UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D. C. 20460 OFFICE OF PREVENTION, PESTICIDES, AND TOXIC SUBSTANCES DP Barcode: D276945 PCCode: 056801 Date: August 17, 2002 MEMORANDUM:

SUBJECT: Revised EFED Risk Assessment of Carbaryl in Support of the Reregistration Eligibility Decision (RED)

To: Anthony Britten, PM Team Reviewer Betty Shackleford, Product Manager 53 Special Review and Reregistration Division (7508C)

FROM: E. Laurence Libelo, Ph. D., Environmental Engineer Thomas Steeger, Ph. D., Senior Biologist Environmental Risk Branch IV Environmental Fate and Effects Division (7507C)

THRU: Betsy Behl, Chief Environmental Risk Branch IV/ Environmental Fate and Effects Division (7507C)

The Environmental Fate and Effects Division has revised the Environmental Fate and Ecological Risk Assessment chapter in support of the reregistration eligibility decision on carbaryl. The chapter has been abridged from its April 8, 2002, version at the request of the Special Review and Reregistration Division and no longer includes environmental fate data evaluation records contained in the original chapter. Although the data evaluation records were cleared for confidential business information, their presence in the chapter did not contribute significantly to understanding the environmental fate of carbaryl. If interested, the public can access both environmental fate and ecological effect data evaluation records by petitioning the Agency through the Freedom of Information Act.

The revised chapter reflects comments made by the registrant (Aventis) during the 30 day error correction phase of the review process and contains more detailed information on the input files for the Pesticide Root Zone Model (PRZM) used in estimating runoff concentrations of carbaryl. Although the registrant provided constructive comments in their 30 day responses to the draft risk assessment of carbaryl, the overall concerns and uncertainties originally identified regarding the environmental fate and ecological effects of carbaryl have not changed. Also included with the revised chapter is a review (DP Barcode D279109) of data submitted regarding the Section 24C Special Local Needs use of carbaryl on oyster beds in Willapa Bay and Grays Harbor, Washington, for control of burrowing shrimp.

Both the revised environmental fate and ecological effects chapter and the review of the use of carbaryl to control burrowing shrimp are intended to represent EFED's assessment of the risks associated with the uses of carbaryl. While some uses and application rates discussed in the chapter may no longer be supported, the EFED chapter is intended to provide a general overview of the concerns and uncertainties associated with the past and present uses of carbaryl. Environmental Fate and Ecological Risk Assessment For the Reregistration of Carbaryl 1 Naphthyl methylcarbamate 1 naphthyl N methylcarbamine CAS Registry Number 63 25 2 PC Code 056801 Prepared by:

E. Laurence Libelo, Ph. D., Environmental Engineer Angel Chiri, Ph. D., Entomologist Thomas M. Steeger, Ph. D., Fishery Biologist United States Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division Environmental Risk Branch IV Ariel Rios Building 1200 Pennsylvania Ave., N. W. Mail Code 7507C Washington, DC 20460 Reviewed by:

Elizabeth Behl, Branch Chief Dana Spatz, Senior Chemist i TABLE OF CONTENTS 1.0 Summary and Environmental Risk Conclusions ............................. 1 Risk to Terrestrial Organisms .............................................. 1 Risk to Plants ........................................................... 3 Risk to Endangered Species................................................ 3 Fate and Water Assessment ................................................ 4 2.0 Introduction ........................................................... 7 3.0 Integrated Risk Characterization .......................................... 8 Introduction ............................................................ 8 Aquatic Organisms ....................................................... 9 Terrestrial Organisms ................................................... 12 Endangered Species ..................................................... 15 Endocrine Disruption Concerns ............................................ 15 Uncertainties .......................................................... 16 4.0 Environmental Fate Assessment .......................................... 17 Exposure Characterization ................................................ 17 Persistence ...................................................... 21 Chemical Degradation Processes............................... 21 Hydrolysis .......................................... 21 Photolysis................................................. 21 Microbially mediated Processes ............................... 21 Mobility ........................................................ 22 Batch Adsorption/ Desorption ................................. 22 Column Leaching ........................................... 23 Field Dissipation ................................................. 23 Terrestrial Field Dissipation .................................. 23 Forestry Field Dissipation .................................... 24 Aquatic Field Dissipation .................................... 24 Bioaccumulation in Fish ........................................... 24 Foliar Dissipation................................................. 25 Atmospheric Transport ............................................ 25 1 Naphthol Fate and Transport ...................................... 26 Aquatic Exposure Assessment ............................................. 27 Urban and Suburban .................................................... 29 Estimated Environmental Concentrations for Terrestrial Ecological Risk Assessment................................................ 29 5.0 Drinking Water Assessment ............................................. 30 Water Resources Assessment ............................................. 30 ii Drinking Water Exposure Assessment ................................ 31 Drinking Water Modeling .................................... 31 Water Treatment Effects ......................................................... 32 Groundwater Resources ............................................ 33 Surface Water Resources ........................................... 34 Monitoring Data............................................ 34 NAWQA ........................................... 34 Registrant Monitoring Study ............................ 35 Sacramento San Joaquin River Delta ..................... 37 STORET ........................................... 37 6.0 Hazard and Risk Assessment for Aquatic Organisms ........................ 37 Hazard Assessment for Aquatic Organisms .................................. 37 Freshwater Fish .................................................. 37 Amphibians ..................................................... 38 Freshwater Invertebrates ........................................... 38 Estuarine/ Marine Fish ............................................. 39 Estuarine/ Marine Invertebrates ...................................... 39 Aquatic Plants ................................................... 40 1 Naphthol ...................................................... 40 Risk Assessment for Aquatic Organisms..................................... 40 Freshwater Fish .................................................. 40 Freshwater Aquatic Invertebrates .................................... 41 Estuarine/ Marine Fish ............................................. 41 Estuarine/ Marine Invertebrates ...................................... 44 Reproduction Effects on Fish ....................................... 44 Endangered Aquatic Species ............................................. 45 7.0 Hazard and Risk Assessment for Terrestrial Organisms ..................... 45 Hazard Assessment for Terrestrial Organisms ................................ 45 Avian .......................................................... 45 Mammalian ..................................................... 46 Insects ......................................................... 46 Terrestrial Plants ................................................. 46 Risk Assessment for Terrestrial Organisms................................... 47 Avian Risk ...................................................... 47 Nongranular Formulations .................................... 47 Granular Formulations....................................... 48 Mammalian Risk ................................................. 48 Risk to Herbivores/ Insectivores: Nongranular Formulations ......... 48 Risk Quotients for Herbivores/ Insectivores Based on Less than Maximum Label Use Rates ....................... 48 iii Risk Quotients for Herbivores/ Insectivores Based on Maximum Label Use Rates ............................... 48 Risk to Granivores: Nongranular Uses .......................... 49 Chronic Risk: Nongranular Uses ......................... 50 Risk: Granular Uses................................... 50 Reproduction Effects ............................................. 50 Insects ......................................................... 51 Terrestrial Plants ................................................. 52 Endangered Terrestrial Species ...................................... 52 8.0 Summary of Ecological Incident Data .................................... 53 9.0 References (Non MRID) ................................................ 55 Appendix A: Refined Water Memo ............................................. 62 Appendix B: Ecological Risk Assessment ....................................... 147 Appendix C: Toxicity Assessment ............................................. 172 Appendix D: ELL FATE ..................................................... 183 Appendix E: Examples of PRZM Standard Pond Input Files ....................... 185 1 1.0 Summary and Environmental Risk Conclusions Carbaryl is a carbamate insecticide registered for control of a wide range of insect and other arthropod pests on over 100 crop and noncrop use sites, including home and garden uses. Carbaryl is a cholinesterase inhibitor that acts on animals on contact and upon ingestion by competing for binding sites on the enzyme acetyl cholinesterase, thus preventing the breakdown of acetyl choline.

Risk to Terrestrial Organisms ° Three different kinds of usage data were considered to assess risk to terrestrial organisms: maximum label rates for 74 uses, maximum reported (based on survey usage data available from the Doane's Agricultural Services for 42 uses) rates, and Quantitative Usage Analysis "average" rates data provided by OPP's Biological and Economic Analysis Division for 70 uses. In most cases the Level of Concern (LOC) exceedance pattern was not significantly affected by the kind of application rate data used to calculate risk quotients.

° Although no avian acute risk LOCs are exceeded for any nongranular carbaryl uses at maximum or less than maximum label application rates, the avian chronic risk LOC is exceeded for most uses. The avian acute LOC is exceeded for 20 g birds for all granular carbaryl uses (risk quotients [RQs]: 0.52  4.76) and for 180 g birds, it is exceeded for the trees/ ornamentals, turfgrass, and tick control uses (RQ: 0.53). No acute LOCs are exceeded for birds in the 1000 g weight class for any of the granular carbaryl uses.

° At maximum label rates, the mammalian acute risk LOC (0.5) is exceeded for all 74 nongranular uses (0.76  12.12). The proportion of RQs exceeding the acute LOCs decreases significantly for mammals in all three weight classes feeding on fruits, pods, seeds, and large insects, as well as for the 1000 g mammals feeding on broadleaf/ forage plants and small insects. At maximum reported application rates the acute risk LOC for 15 g mammals feeding on short grass is exceeded for 41 of 42 nongranular carbaryl uses (RQs: 0.60 11.36 and at "average" use rates is exceeded for 63 of 70 uses.

° The mammalian chronic risk LOC (1) is exceeded for practically all nongranular carbaryl uses at maximum label (RQs: 3.0  48.0), maximum reported (RQs: 1.5  45.0), and "average" use rates (RQs: 1.5  15.9). Therefore, almost all nongranular carbaryl uses are expected to pose acute and chronic risks to small mammals.

° At maximum label rates, acute risk LOCs are exceeded for 15 g mammals (RQs: 2.3  21.1) and 35 g mammals (RQs: 0.99  9.04) for all granular uses, indicating that all granular carbaryl uses pose an acute risk to the smaller mammalian species. For 1000 g mammals, the acute risk LOC is not exceeded for any use.

° Being highly toxic to honey bees and arthropods in general, carbaryl poses a risk to beneficial insects, including many pests's natural enemies, when directly exposed to carbaryl applications, residues on foliage, or contaminated pollen or nectar. Carbaryl is one of the 2 pesticides more often implicated in bee mortality incidents, ranking second and third, respectively, in two separate bee kill surveys undertaken in 1997 by the Washington State Department of Agriculture and the American Beekeeping Federation.

Risk to Aquatic Organisms ° Three different application scenarios were considered in assessing risk to aquatic organisms: maximum label rates, maximum reported (based on survey usage data available for 42 uses) rates, and "average" rates. In most cases the Level of Concern (LOC) exceedance pattern was unaffected by the kind of usage data used to calculate risk quotients.

° The acute risk LOC (0.5) for freshwater fish is exceeded for one of five use scenarios modeled (citrus), at maximum label (RQ: 1.10), maximum reported (RQ: 0.93), and "average" (RQ: 0.58) use rates, while the chronic risk LOC for freshwater fish is not exceeded for any scenario, at any use rate.

° The acute risk LOC for estuarine/ marine fish is not exceeded for any use scenario modeled, at any use rate. Because of lack of valid chronic toxicity data, it is not possible to fully assess chronic risk to estuarine/ marine fish at this time.

° Available nonguideline studies suggest that exposure to carbaryl may act as a potential endocrine disruptor in fish. Exposure to sublethal carbaryl levels cause a significant reduction of serum and pituitary levels of gonadotropic hormone and gonadotropin releasing hormone in the freshwater murrell and a significant decline in ovarian estrogen levels in freshwater perch, starting on day 15 of exposure.

° Most carbaryl uses are likely to pose an acute risk to both freshwater and estuarine/ marine aquatic invertebrates, especially arthropods. The acute risk LOC (0.5) for freshwater invertebrates is exceeded for all five use scenarios modeled at maximum label (RQs: 5.1 161.2 maximum reported (RQs: 3.3  136.5), and "average" (RQs: 2.6  85.3) use rates. The chronic risk LOC (1) is also exceeded for freshwater invertebrates for all 5 use scenarios modeled, at maximum label (RQs: 3.3  91.3), maximum reported (RQs: 2.0  74.7), and "average" (RQs: 1.7  44.7) use rates.

° The acute risk LOC is exceeded for estuarine/ marine invertebrates for the 5 use scenarios modeled at maximum label (RQs: 1.5  48.1), maximum reported (RQs: 1.0  40.7), and "average" (RQs: 0.8  25.4) use rates. Lack of reliable toxicity data precluded the assessment of chronic risk for estuarine/ marine invertebrates.

° Carbaryl directly applied to oyster beds in Washington State poses a severe, albeit localized and temporary, acute risk to fish and nontarget arthropods in and around the target area. The oyster industry is encouraged to continue searching for alternative pest shrimp management measures and more selective carbaryl application regimes, within an IPM context, to minimize impact on non target organisms. 3 Risk to Plants ° Carbaryl can be used as a fruit thinning agent on apples and pears, and according to the label it may cause injury to tender foliage if applied to wet foliage or during periods of high humidity. It may also cause injury to Boston ivy, Virginia creeper, or maidenhair fern. A few incidents involving injury to vegetable crops (potatoes, tomatoes, cabbage, and broccoli) have been reported. To fully assess carbaryl risk to terrestrial plants, Tier I and, if appropriate, Tier II Seed Germination and Seedling Emergence, as well as Vegetative Vigor studies should be submitted by the registrant.

° Based on the single core green alga study available, the acute risk LOC for aquatic plants is not exceeded for any of the five scenarios modeled even at maximum label rates. However, because four of the required five toxicity studies with aquatic plants are unavailable, these results are insufficient to fully assess carbaryl risk to aquatic plants. Toxicity testing for aquatic plants is required to support carbaryl's registered forestry uses.

