Page 1 of 125 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D. C. 20460 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES June 21, 2006 MEMORANDUM SUBJECT: ORGANIC ARSENICS: Final HED Combined Chapter of the Reregistration Eligibility Decision Document ( RED). Organic Arsenics: Cacodylic Acid & Salt, PC Code 012501/ 012502; MSMA, PC Code 013802; DSMA, PC Code 013803; and CAMA, PC Code 013806. DP Barcode: D329694 FROM: Charles Smith, Risk Assessor/ Environmental Scientist Reregistration Branch 2 Health Effects Division ( 7509P) AND Anna Lowit, Ph. D. Sherrie Kinard Yvonne Barnes Ruth Allen Health Effects Division ( 7509P) AND Keara Moore Environmental Fate and Effects Division ( 7507P)

THRU: Alan Nielsen, Branch Senior Scientist William J. Hazel, Ph. D., Branch Chief Reregistration Branch 2 Health Effects Division ( 7509P)

TO: Lance Wormell, CRM Reregistration Branch 2 Special Review and Reregistration Division ( 7508P)

The attached post Science Advisory Board ( SAB) review of the Human Health Assessment for the organic arsenic RED document was generated as part of Phase 4 of the public participation process. The Health Effects Division's ( HED) Final chapter reflects the comments received during the Phase 3 public comment period. This risk assessment document includes the potential individual chemical contributions to human health risk of cacodylic acid ( DMA) and its salt, monosodium methanearsonate ( MSMA), disodium methanearsonate ( DSMA), and calcium acid methanearsonate ( CAMA). This assessment also includes a review of the aggregate human health assessment for the potential combined exposures to a common transformation product Page 2 of 125 from the use of the organic arsenicals. Potential risks from exposure to inorganic arsenic resulting from the use of the organic arsenicals are also discussed. This chapter includes a summary of the product chemistry review from Yvonne Barnes, residue chemistry review from Yvonne Barnes/ Sherrie Kinard/ Bonnie Cropp Kohlligian, dietary risk assessment from Sherrie Kinard, toxicology review from Anna Lowit, occupational exposure and risk assessment from Charles Smith, incidence review from Ruth Allen, environmental fate and drinking water exposures from Keara Moore [ Environmental Fate and Effects Division ( EFED)], as well as risk assessment and characterization from Charles Smith.

This assessment relies in part on data from studies in which adult human subjects were intentionally exposed to a pesticide. These studies, listed below, have been determined to require a review of their ethical conduct. The listed studies have either received the appropriate review or are in the process of being ethically reviewed.

Buchet, J. P., Lauwerys, R., & Roels, H. ( 1981). Comparison of the urinary excretion of arsenic metabolites after a single oral dose of sodium arsenite, monomethylarsonate, or dimethylarsinate in man. International Archives of Occupational and Environmental Health, 48( 1), 71 79.

Johnson, L. R., & Farmer, J. G. ( 1991). Use of human metabolic studies and urinary arsenic speciation in assessing arsenic exposure. Bulletin of Environmental Contamination & Toxicology, 46, 53 61.

Marafante, E., Vahter, M., Norin, H., Envall, J., Sandstrom, M., Christakopoulos, A., Ryhage, R. ( 1987). Biotransformation of dimethylarsinic acid in mouse, hamster and man. Journal of Applied Toxicology, 7( 2), 111 117.

Carbaryl Mixer/ Loader/ Applicator Exposure Study During Application of RP 2 Liquid ( 21%), Sevin Ready to Use Insect Spray or Sevin 10 Dust to Home Garden Vegetables. MRID 444598 01 D. Merricks. ( 1997).

Integrated Report for Evaluation of Potential Exposures to Homeowners and Professional Lawn Care Operators Mixing, Loading, and Applying Granular and Liquid Pesticides to Residential Lawns. MRID 449722 01. D. Klonne. ( 1999).

The PHED Task Force, 1995. The Pesticide Handler Exposure Database ( PHED), Version 1.1. Task Force members Health Canada, U. S. Environmental Protection Agency, and the National Agricultural Chemicals Association, released February 1995.

cc: Tina Levine Jack Housenger Debbie Edwards William Hazel Margaret Rice Page 3 of 125 Table of Contents Table of Contents                              .................. 3 Preface .................................................................................................................................................... 5 1.0 Executive Summary........................................................................................................................... 6 2.1 Summary of Registered Uses ....................................................................................................... 10 2.2 Structure and Nomenclature......................................................................................................... 13 Cacodylic Acid & Sodium Cacodylate........................................................................................... 13 MSMA/ DSMA/ CAMA................................................................................................................. 13 3.1 Comparative Metabolic Profile .................................................................................................... 23 3.1.1 In vivo Metabolism Studies ................................................................................................... 25 3.1.2 In vitro Studies ..................................................................................................................... 29 3.2 Nature of the Residue in Foods .................................................................................................... 29 3.2.1 Description of Primary Crop Metabolism.............................................................................. 29 3.3 Environmental Fate...................................................................................................................... 30 3.3.1 Degradation ( Metabolites) .................................................................................................... 31 3.3.2 Mobility ............................................................................................................................... 32 3.3.3 Soil Buildup/ Persistence ....................................................................................................... 32 4.0 Hazard Characterization/ Assessment................................................................................................ 34 4.1 Overview and Background........................................................................................................... 34 4.2 MMA .......................................................................................................................................... 35 4.2.1 Database Summary ............................................................................................................... 35 4.2.2 Toxicological Effects ............................................................................................................ 36 4.2.3 FQPA Hazard Considerations ............................................................................................... 44 4.2.4 Dose Response, Hazard Identification and Toxicity Endpoint Selection ................................ 44 <IP_ADDRESS> Acute Reference Dose ( aRfD)  General Population....................................................... 46 <IP_ADDRESS> Chronic Reference Dose ( cRfD)..................................................................................... 46 <IP_ADDRESS> Incidental Oral Exposure ( Short Term) .......................................................................... 46 <IP_ADDRESS> Incidental Oral Exposure ( Intermediate Term) ............................................................... 47 <IP_ADDRESS> Dermal Exposure ( Short and Intermediate Term) ........................................................... 47 <IP_ADDRESS> Inhalation Exposure ( Short and Intermediate Term) ....................................................... 47 4.2.5 Recommendation for Aggregate Exposure Risk Assessments ................................................ 47 4.2.6 Classification of Carcinogenic Potential ................................................................................ 47 4.2.7 Endocrine Disruption............................................................................................................ 49 4.3 DMA........................................................................................................................................... 49 4.3.1 Database Summary ............................................................................................................... 49 4.3.2 Toxicological Effects ............................................................................................................ 49 4.3.3 FQPA Hazard Considerations ............................................................................................... 52 4.3.4 Dose Response, Hazard Identification and Toxicity Endpoint Selection ................................ 53 <IP_ADDRESS> Acute Reference Dose ( aRfD)  General Population & Acute Incidental Oral Exposure.. 55 <IP_ADDRESS> Chronic Reference Dose ( cRfD) & Incidental Oral Exposure ......................................... 55 <IP_ADDRESS> Dermal Exposure ( Short and Intermediate Term).......................................................... 55 4.3.5 Recommendation for Aggregate Exposure Risk Assessments ................................................ 57 4.3.6 Classification of Carcinogenic Potential ................................................................................ 57 4.3.7 Endocrine Disruption............................................................................................................ 57 5.1 Incident Reports........................................................................................................................... 58 5.1.1 Cacodylic Acid Incidents ...................................................................................................... 58 5.1.2 MSMA/ DSMA Incidents ...................................................................................................... 59 5.1.3 CAMA Incidents .................................................................................................................. 59 5.2 Other ........................................................................................................................................... 59 6.0 Exposure Characterization/ Assessment ............................................................................................ 59 Page 4 of 125 6.1 Dietary Exposure/ Risk Pathway................................................................................................... 59 6.1.1 Residue Profile ..................................................................................................................... 60 6.1.2 Dietary Risk Assessment/ Characterization ............................................................................ 62 <IP_ADDRESS> Acute Dietary Exposure Results and Characterization .................................................... 63 <IP_ADDRESS> Chronic Dietary Exposure Results and Characterization................................................. 64 <IP_ADDRESS> Dietary Risk Results/ Discussion .................................................................................... 64 6.2 Water Exposure/ Risk Pathway ..................................................................................................... 69 6.2.1 Surface Water Modeling for Drinking Water Estimates ......................................................... 70 <IP_ADDRESS> Inputs/ Characterization.................................................................................................. 71 6.2.2 Drinking Water from Ground Water...................................................................................... 73 6.3 Residential ( Non occupational) Exposure/ Risk Pathway .............................................................. 73 6.3.1 Residential Handler Exposures and Risks.............................................................................. 74 <IP_ADDRESS> Inputs and Assumptions for Residential Handler Risks................................................... 74 <IP_ADDRESS> Summary of Residential Handler Risks .......................................................................... 78 6.3.2 Residential/ Non occupational Postapplication Exposures and Risks ...................................... 79 <IP_ADDRESS> Residential Postapplication Inputs and Assumptions ...................................................... 79 <IP_ADDRESS> Residential/ Non occupational Postapplication Risk Summary........................................ 80 7.0 Aggregate Risk Assessments and Risk Characterization ................................................................... 84 7.1 Acute Aggregate Risk.................................................................................................................. 85 7.2 Short term Aggregate Risk........................................................................................................... 87 7.3 Intermediate term Aggregate Risk................................................................................................ 89 7.4 Long term Aggregate Risk........................................................................................................... 89 7.5 Aggregate Cancer Risk ................................................................................................................ 90 7.6 Aggregate Risk Summary ............................................................................................................ 90 7.7 " Total Arsenic" and Exposure to Inorganic Arsenic ..................................................................... 91 7.7.1 Dietary ................................................................................................................................. 91 7.7.2 Drinking Water..................................................................................................................... 92 7.7.3 Residential Postapplication Exposure.................................................................................... 92 8.0 Cumulative Risk Characterization/ Assessment ................................................................................. 94 9.0 Occupational Exposure/ Risk Pathway .............................................................................................. 95 9.1 Short/ Intermediate term Occupational Handler Exposure and Risk............................................... 96 9.1.1 Inputs/ Assumptions into Handler Exposure/ Risk Estimates ................................................... 96 9.1.2 Summary of Occupational Handler Risk Concerns .............................................................. 117 9.2 Occupational Postapplication Exposures and Risk Estimates ...................................................... 117 9.2.1 Occupational Postapplication Scenarios, Inputs, and Assumptions ...................................... 117 9.2.2 Summary of Occupational Postapplication Risk Concerns................................................... 118 10.0 Data Needs and Label Requirements ............................................................................................ 120 10.1 Product Chemistry ................................................................................................................... 120 10.2 Residue Chemistry................................................................................................................... 120 10.3 Occupational/ Residential Exposure .......................................................................................... 120 11.0 References ................................................................................................................................... 122 12.0 Attachments................................................................................................................................. 124 Page 5 of 125 Preface The Food Quality Protection Act of 1996 requires that EPA's Office of Pesticide Programs review the safety of all existing pesticide tolerances ( the legal limit set on the maximum amount of pesticides that may remain in or on foods) by August 2006. As part of this tolerance reassessment process, the risk assessment on the organic arsenical pesticides is being updated. There are four registered organic arsenical pesticides: cacodylic acid ( dimethylarsinic acid, DMA) and its sodium salt ( sodium cacodylate); monosodium methanearsonate ( MSMA); disodium methanearsonate ( DSMA); and calcium acid methanearsonate ( CAMA). One other organic arsenical, arsanilic acid ( PC 129005), is not included in this assessment. Arsanilic acid is a plant growth regulator with a registration ( expiration 02/ 28/ 2001) for experimental use ( 180.550) in Florida on grapefruit ( tolerance 2 ppm). For ease of discussion the sodium salt of cacodylic acid and cacodylic acid are treated as one and will be referred to as dimethylarsinic acid ( DMA), and MSMA, DSMA, and CAMA will be referred to as monomethylarsinic acid ( MMA). In cases where chemical specific uses, risks, or other issues are being discussed, the specific pesticide name ( MSMA, DSMA, and CAMA) will be used. DMA and MMA can occur as two different valence states. Unless noted, DMA and MMA refer to the + 5 valence state ( e. g., DMAV, MMAV). Section 4.0 of this document describes the mode of action for the development of rat bladder tumors following oral exposure to DMA. One of the key events in this mode of action is the reduction of DMAV to a toxic metabolite, DMAIII. Thus, in Section 4.0, as necessary the specific valence states of DMA are noted.

As part of the reassessment of the organic arsenic herbicides, new studies on the metabolism and the animal cancer mode of action of DMA were evaluated. These studies were the focus of a special issue paper ( USEPA, 2005a) presented to the Science Advisory Board ( SAB) September 12 13, 2005. The paper focused on the carcinogenic mode of action in animals and whether the rat tumor data should be used to estimate human potential risk and if so, how an understanding of the mode of action informs the dose response extrapolation for cancer risk assessment. Based on the deliberations of the SAB, the Agency made appropriate revisions to the issue paper ( USEPA, 2005b). The current risk assessment reflects these revisions, in addition to the revisions that were made based on the comments received during the Phase 3 public comment period. Page 6 of 125 1.0 Executive Summary The Special Review and Registration Division requested that HED conduct a human health aggregate risk assessment/ determination of safety for potential aggregate exposures to residues of arsenic compounds from organic arsenical herbicide use. The Federal Insecticide, Fungicide, and Rodenticide Act ( FIFRA) and the Federal Food, Drug, and Cosmetic Act ( FFDCA) were amended by the Food Quality Protection Act ( FQPA) of 1996. The FQPA differs from FIFRA and FFDCA by the mandate to consider available information concerning the cumulative effects of such residues and other substances that have a common metabolite ( or common mechanism) when performing tolerance assessments for pesticides.

