TECHNICAL SUPPORT DOCUMENT

Assessment of potential risks

from managing F019 waste

 from the motor vehicle

 manufacturing industry

18 December 2006

Disclaimer:

Mention of trade names or commercial products

 does not constitute endorsement or recommendation for use.Table of Contents

  TOC \o "1-3" \u  LIST OF TABLES	  PAGEREF _Toc154220866 \h  1

Glossary, acronyms and abbreviations	  PAGEREF _Toc154220867 \h  1

Executive Summary	  PAGEREF _Toc154220868 \h  7

1.  Risk Assessment Scope and Objectives	  PAGEREF _Toc154220869 \h  9

2.  Background	  PAGEREF _Toc154220870 \h  11

2.1   Zinc phosphating of motor vehicles	  PAGEREF _Toc154220871 \h  11

2.2   Motor vehicle manufacturing wastewater treatment	  PAGEREF _Toc154220872 \h  12

2.3   Sludge management techniques	  PAGEREF _Toc154220873 \h  12

3.  Identifying chemical constituents	  PAGEREF _Toc154220874 \h  13

3.1   Material Safety Data Sheet review	  PAGEREF _Toc154220875 \h  14

3.2   Review of other contributing wastewaters	  PAGEREF _Toc154220876 \h  17

3.3   Wastewater treatment and other process chemicals	  PAGEREF _Toc154220877 \h  17

3.4   Transformation of constituents during wastewater treatment	  PAGEREF _Toc154220878 \h  17

3.5   Expected chemical composition of sludge	  PAGEREF _Toc154220879 \h  18

3.6   Sampling data on chemical composition of sludge	  PAGEREF _Toc154220880 \h  19

4.  Exposure and Risk Assessment	  PAGEREF _Toc154220881 \h  25

4.1   Human activities	  PAGEREF _Toc154220882 \h  27

4.1.1   Waste accumulation practices	  PAGEREF _Toc154220883 \h  27

4.1.2   Waste transport practices	  PAGEREF _Toc154220884 \h  28

4.1.3   Waste placement in landfill	  PAGEREF _Toc154220885 \h  29

4.1.4   Waste release from landfill	  PAGEREF _Toc154220886 \h  29

4.2   Ecological receptor activities	  PAGEREF _Toc154220887 \h  30

4.2.1   Waste accumulation practices	  PAGEREF _Toc154220888 \h  30

4.2.2   Waste placement in landfill	  PAGEREF _Toc154220889 \h  31

4.2.3   Waste release from landfill	  PAGEREF _Toc154220890 \h  31

4.3   Summary of Potential Exposures Assessed	  PAGEREF _Toc154220891 \h  31

4.4   Fate, Transport, Exposure, and Risk Modeling	  PAGEREF _Toc154220892 \h  32

4.4.1   Overall methodology for this risk assessment	  PAGEREF _Toc154220893 \h  32

4.4.2   Delisting Risk Assessment Software, version 2.0	  PAGEREF _Toc154220894 \h  35

4.4.3   Industrial Waste Management Evaluation Model	  PAGEREF _Toc154220895 \h  37

4.4.4   EPA’s Composite Model for Leachate Migration with Transformation Products	  PAGEREF _Toc154220896 \h  38

4.4.5   Peer review of models	  PAGEREF _Toc154220897 \h  39

5.  Potential noncancer hazard to humans	  PAGEREF _Toc154220898 \h  40

5.1   Unlined landfill analysis	  PAGEREF _Toc154220899 \h  41

5.1.1.   High end results for unlined landfill	  PAGEREF _Toc154220900 \h  42

5.1.2	High end results discussion	  PAGEREF _Toc154220901 \h  48

5.1.3   Central tendency results and discussion	  PAGEREF _Toc154220902 \h  53

5.2.   Lined landfill analysis	  PAGEREF _Toc154220903 \h  56

5.2.1   Results of IWEM Tier 1 Evaluation	  PAGEREF _Toc154220904 \h  57

5.2.2   Results of D&P Evaluation	  PAGEREF _Toc154220905 \h  58

5.2.3 Discussion of IWEM and D&P analyses	  PAGEREF _Toc154220906 \h  59

6.  Potential carcinogenic risk to humans	  PAGEREF _Toc154220907 \h  60

6.1   Unlined landfill analysis	  PAGEREF _Toc154220908 \h  61

6.1.2   High end results	  PAGEREF _Toc154220909 \h  63

6.1.3   High end results discussion	  PAGEREF _Toc154220910 \h  64

6.1.4   Central tendency results and discussion	  PAGEREF _Toc154220911 \h  65

6.2 Lined landfill analysis	  PAGEREF _Toc154220912 \h  65

6.2.1.	Results of IWEM Tier 1 Evaluation	  PAGEREF _Toc154220913 \h  66

6.2.2   Discussion of IWEM analysis for cancer risk	  PAGEREF _Toc154220914 \h  66

7.  Potential ecological effects	  PAGEREF _Toc154220915 \h  66

7.1  Unlined landfill analysis	  PAGEREF _Toc154220916 \h  67

7.2 High end results	  PAGEREF _Toc154220917 \h  68

7.3 High end results discussion	  PAGEREF _Toc154220918 \h  71

7.4 Central tendency results and discussion	  PAGEREF _Toc154220919 \h  75

8.  Special cases: fluoride, sulfide, trivalent chromium, lead and cyanide	  PAGEREF _Toc154220920 \h  76

8.1 Human health effects	  PAGEREF _Toc154220921 \h  76

Fluoride	  PAGEREF _Toc154220922 \h  76

Sulfide	  PAGEREF _Toc154220923 \h  77

Trivalent chromium	  PAGEREF _Toc154220924 \h  77

Lead	  PAGEREF _Toc154220925 \h  79

8.2 Ecological effects	  PAGEREF _Toc154220926 \h  79

8.3 Potential explosive hazard	  PAGEREF _Toc154220927 \h  79

9.  Sources of uncertainty in risk and hazard estimates	  PAGEREF _Toc154220928 \h  80

9.1 Measurement Uncertainty	  PAGEREF _Toc154220929 \h  81

9.2 Model Uncertainty	  PAGEREF _Toc154220930 \h  92

9.3 Past and Future States	  PAGEREF _Toc154220931 \h  96

9.4 Summary of Overall Uncertainty	  PAGEREF _Toc154220932 \h  97

10.  Conclusions	  PAGEREF _Toc154220933 \h  98

11.  References	  PAGEREF _Toc154220934 \h  101

APPENDIX A	  PAGEREF _Toc154220935 \h  106

Fate, Transport, Exposure and Risk Models	  PAGEREF _Toc154220936 \h  106

Delisting Risk Assessment Software, Version 2.0 (DRASv2)	  PAGEREF _Toc154220937 \h  106

Industrial Waste Management Evaluation Model (IWEM)	  PAGEREF _Toc154220938 \h  109

EPA Composite Model for Leachate Migration with Transformation Products (EPACMTP)	  PAGEREF _Toc154220939 \h  111

References for Appendix A	  PAGEREF _Toc154220940 \h  112

APPENDIX B	  PAGEREF _Toc154220941 \h  115

DRASv2 Model Inputs	  PAGEREF _Toc154220942 \h  115

APPENDIX C	  PAGEREF _Toc154220943 \h  180

Waste Volumes and Physical Characteristics	  PAGEREF _Toc154220944 \h  180

 LIST OF TABLES

Table 1.  Constituents likely to be present in motor vehicle manufacturing wastewater (zinc phosphate conversion coating)

Table 2.  Chemical constituents analyzed in sludge from motor vehicle manufacturers

Table 3.  Chemical constituents detected in sludge from motor vehicle manufacturers

Table 4.  DRASv2 exposure pathways, exposure routes, receptors and activities

Table 5.  IWEM exposure routes, receptors and activities (noncancer)

Table 6.  IWEM exposure routes, receptors and activities (cancer)

Table 7.  Chemical constituents' estimated high-end hazard quotients at 90,000 cubic yards disposed

Table 8.  Chemical constituents' high-end estimated hazard quotients at 90,000 cubic yards disposed (adjusted for children’s exposure by a factor of 2.04)

Table 9.  Adjusted maximum concentrations for selected constituents

Table 10.  Detection frequencies and concentrations for constituents of potential concern (including selected data sets based on particular analytical methods used)

Table 11.  Estimated central tendency hazard quotients for constituents of potential concern at 21,760 cubic yards disposed

Table 12.  Ratio of D&P analysis composite lined landfill allowable levels to D&P unlined landfill allowable levels

Table 13.  Carcinogen slope factors (CSFs) and Inhalation unit risk factors (URFs)

Table 14.  Individual excess cancer risk probabilities calculated at 90,000 cubic yards disposed

Table 15.  Results from ecological risk analysis

Table 16.  Ratios of maximum detected waste concentrations to soil saturation and toxicity reference value exceedance concentrations

Table 17.  2003 F019 tons and cubic yards used in Economics Background Document and Technical Support Document

Table 18.  Uncertainty factors, modifying factors, and confidence ratings for IRIS oral Reference Doses

Table 19.  Uncertainty factors, modifying factors, and confidence ratings for IRIS inhalation Reference Concentrations

Table 20.  Uncertainty factor and confidence rating for PPRTV reference dose

Table 21.  Uncertainty factors and confidence ratings for ATSDR Minimal Risk Levels

Glossary, acronyms and abbreviations

Analyte – the specific chemical substances of interest in an analytical laboratory procedure.

ATSDR – Agency for Toxic Substances and Disease Registry.  An agency of the United States Department of Health and Human Services, Centers for Disease Control and Prevention.

Bentonite – a type of clay.

BMW – BMW Manufacturing Corporation.

Boiler blowdown – residual water from cleaning a boiler’s steam tubes.

Carcinogen – as used in this document, a particular chemical constituent evaluated for its potential to cause cancer due to its movement from a waste into air, water or soil, and subsequent ingestion, inhalation, or dermal contact by people.

CAS# or CAS Number - as used in this document, a CAS Registry Number®, which is a unique numerical identifier created and assigned to a chemical substance by CAS.  CAS Registry Number® is a Registered Trademark of the American Chemical Society.  CAS numbers shown in tables in this document are shown without hyphens, to facilitate numerical sorting.  However, the usual practice in writing CAS numbers is to hyphenate them according to the format XX-XX-X, XXX-XX-X, XXXX-XX-X, or XXXXX-XX-X, where “X” represents the integers in the registry number.

CFR – Code of Federal Regulations.  The CFR is a codification of the rules published in the Federal Register by Executive departments and agencies of the Federal Government. The CFR is divided into 50 titles which represent broad areas subject to Federal regulation, with environmental regulations contained in title 40, among others.

COPCs – Constituents of Potential Concern.  The chemical constituents present in F019 waste from motor vehicle manufacturers that may pose adverse human health or ecological effects (based on the analyses performed in this document).

CSF – Cancer Slope Factor.  An upper bound estimate, approximating a 95% confidence limit, on the increased cancer risk from a lifetime exposure to the chemical constituent.  This estimate, usually expressed in units of proportion (of a population) affected per milligram of constituent per kilogram of body weight per day, is generally reserved for use in the low-dose region of the dose-response relationship, that is, for exposures corresponding to risks less than 1 in 100.

D&P – Dyes and Pigments.

DAF – Dilution/Attenuation Factor.  The ratio of the concentration of a particular chemical constituent in landfill leachate to the model-predicted concentration of that constituent in a drinking water well.

Delisting – a request under consideration for an exemption from designation as a hazardous waste, or a similar request that has been granted an exemption from designation as a hazardous waste.  See 40 CFR §§ 260.20 and 260.22, and 40 CFR Part 261, Appendix IX.

DRASv2 – Version 2.0 of Delisting Risk Assessment Software.

DOT – United States Department of Transportation.

EPA – United States Environmental Protection Agency.

EPACMTP – EPA Composite Model for Leachate Migration with Transformation Products.

oF – degrees Fahrenheit.

F019 – identifying code for a hazardous waste (wastewater treatment sludge from chemical conversion coating on aluminum).  See 40 CFR 261.31 for the exact description of F019.

FR – Federal Register.  The official daily publication for rules, proposed rules, and notices of Federal agencies and organizations, as well as executive orders and other presidential documents.

Geocomposite - a synthetic liner overlying some type of clay liner.

Geomembrane – flexible membrane layer made of high-density polyethylene.

Geosynthetic – two geotextile outer layers with a uniform core of bentonite clay.

Geotextile – a textile designed for an application in which it is in contact with soils.

GM – General Motors.

Inh CSF – inhalation Cancer Slope Factor.

IWAIR – Industrial Waste Air Model.

IWEM – Industrial Waste Management Evaluation Model.

Kg – kilogram.

Landfill – a type of waste management unit in which waste is placed into or on the ground, for permanent disposal.

Leachate – any liquid, including any suspended components in the liquid, that has percolated through or drained from waste.

Leachate samples – samples created by using a leaching procedure designed to imitate the conditions the waste would undergo when disposed at a municipal solid waste landfill.

L – Liter.

MCL – Maximum Contaminant Level.

mg – milligram.

MRL – Minimal Risk Level.

MSDS – Material Safety Data Sheet(s).  A document that identifies the specific chemical composition of materials handled or used by workers, to inform the workers of potentially hazardous work practices.

Noncarcinogen – as used in this document, potential adverse noncancer health effects.  Note that we use the term noncarcinogen to refer to the type of health effect (health effects that are not cancer) rather than to refer to the substance’s potential to cause cancer.

Nondetect – an analytical laboratory result in which the analyte is not detected by the laboratory analytical instruments above the quantitation level for a particular analysis.

O CSF – oral Cancer Slope Factor.

OSHA – Occupational Safety and Health Administration.  An agency of the United States Department of Labor.

pH – hydrogen ion potential.

Receptors – plants, animals, insects, and other living organisms such as soil microorganisms that may be affected by chemical constituents in the wastes.

RCRA – Resource Conservation and Recovery Act.