Risk to Endangered Species ° The endangered species LOC for birds is met or exceeded for most nongranular carbaryl uses at maximum label, QUA average, and maximum reported use rates. The endangered species LOC is exceeded for 20 g birds for all granular uses; it is exceeded for 180 g birds it is exceeded for all granular uses, except cucumber, melons, pumpkin, squash, beans, peas, lentils, cowpeas, southern peas, wheat, millet, and sugar beets; and for 1000 g birds, it is reached for the trees and ornamentals, turfgrass, and tick control granular uses.

° The endangered species LOC for mammals is met or exceeded for all uses at maximum label, QUA average, and maximum reported use rates.

° At less than maximum label rates the endangered species LOC is exceeded for all carbaryl uses for freshwater and marine/ estuarine aquatic invertebrates. At less than maximum label rates, the endangered species LOC is exceeded for freshwater fish only for the citrus use scenario and not exceeded for estuarine/ marine fish for any of the five use scenarios modeled. 4 Fate and Water Assessment ° Carbaryl is widely detected in surface water at concentrations up to about 7 : g/ L. In general observed concentrations are generally less then 0.5 : g/ L. It was the second most widely detected insecticide, after diazinon, in the U. S. Geological Survey's National Water Quality Assessment (NAWQA) program. NAWQA reported that about 20 % of surface water samples had detectable carbaryl concentrations. For samples where carbaryl was detected the mean concentration was 0.11 : g/ L and the maximum was 5.5 : g/ L. Urban streams had higher frequency of detection then those draining agricultural areas, and had higher concentrations. A targeted study by the registrant found detectable levels of carbaryl in 9 of 15 sites in agricultural areas and 100% of 4 sites in suburban areas (limit of detection = 0.002 : g/ L). Raw water samples from suburban sites had measured residues greater then the limit of detection but below the level of quantitation (0.03 : g/ L) ranging from 0.002 to 0.023 : g/ L. Concentrations in samples from agricultural sites were lower, with one sample measuring about 0.16 : g/ L, one at 0.031 : g/ L and the rest were below the level of quantitation. While this study was targeted at carbaryl use areas only 20 sites were sampled. It is not known how the selected sites relate to the overall distribution of possible exposures. The concentrations found in this study are similar to those reported n non targeted studies. They are not the maximum that occur as evidenced by higher values found in non targeted studies.

° Because of the relatively limited persistence of the compound in the environment it is unlikely that non targeted monitoring studies will detect the maximum concentrations that occur. Extensive data from targeted studies designed specifically to measure carbaryl in relation to actual application and environmental occurrence is not available. Only the registrant study has tried to target use areas. This study, while useful, is limited in extent and did not measure the concentrations as high as observed in other, non targeted studies. Because of the limited number of sites sampled and lack of information on how sampled sites relate to the overall carbaryl use area this study can not be used to estimate the distribution of expected environmental concentrations which actually occur. Targeted monitoring data is limited to this study which found concentrations below those observed in other studies. This lack of extensive targeted data and the limitations inherent in using non targeted data to extrapolate to actual environmental concentrations indicate that computer modeling may provided a more representative estimate of actual peak concentrations that occur.

° Computer modeling using the EPA PRZM3.12 and EXAMS 2.97.5 programs were used to estimate the maximum and average concentrations of carbaryl in surface water. Estimated environmental concentrations (EECs) for use in human health risk assessment were developed by modeling with Index Reservoir scenarios corrected for Percent Cropped Area (PCA) for representative crops. Three different application rate scenarios were used in modeling: the maximum allowed on the label for the specific crop, an "average" rate, and 1 Maximum is the highest application rate allowed according to the label for the specific crop.

"Average" is the average rate as determined by OPP/ BEAD and reported in the a memo titled Quantitative Usage Analysis for Carbaryl, prepared July 21, 1998 by Frank Hernandez, OPP/ BEAD. These average rates are presented here, but are not relevant for drinking water exposure estimates as the usage is averaged over a geographic area. The values do not represent a typical rate that a user in a specific area applies.

Maximum used is the highest rate of application that is actually reported to be used based on OPP/ BEAD analysis of DoaneS survey data.

5 the maximum rate reported to actually be used 1 . EECs varied greatly depending on the geographic location, crop and application rate. EEC values ranged from about 10 : g/ L from sugar beets to about 500 : g/ L from citrus. Chronic EECs ranged from about 1 to 28 : g/ L. With the exception of Florida citrus the calculated EECs are 3 5 times as high as concentrations observed in monitoring data. It is highly unlikely that any but the most extensive targeted monitoring would capture the actual peak concentrations, and the results of the modeling provide an conservative, though not unreasonable, estimate of possible concentrations in drinking water.

° The maximum calculated EEC resulted from use on citrus in Florida. A more detailed assessment of the source of water used to provide drinking water and the relationship between the areas where carbaryl is used and surface water supply sources is required to more accurately evaluate possible human exposures. In 1995, seven percent of Florida's population (about one million people) relied on surface water for their drinking water needs (Marella, 1999). A subset of these people get their water from citrus areas. Until more accurate data on land use and related pesticide application is available and can be linked with data on the location and hydraulic characteristics of the water bodies used for water supply it is not possible to provide a more accurate assessment of possible exposures. Also, the Percent Crop Area for citrus may be much lower then the default minor use crop value of 87% so the corresponding concentration may be lower.

° Carbaryl and its degradate 1 naphthol are fairly mobile and slightly persistent. In general they are not likely to persist or accumulate in the environment. Under acidic conditions with limited microbial activity they may persist.

° Carbaryl dissipates in the environment by abiotic and microbially mediated degradation. The major degradation products are CO2 and 1 naphthol, which is further degrade to CO2. Carbaryl is stable to hydrolysis in acidic conditions, but hydrolyzes in neutral (half life = 12 days) and alkaline environments (pH 9 half life = 3.2 hours). Carbaryl is degraded by abiotic photolysis in water with a half life of 21 days. Under aerobic conditions the compound degrades rapidly by microbial metabolism, with half lives of 4 to 5 days in soil and aquatic environments. In anaerobic environments metabolism is much slower with halflives on the order of 2 to3 months. Carbaryl is considered to be moderately mobile in the environment (Kf =1.7 to 3.5).

° The major metabolite of carbaryl degradation by abiotic and microbially mediated processes is 1 naphthol. This degradate represented up to 67% of the applied carbaryl in degradation 6 studies. It is also formed in the environment by degradation of naphthalene and other polyaeromatic hydrocarbon compounds. Only limited information is available for the environmental transport and fate 1 naphthol. While guideline studies were not submitted specifically for the degradate, open literature information suggests that it is less persistent and less mobile than parent carbaryl.

° Monitoring data for carbaryl in groundwater suggest that carbaryl is not a major groundwater contaminant though targeted data is not available. Parent carbaryl is detected in about 1 % of well samples in non targeted monitoring studies, generally at low concentrations (< 0.1 : g/ L). In the U. S. G. S NAWQA program detections in groundwater were mainly from three setting: wheat (5.8 % of well samples from wheat land use ), orchards and vineyards (1.7 % of well samples from orchard and vineyard land use), and urban (1.8% of urban groundwater samples). 2 Quantitative Usage Analysis for Carbaryl, OPP/ BEAD, 1998 7 2.0 Introduction Carbaryl (1 naphthyl N methylcarbamate) is a broad spectrum carbamate insecticide and acaricide registered for control of over 300 species of insects and mites on over 100 crop and noncrop use sites, including homeowner uses; pet, and poultry uses; and treatment of oyster beds. As other carbamates, carbaryl is a cholinesterase inhibitor that acts on animals on contact and upon ingestion by inactivating the enzyme acetylcholinesterase and blocking the degradation of the neurotransmitter acetylcholine. As a result, the build up of acetylcholine causes an over stimulation of the central nervous system.

Introduced in 1956, carbaryl was the first carbamate insecticide to be successfully marketed for a wide range of agricultural and household lawn and garden uses. Approximately 2.5 million pounds of carbaryl are applied annually in the U. S. A map showing the widespread use of carbaryl in agriculture is shown in Figure 1.

Technical carbaryl is a white crystalline solid that has no appreciable odor. Carbaryl end use formulations include aqueous dispersions, baits dusts, emulsifiable concentrates, flowables, granules, oil based flowables, powder, soluble concentrates, suspension concentrates, wettable powders, water based flowables, water dispersible granules, and ready to use formulations. Carbaryl can be applied by aircraft, ground equipment, and sprinkler irrigation. The principal registrant is Aventis.

For the years of 1987 96, carbaryl usage averaged approximately 2.5 million pounds a. i. for over 1.5 million acres treated. Average estimates for major crops treated include alfalfa (120,000 acres), apples (131,000 acres), corn (82,000 acres), hay (91,000 acres), pecans (95,000 acres), soybeans (101,000 acres), and wheat (106,000 acres). Crops with a high percentage of the total planted acreage treated include Chinese cabbages (57%), asparagus (43%), cranberries (39%), Brussels sprouts (33%), okra (32%), pumpkins (31%), and sweet cherries (25%) 2 . Carbaryl is also used for residential and other non agricultural uses, being the seventh most commonly used insecticide around the home. 8 Figure 1: Carbaryl use in Agriculture (Source USGS http:// water. wr. usgs. gov/ pnsp/ use92/ mapex. html) 3.0 Integrated Risk Characterization Introduction Carbaryl is a widely used insecticide, and as a result of normal agricultural and nonagricultural uses, it is commonly detected in the environment. Carbaryl and its primary degradate 1 naphthol are fairly mobile and slightly persistent. In general they are not likely to persist or accumulate in the environment. Under acidic conditions with limited microbial activity they may persist. Carbaryl dissipates in the environment by abiotic and microbially mediated degradation. The major degradation products are CO2 and 1 naphthol which is further degraded to CO2. Carbaryl is stable to hydrolysis in acidic conditions but hydrolyzes in neutral (pH 7 half life 12 days) and alkaline (pH 9 half life = 5 hours environments. Carbaryl is degraded by photolysis in water with a half life of 21 days. Under aerobic conditions the compound degrades rapidly by microbial metabolism with half lives of 4 to 5 days in soil and aquatic environments. In anaerobic 9 environments metabolism is much slower with half lives on the order of 2 to3 months. Carbaryl is mobile in the environment (Kf =1.7 to 3.5).

The major metabolite of carbaryl degradation by abiotic and microbially mediated processes is 1 naphthol. Only limited information is available for the environmental transport and fate 1 naphthol. While guideline studies were not submitted specifically for the degradate open literature information suggests that it is less persistent and less mobile then parent carbaryl.

Carbaryl is commonly detected in surface water monitoring studies. Concentrations are generally low (less than 1 : g/ L), and the maximum reported value is less than 10 : g/ L. In groundwater carbaryl is detected less often and at lower levels (generally less than 0.01 : g/ L). Because of the relatively limited persistence of the compound in the environment it is unlikely that non targeted monitoring studies will detect the maximum concentrations that occur. Because only very limited targeted data of uncertain quality exists modeling was used to estimate maximum and average concentrations that may occur. Model results suggest that concentrations in surface water resulting from normal agricultural practices are high enough to adversely effect a variety of aquatic, estuarine and marine species.

Aquatic Organisms Most carbaryl uses are not likely to pose acute or chronic risks to freshwater fish, nor an acute risk to estuarine/ marine fish. Most carbaryl uses, however, are likely to pose acute and chronic risks to freshwater invertebrates, and acute risk to estuarine/ marine invertebrates. On an acute basis, carbaryl is highly to slightly toxic to freshwater fish (LC50 = 0.25  20 ppm), moderately toxic to estuarine/ marine fish (LC50 = 2.6 ppm), very highly toxic to freshwater aquatic invertebrates (LC50 = 1.7  26 ppb), and very highly toxic to estuarine/ marine aquatic invertebrates, especially mysids.

Carbaryl's main degradate, 1 naphthol, is highly to moderately toxic to freshwater fish (LC50 = 0.75  1.6 ppm), moderately toxic to estuarine/ marine fish (LC50 = 1.2  1.8 ppm), highly toxic to freshwater invertebrates (LC50 = 0.7 ppm), and highly toxic to moderately toxic to estuarine/ marine invertebrates (0.21  2.5 ppm). EECs for 1 naphthol can not be calculated because of a lack of fate and transport data.

Exposure to sublethal carbaryl levels in laboratory studies are known to adversely affect survival of freshwater fish young (NOAEC = 0.25 ppm) and reproduction in freshwater invertebrates (NOAEC = 3.3 ppb). NOAEC values for estuarine/ marine fish and invertebrates have not been established because of missing data on chronic toxicity to estuarine/ marine fish.