This organic arsenic risk assessment document captures the potential human health risk from both single chemical exposures and, overlapping, or co occurring, exposures to multiple organic arsenical herbicides that can biotransform to a common arsenic species. This assessment includes the four registered organic arsenical herbicides: cacodylic acid ( dimethylarsinic acid; a. k. a. DMA) and its sodium salt ( sodium cacodylate); monosodium methanearsonate ( MSMA); disodium methanearsonate ( DSMA); and calcium acid methanearsonate ( CAMA). Reregistration of DMA is being supported by Luxembourg Pamol, Inc. Reregistration of the MMA salts is being supported by the MAA Task Force ( MAATF), which consists of APC Holdings/ Drexel Chemical Company, KMG Bernuth, Inc., and Luxembourg Pamol, Inc.

DMA is a defoliant ( non selective) used primarily on cotton and to a much lesser extent, on nonbearing citrus, with some non agricultural ( including golf courses, recreational areas, and rightsof way) and residential uses in weed control and lawn renovation. MSMA and DSMA are selective pre and post emergence herbicides used on cotton, non bearing citrus and nuts, golf courses, recreational areas including schoolyards, lawns, and rights of way. CAMA is a selective post emergence herbicide registered for nonfood/ feed uses on golf courses, recreational areas including schoolyards, lawns, and rights of way. CAMA has no registered food uses.

MSMA, DSMA, and CAMA are salts of MMA and readily dissociate to MMA in water. HED has concluded that the primary residues of concern resulting from the herbicidal use of organic arsenics are MMA and DMA per se and their environmental transformation products; MMA, DMA and inorganic arsenic ( iAs). HED and our partners in EFED recognize that over time, and depending on the environmental conditions present, organic arsenicals will biotransform by both methylating and demethylating. Since environmental conditions are variable, it is difficult to quantify organic versus inorganic arsenic residues present at any specific point in time. Additionally, it is known that background residues of both inorganic and organic arsenics exist in soils, and plants, and water, and vary greatly across the United States. The assessment of the potential contribution to human health risk from the herbicidal use of the organic arsenicals is further complicated by the differing toxicity profiles of the organic arsenic species ( MMA differs from DMA), which both differ from iAs. In other words, the target organs and toxicological effects are dissimilar, as well as the magnitude of the toxicity. Hence, HED has chosen a stepwise approach to assessing the potential risks incurred from the use of the organic arsenicals. Page 7 of 125 As part of this stepwise approach, assumptions were made, based on the magnitude of toxicity, as well as the potential for biotransformation to certain arsenic species, that were conservative and health protective. The biotransformation of the arsenic species, iAs   MMA   DMA is predominantly unidirectional in mammals and in the environment but, environmental conditions can alter the progression from most toxic ( iAs) to least toxic ( MMA). It should be noted that any discussion of relative toxicity ( least vs. most) concerns the magnitude of the dose response, not target organs. In vivo and in vitro toxicity studies indicate that the various arsenical compounds have distinct toxicological profiles. Whereas, exposure to high levels of iAs in drinking water results in a variety of adverse health effects including diabetes mellitus, cardiovascular disease, renal disease, vascular skin lesions and cancer, and lung, liver and bladder cancer; long term animal studies with MMA suggest that the large intestine is the target organ with no neoplastic lesions observed at any site. DMA causes bladder tumors in rats after feeding or drinking water exposures. Because of the distinct pharmacokinetic and pharmacodynamic differences that are observed following direct oral exposure to MMA and DMA, it was appropriate to use chemicalspecific data for extrapolating risks for these herbicides. A more detailed discussion of these differences can be found in Section 4.0. The toxicity of iAs has been the subject of risk assessments conducted by OPP's Antimicrobial Division and the Agency's Office of Water ( OW). An in depth discussion of iAs toxicity can be found in Chen 2001 and www. epa. gov/ safewater/ arsenic. html.

Dietary risk estimates were assumed to be to residues resulting from the herbicidal uses, with and without background exposures. Submitted plant and animal metabolism data, as well as open literature show a tendency for the organic arsenicals to biotransform but, the extent and rapidity to which the transformation occurs at any one time is unknown, so exposures are likely to be to a variable mixture of both organic and inorganic arsenicals. Currently, little is known about the transformation of arsenicals taken up from the soil. For risk assessment purposes HED has provided a range of risk estimates that assume no transformation of the applied compound, and complete or partial transformation to DMA. Potential risks from exposure to iAs were also considered. Dietary residues in food were calculated from submitted field trial data. For potential co occurring exposures in the diet from applications of MMA and DMA on the same crop, 1% co occurrence was used and, as above, all exposures were assumed to be to MMA and then, to DMA. Drinking water estimates were modeled on cotton and turf uses and occupational and residential exposure estimates were based on non chemical specific monitoring data and standard operating procedures ( SOP).

Modeling of the application of arsenical herbicides was performed by EFED to predict acute and chronic concentrations that may reach drinking water. Although there are extensive monitoring data available for arsenic, some of it even targeted to heavy use areas, modeling remains a valuable tool to supplement the limitations of monitoring. Most monitoring measures total arsenic and does not provide information on speciation or the source of contamination. This is particularly important for arsenic, which has multiple potential sources, both from natural background and from various anthropogenic activities. The Estimated Drinking Water Concentrations ( EDWCs) are based on maximum labeled application rates under the most vulnerable circumstances. Sorption of arsenicals varies with soil characteristics, which in turn affects migration through soil to sources of drinking water. Page 8 of 125 Several acute and chronic dietary assessments were performed for the organic arsenicals using field trial data, Food and Drug Administration ( FDA) Total Diet Study ( TDS) data, percent crop treated information, and default processing factors. Since arsenic is ubiquitous in the environment and is usually tested for as total arsenic, it is impossible at this time to differentiate where the arsenic originated from ( i. e., background or from herbicidal use) or to determine speciated residue values for use in a national dietary exposure assessment; therefore, these assessments contain some assumptions that are not standard for dietary exposure assessments. A number of the assumptions that have been made in these assessments are considered to be conservative; however, even when assuming that all arsenic found in the field trials, reported in the FDA TDS, and estimated in drinking water is either MMA or DMA, risks are below HED's level of concern [< 100% Population Adjusted Dose ( PAD)] for the U. S. general population and all population subgroups ( highest 89% aPAD). Commodities that contributed the most to the dietary risk estimates are fish, water, rice, and cereal grains. As discussed above, though it is likely that dietary exposures are a mix of arsenic species, since the toxicity profiles of MMA, DMA, and iAs differ, HED can only provide a range of possibilities by showing potential risks from total MMA exposure and total DMA exposure. Possible risks from iAs exposure are discussed later.

There is a potential for exposure in residential settings during the application process for homeowners who use products containing DMA, CAMA, DSMA, or MSMA. HED uses the term " handlers" to describe those individuals who are involved in the pesticide/ herbicide application process. There is also a potential for exposure from entering DMA, CAMA, DSMA, or MSMA treated areas, such as lawns and golf courses. HED uses the term " postapplication" to describe exposures to individuals that occur as a result of being in an environment that has been previously treated with a pesticide. Cacodylic acid, CAMA, and MSMA/ DSMA can be used in many areas that can be frequented by the general population including residential areas ( e. g., home lawns and gardens). As a result, individuals can be exposed by entering these areas, if they have been previously treated. Risk assessments have been completed for both residential handler and postapplication scenarios.

All risks ( i. e., MOEs) associated with the residential handler scenarios are not of concern; all Margins of Exposure ( MOEs) were > 100 for DMA, CAMA, MSMA, and DSMA.

HED considered a number of exposure scenarios for products that can be used in the residential environment representing different segments of the population including toddlers, youth aged children, and adults. Short term ( 1 30 days) MOEs were calculated for all scenarios. In residential settings, HED does not use restricted entry intervals or other mitigation approaches to limit postapplication exposures, because they are viewed as impractical and not enforceable. As such, risk estimates on the day of application are the key concern. In the assessment for residential postapplication exposure and risk, there are risks of concern for DMA, as they are currently used in a residential environment. In the assessment for residential postapplication exposure and risk, there are risks of concern for DMA, as they are currently used in a residential environment. The endpoint used to assess these incidental oral exposures ( BMDL10) comes from data measured at 10 weeks of DMA exposure in the feed to female rats ( Arnold et al, 1999). However, Cohen et al, ( 2001) shows that regenerative proliferation occurred as early as 1 week into the DMA exposure. HED believes that using the Arnold ( 1999) study ( with the Cohen 2001 Page 9 of 125 study as characterization) in conjunction with Day 0 DMA residues ( calculated from the labeled application rates), constitutes the use of the best available data and that the results can be considered conservative for risk assessment purposes.

For the dermal and inhalation, short and intermediate term exposure, the level of concern ( LOC) or target MOE is 100. Estimated risks above 100 are not of concern. The calculated dermal and inhalation risks were not combined for short or intermediate term exposures because the dermal and inhalation endpoints are based on different toxicological effects. There are no occupational handler scenarios for MMA or DMA that have risks of concern, with some level of mitigation.

HED has determined that there are potential exposures to postapplication occupational workers during usual use patterns associated with DMA. For lawn applications using DMA, the calculated MOE ranges from 22 to 47 on day 0 ( 12 hours following application), and the target MOE is not reached until a week to two weeks after application ( depending on the postapplication activity). All other postapplication scenarios ( for CAMA, DSMA, MSMA, and DMA) have risks below HED's level of concern on day 0 ( 12 hours following application).

Though potential aggregate dietary ( food and water) risks that include exposures from registered uses and background are not of concern, whether exposure is assumed to be to MMA or DMA, residential postapplication exposures to toddlers ( from DMA and CAMA) do present potential risks of concern. Additional exposures to toddlers through the diet would increase these concerns.

The Federal Government and most states have established limits and/ or screening levels for " total arsenic" ( unspeciated) exposure from a variety of sources; drinking water, air, and soil. Typically in monitoring programs, arsenic is measured and reported as total arsenic, regardless of what species ( DMA, MMA, iAs), or mixture of species, may be present, or what the source is. These limits or screening levels are established based on risks ( cancer) from exposure to iAs and technically feasible clean up levels. Under FQPA, the Agency is required to consider all potential sources of exposure to the organic arsenicals, and their metabolites and/ or transformation products. Since there is potential for transformation and exposure to iAs from the registered uses of the organic arsenicals, the potential for risks from exposure to iAs was determined, which included a comparison of estimated exposures from registered uses to existing regulatory limits or screening levels ( see Section 7.7).

Based on the MMA and DMA dietary ( food and water) exposure assessments, HED has determined that only a small amount of the total exposure needs to be from iAs to reach HED's LOC for cancer ( 1x10 6). The Agency's Office of Water has established a Maximum Concentration Level ( MCL) for total arsenic of 10 ppb. EDWCs for exposure to iAs alone may possibly exceed the MCL. Since the MCL was established for total arsenic, exposures to any of the arsenic species in water are potentially subject to regulation.

HED considered the possible in soil conversion of MMA and DMA to iAs to assess risks from postapplication dermal exposures to the soil and from postapplication incidental oral exposures to toddlers ingesting soil. EPA's Office of Solid Waste and Emergency Response's ( OSWER) established a soil screening level ( SSL) of 0.4 ppm for total arsenic ( unspeciated). Using very Page 10 of 125 conservative assumptions that include 100% conversion to iAs and 100% bioavailability, the arsenic levels in soil exceeded the 0.4 ppm SSL for total arsenic in all cases, after one application. HED believes the possibility of exceeding the arsenic SSL would increase with the number of arsenic applications as arsenic in its inorganic form does not degrade and evidence indicates that it may build up in soil overtime as applications are repeated.

2.0 Ingredient Profile 2.1 Summary of Registered Uses A master label was provided for all the chemicals by the MAA Task Force and the uses and rates from this master label were used in the assessment. Note that much higher rates are found on some current end use product labels and these higher rates will need to be reduced to the levels on the master label.

Table 2.1a: Maximum Application Rates obtained from the Master Label for Cacodylic Acid Application Master Label Maximum Application Rate ( lb ai/ A) Applications Per Year Cotton Preconditioning for defoliation 0.3 1 Cotton defoliation 0.8 1 Cotton defoliation 0.6 2 Lawns and Ornamental Turf Lawn renovation 7.3 2 Lawn edging 7.72 4 Ornamentals Ornamentals 7.3 6 Non Crop Areas Non crop 7.3 6 Nonbearing Citrus Ground directed 4.96 3 Page 11 of 125 Table 2.1b: Maximum Application Rates obtained from the Master Label for CAMA Timing of Application/ Use Site Master Label Maximum Application Rate ( lb ai/ A) MMA equivalent ( lb ai/ A) Applications Per Year Turfgrass B Lawns and Ornamental Turf & Turf Grown for Sod By Ground only on athletic fields, golf courses, parks On Bentgrass: 2.5 2.2 2 By Ground on well established actively growing turf On grasses other than Bent: 5 4.4 2 By ground on established Bermuda grass & zoysiagrass 4.182 3.6 4 Note: One broadcast application per year. All additional applications are to be spot treatment only. In Florida all applications   spot treatment only.