SDWA – Safe Drinking Water Act.

SIM – Selected Ion Monitoring.  A type of analytical laboratory procedure.

TCLP – Toxicity Characteristic Leach Procedure.  An analytical laboratory procedure in which a waste sample is leached with an acidic leaching fluid to extract chemical constituents from the waste matrix, in order to simulate conditions in a landfill.

Totals samples – samples that give information on the total quantity of a particular chemical constituent in the wastewater treatment sludge.

TRI – Toxics Release Inventory.  A database containing information on toxic chemicals released into the environment.

ug – microgram.

URF – Unit Risk Factor.  The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 µg/L in water, or 1 µg/m3 in air.

Wastewater treatment sludge – watery solids obtained from performing wastewater treatment processes in order to remove contaminants from wastewater.

Zinc phosphating – a conversion coating process in which a layer of phosphate crystals are applied to a surface.

Executive Summary

This document describes a risk assessment to evaluate potential human and environmental hazards from disposing of wastewater treatment sludge in United States landfills.  The wastewater treatment sludge in question is from zinc-phosphate conversion coating on aluminum motor vehicle bodies, a manufacturing step that occurs before painting the motor vehicle bodies.  Its hazardous waste code, or designation, in 40 CFR 261.31 is “F019.”

The purpose of the risk assessment is to evaluate whether removing the hazardous waste designation from this waste could cause adverse effects.  Currently, the waste is regulated as hazardous waste, unless an EPA Region or authorized state environmental agency has promulgated a “delisting” that removes the hazardous waste designation (in many cases, subject to certain conditions).

The risk assessment addresses potential adverse human health effects that may be experienced by people living near the landfill, now or in the future, and potential adverse environmental effects that may be experienced by aquatic organisms living in a stream downhill from the landfill.  The potential adverse health and environmental effects would be due to exposure to constituents that are present in the waste when it is disposed in the landfill, and that are released from the landfill and move into air, nearby surface water, or groundwater underneath the landfill (either at the time of disposal or afterwards).

People and non-human organisms could be exposed to constituents in the sludge from other activities besides landfilling the sludge.  We have not evaluated those exposures for potential adverse health or environmental effects.   We believe that landfilling is the most plausible disposal practice, given the nature of the waste and the disposal practices evidenced by specific facilities that have requested delistings.  We evaluate disposal in an unlined landfill as the first step of the analysis (“unlined” means that the bottom of the landfill consists of bare soil).  For those chemical constituents that might cause problems when disposed in an unlined landfill, we conduct an additional analysis of disposal in a lined landfill (that is, the bottom of the landfill is designed and constructed with materials intended to retard the downward flow of water, including leachate, through the bottom of the landfill and into the subsurface).

For the landfill disposal scenario that we evaluate in this risk assessment, we narrow down the list of chemical constituents that appear to be most likely to move through the environment and cause adverse health and environmental effects.  For this narrowed list of constituents, we present estimates for a range of conditions that could occur – the higher end of the range, which we call the “high end” estimates, and estimates for an indeterminate point somewhere around, but likely above, the middle of the range, which we call the “central tendency” estimates.  The estimates are of potential adverse noncancer human health effects, probabilities of developing cancer, and adverse ecological effects.

For human noncancer effects, the central tendency estimates are well below the risk thresholds used as levels of concern by the Agency in hazardous waste listing determinations, indicating that under most conditions we would not expect residents living near an unlined landfill to experience adverse noncancer health effects.  For one chemical constituent - nickel - the high end estimate is slightly above the level that could cause adverse effects.  The high end estimate uses protective assumptions to predict the potential exposure that some residents living near the landfill might experience, from drinking well water that contains nickel released from the landfilled waste.  The model that we use in this part of the risk assessment estimates concentrations of constituents present in the waste, that move through groundwater to the drinking water well that the nearby residents rely on for their drinking, bathing and showering water.  Our overall assessment is that the models we use probably overestimate the potential adverse effects of disposing of the F019 waste in landfills.

For human cancer probabilities, we present point estimates of the high end and central tendency cancer probabilities.  The high end estimate for probability of developing cancer due to drinking water exposure to arsenic from the waste is above one in one hundred thousand (the level of concern), thus indicating that, under certain conditions, nearby residents (residents whose drinking water well is within one mile downgradient of the landfill) could have a very small probability (3 in one hundred thousand) of developing cancer due to exposure to arsenic present in the waste.  The central tendency estimate is below the risk thresholds used by the Agency in hazardous waste listing determinations, indicating that, under most conditions we would not expect residents living near the landfill to experience cancer effects from exposure to constituents in the landfilled waste.  As with the human noncancer effects estimates, the nature of the assumptions that we use in the models means that we may overestimate the actual risks.

For ecological effects, the high end estimates are generally below the levels causing adverse effects for stream-dwelling organisms, due to surface water concentrations in the stream.  Central tendency estimates for ecological effects confirm the high-end results, indicating that at median waste volumes and constituent concentrations, no adverse effects are predicted to occur.

The additional analysis is of potential health effects from disposal in a landfill designed and constructed with certain types of liners on the bottom of the landfill.  We perform this additional analysis for only those constituents that appeared to possibly pose concerns in the high end estimates of the unlined landfill scenario.  The results of this additional analysis indicate that those chemical constituents would be unlikely to pose the same concerns when landfills with certain types of liners are used for disposal.

Our overall assessment is that the models we use probably overestimate the potential adverse effects of disposing of the F019 waste in landfills.  The risk analysis evaluates high-end risks, and is designed to be protective of human health and the environment.

We develop the estimates of potential adverse health and environmental effects using the best data and tools that we have available.  When certain types of data are unavailable, we must use assumptions instead.  To err on the side of caution and be protective of public health and the environment, we use many assumptions that may cause the estimates of risk or hazard to be higher than the true risk/hazard.  The estimates in this document are uncertain.  If we could resolve some areas of uncertainty, the result would be that we might revise the estimates in an upward direction.  If we could resolve other areas of uncertainty, the result would be that we might revise the estimates in a downward direction.

1.  Risk Assessment Scope and Objectives

The purpose of this document is to describe the technical basis for possible revisions to the F019 hazardous waste listing in 40 CFR 261.31.  The revisions we are considering are for wastewater treatment sludge from zinc phosphating of aluminum-containing motor vehicle bodies.  If revised, the listing would not apply to these wastewater treatment sludges, provided they are managed in landfills meeting certain criteria.  The outcome of such a revision would be that facilities generating these sludges as wastes would no longer be required to dispose of them in landfills meeting the requirements of 40 CFR Parts 264, 265 and 270, and instead could dispose of them in landfills that are subject to the design criteria in 40 CFR 258.40, or possibly an alternate design criterion that references an maximum liner permeability rate.

EPA listed F019 wastes as hazardous as an outgrowth of the listing for wastewater treatment sludge from electroplating (F006).  The preamble to the proposed rule discusses the history of the F019 listing.  EPA listed F019 due to the presence of hexavalent chromium and cyanide (complexed).  See 40 CFR Part 261, Appendix VII.

The objectives of the risk assessment are to determine whether adverse human health or environmental effects may occur as a result of revising the F019 hazardous waste listing in 40 CFR 261.31.  The specific technical questions decision makers have, relating to this revision, include:

Who may be affected by adverse human health effects?

Where do they live?

What is the magnitude of the estimated adverse human health effect(s)?

When will the estimated adverse human health effect(s) occur?

What is/are the cause(s) of the estimated adverse human health effect(s)?

How sure are we about the magnitude of the estimated adverse human health effect(s)?

What organisms may be affected by adverse environmental effects?

Where are those organisms?

What is the magnitude of the estimated adverse environmental effect(s)?

When will the estimated adverse environmental effect(s) occur?

What is/are the cause(s) of the estimated adverse environmental effect(s)?

How sure are we about the magnitude of the estimated adverse environmental effect(s)?

This document describes:

the process of preparing for and applying paint and protective coatings to motor vehicle bodies (automobiles and light duty trucks), using a zinc phosphate conversion coating process;

the wastewater treatment processes used for wastewaters generated at the motor vehicle body assembly plants;

the wastewater treatment sludge generated from the wastewater treatment process (some of its physical and chemical properties); and

a risk assessment that describes estimates of risk from exposure to chemical constituents in the waste, for both humans and nonhuman organisms, from disposing of the wastewater treatment sludge.  The risk assessment in this document answers the questions listed above (although we can provide only a partial answer to question 4).

The scope of the risk assessment described in this document is of:

wastewater treatment sludge

from treating wastewater

that contains discarded nickel/zinc/fluoride-based conversion coating formulations currently (1996-2007) used by United States motor vehicle manufacturers

that is disposed in unlined landfills

for a period of either 20 or 30 years

thus affecting current and future residents living near those landfills

and aquatic organisms currently living in nearby streams

on a chronic basis (due to long-term exposure).

2.  Background

2.1   Zinc phosphating of motor vehicles

In the United States, assembling motor vehicle bodies generally involves:

- constructing the vehicle frame

- attaching parts such as the hood, trunk lid, and doors

- preparing the entire vehicle body for protective coatings that protect the vehicle body from rust or oxidation,

- applying the protective coatings, and then

- attaching numerous other vehicle parts and accessories.

Zinc phosphating is a process used immediately before applying paint on either steel or aluminum-and-steel motor vehicle bodies.  The zinc phosphating process creates a layer of phosphate crystals on the metal surface of the vehicle body.  Paint that is applied adheres to and becomes bonded with these phosphate crystals.  After the zinc phosphating step, motor vehicle manufacturers apply the paint, other coatings, and numerous rinse steps in between to ensure the quality of the various coatings and their adhesion to the motor vehicle body.

2.2   Motor vehicle manufacturing wastewater treatment

At motor vehicle manufacturing plants in the United States, wastewater from the zinc phosphating process is often combined with wastewater from other parts of the manufacturing plant.  Typically, the combined wastewaters are treated before disposal in a municipal wastewater treatment system.  As part of the wastewater treatment process, the solid particles and other pollutants in the wastewater are separated from the wastewater and form sludges.  The wastewater treatment sludge from motor vehicle manufacturing that uses a zinc phosphating process, when aluminum is a component of the motor vehicle bodies, is the waste (F019) that EPA is evaluating in this document.

The wastewater from the motor vehicle manufacturing plant enters the plant’s wastewater treatment system usually through floor drains, sumps and pipes that convey the wastewater to the wastewater treatment area.  In the wastewater treatment area, the wastewater usually undergoes a preliminary step of either removing floating oils with a skimmer, or removing the largest and heaviest solids in a device called a “grit chamber”, or both.  After oil and/or grit removal, the wastewater is generally subjected to various chemical reactions and physical processes designed to remove the solids from the wastewater, and in some cases to remove nitrogen, phosphorus, or trace elements that could pose a problem for the municipal wastewater treatment system receiving the wastewater for further treatment.  The various treatment techniques that occur after the preliminary oil/grit removal generally result in solids being removed from tanks at different stages of the wastewater treatment process; these solids are the sludge that is the subject of this document.

Most of the delisting petitions the motor vehicle manufacturing industry submitted to U.S. EPA describe the motor vehicle assembly process, zinc phosphating and application of other protective coatings, the resulting wastewaters, and wastewater treatment steps in considerable detail.  Copies of these delisting petitions are available in the EPA Regions 4, 5 and 6 rulemaking dockets.

2.3   Sludge management techniques

The solids (sludge) removed from the treatment tanks are usually combined and pressed in a mechanical device called a filter press to remove excess water.  After pressing, the sludge is usually placed in containers for transport to a landfill located away from the manufacturing facility.  Usually the transport container is a large open-topped rectangular metal container called a “roll off box” which is transported by truck.  In some cases the transport container might be an open-topped rail transport container called a “gondola.”  When the transport container is full, the motor vehicle manufacturer or wastewater treatment plant operator arranges for its removal and transport to a disposal site, usually a landfill located at some distance from the motor vehicle manufacturer’s facility.

The sludge’s status as a hazardous waste affects its accumulation and transport conditions.  If the sludge is F019 hazardous waste, the containers in which it is accumulated and transported are required to be kept closed, except when adding or removing waste.  Thus the open-topped roll off box would be covered once the final amount of sludge was placed in the box, and it would remain covered during transport.  However, if the sludge is not regulated as hazardous waste, the container may be kept uncovered during sludge accumulation and during transport (unless there are state, local or tribal requirements for it to be covered).

When the sludge arrives at the landfill it is placed into a specific area of the landfill that is in use at that time, called a “cell” (also referred to as a “unit” in regulatory language).  If the sludge is F019 hazardous waste, the landfill must have a permit to accept hazardous waste.  However, if the sludge is not regulated as hazardous waste, then the landfill would be subject to RCRA Subtitle D regulations, and any applicable state, local, or tribal regulations.  The landfill might accept municipal waste or nonhazardous industrial waste.  Generally these landfills have state permits, and if they accept municipal waste, in most instances they must also meet certain performance standards enumerated at Title 40, Code of Federal Regulations, Part 258, or the state’s corresponding regulations.

EPA interprets the F019 listing to apply to the final wastewater treatment solids, and to any other sludges from the wastewater treatment process that are combined with the final wastewater treatment solids, including grit that is removed in a preliminary wastewater treatment step.

3.  Identifying chemical constituents

The starting point for defining potential hazards is to identify the particular chemical constituents present in the waste, along with their known human health and ecological effects.

The production process and waste management practices that occur at the site of waste generation (the motor vehicle manufacturing plant) have an influence on the chemical composition of the waste.  One of the primary influences on the waste stream’s ultimate chemical composition is the conversion coating formulation’s composition.  Adjustments in quantities of chemical constituents present in the conversion coating formulation that is applied to the automobiles would affect the quantities of chemical constituents present in the wastewater treatment sludge.  Other facility-specific practices that would affect the identity and quantities of chemical constituents present in the wastewater, and thus the wastewater treatment sludge, include:

- whether or not the facility co-mingles other wastes with the conversion coating wastewater at the wastewater treatment facility

- activities at the plant’s wastewater treatment system (for example, changing the wastewater’s hydrogen ion potential, or pH, causes metal ions to precipitate out of the wastewater and into the sludge).