Although EEC scenarios for aquatic organisms were modeled using three different kinds of application rate data (maximum label, maximum reported Doane, and "average" rates), the LOC exceedances are minimally affected by the type of usage data. The acute risk LOC for freshwater fish is exceeded for one of five use scenarios modeled (citrus) at all three application rates, and the chronic risk LOC is not exceeded for any scenario, at any use rate (Table 1). 10 Exposure to certain sublethal carbaryl concentrations can produce deleterious effects in freshwater fish. When the freshwater murrell (Channa punctatus) is exposed to concentrations in the 1666  3730 ppb range, the resulting inhibition of acetycholinesterase (AChE) can cause thyroid and gonadal dysfunction (Ghosh et al., 1990). However, this study was performed at concentration levels well above the highest peak concentration modeled for carbaryl (Table 5) and, therefore, does not provide an indication as to potential effects under field conditions. In the fathead minnow (Primephales promelas), exposure to concentrations in the 0.008  0.68 mg/ l (8  680 ppb) prevented reproduction and decreased survival only at the highest test concentration (Carlson 1972). The NOAEC determined by this study, 0.21 mg/ l (210 ppb), is at the high end of the peak EECs predicted from models for only the citrus scenario (Table 5) and well below the peak EECs predicted for the other four scenarios that were modeled Table 1. Aquatic organisms: acute and chronic Risk LOC exceedances and RQs for nongranular carbaryl uses Acute Risk Chronic Risk Label Max Max Rep "Average" Label Max Max Rep "Average"

Freshwater Fish LOC Exceed. 1 1/ 5 1/ 5 1/ 5 0/ 5 0/ 5 0/ 5 RQs 1. 1 0. 93 0. 58

Estuarine/ Marine Fish LOC Exceed. 1 0/ 5 0/ 5 0/ 5 no data no data no data RQs

Freshwater Inverts LOC Exceed. 1 5/ 5 5/ 5 5/ 5 5/ 5 5/ 5 5/ 5 RQ Ranges 1. 5 48.9 1. 1 4 0.8 25.9 3. 3 91.3 2. 0 74.7 1. 7 44.7 Estuarine/ marine Inverts LOC Exceed. 1 5/ 5 5/ 5 5/ 5 no data no data no data RQ Ranges 1. 5 48.1 1. 0 40.7 0. 8 25.4 1 No. use scenarios for which RQ is greater than LOC/ total No. use scenarios examined (acute LOC = 0.5, chronic LOC = 1)

At relatively high concentrations, carbaryl can adversely affect amphibians' development and behavior. For instance, Bridges (2000) reports that acute exposure to carbaryl in southern leopard frogs during development, from egg to tadpole, results in a higher rate of deformities relative to control tadpoles. Nearly 18% of the tadpoles exhibited some type of developmental deformity, including both visceral and limb malformities, compared to a single deformed (less than 1%) control tadpole. Activity of plains leopard frog tadpoles exposed to carbaryl diminishes by nearly 90% at 3.5 mg/ L and ceases completely at 7.2 mg/ L (Bridges, 1997). Although under the reported test conditions potential consequences of reduced activity and swimming performance can lead to increased vulnerability to predation, slower growth, and failure to complete metamorphosis, tests concentrations are considerably higher than the highest surface water EECs calculated for carbaryl. Testing at or below maximum EEC is needed to better understand if amphibians are indeed likely to be at risk when exposed to carbaryl at concentrations likely to occur under field conditions. It is also possible that the PRZM/ EXAMS pond modeling may not be conservative enough for amphibians breeding in temporary pools and other short lived aquatic habitats exposed to carbaryl 11 through runoff and/ or spray drift. EFED is concerned about the behavioral and developmental effects of carbaryl on amphibians; when appropriate test procedures have been developed to examine these effects, EFED will request that carbaryl undergo these studies.

The acute risk LOC for estuarine/ marine fish is not exceeded for any use scenario modeled, at any use rate, indicating that, except for the oyster bed use in Washington State, carbaryl uses are unlikely to pose an acute risk to these organisms. The absence of core chronic toxicity data precluded the calculation of an RQ for estuarine/ marine fish. Information from the open literature, however, indicates that exposure to sublethal levels of carbaryl can produce certain adverse effects in some species. According to Weis and Weis (1974), laboratory exposure of the silverside (Menidia menidia) to a single dose of carbaryl (100 ppb) resulted in the temporary disruption of schooling behavior, consisting mainly of a spreading out of the school over a larger area. This change in behavior was observed after 24 h exposure. Returning the fish to carbaryl free water did not bring about a return of normal schooling patterns until 72 hours. This effect was attributed to the accumulation of carbaryl degradate1 naphthol.

Aerial carbaryl applications to tideland areas in Washington State, at 7.5  8 lb ai/ acre, for control of burrowing shrimp in commercial oyster beds are known to pose a significant acute risk to fish inhabiting treated mudflats or trapped in shallow pools. Estimates of potential fish kills range from 15,000 to 96,000 following each treatment (MRID 419826 06). Exposure to sublethal carbaryl levels may also inhibit acetylcholinesterase in fish in subtidal areas near treated sites, resulting in a temporary impairment of burying behavior and increasing exposure to predators (Pozorycki, 1999). Along with the burrowing shrimp, other invertebrate populations inhabiting treated mudflats, which constitute a food source for fish, are temporarily reduced or eliminated. There may be up to 100% mortality of Dungenese crab populations following carbaryl applications. However, some invertebrates recolonize the treated areas within two weeks (MRID 419826 06), and most populations of invertebrates recover in less than two months (Brooks 1993). Once established, the oyster beds provide a suitable environment for a species diverse community, as many plants and invertebrates, which are normally rare or absent in barren mudflats, readily grow on or in between oyster shells (MRID 419826 06). Since, on average, tideland areas are treated once every six years, adverse effects on the aquatic biota are temporary. Potential nonchemical pest management methods identified include alternative culture techniques, mechanical control, enhancement of shrimp predators, and electrofishing. Carbaryl application techniques that reduce drift, such as direct injection of carbaryl into the sediment, should be also further explored. In addition, improvements in the forecasting of shrimp infestation and the refinement of current action thresholds may help to decrease the frequency and amount of carbaryl applications without affecting effectiveness.

Environmental concentrations of carbaryl resulting from normal agricultural uses have been shown to have effects on invertebrate populations and individuals. Both acute and chronic risk LOCs are exceeded for freshwater invertebrates for all five carbaryl aquatic use scenarios modeled at maximum label, maximum reported, and "average" use rates, indicating that most carbaryl uses are likely to pose acute and chronic risks to freshwater invertebrates. Emergence of aquatic insects, such as damselflies, can also be severely reduced after 10 12 days exposure to 100 µg/ L of carbaryl (Hardersen and Wratten, 1998). In a mesocosm study, at carbaryl concentrations above 20 µg/ L 12 Daphnia were no longer found and at concentrations greater than 50 µg/ L, all cladocerans were eliminated, resulting in increased algal biomass due to repartitioning of biomass from zooplankton to phytoplankton (Havens, 1995). Studies with the freshwater snail (Pomaca patula) have shown that increased acetyl cholinesterase (AChE) inhibition occurs concurrently with the bioconcentration of carbaryl after 72 hour exposure at 3.2 µg/ g (Mora et al., 2000).

The acute LOC for estuarine/ marine invertebrates is exceeded for all five carbaryl use scenarios assessed at maximum label, maximum reported, and "average" application rates, indicating that estuarine/ marine invertebrates inhabiting intertidal zones and estuaries near areas where carbaryl is applied are likely to be at risk.

Terrestrial Organisms Three different kinds of nongranular carbaryl usage data were considered for assessing risk to terrestrial animals: maximum label rates, maximum reported (Doane data available for 42 uses) rates, and QUA "average" rates. In most cases the LOC exceedance pattern was not significantly affected by the kind of usage data used to calculate risk quotients.

Acute risk quotients indicate that, although none of nongranular carbaryl uses may pose an acute risk to birds, all nongranular uses present a chronic risk to birds. All granular uses are likely to pose an acute risk to 20 g birds, and all granular uses, except for cucurbits, legumes, wheat, millet, and sugar beet, also represent a risk to 180 g birds, while only the trees and ornamentals, turfgrass, and tick control uses pose a risk to 1000 birds.

All nongranular and granular uses are likely to pose an acute risk to 15 g and 35 g mammals. All nongranular uses pose a chronic risk to mammals. Table 2 summarizes LOC exceedances as well as the respective RQ ranges for nongranular uses.

The Agency is aware of only a few carbaryl related mortality incidents for mammals and birds, all involving small numbers of individuals. Although few in number and magnitude, considering that few mortality incidents are actually detected and reported, these known incidents suggest that a certain level of acute risk to birds and mammals from exposure to carbaryl does exist under field conditions. 13 Table 2. Avian and Mammalian Acute and Chronic Risk LOC Exceedances and highest RQs for Nongranular Carbaryl Uses at Maximum Label, Maximum Reported, and QUA Average application rates.

Acute Risk Chronic Risk Label Max Max Rep "Average" Label Max Max Rep "Average"

Birds LOC Exceed. 1 0/ 74 0/ 42 0/ 70 73/ 74 34/ 42 39/ 70 RQs N/ A N/ A N/ A 1.5 12.8 1. 0 12.0 1. 0 4. 2 Mammals LOC Exceed. 1 74/ 74 41/ 42 63/ 70 72/ 74 42/ 42 69/ 70 RQs 0. 76 12.12 0.60 11.36 0.53 4.02 3.0 48.0 1. 5 45.0 1. 5 15.9 1 No. uses for which the highest RQ is greater than LOC/ total No. uses examined (acute LOC for birds = 1; acute LOC for mammals = 0.5, chronic LOC for birds and mammals = 1)

Based on a rock dove LD50 of 1,000 mg/ kg and a mallard LD50 greater than 2,000 mg/ kg, technical carbaryl can be classified as slightly to practically nontoxic to birds on an acute basis. LD50 values for carbaryl as low as 16.2 mg/ kg and 56.2 mg/ kg have been reported for the starling and the red winged blackbird, respectively (Schafer et al., 1983). Although these data are based on simple screening tests, and are therefore not reliable for risk assessment purposes, they do suggest that passerine birds may be significantly more sensitive to carbaryl exposure than non passerine birds. Thus, the registrant is strongly encouraged to submit acute oral toxicity tests with passerine avian species. This risk assessment is using the dove LD50 (lower 95% confidence interval = 1,000 mg/ kg) to calculate acute RQs for granular carbaryl.

On a subacute, dietary basis, carbaryl is practically nontoxic to birds. The quail LC50 is greater than 5,000 ppm, and an LC50 greater than 10,000 ppm is reported for the Japanese quail (Coturnix) by Hill and Camardese (1986). On a chronic basis, the NOAEC is 300 ppm for the mallard duck, based on adverse reproduction effects including reduced egg production, decreased fertility, and increased incidence of cracked eggs. For this risk assessment, the quail LC50 (> 5,000 ppm) and the duck NOAEC (300 ppm) are used to calculate the subacute dietary and chronic RQs, respectively.

The avian acute risk level of concern (LOC) is not exceeded for any nongranular carbaryl use, at maximum or less than maximum label application rates. The avian chronic risk LOC is exceeded for almost all (73 of 74) uses considered at maximum label rates, for 34 of 42 uses at maximum reported rates, and for39of 70 uses at "average" rates. The avian acute LOC is exceeded for 20 g birds for all granular carbaryl uses (RQs: 0.52  4.76). For 180 g birds, the acute LOC is exceeded for the trees/ ornamentals, turfgrass, and tick control uses (RQ: 0.53). No acute LOCs are exceeded for birds in the 1000 g weight class for any of the granular carbaryl uses.

Carbaryl is moderately toxic to small mammals on an acute oral basis (rat LD50 = 301 mg/ kg) and, based on decreased fetal body weights and increased incomplete ossification of multiple bones in the laboratory rat (LOAEC = 600 ppm, NOAEC = 80 ppm), has the potential for mammalian chronic effects. 14 As summarized in Table 2, at maximum label rates the mammalian acute LOC is exceeded for all 74 nongranular carbaryl uses, and the chronic risk LOC is exceeded for 70 of the uses. RQs based on maximum reported rates for 42 uses exceed the acute LOC for 41 uses, while the chronic risk LOC is exceeded for all 42 uses. When "average" rates are used to calculate RQs for 70 nongranular uses, the acute risk LOC is exceeded for 63 uses, and the chronic risk LOC is exceeded for 69 uses, indicating that LOC exceedances are minimally affected when mammalian RQs are calculated using less than maximum label rates.

Information available in the open literature suggests potential reproduction effects of carbaryl on mammals. Several field and laboratory studies report significant reproduction effects for several species of mammals, including reduced reproduction, disturbances in spermatogenesis, pathological pregnancy, increased embryonal resorption, increased percentages of infertile females, and males with underdeveloped testicles (Gladenko et al., 1970, Smirnov et al., 1971, Krylova et al., 1975, Pomeroy & Barrett, 1975). Others report only slight effects (Anonymous, 1969, Dougherty et al., 1971, Narotsky and Kavlock, 1995). Some fail to detect any reproduction effects (DeNorscia and Lodge, 1973, Dougherty, 1975, Chapin et al., 1997).

Carbaryl is highly toxic to honey bees (LC50 = 1.3  2.0 µg/ bee), and moderately to highly toxic to a wide range of other beneficial insects, including species that prey on or parasitize many insect pests. Carbaryl has been linked to numerous bee mortality incidents in several states, which is not surprising given its effectiveness as a broad spectrum insecticide and its large number of uses. According to surveys conducted by the American Beekeeping Federation and the Washington State Department of Agriculture, carbaryl is one of the pesticides most frequently mentioned as being associated with bee kills (Brandi 1997, Johansen 1997). To minimize risk to bees and other pollinators, all carbaryl containing products display the standard pollinator protection language in their labels.

As indicated by precautionary label language, carbaryl can cause injury to some terrestrial plants. Carbaryl, used as a fruit thinning agent on apples and pears, may cause fruit deformity under certain environmental conditions, and injury to tender foliage if applied to wet foliage or during periods of high humidity. As indicated in the label, carbaryl may also cause injury to Boston ivy, Virginia creeper, maidenhair fern, and Virginia and sand pines. A few incidents involving carbaryl injury to vegetable crops have been reported. To date, no terrestrial plant toxicity studies have been submitted to the Agency. To fully assess carbaryl risk to terrestrial plants, Tier I and, if appropriate, Tier II Seed Germination and Seedling Emergence, as well as Vegetative Vigor studies should be submitted by the registrant. 15 Endangered Species The endangered species LOC for birds (0.1) is met or exceeded for 72 of 74 nongranular carbaryl uses at maximum label use rates, for 18 of 70 carbaryl uses at QUA average use rates, and for 25 of 42 maximum reported use rates. The endangered species LOC is exceeded for 20 g birds for all granular uses. For 180 g birds it is exceeded for all granular uses, except cucumber, melons, pumpkin, squash, beans, peas, lentils, cowpeas, southern peas, wheat, millet, and sugar beets. For 1000 g birds, the endangered species LOC is reached for the trees and ornamentals, turfgrass, and tick control granular uses.