Table 2.1c: Maximum Application Rates obtained from the Master Label for DSMA Timing of Application Master Label Maximum Application Rate ( lb ai/ A) MMA equivalent ( lb ai/ A) Maximum Number of Applications Per Crop Cotton By ground or air: pre plant or post plant ( up to cracking) 2.268 1.7 1 By ground or air: post emergent ( as over the top broadcast spray) 2.268 1.7 1 By ground: post emergent ( directed spray application) 2.268 1.7 2 By ground: post emergent ( directed band application) based on 40 inch row spacing) 2.268 1.7 2 Grasses Grown for Seed in Pacific Northwest only ( Ryegrass, Fescue, and Bluegrass) Pacific Northwest apply before boot stage 4.4 3.3 1 Lawns, Ornamental Turf, and Sod Farms By Ground on well established actively growing turf 3.293 2.5 4 Sod Farms 3.293 2.5 4 Nonbearing Orchards and Vineyards Ground directed 4.85 3.7 3 Noncrop Areas Ground application 5.1 3.9 4 Page 12 of 125 Table 2.1d: Maximum Application Rates obtained from the Master Label for MSMA Timing of Application Master Label Maximum Application Rate ( lb ai/ A) MMA equivalent ( lb ai/ A) Maximum Number of Applications Per Crop Cotton By ground or air: pre plant or post plant ( up to cracking) 2.0 1.7 1 1.875 1.6 1 By ground or air: post emergent ( as over the top broadcast spray) 0.9375 0.8 2 By ground: post emergent ( directed spray application) 2.0 1.7 2 Grasses Grown for Seed in Pacific Northwest only ( Ryegrass, Fescue, and Bluegrass)

Pacific Northwest apply before boot stage 6.16 5.3 1 Lawns, Ornamental Turf, and Sod Farms By Ground only on athletic fields, golf courses, parks 2.6136 2.3 4 By Ground on well established actively growing turf 2.178 1.9 4 By ground on established Bermuda grass & zoysiagrass 3.9204 3.4 4 Sod Farms 3.9204 3.4 4 Nonbearing Orchards and Vineyards Ground directed 4 3.5 3 Noncrop Areas Ground application 4.5 3.9 4 Page 13 of 125 2.2 Structure and Nomenclature TABLE 2.2: Test Compound Nomenclature Cacodylic Acid & Sodium Cacodylate Chemical structure Cacodylic Acid Sodium Cacodylate Empirical formula C2 H7 AsO2 / C2 H6 AsNaO2 Common name Cacodylic Acid/ Sodium Cacodylate Other names dimethylarsinic acid, dimethyl arsonate, DMA Molecular Weight 137.99 / 159.99 PC Code 012501 / 012502 CAS Registry Number 75 60 5 / 124 65 2 Chemical Class Organic Arsenic Known Impurities of Concern Unknown MSMA/ DSMA/ CAMA Chemical structure MSMA DSMA CAMA Empirical formula CH4 AsNaO3 / CH3 AsNa2O3 / ( CH4 AsO3 ) 2 Ca Common name MSMA/ DSMA/ CAMA Other names monosodium methanearsonate ( MSMA); disodium methanearsonate ( DSMA), calcium acid methanearsonate ( CAMA), methylarsinic acid, MAA monomethyl arsonate, MMA Molecular Weight 161.94 / 183.92 / 318 PC Code 013803 / 013802 / 013806 CAS Registry Number 2163 80 6 / 144 21 8 / 5902 95 4 Chemical Class Organic Arsenic Known Impurities of Concern Unknown As O C H 3 OH CH 3 As O C H 3 O CH 3 Na +

As OH O O C H 3 Na +

As O O O C H 3 Na + Na +

As O C H 3 O OH 2 Ca 2+ Page 14 of 125 2.3 Physical and Chemical Properties Table 2.3a: Product Chemistry Data Summary for Cacodylic Acid OPPTS Guideline Numbers Data Requirements: Cacodylic Acid [ TGAI] PC Code 012501 CAS# 75 60 5 Master Record Identification [ MRID#] or Reference Are Data Requirements Fulfilled? Results or * Data Gap 830.1550 Product Identity and Composition NO * DATA GAP 830.1600 Description of Materials Used to Produce the Product NO * DATA GAP 830.1620 Description of Production Process NO * DATA GAP 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities NO * DATA GAP 830.1700 Preliminary Analysis 41608302, 42614501 YES 830.1750 Certified Limits NO * DATA GAP 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color 40957813 42473801 YES WHITE 830.6303 Physical State 40957813 42473801 YES CRYSTALLINE SOLID 830.6304 Odor 40957813, 42473801 YES NO ODOR 830.6313 Stability to normal and elevated temperatures, metals and metal ions NO * DATA GAP 830.7000 pH 40957813, 42473801 YES 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range 42397101 YES 192 º C   194 º C 830.7220 Boiling Point/ Boiling Point Range NOT APPLICABLE SEE GUIDELINE 830.7220 830.7300 Density/ Relative Density/ Bulk Density 40957813 42473801 YES 1.10 g / mL 830.7370 Dissociation Constant 42403501 YES 6.17 AT 25 º C 830.7550 Partition coefficient ( n octanol / water) shake flask method 42397101 YES K O/ W = < 0.028 AT 25 º C 830.7560 Partition coefficient ( n octanol / water) generator column method SEE GUIDELINE 830.7550 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography SEE GUIDELINE 830.7550 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 42397101 YES 102 g / 100mL 830.7860 Water solubility generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure NO * DATA GAP Page 15 of 125 Table 2.3b: Product Chemistry Data Summary for Sodium Cacodylate OPPTS Guideline Numbers Data Requirements Sodium Cacodylate [ TGAI] PC Code 012502 CAS# 124 65 2 Master Record Identification [ MRID#] or Reference Are Data Requirements Fulfilled? Results or * Data Gap 830.1550 Product Identity and Composition NO * DATA GAP 830.1600 Description of Materials Used to Produce the Product NO * DATA GAP 830.1620 Description of Production Process NO * DATA GAP 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities NO * DATA GAP 830.1700 Preliminary Analysis 41608302, 42614501 YES 830.1750 Certified Limits NO * DATA GAP 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color 40957813 42473801 YES WHITE 830.6303 Physical State 40957813 42473801 YES CRYSTALLINE SOLID 830.6304 Odor 40957813, 42473801 YES NO ODOR 830.6313 Stability to normal and elevated temperatures, metals and metal ions 42403501 YES STABLE 830.7000 pH 42473801 YES 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range 42403501 YES 77 oC   79.5 oC 830.7220 Boiling Point/ Boiling Point Range NOT APPLICABLE 830.7300 Density/ Relative Density/ Bulk Density 40957813 42473801 YES 1.10 g / mL 830.7370 Dissociation Constant 42403501 YES 6.21 at 25 oC 830.7550 Partition coefficient ( n octanol / water) shake flask method NOT APPLICABLE CRBS 8865, D170691 12/ 12/ 1991 A. Perfetti 830.7560 Partition coefficient ( n octanol / water) generator column method 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography SEE GUIDELINE 830.7550 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 42397101 YES 82 g / 100 mL 830.7860 Water solubility generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure NO * DATA GAP Page 16 of 125 Table 2.3c: Product Chemistry Data Summary for DiSodium Methanearsonic salt OPPTS Guideline Numbers Luxembourg Pamol, Inc. Data Requirements: DSMA [ TGAI] PC Code 013802 CAS# 144 21 8 Master Record Identification [ MRID#] Are Data Requirements Fulfilled? Results or * Deficiency 830.1550 Product Identity and Composition NO * Data Gap 830.1600 Description of Materials Used to Produce the Product 42388301, 44150401 YES 830.1620 Description of Production Process 42388301, 44150401 YES 830.1650 Description of Formulation Process NO * Data Gap 830.1670 Discussion of Formation of Impurities NO * Data Gap 830.1700 Preliminary Analysis 42053701, 45053702 YES 830.1750 Certified Limits NO * Data Gap 830.1800 Enforcement Analytical Method NO * Data Gap 830.1900 Submittal of Samples NO * Data Gap 830.6302 Color 42451102 YES WHITE 830.6303 Physical State 42451102 YES CRYSTALINE SOLID 830.6304 Odor 42451102 YES No Odor 830.6313 Stability to normal and elevated temperatures, metals and metal ions NO * Data Gap 830.7000 pH 41982002 YES 830.7050 UV/ VIS absorption NO * Data Gap 830.7200 Melting Point/ Melting Range 41982001 YES > 300 º C 830.7220 Boiling Point/ Boiling Point Range NOT APPLICABLE 830.7300 Density/ Relative Density/ Bulk Density 42451102 YES 830.7370 Dissociation Constant 41976201 YES 830.7550 Partition coefficient ( n octanol / water) shake flask method 41976202 YES Log P O/ W < 1 830.7560 Partition coefficient ( n octanol / water) generator column method SEE GUIDELINE 830.7550 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography SEE GUIDELINE 830.7550 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 41602502 YES 830.7860 Water solubility, generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure 42120701 YES 0.0000001 mm Hg at 25 ° C Page 17 of 125 Table 2.3d: Product Chemistry Data Summary for DiSodium Methanearsonic salt OPPTS Guideline Numbers APC Holdings Data Requirements: DSMA [ TGAI] PC Code 013802 CAS# 144 21 8 Master Record Identification [ MRID#] Are Data Requirements Fulfilled? Results or * Deficiency 830.1550 Product Identity and Composition NO * DATA GAP 830.1600 Description of Materials Used to Produce the Product 42361001 YES 830.1620 Description of Production Process 42361001 YES 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities 42053701 YES 830.1700 Preliminary Analysis 42053702 YES 830.1750 Certified Limits NO * DATA GAP 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color 42451102 YES 830.6303 Physical State 42451102 YES 830.6304 Odor 42451102 YES NO ODOR 830.6313 Stability to normal and elevated temperatures, metals and metal ions NO * DATA GAP 830.7000 pH 41982002 YES 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range 41982001 YES 830.7220 Boiling Point/ Boiling Point Range SEE GUIDELINE 830.7200 830.7300 Density/ Relative Density/ Bulk Density 42451102 YES 830.7370 Dissociation Constant 41976201 YES 830.7550 Partition coefficient ( n octanol / water) shake flask method 41976202 YES 830.7560 Partition coefficient ( n octanol / water) generator column method 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography SEE GUIDELINE 830.7550 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 41602502 YES 830.7860 Water solubility, generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure 42120701 YES Page 18 of 125 Table 2.3e: Product Chemistry Data Summary for DiSodium Methanearsonic salt OPPTS Guideline Numbers GB Biosciences Corporation Data Requirements: 81% DSMA FI [ Technical] PC Code 013802 CAS# 144 21 8 Master Record Identification [ MRID#] Are Data Requirements Fulfilled? Results or * Deficiency 830.1550 Product Identity and Composition 42051902 YES CSF 09/ 23/ 1991 830.1600 Description of Materials Used to Produce the Product NO * DATA GAP 830.1620 Description of Production Process NO * DATA GAP 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities NO * DATA GAP 830.1700 Preliminary Analysis NO * DATA GAP 830.1750 Certified Limits 42051902, CSF 09/ 23/ 1991 YES 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color NO * DATA GAP 830.6303 Physical State NO * DATA GAP 830.6304 Odor NO * DATA GAP 830.6313 Stability to normal and elevated temperatures, metals and metal ions NO * DATA GAP 830.7000 pH NO * DATA GAP 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range NO * DATA GAP 830.7220 Boiling Point/ Boiling Point Range NO * DATA GAP 830.7300 Density/ Relative Density/ Bulk Density NO * DATA GAP 830.7370 Dissociation Constant NO * DATA GAP 830.7550 Partition coefficient ( n octanol / water) shake flask method NO * DATA GAP 830.7560 Partition coefficient ( n octanol / water) generator column method NO * DATA GAP 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography NO * DATA GAP 830.7840 Water Solubility: Column Elution Method; Shake Flask Method NO * DATA GAP 830.7860 Water solubility, generator column method NO * DATA GAP 830.7950 Vapor pressure NO * DATA GAP Page 19 of 125 Table 2.3f: Product Chemistry Data Summary for MonoSodium Methanearsonic salt OPPTS Guideline Numbers Luxembourg Pamol, Inc Data Requirements: MSMA [ TGAI] PC Code 013803 CAS# 2163 80 6 Master Record Identification [ MRID#] Are Data Requirements Fulfilled? Results or * Deficiency 830.1550 Product Identity and Composition NO * DATA GAP 830.1600 Description of Materials Used to Produce the Product NO * DATA GAP 830.1620 Description of Production Process 41602701, 42387801 YES 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities 41602701, 42387801 YES 830.1700 Preliminary Analysis 42387802 YES 830.1750 Certified Limits NO * DATA GAP 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color 41610001, 42451101 YES WHITE 830.6303 Physical State 41610001, 42451101 YES CRYSTALLINE 830.6304 Odor 41610001, 42451101 YES NO ODOR 830.6313 Stability to normal and elevated temperatures, metals and metal ions 41610001, 42378601 YES 830.7000 pH 41610001, 42378601 YES 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range 41789501 YES 830.7220 Boiling Point/ Boiling Point Range NOT APPLICABLE 830.7300 Density/ Relative Density/ Bulk Density 42451101 YES 1.65 g/ mL at 25 º C 830.7370 Dissociation Constant 41610001 YES 830.7550 Partition coefficient ( n octanol / water) shake flask method 830.7560 Partition coefficient ( n octanol / water) generator column method 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography NO * DATA GAP 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 41610001 YES 830.7860 Water solubility, generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure 41610001, 41651901 YES 0.00001 Pa Page 20 of 125 Table 2.3g: Product Chemistry Data Summary for MonoSodium Methanearsonic salt OPPTS Guideline Numbers APC Holdings, Inc. Data Requirements: MSMA [ TGAI] PC Code 013803 CAS# 2163 80 6 Master Record Identification [ MRID#] Are Data Requirements Fulfilled? Results or * Deficiency 830.1550 Product Identity and Composition NO * DATA GAP 830.1600 Description of Materials Used to Produce the Product 41702001 YES 830.1620 Description of Production Process 41702001 YES 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities 42474101 YES 830.1700 Preliminary Analysis 41702002, 42474101 YES 830.1750 Certified Limits NO * DATA GAP 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color 41610001 YES 830.6303 Physical State 41610001 YES 830.6304 Odor 41610001 YES NO ODOR 830.6313 Stability to normal and elevated temperatures, metals and metal ions 41610001, 4237801 YES 830.7000 pH 41610001, 4237801 YES 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range 41789501 YES 830.7220 Boiling Point/ Boiling Point Range SEE GUIDELINE 830.7200 830.7300 Density/ Relative Density/ Bulk Density 42451101 YES 830.7370 Dissociation Constant 41610001 YES 830.7550 Partition coefficient ( n octanol / water) shake flask method 830.7560 Partition coefficient ( n octanol / water) generator column method 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography NO * DATA GAP 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 41610001 YES 830.7860 Water solubility, generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure 41610001, 41651901 YES Page 21 of 125 Table 2.3h: Product Chemistry Data Summary for MonoSodium Methanearsonic salt OPPTS Guideline Numbers GB Biosciences Corporation Data Requirements: MSMA 59% [ Technical] PC Code 013803 CAS# 2163 80 6 Master Record Identification [ MRID#] Are Data Requirements Fulfilled? Results or * Deficiency 830.1550 Product Identity and Composition 42153501 YES 830.1600 Description of Materials Used to Produce the Product 42081201 YES 830.1620 Description of Production Process 42081201 YES 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities 41608101 YES 830.1700 Preliminary Analysis 41608101 YES 830.1750 Certified Limits NO * DATA GAP 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color NO * DATA GAP 830.6303 Physical State NO * DATA GAP 830.6304 Odor NO * DATA GAP 830.6313 Stability to normal and elevated temperatures, metals and metal ions 41610001, 42378601 YES 830.7000 pH NO * DATA GAP 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range 41789501 YES 830.7220 Boiling Point/ Boiling Point Range SEE GUIDELINE 830.7200 830.7300 Density/ Relative Density/ Bulk Density NO * DATA GAP 830.7370 Dissociation Constant 41610001 YES 830.7550 Partition coefficient ( n octanol / water) shake flask method 830.7560 Partition coefficient ( n octanol / water) generator column method 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography NO * DATA GAP 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 41610001 YES 830.7860 Water solubility, generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure 41610001, 41651901 YES Page 22 of 125 Table 2.3i: Product Chemistry Data Summary for Calcium Methanearsonate OPPTS Guideline Numbers APC Holding Company Data Requirements: CAMA [ TGAI] PC Code 013806 CAS# 5902 95 4 Master Record Identification [ MRID#] Are Data Requirements Fulfilled? Results or * Deficiency 830.1550 Product Identity and Composition NO * DATA GAP 830.1600 Description of Materials Used to Produce the Product 42913801 YES 830.1620 Description of Production Process 42913801 YES 830.1650 Description of Formulation Process NO * DATA GAP 830.1670 Discussion of Formation of Impurities 42913801 YES 830.1700 Preliminary Analysis 42825901 YES 830.1750 Certified Limits NO * DATA GAP 830.1800 Enforcement Analytical Method NO * DATA GAP 830.1900 Submittal of Samples NO * DATA GAP 830.6302 Color 42807602 YES 830.6303 Physical State 42807603 YES 830.6304 Odor 42807604 YES 830.6313 Stability to normal and elevated temperatures, metals and metal ions 42807609 YES 830.7000 pH 42807608 YES 830.7050 UV/ VIS absorption NO * DATA GAP 830.7200 Melting Point/ Melting Range 42807605 YES 830.7220 Boiling Point/ Boiling Point Range SEE GUIDELINE 830.7200 830.7300 Density/ Relative Density/ Bulk Density 42807606 YES 830.7370 Dissociation Constant Memo YES MEMO 09/ 29/ 1995, 07/ 29/ 1993, A. SMITH 830.7550 Partition coefficient ( n octanol / water) shake flask method 830.7560 Partition coefficient ( n octanol / water) generator column method 830.7570 Partition coefficient ( n octanol / water) estimation by liquid chromatography NO * DATA GAP 830.7840 Water Solubility: Column Elution Method; Shake Flask Method 42807607 YES 830.7860 Water solubility, generator column method SEE GUIDELINE 830.7840 830.7950 Vapor pressure NO * DATA GAP Page 23 of 125 3.0 Metabolism Assessment 3.1 Comparative Metabolic Profile Toxicokinetic factors ( i. e., absorption, distribution, metabolism, and excretion) play critical roles in the evaluation of quantitative dose response relationships since these factors influence the amount of chemical at the site of action, along with the time course for exposure at that site. Section 2. C. Toxicokinetics and Metabolism of USEPA, 2005b provides details on the available studies in humans and animals which characterize the metabolism following administration of iAs, MMAV or DMAV. Although species differences exist, these in vivo studies indicate that the methylation/ reduction of iAs to MMAV or DMAV is highly efficient, particularly in rodents and humans. However, when MMAV or DMAV are administered as parent compound, further methylation of MMAV or DMAV is less efficient. The results of the in vivo studies are further supported by the in vitro evidence. Specifically, the in vitro evidence indicates that the cellular absorption of MMAV or DMAV is less than that of iAsV, MMAIII, or DMAIII.