3.1   Material Safety Data Sheet review

Using Material Safety Data Sheets (MSDS) submitted to U.S. EPA from 1996 to 2002 in eleven F019 delisting petitions, we identify chemical constituents that we expect to be present in wastewater treated at motor vehicle manufacturing plants in the United States using zinc-phosphate conversion coating formulations on aluminum-and-steel vehicle bodies.  Table 1 lists the chemical constituents reported on more than three of the eleven facilities’ MSDS, along with their elemental composition, when known.  For three constituents (ethoxylated soya amine, alcohols C10-12, and alcohols C8-18, ethyoxylated propoxylated) we do not know the exact elemental composition.

Table 1.  Constituents likely to be present in motor vehicle manufacturing wastewater (zinc phosphate conversion coating)

Constituent	CAS#	Elements

acetic acid	64197	C	H	O

ethanol, 2-(2-butoxyethoxy)- 	112345	C	H	O

sodium carbonate	497198	C	Na	O

sodium gluconate	527071	C	H	Na	O

	calcium hydroxide	1305620	Ca	H	O

magnesium hydroxide	1309428	Mg	H	O

potassium hydroxide	1310583	K	H	O

sodium hydroxide	1310732	Na	O	H

ammonium bifluoride	1341497

H	N

sodium silicate	1344098	Na

O

hexanoic acid, 3,5,5-trimethyl	3302101	C	H	O

silicic acid, disodium salt	6834920	Na	Si	O

sodium tripolyphosphate	7758294	Na	O	P

sodium monohydrogen phosphate	7558794	H	O	Na	P

	sodium dihydrogenphosphate	7558807	H	O	Na	P

	trisodium phosphate	7601549	Na	O	P

silica	7631869	Si	O

	sodium nitrate	7631994	N	Na	O

sodium nitrite	7632000	N	Na	O

hydrochloric acid	7647010	H	Cl

	phosphoric acid	7664382	H	O	P

sulfuric acid	7664939	H	O	S

nitric acid	7697372	H	N	O

ferric chloride	7705080	Fe	Cl

	hydrogen peroxide	7722841	H	O

	tetrasodium pyrophosphate	7722885	Na	O	P

sodium tripolyphosphate	7758294	Na	O	P

tripotassium phosphate	7778532	K	O	P

phosphoric acid, monopotassium salt	7778770	H	K	O	P

	zinc nitrate	7779886	Zn	N	O

potassium acid fluoride	7789299	F	H	K

Poloxamer	9003116	C	H	O

polyethylene glycol dioleate	9005076	C	H	O

tergitol Np-40 (non-ionic)	9016459	C	H	O

Octyl phenol, ethylene oxide	9036195	C	H	O

phosphoric acid, manganese salt	10124546	H	O	P	Mn

	nitric acid, manganese (2+) salt	10377669	H	N	O	Mn

	phosphoric acid, nickel(2+) salt (2:3)	10381369	H	O	P	Ni

	nitric acid, Iron (3+) salt	10421484	Fe	N	O

nickel(II)nitrate	13138459	H	N	O	Ni

	chromium(III)nitrate	13548384	H	N	O	Cr

	phosphoric acid, zinc salt (2:1)	13598373	H	O	P	Zn

	potassium hexafluorotitanate	16919270	F	K	Ti

Poly(oxy-1,2-ethanediyl), alpha-(nonylphenol)-omega-hydroxy phosphate, potassium salt	52503158	C	H	O	P	K

ethoxylated soya amine	61791240	unknown

Alcohols C10-12	68154972	unknown

Alcohols, C8-18, ethoxylated propoxylated	69013189	unknown

Because they are present at three or more motor vehicle manufacturers’ facilities, we believe that the Table 1 chemical constituents are those most likely to be present in the initial wastewater stream entering motor vehicle manufacturers’ wastewater treatment facilities (although all of these constituents would not be found at all motor vehicle manufacturers’ facilities).  Other chemical constituents may also be present in a given manufacturer’s wastewater, but we believe the Table 1 constituents are likely to be found in most wastewater generated by motor vehicle manufacturers using the zinc phosphate conversion coating formulations.

3.2   Review of other contributing wastewaters

Information in some facilities’ delisting petitions indicates that those facilities co-mingle other wastewater streams with the wastewater from the conversion coating process.  Typically a motor vehicle facility undergoing annual cleaning and maintenance activities would flush wastewater from those activities into the wastewater treatment system.  In addition, some facilities operating boilers for space heating and/or process heat might flush boiler blowdown into the wastewater treatment system.  Some facilities might have storm water drainage patterns that allow storm water to enter the wastewater treatment system.  Some motor vehicle manufacturers’ facilities may use water in the vehicle painting process that ends up in the wastewater treatment system.

A review of eleven facilities’ (four different manufacturers’) delisting petitions indicated that boiler blowdown, cooling water, and factory cleanup water were co-mingled with process wastewater at three or more facilities out of the eleven.

3.3   Wastewater treatment and other process chemicals

A review of eleven facilities’ delisting petition information indicated that several facilities use substances of unknown composition during the wastewater treatment process.  Examples of substances mentioned in three or more facilities’ petitions include “polymer” and “filter aid.”  In addition, several facilities mention oil-based and water-based drawing lubricants.  We currently have no additional information on the chemical composition of these substances.

3.4   Transformation of constituents during wastewater treatment

One purpose of wastewater treatment is to separate the solid phase components from the water phase.  The separation is intended to capture in the solid phase those substances that may cause adverse effects on waterways and drinking water sources.  The separation process may include:

- physical separation steps

- chemical separation steps that add compounds that cause chemical reactions to occur and solids to settle out,

- biological separation steps that use microorganisms to change the chemical and/or biological composition of the wastewater, or

any combination of the three steps.

The solids form a watery mass at the bottom of the wastewater treatment units, and are removed periodically as wastewater treatment sludge.  The sludge composition may vary due to differences in wastewater treatment efficiency with different treatment techniques.

During the wastewater treatment process, many chemical reactions occur that would cause the constituents listed in Table 1 and other constituents in the sludge to transform into different compounds, or to break down into simpler molecules.  We expect that wastewater treatment sludge would be likely to contain the metals and metalloids that were present in the original wastewater, although once in the sludge they may be present in a form that is different from the specific chemical constituent listed on the MSDS.  We expect that the organic constituents that were present in the wastewater entering the wastewater treatment system may in some cases also be present in the sludge, while in other cases (depending on the specific treatment steps employed) may have been transformed into other compounds or may have evolved as gases and been released into the atmosphere.

3.5   Expected chemical composition of sludge

Reviewing the elemental composition of Table 1 constituents yields a list of metals and metalloids that are likely to be present in wastewater treatment sludges from this particular industry.  These metals and metalloids are calcium (Ca), chromium (Cr), iron (Fe), magnesium (Mg), manganese (Mn), nickel (Ni), potassium (K), silicon (Si), sodium (Na), titanium (Ti), and zinc (Zn).  Of these, calcium, iron, magnesium, potassium, silicon, and sodium are typically not considered to be of concern from an environmental standpoint, since they are so widely present in the environment, while chromium, manganese, nickel, titanium and zinc potentially would be of concern.  One non-metal element of possible concern that may also be present in the sludge is fluorine, expected to be present as fluoride.  The remaining non-metal elements likely to be present are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.  None of the non-metals are considered to be of concern in their elemental forms (although sulfur present as sulfide, and certain hydrocarbons, may be of concern).

In addition to these elements, the other co-mingled waste streams (such as boiler blowdown, cooling water, factory cleanup water) and other chemicals used at the facility (drawing lubricant, wastewater treatment chemicals) may contribute other elements or constituents that could be detected in the sludge.

3.6   Sampling data on chemical composition of sludge

Because a wide range of chemical constituents may be present in the sludge from motor vehicle manufacturing, a list of chemicals to look for when analyzing sludge samples could include all of the Table 1 chemical constituents and their expected breakdown (transformation) products, and other chemical constituents as well.  In order to keep analytical costs to a reasonable level, however, EPA Regions (and certain states) that accept petitions to delist a facility’s F019 motor vehicle manufacturing waste have developed lists of chemical constituents that could be expected to be present in the sludge.  Based on these lists, the facilities that have submitted delisting petitions have analyzed their sludge samples for a range of constituents, including most of the inorganic constituents of potential concern identified in section 3.5.  Exceptions are the metals titanium and manganese, and the ten organic (carbon-containing) chemical constituents listed in Table 1.

The F019 sludge sampling and analytical data for twelve facilities that submitted delisting petitions to EPA, and a thirteenth facility that submitted a draft delisting petition, are available in a spreadsheet and database format in the docket for this proposed rule.  The list of chemical constituents for which these facilities analyzed their sludge samples is shown in Table 2.

Table 2.  Chemical constituents analyzed in sludge from motor vehicle manufacturers

	Constituent	CAS#	Constituent	CAS#	Constituent	CAS#

	formaldehyde	50000	dichlorophenol, 2,6-	87650	triethylphosphorothioate, o,o,o-	126681

DDT	50293	hexachlorobutadiene	87683	methacrylonitrile	126987

benzo(a)pyrene	50328	pentachlorophenol	87865	chloro-1,3-butadiene, 2- 126998

dinitrophenol, 2-4-	51285	trichlorophenol, 2,4,6-	88062 tetrachloroethylene 	127184

famphur	52857	nitroaniline, 2-	88744	pyrene	129000

dibenz(a,h)anthracene	53703	nitrophenol, 2-	88755	naphthoquinone, 1,4- 130154

acetylaminofluorene, 2-	53963	butyl-4,6-dinitrophenol, 2-sec-	88857 dimethyl phthalate	131113

nitrosodiethylamine, n-	55185	naphthalene	91203	dibenzofuran	132649

carbon tetrachloride	56235	methylnaphthalene, 2-	91576	naphthylamine, 1- 134327

methylcholanthrene, 3-	56495	chloronaphthalene, 2-	91587	aramite	140578

benz(a)anthracene	56553	naphthylamine, 2-	91598	ethyl acetate	141786

nitroquinoline-1-oxide, 4-	56575	methapyrilene	91805	kepone	143500

cyanide	57125	dichlorobenzidine, 3,3'-	91941	dichloroethylene, cis-1,2- 156592

cyanide, (amenable)	57125	aminobiphenyl, 4-	92671	dichloroethylene, trans-1,2-	156605

cyanide, (complexed)	57125	trichlorophenoxypropionic acid, 2,4,5- 	93721 benzo(g,h,i)perylene	191242

cyanide, (reactive)	57125	trichlorophenoxyacetic acid, 2,4,5- 	93765 inden(1,2,3-cd)pyrene	193395

chlordane	57749	safrole	94597	benzo(b)fluoranthene	205992

dimethylbenz(a)anthracene, 7,12-	57976	dichlorophenoxyacetic acid, 2,4-  94757	fluoranthene	206440

hexachlorocyclohexane, gamma- 	58899	cresol, o- 	95487 benzo(k)fluoranthene	207089

tetrachlorophenol, 2,3,4,6-	58902	dichlorobenzene, 1,2-	95501 acenaphthylene	208968

chloro-3-methylphenol, 4- 	59507	toluidine, o-	95534	chrysene	218019

nitrosomorpholine, n-	59892	chlorophenol, 2-	95578	thionazin	297972

azobenzene, p-(dimethylamino)-	60117	tetrachlorobenzene, 1,2,4,5-	95943 disulfoton	298044

dimethoate	60515	trichlorophenol, 2,4,5-	95954	aldrin	309002

dieldrin	60571	dibromo-3-chloropropane, 1,2-	96128 hexachlorocyclohexane, alpha- 	319846

phenacetin	62442	trichloropropane, 1,2,3-	96184	hexachlorocyclohexane, beta- 	319857

ethyl methanesulfonate	62500	ethyl methacrylate	97632 hexachlorocyclohexane, delta- 	319868

aniline	62534	acetophenone	98862	isodrin	465736

nitrosodimethylamine, n-	62759	nitrobenzene	98953	chlorobenzilate	510156

benzoic acid	65850	nitroaniline, 3-	99092	methyl-4,6-dinitrophenol, 2- 534521

methyl methanesulfonate	66273	trinitrobenzene, sym-	99354 dichloroethylene, 1,2-	540590

methanol	67561	nitro-o-toluidine, 5-	99558	dichlorobenzene, 1,3-	541731

acetone	67641	dinitrobenzene, m- 	99650	methyl tert butyl ketone	591786

chloroform	67663	nitroaniline, 4-	100016	dinitrotoluene, 2,6-	606202

hexachloroethane	67721	nitrophenol, 4-	100027	pentachlorobenzene	608935

hexachlorophene	70304	ethylbenzene	100414	nitrosodipropylamine, n- 621647

butanol, n-	71363	styrene	100425	tetrachloroethane, 1,1,1,2-	630206

benzene	71432	benzyl alcohol	100516	nitrosodi-n-butylamine, n-	924163

trichloroethane, 1,1,1-	71556	nitrosopiperdine, n-	100754 nitrosopyrrolidine, n-	930552

endrin	72208	bromophenyl phenyl ether, 4-	101553	heptachlor epoxide 1024573

methoxychlor	72435	dimethylphenol, 2,4-	105679	endosulfan sulfate 1031078

DDD	72548	cresol, p-	106445	cresols, m- & p-	1319773

DDE	72559	dichlorobenzene, 1,4-	106467	xylenes	1330207

bromomethane	74839	chloroaniline, 4-	106478	polychlorinated biphenyls 1336363

methyl chloride (chloromethane) 	74873	phenylenediamine, p-	106503 hexachloropropene	1888717