The mammalian endangered species LOC for all three mammal weight categories and the grass/ broadleaf plants/ small insects food items is exceeded for all nongranular uses examined, at maximum label rates. At "average" and maximum reported use rates, the endangered species LOC for 15 g mammals feeding on short grass is exceeded for all carbaryl uses. The endangered species LOC is exceeded for 15  35 g mammals for all granular uses.

The endangered species LOC for freshwater fish is exceeded for three (sweet corn, field corn, and citrus) of five use scenarios modeled and for the citrus scenario at less than maximum label rates. For marine/ estuarine fish, the endangered species LOC is met for the citrus scenario only at maximum label rates. The endangered species LOC is exceeded for freshwater and marine/ estuarine aquatic invertebrates for all five use scenarios at maximum and less than maximum label use rates.

The uses of carbaryl on field crops (corn, soybeans, sorghum, wheat), forests and pasture/ rangeland were addressed by the US Fish and Wildlife Service (USFWS) in the reinitiation of consultation in September 1989. In their 1989 Biological Opinion, USFWS found jeopardy to a total of 86 species  6 amphibians, 47 freshwater fish, 27 freshwater mussels, and 5 aquatic crustaceans. Reasonable and Prudent Alternatives (RPA) were given for each jeopardized species. Reasonable and Prudent Measures (RPM) were given for 18 non jeopardized species to minimize incidental take of these species.

Many additional species, especially aquatic species, have been federally listed as endangered/ threatened since the Biological Opinion of 1989 was written, and determination of jeopardy to these species has not been assessed for carbaryl. In addition, endangered insects, birds and mammals were not considered in the 1989 opinion and need to be addressed. Finally, not only are more refined methods to define ecological risks of pesticides being used but also new data, such as that for spray drift, are now available that were not existent in 1989. The RPAs and RPMs in the 1989 Biological Opinion may need to be reassessed and modified based on these new approaches. This can occur once the program is finalized and in place.

Endocrine Disruption Concerns EPA is required under the Federal Food, Drugs, and Cosmetics Act (FFDCA), as amended by Food Quality Protection Act (FQPA), to develop a screening program to determine whether 16 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 the recommendations of its Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC), EPA determined that there was 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).

When the appropriate screening and or testing protocols being considered under the Agency's Endocrine Disruptor Screening Program have been developed, carbaryl may be subjected to additional screening and or testing to better characterize effects related to endocrine disruption.

There are data indicating that carbaryl has the potential for endocrine disruption effects on fish. Serum and pituitary levels of gonadotropic hormone and gonadotropin releasing hormone (GnRH) in the freshwater murrell (Channa punctatus) are reduced by exposure to 1.66  3.73 ppm of carbaryl in laboratory and paddy field tests (Ghosh et al., 1990). The decrease in GnRH levels could be explained by exposure to high estrogen levels, acting through a negative feedback pathway to inhibit GnRH release, and thus the release of gonadotropins (Klotz et al., 1997). Plasma and ovarian estrogen levels in freshwater perch (Anabas testudineus) exposed to 1.66 ppm of carbaryl for 90 days increase until day 15 and then decline, relative to control fish, indicating that long term exposure to this chemical may cause an inhibitory effect on fish reproduction (Choudhury et al., 1993). Both the murrell and the perch studies, however, were performed at concentrations well above the highest peak concentration modeled for carbaryl and, therefore, may not reflect risk under field conditions.

Furthermore, a number of field and laboratory studies report reproduction effects with mammals, suggesting that the possibility of endocrine disruption effects on wild mammals should be further examined.

Uncertainties The absence of valid chronic toxicity data for estuarine/ marine fish, estuarine/ marine invertebrates, and amphibians, as well as the lack of toxicity data for aquatic and terrestrial plants represent uncertainties in the risk assessment for carbaryl that need to be addressed through the submission of additional required data. Additionally, mammalian chronic RQs were based on a rat prenatal development study NOAEC (MRID# 44732901) rather than the more traditional use of a 2 generation reproduction study. Field studies suggest that exposure to a single carbaryl application may affect reproduction in small mammals. 17 Only very limited information is available for the environmental fate and transport of the major carbaryl degradate 1 Naphthol. Without additional data it is not possible to develop an fate profile for 1 Naphthol. Concentrations in surface and groundwater can not be estimated without data on the stability and mobility of the degradate compound.

4.0 Environmental Fate Assessment Exposure Characterization Using acceptable and supplemental environmental fate studies submitted by the registrant, along with published scientific literature, a profile of the fate and transport of carbaryl in the environment has been compiled. This information is sufficiently complete to allow the evaluation of the movement and fate of the compound. However, existing data gaps in Soil Photolysis, Terrestrial Field Dissipation, Aquatic Field Dissipation and degradate fate and mobility need to be addressed by the registrant.

Carbaryl dissipates in the soil environment by abiotic and microbially mediated degradation. The major degradation products are CO2 and 1 naphthol, which is further degraded to CO2. Carbaryl is stable to hydrolysis in acidic conditions, but hydrolyzes rapidly in alkaline environments. Carbaryl is degraded by photolysis in water, with a half life of 21 days. Under aerobic conditions the compound degrades rapidly by microbial metabolism with half lives of 4 to 5 days in soil and aquatic environments. In anaerobic environments metabolism is much slower with half lives on the order of 2 to3 months. Carbaryl is mobile in the environment (Kf =1.7 to 3.5). Sorption onto soils is positively correlated with soil organic content, increasing with higher soil organic content. Table 3 summarizes the environmental fate characteristics of carbaryl. An analysis of the significance of the data is presented in this section.

Monitoring data for carbaryl in surface water and groundwater show that it is commonly found in surface water and groundwater. In surface water concentrations are generally low (less than 1 : g/ L) and the maximum reported value is less than 10 : g/ L. In groundwater carbaryl is detected less often and at lower levels (generally less than 0.01 : /L). Available monitoring studies and data sets are described below.

Because of the relatively limited persistence of the compound in the environment it is unlikely that non targeted monitoring studies will detect the maximum concentrations that occur. Because of the limited amount of data available and because of potential problems with extant data (described below) monitoring data are of limited utility in developing EECs for ecological and human health risk assessment. Therefore, EFED used computer modeling to estimate surface water and groundwater concentrations that could be expected from normal agricultural use. For developing surface water EECs EFED used EPA PRZM3.12 and EXAMS 2.97.5 programs to estimate the concentration of carbaryl in surface water. For ecological risk assessment the standard pond scenario was used. For human health risk assessment index reservoir scenarios were used. 3 "Average" is the average rate as determined by OPP/ BEAD and reported in the a memo titled Quantitative Usage Analysis for Carbaryl, prepared July 21, 1998 by Frank Hernandez, OPP/ BEAD.

4 Maximum used is the highest rate of application that is actually reported to be used based on OPP/ BEAD analysis of DoaneS survey data by Donald Atwood, Personal communication, January 31, 2001.

18 Several application rates were used in modeling: the maximum allowed for the specific crop, an "average" rate 3 , and the maximum rate reported to actually be used 4 . The maximum rate was taken from the carbaryl labels. "Average and maximum reported rates were determined by EPA/ BEAD based on data collected by Doane surveys and registrant market analysis. EECs varied greatly depending on the geographic location, crop, and application rate. Modeling "average" and maximum reported use rates yielded EEC values generally 40 60% lower than maximum. EFED normally uses the maximum allowed application rates in modeling. In this assessment other, "less then maximum", rates were modeled in order to evaluate how conservative maximum rates modeling estimates are. The average and maximum rates may or may not be representative of actual use rates and are of limited certainty due to the quality and extent of the data available to calculate them. As described in the BEAD chapter the average application rates were derived by dividing total pounds used by the overall use area. The resulting average does not represent the actual average applied to any specific area and is not relevant for fist assessment. The maximum reported rate was determined from DOANES survey results. These data, while the best available, are very limited. The number of farmers surveyed is small, often only one or two per state, and the statistical validity of the results are not known but it is highly unlikely that the survey identified the actual maximum value.

The maximum calculated EEC resulted from use on citrus in Florida. For the Index Reservoir scenario using maximum label rates, acute EEC values ranged from about 19 : g/ L from sugar beets to about 500 : g/ L from citrus (Table 6). Chronic EECs ranged from about 2 to 28 : g/ L. These values are higher then concentrations observed in monitoring studies and probably represent conservative estimates of environmental concentrations. Modeling results are higher then monitoring data because of the limited persistence of the compound in most surface waters. It is highly unlikely that any but the most extensive targeted monitoring would capture the actual peak concentrations. The results of the modeling provide a conservative, though not unreasonable, estimate of possible concentrations in drinking water. A more detailed assessment of the source of water used to provide drinking water and the relationship between the areas where carbaryl is used and surface water sources is required to more accurately evaluate possible human exposures. Until more accurate data on land use and related pesticide application is available and can by linked with data on the location and hydraulic characteristics of the water bodies it is not possible to provide more accurate assessment of possible exposures. A more detailed description of modeling is presented below, and model input files are attached in appendix F. 19 Figure 2. Generalized carbaryl degradation pathway Table 3: Summary of Environmental Chemistry and Fate Parameters For Carbaryl (See Text for Analysis)

Parameter Value Reference Selected Physical/ Chemical Parameters Molecular Weight 201.22 Water Solubility 32 mg/ L (ppm) at 20 o C Suntio, et al., 1988 Vapor pressure 1.36 10 7 mm Hg (25 o C) Ferrira and Seiber, 1981 Henry's Law Constant 1.28 x 10 8 atm m 3 mol 1 Suntio, et al., 1988 Octanol/ Water Partition Kow = 229 Windholz et al., 1976 Persistence Hydrolysis t1/ 2 pH 5 pH 7 pH 9 stable 12 days 3.2 hours MRID 00163847, 44759301 Photolysis t½ aqueous 21 days MRID 41982603 Soil photolysis assumed stable No valid data submitted Soil metabolism T½

Aerobic 4 days in one sandy loam soil MRID 42785101 Anaerobic t1/ 2 = 72 days Satisfied by 162 3 Aquatic metabolism Aerobic t1/ 2 = 4.9 days MRID 43143401 Anaerobic t1/ 2 = 72 days MRID 42785102 Table 3: Summary of Environmental Chemistry and Fate Parameters For Carbaryl (See Text for Analysis)

Parameter Value Reference 20 Major Transformation Products Identified in the Fate Studies:

1 naphthol, CO2 Minor Transformation Products Identified in the Fate Studies:

5 hydroxy l naphthyl methylcarbamate (aerobic soil metabolism, anaerobic aquatic ) 1 naphthyl( hydroxymethyl) carbamate (aerobic soil metabolism, anaerobic aquatic) 1,4 naphthoquinone (aerobic aquatic metabolism, anaerobic aquatic) (hydroxy) naphthoquinones (degradates of 1 naphthol) 4 hydroxy 1 naphthyl methylcarbamate (anaerobic aquatic) 1,5 naphthalenediol (anaerobic aquatic) 1,4 naphthalenediol (anaerobic aquatic)

Mobility/ Adsorption Desorption Batch Equilibrium Kf (Koc) =1.74 (207)  sandy loam 2.04 (249)  clay loam sediment 3.00 (211)  silt loam 3.52 (177)  silty clay loam 1/ n values ranged from 0.78 0.84 MRID 43259301 Column Leaching slightly mobile in columns (30 cm length) of sandy loam, silty clay loam, silt loam, and loamy sand soils MRID 433207 01 Field Dissipation Terrestrial Dissipation Submitted study not acceptable MRID 419826 05 Forestry Dissipation Foliar t1/ 2 = 21 days Leaf Litter t1/ 2 = 75 days Soil t1/ 2 = 65 days MRID 43439801 Aquatic Submitted study not acceptable MRID 4326001 Foliar Dissipation 30 days Default value Bioaccumulation Accumulation in Fish not expected due to low Kow 21 Persistence Chemical Degradation Processes Hydrolysis Carbaryl hydrolysis is strongly pH dependant. The compound is stable under acidic conditions and degrades in neutral and alkaline systems with measured half lives of 12 days (pH 7) and 3.2 hours (pH 9). Only one major degradate was identified, 1 naphthol (MRID 44759301). Chapman and Cole (1982) measured half lives of 2.0 weeks (pH = 7.0) and 0.07 weeks (pH = 8). Wolfe et al. (1978) reported half life values in natural pond waters at pH 6.7 of 30 days and at pH 7.2 of 12 days. They also estimated minimum hydrolysis half life in acidic conditions of 1600 days. Armbrust and Crosby (1991) reported hydrolysis half lives in filtered seawater of 24 hours at pH 7.9 and 23 hours at pH 8.3. The major degradation product was 1 naphthol which was stable to further hydrolysis.

Photolysis Aqueous Photolysis In an aqueous photolysis study, carbaryl, with an initial concentration of 10.1 mg/ L, degraded in a pH 5 solution with a half life of 21 days after correction for dark controls( MRID 41982603). The only degradate identified was 1 naphthol. Wolfe et al. (1978) reported a photolysis half life in distilled water at pH 5.5 of 45 hours. In filtered seawater carbaryl degraded rapidly to 1 naphthol under artificial sunlight (290 360 nm) with a half life of 5 hours. The degradation product, 1 naphthol, was degraded very rapidly with half life of less than 1 hour (Armbrust and Crosby, 1991).

Soil Photolysis A study of photolysis (MRID 41982604) on soil was submitted; however the study was determined to be invalid. No data on the possible soil photolysis of carbaryl is available. In view of this data gap, it is assumed that the compound is stable to photolysis on soil.