The biomethylation of arsenic involves alternating steps in which trivalent arsenic is oxidatively methylated and then reduced from pentavalency to trivalency ( Figure 3.1). In mammals, the methylation and reduction reactions are enzymatically catalyzed. Some research suggests that distinct methyltransferases and reductases catalyze each step in the pathway that leads from inorganic arsenic to methylated arsenicals, while other investigators have found orthologous genes encoding arsenic (+ 3 oxidation state) methyltransferase ( AS3MT) in the genomes of rat, mouse, and human. AS3MT catalyzes all steps in the pathway from arsenite to mono, di, and trimethylated products.

Less is known about the capacity for the reduction of pentavalent methylated arsenicals into trivalent methylated arsenicals. In assays containing AS3MT, the low rates of conversion of substrates containing pentavalent arsenic into the expected methylated products suggest that unknown factors limit the capacity of the enzyme to reduce the substrate. Similarly, in cultured cells, pentavalent arsenicals are converted to methylated products at much slower rates than are trivalent arsenicals. The low rate of conversion could reflect inefficient reduction of the substrate before oxidative methylation or could reflect the relatively slow uptake of pentavalent arsenicals into cells. . Page 24 of 125 TMAsIII TMAsV Methylation Reduction Figure 3.1: Scheme for the Methylation of As Page 25 of 125 3.1.1 In vivo Metabolism Studies Humans and many other mammals efficiently methylate iAs to mono, di and trimethyl arsenicals. The degree of methylation varies by species ( see more detail in USEPA 2006). Some species such as the guinea pig, marmoset monkey and chimpanzee do not appear to methylate iAs. When humans are exposed to iAs, urinary concentrations of methylated metabolites vary among populations. However, when exposed iAs, particularly in drinking water, human urine typically contains 10 20% iAs, 10 20% MMA, and 60 80% DMA. Humans tend to excrete higher amounts of MMAV ( 10 20%) than do mice (< 1%) after exposure to iAs. Rats and hamsters tend to excrete more TMAO than other species following exposure to DMA. Recent studies have detected the trivalent species of MMA and DMA in human urine following exposure to drinking water contaminated with iAs. Following direct exposure to MMAV and DMAV, these compounds are methylated to a lesser degree by laboratory animals and humans compared to that of iAsV.

Section 2. C. 2 of USEPA 2006 describes the in vivo metabolism of key arsenical compounds. Figures 3.1.1a, 3.1.1b, and 3.1.1c summarize the results of in vivo metabolism studies. In summary, the available in vivo metabolism studies indicate that:

  When exposed directly to iAs, arsenic is efficiently absorbed and methylated in human and laboratory animal tissues.

  Ingested MMAV and DMAV are eliminated more rapidly compared to ingested iAs.

  Studies in laboratory animals indicate little or no demethylation of either MMAV or DMAV ( i. e., production of inorganic arsenic from methylated arsenicals is minimal to nonexistent). Page 26 of 125 Figure 3.1.1a provides a visual representation of some of the key differences between humans and rats regarding exogenous exposure to iAs. iAs is efficiently methylated to MMAV and/ or DMAV.

Figure 3.1.1a: General metabolic profile following direct exposure to iAs.

iAsV Limited cellular uptake iAsIII Extensive cellular uptake iAsIII MMAV MMAs 10 20% of Human urinary excretion MMAII I DMAV DMAIII DMAs 60 80% of Human urinary excretion TMAO TMAO None found in human urine 5 10% of Rat urinary excretion TMA Page 27 of 125 Figure 3.1.1b provides a visual representation of some key differences between humans and rats regarding exogenous exposure to MMAV. Following direct exposure to MMAV, humans and rats excrete MMAV predominately unchanged. Only a portion of MMAV is methylated to DMAV in humans and rats. Excretion of MMAV occurs rapidly compared to excretion of arsenic following exposure to iAs.

Figure 3.1.1b: General metabolic profile following direct exposure to MMAV MMAV Limited cellular uptake MMAV MMAs Excreted primarily unchanged in human urine (> 80%) MMAIII DMAV DMAIII DMAs ~ 12% of Human urinary excretion ~ 20% of Rat urinary excretion TMAO TMAO None found in human urine ~ 5% of Rat urinary excretion TMA Page 28 of 125 Figure 3.1.1c provides a visual representation of some key differences between humans and rats regarding exogenous exposure to DMAV. Following direct exposure to DMAV, humans excrete DMAV predominately unchanged. Rats tend to excrete more TMAO than other species. Excretion of DMAV is more rapid than excretion of arsenic following exposure to iAs or MMAV.

Figure 3.1.1c: General metabolic profile following direct exposure to DMAV DMAV Limited cellular uptake DMAV DMAs: Excreted primarily unchanged in human urine (> 95%) DMAIII TMA TMAO Small amount (~ 4%) in human urinary excretion ~ 20 40% of rat urinary excretion TMAO Page 29 of 125 3.1.2 In vitro Studies There is evidence from in vitro studies which indicates that iAs is more readily taken up by cells compared to the cellular uptake of MMAV and DMAV. Because methylation occurs intracellularly, these studies provide characterization of the biological processes leading to the differences observed in the in vivo metabolism studies. Furthermore, the differential cellular uptake of iAs, MMAV, or DMAV also provides characterization of the potential intracellular exposure contributing to the differential toxicological profiles of the arsenicals.

In each of the in vitro studies ( described in 2. C. 3 of USEPA 2006), cellular uptake of iAsIII and/ or iAsV was shown to be greater than cellular uptake for MMAV and DMAV. In vitro metabolism studies also suggest that reduction of iAsV occurs at a greater rate in vitro than reduction of DMAV, and that MMAIII is readily methylated but MMAV is not. The in vivo metabolism studies described in USEPA 2006 indicate that methylation is more efficient in humans, mice, hamsters, and rats following direct exposure to iAs compared to methylation rates following direct exposure to MMAV and DMAV. The in vitro studies suggest that, at least in part, the differences in in vivo methylation may be related to the degree to which arsenical compounds are taken up into the cell as well as reduced.

3.2 Nature of the Residue in Foods Based on the available data and published information on cacodylic acid, the Metabolism Committee concluded that the only residue of concern is cacodylic acid ( DMA) per se ( Swartz 1995). Little or no demethylation of cacodylic acid is likely to occur in/ on cotton and animal commodities. Submitted plant and animal metabolism data support this finding. However, there are no available data to show how plants metabolize residues taken up from contaminated soils. Monitoring data, which measures total arsenic ( unspeciated), shows measurable amounts of arsenic in foods, including meat and milk.

3.2.1 Description of Primary Crop Metabolism The qualitative nature of MMA residues in plants is adequately understood. Acceptable metabolism studies on citrus and cotton have been submitted by the MAATF and reviewed by the Agency. The citrus and cotton studies were conducted using MSMA labeled with 14C in the methyl group as the test substance. The Agency previously specified that translation of MSMA metabolism studies to DSMA ( and CAMA) is acceptable, according to a Phase 4 response ( Christina Olinger, March 26, 1991). The results of these reviewed studies were presented on December 19, 1994 to the HED Metabolism Committee ( Christina Swartz, January 26, 1995). Based on the metabolism studies conducted by the registrants for MSMA, as well as metabolism data for MSMA and DSMA from published sources, the Committee concluded that the residues of concern ( i. e., that which is of toxicological concern and requires regulation) associated with the use of MSMA, DSMA, and CAMA are MMA per se and DMA expressed as As2O3. This decision was predicated on the low rate or lack of demethylation, and the inability to distinguish between background arsenic and arsenic resulting from pesticide use. Since the Agency is Page 30 of 125 required to consider all sources of arsenic under FQPA, speciated ( MMA, DMA, iAs) monitoring data would be useful.

The qualitative nature of MMA residues in animals is adequately understood based on acceptable ruminant and poultry metabolism studies. The HED Metabolism Committee ( Swartz 1995) concluded that there was no reasonable expectation of finite residues of concern in meat, milk, poultry, and eggs as a result of registered uses; that is, residues in meat, milk, poultry, and eggs could be classified under Category 3 of CFR § 180.6( a). Tolerances and feeding studies are not required at this time. However, if warranted, this will be revisited in the future.

3.3 Environmental Fate Environmental fate laboratory studies show that organic arsenicals are stable under all tested abiotic conditions. Registrant submitted studies of DMA and MMA found both compounds to be stable to hydrolysis at all pHs ( MRID# s 42059201 and 42363001). DMA and MMA were also found to be stable to photolysis in both aquatic and soil environments ( DMA: MRID# s 41662601 & 41662602; MMA: MRID# s 41903902 & 41903901). These conclusions are supported by multiple open literature studies of organic arsenical soil metabolism in which no degradation occurred in sterile control soils ( see Moore 2006).

Organic arsenicals are subject to microbial metabolism in soil under aerobic or anaerobic conditions. The occurrence, rate, and products of this metabolism are variable, dependent on environmental conditions. The observed persistence of organic arsenicals in aerobic soil has ranged from weeks to years, depending on soil properties and ambient conditions such as soil moisture, temperature, chemical concentration, and amount of organic matter ( Moore 2006). The extreme of this range is seen in several registrant submitted studies of microbial metabolism which observed no transformation at all ( MRID# s 42616001, 42572601, 43036101). These studies demonstrate that there are conditions in which metabolism does not occur, possibly due to non viable soils, but there is well established evidence of organic arsenical metabolism in many environments. Therefore, this assessment is based on the understanding that transformation of organic arsenicals is an important, although variable, process.

Adding to the complexity is that metabolism rates do not appear to depend linearly on organic arsenical concentration; in some studies, degradation decreased with increasing concentration while in others, concentration had no effect on degradation. Hence, the kinetics is not necessarily first order, and " half life" is therefore not necessarily an appropriate constant for all concentrations. Keeping this uncertainty in mind, EFED calculated first order half lives to use in the exposure modeling and as a convenient measure to compare results from laboratory studies. Based on several studies showing estimated first order " half lives" in aerobic and anaerobic soils ranging from months to nearly a year, a calculated aerobic soil half life of 240 days was used in modeling for both DMA and MMA ( see Moore 2006).

