THE WEINBERG GROUP INC.

1220 Nineteenth St, NW, Suite 300 Washington, DC 20036 2400 e mail science@ weinberggroup. com WASHINGTON NEW YORK SAN FRANCISCO BRUSSELS PARIS HEALTH RISK EVALUATION OF SELECT METALS IN INORGANIC FERTILIZERS POST APPLICATION Prepared for:

The Fertilizer Institute ( TFI)

January 16, 2000 i DRAFT TABLE OF CONTENTS EXECUTIVE SUMMARY................................................................................................... vi INTRODUCTION................................................................................................................. 1 SECTION 1.0 ¾ DEFINING THE SCOPE OF THIS EVALUATION.............................. 5 Selection of Representative Fertilizer Products ............................................ 5 Selection of Metals of Potential Concern ( MOPC)....................................... 7 Selection of Health Protective Exposure Scenarios ...................................... 9 Summary of Scope ........................................................................................ 14 SECTION 2.0 ¾ DERIVATION OF RISK BASED CONCENTRATIONS ( RBCs)......... 17 Risk Based Concentration ( RBC) Equation .................................................. 17 Acceptable Target Risk ( TR) or Hazard Index ( THI) ................................... 19 Summary Intake Factor ( SIF) Parameters ..................................................... 19 Application Rate ( AR) and Fraction of Nutrient ( FON) ............................... 24 Soil Accumulation Factor ( SACF) ................................................................ 25 Plant Uptake Factors ( PUFs)......................................................................... 28 Toxicity Assessment...................................................................................... 31 SECTION 3.0 ¾ PRESENTATION OF RISK BASED CONCENTRATIONS ( RBCs)

FOR METALS OF POTENTIAL CONCERN ( MOPC).............................. 33 SECTION 4.0 ¾ SCREENING HEALTH EVALUATION: COMPARISON OF THE RISK BASED CONCENTRATIONS ( RBC) WITH THE CONCENTRATION OF THE METAL OF POTENTIAL CONCERN ( MOPC) IN FERTILIZER PRODUCTS ...................................................... 34 Results ........................................................................................................... 35 SECTION 5.0 ¾ DERIVATION OF THE RISK BASED CONCENTRATION ( RBC)

FOR RADIONUCLUDE ( RADIUM226) AND SCREENING LEVEL HEALTH EVALUATION: COMPARISON OF THE RBC WITH PRODUCT DATA........................................................................................ 36 Relative Toxicity........................................................................................... 36 Relative Concentration in Product ................................................................ 36 Evaluation Precedence .................................................................................. 36 Derivation of the Risk Based Concentration ( RBC) ..................................... 37 ii DRAFT SECTION 6.0 ¾ DISCUSSION OF UNCERTAINTY....................................................... 39 Scope of the Evaluation................................................................................. 39 Derivation of the Risk Based Concentration ( RBC) ..................................... 40 Overall Assessment of Uncertainty on the RBC and Health Risk Screening Evaluation..................................................................................... 42 SECTION 7.0 ¾ CONCLUSIONS OF EVALUATION..................................................... 43 SECTION 8.0 ¾ COMPARISON to other EVALUATIONS ............................................. 44 Purpose and General Approach..................................................................... 44 Scope ............................................................................................................. 45 Key Parameters.............................................................................................. 45 Conclusion Regarding Determination of Risk .............................................. 48 REFERENCES .................................................................................................................. 49 GLOSSARY .................................................................................................................. 53 LIST OF APPENDICES Appendix A DEVELOPMENT OF RELATIVE ABSORPTION FACTORS ( RAF) AND DERMAL ABSORPTION FACTORS ( ABS)

Appendix B APPLICATION RATE DATABASE COMPILED FROM USEPA ( 1999) AND CALCULATION OF APPLICATION RATES ( ARs) FOR PHOSPHATE AND ZINC FERTILIZERS Appendix C COLLECTION OF DATA AND SUMMARY STATISTICS FOR PLANT UPTAKE FACTORS ( PUFs) iii DRAFT LIST OF TABLES Table 1 SELECTION OF REPRESENTATIVE FERTILIZER PRODUCTS: CONSIDERATION OF AMOUNT USED IN THE UNITED STATES ( U. S.), APPLICATION RATE, PERCENT NUTRIENT IN PRODUCT, AND MOPC CONCENTRATION Table 2 SELECTION OF METALS OF POTENTIAL CONCERN ( MOPC): CONSIDERATION OF RELATIVE TOXICITY, RELATIVE PRODUCT CONCENTRATION, AND EVALUATION PRECEDENCE Table 3 SELECTION OF REPRESENTATIVE AND HEALTH PROTECTIVE EXPOSURE SCENARIO Table 4 SELECTION OF REPRESENTATIVE AND HEALTH PROTECTIVE CROP GROUPINGS Table 5 VALUES, DESCRIPTIONS, AND REFERENCES FOR BIOLOGICAL EXPOSURE PARAMETERS Table 6 APPLICATION RATES ( ARs) FOR PHOSPHATE FERTILIZERS AND ZINC MICRONUTRIENT FERTILIZERS Table 7 PARAMETERS USED TO CALCULATE SOIL ACCUMULATION FACTORS ( SACFs)

Table 8 SOIL ACCUMULATION FACTORS ( SACFs)

Table 9 PLANT UPTAKE FACTORS ( PUFs) FOR EACH CROP GROUP Table 10 ORAL AND DERMAL TOXICITY VALUES Table 11 SUMMARY OF ALL OF THE PARAMETERS AND ASSUMPTIONS USED TO CALCULATE THE SUMMARY INTAKE FACTORS ( SIFs)

Table 12 SUMMARY INTAKE FACTORS ( SIFs)

Table 13 PARAMETERS ( SACF, AR, PUF, FOL, AND TOXICITY VALUES) USED TO CALCULATE THE RISK BASED CONCENTRATIONS ( RBCs)

Table 14 UNIT RISK BASED CONCENTRATIONS ( RBCs) FOR ALL SCENARIOS Table 15 PERCENT FRACTION OF NUTRIENT ( FON) ESTIMATES FOR PHOSPHATE FERTILIZER PRODUCT CATEGORIES iv DRAFT Table 16 PERCENT FRACTION OF NUTRIENT ( FON) ESTIMATES FOR MICRONUTRIENT FERTILIZER PRODUCT CATEGORIES Table 17 SCREENING LEVEL EVALUATION: COMPARISON OF THE CONCENTRATION OF METAL OF POTENTIAL CONCERN ( MOPC) IN PHOSPHATE FERTILIZERS TO THE ADJUSTED RISK BASED CONCENTRATION ( RBC)

Table 18 SCREENING LEVEL EVALUATION: COMPARISON OF THE CONCENTRATION OF METAL OF POTENTIAL CONCERN ( MOPC) IN MICRONUTRIENT FERTILIZERS TO THE ADJUSTED RISK BASED CONCENTRATION ( RBC)

Table 19 MAJOR ASSUMPTIONS AND UNCERTAINTIES ASSOCIATED WITH THE RISK BASED CONCENTRATIONS ( RBCs) AND THE SCREENING LEVEL HEALTH RISK EVALUATION Table 20 MAGNITUTE OF RELATIVE IMPACT ASSOCIATED WITH EACH PARAMETER IN THE RISK EQUATION Table 21 COMPARISON OF THE PURPOSE, GENERAL APPROACH, AND SCOPE OF THIS EVALUATION TO USEPA ( 1999b) INORGANIC FERTILIZER RISK ASSESSMENT AND CDFA ( 1998) DEVELOPMENT OF RISK BASED CONCENTRATIONS ( RBCs) FOR ARSENIC, CADMIUM, AND LEAD Table 22 COMPARISON OF KEY PARAMETERS USED IN THIS EVALUATION TO THESE PARAMETERS IN USEPA ( 1999b) INORGANIC FERTILIZER RISK ASSESSMENT AND CDFA ( 1998) DEVELOPMENT OF RISK BASED CONCENTRATIONS ( RBCs) FOR ARSENIC, CADMIUM, AND LEAD Table 23 COMPARISON OF PLANT UPTAKE FACTORS ( PUFs) USED IN THIS EVALUATION TO THE PUFs DEVELOPED IN USEPA ( 1999b) INORGANIC FERTILIZER RISK ASSESSMENT AND CDFA ( 1998) DEVELOPMENT OF RISK BASED CONCENTRATIONS ( RBCs) FOR ARSENIC, CADMIUM, AND LEAD Table 24 COMPARISON OF THE METAL OF POTENTIAL CONCERN ( MOPC) CONCENTRATIONS IN PHOSPHATE FERTILIZER PRODUCTS USED IN THIS EVALUATION TO THE MOPC CONCENTRATIONS USED IN USEPA ( 1999b) INORGANIC FERTILIZER RISK ASSESSMENT Table 25 COMPARISON OF THE METAL OF POTENTIAL CONCERN ( MOPC) CONCENTRATIONS IN MICRONUTRIENT FERTILIZER PRODUCTS USED IN THIS EVALUATION TO THE MOPC CONCENTRATIONS USED IN USEPA ( 1999b) INORGANIC FERTILIZER RISK ASSESSMENT v DRAFT LIST OF FIGURES Figure 1 RISK EVALUATION FOR THE LIFE CYCLE OF AN INORGANIC FERTILZER Figure 2 NARROWING THE SCOPE OF THIS SCREENING LEVEL EVALUATION   FOCUSING ON THE FERTILIZERS PRODUCTS, METALS, AND EXPOSURE SCENARIO OF HIGHEST CONCERN Figure 3 POTENTIAL EXPOSURE PATHWAYS OF METALS OF POTENTIAL CONCERN ( MOPC) IN INORGANIC FERTILIZER POST APPLICATION INCLUDES: TRANSPORT PATHWAYS, MEDIA OF POTENTIAL CONCERN, AND ASSOCIATED EXPOSURE ROUTES LIST OF EQUATIONS Equation 1 RBC FOR THE SINGLE CROP FARM Equation 2 RBC FOR THE MULTI CROP FARM Equation 3 ACCUMULATED SOIL CONCENTRATION Equation 4 SOIL ACCUMULATION FACTOR ( SACF)

Equation 5 METAL LOSS DUE TO LEACHING FROM SOIL vi DRAFT EXECUTIVE SUMMARY An evaluation of the potential human health risks from exposure to metals ( primarily nonnutritive elements) found in inorganic fertilizers following their application to agricultural soil is presented in this report. This evaluation comprises one component of a program developed and funded by The Fertilizer Institute ( TFI) that is intended to answer the question: are fertilizers safe? The overall program is viewed in the context of the life cycle of an inorganic fertilizer. Two additional components of the program include: ( 1) an assessment of risks to fertilizer applicators from exposure to metals in products1, and ( 2) a whole product toxicity and occupational exposure evaluation. There are also two other recent reports, one by the United States Environmental Protection Agency ( USEPA) and another by the California Department of Food and Agriculture ( CDFA), that provide information to address the same questions of post application fertilizer safety. Their scopes, methodologies and conclusions are also summarized in this report.

Metals are generally present in inorganic fertilizers as byproducts or contaminants. There are however some metals, for example zinc, iron and copper, that are plant nutrients and are intentionally included in fertilizer formulations. It is acknowledged a priori that exposure to high enough levels of metals ( nutrient or otherwise) could pose a health risk. This evaluation establishes safe limits of metals, referred to as risk based concentrations ( RBCs), in inorganic fertilizers that are applicable under any foreseeable set of local conditions.

The methodology used to develop the RBCs is a back calculation of health risks and is standard for a screening level risk evaluation. This approach provides the basis to screen specific fertilizers, either as groups ( e. g., DAP, phosphate blends, or zinc micronutrients) or individually ( e. g., a 10 30 5 blend or a 50% zinc oxide). There are three basic steps in the screening level evaluation: ( 1) narrow the scope to focus on the highest possible risks; ( 2) derive the health protective RBC values for each metal of concern; and ( 3) compare the RBC value for each metal to the measured concentration of that metal in fertilizer products. If the measured concentrations are below the RBC values, then there are negligible health risks. If the measured concentrations exceed the RBC values, then there may or may not be a health risk, and, a further, more in depth evaluation is warranted.

The first step of the evaluation, narrowing the scope, involves choosing those fertilizer products, metals, and exposure scenarios that are associated with the highest potential health risks. Those that are not directly evaluated are still represented because their associated risks are even less than those that are evaluated directly. Based on the available data, on analyses from existing reports on fertilizer health risks, and consistent with accepted health risk assessment methodology, this evaluation focuses on:

1 Evaluation completed for metals and applicators; it was determined that risks to fertilizer applicators from metals are negligible ( THE WEINBERG GROUP INC. ( TWG). 1999a, Health Risk Based Concentrations for Fertilizer Products and Fertilizer Applicators. And TWG 1999b, Fertilizer Applicator Health Risk Evaluation for Nonnutritive Elements in Inorganic Fertilizers). vii DRAFT · phosphate fertilizers and micronutrient fertilizers; · 12 metals ( referred to as metals of potential concern [ MOPC]) including: arsenic, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium, vanadium, zinc, and one radionuclide, radium 226; · exposure to the farm family ( including adults and children); · ingestion of crops, unintentional ingestion of fertilized soil, and dermal contact with fertilized soil; and · single and multi crop farming scenarios.

The second step of the evaluation, deriving the health protective RBCs for each metal, involves estimating reasonable maximum exposures ( RME) to the metals. The metals are evaluated for non cancer and/ or cancer hazards, as applicable, and the RBCs are established at accepted risk levels ( i. e., a 1x10 5 cancer risk, and a non cancer hazard index of 1.0). In general, USEPA standard approaches, assumptions and default high end exposure values are used in developing the RBCs. Overall, the RBCs for metals are derived to be health protective to ensure that health risks are not underestimated. There are separate RBCs for phosphate fertilizers and for micronutrient fertilizers.

The third and final step of the evaluation involves comparing the RBC for each metal to the maximum measured level of that metal in fertilizer products. Using the maximum metal concentration provides the most health protective determination of a health risk. The concentration data are obtained from the published literature, from a survey of fertilizer manufacturers, and from monitoring programs being conducted by a number of states. The database is compiled by THE WEINBERG GROUP and is updated as new data become available. To date, there are approximately 925 individual phosphate fertilizer samples in 15 categories of products2, and approximately 140 individual micronutrient fertilizer samples in four categories of products. 3 The screening comparison indicates there are no exceedances for any of the phosphate fertilizer RBCs, and therefore, no post application health risks from exposure to metals in NPK types of fertilizers. This same conclusion is reached by USEPA in their recent ( 1999b) fertilizer risk assessment. 4 The CDFA ( 1998) issued its own report of RBCs for arsenic, cadmium and lead in inorganic fertilizers. 5 While the report did not compare RBCs to measured levels in products, the RBCs are very similar to those in this evaluation, and therefore, would support the same conclusion of negligible risk for NPK type fertilizers if a screening comparison were conducted.