Microbially mediated Processes Carbaryl is degraded fairly rapidly by microbial processes under aerobic conditions and more slowly under anaerobic conditions. In a guideline study of aerobic soil metabolism carbaryl, with an initial concentration of 11.2 mg/ kg, degraded with a half life of 4.0 days in sandy loam soil incubated in the dark at 25 B C (MRID 42785101). The major degradate was 1 naphthol which further degraded rapidly to non detectable levels within 14 days. In an aerobic aquatic metabolism study carbaryl, with an initial concentration of 9.97 mg/ L, degraded with a half life of 4.9 days in flooded clay loam sediment in the dark at 25° C (MRID 43143401). 1 Naphthol was identified as a major nonvolatile degradate. Carbaryl degraded with a half life of 72.2 days in anaerobic aquatic sediment with an initial carbaryl concentration of about 10 mg/ L; 1 naphthol was the major degradate. Minor degradates included 5 hydroxy 1 naphthyl methylcarbamate, 4 hydroxy 1 naphthyl methylcarbamate, 1,5 naphthalenediol, 1,4 naphthalenediol, 1 naphthyl( hydroxymethyl) carbamate, and 1,4 naphthoquinone 22 Liu, et al. (1981) studied carbaryl degradation in anaerobic and aerobic fermenters spiked with a mixture of lake sediment, silt loam and domestic activated sludge and buffered to pH 6.8. They reported abiotic degradation half lives of 8.3 (aerobic) and 15.3 (anaerobic) days. After correcting for abiotic controls, when carbaryl was used as the sole carbon source they found aerobic and anaerobic metabolism half lives of 54 and 11.6 days, respectively. When glucose and peptone were added co metabolism aerobic and anaerobic metabolism, half lives were 7.6 and 6.1 days respectively.

A number of soil microorgamisms have been identified which can degrade carbaryl including Pseudomonas sp (Chapalmadugu and Chaudhry, 1991; Larken and Day, 1986), Rhodoccus sp. (Larkken and Day, 1986), Bacillus sp. (Rajagopal. et al., 1984), Arthrobacter sp. (Hayatsu et al., 1999), and Achromobacter sp (Karns et al., 1986). Some bacteria are capable of complete degradation to CO2 (Chapalamadugu and Chaudhry, 1991) while some stop at 1 naphthol. In soils it appears that consortia of bacteria are able to degrade parent and 1 naphthol completely to CO2. Proposed degradation pathways proceed by using the methylcarbarmate side chain as a carbon source, converting the parent to 1 naphthol. 1 naphthol is then degraded through intermediates salicylaldehyde, salicylic acid, catechol, and gentisate to CO2 and water (Chapalamadugu and Chaudhry, 1991; Hayatsu et al., 1999). Several studies have shown that bacteria isolated from soil exposed to carbofuran can degrade carbaryl indicating cross adaption by microorganisms allowing degradation of compounds with similar structure (Karns et al., 1986: Chaudhry, et al., 1988). Carbaryl degradation utilizes enzyme systems which may or may not degrade other carbarmate compounds (Chapalamadugu and Chaudhry, 1991).

Mobility Carbaryl is considered to be moderately mobile in soils. Based on batch sorption/ desorption studies, the compound has Freundlich Kf values of <3.52. Sorption is dependant on the soil organic matter content and increased with increasing Koc.

Batch Adsorption/ Desorption Based on batch equilibrium experiments (MRID 43259301) carbaryl was determined to be moderately mobile to mobile in soils. In silty clay loam, sandy loam, loamy sand, and silt loam soils and clay loam sediment, mobility decreased with increasing soil organic matter content. Adsorption Koc values ranged from 177 249. Kf values were 1.74 for the sandy loam soil, 2.04 for the clay loam sediment, 3.00 for the silt loam soil, and 3.52 for the silty clay loam soil. Corresponding Koc values were 207, 249, 211, and 177, respectively, and 1/ n values ranged from 0.78 0.84. Mobility decreased with increasing soil organic matter content. Sorption showed significant hystereses with Freundlich desorption constants (Kf( des)) values of 6.72 for sandy loam soil, 6.78 for clay loam sediment, 6.89 for silt loam soil, and 7.66 for silty clay loam soil. 1/ n values ranged from 0.86 1.02. Corresponding desorption Koc values were 800, 827, 485, and 385, respectively. Literature data confirms that carbaryl is mobile. Nkedi Kizza and Brown (1998) reported Kf of 4.72 (1/ n = 0.80) for soil with an organic content of 590 mg/ Kg. They found that sorption was lower on subsoils and attributed this to a lower organic content. The reported Koc values ranged from 144 to 671. 23 Column Leaching In column leaching experiments (MRID 43320701), carbaryl residues were determined to be slightly mobile in columns (30 cm length) of sandy loam, silty clay loam, silt loam, and loamy sand soils treated with aged carbaryl residues. This disparity with the batch experiments may possibly be explained by the relatively poor extraction recovery, by slow desorption kinetics and by degradation during the aging period. Unextracted [ 14 C] labeled residues in the soils prior to leaching ranged from 19.0% of the recovered in the loamy sand soil to 39.7% in the silty clay loam soil. The study author believed that 50% of the carbaryl applied to the soil had degraded prior to leaching.

Field Dissipation Studies of carbaryl dissipation in terrestrial, aquatic and forest environments have been submitted by the registrant. In forest environments carbaryl was found to be moderately persistent in soil (half live = 65 days) and leaf litter (half live = 75 days). The submitted field and aquatic dissipation studies were determined to be unacceptable, and did not provide useful information on movement and dissipation of carbaryl or its degradation products.

Field dissipation studies conducted in the 1960s and 1970s in terrestrial (Fiche/ Master ID 000108961 and 00159337), aquatic (Fiche/ Master ID 001439080, 0124378, 00159337, 00159338, 00159339) and forestry (Fiche/ Master ID 00029738, 00159340, 00159341) environments and submitted in the 1980s have been reexamined. When they were initially reviewed they were not considered acceptable for a number of reasons including: sampling frequency was not sufficient to allow calculation of dissipation rates, degradates were not identified or quantified, soil, sediment and water were not sufficiently characterized, problems with analytical method specificity and validity, insufficient sampling frequency and sampling depth, lack of data on irrigation practices measures. These studies do not meet current levels of scientific validity required to be considered acceptable and do not provide useful information on field dissipation of carbaryl and its degradates.

The data requirements for terrestrial and aquatic field dissipation have not been fulfilled, and additional studies are required.

Terrestrial Field Dissipation Results of two field dissipation studies conducted in California and North Carolina were submitted (MRID 41982605). Because of inappropriate sampling intervals, poor sample storage stability, lack of degradate monitoring, rainfall and irrigation that were less than evapotranspiration, and irrigation water with high pH, these studies do not provide reliable information on the rate of dissipation of parent carbaryl or formation of degradation products. The requirement for terrestrial field dissipation has not been fulfilled, and additional information is required. Because of problems with submitted studies additional field studies are required.

A freezer stability study was reportedly conducted but the results past 90 days were not submitted. There was apparently significant degradation within 90 days. Study samples were analyzed as long as 8 months after collection, making the quality of the data highly questionable. Degradates were not analyzed in either study, and the sampling interval was insufficient to accurately determine the dissipation rate for carbaryl. In the California study >80% of the applied 24 carbaryl apparently dissipated between the final carbaryl application and the next sampling interval (4 7 days after the final application). In the NC study > 90 % apparently dissipated between application and the next sampling event (7days). However, in both studies dissipation after 7 days suggested a half life on the order of weeks. In both studies rainfall and irrigation were less than evapotranspiration so the data can not be used to assess the potential for carbaryl to leach into the subsurface. In the California study, irrigation with water with a pH of 8.0 was applied 1 3 days after each pesticide application. Because carbaryl hydrolysis is highly pH dependant ( T1/ 2 at pH 9 = 3.2 hours) this may have resulted in significantly more rapid degradation.

Forestry Field Dissipation In a supplemental forestry field dissipation study (MRID 43439801) carbaryl was applied on a pine forest site in Oregon. Carbaryl half lives were found to be 21 days on foliage, 75 days in leaf litter and 65 days in soil. At the time of treatment, the trees of primary interest (pine) were 3 8 feet tall. Carbaryl concentration was a maximum of 264 ppm in the pine foliage at 2 days posttreatment 28.7 ppm in the leaf litter at 92 days, 0.16 ppm in the upper 15 cm of litter covered soil at 62 days, and 1.14 ppm in the upper 15 cm of exposed soil at 2 days. Carbaryl was detected in the leaf litter up to 365 days after treatment, and in the litter covered soil up to 302 days after treatment. Carbaryl was <0.003 ppm in water and sediment from a pond and stream located approximately 50 feet from the treated area. This study was determined to provide only supplemental information because degradation products were not identified and their rate of formation and decline was not determined.

Aquatic Field Dissipation Results of aquatic field dissipation studies conducted on rice in Texas and Mississippi were submitted (MRID 43263001). The studies were evaluated and found to be unacceptable. They do not provide useable information on the dissipation of carbaryl and 1 naphthol in aquatic field conditions. Frozen storage stability data were provided for only 6 months, although the water samples were stored for up to 14 months and the soil samples were stored for up to 17.5 months prior to analysis. The data suggest that carbaryl and 1 naphthol degraded significantly during storage. In the six months of storage carbaryl degraded an average of 34 % in Texas water and 39% in from Mississippi. 1 naphthol degraded 50% in water from Texas and 69% from Mississippi. Degradation did not appear linear, and it is not possible to extrapolate out to 14 months. It was therefore not possible to evaluate the actual concentrations of carbaryl and 1 naphthol in the samples or estimate the dissipation rates.

Bioaccumulation in Fish Because of the low octanol/ water partition coefficient carbaryl is not expected to significantly bioaccumulate. Reported Kow values range from 65 to 229 (Bracha, and O'Brian, 1966; Mount, M. E. and Oehme, 1981; Windholz et al., 1976). A fish bioaccumulation study reviewed in 1988 (Chib, 1986, Fiche/ Master ID 00159342) suggested that bioaccumulation factors were 14x in 25 edible tissue, 75x in visceral tissue and 45x in whole fish. Though the study does not meet current acceptable standards it does support the conclusion that significant bioaccumulation is not expected. No additional data on bioaccumulation is required at this time.

Foliar Dissipation The reported rates of carbaryl dissipation from foliar surfaces varies from 1 days to 30 days. In their review of literature data on pesticide foliar persistence, Willis and McDowell (1987) report that carbaryl dissipation rates varied from 1.2 to 29.5 days. In the submitted forestry field dissipation study (MRID 43439801) carbaryl applied to pine needles dissipated with a half live of 21 days. For terrestrial risk assessment modeling EFED used 35 days as the dissipation half life.

Atmospheric Transport Carbaryl has been shown to be transported and deposited by atmospheric processes (Waite, et al., 1995; Foreman, et al., 2000; Sanusi et al., 2000). As with all chemicals applied by aerial or ground spray, spray drift can cause exposure to non target organisms downwind. Beyer et al., (1995) studied spray drift from aerial application to rangeland near the Little Missouri River in North Dakota. In 1991 carbaryl was applied to 35130 ha at 560 g/ ha (0.62 lb) A. I. A 152 m nospray buffer zone was maintained. River water samples collected 1 hour after completion of spraying had a mean concentration of 85.1 : g/ l. Concentration decreased over time, and 96 hours after application the mean was 0.1 : g/ l. In 1993 a similar application resulted in a maximum concentration 1 hour after spraying of 12.6 : g/ l decreasing to 5.14 : g/ L after 96 hours. The researchers found that invertebrates in the river were minimally effected while fish brain acetylcholinesterase activity was not effected.

Vapor phase transport and particulate transport may carry the compound far from the area of application. In the atmosphere, partitioning between particulate and gas phase is a function of temperature and changes from about 30% vapor phase to about 90% when temperature increases from 283 to 303 K (Sanusi et al., 1999). This suggests that atmospheric transport distance and deposition are a function of temperature.

Carbaryl has been detected in air in urban and suburban areas with limited influence from agricultural spraying. It is detected more frequently and generally at higher concentrations at sampling locations in urban areas than in agricultural areas (Foreman et al., 2000). Pesticide concentrations in fog often are higher than those observed in rain water or surface water and may represent a significant, though generally overlooked, route of exposure. Schomburg et al. (1991) reported carbaryl concentrations in fog ranging from 0.069 to 4.0 : g/ L. 26 1 Naphthol Fate and Transport Limited information is available for the environmental fate and transport of the major carbaryl degradate 1 Naphthol. 1 Naphthol was formed in laboratory degradation studies and represented a major portion of the applied mass (maximum of 22 % in aerobic aquatic metabolism, 58% in aerobic soil metabolism and 67% in photolysis). 1 Naphthol was not persistent in the studies and appears to have degraded more rapidly then the parent.

1 Naphthol a natural product and is also formed as a degradation product of naphthalene and other polycyclic aromatic hydrocarbons. It appears to degraded more rapidly then the parent in the submitted studies but there is not sufficient information the develop a detailed fate profile. While guideline studies were not submitted specifically for the degradate, literature information suggests that it is less persistent and less mobile than parent carbaryl. Armbrust and Crosby (1991) reported that 1 Naphthol was stable to hydrolysis in filtered seawater at pH 7.9 and 8.3. Hydrolytic degradation of 1 naphthol is reported to be due to reaction with dissolved O2 and is highly pH dependant (Karthikeyan and Chorover, 2000). Oxidation increases with pH and ionic strength. Below pH 7 oxidation is minimal and reaches a maximum at about pH 9. Oxidation of 1 naphthol reportedly results in production of (hydroxy) naphthoquinones and dimer coupled reaction products, though the reaction rates for 1 naphthol degradation is not well known (Karthikeya and Chorover, 2000). In filtered seawater carbaryl degraded rapidly to 1 naphthol under artificial sunlight (290 360 nm), with half life of 5 hours. The degradation product, 1 naphthol, was degraded very rapidly with half life of less than 1 hour (Armbrust and Crosby, 1991).