Some of the variability in degradation processes is associated with variability in sorption processes. Soil microbial degradation of organic arsenicals only occurs while the compounds Page 31 of 125 remain dissolved in pore water. As the arsenicals sorb to soil, they become less accessible to microbes and therefore less likely to be degraded. Sorption variability is largely controlled by soil properties including the clay content, the iron and aluminum content, and the soil pH. It has also been shown that microbial activity can slow sorption. With changing environmental conditions, arsenicals can also desorb and become available for degradation, although it has been shown that over time, sorbed arsenic species become more tightly bound to soil.

The effects of other environmental factors on the rate of organic arsenical degradation are complex and poorly defined with different studies leading to conflicting results. An increase in temperature has been shown to lead to increased degradation, but results on the impact of soil organic matter or applied organic arsenical concentrations are contradictory. The influence of aerobic versus anaerobic conditions on degradation rates is also ambiguous. What is consistent, in both literature and submitted fate studies, is the great influence of soil environmental conditions on transformation rates.

3.3.1 Degradation ( Metabolites)

Potential metabolites of applied DMA and MMA include volatile alkylarsines and inorganic arsenic ( as arsenate or arsenite) along with carbon dioxide. Cacodylic acid may be present as a metabolite of MMA as well as an applied parent compound. The major metabolites identified in published sources and registrant submissions are inconstant sometimes detected and sometimes not. They also occur in widely variable proportions. Reasons for this are unclear, but are most likely associated with the exquisite sensitivity to the ambient conditions mentioned above. Regardless, it is crucial not to confuse transformation with detoxification. These arsenicals and their transformation products, in combination with arsenic from the natural background and from other anthropogenic sources, maintain the total, immutable arsenic environmental load. Arsenic from pesticides is not lost but redistributed and transformed throughout the environment ( plants, animals, air, soil, sediment, water) into other arsenic containing substances.

The only metabolism pathway that could directly reduce soil arsenic loading is transformation to volatile alkylarsines. Microbial species capable of metabolizing dissolved organic arsenical compounds to gaseous arsines have been identified and dimethylarsine and trimethylarsine are the most likely volatile products of soil metabolism. Metabolism to volatile alkylarsines is possible under certain conditions but, is generally not likely to be a major route of dissipation. The possibility of volatilization was therefore not included in calculations on the fate of applied organic arsenical pesticides.

Other routes of metabolism include methylation and demethylation. DMA has two methyl groups attached to a central arsenic, MMA has one, and inorganic arsenic has none. Theoretically, any of the methyl groups on DMA or MMA are subject to removal, while one methyl group could be added to convert inorganic arsenic to MMA which could be further methylated to DMA. However, not all of these transformations are likely to occur ( see Moore 2006). Studies show that to a varying degree, MMA may lead to both DMA and inorganic arsenic as end products. Although fewer speciated studies are available for DMA, it appears that Page 32 of 125 it can degrade to inorganic arsenic but no transformation to MMA is expected. There is some uncertainty associated with all studies relying on speciation of soil arsenic due to limitations in extraction and analytical techniques. Arsenical species may be transformed to some extent during the process of extraction and measurement. This is not an issue when results are reported as total arsenic, as done in many studies, but those results are less useful in a discussion of metabolites.

Inorganic forms of arsenic are more toxic than the organic forms, so it is very important to assess the possibility of transformation/ mineralization of organic arsenical pesticides to arsenate [ AsV] and arsenite [ AsIII]. As with all organic arsenical degradation processes, conversion to inorganic arsenic is extremely variable. Results of multiple studies range from no mineralization to approximately 80% mineralization. Monitoring of residual arsenic in areas where organic arsenical pesticides have been applied support the conclusion that significant conversion to inorganic arsenic can occur.

3.3.2 Mobility In Air. Based on physical properties tabulated above in section 2.0, volatilization of parent materials would not expected to be a significant route of dispersal. Consistent with this expectation, volatilization of parent was not reported in any lab study. However, as mentioned above, volatile arsines produced by metabolism are part of the global arsenic transformation and transport cycle.

In Soil. Sorption to numerous diverse soils varies tremendously but indicates intermediate to low mobility. Sorption appears to be independent of organic matter content; rather, it is higher in soils with higher percentages of clay or with more iron or aluminum content. pH could have a major influence on sorption because of the anionic nature of the tested chemicals. However, available data show that in the more environmentally relevant range of pHs from 5 to 8.5, sorption of organic arsenicals should not decrease ( increase mobility) dramatically with pH when compared to the much larger variability in soil sorption found with different types of soils.

3.3.3 Soil Buildup/ Persistence The relative immobility of arsenicals along with arsenic's elemental nature lends to buildup in soil after repeated applications an important consideration. Arsenic does not break down; it can only be redistributed through runoff, leaching, erosion, volatilization, or plant uptake. Arsenic sorbs strongly to soil so significant leaching is unlikely in most conditions and the potential for runoff is likely to decrease over time. Volatilization is also likely only in specific circumstances, leaving soil erosion and plant uptake as the sole routes of dissipation of organic arsenicals applied to soil.

Submitted studies ( reviewed by EFED) show that, except for at high application rates, a single year of application is unlikely to lead to significant buildup of soil arsenic, but they show that a large fraction of applied arsenic remains in the top layers of soil. After repeated applications for Page 33 of 125 multiple years, then, soil arsenic levels could be expected to increase, making the possibility of soil buildup a long term concern.

Because long term impacts are of concern, it is important to look at studies conducted over a longer period of time. A review of the open literature by EFED found several long term field dissipation studies with some reporting no arsenic buildup despite very high application rates and others finding substantial buildup at rates similar to current labels. Additional information about the potential for arsenic soil buildup comes from monitoring studies in areas where organic arsenicals are known to be used. Levels of soil arsenic were found to be higher than background arsenic levels in several Florida golf courses and in highway rights of way in Louisiana. These results are inconclusive as to the source of the arsenic buildup, but they add to the weight of evidence from controlled field studies and modeling.

Soil accumulation values are generated by PRZM as part of the process of modeling runoff concentrations. PRZM was run with a modified version of the pe4 v01 shell program to estimate soil accumulation ( see Moore 2006). With some exceptions, the modeling inputs were the same as those described for surface water modeling ( see Moore 2006). Maximum application rates for MMA on turf and cotton and for DMA on turf were used and the modeling assumed median sorption. Because of limitations in the available data and modeling capabilities, soil concentrations were modeled as total arsenic, rather than speciated forms. Application rates were therefore calculated to represent applied arsenic and infinite half lives were used to capture all forms of arsenic that may be present. A wide range of sorption is possible; lower sorption, used to provide protective estimates for surface water modeling, would lead to lower soil concentrations, while greater sorption leading to higher concentrations is also possible. The possibility of transformation to volatile species was not included in modeling, and modeling does not account for plant uptake. The results presented are for the scenarios that led to the highest soil concentrations ( PA turf and NC cotton).

In the top 10 cm of soil, modeling predicts that arsenic will accumulate with very little dissipation for several years and then level off. Over the long term, the buildup of total arsenic from MMA application is predicted to reach chronic concentrations of approximately 13 ppm and 45 ppm on cotton and turf, respectively. For DMA on turf, the highest application rate leads to a modeled chronic soil concentration of approximately 77 ppm, assuming annual application at that rate. The application rate for other non crop uses is significantly higher than that for turf. For DMA on cotton, the chronic soil concentration is 2 ppm. " Chronic" concentrations are the upper 90th percentile confidence limit on the annual average, or the 1 in 10 year peak annual concentration. If deeper soils are included, the overall concentrations would be lower. Most studies suggest that concentrations are highest in the surface layers and buildup is typically limited to the top 30 cm.

The same issue of arsenic buildup, supported for soil by field studies, monitoring, and modeling, is relevant to concentrations of arsenic in sediment. Arsenic that reaches surface water is likely to end up in sediments. A registrant study in an aerobic aquatic/ sediment system found that after 30 days, 25% of applied DMA was found in the sediment ( MRID# 43036101). For MMA, 39% Page 34 of 125 of the applied amount ended up in sediment after 30 days, with most of it out of the water within the first week ( MRID# 43314801). In an anaerobic system, after 1 year 61 to 95% of applied MMA was found in the sediment ( MRID# 44767602). For DMA, approximately 95% of the applied amount was found in the sediment after one year, with most of it reaching there within the first month ( MRID# 42572601). A literature review of arsenic fate reported that in Lake Michigan, arsenic concentrations in water were generally much less than in the sediments, and referred to oceanic sediments as " the ultimate sink for arsenic" ( Moore 2006).

4.0 Hazard Characterization/ Assessment 4.1 Overview and Background The text and tables below were summarized or extracted from various sources including data evaluation records developed for the studies noted below for MMA and DMA, EPA's special metabolism and mode of action paper on DMA ( USEPA 2006) , and the scientific literature. EPA's special metabolism and mode of action paper on DMA ( USEPA 2006) provides a detailed description of the metabolic profiles of MMA and DMA in most mammals, including rodents and humans; the mode of action for the development of rat bladder tumors; the human relevance of the animal mode of action; and the dose response considerations for DMA's mode of action. The current document provides only a brief summary of the information contained in the special issue paper. For details regarding these topics, including the benchmark dose analysis for DMA, the reader is referred to   USEPA ( 2006). Revised Science Issue Paper: Mode of Carcinogenic Action for Cacodylic Acid ( Dimethylarsinic Acid, DMAV) and Recommendations for Dose Response Extrapolation. January 30, 2006.

Toxicokinetic factors ( i. e., absorption, distribution, metabolism, and excretion) play critical roles in the evaluation of quantitative dose response relationships since these factors influence the amount of chemical at the site of action, along with the time course for exposure at that site. The in vivo metabolism of inorganic arsenic and its methylated forms involves alternating steps in which trivalent arsenic is oxidatively methylated and then reduced from pentavalency to trivalency ( Figure 3.1a). This process occurs inside the body in a primarily one way direction such that direct exposure to MMA or DMA is not expected to lead to internal exposure to inorganic arsenic. Data from in vivo and in vitro metabolism and pharmacokinetic ( PK) studies with various species indicate that the cellular uptake and efficiency of methylation differs by the administered or exogenous arsenical compound. Because of the predominately one directional nature of the pathway in mammals, following direct exposure to pentavalent MMA or pentavalent DMA ( e. g., MMAV or DMAV, respectively) the number of biologically active metabolic products is expected to be smaller compared to direct ingestion of iAs ( Figure 3.1a). For example, environmental exposure to pentavalent iAs ( e. g., iAsV) may result in an internal mixture of multiple biologically active metabolic products [ iAsV, iAsIII, MMAV, MMAIII, DMAV, DMAIII, and TMAO)]. However, following ingestion of DMAV, metabolism to DMAIII Page 35 of 125 and TMAO can occur ( Figure 3.1a). Thus, the toxicokinetics and toxicodynamics for MMAV and DMAV are simpler compared to the internal mixture following exposure to iAs.

In vivo and in vitro toxicity studies indicate that the various arsenical compounds have distinct toxicological profiles. For example, exposure to high levels of inorganic arsenic in drinking water results in a variety of adverse health effects including diabetes mellitus, cardiovascular disease, renal disease, vascular skin lesions and cancer, and lung, liver and bladder cancer. Long term animal studies with MMA suggest that the large intestine is the target organ with no neoplastic lesions observed at any site. DMA causes bladder tumors in rats after feeding or drinking water exposures. Many of the toxicological activities of the pentavalent and trivalent arsenical compounds are shown in Figure 3.1a. Because of the distinct PK and pharmacodynamic ( PD) differences that are observed following direct oral exposure to MMA and DMA, it is appropriate to use chemical specific data for extrapolating risk for these pesticides.

Under the FQPA, only those chemicals with a common mechanism of toxicity are considered in cumulative risk assessment. In the case of the DMA, the mode of action for the development of bladder tumors in rats has been elucidated. Understanding the mode( s) of action for inorganic arsenic is complicated by the mixture of toxic metabolites that result in vivo. The mode or mechanism of action for cancer and/ or non cancer effects from exposure to inorganic arsenic and from direct exposure to MMA have not yet been elucidated. Some have hypothesized that multiple modes of action may influence the toxicity of inorganic arsenic. Moreover, because of the PK and PD differences noted above, inorganic arsenic, MMA, and DMA are not expected to exhibit the same mode or mechanism of toxicity. Thus, the risk to direct, exogenous exposure to MMA and DMA should not be summed in a cumulative risk assessment.

4.2 MMA 4.2.1 Database Summary The database of toxicology studies for MMA is adequate for risk assessment purposes. No additional studies are required at this time. As MMA is an in vivo metabolite of inorganic arsenic, there is extensive data evaluating the pharmacokinetics and metabolism of MMA in various species in addition to extensive in vitro metabolism and toxicity studies. Acceptable animal toxicity studies include: subchronic dermal toxicity, chronic toxicity following oral exposure in rodents and non rodents, developmental toxicity in rat and rabbit, reproductive toxicity, and genotoxicity/ mutagenicity. There are no acute studies in animals which studied sub lethal doses. However, an acute study is not required at this time since clinical signs consistent with acute toxicity were noted within 2 5 hours of each days dosing in the first week of the dog study. A subchronic toxicity study via the inhalation route is not available for MMA or the pesticidal salts ( i. e.; MSMA, DSMA, and CAMA). This study is not required at this time. It is preferred to use route specific and chemical specific studies in the risk assessments. For screening purposes, an inhalation study with DMA where port of entry effects of the nasal turbinates were noted is being using as surrogate data for MMA. There are no studies which Page 36 of 125 observed toxic effects of MMA in humans and there are no epidemiology studies with MMA. There is one metabolism study where human subjects ingested MMA and urinary metabolites were measured ( Buchet et al, 1981).

4.2.2 Toxicological Effects The target organs following oral exposure of MMA are believed to be the gastrointestinal tract, particularly the large intestine. Effects such as histopathology of the cecum, rectum, and/ or colon were noted as the most sensitive effects in chronic exposure to rats. Diarrhea and vomiting, suggesting irritation of the gastrointestinal tract were noted in the chronic dog study in the first week of dosing and continued throughout the study. Histopathology of the kidney was also noted in the dog and mouse after chronic exposure.

Following 21 days of dermal exposure in rabbit to MMA, there were no toxicologically relevant effects noted systemically or dermally up to 1000 mg/ kg/ day.

