# Risks of Oxamyl Use to Federally Threatened California Red-legged Frog ( Rana aurora draytonii )

Pesticide Effects Determination

Environmental Fate and Effects Division Office of Pesticide Programs Washington, D.C. 20460

2/12/2009Primary Authors: Alicia Korol Greg Orrick Kristina Garber

Secondary Reviewers: Marietta Echeverria Anita Pease

Branch Chief, Environmental Risk Assessment Branch 4: Elizabeth Behl

2Table of Contents 1. Executive Summary

.................................................................................................................... 8 2. Problem Fo rmulation

......................................................................................................... ........ 13 2.1. Purpose

................................................................................................................................ 13 2.2. Scope

..................................................................................................................... .............. 15 2.3. Previous Assessments

...................................................................................................... ... 16 2.4. Stressor Source and Distribution

........................................................................................ 16 2.4.1. Environmental Fate Properties

..................................................................................... 16 2.4.2. Mechanism of Action

................................................................................................... 19 2.4.3. Use Characterization

.................................................................................................... 20 2.5. Assessed Species

................................................................................................................. 26 2.5.1. Distribution

............................................................................................................ ...... 26 2.5.2. Reproduction

............................................................................................................ .... 29 2.5.3. Diet ..............................................................................................29 2.6. Designated Critical Habitat

............................................................................................... .. 31 2.7. Action Area

............................................................................................................... .......... 33 2.8. Assessment Endpoints and Measures of Ecological Effect

................................................ 35 2.8.1. Assessment Endpoints for the CRLF

........................................................................... 35 2.8.2. Assessment Endpoints for De signated Critical Habitat

............................................... 36 2.9. Conceptual Model

............................................................................................................... 39 2.9.1. Risk Hypotheses

........................................................................................................... 39 2.9.2. Diagram

........................................................................................................................ 39 2.10. Analysis Plan

............................................................................................................ ........ 42 2.10.1. Measures to Evaluate the Risk Hypothesis and Conceptual Model

.......................... 43 2.10.2. Data Gaps

................................................................................................................... 47 3. Exposure Assessment

................................................................................................................ 47 3.1. Label Application Rates and Intervals

................................................................................ 47 3.2. Aquatic Exposure Assessment

............................................................................................ 49 3.2.1. Modeling Approach

..................................................................................................... 49 3.2.2. Model Inputs

................................................................................................................ 50 3.2.3. Results

.......................................................................................................................... 52 3.2.4. Existing Monitoring Data

............................................................................................ 53 3.3. Terrestrial Animal Exposure Assessment

........................................................................... 54 3.4. Terrestrial Plant Exposure Assessment

............................................................................... 57 4. Effects Assessment

.......................................................................................................... .......... 58 4.1. Toxicity of Oxamyl to Aquatic Organisms

......................................................................... 60 4.1.1. Toxicity to Freshwater Fish

......................................................................................... 61 4.1.2. Toxicity to Freshwater Invertebrates

........................................................................... 61 4.1.3. Toxicity to Aquatic Plants

........................................................................................... 62 4.2. Toxicity of Oxamyl to Terrestrial Organisms

..................................................................... 62 4.2.1. Toxicity to Birds

.......................................................................................................... 64 4.2.2. Toxicity to Mammals

................................................................................................... 65 4.2.3. Toxicity to Terres trial Invertebrates

............................................................................ 65 4.2.4. Toxicity to Terrestrial Plants

....................................................................................... 66 4.3. Incident Database Review

.................................................................................................. 66

35. Risk Characterization

................................................................................................................ 68 5.1. Risk Estimation

................................................................................................................... 68 5.1.1. Exposures in the Aquatic Habitat

................................................................................ 68 5.1.2. Exposures in the Terrestrial Habitat

............................................................................ 71 5.1.3. Primary Constituent Elements of Designated Critical Habitat

.................................... 75 5.2. Risk Description

................................................................................................................. 76 5.2.1. Direct Effects

............................................................................................................... 79 5.2.2. Indirect Effects (via Re ductions in Prey Base)

............................................................ 89 5.2.3. Indirect Effects (via Habitat Effects)

........................................................................... 96 5.2.4. Modification to Designated Critical Habitat

................................................................ 97 5.3. Uncertainties

...................................................................................................................... 99 5.3.1. Exposure Assessment Uncertainties

............................................................................ 99 5.3.2. Effects Assessment Uncertainties