1 naphthol is degraded rapidly by microbial processes in aerobic systems. In an aerobic soil metabolism study (MRID 42785101) 1 naphthol degraded rapidly to non detectable levels within 14 days. Armbrust and Crosby (1991) reported that 1 naphthol degraded in unfiltered seawater to below detectable level within 94 hours. Burgos et al. (1999) found that greater than 90% of aqueous 1 naphthol was degraded to CO 2 within 10 days. However, they found that sorption to soil greatly reduced the degradation rate; when sorbed degradation was greatly slowed to 25 40% degradation in 90 days.

No guideline information was submitted on 1 naphthol sorption. Literature information suggests that it is not strongly sorbed. Sorption to poorly crystalline aluminum hydroxide was pH dependant and appeared to occur only after oxidation (Karthikeyan et al., 1999). Hassett et al. (1981) reported an average 1 naphthol Koc of 431 (± 40) for 10 of the 16 soils tested. They also found that in other soils with very low organic carbon to clay ratios clay surfaces controlled sorption. Additional data on 1 naphthol sorption is required to fully characterize mobility. 27 Aquatic Exposure Assessment Surface Water Five crop scenarios: apples, field corn, sweet corn, oranges and sugar beets scenarios were used in modeling for surface water EEC. These crops were chosen as representative of the major groups of crops with high carbaryl use and application rates that would result in high potential for surface water contamination. The EEC's generated in this analysis were calculated using PRZM for simulating runoff from an agricultural field and EXAMS for estimating environmental fate and transport within the water body. Modeling was done using the maximum rate on label, average application rate and maximum rate of application reported.

Two sets of surface water simulations have been done for carbaryl: for drinking water assessment and for aquatic ecological exposure assessment. The modeling done for drinking water assessment was done using the index reservoir watershed scenario (Jones, et al., 2000) and calculated values were corrected for Percent Crop Area (PCA). For ecological risk assessment modeling was done using the standard farm pond scenario. The standard pond scenario used by EFED simulates a ten hectare field draining into a one hectare static pond that is two meters deep and has no outlet. It is assumed that evaporation losses and inflow from rainfall and runoff are balanced. The inputs used are similar to those used in modeling drinking water EECs and are shown in Table 4. EECs generated (Table 5) were compared with toxicological information described below to estimate the risk to non target aquatic organisms. 28 Table 4. PRZM/ EXAMS environmental fate input parameters for Carbaryl Parameter Value Data source Molecular Weight 201.22 Solubility 32 mg/ L (@ 20° C) Suntio, et al., 1988 Vapor Pressure (torr) 1.36 10 6 @ 25° C Ferrira and Seiber, 1981 Henry's Law Constant 1.28 x 10 8 Suntio, et al. 1988 Hydrolysis Half life pH 5 pH 7 pH 9 stable 12 days 3.2 hours MRID 00163847 44759301 Soil Photolysis Half life (days) stable no valid data submitted Aquatic Photolysis Half life (days) 21 days MRID 41982603 Aerobic Soil Metabolism Half life 4. 0 days (n= 1 so use 3x) MRID 42785101 Aerobic Aquatic Metabolism Half life 4. 9 days (n = 1 so use 3x) MRID 43143401 Anaerobic Aquatic Metabolism Half life 72.2 days MRID 42785102 Soil Water Partitioning Coefficient Kads (Koc) 1.74 (207) sandy loam 2.0 (249) clay loam 3.0 (211) silt loam 3.5 (177) silty clay loam (Koc = 209 for SCIGROW) MRID 43259301 There are a number of factors which may limit the accuracy and precision of the PRZM/ EXAMS modeling, including the selection of realistic exposure scenarios, the quality of the input data, the ability of the models to represent the real world and the number of years that were modeled. The scenarios that are selected for use in Tier II EEC calculations were chosen to be representative of uses likely to produce the highest concentrations in the aquatic environment. The EEC's in this analysis are accurate only to the extent that the model represents real environments. The most limiting part of the site selection is the use of the standard pond with no outlet. A standard pond is used because it provides a basis for comparing pesticides in different regions of the country on equal terms. The models also have limitations in their ability to represent some processes such as the handling of spray drift. A second major limitation is the lack of validation at the field level for pesticide runoff. 29 Table 5. Tier II surface water estimated environmental concentration (EEC) values derived from PRZM/ EXAMS modeling for use in ecorisk assessment (Calculated using standard pond.)

Use Site, Application Method Number of Applications Per Year Application Rate (Pounds A. I. per Application) Surface Water Acute (ppb) (1 in 10 year peak single day concentration) 21 day (ppb) (1 in 10 year) 60 day (ppb) (1 in 10 year)

Sweet Corn (OH), air/ ground Maximum "Average" Maximum Reported 8 2 3 2 3.4 1 46 16 14 26 10 8 21 5 4 Field Corn (OH), air/ ground Maximum "Average" Maximum Reported 4 2 2 2 1 1.5 28 12 18 16 6 9.5 10 3 5 Apples (OR), air/ ground Maximum "Average" Maximum Reported 5 2 2 2 1.2 1.6 8.6 4.5 6.0 4.9 2.5 3 4 1 2 Sugar Beets (MN), air/ ground Maximum "Average" Maximum Reported 2 1 1 1.5 1.5 1.2 19 14 11 11 7 5 5 3 2 Oranges (FL), air/ ground Maximum "Average" Maximum Reported 4 2 3 5 3.4 4.3 274 145 232 137 67 112 79 33 55 Urban and Suburban EFED has limited tools for assessing the effects of pesticide use in urban and suburban settings on surface water and groundwater quality. Carbaryl is extensively used in such nonagricultural applications, resulting in widespread surface water contamination. This conclusion is based on monitoring data. In urban and suburban areas small streams are generally greatly affected by surface runoff and water collection into storm sewers. These small streams can provide a significant habitat for aquatic animals, and this habitat can be severely degraded by runoff of urban pesticides. Garden and lawn care products and other outdoor uses contribute to carbaryl presence in storm sewers and streams. Monitoring data show that about 50% of urban streams have measurable concentrations (> 0.01 : g/ L) of carbaryl compared to less than 10% of agricultural sites (Larson, et al., 1999). Additional information is needed to adequately assess the environmental impacts of urban and suburban uses. Targeted surface water and groundwater monitoring studies are required to more adequately understand the movement of the compound in these environments and to provide estimates of the distribution of possible exposures from urban and suburban environments.

Estimated Environmental Concentrations for Terrestrial Ecological Risk Assessment For terrestrial EECs, EFED uses the concentration of a chemical on food items derived from the Kenaga nomograph, as modified by Fletcher et al. (1994). The nomograph allows estimation of the concentration of pesticide on food items resulting from application, based on a large set of actual field residue data. The upper limit values from the nomograph represent the 95th percentile 30 of residue values from actual field measurements (Hoerger and Kenaga, 1972). Hoerger Kenaga pesticide environmental concentration estimates were based on residue data correlated from more than 20 pesticides on more than 60 crops. Representative of many geographic regions (7 states) and a wide array of cultural practices, Hoerger Kenaga estimates also considered differences in vegetative yield, surface/ mass ratio and interception factors. In 1994, Fletcher et al. reexamined the Hoerger Kenaga simple linear model (y= B 1 x, where x= application rate and y= pesticide residue in ppm) to determine whether the terrestrial EEC's were accurate. They compiled a data set of pesticide day 0 and residue decay data involving 121 pesticides (85 insecticides, 27 herbicides, and 9 fungicides from 17 different chemical classes) on 118 species of plants. They concluded that Hoerger Kenaga estimates needed only minor modifications to elevate the predictive values for forage and fruit categories from 58 to 135 ppm and from 7 to 15 ppm, respectively. Otherwise, the Hoerger Kenaga estimates were accurate in predicting the maximum residue values after a 1 lb ai/ acre application.

EFED calculates concentration over time assuming first order dissipation from plant surfaces. In the absence of reliable foliar dissipation data a dissipation half life of 35 days is used. Published literature shows that carbaryl dissipation rates vary. and are among the highest observed for any pesticide. (Willis and McDowell, 1987). ELL FATE, a spreadsheet based first order decay model was used to calculate concentration over time for multiple applications at the label maximum, "average," and maximum reported application rates. A more thorough description of the model calculations and ELL FATE outputs are attached in Appendix D. EEC values calculated for different crop applications are presented in Tables 4, 7, 8, and 9, Appendix B.

5.0 Drinking Water Assessment Water Resources Assessment Chemical characteristics and available monitoring data indicate that carbaryl has the potential to enter surface water via leaching and runoff under certain conditions and has limited potential to leach to ground water. Carbaryl tends not to bind tightly to soil, aquifer solids, or sediment. Once the compound has entered surface water, it may be degraded by chemical and biological processes. Abiotic degradation by photolysis (t1/ 2 = 21 days) and hydrolysis in alkaline (t1/ 2 = 3.2 hours at pH 9) and neutral (t1/ 2 = 12 days at pH 7) waters result in fairly rapid degradation in most aqueous environments. Microbially mediated processes also contribute to fairly rapid degradation of the parent to 1 naphthol and CO2. Aerobic aquatic, soil aerobic and anaerobic metabolism studies (t1/ 2 = 5, 4, and 72 days respectively) suggest that the compound is broken down by a variety of metabolic processes.

Under certain limited conditions carbaryl may be expected to persist in the environment. Under low pH conditions the compound is stable to hydrolysis. In anaerobic environments metabolism is fairly slow (t½ = 72 days).

Surface water monitoring studies show that carbaryl is the second most widely detected insecticide after diazinon. Carbaryl, at typically low concentrations, is found in greater than 20 % 31 of surface samples in NAWQA studies at concentrations up to 5.5 ppb. Carbaryl is detected more frequently in non agricultural areas (about 40%) then in agricultural areas (about 5 %). A maximum carbaryl concentration of 8.4 ppb was reported for surface water samples in the California DPR surface water database. Carbaryl is generally not widely detected in groundwater monitoring studies though some studies have found concentrations of up to several hundred ppb. Concentrations as high as 610 µg/ L have been detected in one case but typical groundwater concentrations are much lower. NAWQA studies have found that about 1 % of groundwater samples have measurable levels (> 0.003 : g/ L) of carbaryl, with a maximum concentration of 0.02 µg/ L. Targeted studies designed to measure carbaryl in groundwater are not available.

Drinking Water Exposure Assessment Based on chemical properties, existing monitoring data and computer simulation estimates of carbaryl contamination that can be expected in surface water and groundwater as a result of normal use practices have been determined. Carbaryl is the second most commonly detected insecticide in surface water, and can be expected to contaminate drinking water derived from surface water bodies. Targeted and non targeted studies regularly detect carbaryl in low concentrations, typically below 1 µg/ L. Monitoring studies suggest that about 20 % of surface water bodies have detectable (> 0.01 : g/ L) levels of the compound. The maximum reported value in surface water was 8.4 µg/ L.

Carbaryl is not widely detected in groundwater studies. Drinking water derived from groundwater has been found to have low or non detectable levels of carbaryl. For drinking water derived from groundwater, the acute and chronic EEC value of 0.8 µg/ L is based on modeling using SCI GROW. It must be noted that carbaryl has an aerobic metabolism half life (4 days) which is significantly outside the range of values for which SCI GROW may be valid (17 1000 days). Because of this there is significant uncertainty in the SCI GROW value. EFED currently does not have more advanced groundwater models, and targeted studies specifically designed to evaluate the potential for carbaryl to move to groundwater are not available.

Because of its chemical structure carbaryl is somewhat difficult to quantify by gas chromatography. Older studies using GC or GC/ MS generally have poor recovery and quantitation limits. Because of this difficulty in analysis the actual concentration of carbaryl in groundwater and surface waters may be higher than reported. More recent studies using HPLC/ MS should provide better data on the true extent and magnitude of water contamination from the use of carbaryl.

Drinking Water Modeling Modeling to support the assessment of drinking water in the human health risk assessment was done for five scenario: Florida citrus, Ohio sweet corn and field corn, Oregon apples and Minnesota sugar beets. These scenarios were selected to represent the range of crops and use rates likely to result in higher environmental concentrations. EECs were calculated using The Pesticide Root Zone Model version 3.12 (PRZM) (Carsel et al., 1997) and EXAMS 2.97.5 (Exposure Analysis Modeling System) (Burns, 1997) were run. PRZM is used to simulate pesticide transport as a result 32 of runoff and erosion from an agricultural field and EXAMS estimates environmental fate and transport of pesticides in surface water. Weather and agricultural practices are simulated over 36 years so that the 10 year exceedance probability at the site can be estimated. A partial list of input parameters for the PRZM/ EXAMS modeling are given in Table 4. Simulations were run using the maximum application rates, average rates, and maximum reported rates. The values generated by the models were multiplied by a default percent crop area factor (PCA) which accounts for the fact that is unlikely for any basin to be completely planted to agricultural crops. For human health assessment, simulations were done using the Index Reservoir scenario in Exams. The Index Reservoir and PCA are described in Jones et al., 2000. The EEC's for the five scenarios simulated are shown in Table 6. Input files for PRZM/ EXAMS modeling is included in Appendix A.

The maximum calculated EEC resulted from use on citrus in Florida. For the Index Reservoir scenario using maximum label rates, acute EEC values ranged from about 10 : g/ L from sugar beets to about 500 : g/ L from citrus (Table 6). Chronic EECs ranged from about 2 to 28 : g/ L. These values are higher then concentrations observed in monitoring studies and probably represent conservative estimates of environmental concentrations. It is highly unlikely that any but the most extensive targeted monitoring would capture the actual peak concentrations. The results of the modeling provide a very conservative, though not unreasonable, estimate of possible concentrations in drinking water. A more detailed assessment of the source of water used to provide drinking water and the relationship between the areas where carbaryl is used and surface water sources is required to more accurately evaluate possible human exposures. In Florida, for example, the majority of drinking water is derived from groundwater (> 90%) so high surface water concentrations do not necessary indicate high exposure. Until more accurate data on land use and related pesticide application is available and can by linked with data on the location and hydraulic characteristics of the water bodies it is not possible to provide more accurate assessment of possible exposures. A more detailed description of modeling is presented below, and model input and output files are attached in Appendix A.