As stated above, no neurotoxicity studies are available for MMA at this time. There is no evidence of neurotoxicity observed in rat, rabbit, or dog. In the 104 week oncogenicity study in mice, at high doses ( 46 and 104 mg/ kg/ day), female mice exhibited increased incidences of hypersensitivity and tonic convulsions. At the same dose, body weight gain, increased water consumption, and histopathology of the large intestine and kidney were also noted in mice, suggesting significant toxicity to the animals. It is also notable that the hypersensitivity and tonic convulsions were at doses approximately 20 fold higher than those resulting in clinical signs and kidney histopathology observed in the dog.

There is no quantitative or qualitative evidence of increased susceptibility of rats or rabbit fetuses to in utero exposure in available developmental toxicities. In the rabbit developmental toxicity study, developmental variations were observed at doses similar to those resulting in maternal toxicity. These developmental effects included an increased incidence of skeletal variations in the numbers of 13th thoracic vertebra with ribs and 8th lumbar vertebra at 12 mg/ kg/ day. At 12 mg/ kg/ day, abortions in two rabbits were attributed to decreased body weight gain ( mean  75% compared to control). The maternal toxicity LOAEL is 12 mg/ kg/ day, based on decreased body weight, food consumption ( during the dosing period), and abortions. The maternal toxicity NOAEL is 7 mg/ kg/ day. The developmental NOAEL is 7 mg/ kg/ day. In the rat developmental toxicity study, developmental effects were observed at doses greater than maternally toxic doses. In the rat developmental toxicity study, the developmental NOAEL of 100 mg/ kg/ day is based on decreased fetal body weight observed at 500 mg/ kg/ day. The maternal NOAEL of 10 mg/ kg/ day is based on decreased body weight gains and food consumption observed at 100 and 500 mg/ kg/ day.

Results of reproductive toxicity studies with MMA indicate that effects on reproductive performance occur only at high doses, higher than those resulting in gastrointestinal and kidney effects. In the reproductive toxicity study, whole litter loss was noted in the 300 ppm ( F2 generation only) and 1000 ppm dose groups ( F1 and F2; approximately 21.2 mg/ kg/ day and Page 37 of 125 75.8/ 88.6 mg/ kg/ day, respectively). At doses similar to those used in the reproductive toxicity study, in the chronic rat toxicity study, beginning at week 4 5, diarrhea was observed in all rats at 1000 ppm and in 27/ 60 males and 45/ 60 females of the 400 ppm groups. The observations in the chronic rat study suggest that the rats in the reproductive toxicity study may have experienced significant toxicity. There are two literature studies ( Lopez and Judd, 1979; Prukop and Savage, 1986) which observed reproductive performance in mice. These studies provide information regarding overall characterization, but are not useful for dose response assessment due to the sparsity of information provided and high doses used. For example, Lopez and Judd ( 1979) observed smaller nest building in mice exposed to 477 ppm of MSMA in tap water for 14 days. In the oncogenicity study with mice, histopathology of the large intestine and kidney was noted at a dose lower ( 200 ppm) than used by Lopez and Judd ( 1979). In a different study, Prukop and Savage ( 1986) performed a one generation reproduction study in mice using doses that are approximately 5 and 50 fold higher than the point of departure selected by EPA for use in risk assessment for chronic dietary and short/ intermediate term incidental oral exposure.

MMA is classified as " not likely" a human carcinogen. Studies in rats and mice did not show an increased tumor incidence at any tissue site in either species. The results of these studies have also been summarized by Arnold et al., ( 2003). In a recent study, Shen et al., ( 2003) exposed male rats to MMA at 0, 50, or 200 ppm in drinking water for 104 weeks. Although incidence of GST P positive foci in the liver, and urinary bladder hyperplasia, were observed in MMA treated animals, there was no increase incidence in tumors at any tissue site. The acceptable genetic toxicology studies indicate that MAA is not mutagenic in bacteria ( Salmonella typhimurium ) or cultured mammalian cells ( Chinese hamster ovary). Similarly, MMA did not induce unscheduled DNA synthesis ( UDS) in primary rat hepatocytes. TABLE 4.2.2a: Profile of Subchronic, Chronic, and Other Toxicity of MMA and Cacodylic Acid MMA Cacodylic Acid Guideline #

/ Study Type MRID# ( year)

/ Classification/ Doses Results MRID# ( year)

/ Classification/ Doses Results 870.3100 90 Day oral toxicity 40632601 ( 1985)

Unacceptable/ Nonguideline 0, 10, 100, 500, and 1250 ppm ( 0,

2.1, 22.5, 110.6, and 288.6 mg/ kg/ day for males and 0, 2.8,

27.5, 137.4, and 342.5 mg/ kg/ day for females)

MMA In mice Based on the data presented in this study, a LOAEL and NOAEL can not be established. The numerous deficiencies in the conduct of this study preclude meaningful evaluation of the data. 42767701 ( 1987)

Acceptable/ Guideline males: 0, 0.4, 4.0, 43.2 mg/ kg/ day females: 0, 0.4, 4.5, 45.7 mg/ kg/ day In rats NOAEL = 0.4 mg/ kg/ day LOAEL = 4 ( males) and 4.5 ( females)

mg/ kg/ day based on increased incidence of cuboidal to columnar epithelial lining thyroid follicles and increased water consumption and urine output and decreased specific gravity; and decreased hematology parameters in females.

870.3200 21/ 28 Day dermal toxicity 41872701 ( 1991)

Acceptable/ Guideline 0, 100, 300, or 1000 mg/ kg/ day MMA In rabbits Systemic toxicity NOAEL = 1000 Systemic toxicity LOAEL > 1000 Dermal irritation NOAEL = 1000 Dermal irritation LOAEL > 1000 41872801 ( 1991)

Acceptable/ Guideline 0, 100, 300, 1000 mg/ kg/ day In rabbits NOAEL = 300 mg/ kg/ day LOAEL = 1000 mg/ kg/ day based on decreased body weight gains in females, and decreased testicular weights, hypospermia and tubular hypoplasia in males.

870.3465 90 Day inhalation toxicity Not available for MMA 44700301 ( 1994)

Acceptable/ Guideline 0, 10, 34, 100 mg/ m3 0. 0.01, 0.03, 0.10 mg/ L In rats NOAEL = 0.010 mg/ L/ day LOAEL = 0.034 mg/ L/ day in both male and female rats based on the presence of moderate and marked intracytoplasmic eosinophilic granules ( IEG) in the cells of the nasal turbinates.

870.3700a Prenatal developmental 41926401 ( 1990)

Acceptable/ Guideline 0, 10, 100, or 500 mg/ kg/ day MMA In rats Maternal toxicity NOAEL = 10 mg/ kg/ day.

Maternal toxicity LOAEL = 100 mg/ kg/ day,

based on decreased body weight gain and food consumption.

Developmental toxicity NOAEL= 100 mg/ kg/ day. Developmental toxicity LOAEL = 500 mg/ kg/ day, based on decreased mean fetal body weight. 4062701 ( 1988)

Acceptable/ Guideline 0, 4, 12, 36 mg/ kg/ day ( gavage)

In rats Maternal NOAEL = 12 mg/ kg/ day LOAEL = 36 mg/ kg, based on decreased body weights, body weight gains, food consumption and gravid uterine weight.

Developmental NOAEL = 12 mg/ kg/ day LOAEL = 36 mg/ kg, decreased fetal weights,

shorter crown rump length, the suggestion of diaphragmatic hernia and delayed/ lack of ossification of numerous bones. TABLE 4.2.2a: Profile of Subchronic, Chronic, and Other Toxicity of MMA and Cacodylic Acid MMA Cacodylic Acid Guideline #

/ Study Type MRID# ( year)

/ Classification/ Doses Results MRID# ( year)

/ Classification/ Doses Results 870.3700b Prenatal developmental 15939001 ( 1986)

Acceptable/ Guideline 0, 1, 3, 7, 12 mg/ kg/ day MMA In rabbits Maternal toxicity NOAEL = 7 mg/ kg/ day.

Maternal toxicity LOAEL = 12 mg/ kg/ day,

based on decreased body weight, food consumption ( during the dosing period),

and abortions. Developmental toxicity NOAEL = 7 mg/ kg/ day. Developmental toxicity LOAEL = 12 mg/ kg/ day, based abortions and on an increased incidence of skeletal variations ( increased numbers of 13th thoracic vertebra with ribs and 8th lumbar vertebra). 40663301 ( 1988)

Acceptable/ Guideline 0, 3, 12, 48 mg/ kg/ day ( gavage)

In rabbits Maternal NOAEL = 12 mg/ kg/ day LOAEL = 48 mg/ kg/ day, based on mortality,

abortions, body weight loss and reduced food consumption. Developmental NOAEL = 12 mg/ kg/ day LOAEL was not established, since no pregnant rabbit survived to the gestation day 29 scheduled sacrifice.

870.3800 Reproduction and fertility effects 43178301 ( 1994)

Acceptable/ Guideline 0, 100, 300, or 1000 ppm.

F0: 5.8, 17.8, and 63.5 mg/ kg/ day,

respectively, for males and 7.5,

22.5, and 77.6 mg/ kg/ day for females.

F1: 6.5, 21.1, and 75.8 mg/ kg/ day,

respectively, for males and 7.9,

25.4, and 88.6 mg/ kg/ day for females.

MMA In rats Parental NOAEL = 100 ppm for males and 300 ppm) for females.

Parental LOAEL = 300 ppm for male rats and 1000 ppm for female rats based on increased food consumption with decreased body weight gain along with whole litter loss. Reproductive NOAEL = 300 ppm.

Reproductive LOAEL > 300 ppm.

Offspring NOAEL = 100 ppm.

Offspring LOAEL = 300 ppm based on increased pup death ( day 0 21), reduced litter survival index, and decreased lactation index related to whole litter loss. 41059501 ( 1989)

Acceptable/ Guideline Males: 0, 0.31, 2.16, 15.5 mg/ kg/ day Females: 0, 0.38, 2.48, 17.86 mg/ kg/ day In rats Parental/ Systemic NOAEL = Females: 2.48 mg/ kg/ day LOAEL = Females: 17.86 mg/ kg/ day, based on decreased absolute and relative ovarian weights and increased incidence of thyroid follicles lined with cuboidal to columnar epithelium in females only.

Reproductive NOAEL = Females: 17.86 mg/ kg/ day LOAEL was not established Offspring toxicity: There was no suggestive evidence of offspring toxicity in either generation. TABLE 4.2.2a: Profile of Subchronic, Chronic, and Other Toxicity of MMA and Cacodylic Acid MMA Cacodylic Acid Guideline #

/ Study Type MRID# ( year)

/ Classification/ Doses Results MRID# ( year)

/ Classification/ Doses Results 870.4200b Chronic toxicity 40546101 and 41266401 ( 1988)

Acceptable/ Guideline 0, 2.5, 10, 40 mg/ kg/ day ( week 1 only)

0, 2, 8, and 35 mg/ kg/ day ( week 2

52) MMA In dogs NOAEL = 2 mg/ kg/ day.

LOAEL = 8 mg/ kg/ day based on based on body weight gain and kidney effects ( organ weight and histopathology) in females in both sexes 41490901 ( 1989)

Acceptable/ Guideline 0, 6.5, 16, 40 mg/ kg/ day ( gavage)

In dogs NOAEL = 16 mg/ kg/ day LOAEL = 40 mg/ kg/ day based on salivation,

vomiting, diarrhea, and decreased body weight gains in males and females; and decreased HCT%, HgB, RBC counts, total protein and albumin in males.

Benchmark Dose Estimates for Bladder Effects ( as described in DMA MOA Paper,

USEPA, 2005b)

Tumors 104 weeks BMD10 =

7.74 mg/ kg/ day BMDL10 =

5.96 mg/ kg/ day 870.4300 Combined Chronic/

Carcinogenicity 41669001 ( 1990)

Acceptable 0, 50, 400 and 800 1300 ppm ( 0,

3.2, 27.2, and 93.1 mg/ kg/ day for males and 0, 3.8, 32.9, and 101.4 mg/ kg/ day for females) for 104 weeks.

MMA In rats NOAEL = 50 ppm ( 3.2 mg/ kg/ day for males and 3.8 mg/ kg/ day for females)

LOAEL = 400 ppm ( 27.2 mg/ kg/ day for males and 32.9 mg/ kg/ day for females)

based on decreased body weights, body weight gains, food consumption,

histopathology of gastrointestinal tract and thyroid.

Dosing was considered adequate. 41862101 ( 1989)

Acceptable/ Guideline Males: 0, 0.14, 0.73, 2.80, 7.30 mg/ kg/ day Females: 0, 0.16, 0.79, 3.20, 8.0 mg/ kg/ day In rats Hyperplasia 10 weeks BMD10 =

2.00 mg/ kg/ day BMDL10 =

1.54 mg/ kg/ day 870.4300 Carcinogenicity 42173201 ( 1991)

Acceptable 0, 10, 50, 200, and 400 ppm ( 0,

1.8, 9.3, 38, and 83 mg/ kg/ day for males and 0, 2.2, 12, 46, and 104 mg/ kg/ day for females)

MMA In mice NOAEL = 50 ppm ( 9.3 and 12 mg/ kg/ day)

for males and females.

LOAEL = 200 ppm ( 38 and 46 mg/ kg/ day)

for males and females based on decrease in body weight gain, increased water consumption, and histopathology of the kidney.

Dosing was considered adequate. 41914601 ( 1990)

Unacceptable Males: 0, 1.47, 7.0, 35.25, 91.95 mg/ kg/ day Females: 0, 1.7, 8.65, 43.15, 97.0 mg/ kg/ day In mice NOAEL = 1.7 ( Females) and 7 ( Males)

mg/ kg/ day LOAEL = 8.65 ( Females) and 35.25 ( Males)

mg/ kg/ day based on vacuolar degeneration of bladder epithelium. TABLE 4.2.2a: Profile of Subchronic, Chronic, and Other Toxicity of MMA and Cacodylic Acid MMA Cacodylic Acid Guideline #

/ Study Type MRID# ( year)

/ Classification/ Doses Results MRID# ( year)

/ Classification/ Doses Results 870.5100 Gene mutation Salmonella typhimurium reverse gene mutation 41651902 ( 1989)

Acceptable/ Guideline In deionized distilled water at concentrations of 667, 1000, 3333,

6667 and 10,000 µ g/ plate in the presence and absence of mammalian metabolic activation ( S9 mix). MMA There was no evidence of induced mutant colonies over background.