.............................................................................. 104 5.4. Addressing the risk hypotheses

......................................................................................... 106 6. Risk Conclusions

.................................................................................................................... 107 7. References

.................................................................................................. 110

Appendices
Appendix A. Intersection of Oxamyl Use Ar ea and California Red-legged frog Habitat Appendix B. The Risk Quotient Method and Levels of Concern Appendix C. PRZM/EXAMS Input Files and Output File Data Appendix D. Example output from T-REX v.1.3.1 Appendix E. Example output from Terrplant v.1.2.2 Appendix F. List of citations accepted and rejected by ECOTOX criteria Appendix G. Detailed spreadsheet of avai lable ECOTOX open literature for oxamyl Appendix H. Summary of human he alth effects data for oxamyl Appendix I. Example output from analysis of likelihood of individual mortality Appendix J. Example output from T-HERPS v.1.0 Appendix K. Use of fugacity approach to estimate exposures to small mammals consuming earthworms contaminated with oxamyl from treatment sites Appendix L. Degradate summary

Attachments

Attachment 1 : Status and Life Hist ory of California Red-legged Frog Attachment 2 : Baseline Status and Cumulativ e Effects for the California Red-legged Frog

4List of Tables
Table 1. Description of evidence supporting effects determination for oxamyl use in California. Assessment endpoint is surv ival, growth and reproduction of CRLF individuals

.................................................................................................................... ..... 11 Table 2. Summary of effects determination for CRLF critical habitat based on uses of
Table 3. Summary of Chemical Properties and Environmental Fate Parameters of
Table 4. Oxamyl uses involving foliar aapplications. These uses are registered for use in CA and considered part of the FIFRA regul atory action relevant to this endangered
Table 5. Uses of oxamyl involvi ng soil applicatio ns. These uses are registered for use in CA and considered part of the FIFRA regul atory action relevant to this endangered
Table 6. Summary of California Department of Pesticide Registration (CDPR) Pesticide
Table 7. Summary of California Department of Pesticide Registration (CDPR) Pesticide

Table 9. Summary of Assessment Endpoints an d Measures of Ecological Effect for

Table 12. PRZM Scenarios and Input Parameters Describing Oxamyl Uses in California.

Table 15. Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
Table 16. Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Table 17. EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Table 18. TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and SemiTable 23. Pesticides and their associated certai nty classification associ ated with incident oxamyl in California.

........................................................................................................ 12
Oxamyl

.............................................................................................................................. 17

species assessment.

........................................................................................................... 21

species assessment.

........................................................................................................... 22
Use Reporting (PUR) Data from 1999 to 2006 by County

............................................... 24
Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered Oxamyl Uses

.. 25 Table 8. Assessment Endpoints and M easures of Ecological Effects.

............................. 36
Primary Constituent Elements of Designated Critical Habitat.

........................................ 38 Table 10. Oxamyl Uses by Foliar 1 Application Assessed for the CRLF. 2

....................... 48 Table 11. Oxamyl Uses by Soil 1 Application Assessed for the CRLF. 2

........................... 49

............................................................................................................................... ............ 51 Table 13. PRZM and EXAMS Chemical Input Parameters for Oxamyl

.......................... 52 Table 14. Aquatic 1-in-10-year EECs ( μ g/L) for Oxamyl Uses in California

.................. 53
oxamyl with T-REX

.......................................................................................................... 55
Exposures of the CRLF and its Prey to Oxamyl

............................................................... 56

Terrestrial Inverteb rate Prey Items.

.................................................................................. 57
aquatic Areas Exposed to Oxamyl via Runoff and Drift.

................................................. 58 Table 19. Freshwater Toxicity Profile for Oxamyl

........................................................... 60 Table 20. Categories of Acute Toxi city for Aquatic Organisms.

..................................... 61 Table 21. Terrestrial Toxici ty Profile for Oxamyl

............................................................ 63 Table 22. Categories of Acute Toxicity for Avian and Mammalian Studies

.................... 64

#I000799-003

.................................................................................................................... 67 Table 24. Summary of Direct Effect RQs for the Aquatic-phase CRLF.