2 The phosphate fertilizer categories include: NPK blends, ammonium phosphate sulfate, ammonium polyphosphate, diammonium phosphate ( DAP), monoammonium phosphate ( MAP), nitrophosphate, orthophosphate, phosphate, phosphoric acid, superphosphate, superphosphoric acid, triple superphosphate, urea ammonium phosphate, ureaammonium polyphosphate, and urea diammonium phosphate. 3 The micronutrient fertilizer categories include: boron, iron, manganese and zinc micronutrients ( no mixes). 4 In addition to evaluating health risks, USEPA conducted a screening level ecological risk evaluation of metals in fertilizer runoff into streams, and concludes that no exceedances of water quality criteria are projected. USEPA 1999b, Estimating Risks from Contaminants Contained in Agricultural Fertilizers. 5 CDFA 1998, Development of Risk Based Concentrations for Arsenic, Cadmium, and Lead in Inorganic Commercial Fertilizer. viii DRAFT With regard to micronutrient fertilizers, there are exceedances of arsenic and lead RBCs for several micronutrient fertilizer products. These products contain relatively high levels of arsenic and lead in some samples. The USEPA ( 1999b) reached a similar conclusion indicating that a few micronutrient fertilizer products exceeded the acceptable risk levels for arsenic. Because of the health protective methodology employed in screening level evaluations, and because exceedances occur only at the maximum arsenic and lead concentrations, a firm conclusion regarding health risks from the micronutrient products in question requires a closer evaluation. This refined evaluation would take into account product specific information on crop uses, application rates, fraction of nutrients in the product, and metal concentrations from multiple samples of the same product. This product specific information would replace the default, highend exposure values used in the screening risk evaluation equation.

As with all risk assessments there is some level of uncertainty associated with this evaluation. The major uncertainties are identified and described in the report. The uncertainty is more likely to err on the side of overestimating the potential for risk rather than underestimating the potential risk for both the NPK and micronutrient fertilizer products.

In conclusion, this report, along with the recent USEPA ( 1999b) and CDFA ( 1998) evaluations, provide considerable and definitive information to answer the question: do metals in fertilizers pose a health risk following application? The answer is: these evaluations indicate that metals in inorganic fertilizers do not pose post application harm to human health. It is clear that the risks are negligible for metals in NPK type fertilizers. For the majority of micronutrient fertilizer products for which we have data, the risks are also clearly negligible. A few samples for a few micronutrient products have concentrations of arsenic or lead that exceed the corresponding RBCs. However, no definitive conclusion regarding health risk can be made until these materials are further evaluated in a specific case by case manner. Screening risk evaluations are designed to identify if, and where, additional attention may be warranted. Actual risks may well be overestimated, but they are not underestimated, by the RBC values.

So where do things stand in the life cycle evaluation: are inorganic fertilizers safe? This report and the CDFA ( 1998) report address post application health risks; the recent USEPA ( 1999b) report addresses post application health and environmental risks; and the TWG ( 1999a, b) reports address applicator risks from metals in fertilizers. In total, these evaluations support the conclusion that these fertilizers are safe. The remaining aspect of this life cycle evaluation is an evaluation of whole product toxicity and occupational risks. This evaluation is underway at TFI. It is both prudent and responsible to conduct such an evaluation. However, the fact that there are industry and government standards in place to protect workers and the environment, and given the long history of the fertilizer industry, the answer seems obvious. The information that is being assembled is the proof. 1 DRAFT INTRODUCTION This document presents an evaluation of the potential human health risks from exposure to metals ( primarily non nutritive elements) found in inorganic fertilizers following their application to agricultural soil. This evaluation comprises one component of a program developed and funded by The Fertilizer Institute ( TFI) that is intended to answer the question: are fertilizers safe? The overall program is viewed in the context of the entire life cycle of an inorganic fertilizer, as diagrammed in Figure 1. As seen in Figure 1, this human health risk evaluation focuses on the latter part of the life cycle, that is, post application. 6 Metals are generally present in inorganic fertilizer as byproducts or contaminants. These nonnutritive elements are not purposely present in the fertilizer and are not needed by the plant for growth. Some metals, for example zinc, iron, and copper, are plant nutrients and their presence in fertilizers is essential for plant growth. This human health risk evaluation includes a dozen metals, both non nutritive and nutritive, as well as radioactive elements. 7 In this report, all of the metals under evaluation are referred to as ` metals of potential concern' or MOPC.

The information presented in this document is intended to be easy to use by fertilizer manufacturers, regulators, and the public. There are many fertilizer products, many uses ( varying by local conditions), many metals ( and at varying concentrations), and a number of possible scenarios where a person could be exposed to MOPC following the application of fertilizers to agricultural soils. The intention of this document is to derive safe exposure levels for these metals that would be applicable under any foreseeable set of local conditions, rather than to determine if a given product and local conditions pose an unacceptable health risk. In the language of ` risk assessment', the former is called a back calculation of risk and the latter is called a forward calculation of risk. Both approaches use the same fundamental risk assessment science. The forward calculation allows a determination of whether ` fertilizer product A' used under ` conditions B' poses a health risk. The back calculation allows extrapolation to a much wider set of product and local condition combinations now and in the future. In the back calculation, the results are presented as concentrations of metals that are considered " safe" under reasonable worst case conditions. These concentrations are called ` risk based concentrations' or RBCs. By the nature of their derivation, RBCs are also typically called ` screening level values' and are intended for screening level evaluations. In a screening level evaluation, RBCs are used to determine if a given fertilizer product is safe by comparing the RBC with the metal concentration in the product.

6 The Weinberg Group Inc. ( TWG) prepared two previous reports that evaluate the health risks to applicators of fertilizers for TFI. They are: TWG. 1999a. Health Risk Based Concentrations for Fertilizer Products and Fertilizer Applicators. and TWG. 1999b. Fertilizer Applicator Health Risk Evaluation for Non nutritive Elements in Inorganic Fertilizers: Risk Based Concentrations ( RBCs) Compared to Measured Levels of Non nutritive Elements in Products. These reports concluded there is no significant health risk for fertilizer applicators.

7 Due to the major difference regarding the toxic nature of radionuclides compared to metals, and thus the significant difference in evaluating risk from exposure, radionuclides are evaluated separately. The evaluation of radionuclides can be found in Section 5.0. 2 DRAFT Since RBCs are used primarily for screening level evaluations, they are based on the exposure scenario that reflects the reasonable maximum exposure ( RME), and are intended to be health protective of all other scenarios. In this way, RBCs are derived to ensure that health risks are not underestimated. In general, United States Environmental Protection Agency ( USEPA) standard approaches and values are used in developing the RBCs in this evaluation of metals in fertilizers.

In addition to the development and presentation of RBCs, this report also presents a screening level health risk evaluation where the RBC for each metal is compared to the available database of measured levels of the metals in fertilizer products. Measurements of metal concentrations in fertilizer products conducted in the future could also be compared to the RBCs in order to screen for potential human health risks.

Finally, this evaluation builds upon existing reports and information on potential health risks from exposure to metals in fertilizers to answer the question: are fertilizers safe? Considerable data and analyses have been reported in recent months by the USEPA and by the California Department of Food and Agriculture. 8 This report is organized as follows:

SECTION 1.0   DEFINING THE SCOPE OF THIS EVALUATION. The logic and rationale that was used to define the scope of this evaluation is presented. Specifically, this section identifies the fertilizer product categories that are evaluated, the metals for which RBCs are developed, and the human exposure scenarios and the crop groups that the RBCs are based upon.

SECTION 2.0   DERIVATION OF RISK BASED CONCENTRATIONS ( RBCs). In this section, the RBC equation and the following parameters and factors are described.

SECTION 3.0   PRESENTATION OF THE RISK BASED CONCENTRATIONS ( RBCs) FOR METALS OF POTENTIAL CONCERN ( MOPC). In this section, the screening level RBCs are selected and described for each MOPC.

SECTION 4.0   SCREENING LEVEL HEALTH EVALUATION: COMPARISON OF RBCs WITH CONCENTRATIONS OF MOPC IN FERTILIZER PRODUCTS. In this section, the RBCs for each MOPC are compared to metal concentration data for each of the product categories.

8 The following resources provided critical information in streamlining and focusing the scope of this evaluation:

· California Department of Food and Agriculture ( CDFA) and the Heavy Metal Task Force. 1998. Development of Risk Based Concentrations for Arsenic, Cadmium, and Lead in Inorganic Commercial Fertilizer. Foster Wheeler Environmental Corporation, Sacramento, CA. · United States Environmental Protection Agency ( USEPA). 1999a. Background Report on Fertilizer Use, Contaminants and Regulations. Columbus, OH: Battelle Memorial Institute. · United States Environmental Protection Agency ( USEPA). 1999b. Estimating Risk from Contaminants Contained in Agricultural Fertilizers. Draft. Washington, D. C.: Office of Solid Waste and Center for Environmental Analysis. 3 DRAFT SECTION 5.0   DERIVATION OF THE RISK BASED CONCENTRATION FOR RADIONUCLUDE ( RADIUM226) AND SCREENING LEVEL HEALTH EVALUATION: COMPARISON OF THE RADIUM226 RBC WITH PRODUCT DATA. In this section, a RBC for radium 226 is derived and the RBC is compared to radium226 product data.

SECTION 6.0   DISCUSSION OF UNCERTAINTY. In this section, uncertainties related to the scope of this health risk evaluation and the derivation of RBCs are presented.

SECTION 7.0   CONCLUSIONS OF EVALUATION. In this section, conclusions are drawn from the screening level health risk evaluation for NPK and micronutrient fertilizers.

SECTION 8.0   COMPARISON TO OTHER EVALUATIONS. In this section, the outcome of this evaluation is compared to other health risk evaluations for fertilizers, including USEPA ( 1999b) and CDFA ( 1998). FIGURES manufacture transport blending storage focus on products and application ( a)

occupational risks ( b) environment this evaluation focus on metals and crop ingestion / soil contact risks ( a) Occupational exposure to metals during application was determined to be safe in previous evaluation ( TWG 1999a, b).

( b) Whole product toxicity and occupational exposure are being evaluated in another program.

FIGURE 1. RISK EVALUATION FOR THE LIFE CYCLE OF INORGANIC FERTILIZERS DRAFT 5 DRAFT SECTION 1.0 ¾ DEFINING THE SCOPE OF THIS EVALUATION Consistent with a screening level risk evaluation9, the scope of this evaluation is narrowed to focus on the fertilizer product categories, metals, and exposure scenarios that have the highest potential for health risks. 10 Developing RBCs that are based on " high end" exposures results in RBCs that are protective of other less risky scenarios and results in health risks that are not underestimated. Figure 2 entitled ` Narrowing the Scope of the Evaluation  Focusing on the Fertilizer Products, Elements, and Exposure Scenario of Highest Concern' presents a summary of how each of these key components was narrowed. In addition, the narrowing of each of these components is discussed in the following sections.

Selection of Representative Fertilizer Products As stated previously, the purpose of this assessment is to evaluate potential health risks from metals in inorganic fertilizers following their application to agricultural soils. The fertilizer products that result in the greatest addition of metals to soil are the products of highest concern. The magnitude of MOPC addition to soil is dependent on several factors including ( 1) the composition of the fertilizer, ( 2) the concentration of the metal in the fertilizer, and ( 3) the amount of fertilizer that is applied. By evaluating the health risks from those products whose use results in the greatest addition of metals to soil, the wide array of inorganic fertilizers is covered as well. That is, ` all' fertilizers can be evaluated by screening for health risks based on those products posing the highest potential risks. Therefore, a critical component of this evaluation is the characterization of inorganic fertilizer products and the selection of the products that will be representative of all other inorganic fertilizer products.

Table 1 presents a summary of each of the factors determining the magnitude of metal addition to soil and identifies the representative products that are selected for health risk evaluation. 11 Each of the factors is also discussed below.

Types of Inorganic Fertilizers and Use There are three general categories of inorganic fertilizers: macronutrient ( or primary) fertilizers, secondary fertilizers, and micronutrient fertilizers. Each of the general categories of inorganic fertilizers supplies plants with different nutrients. Macronutrient fertilizers supply primary nutrients, which include nitrogen ( N), available phosphate ( P), and soluble potash or potassium ( K). There are products that supply each of the nutrients separately, as well as blends; for example NPK. Also, there are numerous phosphate fertilizers, such as, diammonium phosphate ( DAP), triple super phosphate ( TSP), and monoammonium phosphate ( MAP). There are also many different types of macronutrient nitrogen fertilizer products ( e. g., ammonium nitrate,

9 Narrowing the scope of a screening level evaluation to focus on the scenario that is health protective and representative of all other scenarios is standard USEPA practice [ as indicated in USEPA guidance ( 1995), and used to assess health and environmental risks from fertilizers in USEPA ( 1999b) and CDFA ( 1998)]. 10 Based on a screening level ecological risk evaluation of metals in fertilizer runoff into streams, USEPA ( 1999b) concluded that no exceedances of water quality criteria are projected. 11 Information used in this section was obtained primarily from USEPA ( 1999a) and TWG ( 1999b). 6 DRAFT ammonium polysulfide, sodium nitrate, and urea). Macronutrient fertilizers are used the most in the US, accounting for 91% of the total inorganic fertilizer; specifically, 38%, 12%, 10%, and 31% of N, P, K, and NPK are used, respectively ( USEPA 1999a).

Secondary fertilizers supply secondary nutrients to plants including calcium, magnesium, and sulfur. Examples of secondary fertilizer products include calcium chloride, calcium chelate, and magnesium chelate. Secondary and micronutrient fertilizers ( discussed below) account for only 4.5% of the total inorganic fertilizer use in US agriculture ( USEPA 1999a).

Micronutrient fertilizers supply plants with boron, chlorine, cobalt, copper, iron, manganese, molybdenum, sodium, and/ or zinc. For example, zinc micronutrient fertilizers supply zinc, iron micronutrient fertilizers supply iron, and mixes supply one or more of the micronutrients. Examples of micronutrient products include manganese oxide, cobalt sulfate, and zinc sulfate. Among the various micronutrient fertilizers ( e. g., boron, iron, manganese, and zinc), zinc is used the most throughout the US ( Hignett and McClellan 1985).

Product Composition / Percent Nutrient In addition to the nutrient composition ( i. e., N, P, K and secondary and micronutrient described above), the percent of each nutrient ( e. g., P2O5 or zinc) in a product varies. For example, as can be seen in Table 1, percent nutrient of P2O5 ranges from 2 70% ( USEPA 1999a).

Application Rates The application rate ( AR) of any given fertilizer can vary depending on the nutrient needs of the plant and the local soil conditions. The AR is also influenced by the composition of the product and the percent nutrient content. The lower the percentage of nutrient in a product, the higher the AR required to meet the plant's nutrient needs. The ARs presented in Table 1 are high end estimates ( 95th percentile) and are based on the nutrient needs of high acreage US crops ( USEPA 1999a). As can be seen in Table 1, nitrogen ( N) has the highest AR of each of the primary nutrients and phosphate ( P) has the second highest AR. The ARs for secondary and micronutrients are generally much lower than the ARs for the primary nutrients.