870.5300 Gene mutation Mouse lymphoma assay 41651904 ( 1989)

Acceptable/ Guideline In deionized water at concentrations of 300, 400, 534,

712, 949, 1266, 1688, 2250, 3000 and 4000 µ g/ mL in the absence of mammalian metabolic activation ( S9 mix) and at concentrations of 71, 95, 127, 169, 225, 300, 400,

534, 712, 949, 1266 and 1688 µ g/ mL in the presence of S9 mix.

MMA MMA was tested up to cytotoxic concentrations. There was no evidence of induced mutant colonies over background.

870.5375 Chromosomal aberration Mouse micronucleus assay 41651903 ( 1989)

Acceptable/ Guideline In distilled water in two independent assays.

Concentrations tested in the initial assay were 625, 1250, 2500, 5000 µ g/ mL,

with and without metabolic activation ( S9 mix). MMA MMA was tested up to a slightly cytotoxic concentration, limited by solubility in the solvent, distilled water. There was no evidence of chromosomal aberrations induced over background. Numerous mutageniticy and genotoxicity studies with DMA and DMAIII. These are described in detail in USEPA, 2005b ( See Table B4 in the DMA MOA paper).

Overall, DMA ( cacodylic acid) is not a direct acting mutagen. TABLE 4.2.2a: Profile of Subchronic, Chronic, and Other Toxicity of MMA and Cacodylic Acid MMA Cacodylic Acid Guideline #

/ Study Type MRID# ( year)

/ Classification/ Doses Results MRID# ( year)

/ Classification/ Doses Results 870.5550 Unscheduled DNA Synthesis 41651905 ( 1989)

Acceptable/ Guideline In deionized distilled water at concentrations of 10, 50, 100, 500,

750 and 1000 µ g/ mL for 18 to 20 hours in an initial and a confirmatory assay. MMA There was no evidence that unscheduled DNA synthesis, as determined by radioactive tracer procedures [ nuclear silver grain counts] was induced.

870.7485 Metabolism and pharmacokinetics 42010501 ( 1991)

Acceptable/ Guideline In water at concentrations of 0, 5.0,

or 200.0 mg/ kg according to the following five different dose groups: 1) In the vehicle control group, dosed with water by gavage; 2) a single radiolabeled gavage dose of 5.0 mg/ kg; 3) a single radiolabeled gavage dose of 200 mg/ kg; 4) dosed by gavage for 14 consecutive days with unlabelled MSMA at 5.0 mg/ kg/ day followed by a single radiolabeled dose of MSMA at MSMA; 5) a single radiolabeled i. v. dose of 5.0 mg/ kg.

MSMA in rats Analysis of fecal and urinary samples by HPLC and TLC revealed that the radioactivity of all preparative fractions was associated with parent compound and two unknown metabolites. The major product excreted in both urine and feces was unchanged parent, accounting for 80 97%

of the administered dose. 42341301 & 43005801 ( 1992)

Acceptable/ Guideline Doses: 0, 5.0 and 50.0 mg/ kg In rats Over a 7 day period 90  98% of total dose was excreted. Total radioactivity recovered in the urine, feces and exhaled air was 28

82, 4  33, and 0  0.1%, respectively.

870.7600 Dermal penetration Not available for MMA 43497401 ( 1994)

Acceptable/ Guideline Dose: 0, 0.90, 9.30, or 91.3 µ g/ cm2 In rats 10 hour dermal absorption is 3.5% Page 43 of 125 TABLE 4.2.2b: Acute Toxicity of MSMA Guideline No. Study Type MRID# s Results Toxicity Category 81 1 Acute Oral, rat 45405601* LD50 = 2449 mg/ kg ( F) 3184 mg/ kg ( M) 2833 mg/ kg ( Combined) III 81 2 Acute Dermal, rabbit 41890001* LD50 > 2000 mg/ kg III 81 3 Acute Inhalation, rat 42604601* LC50 = 2.20 mg/ L III 81 4 Primary Eye Irritation, rabbit 43840901* Reversible conjunctival irritation III 81 5 Primary Skin Irritation, rabbit 41892008a Slight irritant IV 81 6 Dermal Sensitization, guinea pig 41890002* Not a sensitizer 81 8 Acute Neurotoxicity N/ A * Data presented in table are for formulations containing technical MSMA. a DSMA study used as a surrogate TABLE 4.2.2c: Acute Toxicity of DSMA*

Guideline No. Study Type MRID# s Results Toxicity Category 81 1 Acute Oral, rat 41892004 LD50 = 1935 ( 1631 2295) mg/ kg ( M& F) III 81 2 Acute Dermal, rabbit 41892005 LD50 > 2000 mg/ kg III 81 3 Acute Inhalation, rat 41892006 LC50 > 6 mg/ L IV 81 4 Primary Eye Irritation, rabbit 41892007 Redness and chemosis of the conjunctivae III 81 5 Primary Skin Irritation, rabbit 41892008 No erythema or edema IV 81 6 Dermal Sensitization, guinea pig 41890009 Not a sensitizer 81 8 Acute Neurotoxicity N/ A * Data presented is for technical DSMA. Page 44 of 125 TABLE 4.2.2d: Acute Toxicity of CAMA*

Guideline No. Study Type MRID# s Results Toxicity Category 81 1 Acute Oral, rat 42880201 LD50 > 5000 mg/ kg ( M& F) IV 81 2 Acute Dermal, rat 42900101 LD50 > 5000 mg/ kg IV 81 3 Acute Inhalation, rat 42900102 LC50 > 5 mg/ L IV 81 4 Primary Eye Irritation, rabbit 42900202 Mild eye irritant III 81 5 Primary Skin Irritation, rabbit 42900203 Slight skin irritant IV 81 6 Dermal Sensitization, rabbit 42900103 None 81 8 Acute Neurotoxicity N/ A * Acute oral studies listed in table represent a formulation with 10.3% a. i.

4.2.3 FQPA Hazard Considerations Acceptable developmental studies in rats and rabbits along with a two generation reproductive toxicity study are available for MMA. Results of developmental and reproductive toxicities studies provided no indication of increased susceptibility of rat or rabbit. The toxicology database is considered complete for the evaluation of sensitivity of the developing young. A developmental neurotoxicity study is not required. As described below, toxicity to gastrointestinal tract and kidney provide the critical effects for MMA following oral exposures. These effects are more sensitive than toxicities noted in other studies, including developmental and reproductive toxicity and neurotoxicity. Therefore, the FQPA safety factor is not needed.

4.2.4 Dose Response, Hazard Identification and Toxicity Endpoint Selection Toxicological endpoints are needed to assess potential risk to MMA from the following durations and routes of exposure:

  Acute and chronic dietary exposure,   Short and intermediate term incidental oral exposure,   Short and intermediate term dermal exposure, and   Short and intermediate term inhalation exposure.

Although the mode of action for MMA is not known, toxicity endpoints relevant to the target tissues provide the critical endpoints for each exposure scenario. Following oral exposures, toxicity to the gastrointestinal tract provide the critical effects for MMA. Diarrhea and vomiting, suggesting irritation of the gastrointestinal tract, were noted in the chronic dog study in the first week of dosing within 2 5 hours of each days dosing at the highest dose ( week 1 LOAEL of 40 mg/ kg/ day). In the absence of an acute toxicity study with sub lethal observations, the week 1 Page 45 of 125 NOAEL of 10 mg/ kg for the effects noted in the first week of dosing provide the most appropriate effects for acute dietary risk assessment.

For short term incidental oral exposure, toxicity observed in the does from the rabbit development toxicity study provides an appropriate endpoint. Animals in the rabbit study were dosed on 13 consecutive days, consistent with the duration of interest for short term incidental oral exposure ( i. e. 1 30 days). The maternal toxicity LOAEL is 12 mg/ kg/ day, based on decreased body weight, food consumption ( during the dosing period), and abortions. The maternal toxicity NOAEL is 7 mg/ kg/ day.

In the two year, chronic toxicity study in rat, the LOAEL of 27.2 mg/ kg/ day is based on decreased body weights, diarrhea, body weight gains, food consumption, and histopathology of gastrointestinal tract and thyroid. Diarrhea and body weight changes were noted at the 27.2 mg/ kg/ day dose level following approximately 4 to 7 weeks of exposure and are therefore reasonable for use in intermediate term incidental oral risk assessment. Histopathology was observed only at termination. Thus, the NOAEL of 3.2 mg/ kg/ day is appropriate for extrapolating chronic dietary risk assessment and intermediate term incidental oral exposure. It is notable that the rat NOAEL for chronic toxicity is further supported by the NOAEL observed in the chronic dog study ( 2 mg/ kg/ day, respectively). The effects noted in the chronic study in the rat and dog chronic studies are more sensitive than those noted in the 104 week study with mice ( NOAEL of 9.3 mg/ kg/ day).

Pharmacokinetics of absorption and metabolism can differ among oral, dermal, and inhalation exposures. Because of this, it is preferred to use route specific studies when extrapolating risk. Regarding dermal exposure, the MMA dermal toxicity study in rat indicates no toxicologically relevant effects up to 1000 mg/ kg/ day. Regarding inhalation exposures, the rat inhalation study with DMA has been selected as a surrogate for MMA in the absence of an MMA inhalation toxicity study. This provides some uncertainty in the inhalation risk assessments for MMA. As described in the EPA's issue paper regarding metabolism and mode of action for DMA, the pharmacokinetics of oral exposure to DMA and MMA differ and that chemical specific data are preferred. In the case of oral exposure, the target tissues for DMA and MMA are believed to be different ( bladder vs. gastrointestinal tract). In the 90 day inhalation toxicity study with DMA, port of entry effects, not systemic ones, are the most sensitive. Both DMA and MMA cause in vitro cytotoxicity in various cell lines and tissues. The cytotoxic concentrations are within the same ranges for the pentavalent DMA and MMA ( USEPA 2006). Although the relationship between cytotoxicity and nasal/ respiratory irritation is not known, it's a reasonable assumption that chemicals which cause cytotoxicity to tissue surfaces may also be irritating to the respiratory tract. Moreover, both MMA and DMA are mildly irritating to eyes. For some pesticide chemicals where no inhalation studies are available, OPP often extrapolates risk using oral studies with the assumption of 100% absorption. This approach is reasonable for chemicals whose toxicity is primarily related to systemic effects. However, for MMA, it is a reasonable assumption that MMA may cause port of entry effects via the inhalation route, similar to DMA. As such, use of an oral study may not be appropriate in this case. As a screening approach, the DMA inhalation study is currently being used as a surrogate for MMA inhalation toxicity. In the event that the use pattern or exposure profile for MMA changes, the Agency may require an inhalation toxicity study with MMA or its salts in the future. Page 46 of 125 Historically, EPA has utilized 10X factors to account for inter species and intra species extrapolation/ uncertainty. In the case of MMA, there are not sufficient data to support reduction of the default factors. Therefore, a total of 100X will be applied to each route and duration of MMA exposure to account for inter species and intra species extrapolation/ uncertainty.

<IP_ADDRESS> Acute Reference Dose ( aRfD)  General Population There are no acute oral studies which considered non lethal doses of MMA which could provide endpoints of the appropriate duration of exposure ( i. e. single dose). However, in the chronic oral toxicity study in dog ( MRID# s 40546101 and 41266401), vomiting and diarrhea were observed in the first of dosing primarily after 2 5 hours after each days dosing. The timing of these events suggest an acute effect on the gastrointestinal tract following gavage administration of MMA.

In the chronic oral toxicity study in dog, MMA was administered to 5 purebred beagle dogs/ sex/ group by capsule at dose levels of 0, 2.5, 10, or 40 mg/ kg/ day for the first week and at dose levels of 0, 2, 8, and 35 mg/ kg/ day for the remaining 51 weeks. The LOAEL for the first week of dosing was 40 mg/ kg/ day based on diarrhea and vomiting. The NOAEL for the first week of dosing was 10 mg/ kg/ day.

<IP_ADDRESS> Chronic Reference Dose ( cRfD)

In a combined chronic toxicity/ carcinogenicity feeding study ( MRID# 41669001), MMA was administered in the diet to 60 Fischer F344 rats/ sex/ dose at dose levels of 0, 50, 400 and 800 1300 ppm ( 0, 3.2, 27.2, and 93.1 mg/ kg/ day for males and 0, 3.8, 32.9, and 101.4 mg/ kg/ day for females) for 104 weeks. The high dose group of 60 animals/ sex received 1300 ppm until week 53. Because of excessive mortality ( 32% of males), the highest dose was reduced to 1000 ppm until week 60 and to 800 ppm for the remainder of the study. Beginning at week 4 5, diarrhea was observed in all rats at the highest dose level, and in 27/ 60 males and 45/ 60 females of the 400 ppm group. Body weights were statistically decreased from week 7 through termination for males of the 400 ppm groups and from week 4 through termination for high dose males.

The chronic LOAEL was 400 ppm ( 27.2 mg/ kg/ day for males and 32.9 mg/ kg/ day for females) based on decreased body weights, body weight gains and, food consumption, diarrhea and, histopathology of the gastrointestinal tract and thyroid.

<IP_ADDRESS> Incidental Oral Exposure ( Short Term)

In a developmental toxicity study ( MRID# 15939001), MMA was administered in distilled water by gavage to 14 mated New Zealand white rabbits per group at doses of 0, 1, 3, or 7 mg/ kg/ day on gestation days ( GD) 7 19, inclusive. Subsequent groups of 13 14 mated New Zealand white rabbits were dosed with 0 and 12 mg/ kg/ day test material. The maternal toxicity LOAEL was 12 mg/ kg/ day, based on decreased body weight, food consumption ( during the dosing period), and abortions. The maternal toxicity NOAEL was 7 mg/ kg/ day. Page 47 of 125 <IP_ADDRESS> Incidental Oral Exposure ( Intermediate Term)

In a combined chronic toxicity/ carcinogenicity feeding study ( MRID# 41669001), MMA was administered in the diet to 60 Fischer F344 rats/ sex/ dose at dose levels of 0, 50, 400 and 800 1300 ppm ( 0, 3.2, 27.2, and 93.1 mg/ kg/ day for males and 0, 3.8, 32.9, and 101.4 mg/ kg/ day for females) for 104 weeks. The chronic LOAEL was 400 ppm ( 27.2 mg/ kg/ day for males and 32.9 mg/ kg/ day for females) based on decreased body weights, and diarrhea. The chronic NOAEL was 50 ppm ( 3.2 mg/ kg/ day for males and 3.8 mg/ kg/ day for females).