Water Treatment Effects The Office of Pesticide Programs has completed a preliminary review of the effects of d r i n k i n g w a t e r t r e a t men t o n p e s t i c i d e s i n w a t e r (http:// www. epa. gov/ scipoly/ sap/ 2000/ september/ sept00 sapdw 0907. pdf). This review indicates that standard drinking water treatment, consisting of flocculation/ sedimentation and filtration does not substantially affect concentrations of pesticides in drinking water. Evidence suggests that carbaryl does not react with chlorine or hypoclorite disinfection products in water treatment but is rapidly degraded (T½ = too rapid to measure) by ozone (Mason et al., 1990). Since relatively few water treatment facilities in the U. S. use ozone the limited data available do not indicate that carbaryl is likely to be degraded in the majority of treatment plants. 33 Table 6. Drinking Water EECs Crop Number of Applications per Year Pounds A. I. per application Surface Water Acute (ppb) (1 in 10 year peak single day concentration) Surface Water Chronic (ppb) (1 in 10 year annual average concentration)

Sweet Corn (OH) (PCA = 0.46) Maximum 1 8 2 37 3.2 Average 2 2 3. 4 45 2.2 Maximum 3 Reported 3 1 15 0.9 Field Corn (OH) (PCA = 0.46) Maximum 1 4 2 30 2.1 Average 2 2 1 13 0.6 Maximum 3 Reported 2 1. 520 1 Apples (OR) (PCA = 0.87) Maximum 1 5 2 144 9 Average 2 2 1. 2 12 0.7 Maximum 3 Reported 2 1. 625 1 Sugar Beats (MN) (PCA = 0.87) Maximum 1 2 1. 519 2 Average 2 1 1. 5 12 1.1 Maximum 3 Reported 1 1. 2 9 0. 9 Oranges (FL) (PCA = 0.87) Maximum 1 4 5 494 28 Average 2 2 3. 4 246 11 Maximum 3 Reported 3 4. 26 411 16 Surface Water Monitoring 5.5 (Maximum Observed Concentration)

Groundwater SCIGROW Maximum 1 5 40. 8 0. 8 Groundwater (NAWQA Monitoring Data) 0.02 0.02 1 Maximum application rate on label 2 Average application rate from Quantitative Usage Analysis for Carbaryl, prepared July 21, 1998 by Frank Hernandez, OPP/ BEAD 3 Maximum rate of application reported in Doanes survey data Groundwater Resources Available evidence from valid scientific studies show that carbaryl has a limited potential to leach to ground water. As a result of normal agricultural use, detections of carbaryl residues have 34 been reported in groundwater from several states. As reported in the U. S. EPA. Pesticides in Groundwater Database (Jacoby et al., 1992) carbaryl was detected in 0.4% of wells sampled. Carbaryl was detected in California (2 out of 1433 wells), Missouri (11 out of 325 wells), New York (69 out of 21027 wells) Rhode Island (13 out of 830 wells) and Virginia ( 11 out of 138 wells). The maximum concentration detected was 610 µg/ L in NY, though typically the measured concentrations were significantly lower.

The EPA STORET database was queried on May 12, 1999 for reports of measurements of carbaryl in groundwater. The database contained 9389 records indicating that analysis was done for carbaryl. Out of these only 4 reported concentrations above the detection limits. These analyses were all from one well in Cleveland, OK in 1988. The 4 reported concentrations were between 0.8 and 1 ppb.

Carbaryl was detected at greater than the detection limit (0.003 µg/ L) in 1.1 % of groundwater samples from 1034 sites across the U. S. by U. S. G. S. NAWQA program. The maximum observed concentration was 0.021 µg/ L. Detections were mainly from three use sites: wheat (5.8 % of well samples from wheat land use ), orchards and vineyards (1.7 % of well samples from orchard and vineyard land use), and urban (1.8% of urban groundwater samples). Data on pesticides in groundwater were reviewed by Kolpin et al. (1998) and updated information is available at: http:// water. wr. usgs. gov/ pnsp/ pestgw/.

Surface Water Resources Monitoring Data Carbaryl is widely detected in non targeted and targeted monitoring studies. Observed concentrations are generally low (> 0.5 : g/ L). Carbaryl is not very persistent in most surface water conditions suggesting that the wide spread occurrence is a result of its extensive use in a variety of applications. Because of limitation in the analytical methods used there is some uncertainty in the quantitative accuracy of carbaryl analysis.

NAWQA Carbaryl is the second most widely detected insecticide after diazinon in the USGS NAWQA program (http:// water. usgs. gov/ nawqa/ nawqa_ home. html). Carbaryl was detected in 46% of 36 NAWQA study units between 1991 and 1998. The reported concentrations are believed to be reliable detections but have greater than average uncertainty in quantification. The data in the NAWQA database are amended with an "E" qualifier to indicate the variability found in the analysis. This suggests that the reported values may not represent the maximum concentrations that exist.

Carbaryl (along with diazinon) was one of the two most widely detected insecticides. Out of 5220 surface water samples analyzed 1082, or about 21 percent, were reported as having detections greater than the MDL. The maximum reported concentration was 5.5 µg/ L. For samples 35 with positive detections the mean concentration was 0.11 : g/ L, with a standard deviation of 0.43 : g/ L. A significant portion of the total carbaryl applied was transported to streams. In areas with high agricultural use the load measured in surface waters was relatively consistent across the country at about 0.1 percent of the amount used in the basins (Larson et al., 1999) http:// water. wr. usgs. gov/ pnsp/ rep/ wrir984222/ load. html. The estimated carbaryl use on in agricultural applications is about 2.5 million pounds suggesting that 2,500 pounds are delivered to the nations streams draining agricultural areas.

Streams draining urban areas showed more frequent detections and higher concentrations than streams draining agricultural or mixed land use areas. For example Kimbrough and Litke (1996) reported that, in the South Platte River Basin Study Unit, between April and December of 1993, carbaryl was detected in 14 urban drainage samples and 6 agricultural drainage samples. Carbaryl had the highest concentration of the four insecticides analyzed with a maximum concentration of 2.5 : g/ L in the urban basin and 1.5 : g/ L in the agricultural basin (http:// webserver. cr. usgs. gov/ nawqa/ splt/ meetings/ KIMB1. html). In the South Central Texas Study Unit carbaryl was detected in 12% of streams draining agricultural areas and 52 % draining urban areas (Bush et al., 2000) http:// water. usgs. gov/ pubs/ circ/ circ1212/.

Registrant Monitoring Study Aventis Crop Science initiated in February 1999 a surface water monitoring study of carbaryl residues in surface water in areas believed to have high agricultural and residential use, based predominantly on county level sales data. A total of 20 sites are monitored, with "medium sized watersheds" targeted: 16 sites in agricultural areas and 4 in areas draining suburban areas. Samples of raw water were collected at municipal water treatment facilities. When raw water analyses detected carbaryl, stored finished water samples (collected at the same time) were analyzed. Samples were collected weekly during periods suspected of being "high risk" and monthly the rest of the year in agricultural areas. Suburban sites were sampled weekly. The study was originally envisioned to last for one year, but was extended for an additional year in February, 2000 (amendment 7), and for a third year in February, 2001 (amendment 9). Carbaryl was analyzed by HPLC/ MS/ MS with a limit of detection of 0.002 ppb (2 ppt) and a limit of quantitation (LOQ) of 0.030 ppb (30 ppt).

OPP has received two interim reports of monitoring from this study. The first report (MRID 45116201) has been fully reviewed and results are described below. Very recently a second report was received by OPP/ EFED. Results from this latest report (MRID 45394101) have not been reviewed in depth, but are similar to results from year one.

Carbaryl was widely detected at surface water sites monitored in this study. Samples containing carbaryl were detected in raw drinking water samples collected at all four suburban monitoring locations, and at about three quarters of the agricultural monitoring locations (13 of 16 sites). Carbaryl was not detected as frequently in finished drinking water samples when they were analyzed; however, only a small subset of finished water samples were actually analyzed. This represents a significant flaw in the study design and limited its usefulness for evaluating the effects 36 of treatment. Differences in concentrations between raw and finished drinking water are likely attributed more to changes in the concentration of source water than to effects of treatment. Most carbaryl detections in this study were at low levels, below the LOQ of 0.03 ppb. Carbaryl contamination measured in this monitoring study appears to be transient, and therefore it is unlikely that any but the most intensive field sampling would ever detect the actual peak concentration that occurs at a site. The interim study reports have not adequately addressed why concentrations found in this study, which claims to target high carbaryl use areas, are substantially lower than those measured in the untargeted USGS NAWQA studies. That, and the limited number of sites sampled, limit the usefulness of this study.

Summary of year one monitoring In raw water samples from suburban sites detectable residues in raw water ranged from 0.002 to 0.023 ppb. 11 out of 40 raw water samples from Sweetwater Creek, the source of water for the East Port facility in Douglas, GA had detectable levels ranging from 0.002 to 0.018 ppb. One out of 46 samples from Joe Pool Lake, Ellis Texas had a detection at 0.014 ppb. Jorden Lake in Cary, NC had 2 detections out of 44 samples (0.004 and 0.003 ppb). 11 out of 40 samples from the Cahaba River in Birmingham AL had detections ranging from 0.002 to 0.023 ppb. Finished water sampled from suburban areas were all below the detection limit.

In samples from agricultural sites 9 out of 15 water sources had some detectable level of carbaryl. The detections were generally at low levels, with one of about 0.16 ppb and one of 0.031. The rest were below the level of quantitation (< 0.030 ppb). Samples from finished water were generally lower than raw water, though it appears that raw and finished water sampling did not sample the same mass of water. Therefore, the data can not be used to evaluate the effectiveness of water treatment on carbaryl. Because the samples were collected at the same time, the water exiting the treatment plant was temporally different than the water entering and represent different, independent, parcels of water. In several cases finished water had higher concentrations than raw water, and finished water had detectable carbaryl when the raw did not. The highest concentration measured was in finished water (0.18 ppb). Raw water sampled at the same time had much lower concentration (0.010).

Non targeted monitoring, such as the NAWQA program, has shown that much higher concentrations occur indicating that this study, while useful, can not be used to describe the overall distribution of concentrations that occur throughout the entire use area. This study does not provide sufficient information to allow estimation of actual peak and mean concentrations that actually occur in all use areas. The highest concentration values measured in this study are close to the average values seen in other, non targeted, studies.

Only limited information was submitted on sampling site selection and how the sites relate to the overall distribution of use areas. Home and garden sites were selected downstream of urban/ suburban areas that were believed to have high use based on county scale sales data. 37 Agricultural sites were selected based on county scale sales data, and are believed to be in "major use counties."

This study is still ongoing and only interim study results have been submitted. Additional information is needed to evaluate the study results. Additionally, an analysis of how the selected sites relate to the nationwide distribution of carbaryl use areas is required. This should include an explanation of why this study did not observe concentrations as high as those found in other, nontargeted studies, and how the results of this study can be related to concentrations that occur throughout the country. Based on the interim data submitted it appears that this study measured concentrations similar to those observed in non targeted studies but did not capture high end or peak values. Until additional information is submitted it is not possible to use these interim results for more then to reinforce the inferences drawn from non targeted study data.

Sacramento San Joaquin River Delta As part of a two year study into the cause of declines in aquatic insects in California's Sacramento San Joaquin Delta, toxicity of surface water was measured using ceriodaphnia. When toxicity was found, toxic identification evaluation was done to determine the causative agent. Carbaryl was found to be the primary toxicant at one of 20 sites sampled in 1995, with concentration of 7.0 : g/ L. The toxicity seemed to persist for several days (Werner, et al., 2000).

STORET The EPA STORET database ( was queried on May 12, 1999 for reports of measurements of carbaryl in surface water. The database contained 8048 records indicating that analysis was done for carbaryl. Out of these 432 reported concentrations above the detection limits. The maximum value reported was 5.5 µg/ L. Of the reported detections 18 were above 1 ppb. The data is the STORET database is used to give a general indication of the occurrence pattern only. Lack of QA/ QC and analytical methodology limitations limit the usefulness of the STORET data. However, reported detections of carbaryl suggest that the compound is infrequently detected in surface water and at low levels.

6.0 Hazard and Risk Assessment for Aquatic Organisms Hazard Assessment for Aquatic Organisms Freshwater Fish On an acute basis, technical carbaryl is moderately to highly toxic to freshwater fish and to fish that spend a portion of their life cycle in fresh water, such as the Atlantic salmon (LC50 = 0.25 20 ppm). LC50 values for the typical end use products range from 1.4 to 290 ppm, falling in the moderately to practically nontoxic categories. Calculation of acute and chronic risk quotients for freshwater fish are based on an Atlantic salmon LC50 of 250 ppb and a fathead minnow NOAEC of 210 ppb, respectively. 38 Amphibians According to an available supplemental study with a 50% carbaryl formulation, the LD50 for the bullfrog (Rana catesbeiana) is greater than 4,000 mg/ kg, or practically nontoxic (MRID 00160000). A single acute exposure of plains leopard frog tadpoles (Rana blairi) to carbaryl concentrations in the 3.5  7.2 mg/ L range led to a 90% reduction in swimming activity, including sprint speed and sprint distance, activity ceasing completely at 7.2 mg/ L (Bridges 1997). This reduction in activity and swimming performance may result in increased predation rates and, because activity is closely associated with feeding, may result in slowed growth that could lead to failure to complete metamorphosis. Acute exposure to low carbaryl levels may not only affect immediate survival of tadpoles but also impact critical life history functions.