iodomethane	74884	dibromoethane, 1,2-	106934	diallate	2303164

dibromomethane	74953	acrolein	107028	tetraethyl dithiopyrophosphate  3689245

chloroethane	75003	allyl chloride	107051	chlorophenyl phenyl ether, 4- 7005723

vinyl chloride	75014	dichloroethane, 1,2-	107062	endrin aldehyde	7421934

acetonitrile	75058	propionitrile (ethyl cyanide)	107120	lead	7439921

methylene chloride	75092	acrylonitrile	107131	mercury	7439976

carbon disulfide	75150	vinyl acetate	108054	nickel	7440020

bromoform	75252	methyl isobutyl ketone 	108101	silver	7440224

bromodichloromethane	75274	cresol, m- (3-methylphenol)	108394	thallium 7440280

dichloroethane, 1,1-	75343	bis(2-chloro-methylethyl) ether	108601	tin 7440315

dichloroethylene, 1,1-	75354	toluene	108883	antimony	7440360

trichlorofluoromethane	75694	chlorobenzene	108907	arsenic	7440382

dichlorodifluoromethane	75718	phenol	108952	barium	7440393

pentachloroethane	76017	picoline, 2-	109068	beryllium	7440417

heptachlor	76448	dichloro-2-butene, trans-1,4-	110576	cadmium	7440439

hexachlorocyclopentadiene	77474	chloroethyl vinyl ether, 2-	110758 chromium	7440473

isophorone	78591	pyridine	110861	cobalt	7440484

isobutanol	78831	bis(2-chloroethyl) ether	111444	copper	7440508

dichloropropane, 1,2-	78875	bis(2-chloroethoxy) methane	111911	vanadium 7440622

methyl ethyl ketone (2-butanone)	78933	endosulfan I	115297	zinc	7440666

trichloroethane, 1,1,2-	79005	bis(2-ethylhexyl) phthalate	117817 selenium	7782492

trichloroethylene	79016	di-n-octyl phthalate	117840	toxaphene	8001352

acrylamide	79061	hexachlorobenzene	118741	dichloropropene, cis-1,3- 10061015

tetrachloroethane, 1,1,2,2-	79345	dimethylbenzidine, 3,3'-	119937 dichloropropene, trans-1,3-	10061026

methyl methacrylate	80626	anthracene	120127	nitrosomethylethylamine, n- 10595956

pentachloronitrobenzene	82688	isosafrole	120581	fluoride	16984488

acenaphthene	83329	trichlorobenzene, 1,2,4-	120821	sulfide, (reactive) 18496258

diethyl phthalate	84662	dichlorophenol, 2,4-	120832	sulfide	18496258

di-n-butyl phthalate	84742	dinitrotoluene, 2,4-	121142	hexavalent chromium	18540299

phenanthrene	85018	dimethylphenethylamine, a,a-	122098	pronamide 23950585

butyl benzyl phthalate	85687	diphenylamine	122394	endosulfan II	33213659

nitrosodiphenylamine, n-	86306	dioxane, 1,4-	123911

fluorene	86737	dibromochloromethane	124481

The data include sludge samples that were analyzed as either “totals” or “leachate” samples.  “Totals” samples are analyzed in their entirety.  That is, the solids and liquids present in the sludge sample are prepared for analysis and analyzed for their total content of a particular chemical constituent.  “Leachate” samples consist of only a portion of the sludge sample.  To create a leachate sample, the laboratory analyst processes the sludge sample using the Toxicity Characteristic Leaching Procedure (TCLP), a method designed to imitate the conditions the waste would undergo when disposed at a municipal solid waste landfill.  The processing produces a liquid portion that we expect would be similar in composition to the leachate leaving the landfill and entering the soil and groundwater underneath the landfill.  Both types of samples provide information needed to evaluate how much of a particular chemical constituent is present in the waste and how it is likely to move in the environment once it is released from the landfill.

Table 3 shows the chemical constituents that facilities detected at levels above the quantitation limit of the instruments used, in descending order of frequency of detection in totals samples and leachate samples.

Table 3.  Chemical constituents detected in sludge from motor vehicle manufacturers

	Constituent	CAS#	% of totals samples	% of leachate samples

	Detected in both totals and leachate samples:

nickel	7440020	100	100

fluoride	16984488	100	100

zinc	7440666	100	99

barium	7440393	100	90

copper	7440508	100	83

chromium	7440473	100	55

tin	7440315	99	81

formaldehyde	50000	97	97

lead	7439921	89	38

cobalt	7440484	81	81

mercury	7439976	80	4

sulfide	18496258	80	62

xylenes	1330207	76	33

vanadium	7440622	61	38

arsenic	7440382	56	55

cyanide	57125	50	17

ethylbenzene	100414	56	41

hexavalent chromium	18540299	52	14

toluene	108883	49	17

butanol, n-	71363	49	31

acrylamide	79061	46	22

cadmium	7440439	39	27

bis(2-ethylhexyl) phthalate	117817	31	3

antimony	7440360	28	35

methyl ethyl ketone 	78933	26	8

beryllium	7440417	23	6

selenium	7782492	22	41

silver	7440224	19	31

thallium	7440280	13	25

butyl benzyl phthalate	85687	10	10

naphthalene	91203	8	29

cresol, p- 	106445	7	73

acetone	67641	7	54

trichloroethylene	79016	6	2

dichloroethane, 1,2-	107062	5	1

acetonitrile	75058	3	5

chlorobenzene	108907	1	3

methylene chloride	75092	1	7

trichloroethane, 1,1,1-	71556	1	1

dichloroethane, 1,1-	75343	1	1

	Table 3 (cont.).  Chemical constituents detected in sludge from motor vehicle manufacturers

	Constituent	CAS#	% of totals samples	% of leachate samples

	Detected only in "totals" samples (not in leachate samples):

di-n-octyl phthalate	117840	23

	methyl isobutyl ketone	108101	10

	tetrachloroethylene 	127184	8

	styrene	100425	7

	acrolein	107028	7

	dichloroethylene, cis-1,2-	156592	6

	methyl chloride	74873	4

	carbon disulfide	75150	4

	chloroform	67663	2

	benzene	71432	1

	allyl chloride	107051	1

	Detected only in leachate samples (not in "totals" samples):

phenol	108952

53

acetophenone	98862

11

cresol, o-	95487

7

cresol, m- 	108394

7

di-n-butyl phthalate	84742

4

Note that several organic chemical constituents are found in more than 30% of the totals samples (formaldehyde, n-butanol, acrylamide, ethylbenzene, toluene and xylenes).  The data in Table 1 do not suggest that these would be found in either the wastewater or the sludge (except possibly formaldehyde, which might occur as a breakdown or transformation constituent from more complex hydrocarbons).  It seems likely that n-butanol, ethylbenzene, toluene, xylenes, and possibly formaldehyde are present due to other operations at the facilities.  For example, they may arise from painting operations that occur after the motor vehicle bodies are conversion-coated.  The acrylamide is likely to be a result of wastewater treatment activities (acrylamide polymers are sometimes added to wastewater as flocculating agents).   In addition, certain constituents that would not be expected to be present are reported as present, possibly due to contamination in either the sampling or laboratory processes used (for example, phthalates are common laboratory contaminants).

Note also that several metals and metalloids are found in more than 30% of the samples (lead, mercury, tin, arsenic, barium, cadmium, chromium, cobalt, copper and vanadium); we would not expect to find these constituents from a review of Table 1.  It seems likely that these constituents could be present in water used in the conversion coating baths, in the motor vehicle bodies (in solders, or in the steel or aluminum) or in co-mingled boiler blowdown water, cooling water, and factory clean-up water in the wastewater collection and treatment system.  Cyanide compounds and sulfide are found in more than 30% of samples as well.  Fluoride is found in 100% of totals samples.

In 2000, the Aluminum Association submitted to EPA analytical sampling data from 39 automotive assembly plants, including 23 performing conversion coating on steel-only vehicle bodies, and 16 performing conversion coating on steel-plus-aluminum vehicle bodies.  The data set did not identify the samples taken from plants performing steel-only conversion coating vs. steel-plus-aluminum conversion coating.  In addition, the Aluminum Association did not provide documentation on the conditions under which the samples were taken, laboratory analytical information, quality control, and quality assurance measures taken during both the sampling and the laboratory analyses.  Thus, we concluded that we could not rely on these data to indicate the identity or levels of constituents in the waste.  These data are available in the docket for review and inspection.

The 56 constituents in Table 3, identified in the delisting petition and verification sampling from thirteen motor vehicle manufacturers’ facilities, form the basis for the risk assessment results described in Sections 5, 6 and 7.

4.  Exposure and Risk Assessment

People and ecological “receptors” (plants, animals, insects, and other living organisms such as soil microorganisms) might be exposed to chemical constituents that are present in the F019 waste.  People can be exposed to the chemical constituents in the waste while it is accumulated at the manufacturing plant, while it is transported to the landfill, as it is being placed in the landfill, or when it is released from the landfill.  Releases from landfills generally happen over long periods of time.  However, unusual weather conditions such as major floods can cause wastes and waste constituents to be released from the landfill rapidly.  Ecological receptors generally could only be exposed to the chemical constituents in the waste as it is being placed in the landfill, or when it is released from the landfill, unless they use the landfill as habitat.

Assessments of potential risk due to environmental exposures performed to support EPA’s regulatory decisions typically consist of several steps:

1) Identifying the likelihood that people or ecological receptors may experience a particular exposure due to an activity such as a release of a hazardous chemical constituent into the environment;

2) Evaluating the potential hazard(s) posed by the chemical constituent, by identifying the chemical constituents of potential concern, and their health effects; and

3) Combining the potential for people or ecological receptors to come into contact with the chemical constituent, at the levels (or doses) that are estimated to occur under various conditions, and calculating the potential for adverse health effects that corresponds to those doses.

Sections 4.1 to 4.3 describe how we perform the first step listed above qualitatively: identifying the potential for environmental exposures to chemical constituents in the F019 waste from motor vehicle manufacturers.  Section 3 describes the second step, identifying the chemical constituents of potential concern; some of the references listed at the end of this document describe the constituents’ health effects.  Section 4.4 describes the mathematical models we use to perform the first and third steps quantitatively.  Sections 5, 6, 7 and 8 describe our use of the models and their results, as we perform the second and third steps quantitatively.

The US Department of Labor’s Occupational Safety and Health Administration (OSHA) and the corresponding state government occupational safety and health agencies enforce worker training and other requirements intended to protect workers from workplace hazards.  We assume that the motor vehicle manufacturing plant workers who handle the sludge, transportation workers, and landfill workers are covered by worker protection requirements, and that those requirements protect the workers’ health and safety.  The RCRA hazardous waste characteristics regulations which focus on acute hazards (ignitability, corrosivity and reactivity; see 40 CFR 261.21-261.23) address risks to workers handling wastes.  However, for hazardous waste listing determinations, EPA has usually not evaluated risks to workers from chronic exposures to toxic constituents present in wastes.  Thus we exclude workers from the description of possible human exposures in section 4.1 since no acute hazards appear to exist, and we typically assume that the worker protection requirements address chronic exposures to toxic constituents present in wastes.

4.1   Human activities

4.1.1   Waste accumulation practices

The F019 wastewater treatment sludge is currently regulated as a hazardous waste, unless that facility’s sludge has been “delisted.” See the discussion in the preamble of the Federal Register notice proposing the regulatory amendment.  As a hazardous waste, the sludge must be stored in covered containers (except when adding or removing sludge), or in tanks, and other requirements apply as well.

If the F019 wastewater treatment sludge is reclassified as nonhazardous waste, the motor vehicle manufacturers could accumulate it in uncovered piles directly on the ground, or in uncovered containers or tanks, unless state or local requirements prevent that kind of management practice.  Depending on the distance between their residences and the sludge handling and accumulation areas, nearby residents could be exposed to the chemical constituents in the F019 waste while it is being accumulated.

We do not evaluate the potential risk from environmental exposures that may be experienced by residents near the manufacturing plant where the sludge is generated, since we don’t know the exact locations of the wastewater treatment and sludge storage operations at the manufacturing plants and the distance and direction to nearby residences.  However, these sludges, which are generated from wastewater treatment and have relatively high moisture content, are unlikely to produce particulate releases.   Generators who submitted delisting petitions also indicated that they typically store dewatered sludges in containers or bins prior to shipment offsite for disposal.   In addition, regulatory controls under the Clean Air Act (and state or local restrictions on air releases) are designed to address potential air releases from manufacturing facilities.  Finally, we assume that local zoning ordinances would provide an adequate buffer zone between the manufacturing plant property and nearby residences, so that any windborne dried sludge particles and volatilized gases from the sludge accumulation would be negligible at the residences.

4.1.2   Waste transport practices

If the F019 continues to be classified as hazardous waste, the waste must be transported in a vehicle that meets US Department of Transportation (DOT) requirements for hazardous materials transport.  If the F019 is reclassified as nonhazardous waste, the waste could be transported in a vehicle that may or may not meet the DOT requirements.  Whether or not the vehicle would be required to meet DOT requirements would depend on whether the sludge would still be classified as a hazardous material under DOT requirements, and whether the sludge was destined for an out-of-state landfill.

People who live along the vehicle’s route, from the manufacturing plant to the landfill, would be likely to have different levels of exposure depending primarily on the vehicle’s travel speed.  Also, in the event of a roadway or rail crash, people near the crash site could be exposed to volatile gases or particulates released from the sludge while the vehicle was stopped, and spilled sludge might be released from the vehicle.

We do not evaluate the potential risk from environmental exposures that may be experienced by people living along the transport route from the manufacturing plant to the landfill site.  Such exposures would be intermittent and could vary if transport routes change.  We are assuming that prudent transporters would cover their waste loads to prevent dust and nuisance complaints, even if there was no state or federal requirement to do so, and would take measures to minimize leakage (dripping) of the waste load.  Furthermore, transport costs are typically based on the dewatered sludge’s weight, so we believe generators have an incentive to keep containers covered or indoors prior to shipment to prevent precipitation from entering the container.  To the extent that containers may not be covered, omitting this potential exposure leaves a gap in our understanding of the potential risks from managing these wastes.