Concentration of Metal in Products Metals occur in fertilizers because of the sources of the nutrients. As a category, phosphate fertilizers have the highest levels of metals among the primary and secondary nutrients, thus, the " high" relative concentration rating. Nitrogen fertilizers ( and NPK applied for N) have lower concentrations of MOPC compared to phosphate fertilizers ( and NPK applied for P) and potash fertilizers generally have much lower concentrations of MOPC than nitrogen fertilizers ( USEPA 1999a, b). Phosphorous is mined from phosphorous rock, and phosphorous ores naturally contain metals. 12 Depending upon their source of nutrients, micronutrient fertilizers can also have relatively high levels of metals. As presented in Table 1, iron and zinc micronutrients have 12 As reported in Raven and Loeppert ( 1997), Potash & Phosphate Institute ( PPI) ( 1998), CDFA ( 1998), TWG ( 1999c), and USEPA ( 1999a). 7 DRAFT the highest relative concentrations of MOPC ( especially when considering arsenic in iron micronutrients) ( USEPA 1999a, b). Micronutrient mixes can also have relatively high concentrations of select MOPC. Since the metals exist in the nutrient part of the fertilizer, the percent nutrient of the product has a direct bearing on the concentration of metal in the final product. Table 1 lists ` concentration relative ratings' for the metals evaluated in this assessment. The actual measured concentrations of metals in numerous products have been compiled in a database from industry, state and literature sources ( TWG 1999c).

Representative Fertilizer Products Considering all of the factors discussed above and the information presented in Table 1, phosphate fertilizers are selected to represent the macronutrient ( primary and secondary) fertilizers in developing the health protective RBCs and comparing them to measured levels in products. The application of phosphate fertilizers is expected to result in the greatest addition of metals to soil, and therefore, the highest potential for exposure among the macronutrient fertilizers. 13 The RBCs are developed for a generic phosphate fertilizer but are then modified to account for different percent nutrient content in specific phosphate fertilizers ( e. g., DAP, TSP) or phosphate blends ( e. g., NPK of various percent nutrient combinations). 14 Zinc, manganese, iron, and boron micronutrient fertilizers are selected to represent micronutrient fertilizers. Micronutrient mixes are not specifically evaluated, however, the evaluation of the other micronutrients will be health protective of potential risk from the application of micronutrient mixes because the concentrations of MOPC in micronutrient mixes is represented by the other micronutrient fertilizers. While the ARs can vary among micronutrient products, the initial screening RBCs are based on the AR for zinc products. The ARs for different micronutrient fertilizers are similar. In the health risk evaluation, the RBCs are modified to account for the different percent nutrient content in specific micronutrient fertilizers.

Other commercial fertilizer products, for example, nitrogen only, potassium only, secondary nutrient fertilizers, and the remaining micronutrient fertilizers and mixes are not specifically evaluated because the evaluation of phosphate fertilizers, and select micronutrients ( as discussed above) is considered health protective of these fertilizers.

Selection of Metals of Potential Concern ( MOPC)

As can be seen in Table 2, this health risk assessment begins with a list of 23 metals that are potentially found in inorganic fertilizers. 15 For similar reasons that the products of highest potential concern are selected for a screening risk evaluation, the metals selected for this assessment are also narrowed. These metals are called MOPC. MOPC selected for evaluation 13 The selection of phosphate fertilizers for this evaluation is further supported by estimates of MOPC loading in soil from macronutrient fertilizer application in both the USEPA ( 1999a) and CDFA ( 1998) risk assessments. 14 This evaluation focuses on granular fertilizers. Liquid fertilizers are not considered separately in this evaluation because liquid fertilizers are generally applied at a much lower rate then granular fertilizers. Therefore, the evaluation of granular fertilizers will be health protective of liquid fertilizers ( USEPA 1999a). 15 While not exhaustive, this list is considered comprehensive. It was developed from a search of industry and published literature records ( TWG 1999c). Three radionuclides ( radium, thorium and uranium) were also considered in the starting list. 8 DRAFT are intended to be representative and health protective of all the metals in inorganic fertilizer products. The factors that are considered in selecting the MOPC include ( 1) their relative toxicity, ( 2) their relative concentration in products, and ( 3) whether there is an evaluation precedence ( e. g., a regulation or high priority) for human health concerns. Both toxicity and concentration in products are considered because they are determinants that relate directly to risk. All three factors are detailed in Table 2, along with the list of MOPC that are selected.

Relative Toxicity Relative toxicity is determined by comparing the oral reference dose ( RfD) for each metal as established by USEPA and presented in USEPA's Integrated Risk Information System ( IRIS). 16 The oral RfD is particularly relevant in this evaluation because oral exposure is expected to contribute the greatest potential for health risk from metals in agricultural soil.

Relative Product Concentration The data describing the concentration of metals in products comes from an industry and published literature survey conducted for TFI ( TWG 1999c) and from the USEPA publication on fertilizers ( USEPA 1999a). The MOPC concentration in the fertilizer products is rated by a qualitative evaluation of MOPC concentrations in each of the phosphate fertilizer and micronutrient fertilizer product categories relative to each other. The concentration for each MOPC is compared across product categories and rated accordingly. Products with obviously high MOPC concentrations are rated high; product categories with generally low MOPC concentrations are rated low. The relative MOPC concentrations are low ( phosphate fertilizer < 10 ppm, micronutrient fertilizer < 50ppm); medium ( phosphate fertilizer, 10 ppm   100 ppm, micronutrient fertilizer, 50 ppm   1,000 ppm); and high ( phosphate fertilizer > 100 ppm, micronutrient fertilizer > 1,000 ppm). Again, these qualitative ratings are based on a review of the product concentration database ( TWG 1999c.)

Evaluation Precedence As seen in Table 2, most of the 23 metals on the starting list, and all of the MOPC selected for this health risk evaluation, have been identified and/ or evaluated in previous, relevant, reports. 17 Evaluation precedence is considered an important aspect in the final selection of MOPC, even when the metal was not highly toxic or was not found at particularly high concentrations in fertilizer products.

16 There is a detailed discussion of these values in the section of this report entitled ` Toxicity Assessment'. 17 The following reports ( or standards) have established evaluation precedence for the MOPC: · California based RBCs for arsenic, cadmium, and lead are developed in CDFA ( 1998). · Risks from arsenic, cadmium, chromium, copper, lead, mercury, nickel, vanadium and zinc contained in agricultural fertilizers was estimated in USEPA ( 1999b). · Canada has established metal limits in fertilizers for arsenic, cadmium, cobalt, mercury, molybdenum, nickel, lead, selenium, and zinc as reported in the Canadian Fertilizers Act R. S., c. F 9s. l. ( 1003). · Pollutant limits for arsenic, cadmium, chromium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc in biosolids applied to agricultural soils were developed by USEPA ( 1995). 9 DRAFT Metals of Potential Concern ( MOPC) Selected for Evaluation The following 12 metals are selected as MOPC. Note, the elemental symbol for each metal is presented in parenthesis next to each MOPC, however, for ease in reading this document, the full name is used throughout this document. In addition, one radionuclide ( discussed in Section 5.0) is selected for evaluation.

Arsenic ( As) Copper ( Cu) Nickel ( Ni) Radium 226 ( Ra) Cadmium ( Cd) Lead ( Pb) Selenium ( Se) Chromium ( Cr) Mercury ( Hg) Vanadium ( V) Cobalt ( Co) Molybdenum ( Mo) Zinc ( Zn)

Selection of Health Protective Exposure Scenarios In a similar manner to that used to focus on which fertilizer products and MOPC to include in the screening risk evaluation, the exposure scenario that would be representative and health protective of all potential exposure scenarios is identified. All of the possible exposure pathways, as well as exposure routes for potentially exposed populations, that occur postapplication are considered. The exposure scenario with the greatest exposure and risk potential is then identified.

Potential Exposure Pathways The first step in selecting the exposure scenario with the highest potential risk is to determine all of the possible exposure pathways for the MOPC in fertilizer, following application. A complete exposure pathway has a transport pathway, a potential exposure media, and a likely exposure route ( mode of contact with the receptor). All of the potential exposure pathways are presented in Figure 3. Each of these exposure pathways and associated exposure routes is discussed below.

1. The first pathway is runoff of the metals into surface water, followed by incidental ingestion and dermal contact by humans, as well as, uptake into fish followed by ingestion of fish by humans. This exposure pathway and routes are eliminated as a major exposure pathway because ( a) they are not expected to contribute significantly to risk ( based on USEPA's previous assessment of fertilizers ( 1999b) and biosolids ( 1995)) and ( b) the only MOPC that is expected to bioaccumulate in fish is a form of mercury, methyl mercury. 18 The other MOPC are not expected to bioaccumulate.

2. Leaching into groundwater followed by ingestion in drinking water is eliminated as a major exposure pathway based on the elimination of this pathway in USEPA ( 1999b, 1995) and CDFA ( 1998). Exposure from drinking water is much less than from crop consumption.

18 In soil, mercury is reactive and may form several different complexes. Although the transport of mercury into a nearby water body, some formation of methyl mercury, and uptake into fish may occur, it is expected that this pathway will occur less frequently, and result in less exposure than the complexing of mercury with chlorine in soil ( especially since chlorine ions may be the most persistent and available complexing agent for mercury in soil) ( McLaughlin et al. 1996). 10 DRAFT 3. Volatilization of metals into air followed by inhalation, and wind blown dispersion of airborne metals followed by inhalation, are eliminated as major exposure pathways based on USEPA ( 1999b) and CDFA ( 1998) as well as TWG's applicator risk assessment ( 1999a, b). Specifically, this exposure pathway is eliminated because MOPC are not expected to volatilize and the inhalation of particulates was found to contribute minimally to risk in these previous evaluations. Other exposure routes that are selected for inclusion in the RBC equation ( e. g., unintentional ingestion of fertilized soil or ingestion crops) are the primary contributors to risk.

4. The ingestion of MOPC in fertilized soil and in crops by foraging cattle, followed by the subsequent ingestion of animals products ( beef and milk) by humans, is eliminated as a major exposure pathway. 19 Instead, the direct exposure pathways ( i. e., unintentional ingestion of soil and dermal contact with soil, and ingestion of crops) are considered to provide a much higher level of exposure, especially because the MOPC do not bioaccumulate in the terrestrial food chain ( i. e., cattle).

5. Direct contact with soil ( i. e., unintentional ingestion of fertilizers in soil and dermal contact with fertilizers in soil) and uptake of metals in the soil by plants ( crops) followed by ingestion are considered the most likely and most substantial exposure pathways and therefore are the basis of the RBCs. The selection of these exposure pathways is based on information presented in USEPA ( 1999b and 1995), CDFA ( 1998) and TWG ( 1999a, b).

Potential Populations and Exposure Routes The next step in defining the exposure scenario is to identify all of the potentially exposed populations and their associated exposure routes. This step is presented in Table 3. Note, exposure pathways and routes eliminated in the previous step are not included in this table. There are four potential populations considered for evaluation including a home gardener, the general public, a farm worker, and a resident farmer.

Representative and Health Protective Exposure Scenario Compared to the other populations, the resident farmer has many more potential exposure routes and greater potential for exposure. The home gardener is not selected because of the lower exposure potential and low use of fertilizers compared to the farmer. The general public is not selected because of the low relative exposure potential from the ingestion of soil compared to the resident farmer. The farm worker has been evaluated in previous reports ( TWG 1999a, b) and found not to be at risk from metals as a result of applying fertilizers. Clearly, the resident farmer ( and family including children) is the population with the highest exposure potential and is selected as the population that the RBCs will be based upon. 20 19 These exposure routes are eliminated in CDFA ( 1998) screening phase of the assessment because they contribute much less to risk than ingestion of crops. 20 The selection of the resident farmer as the representative and health protective population is supported by the use of this population in developing RBCs in CDFA ( 1998) and the use of this population to estimate risk from exposure to agricultural fertilizers in USEPA ( 1999b). 11 DRAFT In most risk evaluations there are populations that may be considered " sensitive or high end" populations. These populations are at potentially higher risk from exposure compared to other populations either because the population is particularly sensitive to the toxic effect of the MOPC ( e. g., children are especially sensitive to lead exposure) or because the population is considered sensitive ( e. g., lactating mother or elderly). In this evaluation, children are evaluated. Elderly are not specifically evaluated because the adult farm resident scenario is considered health protective of an elder. The exposure routes and associated exposure parameters used to evaluate the adult farmer resident, represent greater exposure than an elder would encounter. The lactating mother is not evaluated because metals are not typically fat soluble, and therefore, are not expected to be at elevated concentrations in mother's milk. In addition, as discussed in the toxicity assessment, toxicity values have uncertainty factors built into them for different reasons, one of which is to protect for sensitive subpopulations.

Selection of Representative Crop Groups As indicated above, the ingestion of crops is a significant route of exposure. The magnitude of exposure from this route varies depending on the type of crop( s) evaluated. Crops vary in how they grow ( e. g., above or below ground, depth of root system), how much nutrient they need to grow ( e. g., higher or lower phosphate requirement), and their ability to take up metals into edible portions of the plant. For the purposes of this assessment, crops are therefore grouped by type, and these crop groups are treated separately in the equation used to derive the RBC values for each MOPC.

In this evaluation, crops are grouped considering basic physiology (" like" crops were grouped together) as well as crop grouping and evaluation in other relevant reports. 21 The crop groups that are considered include: unexposed vegetables ( root crops), exposed vegetables, grains, fruit, forage crops, and field crops. Each of these groups is further clarified and classified below:

· Vegetable crops are also called exposed crops or unprotected crops. Vegetable crop is a large, broad category of many different kinds of crops. Examples of different types of vegetables are leafy vegetables ( e. g., endive, kale, lettuce, spinach, swiss chard, and water cress), head and stalk vegetables ( e. g., artichokes, asparagus, broccoli, brussel sprouts, cabbage, cauliflower, celery, and peppers), and legumes ( e. g., beans and peas). Several crops included in this group are technically fruits, but are cultivated as vegetables ( i. e., cucumber, eggplant, and tomato). All of the above vegetables are considered in the vegetable crop group.

· Unexposed vegetables are also called protected vegetables, root crops, herbage, tubers, or bulbs. This report will refer to this group as root crops. Root crops have unique growing characteristics and are considered to have " like" physiologies; thus, they are evaluated together. Crops in this category include beets, carrots, fennel, mangel, onion, parsnip, potatoes, radish, rutabaga, and turnip.

21 CDFA ( 1998) evaluated six crop groups: vegetable, root, grain, tree, vine, and forage crops. USEPA ( 1999b) evaluated five crop groups: grains, forage, fruit, herbage, and roots. Grain and forage were evaluated through ingestion of these crops by cattle and subsequent human ingestion of animal products. 12 DRAFT · Grains are also a large, general crop group. Grains can be designated as field grains, silo grains, forage grains, or small or large grains. The grains included in this group are all grains consumed by humans. Grains consumed by cattle ( forage or silo grains) are not included in this evaluation because, as discussed, ingestion of animal products is not evaluated. Grains in this group include corn, barley, millet, oat, rice, rye, and wheat.