<IP_ADDRESS> Dermal Exposure ( Short and Intermediate Term)

In a 21 day dermal toxicity study ( MRID# 41872701/ 42659701), MMA ( 99.4% a. i., Batch# 0030401) was administered dermally to 5 New Zealand white rabbits/ sex/ group at doses of 0, 100, 300, or 1000 mg/ kg/ day for 6 hours/ day, 5 days/ week for 21 days. The systemic toxicity LOAEL was > 1000 mg/ kg/ day. The systemic toxicity NOAEL = 1000 mg/ kg/ day.

There was no edema or erythema noted at the exposure sites of any dose group. There were no histological dermatopathology findings at the 1000 mg/ kg/ day dose level as compared to the control group. The dermal irritation LOAEL was > 1000 mg/ kg/ day. The dermal irritation NOAEL = 1000 mg/ kg/ day.

<IP_ADDRESS> Inhalation Exposure ( Short and Intermediate Term)

In a 90 day toxicity study ( MRID# 44700301), DMA [( Cacodylate 3.25) ( active ingredients: cacodylic acid ( 4.9%) and sodium cacodylate ( 28.4%); batch 095/ 93)] was administered by inhalation to 10 rats/ sex/ dose at aerosol concentrations of 10, 34 and 100 mg/ m3 ( analytical concentrations 0.01, 0.034, or 0.1 mg/ L). The NOAEL is 0.010 mg/ L/ day. The LOAEL is 0.034 mg/ L/ day in both male and female rats based on the presence of moderate and marked intracytoplasmic eosinophilic granules ( IEG) in the cells of the nasal turbinates.

4.2.5 Recommendation for Aggregate Exposure Risk Assessments The FQPA ( 1996) requires that EPA aggregate risks from multiple pathways as part of tolerance reassessment. OPP aggregates risk from multiple pathways and routes in cases where the toxic effect of interest is common among or between the routes of interest. In the case of MMA, exposures from the oral route ( food, water, incidental oral) may be aggregated. As no effects were noted in the MMA dermal toxicity study and the DMA inhalation toxicity study is being used a surrogate, it is inappropriate to aggregate risks from dermal and inhalation exposures.

4.2.6 Classification of Carcinogenic Potential MMA, or its sodium or calcium salts, have been classified as " not likely" human carcinogens. Parathyroid adenomas were noted in the combined chronic/ carcinogenicity study in rats for Page 48 of 125 MMA. These tumors were outside of the historical controls. However, the tumors are not a concern because 1) only the benign tumors were increased in incidence; 2) pair wise significance was not attained for either sex; 3) an increase in tumor incidence was not observed in mice; and 4) the acceptable genetic toxicology studies indicate that MMA is not mutagenic in bacteria ( Salmonella typhimurium) or cultured mammalian cells ( Chinese hamster ovary). Similarly, MMA did not induce unscheduled DNA synthesis ( UDS) in primary rat hepatocytes.

Table 4.2.4: Summary of Toxicological Doses and Endpoints for Chemical for Use in Human Risk Assessments of MMA Exposure Scenario Dose Used in Risk Assessment, UF Level of Concern for Risk Assessment Study and Toxicological Effects Acute Dietary ( general population) NOAEL = 10 mg/ kg UF = 100 Acute RfD & PAD = 0.1 mg/ kg Chronic Toxicity in Dog, MMA study ( MRID# 40546101) LOAEL = 40 mg/ kg/ day based on clinical signs of diarrhea and vomiting observed in the first of week of dosing with 2 5 hours of each days dosing.

Chronic Dietary ( all populations) NOAEL= 3.2 mg/ kg/ day UF = 100 Chronic RfD & PAD =

0.03 mg/ kg/ day Chronic Toxicity Rat, MMA study ( MRID# 41669001) Rat LOAEL = 27.2 mg/ kg/ day for males and 32.9 mg/ kg/ day for females based on decreased body weights, diarrhea, body weight gains, food consumption, histopathology of gastrointestinal tract and thyroid.

Incidental Oral Short Term ( 1  30 days) NOAEL= 7 mg/ kg/ day LOC = 100 Rabbit developmental toxicity study ( MRID# 15939001) LOAEL = 12 mg/ kg/ day, based on decreased body weight, food consumption ( during the dosing period), and abortions.

Incidental Oral Intermediate Term ( 1  6 months) NOAEL= 3.2 mg/ kg/ day LOC = 100 Chronic Rat study ( MRID# 41669001)

LOAEL = 27.2 mg/ kg/ day for males and 32.9 mg/ kg/ day for females based on decreased body weights, diarrhea.

Dermal Short Term ( 1  30 days) Intermediate Term ( 1  6 months) Dermal NOAEL= 1000 mg/ kg/ day LOC = 100 21 Day Dermal Toxicity in Rabbit, MMA study ( MRID# 41872701) LOAEL > 1000 mg/ kg/ day.

Dermal Long Term (> 6 months) Not applicable Inhalation Short Term ( 1  30 days) Intermediate Term ( 1  6 months) Inhalation NOAEL= 0.01 mg/ L ( 4.38 mg/ kg/ day, adjusted) LOC = 100 90 Day Inhalation with DMA  Rat ( MRID# 44700301) LOAEL = 0.034 mg/ kg/ L ( 14.95 mg/ kg/ day) based on presence of moderate and marked intracytoplasmic eosinophilic granules ( IEG) in the nasal turbinate cells of male and female rats.

Cancer Classification: " not likely human carcinogen"

UF = uncertainty factor, FQPA SF = Special FQPA safety factor, NOAEL = no observed adverse effect level, LOAEL = lowest observed adverse effect level, PAD = population adjusted dose ( a = acute, c = chronic) RfD = reference dose, MOE = margin of exposure, LOC = level of concern, NA = Not Applicable Page 49 of 125 4.2.7 Endocrine Disruption EPA is required under the FFDCA, as amended by FQPA, to develop a screening program to determine whether certain substances ( including all pesticide active and other ingredients) " may have an effect in humans that is similar to an effect produced by a naturally occurring estrogen, or other such endocrine effects as the Administrator may designate." Following recommendations of its Endocrine Disruptor and Testing Advisory Committee ( EDSTAC), EPA determined that there was a scientific basis for including, as part of the program, the androgen and thyroid hormone systems, in addition to the estrogen hormone system. EPA also adopted EDSTAC's recommendation that the Program include evaluations of potential effects in wildlife. For pesticide chemicals, EPA will use FIFRA and, to the extent that effects in wildlife may help determine whether a substance may have an effect in humans, FFDCA authority to require the wildlife evaluations. As the science develops and resources allow, screening of additional hormone systems may be added to the Endocrine Disruptor Screening Program ( EDSP). In the available toxicity studies on MMA, there was no estrogen, androgen, and/ or thyroid mediated toxicity.

4.3 DMA 4.3.1 Database Summary The database of toxicology studies for DMA is adequate for risk assessment purposes. No additional studies are required at this time. Acceptable animal toxicity studies include: subchronic oral, dermal, and inhalation toxicity; chronic toxicity following oral exposure in rodents and non rodents; developmental toxicity in rat and rabbit; reproductive toxicity; and genotoxicity/ mutagenicity. Similar to MMA, there is extensive data evaluating the pharmacokinetics and metabolism of DMA in various species in addition to extensive in vitro metabolism and toxicity studies. Moreover, there is a robust database of studies evaluating the mode of action for the development of bladder tumors in rats ( See USEPA 2006). There are no studies which observe toxic effects of DMA in humans and there are no epidemiology studies with DMA. There are two metabolism studies where human subjects ingested DMA and urinary metabolites were measured ( Buchet et al, 1981; Marafante et al, 1987).

4.3.2 Toxicological Effects In oral toxicity studies with DMA, the bladder and thyroid have been identified as potential target organs. As described below, effects on the bladder provide the most appropriate and toxicologically relevant effects for extrapolating cancer and oral, non cancer risk to DMA. In standard rodent bioassays, DMA is associated with bladder tumors in female and male Fischer ( F344) rats. DMA is not associated with neoplastic responses in either sex of B6C3F1 mice or two hybrid strains of mice ( 41862101; Wei et al., 1999; NCI, 1969). Although negative findings are found in the standard mouse bioassay, positive findings have been reported in genetically engineered mouse strains or strains susceptible for specific tumor types ( Chen et al., 2000; Salim et al., 2003; Hayashi et al., 1998). Such strains can be useful for hazard identification and may provide insight into the chemical and gene interactions involved in carcinogenesis. It is Page 50 of 125 inappropriate, however, to use these strains for cancer risk extrapolation purposes because they are engineered to be highly susceptible to carcinogens.

A postulated mode of action is a biologically plausible hypothesis for the sequence of events leading to an observed effect ( in this case, rat bladder tumors). A mode of action identifies " key" cellular and biochemical events  i. e., those that are both measurable ( quantifiable) and critical to the observed adverse response. In the special metabolism and mode of action paper on DMA ( USEPA 2006), the overall weight of the evidence supporting the postulated mode of action for DMA is described in detail. The Agency's conclusions regarding the mode of action and dose response assessment were supported by the SAB at the September, 2005 meeting.

The proposed mode of action for the development of bladder tumors from oral exposure to DMA is as follows: 1) reductive metabolism of DMAV to DMAIII; 2) DMAIII causes urothelial cytotoxicity; 3) regenerative cell proliferation then ensues in order to replace dead urothelial cells; 4) with continuous exposure, persistent regenerative proliferation leads to the production of additional mutations, including those necessary for multi step carcinogenesis. As summarized in Table 4.3.2a experimental data are available to support the coincidence of key events at similar concentration levels. Similarly, time course data are available that support the sequence of key events in time. The levels of DMAIII in the urine of rats treated with 100 ppm DMAV range from 0.5   5.0 FM. The LC50 values for DMAIII in rat and human urinary epithelial cells in vitro are 0.5 0.8 FM. There is a significant increase in chromosome aberrations in human lymphocytes in vitro at about 1.35 FM DMAIII. At 100 ppm, there is significant cell killing and regenerative proliferation in female rat bladders. It appears that chromosomal mutations, cytotoxicity and cell proliferation can potentially occur concurrently at 100 ppm DMAV, the tumorigenic dose in female rats via the feed.

The dose response relationship for DMA tumorigenesis based on mode of action considerations is nonlinear as it is dependent on genetic, biochemical and histopathological events for which dose response relationships are nonlinear. Page 51 of 125 Table 4.3.2a: Summary of Key Precursor Events and Urinary Bladder Tumor Formation in Female F344 Rats Administered DMAV in the Feed ( Reproduced from USEPA 2006)

Dose ppm ( mg/ kg bw/ day) Metabolism of DMAV to DMAIII * Urothelial toxicity** Regenerative proliferation response*** Urothelial hyperplasia**** Transitional cell carcinoma 2 ( 0.2) + ( week 3 0.03 ± 0.07uM) + ( week 10 6/ 10, grade 3 or 4)

10 ( 1) + ( week 3 0.12 ± 0.05uM) + ( week 3 2/ 7, grade 3)

( week 10 8/ 10, grade 3 or 4) +/ ( week 10 nonstatistical 1.5 fold increase)

40 ( 4) + ( week 3 0.28 ± 0.24uM) + ( week 3 7/ 7, grade 3)

( week 10 5/ 10, grade 3 or 4) + ( week 10 4.3 fold increase) + ( week 10 4/ 10)

100 ( 9.4) + ( week 3 0.55 ± 0.4 uM) + ( 6 hrs 6/ 7, grade 3)

( 24 hrs 4/ 7, grade 3 or 4)

( week 2 6/ 10, grade 5)

( week 10 10/ 10, grade 4 or 5) + ( week 1 2.2 fold increase)

( week 2 3.9 fold)

( week 10 4.2 fold increase) + ( week 2 1/ 10)

( week 8 7/ 10)

( week 10 9/ 10) + ( Gur et al., 1989a; serial sacrifices not performed but carcinoma first observed at week 87)

* concentration of DMAIII in fresh voided urine collected from female rats fed DMAV in the diet ( Arnold et al., 2004; Cohen et al., 2002a) ** incidence of urothelial toxicity ( number of animals affected over total number of animals examined) and SEM classification ( Arnold et al., 1999; Cohen et al., 2001; Cohen et al., 2002a) *** BrdU labeling index, fold increase compared to control value ( Arnold et al., 1999; Cohen et al., 2001) **** Simple hyperplasia, number of animals affected over total number of animals examined ( Arnold et al., 1999; Cohen et al., 2002a) + present  absent mg/ kg bw per day estimated by averaging across studies and time points. Page 52 of 125 Thyroid lesions, primarily incidence of cuboidal to columnar epithelial cells lining thyroid follicles were seen in studies with the rat ( carcinogenicity, subchronic, and two generation reproduction study). There is some evidence that DMA induces tumors in the thyroid gland of rats but at doses much greater than those required to produce urinary bladder tumors. There is also some evidence that DMA has been used as a tumor promoter after initiation of the thyroid gland with mutagenic chemicals ( Yamamoto et al, 1995; Yamamoto et al, 1997). The toxicological endpoints selected based on the bladder tumor mode of action studies for DMA are health protective for other potential toxicities, including thyroid effects.

The subchronic inhalation toxicity study with DMA indicates that port of entry effects of the nose are the most sensitive for inhalation exposure. Regarding dermal toxicity, no dermal or systemic toxicity was noted up to 300 mg/ kg/ day. At 1000 mg/ kg/ day, the limit dose, body weight changes in females and testicular effects were noted in males. The effects noted in the testes were only observed at the limit dose and were not replicated in other DMA studies.

Table 4.3.2b: Acute Toxicity of Cacodylate 3.25 ( 33.3% a. i.)