4.1.3   Waste placement in landfill

If the F019 continues to be classified as hazardous waste, the waste must be disposed in a permitted hazardous waste landfill.  If the F019 is reclassified as nonhazardous waste, the waste could be disposed in a “Subtitle D” landfill that must have a cover placed over the waste at the end of each day, and meet certain other requirements.

Nearby residents could be exposed to chemical constituents during waste placement in a landfill.  They could be exposed to volatile gases emitted from the sludge, as well as windblown dried sludge particles.  They would be unlikely to experience direct skin contact with the sludge.

4.1.4   Waste release from landfill

Nearby residents could breathe volatile gases from sludge that was disposed of previously.  We expect that breathing volatile gases from sludge disposed of previously is somewhat less likely for residents near landfills that use a landfill gas collection system than for residents near landfills that do not use a landfill gas collection system.  A continuously operating landfill gas collection system would cause the landfill to be under negative pressure compared to local atmospheric pressure, and volatile chemical constituents would be collected in a pipe system (usually to be combusted for energy recovery purposes) rather than dispersed into the surrounding atmosphere.  A landfill gas collection system that operates intermittently (for example, due to frequent equipment breakdowns) would experience pressure fluctuations relative to local atmospheric pressure and might result in nearby residents’ exposures that are similar to a landfill that operates without any landfill gas collection system at all.

Nearby residents would be unlikely to be exposed to windblown dried sludge particles from previously disposed sludge unless significant erosion of the landfill’s cover occurred.  In the near-term timeframe, such exposure would be unlikely for landfills containing municipal solid waste, due to the criteria at 40 CFR 258.21 requiring landfill operators to apply a cover of "earthen material" at the end of each day’s operations.   For non-municipal solid waste landfills ("industrial landfills"), federal regulations are limited.  Instead, there are classification criteria at 40 CFR Part 257 that presume a facility poses a reasonable probability of adverse effects on health or the environment, unless they periodically apply cover material to control disease vectors (257.3-6) or for other safety reasons (257.3-8).  Facilities that fail to satisfy these criteria are considered "open dumps", which are prohibited under section 4005 of RCRA (see 40 CFR Section 257.1(a)(1)).  In addition, states typically have regulations in place for industrial landfills and require operating permits (ASTSWMO 1996).

Nearby residents would be unlikely to have direct skin contact with previously disposed sludge unless there was a catastrophic release such as from a flood.

Nearby residents could be exposed to chemical constituents from the sludge that have entered groundwater underneath the landfill, if the groundwater moves toward the residents’ water wells and the residents use the water for drinking, bathing and/or showering.

Nearby residents also could be exposed if volatile constituents from the previously disposed sludge attach to windblown dust and fall onto soil, gardens or cropland, and the residents inadvertently ingest the soil and eat the garden produce or crops.

4.2   Ecological receptor activities

4.2.1   Waste accumulation practices

During waste accumulation, we believe that ecological receptors likely would have little to no exposure to the chemical constituents in the F019 waste.  We anticipate that the motor vehicle manufacturing facility consists of paved areas with little vegetation, and storm water may drain into the wastewater treatment facility.  In the event storm water drains directly to nearby waterways, ecological receptors could be exposed from precipitation coming into contact with accumulating sludge and draining off, carrying chemical constituents into nearby waterways.  We do not have any information at this time indicating that this scenario is likely to occur.

4.2.2   Waste placement in landfill

Ecological receptors could be exposed to chemical constituents during waste placement in the landfill.  Essentially all organisms in the nearby vicinity that are downwind of the waste placement area could experience exposures to the volatile gases emitted from

the sludge during waste placement.  There may be some exposure of birds and rodents/small mammals to the waste.  However, landfills generally require operators to cover disposed solid waste daily, or at more frequent intervals if necessary to control disease vectors, fires, odors, blowing litter, and scavenging (40 CFR 258.21).  In addition, municipal landfill units must control on-site populations of disease vectors (rodents, insects, and other animals; see 40 CFR 258.22).

4.2.3   Waste release from landfill

Ecological receptors could be exposed to chemical constituents during waste release from the landfill.  Previously-disposed F019 sludge would continue to emit volatile gases for a period of time, and downwind ecological receptors could be exposed to those chemical constituents.  Precipitation that falls on the landfill and drains through the entire landfill, picking up chemical constituents from the waste in the landfill, and then enters the groundwater, eventually may flow into a nearby body of surface water such as a stream or river.  Aquatic organisms in the nearby surface water could then be exposed directly to the chemical constituents, or exposed due to buildup of the chemical constituents in sediments and aquatic organisms that are then consumed by higher-level aquatic organisms.

4.3   Summary of Potential Exposures Assessed

Managing the F019 wastewater treatment sludge from chemical conversion coating of motor vehicles creates some potential exposures for people and ecological receptors.  As described above, the initial sludge accumulation creates some potential for exposure by nearby residents, and nearby stream-dwellers, while sludge transport creates some potential for exposure for residents along the transport route, and disposal creates some potential for exposure by residents living near the landfill and nearby stream-dwellers.  In this analysis, we assess the potential for adverse effects from the landfill activities.  We have estimated the potential risks from environmental exposures that may be experienced by people living near the landfills, and by ecological receptors, both during waste placement and upon release over time from the landfill.

4.4   Fate, Transport, Exposure, and Risk Modeling

4.4.1   Overall methodology for this risk assessment

This risk assessment’s overall methodology evaluates the potential for adverse human health and environmental effects due to exposure to the 56 chemical constituents shown in Table 3.  These 56 chemical constituents exist in a particular chemical structure for a certain period of time after disposal in the landfill.  However, eventually, due to interaction with water or with other chemical constituents, exposure to radiation or light energy, or temperature changes, the chemical constituents change into other forms (their “fate”).  A “fate and transport” model uses variables that represent the many influences on a chemical constituent

as it exists initially in the environment,

as it moves through the environment as a result of those influences, and

as it eventually changes into another form.

The input to a fate and transport model is a specific quantity of a chemical constituent that is released into the environment from a source.  The output from a fate and transport model is an estimate (or a distribution of estimates) of how much of the released quantity of that chemical constituent exists at a specific place, at a specific point in time.

Exposure models use the fate and transport model outputs, and combine them with information on “receptors” to develop estimates of receptors’ exposures to that chemical constituent.  Risk models take the exposure model estimates to develop estimates of potential adverse health effects that may result from those estimated exposures.  Often, exposure and risk equations are combined together in the same model.  Sometimes a model contains fate, transport, exposure and risk equations all in one model (or in separate model components that are linked together).

Because the 56 chemical constituents in Table 3 have different environmental fate and transport patterns, and different toxicities, due to their different physical and chemical characteristics, we need to screen them using a tool that shows the likely transport routes that they will follow, and to identify which ones are more likely to present health risks of concern.  This screening consists of a primary analysis of an unlined landfill scenario to estimate the possible exposures that residents near that landfill, and organisms in a nearby stream, might receive from each of those 56 chemical constituents.  The model we use tracks movement of constituents either through the air, into groundwater, or via precipitation runoff into surface water.  Thus it serves to screen the constituents by identifying where they are most likely to move, once disposed into the landfill, and to indicate which ones are more likely to possibly cause adverse effects.  However, it only models an unlined landfill scenario.

We perform an additional analysis of a lined landfill scenario, in which we model disposal into a landfill that is designed and built with technologies intended to contain or reduce emissions (such as landfill gas collection systems, liners, leachate collection systems, and covers).  This additional analysis also allows for the comparison of different liner designs.  For movement into groundwater, those constituents that do not appear to present a problem in the primary screening analysis of the unlined landfill scenario are less likely to move away from the landfill if it is designed and constructed with emission-reducing technologies.  In the additional analysis, we focus on the smaller number of chemical constituents which the primary screening analysis indicated are more likely to potentially cause adverse health effects.  The additional analysis evaluates the effectiveness of landfill liners in containing leachate (and thus reducing potential human exposures from contact with contaminated groundwater).  However, it only models movement (and resulting potential exposure) via the groundwater pathway.

We use three models in this risk assessment.  For the primary screening analysis of the unlined landfill scenario, we use

the Delisting Risk Assessment Software, version 2.0 (DRASv2)

 For the additional analysis of the lined landfill scenario, we use

the Industrial Waste Management Evaluation Model (IWEM)

For the DRASv2 model and the IWEM model, the underlying fate and transport equations for the movement of constituents in groundwater underneath the landfill is

the EPA Composite Model for Leachate Migration with Transformation Products (EPACMTP)

We also used EPACMTP in a related analysis (the Dyes and Pigments listing determination rulemaking risk assessment, described in more detail in section 5).

We describe each model in the sections below, with references to the user’s guides and technical background documents.  Appendix A lists the main assumptions the model developers made when they decided how to represent the landfill and its releases to the environment.

Finally, it is important to understand what each model provides as risk estimate outputs.  Due to variability in natural systems (for example, differences in ages, sizes, and genetic makeup among humans, or the wide ranges of environmental conditions across the United States) the “true” hazard or risk posed by disposing of F019 from motor vehicle manufacturers in U.S. landfills is itself a range of values.  We call this range of hazard or risk estimate values the “risk distribution.”  Models can estimate hazard or risk at a given point somewhere on this distribution, or they can be set up to provide outputs that are themselves distributions of hazard or risk estimates.  We call models that give risk outputs that are single-point estimates “deterministic,” and those that give outputs that are distributions of estimates “probabilistic.”  The difference between deterministic model outputs and probabilistic model outputs results from the way that the models try to represent reality – either with a single point value for a given variable (deterministic), or by running many times sequentially, and selecting variable values from a model input distribution of data points for that variable, on a probabilistic basis (probabilistic).

DRASv2 and IWEM both provide single-point estimates of risk that correspond to a particular chemical constituent concentration in waste.  In contrast, EPACMTP was designed to be run as a probabilistic model that provides as its output a distribution of groundwater concentrations (that can then be used directly as input to a probabilistic risk model, or a particular point estimate from the distribution can be used as an input to a deterministic risk model).  Both DRASv2 and IWEM take advantage of the EPACMTP probabilistic format, by selecting a single point estimate (the 90th percentile estimated chemical constituent concentration at the drinking water well) from the EPACMTP distribution of groundwater concentrations to use in an input in the deterministic DRASv2 or IWEM risk model, in order to develop single-point deterministic risk estimates.

4.4.2   Delisting Risk Assessment Software, version 2.0

We use DRASv2 for the primary screening analysis of disposal in an unlined landfill.  This model assesses potential human health risk or hazards from many possible pathways by which the 56 chemical constituents in Table 3 might move through the environment.  DRASv2 models movement of leachate from the waste, into the soil and groundwater underneath the landfill, where constituents present in the leachate mix with the groundwater.  DRASv2 also models the constituents in the waste that become airborne, or are carried away from the landfill by precipitation, during the process of placing the waste into the landfill.

For movement in groundwater, DRASv2 models the constituents that are present in the waste leachate that has mixed with the groundwater underneath the landfill.  DRASv2 models the leachate/groundwater mixture underneath the landfill as it moves toward a hypothetical residential groundwater well that is located in the direction toward which the groundwater would flow (“downgradient”).  If such a well is used at a future point in time, when the constituents that were in the waste have moved via the groundwater into the zone from which the well draws its water, people using the well could be exposed to constituents from the waste in the landfill when they use the groundwater for drinking, bathing, and/or showering.  People could ingest constituents by drinking the groundwater directly, or could be exposed to constituents by getting them on their skin while bathing or showering with the groundwater.  Some, but not all, of the constituents could become volatile (gaseous) when heated, and so heating the groundwater and using it for bathing/showering purposes may cause volatilized constituents to be released into the house’s interior when the groundwater comes out of a bath faucet or showerhead.  For these volatilizing constituents, people would be exposed to them by breathing the air in the bath or shower enclosure during the bath or shower, and also would be exposed to lower levels of volatilized constituents while they are in other parts of the residence.

For movement in air, or movement by being carried away from the landfill by precipitation runoff, DRASv2 models “surface pathways” (so-called because the movement occurs above the land surface rather than in groundwater).  DRASv2 models three surface pathways by which people would be exposed to constituents from the waste: 1) direct air inhalation (breathing either particles that contain waste constituents, or volatilized constituents from the waste by being downwind of the landfill when the waste is being placed into the landfill), 2) soil ingestion (ingesting soil that is contaminated with constituents from the waste that moved by wind currents and were deposited on the soil in the yard of a downwind residence), and 3) surface water ingestion/ingestion of fish.  This third pathway, surface water ingestion/ingestion of fish, occurs as a result of precipitation that comes into contact with the waste when it is deposited into the landfill, washes some of the constituents out of the waste and carries them with the precipitation run-off to a nearby, downhill stream (surface water body).  For this pathway, people would be exposed to the constituents from the waste in two ways: by drinking the surface water directly, and by ingesting fish that have absorbed the constituents once they entered the surface water body.

The DRASv2 model assesses potential ecological hazards to aquatic organisms in a freshwater surface water body.  DRASv2 models the constituents’ movement as a result of precipitation that comes into contact with the waste when it is deposited into the landfill, washes some of the constituents out of the waste and carries them with the precipitation run-off to a nearby, downhill stream (surface water body).

Table 4 shows the environmental media, exposure routes, receptors, and receptor activities/behaviors that DRASv2 models:

	(

soil intake²

surface water	Ingestion	(

	drinking

surface water	Ingestion	(

	eating fish

surface water	ingestion/dermal

	(	habitat use

	Note 1: DRASv2 models cancer risk for a child age 0-6 who is modeled further as an adult age 7-30.  DRASv2

does not model noncancer effects for children via groundwater ingestion (see discussion in section 5).

	Note 2: Some adults and some children ingest soil inadvertently only.  Some adults and some children ingest

  soil inadvertently, and also ingest it intentionally.  See EPA 1997b and EPA 2002b for further

  descriptions of soil ingestion behaviors.