· Fruit crops can be grown on trees ( i. e., tree fruits, such as, limes, lemons, and oranges) or as sweet fruits. Examples, of sweet fruits include cantaloupe, apple, rhubarb, strawberry, fig, grapes, kiwi, and pear. Vine crops ( such as, grapes) are also fruits. The ingestion of fruit crops is not included in this evaluated because they are not expected to contribute significantly to exposure. 14 Nuts are also tree crops, but are not considered in this evaluation because of low exposure potential. 14 · Field crop is a general term for crops grown on fields. Examples of field crops include corn, cotton, potatoes, soybeans, tobacco, or wheat ( USEPA 1999a). Field crops that are ingested by humans are evaluated in the appropriate crop groupings ( grain, root, or vegetable group).

· Forage crops are crops that are grown solely for the purpose of feeding cattle. Again, the ingestion of animal products by humans was eliminated from this evaluation. Therefore, forage crops are not considered further. 14 For consistency, these crop groupings are retained throughout the different components of this evaluation ( e. g., development of plant uptake factors, application rates, and ingestion rates) given available data. Crop groups expected to contribute significantly to exposure are selected for inclusion in the evaluation. 22 These are vegetable, root and grain crops. Crop groups and the rationale for inclusion are presented in Table 4.

Farms and their use of fertilizers vary by size, geography ( including soil and climate conditions), preferred crop types, etc. USEPA ( 1999a) recent report on the use of fertilizers includes an overview of fertilizer consumption and the amount of crops produced in different regions of the country. For example, the following table indicates where the use of different fertilizer types is heaviest, and those states with the highest crop acreage ( by crop).

22 CDFA ( 1998) eliminated tree ( fruit and nut) crops, vine crops ( grapes), and forage crops from the development of RBCs in the screening phase of their assessment because their associated exposure to arsenic, cadmium, and lead and subsequent risk, were determined to be considerably less than for the other crop groupings. 13 DRAFT FERTILIZER REGION STATES Phosphate West North Central East North Central Illinois Indiana Multiple Nutrient South Atlantic West North Atlantic Florida Texas Secondary Nutrient Pacific South Atlantic California North Carolina CROP STATES SPECIFIC CROPS California Asparagus, bell pepper, broccoli, cabbage, cauliflower, celery, lettuce, tomatoes Florida Bell peppers, legumes, snap peas, sweet corn ( fresh) Georgia Snap peas Vegetable Michigan Cucumbers ( fresh) California Carrots, onion Idaho Potato Maine Potato New York Onion Oregon Onion Root Texas Potato, onion Illinois Corn ( for grain), wheat Indiana Corn Montana Corn Grain Nebraska Corn California Apples, citrus fruits Fruit Florida Citrus fruits It is also recognized that a farm may grow one crop or it may grow several different kinds of crops ( i. e., multi crop farming). The exposure scenario for a single crop farm could be quite different from the exposure scenario for a multi crop farm. For example, on a single crop farm the application rate would be the same for every parcel of the farm, because only one crop is grown, and the application rate is dependent on the crop type. Whereas, on a multi crop farm the application rate and crop acreage is proportioned into different crop groups ( i. e., grain, 50%, vegetable, 40%, and root, 10%). Another parameter that is used to quantify exposure, and that is crop specific, is the plant uptake factor. Therefore, RBCs for both a single crop ( one for each crop group) and a multi crop ( combines all 3 crop groups) are developed. The lowest of these four RBCs is used for the screening level health risk evaluation. 14 DRAFT Summary of Scope The scope of this evaluation is focused in order to provide a health protective screening evaluation of risks associated with post application exposure to metals in inorganic fertilizers. Those fertilizer types, metals, receptors, and exposure routes that are associated with the highest potential health risks are identified for direct evaluation. Those that are not directly evaluated are represented because their associated risks are even less than those that are evaluated directly. Based on the available data and on analyses from existing reports, and consistent with accepted health risk assessment methodology, this evaluation focuses on:

· phosphate fertilizers and micronutrient fertilizers; · 12 metals including: arsenic, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium, vanadium, zinc, and one radionuclide, radium 226; · exposure to the farm family ( including children); · ingestion of crops, unintentional ingestion of fertilized soil, and dermal contact with fertilized soil; and · single and multi crop farming scenarios TABLES TABLE 1 SELECTION OF REPRESENTATIVE FERTILIZER PRODUCTS: CONSIDERATION OF USE IN THE U. S., APPLICATION RATE, PERCENT NUTRIENT IN PRODUCT, AND RELATIVE METAL OF POTENTIAL CONCERN ( MOPC) CONCENTRATION Use in US in 1996 High End Range of Rating of General Inorganic rounded to the ( 95th percentile) Percent Relative Selected for Evaluation?

Fertilizer Category nearest million ton Application Rate Nutrient in MOPC Yes ( Y) or ( purpose) Nutrient ( percent of total) ( a) ( lb/ acre year) ( b) Product ( a) Concentration ( c) No ( N) Rationale Macronutrient N 23 ( 38) 206 ( d) 6.3  82 Medium N Evaluation of NPK P and P will be health protective of NPK N and N ( supply primary because of the low relative MOPC concentration.

nutrient) P 7 ( 12) 173 ( e) 2.0  70.1 High Y Primarily because of the relative high MOPC concentration. Also due to the application rate and amount used in the US.

K 6 ( 10) 177 ( f) 9.8  62.1 Low N Low relative MOPC concentration.

NPK for N 19 ( 31) 206 3 46 Medium N Evaluation of NPK P and P will be health protective of NPK N and N because of the low relative MOPC concentrations.

NPK for P 173 11.5  27.4 High Y Primarily because of the relative high MOPC concentration.

Also due to the application rate and amount used in the US.

Secondary ( g) Sulfur 3 ( 4.5) 40 14  100 N Low use and low relative MOPC concentration.

( supply secondary Calcium 4,000 NA Low ( i) N Low use and low relative MOPC concentration.

nutrient) Magnesium 100 NA N Low use and low relative MOPC concentration.

Micronutrients ( h) Boron 3 10  21 Medium/ Low ( i) Y High relative arsenic concentration.

( supply micronutrient) Iron 20 12  15 High ( i) Y High relative arsenic and cadmium concentration.

Manganese 10 24.7  29.5 Medium/ Low ( i) Y High relative arsenic concentration.

Zinc 10 7  58 High ( i) Y High relative MOPC concentration.

Mixes 30 NA High/ Medium ( i) ( j) N Appropriate information is not available.

Notes: Bold = Selected as the representative and health protective product, therefore, evaluated in this assessment.

MOPC = Metal of Potential Concern N = Nitrogen. Examples of nitrogen fertilizers include: ammonium nitrate, ammonium sulfate, ammonium sulfate nitrate urea, calcium ammonium nitrate, calcium cyanamide, calcium nitrate,

calcium nitrate urea, ferrous ammonium sulfate, magnesium nitrate, nitric acid, sodium nitrate, urea, urea formaldehyde, zinc manganese ammonium sulfate.

P = Available Phosphate or Phosphorous Oxide ( or P2O5). P is not a fertilizer, but is a building block of other fertilizers ( many of which are NPKs). Examples of " phosphate" fertilizers include:

ammonium metaphosphate, ammonium phosphate, ammonium phosphate nitrate, ammonium phosphate sulfate, ammonium polyphosphate, basic lime phosphate, basic slag,

calcium metaphosphate, diammonium phosphate ( DAP), magnesium phosphate, monoammonium phosphate ( MAP), nitric phosphate, phosphate rock, phosphoric acid,

superphosphate ( SP), and triple SP ( TSP).

K = Potassium or Soluble Potash ( or K2O). Examples of potash fertilizers include: lime potash mixtures, manure salts, muriate potash, potassium carbonate, potassium nitrate, potassium sulfate,

potassium magnesium sulfate, potassium metaphosphate, and potassium sodium nitrate.

NPK = Nitrogen, Phosphate, Potash blend. Generally called macronutrient agricultural blends. Some phosphate fertilizers are also NPs ( e. g., DAP, TSP) or NPKs.

NA = Not Applicable TWG = The Weinberg Group Inc.

( a) Based on information presented in USEPA ( 1999a). Note, total percent does not add up to 100% because liming agents ( 3.6%) are not included.

( b) Based on application to field crops that are planted the most ( highest planting acreage) in the US ( USEPA 1999a).

( c) Qualitative rating of relative MOPC concentrations among products. MOPC considered include arsenic, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium,

vanadium, and zinc. Based on TWG fertilizer database [( TWG 1999c) compilation of survey, literature, industry and state data], and information presented in USEPA ( 1999a),

CDFA ( 1998), and USEPA ( 1999b).

( d) Based on application to broccoli ( USEPA 1999a).

( e) Based on application to potato ( USEPA 1999a).

( f) Based on application to oranges ( USEPA 1999a).

( g) Examples of secondary nutrient products include: aluminum sulfate, calcium chelate, calcium chloride, Epsom salt, and gypsum.

( h) Examples of micronutrient products include: borax, copper chelate, magnesia, manganese oxide, ferric oxide, non chelate, zinc oxide, and zinc sulfate.

( i) Concentration of MOPC in the product varies by MOPC; these ratings are based on the general trends observed. Considering all MOPCs, zinc micronutrients have the highest relative MOPC concentrations. In addition, zinc micronutrient fertilizers have the most data available. However, some MOPCs are at higher concentrations ( e. g., arsenic and cadmium)

in micronutrient fertilizers other than zinc ( e. g., iron).

( j) Mixes are not included in the screening evaluation, because the necessary information ( percent micronutrient) is not available. DRAFT Relative Ratings for Determinants of Potential Health Risk MOPC Concentration ( b)

Aluminum N Not expected to pose a health risk Antimony N Not expected to pose a health risk Arsenic CAL, C, E, S Y Relative Toxicity Barium N Not expected to pose a health risk Beryllium N Not expected to pose a health risk Bismuth NA N Not expected to pose a health risk Boron N Not expected to pose a health risk Cadmium CAL, C, E, S Y Potential for Exposure ( g)

Chromium III ( f) E, S Y Evaluation Precedence Cobalt C, S Y Evaluation Precedence Copper E, S Y Evaluation Precedence Iron S N Not expected to pose a health risk Lead CAL, C, E, S Y Relative Toxicity Manganese N Not expected to pose a health risk Mercury CAL, C, E, S Y Relative Toxicity Molybdenum C, S Y Evaluation Precedence Nickel C, E, S Y Evaluation Precedence Selenium C, S Y Evaluation Precedence Silver N Not expected to pose a health risk Strontium N Not expected to pose a health risk Titanium N Not expected to pose a health risk Vanadium E Y Evaluation Precedence Zinc C, E, S Y Evaluation Precedence Notes: Bold = Selected for evaluation.

Italics = Micronutrients ( i. e., essential to plant growth)

= Relative High Toxicity = Relative High Concentration = Relative Medium Toxicity = Relative Medium Concentration = Relative Low Toxicity = Relative Low Concentration NA = Not Available C = Canadian Standard. Canadian Fertilizers Act R. S., c. F 9s. 1.( 1003).

CAL = California Department of Food and Agriculture ( CDFA) and the Heavy Metal Task Force. 1998. Development of Risk Based Concentrations for Arsenic, Cadmium, and Lead in Inorganic Commercial Fertilizers. Foster Wheeler Environmental Corporation, Sacramento, CA.

E = United States Environmental Protection Agency ( USEPA). 1999b. Estimating Risks from Contaminants Contained in Agricultural Fertilizers. Draft. Washington, D. C.:

Office of Solid Waste and Center for Environmental Analysis.

S = United States Environmental Protection Agency ( USEPA). 1995. A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule . Washington, D. C.:

Office of Wastewater Management. EPA 832 B 93 005.

( a) Toxicity rating is based on the oral reference dose ( RfD), because, the oral route of exposure is expected to be the exposure route of most concern ( i. e., incidental ingestion of soil and ingestion of crops), and because all of the MOPC have an oral RfD.

( b) MOPC concentration rating is based on a qualitative evaluation of the MOPC concentrations in products relative to each other.

( c) Phosphate fertilizers includes ( but are not limited to) N P K blends, DAP, MAP, TSP, and SP.

( d) Micronutrient fertilizers include: boron, iron, manganese, and zinc.

( e) Evaluation precedence identifies existing, relevant, studies that have evaluated the MOPC.

( f) Based on the assumption that chromium III ( not chromium VI) is the species that is available.

( g) Cadmium is selected for evaluation because it is easily taken up into plants and, therefore, has a high exposure potential. Relative toxicity and concentration also contributed to this selection. Primary Reason Metal of Potential Concern ( MOPC) Yes ( Y) or No ( N)

TABLE 2 SELECTION OF METALS OF POTENTIAL CONCERN ( MOPC): CONSIDERATION OF RELATIVE TOXICITY, RELATIVE PRODUCT CONCENTRATION, AND EVALUATION PRECEDENCE Selected for Evaluation ?

Toxicity ( a) Phosphate Fertilizer ( c) Micronutrient Fertilizer ( d) Evaluation Precedence ( e) DRAFT TABLE 3 SELECTION OF REPRESENTATIVE AND HEALTH PROTECTIVE EXPOSURE SCENARIO Potential Exposure Routes Selected for Evaluation?

Soil Incidental Dermal Ingestion of Yes ( Y) or Potential Populations Ingestion Contact Crops No ( N) Rationale Home Gardner Y Y Y N Lower exposure potential than resident farmer. ( a)

Public Consumer N N Y N Lower exposure potential than other scenarios. ( a)

Lower exposure potential than a resident farmer and evaluated in Farm Worker ( b) Y Y N N previous evaluation. ( c)

Highest exposure potential; representative and health Resident Farmer ( d) ( e) Y Y Y Y protective of other scenarios.

Notes: Bold = Selected as the representative and health protective exposure scenario.

RBC = Risk Based Concentration Y = Yes, a plausible exposure route and expected to contribute significantly to exposure.

N = No, not a plausible exposure route.

( a) Each of these populations has lower exposure potential compared to the farm resident because exposure to fertilized soil either ( 1) does not occur or ( 2) occurs less frequently.

( b) Exposure to an applicator, including a farm worker, was evaluated in TWG ( 1999a, b). No significant health risk was found for this exposure scenario.

( c) A farm worker has a much lower exposure potential than a farm resident because the ingestion of crops is not applicable ( or considered) for this population.

( d) Resident farmer considers both an adult and child who lives on a farm.

( e) CDFA ( 1998) focused on this population in developing RBCs for arsenic, cadmium, and lead; USEPA ( 1999b) also focused on this population in evaluating risks from contaminants contained in agricultural fertilizers. DRAFT TABLE 4 SELECTION OF REPRESENTATIVE AND HEALTH PROTECTIVE CROP GROUPINGS Selected for Evaluation?

Yes ( Y) or No ( N) Rationale Root ( a) Y Expected to contribute significantly to exposure.

Vegetable ( b) Y Expected to contribute significantly to exposure.

Grain ( c) Y Expected to contribute significantly to exposure.

Fruit ( d) N Much less exposure potential compared to crop groups selected for evaluation. ( g)

Forage ( e) N Ingestion of animal products eliminated from further evaluation in scoping stage. ( g)

Field ( f) N Field crops that are ingested by humans are considered in their appropriate crop groups.