......................... 69 Table 25. Acute and Chronic RQs for aquatic invertebrates exposed to oxamyl

............. 70

5Table 26. RQs for the terrestrial-phase CRLF based on acute and chronic exposures from foliar applications of oxamyl at maximum use rates. These RQs were generated using TREX

............................................................................................................................ ....... 72 Table 27. RQs for acute exposures to small and large terrestrial insects from foliar
Table 28. RQs for acute and chronic exposures of small mammals consuming short grass

Table 29. RQs for monocots and dicots inhabiting dry and se mi-aquatic areas exposed to
Table 30. Risk Estimation Summary for Oxamyl - Direct and Indirect Effects to CRLF. 77 Table 31. Risk Estimation Summary for Oxamyl – PCEs of Designated Critical Habitat
Table 32. Upper-bound Kenega Nomogram T-HE RPS EECs (mg/kg-bw) for Dose-based
Table 33. Upper-bound Kenega Nomogram T- HERPS EECs (mg/kg-diet) for DietaryTable 34. Dose-based RQs for 1.4g CRLF consuming different food items (calculated

Table 35. Refined Dose-based RQs for 37g CRLF consuming different food items
Table 36. Refined Dose-based RQs for 238g CRLF consuming different food items
Table 37. Refined Acute Dietary-based RQs for CRLF consuming different food items
Table 38. Revised Chronic Dietary-based RQ s for CRLF consuming different food items
Table 39. Acute RQs and corresponding likeliho od of individual eff ects and chronic RQs
Table 40. Acute, dose-based RQ values for small mammals (15 g) exposed to oxamyl through consumption of food items on th e treated field. RQs correspond to single
Table 41. Concentration where LOC is not exceeded for small mammals (15 g) receiving acute, dose-based exposures of oxamyl throughconsumption of contaminated food items
Table 42. Chronic, dose-based RQ values for small mammals (15 g) exposed to oxamyl through consumption of food items on th e treated field. RQs correspond to single
Table 43. Chronic, dietary-based RQ values for small mammals (15 g) exposed to oxamyl through consumption of food items on the treated field. RQs correspond to single

Table 44. Acute dose-based RQs and associat ed likelihood of individual effects to
Table 45. Description of evidence supporting ef fects determination for oxamyl use in
Table 46. Summary of effects determination for CRLF critical habitat based on uses of applications of oxamyl at maximum use rates

.................................................................. 73
to oxamyl from foliar applications at maximum use rates

................................................ 74
oxamyl via spray drift and runoff.

.................................................................................... 75

for the CRLF

..................................................................................................................... 78
Exposures of the CRLF and its Prey to Oxamyl

............................................................... 81
based Exposures of the CRLF and its Prey to Oxamyl

..................................................... 82
using T-HERPS).

.............................................................................................................. 83
(calculated using T-HERPS)

............................................................................................. 83
(calculated using T-HERPS)

............................................................................................. 84
(calculated using T-HERPS)

............................................................................................. 85
(RQs calculated using T-HERPS)

..................................................................................... 88
for aquatic invertebrates exposed to oxamyl.

................................................................... 90

applications of oxamyl at 1 lb a.i./A and 2 lb a.i./A.

........................................................ 93

and distance from edge of treatment field where LOC is not exceeded.

.......................... 94

applications of oxamyl at 1 lb a.i./A and 2 lb a.i./A.

........................................................ 95

applications of oxamyl at 1 lb a.i./A and 2 lb a.i./A.

........................................................ 95
terrestrial-phase frogs (prey) due to oxamyl exposures

.................................................... 96

California.

.................................................................................................................... ... 108
oxamyl in California.

...................................................................................................... 109

6List of Figures
Figure 1. Estimated Annual Oxamyl Usage in the U.S.

................................................... 23 Figure 2. Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for

Figure 5. Conceptual Model for Pesticide e ffects on Aquatic-Phase of the CRLF and its
Figure 6. Conceptual Model for Pesticide E ffects on Terrestrial-Pha se of the CRLF and CRLF

................................................................................................................................. 28 Figure 3. CRLF Reproductive Events by Month

.............................................................. 29 Figure 4. Initial area of concern for oxamyl use in California

.......................................... 34

Critical Habitat

.................................................................................................................. 41

its Critical Habitat

........................................................................................................... .. 42 Figure 7. Chance of individual mortality to terrestrial-phase CRL F when considering dose-based RQs

................................................................................................................. 86 Figure 8. Chance of individual mortality to terrestrial-phase CRLF when considering
Figure 9. Likelihood of individua l mortality to terrestrial invertebrates at different distances from the edge of a fi eld treated with a single aerial application of oxamyl at 1 lb
Figure 10. Likelihood of individual mortality to terrestrial inverteb rates at different acute dietary-base RQs.