Note that in using DRASv2, EPA has identified certain problems and is developing version 3 to address these known problems. Version 2 can still be used for its intended purpose by user over-rides.  In this risk assessment, we perform all DRASv2 modeling in the forward-calculation mode.

EPA 2002a in the references list is the model documentation and user’s guide for DRASv2; it describes the assumptions underlying the model in considerable detail.  Appendix A excerpts and paraphrases descriptions of model assumptions from EPA2002a.

4.4.3   Industrial Waste Management Evaluation Model

For the additional analysis, of the scenario of disposal in a lined landfill, we use the Industrial Waste Management Evaluation Model, or IWEM (see EPA 2002c and EPA 2002d for user’s guide and model documentation).  IWEM has three different tiers, or levels of complexity; we use Tier 1.

IWEM assesses potential human health risk or hazards from groundwater pathways only (a companion model, IWAIR, assesses risk or hazards from air pathways.  Since the primary, screening analysis showed all potential risks or hazards to be from groundwater pathways, we did not evaluate air or surface water pathways in the additional analysis.)

Similar to DRASv2, IWEM models movement of leachate from the waste, into the soil and groundwater underneath the landfill, where constituents present in the leachate mix with the groundwater, as it moves toward a hypothetical residential groundwater well that is located in the direction toward which the groundwater would flow (“downgradient”).

IWEM models the ingestion of groundwater as drinking water, and inhalation of volatile constituents from groundwater during showering (that DRASv2 also models).  However, IWEM does not model dermal exposure from bathing/showering.

Table 5 shows the two groundwater exposure routes, receptors, and receptor activities/behaviors that IWEM models for noncancer effects:

Table 5.  IWEM exposure routes, receptors and activities (noncancer)

	Exposure Route	Receptors	Receptor Activity

 	Adult	Child

	ingestion

(	drinking

inhalation	((

showering

	Note 1: IWEM compares the estimated air concentration (from showering) to a reference

    air concentration that should protect children as well as adults

    (see EPA 2002d, p. 5-11).

Here are the two groundwater exposure routes, receptors, and receptor activities/behaviors that IWEM models for cancer risk:

Table 6.  IWEM exposure routes, receptors and activities (cancer)

	Exposure Route	Receptors	Receptor Activity

 	Adult	Child

	ingestion	((	((	drinking

inhalation	(

showering

	Note 1: The modeled individual is a child/adult age 0-29.

EPA 2002c and EPA2002d in the references list are the model user’s guide and model documentation, respectively, for IWEM.  Both documents describe the assumptions underlying the model.  Appendix A excerpts and paraphrases descriptions of some of the main model assumptions from EPA 2002c and EPA 2002d.

4.4.4   EPA’s Composite Model for Leachate Migration with Transformation Products

The last model that we use is EPACMTP (EPA's Composite Model for Leachate Migration with Transformation Products) (see EPA 1997a, EPA 2003a, and EPA 2003b for model documentation and user’s guide).  DRASv2 and IWEM use different versions of EPACMTP for the groundwater fate and transport of the chemical constituents disposed in the modeled landfills (DRASv2 uses the 1996/1997 version, while IWEM uses the 2002/2003 version, or version 2.0).

EPACMTP models only fate and transport of the chemical constituents underneath the landfill (in the unsaturated zone, it models vertical (downward) movement; in the saturated zone, or aquifer, it models movement in three dimensions).  Thus we cannot use EPACMTP by itself to develop estimates of human health or environmental effects.  However, EPACMTP is important to this analysis because it models the constituents’ movement in the subsurface in both of the other models that we use (DRASv2 and IWEM).

Appendix A includes many of the modeling assumptions in EPACMTP in the descriptions excerpted from the DRASv2 and IWEM model documentation.

4.4.5   Peer review of models

Each of these models has been peer reviewed, at a minimum with an internal EPA peer review:

- U.S. EPA’s Region 6 Delisting Program, Multimedia Planning and Permitting Division developed the DRAS software program (version 2).  Region 6 provided a beta test version to EPA Regions and EPA headquarters staff in September 1999. EPA’s Office of Research and Development (ORD) provided internal peer review comments during the fall of 1999.  One external (to EPA) reviewer provided review comments on one aspect of the approach used in DRAS that affects the groundwater pathway results.  Region 6 completed a Response to Comments package on Regional, Office of Solid Waste (OSW) and ORD comments in June 2000. Region 6 revised the software code and the technical documentation in response to Regional, OSW, and ORD comments.

- IWEM was developed by U.S. EPA Office of Solid Waste staff.  EPA held an external peer review on a 1999 draft version of IWEM.  The peer review summaries and individual peer review comments are available in the electronic docket for the federal government at http://www.regulations.gov, under docket identification number EPA-HQ-RCRA-1999-0032, document identification number EPA-HQ-RCRA-1999-0032-0017 (in .tif and .pdf format) in the docket for an October 8, 1999 Notice of availability (Volume 64 FR No. 195, pp. 54889-54890).

- EPACMTP and its predecessors has been peer reviewed on numerous occasions.  For example, in 1995, EPA’s Science Advisory Board reviewed the version that was available at that point in time.  Version 2.0, developed in 2002, was a submodel of a model called “3MRA” that was reviewed by EPA’s Science Advisory Board (see EPA 2004a).  The dyes and pigments listing determination risk assessment (EPA 2003c) also uses the EPACMTP model (version 2.0).

5.  Potential noncancer hazard to humans

In order to determine whether there is a potential noncancer hazard from constituents present in the waste, we use a criterion, or guideline, of what an acceptable exposure is.  The acceptable exposure that we use in this analysis is, in most cases, the Reference Dose (RfD) or Reference Concentration (RfC) from an EPA database of toxicity information (EPA 2005c).   The RfD or RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious effects during a lifetime.  In mathematical terms, we represent this as the ratio of a person’s modeled, or estimated, daily exposure to a particular constituent to the estimate of that person’s exposure that should be likely to be without an appreciable risk of deleterious effects during a lifetime.  We call the ratio the “hazard quotient.”

If the estimated daily exposure is greater than the exposure that should be without risk of deleterious effects, then the hazard quotient is greater than one.  If the estimated daily exposure is less than the exposure that should be without risk of deleterious effects, then the hazard quotient is less than one.  We use the hazard quotient calculation to sort out those constituent exposures that are unlikely to be of concern from those constituent exposures that could potentially pose concerns.  Because of uncertainties that are inherent in the data that EPA uses to develop acceptable exposure levels, a hazard quotient greater than one does not necessarily mean that the individual’s exposure will result in adverse health effects.

To be more certain that we do not ignore exposures of potential concern, we use an initial criterion of a hazard quotient of one-tenth (0.1), so that our first step captures the exposures that are most likely to be within the range of concern.  Our initial calculations are to develop the high end estimates of exposures – in other words, those exposures that might occur at the high end of the range of circumstances that could occur, or the high end of the risk distribution.  We first develop high end hazard quotient estimates for all of the 56 constituents that we are able to evaluate, and compare those high end estimates to the hazard quotient level of 0.1.  Then we evaluate further those constituents whose estimated high end hazard quotients are greater than 0.1, by reviewing the analytical data more closely to be more sure that the analytical laboratory results actually reflect the quantities of constituents in the waste.  Our second set of calculations are to develop central tendency estimates for those constituents whose high end estimates result in a hazard quotient greater than 0.1.  By using this process, we narrow down the list of 56 constituents to a more manageable list of constituents of potential concern that we can scrutinize more closely.

5.1   Unlined landfill analysis

To calculate the hazard quotients for the scenario of disposal in an unlined landfill, we use DRASv2 to represent the movement of chemical constituents from the waste in the landfill toward human receptors, and to develop high end estimates of the doses of those constituents to which nearby human receptors would be exposed.  Appendix B shows the specific model inputs that we used to develop these initial high end estimates (including the toxicity values that we use as comparisons to identify potential adverse health effects).  Note that, in some cases, we adjust the default values found in the DRASv2 model to reflect newer recommendations (for example, for toxicity research conducted since the DRASv2 model was developed) or to reflect knowledge of certain minor problems with the DRASv2 default values.  If you are interested in running the DRASv2 model to see how we estimate the results shown in this document, you can replicate our methodology by using our model inputs.  If you use the default model inputs in DRASv2, instead of the inputs shown in Appendix B, you will get results that will differ slightly, for some constituents, from the results we present in this document.  You must set the “carcinogen/noncarcinogen” field at “noncarcinogen” in order to obtain the noncancer health effects results in the output screens.  Note that for correct results you must run DRASv2 in “forward-calculate” mode.

Using DRASv2, we assess the potential non-carcinogenic hazards to humans from 52 of the 56 constituents listed in Table 3.   (See the discussion in section 8 on fluoride, sulfide, lead and trivalent chromium.)

The human exposure variable settings that are built into the model represent an adult who

weighs 72 kilograms,

drinks 2 liters of water per day,

eats 20 grams of fish per day,

breathes 20 cubic meters of air per day,

has a skin surface area of 20,000 square centimeters, and

showers for 15 minutes (dermal exposure) or 11.4 minutes (inhalation exposure) on a daily basis

or a child who:

weighs 15 kilograms,

ingests 200 milligrams of soil per day, and

has a skin surface area of 7,900 square centimeters.

The model assumes that both the adult and child reside at home 350 days per year.

For waste volumes disposed, we review the information contained in the delisting petitions submitted and more recent data provided by facilities in the motor vehicle manufacturing industry (see Appendix C for a detailed description of these data and assumptions that we have made regarding them.)  Combining the data from both sources for past generation or disposal of this waste, we find volumes ranging from 426 to 3892 cubic yards per year (the median was 1,088 cubic yards per year, and the 90th percentile ranked value was approximately 2,900 cubic yards per year).  We use the total waste volume of 90,000 cubic yards disposed for the initial high end estimates.  For the central tendency estimates, we use the total waste volume of 21,760 cubic yards disposed.,

5.1.1.   High end results for unlined landfill

Table 7 shows the model-calculated high end estimated hazard quotients for the 52 constituents, using the maximum waste concentrations shown in the spreadsheet in the docket, along with the exposure pathways that contribute to the estimated exposures.

Table 7.  Chemical constituents' estimated high-end hazard quotients

at 90,000 cubic yards disposed

	 	 	estimated	exposure	exposure

	hazard	pathway	route

	Constituent	CAS#	quotient	of concern

	Detected in both totals and leachate samples:

nickel	7440020	2	groundwater	 ingestion

	zinc	7440666	0.5	groundwater	 ingestion

	barium	7440393	0.01	groundwater	 ingestion

	copper	7440508	0.0008	groundwater	 ingestion

	tin	7440315	0.4	groundwater	 ingestion

	formaldehyde	50000	0.6(0.005)	air 	 inhalation

	cobalt	7440484	0.04	groundwater	 ingestion

	mercury	7439976	2 (0.005)	groundwater	 inhalation

	xylenes	1330207	0.1	groundwater 	ingestion, inhalation and dermal

	vanadium	7440622	0.04	groundwater	 ingestion

	arsenic	7440382	1(0.1)	groundwater	 ingestion

	cyanide	57125	0.0007	groundwater	 ingestion

	ethylbenzene	100414	0.02	groundwater	ingestion, inhalation and dermal

	hexavalent chromium	18540299	0.003	groundwater	 ingestion

	toluene	108883	0.005	groundwater	ingestion, inhalation and dermal

	butanol, n-	71363	0.02	groundwater 	ingestion and dermal

	acrylamide	79061	0.9 (0.002)	groundwater	 ingestion

	cadmium	7440439	0.2	groundwater	 ingestion

	bis(2-ethylhexyl) phthalate	117817	0.002	groundwater	ingestion and dermal

	antimony	7440360	0.3	groundwater	 ingestion

	methyl ethyl ketone 	78933	0.0008	groundwater	 ingestion

	beryllium	7440417	0.001	groundwater	 ingestion

	selenium	7782492	0.1	groundwater	 ingestion

	silver	7440224	0.01	groundwater	 ingestion

	thallium	7440280	1(0.08)	groundwater	 ingestion

	butyl benzyl phthalate	85687	0.0003	groundwater	ingestion and dermal

	naphthalene	91203	0.2	groundwater	ingestion, inhalation and dermal

	cresol, p- 	106445	0.02	groundwater	ingestion and dermal

	acetone	67641	0.007	groundwater	ingestion, inhalation and dermal

	trichloroethylene	79016	0.002	groundwater	ingestion, inhalation and dermal

	dichloroethane, 1,2-	107062	0.00008	groundwater	ingestion, inhalation and dermal

	acetonitrile	75058	0.007	groundwater	 inhalation

	chlorobenzene	108907	0.03	groundwater	ingestion and dermal

	methylene chloride	75092	0.0009	groundwater	ingestion, inhalation and dermal

	trichloroethane, 1,1,1-	71556	0.00004	groundwater	ingestion, inhalation and dermal

	dichloroethane, 1,1-	75343	0.00008	groundwater	ingestion and dermal

Detected only in totals samples (not in leachate samples):

di-n-octyl phthalate	117840	0.04	groundwater	ingestion and dermal

	methyl isobutyl ketone 	108101	0.000007	groundwater	 inhalation

	tetrachloroethylene 	127184	0.001	groundwater	ingestion, inhalation and dermal

	styrene	100425	0.0000009	groundwater	ingestion, inhalation and dermal

	acrolein	107028	0.00026	air 	 inhalation

	dichloroethylene, cis-1,2-	156592	0.002	groundwater	ingestion and dermal

	methyl chloride 	74873	0.002	groundwater	 inhalation

	carbon disulfide	75150	0.00004	groundwater	ingestion, inhalation and dermal

	chloroform	67663	0.00008	groundwater	ingestion, inhalation and dermal

	benzene	71432	0.0002	groundwater	ingestion, inhalation and dermal

	allyl chloride	107051	0.01	groundwater	 inhalation

Detected only in leachate samples (not in totals samples):

phenol	108952	0.01	groundwater	ingestion and dermal

	acetophenone	98862	0.00006	groundwater	ingestion and dermal

	di-n-butyl phthalate	84742	0.0002	groundwater	ingestion and dermal

	cresol, o-	95487	0.003	groundwater	ingestion and dermal

	cresol, m- 	108394	0.005	groundwater	ingestion and dermal

	Note 1: results rounded to one significant figure.