Notes: Bold = Selected as a representative and health protective crop grouping and included in the RBC equation.

RBC = Risk Based Concentration Y = Yes, crop grouping expected to contribute significantly to exposure and included in the RBC equation.

N = No, crop grouping not expected to contribute significantly to exposure and not included in the RBC equation.

( a) Root crops are also called unexposed vegetables or protected vegetables. Root crops include: beets,

carrots, fennel, onions, parsnip, potatoes, radish, rutabaga, turnip, and mangel.

( b) Vegetable crops are also called exposed or unprotected vegetables. Vegetable is a large broad category of crops.

Examples of different types of vegetables are leafy ( e. g., endive, kale, lettuce, swiss chard, spinach, and water cress), head and stalk ( e. g., artichoke, asparagus, broccoli, brussel sprout, cabbage, cauliflower, celery, and peppers).

Several fruits are also included in the vegetable category, because, they are cultivated as vegetables ( i. e., cucumber,

eggplant, and tomato).

( c) Grain is a large broad category of crops. Grains can be designated as field grains, silo grains, forage grains, or small or large grains. Only grains consumed by humans are included in this group. These grains include barley, corn,

millet, oat, rice, rye, and wheat.

( d) Fruit crops can be designated as vine crops ( grape), tree crops ( nuts or lemon, lime, and orange) or sweet fruits ( e. g., apple, cantaloupe, fig, grape, kiwi, rhubarb, pear, and strawberry).

( e) Forage crops are crops grown solely for the purpose of feeding cattle.

( f) Field crop is a general term for crops grown on fields. Examples of field crops include corn, cotton, potatoes,

soybeans, tobacco, or wheat. Field crops that are ingested by humans are evaluated within their appropriate crop grouping ( e. g., potatoes as root crops, wheat as grain).

( g) CDFA ( 1998) eliminated fruit and forage crops from the development of RBCs by demonstrating considerably less exposure to arsenic, cadmium, and lead, and therefore risk, for these crop groups.

Potential Crop Groups DRAFT FIGURES FIGURE 2. NARROWING THE SCOPE OF THIS SCREENING LEVEL EVALUATION  FOCUSING ON THE FERTILIZER PRODUCTS, METALS, AND EXPOSURE SCENARIO OF HIGHEST CONCERN Nitrogen Phosphate Potash NPK for phosphorous NPK for nitrogen Various Secondary and Micronutrients Fertilizer Products Phosphate Fertilizers ( b)

Micronutrient Fertilizers METAL CONCENTRATION ( a) Aluminum, antimony, arsenic, barium,

beryllium, bismuth, boron, cadmium,

chromium, cobalt, copper, iron, mercury,

manganese, molybdenum, nickel, lead,

radium, selenium, silver, strontium,

titanium, thorium, uranium, vanadium,

zinc Metals arsenic, cadmium, chromium, cobalt,

copper, lead, mercury, molybdenum,

nickel, radium226, selenium,

vanadium, and zinc TOXICITY ( a) Exposure Scenario Occupational and Public · Ingestion soil/ fertilizer · Dermal contact soil/ fertilizer · Inhalation particulates · Ingestion animal products ( beef, fish, milk)

· Ingestion crops ( grain,

vegetable, fruit, roots,

forage, vine)

Applicator ( c):

· Ingestion and dermal contact with fertilizer · Inhalation particulate Public

Farm Family:

· Ingestion crops,

( grain, vegetable and root)

· Ingestion and dermal contact with soil EXPOSURE ( a)

( a) This is the primary factor considered when selecting the product.

( b) Phosphate fertilizers include phosphate only and NPK for phosphate fertilizers.

( c) Occupational exposure ( i. e., applicator) was evaluated in TWG ( 1999a, b). DRAFT uptake leaching uptake runoff SOIL incidental ingestion dermal contact uptake Fish ingestion Crops ingestion Ground Water ingestion of drinking water Foraging Cattle ingestion of animal products ( beef and milk) volatilization wind blown dispersion Air inhalation Application of Inorganic Fertilizer Potential Indirect Media of Exposure exposure route Potential Direct Media of Exposure exposure route transport pathway FIGURE 3. POTENTIAL EXPOSURE PATHWAYS OF METALS OF POTENTIAL CONCERN ( MOPC) IN INORGANIC FERTILIZER POST APPLICATION INCLUDES: TRANSPORT PATHWAYS, MEDIA OF POTENTIAL CONCERN, AND ASSOCIATED EXPOSURE ROUTES Surface Water incidental ingestion dermal contact uptake KEY: uptake Crops ingestion Indicates: Excluded from further consideration, not a major exposure pathway.

DRAFT 17 DRAFT SECTION 2.0 ¾ DERIVATION OF RISK BASED CONCENTRATIONS ( RBCS)

As noted in the introduction, this evaluation uses a standard, back calculation, risk based approach to evaluate potential health risks. RBCs that are nationally representative and health protective are derived.

As defined in Section 1.0, RBCs are derived to represent and evaluate:

· 2 categories of inorganic fertilizers: phosphate fertilizers and micronutrient fertilizers; · 12 MOPC: arsenic, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium, vanadium, and zinc; and 1 radionuclide, radium 226; · Farm resident, including adult and child; · 3 routes of exposure;  Unintentional ingestion of soil following fertilizer application,  Dermal contact with soil following fertilizer application,  Ingestion of crops, which are broken out into 3 crop groups: root, vegetable, and grain; and · Both single crop and multi crop farm scenarios.

Risk Based Concentration ( RBC) Equation The RBC equation is developed using standard USEPA risk practices and exposure parameters ( USEPA 1989). 23 The standard equation to calculate risk combines 3 factors: estimated intake from exposure, toxicity of the element of interest ( in this case MOPC), and concentration of the MOPC in the media of concern ( i. e., fertilizer or product). In a back calculation risk based approach, the equation is arranged to solve for the RBC using an estimate of potential exposure, toxicity, and an acceptable risk level. 24 The RBC equation for the single crop farm is presented below. The equation integrates the 3 potential routes of exposure.

23 The standard USEPA exposure ( intake) and risk equations were modified to fit the scenario evaluated in this report. 24 Standard USEPA guidance presented in USEPA ( 1991). 18 DRAFT Equation 1. RBC for the Single Crop Farm )]} * * * * * ( THI or TR ) * * * * * * ( ) * * * * * * [( * / 1 * { * THI or TR TOX PUF AT RAFc IRc EF ED TOX AT BW ABS AF SA EF ED TOX AT BW CF RAFs IRs EF ED FON AR SACF RBC + + = where:

where:

RBC = Risk Based Concentration ( mg MOPC/ kg product); TR/ THI = Acceptable Target Risk or Hazard Index ( Unitless); AR = Application Rate ( g/ m2 year); FON = Fraction of Nutrient ( unitless); SACF = Soil Accumulation Factor ( m2 year/ g); ED = Exposure Duration ( years); EF = Exposure Frequency ( days/ year); BW = Body Weight ( kg); AT = Averaging Time ( days); CF = Conversion Factor ( 1X 10 6 kg/ mg); IRs = Ingestion Rate Soil ( mg/ day); SA = Surface Area ( cm2/ event day); AF = Adherence Factor ( mg/ cm2); IRc = Ingestion Rate Crops ( kg/ day); RAF = Relative Absorption Factor ( RAF) ( unitless); ABS = Dermal Absorption Factor ( unitless); PUF = Plant Uptake Factor ( unitless); and TOX = Toxicity Values ( mg/ kg day or mg/ kg day   1).

The RBC equation for the multi crop farm scenario is more complicated than the RBC equation for the single crop farm, because all three crop groups are integrated into one equation. Yet, each crop group has a different AR and PUF. The RBC equation for the multi crop farm scenario is presented below. Note the addition of a new factor, Fraction of Land ( FOL), in the equation. FOL is used to fractionate the addition of MOPC to soil by the different application Fertilizer Soil Ingestion Incidental SIFsi Factor Intake Summary AT BW CF RAFs IRs EF ED / ) ( * * * * * = Fertilizer Soil Contact Dermal SIFd Factor Intake Summary AT BW CF ABS AF SA EF ED / ) ( * * * * * * = Crop Ingestion SIFc Factor Intake Summary AT RAFc IRc EF ED ) ( * * * = 19 DRAFT rates for the different crop groups. Also note the use of SIFs in the equation. SIFs are summary intake factors that are derived for the single crop farm in Equation 1.

Equation 2. RBC for the Multi Crop Farm } * * ] * ) * * [( * / 1 * { THI or TR } * * ] * ) * * [( * / 1 * { THI or TR } * * ] * ) * * [( * / 1 * { * ( THI or TR TOX SIFg PUFg FOLg TOXd SIFd TOX SIFs FON ARg TOX SIFr PUFr FOLr TOXd SIFd TOX SIFs FON ARr TOX SIFv PUFv FOLv TOXd SIFd TOX SIFs FON ARv SACF RBC + + + + + + + + = where:

FOL = Fraction of Land ( unitless) ( discussed below) v = Vegetable r = Root g = Grain As discussed in Section 1.0, California is the largest multi crop farming state; so, the multi crop RBC is based on a multi crop farm in this region. Gross estimates of the percentage of acreage dedicated to each crop group in California were made based on a rough review of agricultural data ( crop acreage harvested) obtained from USDA ( 1999). In addition, CDFA ( 1998) was consulted for FOLs. FOLs of 50% grain, 40% vegetable, and 10% root are used to calculate multi crop RBCs. 24 Acceptable Target Risk ( TR) or Hazard Index ( THI)

In keeping with standard USEPA practices, a target cancer risk ( TR) of 1X 10 5 and a target hazard index ( THI) of 1 is used. 25 In general, USEPA uses an acceptable cancer risk of 1 X10 5 ( 1 in 10,000) and a hazard quotient ( HQ) of 1 for noncancer effects under it's hazardous waste programs. A HQ is the determination of noncancer risk for an individual MOPC. If the noncancer effects of the individual MOPC were all the same, the THI ( of 1) would need to be reduced to account for the additive noncancer effects. However, since most of the MOPC are associated with different noncancer effects ( i. e., different toxic endpoints) the THI does not need to be reduced below 1.26 Summary Intake Factor ( SIF) Parameters Summary intake factors ( SIFs) combine biological exposure parameters and absorption factors to estimate intake from exposure. They are standard methods, intended to simplify the calculation 24 CDFA ( 1998) also uses these FOLs to develop RBCs for their multi crop scenario. 25 CDFA ( 1998) and USEPA ( 1999b) use these acceptable risk and HQ levels in their fertilizer risk assessment. 26 Associated target organs or target effects for each noncarcinogen are presented in ` Toxicity Assessment'. 20 DRAFT of the RBC. Biological exposure parameters are related to behavior and are age dependent. They include: exposure duration ( ED), exposure frequency ( EF), body weight ( BW), averaging time ( AT), ingestion rates ( IR), skin surface area ( SA), and adherence factor ( AF). The values for all of these exposure parameters were developed from USEPA references and are intended to represent the reasonable maximum exposure ( RME). They are presented in Table 5. As defined under USEPA ( 1989), RME is the highest exposure that is reasonably expected to occur and that is well above the average case, but within the bounds of the high end exposure case. In addition, relative absorption factors ( RAF) and dermal absorption factors ( ABS) are developed ( as appropriate). The information used to derive RAF and ABS are presented in Appendix A. RAF and ABS are presented in Appendix A, Table A 1.

Exposure Duration ( ED)

The exposure duration ( ED) is the length of time exposure occurs and is typically the length of residence. The ED for the farm adult is 30 years. This ED is the USEPA recommended default ED at the 95th percentile for a family to reside in a home. The central default value ( 50% percentile) is 9 years. There is also a central residence time estimate for a farm presented in USEPA ( 1997a) ( about 17   18 years), however; the upper end estimate of general residence time is considered a better estimate for the RME scenario. The ED for the farm child is 6 years. This is the standard age frame considered when evaluating risks to children.

Exposure Frequency ( EF)

Exposure frequency ( EF) represents how often ( days/ year) the potential for exposure occurs. The exposure frequency ( EF) for the farm adult and child is 350 days/ year for all exposure routes, including dermal contact and incidental ingestion of soil and crop ingestion. An EF of 350 days/ year is recommended when using daily ingestion rates ( excluding time away from home for vacation). In addition, an EF of 350 days/ year is most representative of a warm climate.

Averaging Time ( AT)

Averaging time ( AT) depends on the toxic effect assessed ( i. e., whether cancer or non cancer). For non carcinogens, intake is averaged over ED. In the RBC equation for non cancer, ED is in the numerator of the intake equation and AT is in the denominator ( AT= ED* 365 days/ yr). Therefore, AT and ED cancel each other out. For carcinogens, intake is averaged by prorating the cumulative dose over a lifetime ( i. e., 70 years = 25,550 days) ( USEPA 1989).

Body Weight ( BW)

USEPA standard default body weights ( BW) were used for both the farm adult and child. The BW values are averages; average is the recommended statistic for BW when evaluating the RME scenario ( USEPA 1989). The adult BW is 71.8 kg ( represents ages 18   75 years) and the child BW is 15.5 kg ( average BW from 6 months to 6 years for males and females) ( USEPA 1997a). 21 DRAFT Ingestion Rate ( IR)

Ingestion rate ( IR) is the amount of media of interest ( either soil or crop) ingested and is presented as an amount per day. IR correlates with BW, because IR correlates with age, which correlates with BW. Because IR correlates with BW, and the average BW is suggested for the RME scenario, IRs are also central estimates ( or averages). The IR for soil is different than the IR for crops ( and the IR for each crop group is different) as discussed below.

· Soil The incidental soil IR for an adult is 50 mg/ day. This is USEPA's recommended central estimate adult soil IR ( USEPA 1997a). There is no recommended high end estimate. In the past, typical USEPA risk assessments used adult soil ingestion rates of 50 mg/ day for an industrial setting and 100 mg/ day for a residential and agricultural setting ( USEPA 1997a). USEPA's most recent guidance ( 1997a) recommends an IR of 50 mg/ day. Regardless, whether using a soil ingestion rate of 50 mg/ day or 100 mg/ day, the effect on the RBC not significant, as discussed in the uncertainty section.

The soil IR for a child is 200 mg/ day. This is a conservative estimate of the mean. A high end estimated soil IR of 400 mg/ day was considered too high for this assessment, because, it is based on a short study period, and not usual daily activity ( USEPA 1997a). As with the adult scenario, the use of a 200 mg/ day or 400 mg/ day soil ingestion does not significantly influence the RBC ( as discussed in the uncertainty section).

· Crop IRs for each crop group ( i. e., vegetable, root, and grain) are developed from information presented in USEPA ( 1997a). Because the IR for crops varies by age group, and correlates with BW, the crop IRs are already averaged over BW. Therefore, BW does not appear as an independent parameter in the crop intake equation. In developing the crop IRs, the IRs for each crop group consider all of the data that are appropriate for that crop group ( as listed in Section 1.0). The crop IRs are weighted averages of the means, across the age groups of interest, on a per capita basis. Per capita intake rates are appropriate estimates for average intake of the general population ( USEPA 1997a). The IRs are based on data from the USEPA " key" and recommended study ( USEPA 1997a). This study is the Continuing Survey of Food Intakes by Individuals ( CSFII) from 1989 1991.