.................................................................................................... 87

a.i./A

.................................................................................................................................. 91
distances from the edge of a field treated with a single groundapplication of oxamyl at 2 lb a.i./A

.............................................................................................................................. 92

71. Executive Summary
The purpose of this assessment is to evaluate potential direct and i ndirect effects on the California red-legged frog (Rana aurora draytonii ) (CRLF) arising from FIFRA regulatory actions regarding use of oxamyl on agricultural sites. In addition, this assessment evaluates whether these actions can be expected to resu lt in modification of the species’ designated critical habitat. This assessment was completed in accordance with the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) Endangered Species Consultation Handbook (USFWS/NMFS, 1998) and procedures outlined in the Agency’s Overview Document (U.S. EPA, 2004).
The CRLF was listed as a threatened species by USFWS in 1996. The species is endemic to California and Baja California (Mexico) and inhabits both co astal and interior mountain ranges. A total of 243 streams or drainages are believed to be currently occupied by the species, with the greatestnumbers in Monterey, San Luis Obispo, and Santa Barbara counties (USFWS , 1996) in California.
Oxamyl [( EZ )-N,N-dimethyl-2-methylcarbamoyloxyi mino-2-(methylthio)acetamide; CAS# 23135-22-0; PC Code 103801] is an N-methyl carbamate. The mode of action of these pesticides is inhibition of the enzyme acetylcholinesterase. Oxamyl is currently registered as a restricted use plant growth regulator, acaricide, insecticide, miticide, and nematicide for the control of a broad spectrum of insects, mites, ticks, and nematodes on various field crops, vegetables , fruits, and non-bearing trees. The active ingredient is applied to treatment sites in liquid formul ations by aerial, ground or chemigation application equipment or by soil injection. The following uses of oxamyl are registered in California and, therefore, considered partof the federal actio n evaluated in this assessment: apples, celery, cherries, citrus, clover, cotton, cucumber , eggplant, garlic, melons, onions, peaches, pears, peppers, potatoes, pumpkins, squash, tobacco, and tomatoes. Oxamyl has additional uses that are not registered for use in California ( i.e.
, bananas, carrots, ginger, mint, peanuts, pineap ple, plantains, sweet potatoes, and yams). Because oxamyl is not expected to be applied for these uses within California, which is the action area for oxamyl use that is relevant to the CRLF, these uses are not considered part of the federal action ev aluated in this assessment.
Oxamyl is hydrophilic, highly mobile, and relatively nonvolatile. The compound dissipates in the environment by abiotic a nd microbially-influenced degradation and by leaching, with estimated half-lives on the or der of several hours to several weeks. Because oxamyl is relatively nonvolatile and doe s not bind well to soil, the major routes of off-site transport for the compound are expected to include surface water runoff and spray drift.
Major degradates of oxamyl include oxime [2-hydroxyamino-N,N-dimethyl-2­ (methylthio)acetamide], DMOA [N,N-dim ethyl-oxalamic acid], DMCF [cyanomethanoic acid dimethylamide ], DMEA [N,N -dimethyl-oxalamide], and carbon dioxide. Similar to oxamyl parent, oxime is highly mobile; DMOA, DMCF, and DMEA are expected to be highly mobile as well. Furthermore, oxime and DMOA are more