	Note 2: tin, cobalt and di-n-octyl phthalate used intermediate value for oral reference dose; trichloroethylene and 1,1,1-trichloroethane used intermediate value for

inhalation reference; p-cresol used acute value for oral reference dose

Note 3: acrylamide, arsenic, mercury and thallium results presented for nominal maximum leachate concentration;

parenthetical results are for likely true maximum concentration (see discussion of results in text)

Note 4: formaldehyde results presented for nominal maximum totals concentration; parenthetical results are for

likely true maximum totals concentration (see discussion of results in text)

Note 5: copper results presented using an oral reference dose of 0.03 mg/kg-day in effect in spring 2004.  Current ATSDR oral MRL for copper is 0.01 mg/kg-day; using this current value would be expected to increase the model result shown above by a factor of 3.

We have varying degrees of certainty regarding the degree of health effects that may be experienced due to the human exposures that we modeled.   See the discussion in section 9 on uncertainty in the estimates shown in Table 7, and the discussion below that addresses some of these uncertainties in more detail.

Thirteen constituents out of the 52 evaluated using DRASv2 appear to have maximum waste concentrations that equal or exceed one-tenth of the hazard quotient: antimony, arsenic, acrylamide, cadmium, formaldehyde, mercury, naphthalene, nickel, selenium, thallium, tin, xylenes, and zinc.  (Two equal one-tenth of the hazard quotient: xylenes and selenium.  The other 11 exceed one-tenth of the hazard quotient.)  Twelve of the thirteen (all except for formaldehyde) show exposures occurring via groundwater pathways.  For the thirteenth (formaldehyde), the exposure occurs via air pathways.  For the twelve that show exposures occurring via groundwater pathways, most (all except for mercury, naphthalene and xylenes) show exposures occurring via groundwater ingestion only.  Mercury shows exposures occurring via inhalation during showering, when using groundwater as shower water, while both naphthalene and xylenes show exposures occurring as a result of three groundwater uses: ingestion exposure from drinking the water, dermal exposure from bathing, and inhalation exposure from using it as shower water.

For the noncancer health effects calculations, the DRASv2 model accounts for children’s exposures via some pathways and exposure routes, but not all pathways/exposure routes included in the model.  DRASv2 accounts for a child’s groundwater dermal exposure during bathing, and it accounts for children’s exposure due to soil ingestion.   However, it does not calculate noncancer health effects for a child’s groundwater ingestion.  It also does not account for a child’s inhalation of volatilized constituents during bathing or showering with contaminated groundwater, nor does it account for children’s exposure due to direct air inhalation or the surface water pathways.  Direct air inhalation and surface water pathways did not appear to be significant pathways leading to adverse noncancer health effects, for the adult exposures modeled (except for formaldehyde; but see discussion in section 5.1.2 on formaldehyde).

The DRASv2 model was released in April 2002.  In September 2002, EPA published a set of recommended children’s exposure factors.  These recommended exposure factors were under development when the DRASv2 model was released.

To better reflect the potential noncancer health effects that children could experience due to ingesting groundwater contaminated with constituents from the F019 waste, we develop an adjustment factor that reflects two of the differences between children and the adult that was modeled using DRASv2: their body weights, and their drinking water intakes.  The age ranges, body weights, and drinking water intakes of the children who would be using the groundwater as a drinking water source determine the magnitude of the adjustment factor.  We develop an adjustment factor for a child who begins using the groundwater as drinking water at the age of six months and continues drinking it until just before his/her fourth birthday, has a mean body weight (during that time interval) of 12.7 kilograms, and (at the 90th percentile level drinking water intake) drinks 0.72 liters per day (compared to the adult’s assumed body weight of 72 kilograms, and approximately 84th percentile drinking water intake of 2 liters per day).  The ratio of the child’s exposure to the modeled adult’s exposure (in other words, the adjustment factor) is 2.04.  Different choices of age group, body weight percentile, and/or drinking water percentile could affect the numerical value of the adjustment factor in either an upward or downward direction.

Thus, to reflect a young child’s exposure due to groundwater ingestion, we must adjust upward by a factor of 2.04 the groundwater ingestion portion of the estimated hazard quotients for the Table 7 constituents with estimated hazard quotients at or above 0.1.

The DRASv2 model indicates that three of the constituents (out of the thirteen with estimated hazard quotients at or above 0.1) cause other groundwater exposures besides ingestion.  The three constituents are mercury, xylenes and naphthalenes.   For these three, we cannot simply multiply the Table 7 estimated hazard quotient by 2.04.  For naphthalene and xylene, the groundwater inhalation pathway is responsible for the majority of the modeled person’s exposure.  We apply the adjustment factor of 2.04 for the groundwater ingestion portion of the total modeled exposure, and the dermal exposure from bathing already accounts for children’s exposure.  However, we cannot readily adjust the modeled exposures to account for children’s exposure via inhalation of constituents volatilized from groundwater used in bathing or showering.  We anticipate that most children bathe, rather than shower, and there is no model for bathing exposure that we are aware of.  Applying the adjustment factor for the groundwater ingestion portion of the total modeled exposure for these two constituents does not change the estimated hazard quotient shown in Table 7 for naphthalene, because most of the estimated hazard quotient reflects the adult’s exposure via inhalation due to showering.  For xylene, although most of the estimated hazard quotient reflects the adult’s exposure via inhalation due to showering, adjusting the groundwater portion of the total modeled exposure to account for the child age 0-4 changes the rounded estimated hazard quotient from 0.1 to 0.2.  For mercury, we do not adjust the estimated hazard quotient since it is due to groundwater inhalation rather than ingestion.

Table 8 shows the original (adult) hazard quotients for the eleven constituents with groundwater exposures of concern, for which we adjusted hazard quotients to reflect the young child’s exposure.  These adjusted estimated hazard quotients reflect the exposure, via ingestion of groundwater, of a 12.7 kilogram child who drinks 0.72 liters per day, and also the dermal exposure via bathing with groundwater, and soil ingestion, of a 15 kilogram child with a skin surface area of 7,900 square centimeters who ingests 200 mg soil/day.

Table 8.  Chemical constituents' high-end estimated hazard quotients

at 90,000 cubic yards disposed (adjusted for children's exposure

by a factor of 2.04)

Constituent	CAS#	Hazard quotient	Hazard quotient

 	 	adult	child

Detected in both totals and leachate samples:

Nickel	7440020	1.7	3

Zinc	7440666	0.54	 1

Tin	7440315	0.41	0.8

Xylenes	1330207	0.12	0.2

Arsenic	7440382	1.2(0.12)	2(0.2)

Acrylamide	79061	0.94 (0.0023)	2(0.005)

Cadmium	7440439	0.16	0.3

Antimony	7440360	0.31	0.6

Selenium	7782492	0.14	0.3

Thallium	7440280	.84(0.063)	2(0.1)

Naphthalene	91203	0.22	0.2

	Note 1: adult results shown at two significant figures for calculation purposes;

 child results rounded to one significant figure.

	Note 2: tin used intermediate (rather than chronic) value for oral reference dose

Note 3: acrylamide, arsenic, and thallium results presented for

 nominal maximum concentration; parenthetical results are for

likely true maximum concentration (see discussion of results in text)

High end results discussion

The DRASv2 modeled movement for the 13 constituents identified in section 5.1.1 as having high end estimated hazard quotients at or above 0.1 indicates that the hazard from most, if realized, would occur via the groundwater pathway (constituents would leach from the waste into groundwater underneath the landfill, and then be ingested or inhaled by humans using the groundwater as a drinking water or bath/shower water source).  In one case (formaldehyde), the modeled movement indicated that the hazard, if realized, would occur via the air pathway.  The DRASv2 model groundwater pathway results are influenced by the leachate concentrations used as model inputs.  The DRASv2 model air pathway results are influenced by the totals concentrations used as model inputs.  Thus we undertook a more careful review of the analytical laboratory procedures used to measure the leachate and totals concentrations of these 13 constituents.

After performing this review, we conclude that the maximum detected values used in this initial DRASv2 modeling were anomalous for a number of these constituents.    SEQ CHAPTER \h \r 1 From the summary of analytical data provided in the spreadsheets in the docket, we find that the results for some constituents appeared to be more reliable when more selective and/or sensitive methods were used.  The constituents most affected by method choice were: acrylamide, formaldehyde, arsenic, and thallium.  There were also some limitations in some of the data for mercury (described below) and fluoride (described in section 8).

Acrylamide.  As described in the final delisting for six facilities in Michigan (68 FR 44652, July 30, 2003), samples of F019 sludge were initially analyzed for acrylamide using Method 8316 (EPA 1994).  However, the data validation report stated that this was not sufficiently selective for acrylamide in these wastes.  (Acrylamide is a potential trace contaminant in the flocculent-aide used in wastewater treatment plants.)  Six facilities completed further analyses by a more sensitive method, Method 8032A (EPA 1994) using Selected Ion Monitoring and did not detect any acrylamide (in 28 samples analyzed at six different plants).  The reported detection limits ranged from 0.0004 to 0.0007 mg/L.  Some facilities also submitted a detailed mass balance that concluded that the maximum possible acrylamide that could be in the sludge would be much lower than the reported detections.  Based on the results for the facilities that analyzed for acrylamide use the more selective method, EPA determined that the previous analytical results were not meaningful; the initial method used was not selective and may have detected chemicals other than acrylamide.  Using the higher of the two detection limits, 0.0007 mg/L value as the maximum value (rather than the 0.29 mg/L value that we used in the initial analysis), yields a hazard quotient of 0.002 (shown in parentheses in Table 7).

Arsenic and Thallium.  As described in the final delisting for six facilities in Michigan (68 FR 44652, July 30, 2003), initial analyses of samples of F019 sludge for arsenic and thallium yielded TCLP levels of potential concern.   These analyses used method 6010B (EPA 1994).   Samples were reanalyzed for these constituents using the more sensitive Method 6020, and the results were below the delisting levels.  The delistings were granted, based on the results from Method 6020 analyses.  The analytical data submitted for these petitions were validated by an independent third party using EPA data review guidelines.

Method 6020 (Inductively Coupled Plasma-Mass Spectrometry) is more sensitive and more specific than Method 6010B (Inductively Coupled Plasma-Atomic Emission Spectrometry).  The Inductively Coupled Plasma-Atomic Emission Spectrometry method measures the emissions from different metal ions, which overlap for some elements.  Such overlap requires correction for spectral interferences (e.g., aluminum may interfere with measurement of arsenic and thallium).  The detector in the Inductively Coupled Plasma-Mass Spectrometry method measures the molecular weight of the atoms produced, and therefore, determines their identity.  Inductively Coupled Plasma-Mass Spectrometry is also subject to some interferences due to ions that have the same molecular weight as the target mass ion (isobaric interferences).   However, the Inductively Coupled Plasma-Mass Spectrometry method is preferred for the analysis of metals such as arsenic and thallium because it generally yields lower detection limits, and its detection method provides a more definitive identification through mass spectra information.

Many of the detections reported using Method 6010B were at or below the detection limit and were attributed by petitioners to false positives from interferences from the matrix or other analytes present.  In addition, an industry group submitted a discussion of the merits of Method 6020 over Method 6010B. In any case, EPA believes that the results from Method 6020 are more reliable; Table 9 includes the analytical results for samples that were analyzed by this method.  Table 7 includes, in parentheses, the calculated hazard quotients using samples that were analyzed using Method 6020.

Table 9.  Adjusted maximum concentrations for selected constituents

	Constituent	CAS#

maximum

adjusted

	in docket

maximum

	spreadsheet

	mg/L

mg/L

Leachate:

acrylamide	79061

0.29

0.0007

arsenic	7440382

0.48

0.048

formaldehyde	50000

16

3

mercury	7439976

0.484

0.001

thallium	7440280

0.27

0.02

maximum

adjusted

	in docket

maximum

	spreadsheet

	mg/kg

mg/kg

Totals:

formaldehyde	50000

19,100

142

	Note: acrylamide's adjusted maximum is the higher of two reported detection limits

Formaldehyde.  The analytical data for formaldehyde generally showed low totals levels in sludge samples (average 18.8 mg/kg), except for data for two facilities (General Motors, Oklahoma City, OK and General Motors, Lansing, MI).  For these two facilities, samples analyzed for formaldehyde totals using a wet chemistry method yielded much higher results (average 9,776 mg/kg).  The facility in Lansing, MI, did further analysis using a more selective method (High Performance Liquid Chromatography, Method 8315 (EPA 1994)), and the total formaldehyde levels dropped 100-fold.  The Lansing, MI, petitioner noted that the wet chemistry method is subject to significant positive interferences from other chemicals and used the HPLC method in subsequent verification testing.  The facility in Oklahoma City did not pursue a delisting, and did not do any further analysis.

  SEQ CHAPTER \h \r 1 We received additional information from a representative of General Motors Corporation that described the potential problems with the wet chemistry method.   The document notes that, not only is the wet chemistry method less selective, this method also requires that the sample be heated (~215o F) to distill off formaldehyde.  Formaldehyde may be present in sludges if formaldehyde resins are used in the automotive painting process.  However, the formaldehyde-based resins may also be present in the waste sludge.  When samples are distilled, the resins are heated and release significant additional formaldehyde during the distillation.  This formaldehyde is trapped with the distillate and is erroneously measured as free formaldehyde.