These IRs are based on " as consumed", which means fresh weight or wet weight. For children, the age groups included in the weighted average are ages 1   5. For adults, ages 6 70+ were considered. This age group also considers teens and young adults.

Vegetable Vegetable IRs are developed from data in Table 9 9 ( Per Capita Intake of Exposed Vegetables) and Table 9 10 ( Per Capita Intake of Protected Vegetables) in USEPA ( 1997a). Data for exposed vegetables considers all of the vegetables presented in the 22 DRAFT discussion of crop grouping in Section 1.0, plus additional vegetables not listed in this group. Protected vegetables in Table 9 10 in USEPA ( 1997a) are vegetables with a husk or thick skin ( not vegetables that grow underground or root vegetables). Examples, of these vegetables include pumpkin, squash, lima beans, peas, and corn. Several of these vegetables do not fit into the vegetable category, as defined for this report ( especially corn), however, all exposed vegetables were still included in developing the IRs for vegetables. The vegetable IR is the age weighted IR for protected plus exposed vegetables.

The vegetable IR for an adult is 1.7 g/ kg day. The vegetable IR for a child is 2.9 g/ kgday

Root The IRs for root crops are developed from data in Table 9 11 ( Per Capita Intake of Root Vegetables) ( USEPA 1997a). Examples of root vegetables considered in this table are potatoes, carrots, beets, garlic, onions, radish, turnip, and leeks.

The root IR for an adult is 1.1 g/ kg day and the root IR for a child is 2.1 g/ kg day.

Grain The IRs for grain are developed from data presented in Table 12 1 ( Per Capita Intake of Total Grains Including Mixtures) ( USEPA 1997a). These IRs are developed the same way as the IRs for vegetables and roots ( i. e., time weighted averaged, based on the mean, and per capita). Total grains presented in this table includes breads, sweets ( cakes, pie, and pastries), breakfast foods with grains, pasta, cereals, and rice and grain mixtures.

The grain IR for an adult is 3.4 g/ kg day and the grain IR for the child is 9.4 g/ kg day.

Fraction Ingested ( FI)

One parameter that is not shown in the RBC equation, but is factored in and needs to be mentioned is fraction ingested ( FI). FI can apply to any media of interest ( soil or crop) ingested, and is the fraction ( or portion) of the soil or crop that originates from the source ( in this case, soil following application of fertilizer, or crops grown on this soil). For the purposes of this screening level evaluation, all ( 100%) of the soil or crop is assumed to come from the farm, therefore, FI is 1. An FI of 1 is the most health protective ( conservative) FI value. Since FI is 1, for simplicity, it is not presented in the RBC equation.

Skin Surface Area ( SA)

Skin surface area ( SA) is the area of skin that is available for dermal contact with soil/ fertilizer. The skin SA is taken from the most recent USEPA ( 1998b) dermal guidance. Similar to IR, skin SA correlates with BW. Therefore, average or central estimates are recommended for the RME scenario. 23 DRAFT For soil exposure, the recommended central estimate of skin SA area for an adult is 5,700 cm2/ day; the recommended central skin SA for a child is 2,900 cm2/ day ( USEPA 1998b). The adult skin SA is based on a warm climate where more skin is likely to be exposed. The adult skin SA is based on the adult wearing short sleeved shirt, shorts, and shoes; the exposed areas are the head, hands, forearms, and lower legs. The child skin SA is also based on a warm climate scenario and a child wearing short sleeved shirt and shorts, but no shoes. For the child, the exposed SA area is 45% of the total skin SA ( USEPA 1998b).

Adherence Factor ( AF)

Adherence factor ( AF) is an estimate of the amount of soil that adheres to skin. As with the skin SA, the most recent USEPA dermal guidance ( 1998b) was consulted for AFs. AFs vary depending on the exposure scenario. For example, AFs are available for a groundskeeper, or nursery worker, or an archeologist. The AF selected for the adult is the USEPA recommended adult, default AF, 0.08 mg/ cm2 event. This AF is for the residential scenario and is based on outdoor gardening. The recommended default AF for a child is 0.3 mg/ cm2 event ( USEPA 1998b).

Absorption Parameters As can be seen in the RBC equation, there are two additional parameters in the SIF, relative absorption factor ( RAF) and percent dermal absorption ( ABS). These parameters adjust the estimated intake to an actual absorbed " dose." Absorbed dose refers to the amount of the MOPC that is actually absorbed into the blood stream following exposure and intake. RAF and ABS help to develop a more realistic RBC by estimating the fraction of MOPC that is actually absorbed into the bloodstream, not just the amount of exposure ( i. e., ingested or contacted). Absorption is representative of the fraction of the MOPC that is available ( i. e., bioavailable). Bioavailability is the fraction of specific contaminant in a medium ( e. g., soil or crop) that is absorbed into the bloodstream across physiological barriers. Without the incorporation of these factors, the RBCs may be largely overestimated. However, these parameters are only used, when appropriate and applicable data are available. Information supporting the RAFs is presented in Appendix A. For MOPC where data is not available to develop a RAF, a RAF of 100% is assumed. This is the case for most MOPC. An RAF is developed and incorporated into the RBC for arsenic and lead, as discussed below. In addition, for most MOPC, a default ABS for metals of 1% is used ( USEPA 1998b).

· Relative Absorption Factor ( RAF)

RAF is intended to ensure that the toxicity value and estimated intake are based on comparable estimates of intake ( both based on an absorbed or administered dose, and the same or similar medium). Therefore, RAF depends on ( 1) whether the toxicity value is an " administered" or an actual absorbed dose and ( 2) the absorption from both the medium of the toxicity study and the medium of interest ( i. e., soil or crop). RAF is the percent of the MOPC that is absorbed from the medium of interest [ following ingestion, and absorption through the gastrointestinal tract ( GI)] divided by the percent GI absorption used in the oral toxicity study. 24 DRAFT The estimated intake and associated toxicty of arsenic from the ingestion of soil is adjusted by a RAF. The oral toxicity value for arsenic is based on an administered dose from exposure to arsenic in drinking water. An applicable and acceptable study on the bioavailability of arsenic was found. This study determined a bioavailability of arsenic in soil of 42% ( Rodriquez et al. 1999). The percent absorption of arsenic in drinking water is 95% ( USEPA 1999c). Therefore, a RAF for arsenic in soil of 44% ( 42% ¸ 95%) is incorporated into the RBC.

In addition, the estimated intake of lead into the GI tract following unintentional ingestion of lead in soil and ingestion of lead in crops, and the associated toxicity, is adjusted by a RAF. Since the toxicity of lead is based on an acceptable blood lead level, which is an absorbed level ( or dose), the intake also needs to be adjusted to an absorbed dose. The GI absorption of lead in soil and crop following ingestion is 0.41, and 0.50, respectively ( USDHHS 1997). The estimated intake from unintentional ingestion of soil and ingestion of crops and associated toxicity is adjusted accordingly.

A default RAF of 100% ( or 1) is assumed for all other MOPC and their associated exposure routes.

· Percent Dermal Absorption ( ABS)

All of the toxicity values for the dermal route of exposure are based on an absorbed dose ( as described in the Toxicity Assessment Section). Therefore, intake from dermal contact needs to be in an absorbed dose. Percent dermal absorption ( ABS) estimates the amount of MOPC that is absorbed across the skin into the bloodstream following dermal contact. Screening level ABS are used ( 1% for all MOPC, except 3% for arsenic) and were obtained from ( USEPA 1998b).

Application Rate ( AR) and Fraction of Nutrient ( FON)

Application rate ( AR) is a very important parameter in the RBC equation and can influence the RBC greatly. As defined in the scoping stage of this evaluation ( Section 1.0), RBCs are developed for phosphate fertilizers and zinc micronutrient fertilizers. Application rates ( ARs) for phosphate and zinc micronutrient fertilizers are presented in Table 6.

Also discussed in Section 1.0, AR is dependent on the plant nutrient needs ( P or zinc) and the composition of the product, specifically, the percent nutrient ( percent P or percent zinc). ARs vary for different crops and different products. ARs for each of the three crop groups ( vegetable, root, and grain) are developed for phosphate and for zinc based on information presented in USEPA ( 1999a). However, these ARs are based on nutrient needs of crops and are not product specific ( i. e., they do not consider the percent nutrient of product). These ARs ( or nutrient needs) will vary depending on the percent nutrient of the product. For example, products with a higher percent of P will be applied less than a product with a low percent of P in order to meet the nutrient needs of the plant. The percent of P for phosphate fertilizers varies considerably from fertilizer to fertilizer ( as can be seen in Table 1, percent of P ranges from 2.0 70.1). 25 DRAFT RBCs are intended for screening level evaluations and need to be easy to use and flexible. Therefore, the RBCs are normalized to represent a 1 percent fraction of nutrient ( FON) content. These RBCs are called unit RBCs. Unit RBCs can easily be adjusted to represent a particular product with a certain percent nutrient content ( the concept of unit RBC and their adjustment is discussed in further detail in Section 4.0).

The ARs for P ( and thus phosphate fertilizers) are based on the appropriate and available crop data presented in USEPA ( 1999a). Data for all crops and every state, regardless of geographic area, are compiled into the database used to develop the ARs for P. The data set compiled for each crop group is presented in Appendix A. The ARs are the 95 upper confidence limit ( UCL) of the mean ( based on the assumption that the data is normally distributed). Although this data set may not be normally distributed, the 95UCL of the mean is considered an appropriate estimate because it is sufficiently high end. The ARs are presented in USEPA ( 1999a) in units of 1b/ acre yr. These ARs are converted to g/ m2 year by 0.11 g acre/ lb m2 ( for appropriate units in the RBC) and then adjusted to reflect a 1% FON.

The high end ARs for phosphate fertilizers are:

· Vegetable = 119 lb/ acre year ( 13 g/ m2 year); · Root = 157 lb/ acre year ( 17 g/ m2 year); and · Grain = 63 lb/ acre year ( 7 g/ m2 year).

There is limited information available on the application of micronutrients. The information and ARs presented in USEPA ( 1999a) are based on interviews with experts. The " high" AR for zinc micronutrient presented in USEPA ( 1999a) of 10 lb/ acre ( 1 g/ m2 year) is a best estimate. This is the AR used for all micronutrient fertilizers and for all crop groups.

Soil Accumulation Factor ( SACF)

The soil accumulation factor ( SACF) estimates how much of an MOPC accumulates in soil following annual applications ( over years of farming) and takes into account an estimated loss of MOPC in soil from transport of the MOPC into surrounding media. The accumulation and behavior of MOPC in soil from agricultural application depends essentially on ( 1) farming duration ( years) ( 2) the application rate ( AR) of the fertilizer ( 3) the concentration of the MOPC in the fertilizer and ( 4) the fate and transport of the MOPC in soil. Further, fate and transport depends on the soil condition, climatic conditions and MOPC specific parameters ( i. e., MOPC form, soil water coefficient, etc.). USEPA has developed models that estimate the accumulation of MOPC in soil following application ( USEPA 1990, 1993). These models were modified by CDFA ( 1998) for the purposes of developing an RBC ( Equation 3.0); the resulting equation is presented below.

The modified equation ( Equation 4.0) is also presented below. As can be seen in Equation 4.0, SACF is related to the duration of application, the depth of soil that is expected to accumulate MOPC, the potential loss of the MOPC from soil through potential transport ( or now considered loss) pathways, and limited soil characteristics ( e. g., bulk density). The fate and transport of the MOPC in soil, over years of farming, depends on the form of the MOPC, the type ( i. e., sandy or 26 DRAFT silty loam) and condition of soil ( e. g., the organic matter content of the soil, the pH of the soil) and the climatic conditions of the area. Because SACF depends on so many different factors, which all vary given any situation, not all situations can be represented when developing the RBC. Instead and in keeping with the intent of this screening level evaluation, a SACF is estimated that is based on nationally representative high end ( resulting in more protective RBCs) assumptions, and an SACF that is based on the most important parameters and loss pathways. The development of SACF does not consider MOPC specific factors ( except Kd), such as, the form of the MOPC ( speciation and complexation), and is based on general, not site specific, assumptions. All of the parameters used to calculate the SACFs are presented in Table 7. The SACFs are presented in Table 8.

Equation 3.0 Accumulated Soil Concentration s s K BD Z T K AR Sc * * * * - - * = 100 )] exp( 1 [

where: Sc = accumulated soil concentration ( mg/ kg); AR = application rate ( deposition rate) of metal ( g/ m2 yr); Ks = soil loss constant ( yr 1); T = total time period ( evaluation time) over which deposition occurs ( years); 100 = conversion factor ( mg m2/ kg cm2); Z = soil mixing depth ( cm); and BD = soil bulk density ( g/ cm3).

Equation 4.0 Soil Accumulation Factor ( SACF)

SACF =

s K BD Z T K s * * * * - - * - 100 )] exp( 0 . 1 [ 10 6 where: SACF = soil accumulation factor ( m2/ yr g); 10 6 = conversion factor ( kg/ mg); T = total time period over which deposition occurs ( years); Z = soil mixing depth ( cm); BD = soil bulk density ( g/ cm3); and Ks = soil loss constant ( yr 1).

Time Period of Application ( T)

MOPC are added to soil over years of farming. Because of losses from the root zone, the rate of accumulation of the MOPC in soil will slow over the years. Eventually, following application year after year, on the same soil, the concentrations of the MOPC are expected to reach a steady state. The number of years it takes the MOPC to reach steady state is assumed to be 50 years, 27 DRAFT except for lead where the application duration is 200 years. These application durations are developed in CDFA ( 1998).

Soil Mixing Depth ( Z)

Soil mixing depth ( Z) is the depth of soil that is expected to be tilled. A default Z of 20 cm is used ( USEPA 1998a).

Soil Bulk Density ( BD)

A default BD of 1.5 g/ cm3 from USEPA ( 1998a) is used. This BD is based on a loam soil.

Defining Potential Fate and Transport ( Loss Pathways) ( Ks)

As can be seen in Figure 3, chemicals in soils can be lost through four potential transport pathways including degradation, leaching, erosion, and volatilization. The loss of the MOPC through these transport pathways decreases the amount of MOPC that accumulates in soil and that is available ( 1) for exposure through direct contact with soil or ( 2) uptake into crops. Only leaching is considered a mechanism ( albeit a small amount) of metal loss from soil. 25 All of the other transport pathways are not considered in the development of SACF because they either are ( 1) not plausible or ( 2) they are inconsequential. 26 The equation that is used to determine loss due to leaching is presented below ( Equation 5.0). This equation is adopted from USEPA ( 1993).

Equation 5.0 Metal Loss Due to Leaching from Soil ) / 0 . 1 ( Q * + * * Q - + = d K BD Z Ev I P ksl where: ksl = metal loss due to leaching ( yr 1) P = average annual precipitation ( cm/ yr) I = average annual irrigation ( cm/ yr) Ev = average annual evapotranspiration ( cm/ yr) Kd = soil water partitioning coefficient ( mL/ g) Q = soil volumetric water content ( mL/ cm3)

Equation 5.0 was further reduced because irrigation is designed to counter loss due to evapotranspiration; therefore, evapotranspiration and irrigation are excluded from this equation.