On a chronic basis, carbaryl has been shown to have the potential to adversely affect amphibians. In a recent study, nearly 18% of southern leopard frog (Rana sphenocephala) tadpoles exposed to carbaryl during development exhibited some type of developmental deformity, including both visceral and limb malformations, compared to a single deformed (< 1%) control tadpole demonstrating that carbaryl exposure can result in amphibian deformities (Bridges, 2000). Although the length of the larval period was the same for all experimental groups, tadpoles exposed throughout the egg stage were smaller than their corresponding controls. Because exposure to nonpersistent chemicals may last for only a short period of time, it is important to examine the long term effects that short term exposure has on larval amphibians and the existence of any sensitive life stage. Any delay in metamorphosis or decrease in size at metamorphosis can impact demographic processes of the population, potentially leading to declines or local extinction.

Freshwater Invertebrates Carbaryl is very highly toxic to aquatic invertebrates (1.7  26 ppb) on an acute basis. This compound also has a very strong potential for chronic effects to invertebrates (NOAEC = 3.3 ppb). Field studies that evaluated populations of damselflies (Xanthocnemis zealandica) after exposure to 100 µg/ L carbaryl showed a 90% reduction in emergence success after 10 12 days exposure (Hardersen and Wratten, 1998). Studying natural plankton communities in enclosed mesocosms, Havens (1995) reports a decline in total zooplankton biomass and individuals across the range of carbaryl treatments (0  100 ug/ L). Furthermore, at carbaryl concentrations greater than 20 µg/ L Daphnia was no longer found and that at concentrations above 50 ug/ L all cladocerans were eliminated, resulting in an increase in algal biomass, representing a repartitioning of biomass from zooplankton to phytoplankton. Hanazato (1995) exposed Daphnia ambigua to carbaryl and a kairomone released by the predator Chaoborus (phantom midge) simultaneously. Daphnia developed helmets in response to the kairomone, but not in response to carbaryl at 1 3 µg/ L. However, carbaryl enhanced the development of high helmets and prolonged the maintenance period of the helmets in the presence of the kairomone, suggesting that at low concentrations carbaryl can alter predator prey interactions by inducing helmet formation and vulnerability to predation in Daphnia. In related mesocosms studies, exposure to carbaryl at 1 ppm killed all plankton species, including Chaoborus larvae (Hanazato, 1989). However, this concentration is well above the maximum EECs modeled for carbaryl, and is unlikely that such high levels of this chemical would 39 be found under field conditions. Mora et al. (2000) studying the relationship between toxicokinetics of carbaryl and effects on acetylcholinesterase (ACHase) activity in the snail, Pomaca patula, observed increased enzyme inhibition, along with the bioconcentration of carbaryl, after 72 hours of exposure to sublethal levels (3.2 ug/ g). The transfer of snails to carbaryl free water was followed by rapid monophasic elimination with a half life of 1.0 hour, although ACHase activity levels never returned to control values. The risk assessment for freshwater invertebrates is based on a stonefly LC50 of 1.7 ppb and a water flea NOAEC of 1.5 ppb, respectively.

Estuarine/ Marine Fish Carbaryl is categorized as moderately toxic to estuarine/ marine fish on an acute basis, based on a minnow LC50 of 2.6 ppm. Laboratory exposure to a single dose of carbaryl at 100 ppb can adversely affect schooling behavior in the silverside (Weis and Weis, 1974). Exposure to carbaryl at 10 ppb caused retardation of fin regeneration during the first week of the study in the killifish (Fundulus heteroclitus) (Weis and Weis 1975). Field exposure to a maximum carbaryl water concentration of 1.2 ppm affected burying behavior in caged English sole young (Pozorycki, 1999). The acute risk assessment for estuarine/ marine fish is based on a sheepshead minnow LC50 of 2.6 ppm. At present, the chronic NOAEC for marine/ estuarine fish has not been established, therefore additional chronic toxicity studies are required. Guideline 72 4( a) is not fulfilled.

Estuarine/ Marine Invertebrates Technical carbaryl is categorized as very highly toxic to estuarine/ marine shrimp species and moderately toxic to oysters on an acute basis. The mysid LC50 falls in the 5.7  9.6 ppb range and the oyster LC50 is 2.7 ppm. Typical end use carbaryl products are considered very highly toxic to mysids and slightly toxic to oysters. Carbaryl applied to oyster beds in Washington State tidelands at 7.5  8 lb ai/ acre to control ghost and mud shrimp has been shown to be lethal to many nontarget invertebrate species. The acute risk assessment for estuarine/ marine invertebrates is based on a mysid LC50 of 5.7 ppb. There is insufficient data to assess the chronic risk for estuarine/ marine invertebrates. Additional chronic toxicity studies are required. Guideline 72 4( b) is not fulfilled. 40 Aquatic Plants Data based on a single available core toxicity study with the green alga Pseudokirchneria subcapitata (formerly Selenastrum capricornutum) indicates that the LC50 and NOAEC are, respectively, 1.1 ppm and 0.37 ppm . Toxicity testing for the following four aquatic plants is required to support carbaryl's registered forestry uses; duckweed (Lemna gibba), marine diatom (Skeletonema costatum), freshwater blue green algae (Anabaena flos aquae), and a freshwater diatom. Guideline 122 2 is not fulfilled.

1 Naphthol 1 naphthol, the major metabolite of carbaryl degradation by abiotic and microbially mediated processes is moderately to highly toxic to aquatic organisms on an acute basis. LC50 values range from 0.75 to 1.6 ppm for freshwater fish, from 1.2 to 1.8 ppm for estuarine/ marine fish, from 0.70 to 0.73 ppm for freshwater invertebrates, and from 0.21 to 2.5 ppm for estuarine/ marine invertebrates.

Risk Assessment for Aquatic Organisms A detailed analyses of risk quotients (RQs) in relation to their corresponding levels of concern (LOCs) is presented in Appendix B. A summary of the acute and chronic LOC exceedances for aquatic organisms, based on maximum label rates, is presented in Tables 7 and 8.

Freshwater Fish Carbaryl is highly to slightly toxic to freshwater fish (LC50 = 0.25  20 ppm) on an acute basis. The acute risk LOC (0.5) for freshwater fish is exceeded for one of five use scenarios modeled (citrus), at maximum label (RQ: 1.10), "average" (RQ: 0.58), and maximum reported (RQ: 0.93) use rates, and not exceeded for the other four scenarios (sweet corn, field corn, apples, sugar beets). The chronic risk LOC is not exceeded for any of the five use scenarios modeled (Table 7). These data suggest that carbaryl uses may present a risk to freshwater fish only under situations that combine high application rates and runoff into water bodies, such as ponds or lagoons, where the chemical may reach toxic levels.

Sublethal effects have been documented in the literature showing that in fish the inhibition of acetycholinesterase (AChE) can effect thyroid and gonadal dysfunction in the freshwater murrell, Channa punctatus, resulting in ACh accumulation. At the 0.21 ppm concentration level carbaryl was found to reduce pituitary and serum gonadotropin levels accompanied by inhibition of hypothalamic gonadotropin releasing hormone (GnRH) (Bhattacharya, 1993). These test concentration are at the upper end of the water EECs modeled for carbaryl (citrus scenario). 41 Freshwater Aquatic Invertebrates Acute and chronic risk LOCs are exceeded for freshwater invertebrates for all five carbaryl use aquatic scenarios modeled using maximum label use rates (acute RQs = 5.06  161.18, chronic RQs = 3.27  91.33), maximum reported rates (acute RQs = 3.30  136.47, chronic RQs = 2.00 74.67 and "average" rates (acute RQs = 2.65  85.29, chronic RQs = 1.67  44.67), indicating that most carbaryl uses are likely to pose acute and chronic risks to freshwater invertebrates, especially to arthropods. Although carbamates and OP's breakdown rapidly in the environment, studies pertaining to agricultural regions where these insecticides are applied for extended periods of the year have shown that nontarget aquatic invertebrates may be exposed to high levels of ChE inhibiting compounds for a period of up to several months (Gruber and Munn, 1998). In general, due to its rapid metabolism and rapid degradation, carbaryl should not pose a significant bioaccumulation.

Table 7. Summary of acute and chronic risk LOC exceedances, based on maximum label application rates, for freshwater organisms 1 Organism Use site Scenarios Risk Quotients Equal or Exceed Level of Concern for:

Acute Risk (RQs) Acute Restricted Use Acute Endangered Species Chronic Risk Fish Sweet Corn NO YES YES NO Field Corn NO YES YES NO Apples NO NO NO NO Sugar Beets NO NO YES NO Citrus YES (1.1) YES YES NO Aquatic Invertebrates Sweet Corn YES (27.1) YES YES YES (17.3)

Field Corn YES (16.5) YES YES YES (10.7)

Apples YES (5. 1) YES YES YES (3. 3)

Sugar Beets YES (11.2) YES YES YES (7.3)

Citrus YES (161.2) YES YES YES (91.3) 1 Levels of concern (LOCs) for aquatic organisms Acute Risk 0.5 Acute Restricted Use 0. 1 Acute Endangered species 0.05 Chronic Risk 1 Estuarine/ Marine Fish Carbaryl is moderately toxic to estuarine/ marine fish (LC50 = 2.6 ppm); however, no acute LOCs are exceeded for any of the five use scenarios modeled, at any use rate (Table 8). Thus, most carbaryl uses are unlikely to pose an acute risk to marine/ estuarine fish. Although a NOAEC based on core data has not been established, evidence from the open literature indicates that exposure to 5 Also referred in the literature as Callianassa californiensis.

42 low carbaryl levels may produce adverse physiological and behavioral effects in estuarine/ marine fish. Laboratory exposure of Menidia menidia to a single dose of carbaryl (100 ppb) resulted in the disruption of schooling behavior, as carbaryl exposed groups consistently occupied twice the space of control groups, which was attributed to the accumulation of the carbaryl degradate 1 naphthol (Weis and Weis, 1974). Exposing the killifish (Fundulus heteroclitus) to carbaryl at 10 ppb in the laboratory caused retardation of fin regeneration during the first week of the study (Weis and Weis 1975). According to Pozorycki (1999), field studies with caged juvenile English sole (Pleuronectes vetulus) indicated that brain acetylcholinesterase (AChE) activity decreases following carbaryl application, affecting the ability to bury in sediments. Mean brain AChE inhibition was 26% in fish placed on treated mudflats and 24% in fish placed subtidally, but maximum individual values approached 50%. AChE inhibition at 50 60% was noted as a threshold value below which burying decreased sharply. Maximum carbaryl water concentration measured by HPLC was 1.2 µg/ ml at the cage sites. Sediment concentrations on treated mudflats were as high as 23 µg/ g 24 hrs after application. Chronic toxicity studies with an estuarine/ marine fish species is required.

There is one carbaryl use in particular that represents a potential acute and chronic risk to estuarine/ marine fish. Since 1963, carbaryl has been used to treat two tideland areas of Washington State for the control of two species of burrowing shrimp in commercial oyster beds. The acute risk to fish inhabiting treated mudflats or trapped in shallow pools is extremely high, often resulting in fish kills. Exposure to sublethal carbaryl levels has also been shown to inhibit acetylcholinesterase in fish in subtidal areas adjacent to the treated sites resulting in a significant, although reversible, impairment of burying behavior, thus increasing their exposure to predators. Carbaryl is applied aerially, at the rate of 7.5  8 lb ai/ acre (maximum label rate) over oyster seed beds and bare mudflats on a combined total of 800 acres of tidelands in Willapa Bay and Grays Harbor, Washington, to control burrowing shrimp populations (Neotrypaea 5 californiensis and Upogebia pugettensis). Applications are made when shrimp population densities meet the established action threshold of 10 burrow holes per square meter. On average, oyster beds are treated once every six years (Feldman et al. 2000). Unchecked, these shrimp can adversely affect oyster production by making the substrate unsuitable for oyster culture and by competing with these bivalves for food resources (Hulburt et al. 1989). 43 Table 8. Summary of acute risk LOC exceedances, based on maximum label application rates, for marine/ estuarine organisms 1 Organism Use site Scenarios Risk Quotients Equal or Exceed Level of Concern for:

Acute Risk (RQs) Acute Restricted Use Acute Endangered Species Chronic Risk Fish Sweet Corn NO NO NO No Data Field Corn NO NO NO No Data Apples NO NO NO No Data Sugar Beets NO NO NO No Data Citrus NO YES YES No Data Aquatic Invertebrates Sweet Corn YES (27.1) YES YES No Data Field Corn YES (16.5) YES YES No Data Apples YES (5.1) YES YES No Data Sugar Beets YES (11.2) YES YES No Data Citrus YES (161.2) YES YES No Data 1 Levels of concern (LOCs) for aquatic organisms Acute Risk 0.5 Acute Restricted Use 0. 1 Acute Endangered species 0.05 Chronic Risk 1 In addition to providing a substantial portion of U. S. oyster production, these estuaries are also important nurseries for several valuable fisheries. Estimates of potential fish kills in the treated area range from 15,000 to 96,000. Species killed following carbaryl applications include staghorn sculpin (Leptocottus armatus), saddleback gunnels (Pholis ornata), English and sand sole (Parophrys vetulus and Psettichthys melanostictus), shiner perch (Cymatogaster aggregata), starry flounder (Platichthys stellatus), bay gobies (Lepidogobius lepidus), and three spine sticklebacks (Gasterosteus aculeatus) (Feldman 2001). Furthermore, fish inhabiting subtidal channels or migrating over treated mudflats with the flood tide may exhibit a marked reduction in brain acetylcholinesterase (AChE) activity. Field studies with caged juvenile English sole (Pleuronectes vetulus) indicated that mean brain AChE inhibition was 26% in fish placed on treated mudflats and 24% in fish placed subtidally, maximum individual values approaching 50%. The maximum carbaryl water concentration was 1.2 ppm at the cage sites, while sediment concentrations on treated mudflats were as high as 23 ppm 24 hours following application. In treated mudflats, invertebrates that are a source of food for these fish had carbaryl concentrations as high as 76 ppm. It was estimated that AChE inhibition of up to 50% was possible due to the additive exposure to carbaryl in water and prey items, resulting in temporary impairment of burying behavior and increased exposure to predators (Hulburt et al. 1989). Recovery of burying behavior occurred after removal of the exposure.