Formaldehyde is extremely soluble in water, and is expected to partition into wastewater, rather than concentrate in the sludge.  In addition, formaldehyde should extract nearly completely into the aqueous phase in the TCLP tests.  Thus, the total level measured in a solid sample should be very close to 20 times the concentration measured in the TCLP extract from the sample (the TCLP method requires extraction of solid samples with 20 times the weight of the solids; see Method 1311 (EPA 1994)).  The levels of formaldehyde measured in the totals analysis at the two facilities with anomalous results yielded ratios of totals to TCLP values that were much higher than the expected ratio of about 20 (1,000 to 3,600-fold at the Oklahoma City facility and 1,200 to 10,000-fold at the Lansing, MI, plant).   Therefore, the Agency believes that the totals analyses for formaldehyde at these two sites are not indicative of the level of formaldehyde in the F019 sludge that is available for release at normal temperatures.  Similarly, the leachate analyses for several samples containing formaldehyde used the same wet chemistry method.  Omitting the wet chemistry leachate values from the observations shown in the spreadsheet in the docket yields a new ‘maximum” formaldehyde leachate value of 3 mg/L.

Table 9 shows that, by omitting the data from the wet chemistry method at these two facilities, the maximum detected value for “total” formaldehyde is 142 mg/kg.  Table 7 includes, in parentheses, the calculated hazard quotient using this adjusted maximum total formaldehyde result.

Mercury.  The sample with highest TCLP mercury value (0.484 mg/L) appears to be anomalous.  The corresponding totals level of mercury in this sample was 0.67 mg/kg (see data in the spreadsheet in the docket for General Motors, Oklahoma City).  Using a conservative dilution factor of 20 for the TCLP test, the maximum TCLP value would be < 0.0335 mg/L.  Thus, the reported TCLP data point appears erroneous, especially in light of the nondetects seen in other TCLP results for wastes with similar total mercury values.  Discounting this data point, there were only 3 other detected TCLP values for mercury, the highest concentration being 0.001 mg/L, which yields a hazard quotient of 0.005 (noted in parentheses in Table 7).

With re-calculated estimated high end hazard quotients well below 0.1, we drop acrylamide, formaldehyde and mercury from further analysis.  We retain arsenic and thallium, however, with re-calculated estimates of high end hazard quotients of 0.1 and 0.08, respectively.

Considering children’s exposure, and using the Tables 4 and 5 results (including re-calculated results in parentheses for acrylamide, arsenic, formaldehyde and thallium) of  estimated high end hazard quotients that are above 0.1, yields a narrowed list of 10 constituents of potential concern:  antimony, arsenic, cadmium, naphthalene, nickel, selenium, thallium, tin, xylenes and zinc).   Naphthalene and xylene are from Table 7, while the remaining eight are from Table 8.

For these ten constituents, two (nickel and zinc) equal or exceed a hazard quotient of one.  For eight of the ten, the only exposure pathway of concern was ingestion of groundwater.  Xylenes and naphthalene had additional exposure pathways of concern (besides groundwater ingestion) of dermal contact during bathing, and groundwater inhalation during showering.

5.1.3   Central tendency results and discussion

We use the narrowed list of 10 constituents from section 5.1.2 to perform a central tendency analysis.  (The constituents with high end estimates below the range of concern would have central tendency estimates that are even lower than estimates for these ten constituents, and thus, we need not analyze them.)  We use Table 10 analytical values for median totals and leachate concentrations.  The remaining model inputs are the same as shown in Appendix B.

Table 10.  Detection frequencies and concentrations for constituents of potential concern (including

selected data sets based on particular analytical methods used)

	Constituent	CAS#	 	leachate

90th

detection 	median	mean	percentile	maximum

	 	 	frequency	mg/L	mg/L	mg/L	mg/L

nickel	7440020	163/163	17	22	47	83

	zinc	7440666	143/145	4.6	17	52	270

	tin	7440315	79/98	6.9	11	21	82

	xylenes	1330207	44/138	0.054	0.2	0.22	4.5

	arsenic - all data	7440382	81/146	0.025	0.098	0.29	0.48

	arsenic - method 6020	7440382	21/21	0.011	0.015	0.025	0.048

	cadmium	7440439	37/136	0.008	0.017	0.021	0.16

	antimony	7440360	36/104	0.035	0.064	0.14	0.29

	selenium	7782492	46/112	0.22	0.2	0.39	0.56

	thallium - all data	7440280	25/99	0.062	0.086	0.2	0.27

	thallium - method 6020	7440280	8/8	0.0065	0.0087	0.019	0.02

	naphthalene	91203	34/117	0.0035	0.016	0.021	0.29

	Constituent	CAS#	 	totals

90th

detection 	median	mean	percentile	maximum

	 	 	frequency	mg/kg	mg/kg	mg/kg	mg/kg

nickel	7440020	106/106	1300	1600	3400	5720

	zinc	7440666	89/89	7100	7900	15000	17600

	tin	7440315	82/83	240	490	930	2310

	xylenes	1330207	68/89	2.2	5.4	14	42

	arsenic - all data	7440382	47/84	7.9	8.5	18	25

	cadmium	7440439	41/105	1.1	4.1	20	21.5

	antimony	7440360	25/88	5.5	15	30	174

	selenium	7782492	18/83	2.5	5.1	14	21

	thallium - all data	7440280	11/84	1.1	1.6	1.5	7.1

	naphthalene	91203	7/84	21	22	32	34

	Note 1: means, medians and 90th percentiles calculated from detected values only

Note 2: means, medians and 90th percentile rounded to two significant figures

Note 3: The 90th percentile value is calculated from a rank order

  of the available data (using Excel® PERCENTILE formula).

Table 11 shows the results from running DRASv2 at the central tendency settings of 1088 cubic yards/year for 20 years.  However, the results shown in the column headed “raw results” are at the high end drinking water intake of 2 liters/day (approximately the 84th percentile).  To better reflect a central tendency drinking water intake, we apply an adjustment factor of 0.75 to the raw results, in order to represent an adult with average body weight (72 kilograms) who drinks water at the mean drinking water intake of 21 milliliters per kilogram of body weight per day, or 1.5 liters per day (EPA 1997b, Table 3-30).  To estimate a child's drinking water intake, we apply an adjustment factor of 0.9 to the raw results, in order to represent a child aged 6 months to <4 years with average body weight (12.7 kilograms) who drinks water at the mean drinking water intake (on average during that 3 1/2 year period) of 0.32 liters/day (EPA 2002b, p. 4-16).  We only apply these adjustment factors to the results for antimony, arsenic, cadmium, nickel, selenium, thallium, tin and zinc, because the DRASv2 model indicates exposures via the groundwater ingestion route only.  The majority of the groundwater pathway exposure from naphthalene and xylenes is from inhalation during bathing/showering, and thus even adjusting the small contribution to total exposure that the DRASv2 model indicates occurs via groundwater ingestion would not make a significant difference in the central tendency estimates for these two constituents.  In addition, we do not adjust any of the variable settings for groundwater inhalation or groundwater dermal exposure to represent central tendency values, because the extra effort to do so would not have any significant effect on the central tendency estimates.

Table 11.  Estimated central tendency hazard quotients for constituents of potential concern

  at 21,760 cubic yards disposed

	Constituent	CAS#	 	adjusted for	adjusted for

raw	mean drinking	mean drinking

results	water intake	water intake

 	 	(adult)	(adult)	(child)

nickel	7440020	0.1	0.09	0.1

zinc	7440666	0.003	0.002	0.003

tin	7440315	0.01	0.009	0.01

xylenes	1330207	0.0007

arsenic	7440382	0.01	0.008	0.009

cadmium	7440439	0.003	0.002	0.003

antimony	7440360	0.01	0.01	0.01

selenium	7782492	0.02	0.02	0.02

thallium	7440280	0.01	0.007	0.009

naphthalene	91203	0.001

Note: estimates rounded to one significant figure

Table 11 estimates reflect exposures of the 72-kilogram adult described in section 5.1, and the exposure, via ingestion of groundwater, of a 12.7 kilogram child who drinks 0.32 liters per day, and also the dermal exposure via bathing with groundwater, and soil ingestion, of a 15 kilogram child with a skin surface area of 7,900 square centimeters who ingests 200 mg soil/day.

5.2.   Lined landfill analysis

Section 5.1.2 identifies 10 constituents of potential concern, or COPCs, of which one (nickel) had an estimated high end hazard quotient that exceeded one.  The DRASv2 modeled scenario indicates that nickel would move and affect human health via the groundwater pathway.  The DRASv2 high end evaluation indicates that the potential adverse human health effects would occur as a result of movement of nickel from the waste in the landfill into groundwater underlying the landfill.  Thus, we examine the DRASv2 modeled scenario of unlined landfill conditions more closely.  Specifically, we are interested in knowing whether modeling lined, rather than unlined, landfills would affect estimates of potential health effects.

	Changes to landfill requirements in the United States (e.g., the promulgation of federal regulations that require municipal solid waste landfills to meet certain leakage prevention requirements; see 40 CFR 258.40), have caused substantial changes in landfill practices.  The majority of municipal solid waste landfills, and probably many landfills that accept nonhazardous industrial solid waste but not municipal solid waste, now are designed, built, and operated with liner systems that typically include composite liners and leachate collection systems.  The potential risks found by the DRAS version 2.0 modeling were all from groundwater exposure pathways.  As a result, current landfills with liner systems and leachate collection systems should dramatically lessen impacts on local groundwater conditions.  DRAS does not have an option to model the impact of liners on landfill releases.  Therefore, we examine the potential impact of liners using other tools.

We review modeling results that incorporate information about the effectiveness of landfill liners in reducing “infiltration,” or water that flows downward through the bottom of the landfill and enters the groundwater system beneath the landfill.  We used the Industrial Waste Management Evaluation Model (IWEM) to show the impact of landfill liners on infiltration, and thus the effect that landfill liners have on slowing the downward movement of constituents from the landfill into the groundwater system underneath the landfill.  Slowing the downward movement has the practical effect of reducing the rate at which chemical constituents enter the groundwater system.  A reduced entry rate results in less chemical constituent moving in the groundwater (over a given time interval), and thus lower constituent exposures (and reduced hazard and risk estimates) for the groundwater users.  We also examine the results of the risk analysis completed for a recent EPA rulemaking that listed certain wastes from the dyes and pigments industry as hazardous, under certain conditions (dyes and pigments analysis, or D&P).

5.2.1   Results of IWEM Tier 1 Evaluation

We use Tier 1 of the IWEM model (EPA 2002c, EPA 2002d) to evaluate the impact of landfill liners on predicted human health effects.  Tier 1 is a very simple screening mode in which users enter the chemical constituents of interest, together with their leachate concentrations in the waste, and receive output regarding the “allowable” levels in the waste that correspond with the same risk management criteria that we used in the DRASv2 evaluation for noncancer health effects, along with an indication of whether the landfill scenario is protective of human health at the modeled leachate concentration.

For comparison purposes, we use the same maximum leachate concentration that we use in the DRASv2 high end evaluation.

Unlike DRASv2, IWEM’s groundwater ingestion equations model the exposures of a child from birth to age 6 who drinks 42.6 milliliters of water per kilogram body weight per day during that time interval.  The modeled adult weighs 71.8 kilograms, and breathes 13.25 cubic meters of air per day.

Disposing of waste containing nickel at the maximum leachate value in an unlined landfill would not be protective of human health, according to the assumptions and the reference doses and reference concentrations used in the IWEM Tier 1 software.

IWEM Tier 1 also shows results as “allowable levels” in the waste leachate samples, that correspond to the risk management criterion used in the IWEM model (the same noncancer risk management criterion used in DRASv2).  DRASv2 also calculates allowable levels.  Thus, comparing the allowable levels of IWEM Tier 1 (unlined) for noncancer effects to the DRASv2 allowable levels (unlined) for noncancer effects indicates numerically how the assumptions used in IWEM Tier 1 compare to the assumptions used in DRASv2.  According to the IWEM Tier 1 model, the allowable level of nickel in leachate from the waste, disposed in an unlined landfill, would be 1.1 mg Ni/liter of leachate.  According to the DRASv2 model, the allowable level of nickel in leachate from the waste, disposed in an unlined landfill, would be 24.5 mg Ni/liter of leachate.

The IWEM Tier 1 results for a single-lined landfill and composite-lined landfill are not comparable with the DRASv2 results, since the DRASv2 evaluation models an unlined landfill.  The IWEM Tier 1 results indicate that disposing of waste containing nickel at the maximum leachate value (83 mg Ni/liter of leachate) in a single-lined landfill would be problematic, since the allowable level in leachate calculated by IWEM Tier 1 is 3.3 mg Ni/liter of leachate.  The IWEM Tier 1 results indicate that disposing of waste containing nickel at the maximum leachate value in a composite-lined landfill would not be problematic, since the allowable level in leachate calculated by IWEM Tier 1 is 1000 mg Ni/liter of leachate.  Thus, according to the IWEM model, the protection afforded by a composite-lined landfill is sufficient to alleviate concerns about potential adverse health effects that could occur due to the presence of these nine constituents in F019 waste, at the maximum leachate concentrations that were modeled.

Comparing the allowable levels of the IWEM Tier 1 single liner scenario to the IWEM unlined scenario indicates numerically what is the impact of a single liner on the infiltration rate, and the resulting reduction in chemical constituent exposure to the groundwater user.  For nickel, the IWEM single liner allowable level of 3.3 mg Ni/liter of leachate is a factor of 3 greater than the IWEM unlined landfill allowable level of 1.1 mg Ni/liter of leachate.

5.2.2   Results of D&P Evaluation

The analysis of landfill liners for the “dyes and pigments” (D&P) listing (EPA 2003c, p. 2-4) indicates that clay-lined, synthetic-lined, and geomembrane/geocomposite-lined landfills afford additional protection from chemical constituent exposures via the groundwater pathway, compared to the unlined landfill scenario.  We examined the modeling performed for lined landfills in the recent listing rule for dye and pigment production wastes (February 24, 2005, 70 FR 9138).  In the D&P rule, EPA established a conditional exemption for wastes disposed in landfills meeting liner design requirements, similar to the exemption proposed for F019 sludge from motor vehicle manufacturers.