25 Leaching of MOPC into groundwater, and subsequent ingestion of drinking water, was eliminated as an exposure pathway ( as presented in Figure 3). Although the amount of MOPC that leaches is expected to be small, and is not considered to contribute significantly to exposure, the loss of MOPC through leaching is still greater than the loss through other transport pathways. 26 The other 3 loss pathways, degradation, erosion, and volatilization were previously determined to ( 1) either not occur or ( 2) to be inconsequential as loss pathways for metals in agricultural soils ( CDFA 1998). 28 DRAFT Precipitation ( P)

A USEPA ( 1998a) default precipitation ( P) estimate of 28 cm/ year is assumed. This precipitation is a relatively low precipitation rate from a national perspective. Precipitation rates range across the country from approximately 18 cm/ year up to 165 cm/ year ( USEPA 1998a). The lower the precipitation rate the less potential for leaching and the more MOPC in the soil.

Soil Water Partitioning ( Kd)

Soil water partitioning coefficients ( Kd) are used to estimate how much of an MOPC is expected to move from the soil phase to the water phase. This movement of an MOPC to the liquid phase makes the MOPC more bioavailable. Bioavailable MOPC are available for movement away from soil, for example, through uptake into crops or leaching into groundwater. Kd is best determined from empirical studies and not modeled. 27 Kd is the ratio of the total soil metal concentration over the dissolved metal concentration ( or metal in the water phase). Kd is highly influenced by the characteristics of the soil ( e. g., organic matter content and especially pH). Generally, the lower the pH, the higher the Kd ( and the more soluble and more bioavailable the MOPC).

The Kd values are taken from an article that compiled empirically derived Kds from existing literature and developed a distribution of these values. The literature presents Kds for most of the MOPC over different soil types ( clays and loams) and a pH range of 4.5   9.0 ( Baes and Sharp 1983). The Kd selected for use in the SACF is the mean value. Because there were no Kd values for mercury, nickel, and vanadium in Baes and Sharp ( 1983), Kds for these MOPC are adopted from USEPA ( 1995) and Gerriste et al. ( 1982). These values are also mean estimates. The soil type in Gerriste et al. ( 1982) is sandy soil and sandy loam with pH's of 5.0 and 8.0, respectively.

Soil Volumetric Water Content ( Q )

A default soil volumetric water content ( Q ) of 0.2 mL/ cm3 is used ( USEPA 1998b).

Plant Uptake Factors ( PUFs)

Like AR, plant uptake factor ( PUF) is a critical parameter in the RBC equation. 28 PUF estimates the amount of MOPC present in soil that is taken up by the crop. 29 PUF is MOPC specific and is determined through experimental studies that measure the concentration of MOPC in soil and then MOPC in plant tissue of plants grown on this soil. Basically, PUF is the ratio of total ( not extractable, as discussed below) MOPC concentration in plant over the MOPC concentration in soil. In addition to the influence of crop type and MOPC, there are many other factors that influence PUF. These factors include study design ( e. g., greenhouse or pot or field study), form of the MOPC, and the soil types and conditions of the study. Each of these factors is considered 27 As discussed in USEPA ( 1999b). 28 In CDFA ( 1998) sensitivity analysis, PUF was determined to be one of the most sensitive parameters for most of the RBCs. 29 PUF is also called transfer coefficient or transfer ratio. 29 DRAFT when selecting studies that are used to develop PUFs. A presentation of the study selection criteria are presented in Appendix B, along with the summary statistics for each PUF data set. PUFs that are used to calculate the RBCs are presented in Table 9.

Green House, Pot, and Field Studies Study design ( i. e., green house or pot or field) will influence the PUF. Generally, when both the plant root system and soil are confined, as in a green house or pot study, the opportunity for uptake of the MOPC by the plant is increased. The higher uptake could result from increased soil temperature and differences in evapotranspiration ( Chaney et al. 1999), and in comparison, in field studies, the root system has a greater space, and more dilute soil system, allowing less potential for MOPC uptake. Nevertheless, because of the sometimes limited information from field studies, greenhouse and pot studies are included in the PUF database. 30 Type of Fertilizer The chemical form of the MOPC in the fertilizer influences the PUF and the MOPC form is likely to be different for different types of fertilizers. In general, the form of the MOPC in fertilizer is different in organic fertilizer compared to inorganic fertilizer. Given that this evaluation is focused on inorganic fertilizers, studies using inorganic fertilizers are of most interest.

MOPC in inorganic fertilizers are generally impurities and are usually part of a relatively immobile complex. The plant uptake of MOPC in phosphate fertilizers is generally lower than some other fertilizers, like soluble chloride or sulfate salts. MOPC in these fertilizers, which are extremely soluble, are much more available for plant uptake. MOPC in inorganic fertilizers usually have higher plant uptake than MOPC in organic fertilizer. MOPC in organic fertilizers tend to have an increased capacity to sorb to soil because of the presence of several hydrous metal oxides ( aluminum, iron, and manganese) ( Chaney et al. 1999). In general, studies using organic fertilizers are not appropriate for developing PUFs for inorganic fertilizer application. However, studies using organic fertilizer ( sewage sludge) are included in the database if the addition of an organic fertilizer was more like the addition of an inorganic fertilizer. These studies were used only if:

1. The experiment included an untreated ( control) plot with typical plant yields. Control plots with atypically low plant yields were assessed to be inadequately fertilized and, therefore, inappropriate for evaluating PUFs. 2. Sludge had been added many years ago and MOPC concentrations in soil had reached steady state. 3. Flyash was added to soil at nontoxic levels, and like sludge, was allowed to reach steady state with the surrounding soil.

30 USEPA ( 1999b) conducted a sensitivity analysis on the use of field versus pot studies for estimating fertilizer risks and found data from field studies to be the most appropriate information to use for this scenario. More specifically, the PUFs developed from pot studies are much higher than the PUFs from field studies; therefore, field studies are more appropriate for the exposure scenario. 30 DRAFT Soil Type and Condition PUF is also influenced by soil type ( e. g., sandy silty loam, sand) and soil conditions ( e. g., pH, cation exchange capacity, temperature, and moisture content), because, these factors will affect the form and behavior of the MOPC in soil. The studies included in the PUF database represent a wide variety of soils and soil conditions covering a large range of chemical and physical soil properties. The database included information obtained throughout the US and some information from Canada, Europe, Australia and elsewhere. An evaluation of the variability of these specific soil factors was not conducted on the PUF database, however, the database is considered large enough to average out the affects of these variables. In addition, a high end estimate of the PUF was used in developing the RBC to represent conditions where high plant uptake may occur.

Studies Excluded from Consideration Studies were excluded from the PUF database because insufficient information was presented to be useful. In particular, studies that did not report total metal soil concentrations ( or at least sufficient data to calculate total metal soil concentration) were excluded from the database. These studies typically report an extractable ( or plant available) soil concentration. Plant available ( i. e., extractable) MOPC concentration in soil does not correlate well with total MOPC soil concentration because of the different methods of extraction and is not considered a good value for estimating PUFs. 31 In general, PUFs developed using extractable MOPC concentrations are lower than PUFs using total MOPC concentrations.

In addition, studies where the methods were deemed to be inappropriate or not applicable for this scenario, were excluded. For example, studies where the application rates of the fertilizer were exaggerated, in comparison with practical application rates, were excluded from the database.

Presentation of PUFs The PUFs for each MOPC and crop group are presented in Table 9. The PUFs are presented in both dry and wet ( or fresh) weight. Most studies present plant and soil concentrations in dry weight; dry weights are generally more constant than fresh weight. However, PUFs need to be in the same units as the ingestion rates ( IR). IRs are presented in " as consumed basis" ( as consumed equals wet weight), therefore, the PUFs are converted from dry to weight wet. This conversion is done by multiplying the PUF in dry weight by a dry weight fraction for the crop over the dry weight fraction of the soil. The percent ( or fraction) of dry weight is derived from the percent of wet weight ( or moisture values) ( i. e., 100% weight  % wet weight = % dry weight). The fraction of dry weight for vegetable, root, and grains are 10%, 11%, 90%, respectively. These values are based on standard USEPA data ( USEPA 1997a). The fraction dry weight for soil is 90%. This fraction is based on sandy loam soil because this is the type of soil used in most of the studies. Regardless of soil type, the percent moisture content of soil is typically low; therefore, the dry weight fraction is usually high. The PUFs in Table 9 are the 90% upper confidence limit ( UCL) of the geometric mean, which is a high end estimate. Generally, the data for PUFs are log normally distributed.

31 Expert opinion from Dr. Roland Hauck of Florence, AL. Personal Communications. 1999 31 DRAFT Toxicity Assessment In developing the RBCs, the toxicity of the MOPC are evaluated for both cancer and non cancer endpoints ( note the exceptions for lead, as discussed below). Toxicity values were obtained from USEPA's online Integrated Risk Information System ( IRIS) ( USEPA 1999c), USEPA's Health Effects Assessment Summary Tables ( HEAST) ( USEPA 1997b) and USEPA Region III risk based concentration toxicity values ( USEPA 1999c). The oral and dermal toxicity values are presented in Table 10.

For several MOPC ( i. e., chromium and mercury) the toxicity values depend on the form of the MOPC. For example, toxicity values are available for chromium III and chromium VI. For mercury, toxicity values are available for elemental mercury, mercuric chloride, and methyl mercury. Assumptions about the form of the MOPC that is likely to be found in soil following years of application of inorganic fertilizer are made and the appropriate toxicity values are used to calculate the RBC. In summary, chromium III and mercuric chloride ( or divalent mercury) are more likely to be found in soil and be available for uptake and potential exposure, compared to the other forms of these MOPC.

Carcinogenic Effects For MOPC exhibiting carcinogenic potential, cancer slope factors ( SF) are developed by USEPA's Carcinogen Risk Assessment Verification Endeavor Work Group ( CRAVE). These slope factors are developed from chronic animal studies or, where possible, human epidemiological data, and represent the excess lifetime cancer risk associated with various levels of exposure. Cancer slope factors ( SFs) are expressed as in terms of dose in units of ( mg chemical/ kg body weight/ day) 1. They describe the upper bound increase in an individual's risk of developing cancer over a 70 year lifetime per unit of exposure or dose, where the unit of acceptable exposure is expressed as mg chemical/ kg body weight/ day ( mg/ kg/ day). In addition to developing the SF, USEPA assigns a weight of evidence classification for each carcinogen, which are also provided in Table 10.

Non Carcinogenic Effects Toxicity criteria for chemicals potentially causing noncarcinogenic effects are expressed as references doses ( RfDs). The RfD is a threshold level of beyond which toxic effects may result. RfDs are expressed in units of dose ( mg chemical/ kg body weight/ day). Chronic oral RfDs are developed to be protective for long term exposure to a chemical. To derive a RfD, a series of professional judgements are made to assess the quality and relevance of the human or animal data and to identify the critical study and the toxic effect. A toxicity level from the critical study, preferably the highest no observable adverse effect level ( NOAEL), is used. For each uncertainty associated with the NOAEL, a standardized factor is applied to establish a margin of safety. For example, uncertainty factors are used to account for sensitive subpopulations or the extrapolation of animal data to humans. An oral RfD for cadmium in both food and water is available. The toxicity value for food is used in this evaluation. 32 DRAFT Dermal Toxicity Values Toxicity values are available from USEPA for the oral ( i. e., ingestion) route of exposure, but are not available for the dermal route of exposure. Dermal toxicity values are developed by converting the oral toxicity values from an administered dose to an absorbed dose, following USEPA standard guidance ( USEPA 1989). For RfDs, the oral value is adjusted to a dermal toxicity value by multiplying the oral RfD by the fraction of MOPC that is absorbed in the gastrointestinal tract ( GI ABS). The oral SFs are converted to dermal SFs by dividing by the GI ABS. GI ABS values are also presented in Table 10. Note, if the oral toxicity value is already based on an absorbed dose ( e. g., cadmium), then no adjustment is necessary. The GI ABS values are from the chemical specific Agency for Toxic Substance Disease Registry ( ATSDR) toxicological profiles.

Toxicity Value for Lead No RfD or CSF has been established for lead ( USDHHS 1997). The general consensus on evaluating lead exposure and toxicity is through measuring blood lead levels ( NAS 1980). USEPA and ATSDR recommend a fetal acceptable blood lead concentration of 10 m g/ dL ( PbB fetal, 0.95, goal). This level is as an upper limit indicator below which no adverse effects would be expected. The USEPA approach for developing acceptable concentrations for blood lead was used in developing the acceptable blood lead concentration. The acceptable fetal blood lead level of 10 m g/ dL is used to develop a target blood lead concentration ( PbB a, c, g). In addition, biokinetic slope factors ( BKSF) for the different exposure routes and the child and adult are used to convert the estimated intake to a blood lead level ( DTSC 1992). 32 32 CDFA ( 1998) used the same biokinetic slope factors. TABLES TABLE 5 VALUES, DESCRIPTIONS, AND REFERENCES FOR BIOLOGICAL EXPOSURE PARAMETERS ( a)

Parameter Units Adult Descriptor Child Descriptor Reference Exposure Duration ( ED) years 30 RME default, 95th percentile length of residence 6 typical RME default USEPA ( 1997a)

Exposure Frequency ( EF) days/ year 350 daily contact; days/ year at home 350 daily contact; days/ year at home USEPA ( 1989)

Averaging Time ( AT) days Cancer 25,550 prorated over a lifetime of 70 yrs 25,550 prorated over a lifetime of 70 yrs USEPA ( 1989)

Non cancer 10,950 averaged over ED 2,190 averaged over ED USEPA ( 1989)

Body Weight ( BW) kg 71.8 default, mean 15.5 mean ( b) USEPA ( 1997a)

Ingestion Rates ( IR) default, conservative Soil estimate of the mean Crop Vegetable 1.7 mean ( c) 2.9 mean ( d) USEPA ( 1997a)

Root 1.1 mean ( c) 2.1 mean ( d) USEPA ( 1997a)

Grain 3.4 mean ( c) 9.4 mean ( d) USEPA ( 1997a)

Fraction Ingested ( FI) unitless 1 NA 1 NA NA Skin Surface Area ( SA) cm 2 day 5,700 RME default ( f) 2,900 RME default ( f) USEPA ( 1998b)

Adherence Factor ( AF) mg/ cm 2 day 0.08 RME default ( f) 0.3 RME default ( f) USEPA ( 1998b)

Notes: NA = Not Applicable RBC = Risk Based Concentration RME = Reasonable Maximum Exposure USEPA = United States Environmental Protection Agency ( a) All values are intended to result in an RBC representative of an RME scenario.

( b) Calculated average for ages 6 months to 6 years for male and female.

( c) Calculated time weighted mean developed from key study. Represents per capita intake, ages 18 70+.

( d) Calculated time weighted mean developed from key study. Represents per capita intake, ages 1 5.

( f) Skin SA and AF values are central estimates. USEPA ( 1997a)

mg/ day g/ kg day 50 default, mean 200 DRAFT TABLE 6 APPLICATION RATES ( ARs) FOR PHOSPHATE FERTILIZERS AND ZINC MICRONUTRIENT FERTILIZERS Fertilizer Application Rate ( AR) ( a)

lb/ acre year ( b) g/ m2 year ( c) lb/ acre  year ( d) g/ m2 year ( c)

Vegetable 119 13 10 1.1 Root 157 17 10 1.1 Grain 63 6.9 10 1.1 ( a) Developed from information presented in USEPA ( 1999a). Rounded to the nearest whole number. ( b) High end estimate of data set compiled for each crop group, including all states, presented in Appendix B. The high end estimate is the 95% upper confidence limit ( UCL) of the mean, assuming a normal distribution.

( c) Converted to appropriate units for the RBC equation ( g/ m 2 year) by multiplying by the conversion 0.11 g acre/ lb m 2. ( d) Limited data is available on the application of micronutrient fertilizers, therefore, this is a high end best estimate based on industry experts, as presented in USEPA ( 1999a). Crop Group Phosphate Zinc Micronutrient DRAFT TABLE 7 PARAMETERS USED TO CALCULATE SOIL ACCUMULATION FACTORS ( SACFs)

Parameter Value Application Time Period ( T) ( yrs) 50 ( a) Soil Depth ( Z) ( cm/ yr) 20 ( b)

Bulk Density ( BD) ( g/ cm 3) 1.5 ( b)

Soil Loss ( Ks) ( yr 1) ( c) Arsenic 0.14 Cadmium 0.14 Chromium 0.00042 Cobalt 0.017 Copper 0.042 Lead 0.0094 Mercury 0.0028 Molybdenum 0.046 Nickel 0.015 Selenium 0.33 Vanadium 0.084 Zinc 0.058 Precipitation ( P) ( cm/ year) 28 Soil Volumetric Water Content ( mL/ cm 3) 0.20 Soil Water Partition Coefficient ( Kd) ( L/ kg) Arsenic 6.7 ( d) Cadmium 6.7 ( d) Chromium 2200 ( d) Cobalt 55 ( d) Copper 22 ( d) Lead 99 ( d) Mercury 330 ( e) Molybdenum 20 ( d) Nickel 63 ( e) Selenium 2.7 ( d) Vanadium 11 ( e) Zinc 16 ( d)

( a) Reasonable assumption for T developed in CDFA ( 1998). A T of 200 yrs is used for lead. ( b) Obtained from USEPA ( 1998a). ( c) Calculated. ( d) Obtained from Baes and Sharp ( 1983). ( e) Obtained from Gerritse et al. ( 1982) and USEPA ( 1995).

DRAFT TABLE 8 SOIL ACCUMULATION FACTORS ( SACFs)

MOPC SACF ( a) m2/ yr g Arsenic 2.4E 05 Cadmium 2.4E 05 Chromium 1.6E 04 Cobalt 1.1E 04 Copper 6.9E 05 Lead 3.0E 04 Mercury 1.6E 04 Molybdenum 6.5E 05 Nickel 1.2E 04 Selenium 1.0E 05 Vanadium 3.9E 05 Zinc 5.4E 05 Notes: MOPC = Metal of Potential Concern ( a) Calculated.

DRAFT TABLE 9 PLANT UPTAKE FACTORS ( PUFs) FOR EACH CROP GROUP Metal PUF ( mg MOPC/ kg plant/ mg MOPC/ kg soil) ( unitless) ( a) of Potential Dry Weight ( b) Wet Weight Concern ( MOPC) Vegetable ( c) Root ( d) Grain ( e) Vegetable Root Grain Arsenic 0.3 0.05 0.03 0.03 0.0061 0.03 Cadmium ( f) 1.7 0.93 0.12 0.17 0.11 0.12 Chromium ( g) 0.0014 0.0014 0.037 0.00014 0.00018 0.037 Cobalt 0.05 0.03 0.02 0.005 0.0037 0.02 Copper 0.034 0.22 0.31 0.0034 0.027 0.31 Lead 0.08 0.05 0.05 0.008 0.0061 0.05 Mercury 0.61 0.67 0.26 0.061 0.082 0.26 Molybdenum 1.1 0.15 0.22 0.11 0.018 0.22 Nickel 0.15 0.07 0.05 0.015 0.0086 0.05 Selenium 0.88 0.76 0.57 0.088 0.093 0.57 Vanadium ( h) 0.007 0.007 0.007 0.0007 0.00086 0.007 Zinc 1.7 0.46 0.58 0.17 0.056 0.58 ( a) PUFs are the 90% upper confidence limit ( UCL) of the geometric mean, which is considered a high end estimate. ( b) Converted to wet weight ( ww) using the dry weight ( dw) fraction. Dry Weight Fractions are: vegetable = 91% moisture, 9% dry; root = 89% moisture, 11% dry; grain = 10% moisture, 90% dry; and soil ( based on sandy loam) = 10 % moisture, 90% dry ( USEPA 1997a). Example of dw to ww conversion: PUF arsenic, vegetable dw * dw fraction vegetable/ dw fraction soil = 0.3 * 0.09/ 0.90 = 0.03 ( c) Vegetable database consists of data for broccoli, brussel sprouts, cabbage, cauliflower, cucumber, eggplant, kale, lettuce, pepper, spinach, swiss chard, and tomato. ( d) Root crop database consists of data for beet, carrot, fennel, mangel, onion, parsnip, potato, radish, and rutabaga. ( e) Grains database consists of data for barley, corn, millet, oats, rice, and wheat. ( f) Cadmium PUF does not consider the presence of zinc, which can decrease the cadmium PUF. ( g) The PUFs for chromium ( vegetable and root) were adopted from ( USEPA 1999b). ( h) Very limited data were found that could be used to develop a PUF for vanadium. This PUF is based on data for forage crops ( obtained from USEPA ( 1999b)).

DRAFT TABLE 10 ORAL AND DERMAL TOXICITY VALUES Noncancer Toxicity Value Cancer Toxicity Value GI ABS Fraction Oral Dermal Oral Dermal Metal of Potential RfD RfD ( a) Safety Target Organ SF SF ( a) Target Concern ( MOPC) Value Source ( mg/ kg day) ( mg/ kg day) Factor or Effect Source ( mg/ kg day) 1 ( mg/ kg day) 1 Tissue WOEC Source Arsenic 0.95 IRIS 3.0E 04 2.9E 04 3 skin IRIS 1.5E+ 00 1.5E+ 00 skin A IRIS Cadmium ( b)   1.0E 03 1.0E 03 10 kidney IRIS

Chromium ( III) ( c) 0.02 USDHHS 1993 1.5E+ 00 3.0E 02 1,000 none observed IRIS    D IRIS Cobalt 0.44 USDHHS 1992 6.0E 02 2.6E 02 10 blood RBC

Copper 0.97 USDHHS 1989 4.0E 02 3.9E 02   RBC    D IRIS Lead   10 ug/ dL acceptable fetal blood lead level and biokinetic slope factors specific to age group and exposure route. B2 USEPA 1996 Mercury ( d) 0.07 IRIS 3.0E 04 2.1E 05 1,000 autoimmune, kidney IRIS    C IRIS Molybdenum 1 ( f) 5.0E 03 5.0E 03 30 joints, blood IRIS

Nickel ( e) 0.007 USDHHS 1995 2.0E 02 1.4E 04 300 decreased organ weight IRIS

Selenium   5.0E 03 5.0E 03 3 liver, CNS ( selenosis) IRIS    D IRIS Vanadium 0.03 USDHHS 1990 7.0E 03 2.1E 04 100  HEAST

Zinc 0.81 USDHHS 1994 3.0E 01 2.4E 01 3 blood IRIS    D IRIS Notes:  = Not Applicable or Not Available CNS = Central Nervous System GI ABS = Gastrointestinal Absorption Fraction HEAST = Health Effects Assessment Summary Tables ( USEPA 1997b)

IRIS = Integrated Risk Information System ( USEPA 1999c)

RfD = Reference Dose SF = Slope Factor USDHHS = United States Department of Health and Human Services WOEC = Weight of Evidence Classification ( A = human carcinogen, B = probable human carcinogen, C = possible human carcinogen, D = not classifiable as to human carcinogenicity)

( a) Dermal toxicity values are not developed by the USEPA, so, the oral toxicity values are used. In most cases, the oral toxicity value is an administered dose and is not an absorbed dose ( note the incorporation of a percent dermal absorption value), therefore, the toxicity value also needs to be in an absorbed dose. Oral toxicity values that are administered are converted to absorbed dose by multiplying the oral RfD by the GI ABS or dividing the SF by the GI ABS ( USEPA 1989).

( b) Toxicity values are based on cadmium in food, which is based on an absorbed dose.

( c) Toxicity values are based on insoluble salts. As discussed in the Toxicity Assessment Section, chromium ( Cr) is expected to be primarily in the form of CrIII ( rather than CrVI) in soil and available for uptake.

( d) Toxicity values are based on mercuric chloride. As discussed in the Toxicity Assessment Section, mercuric chloride ( or divalent mercury) is assumed to be the most likely form of mercury found in soil. Based on oral administration of mercuric chloride in mice. A 1% GI ABS value was also reported.

( e) Toxicity values are based on soluble nickel salts.

( f) No GI ABS information was found for molybdenum; therefore, a GI ABS fraction of 1 was assumed. DRAFT 33 DRAFT SECTION 3.0 ¾ PRESENTATION OF RISK BASED CONCENTRATIONS ( RBCS) FOR METALS OF POTENTIAL CONCERN ( MOPC)

A summary of all of the parameters that go into deriving the risk based concentrations ( RBCs) are presented in Tables 11, 12, and 13. Table 11 summarizes the parameters used to calculate the summary intake factors ( SIFs); Table 12 presents the SIFs for each exposure pathway; and Table 13 provides the remaining parameters used to calculate the RBCs. The unit RBCs, based on a one percent fraction of nutrient ( FON), are presented in Table 14 for phosphate fertilizers and micronutrient fertilizers.

As seen in the tables, unit RBCs are calculated for a single crop farm and a multi crop farm for both an adult and a child. The lowest RBC for each MOPC is selected for screening human health risks and is presented in the last two columns of Table 14.

Note that for arsenic the adult farm resident has the lowest RBC because arsenic is a carcinogen and the exposure duration is much longer for an adult. The lowest RBCs for the remainder of the MOPC are for the child farm resident. The multi crop scenario always has the lowest RBC value because exposure is coming from all crop types not just one of the crop types. TABLES TABLE 11 SUMMARY OF ALL OF THE PARAMETERS AND ASSUMPTIONS USED TO CALCULATE THE SUMMARY INTAKE FACTORS ( SIFs) ( a)

Parameter ( b) Units Parameter Values Target Cancer Risk and Hard Quotient unitless  TR Target Cancer Risk 1.0E 05 THQ Target Hazard Quotient 1 Biological Exposure Parameters Adult Child EF Exposure Frequency days/ year 350 350 ED Exposure Duration years 30 6 AT Averaging Time days Cancer 25,550 25,550 Noncancer 10,950 2190 BW Body Weight kg 71.8 15.5 IRs Soil Ingestion Rate mg/ day 50 200 IRc Ingestion Rate g/ kg day Vegetables 1.7 2.9 Roots 1.1 2.1 Grains 3.4 9.4 AF Adherence Factor mg/ cm 2 0.08 0.3 SA Exposed Skin Surface Area cm 2/ day 5,700 RAF Relative Absorption Factor unitless Arsenic 0.42 1 Cadmium 1 1 Chromium 1 1 Cobalt 1 1 Copper 1 1 Lead 0.41 0.5 Mercury 1 1 Molybdenum 1 1 Nickel 1 1 Selenium 1 1 Vanadium 1 1 Zinc 1 1 ABS Dermal Absorption Factor unitless  Arsenic 0.03 Cadmium 0.01 Chromium 0.01 Cobalt 0.01 Copper 0.01 Lead 1 Mercury 0.01 Molybdenum 0.01 Nickel 0.01 Selenium 0.01 Vanadium 0.01 Zinc 0.01 Notes:

 Not Applicable ( a) The equations used to calculate the SIFs are presented below.

SIFs are calculated to simplify the calculation of the RBC, and are presented in Table 12.

( b) The development of all of these parameters is presented in Section 2.0.

SIF Calculations:

Unintentional Ingestion of Fertilized Soil Summary Intake Factor ( SIFsi) = ( ED* EF* IRs* RAFs* CF)/( BW* AT)

Dermal Contact with Fertilized Soil Summary Intake Factor ( SIFd) = ( ED* EF* SA* AF* ABS* CF)/( BW* AT)

Crop Ingestion Summary Intake Factor ( SIFc) = ( ED* EF* IRc* RAFc)/( AT) Soil ( s) Crop ( c) 2,900 DRAFT TABLE 12 SUMMARY INTAKE FACTORS ( SIFs) ( a)

Summary SIF Value Intake Factors ( SIF) Units Adult Child Unintentional Ingestion of Fertilized Soil ( SIF) si day 1 Cancer Arsenic ( a) 1.2E 07 4.5E 07 Noncancer Arsenic 2.8E 07 5.2E 06 Lead ( b) 2.7E 07 5.1E 06 All Other MOPC ( c) 6.7E 07 1.2E 05 Dermal Contact with Fertilized Soil ( SIF) d Cancer Arsenic 7.8E 08 1.4E 07 Noncancer Arsenic 1.8E 07 1.6E 06 All Other MOPC ( c) 6.1E 08 5.4E 07 Crop Ingestion Vegetable ( SIF) v Cancer Arsenic 7.0E 04 2.4E 04 Noncancer Lead ( b) 8.2E 04 1.4E 03 All Other MOPC ( c) 1.6E 03 2.8E 03 Root ( SIF) r Cancer Arsenic 4.5E 04 1.7E 04 Noncancer Lead ( b) 5.3E 04 1.0E 03 All Other MOPC ( c) 1.1E 03 2.0E 03 Grain ( SIF) g Cancer Arsenic 1.4E 03 7.7E 04 Noncancer Lead ( b) 1.6E 03 4.5E 03 All Other MOPC ( c) 3.3E 03 9.0E 03 ( a) Arsenic is the only MOPC that is evaluated for potential carcinogenicity.

( b) Lead SIFs are adjusted appropriately by biokinetic slope factors specific to age group and exposure route.

( c) The only parameters in the SIF equations ( presented below) that are MOPC specific, and therefore, can change the SIF to be MOPC specific, are RAF or ABS. If a MOPC specific RAF or ABS is not found, a default value is used; then the SIF is not specific MOPC, and therefore, is generic, and presented in the All Other MOPC row.

SIF Calculations:

Unintentional Ingestion of Fertilized Soil Summary Intake Factor ( SIFsi) = ( ED* EF* IRs* RAFs* CF)/( BW* AT) Dermal Contact with Fertilized Soil Summary Intake Factor ( SIFd) = ( ED* EF* SA* AF* ABS* CF)/( BW* AT) Crop Ingestion Summary Intake Factor ( SIFc) = ( ED* EF* IRc* RAFc)/( AT)