8persistent than oxamyl in certain conditions. Degradates of oxamyl are not considered to be of toxicological concern, based on limited mammalian toxic ity data considered in the Reregistration Eligibility Decision (U.S. EPA 2000). Therefore, exposure to degradates of oxamyl was not considered in this assessment.
Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF, its prey and its habitats to oxamyl are assessed separately for the two habitats. Tier-II aquatic exposure models are used to estimate high-e nd exposures of oxamyl in aquatic habitats resulting from runoff and spray drift from di fferent uses. Peak model-estimated aquatic exposure estimates resulting from different oxamyl uses range from 3.2 to 45 μg/L.
To estimate oxamyl exposures to the terrestrial-phase CRLF, and its potential prey (insects, mice and terrestrial-phase frogs), the T-REX model is used. The T-HERPS model is used to allow for further char acterization of amphibi an-specific dietary exposures used to represent oxamyl exposures to terrestrial-phas e CRLFs. T-REX and THERPS are used for oxamyl uses involving ap plications to foliar surfaces only, not uses involving applications to so il. Exposures of small mammals consuming earthworms contaminated with oxamyl applied directly to the soil are characterized using a fugacitybased approach. AgDRIFT is used to estimate deposition of oxamyl on terrestrial habitats from spray drift. The TerrPlant model is usedto estimate oxamyl exposures to terrestrialphase CRLF habitat.
The effects determination assessment endpoints for the CRLF include direct toxic effects on the survival, reproduction, and growth of th e CRLF itself. Direct effects to the CRLF in the aquatic habitat are based on toxicity information for freshwater fish, which are generally used as a surrogate for aquatic-pha se amphibians. The acu te toxicity endpoint for the aquatic-phase CRLF is a 96-h LC 50 of 4.2 mg a.i./L. The chronic toxicity endpoint for the aquatic-phase CRLF is a NOAEC of 0.77 mg a.i./L, with a LOAEC of 1.5 mg a.i./L based on embryo hatching and larv al swim-up. In the terrestrial habitat, direct effects are based on toxicity informati on for birds, which are used as a surrogate for terrestrial-phase amphibians. The acute and sub-acute endpoints for the terrestrialphase CRLF are LD 50 = 3.16 mg/kg-bw and LC 50 = 340 mg/kg-diet, respectively. The chronic endpoint for the terrestrial-phase CRLF is a NOAEC of 10 mg/kg-diet, which is based on a LOAEC of 50 mg/kg-diet, where e ffects to egg production and fertility were observed (in mallard ducks).
Given that the CRLF’s prey items and designated critical habitat requirements in the aquatic habitat are dependant on the availabil ity of freshwater aquatic invertebrates and aquatic plants, toxicity information for thes e taxonomic groups is also discussed. The toxicity endpoint for algae, representing pr ey of tadpole-stage CRLF is 0.12 mg a.i./L (120-h EC 50 ). The acute and chronic endpoints fo r aquatic invertebrates are 0.018 mg a.i./L (48-h EC 50 ) and 0.012 mg a.i./L (NOAEC derived from an acute-to-chronic ratio), respectively. The endpoints for aquati c plants are 0.12 mg a.i./L (120-h EC 50 ) and 30 mg a.i./L (14-d EC 50 ) for non-vascular and vasc ular plants, respectively.

9In the terrestrial habitat, indirect effect s due to depletion of prey are assessed by considering effects to terrestrial insects, small terrestrial mammals, and frogs. For terrestrial insects, the LD 50 is 0.31 μ g/bee. For terrestrial mammals, the acute and chronic endpoints ar e a 2.5 mg/kg-bw LD 50 and a 25 mg/kg-diet NOAEC, with a LOAEC of 75 mg/kg-diet, based on decreased food cons umption and altered body weight in first generation rats. The endpoints used to repres ent acute, sub-acute and chronic effects to the terrestrial-phase CRLF are also used to represent effects to terrestrial-phase frogs serving as prey to the CRLF ( e.g. , Pacific tree frogs). Indirect effects due to modification of the terrestrial habitat are characterized by available data for terrestrial monocots and dicots. The endpoint for terrestrial plants is an EC 25 > 2.1 lbs a.i./A.
Risk quotients (RQs) are derived as quantitative estimates of potential high-end risk. Acute and chronic RQs are compared to the Agency’s levels of concern (LOCs) to identify instances where oxamyl use within the action area has the potential to adversely affect the CRLF and its designated critical habi tat via direct toxicity or indirectly based on direct effects to its food supply ( i.e. , freshwater invertebrate s, algae, fish, frogs, terrestrial invertebrates, and mammals) or habitat ( i.e. , aquatic plants and terrestrial upland and riparian vegetation). When RQs fo r each particular type of effect are below LOCs, the pesticide is determined to have “no effect” on the CRLF. Where RQs exceed LOCs, a potential to cause adverse effects is identified, leading to a conclusion of “may affect.” If a determination is made that oxamyl use within the action area “may affect” the CRLF and its designated critical habitat, a dditional information is considered to refine the potential for exposure and effects, and th e best available information is used to distinguish those actions that “may affect, but are not likely to adversely affect” (NLAA) from those actions that are “likely to adve rsely affect” (LAA) the CRLF and its critical habitat.

Based on the best available information, the Agency makes a May Affect, and Likely to Adversely Affect (LAA) determination fo r the CRLF from the use of oxamyl. Additionally, the Agency has determined that there is the potential for modification of CRLF designated critical habitat from the us e of the chemical. Summaries of the risk conclusions and effects determinations for th e CRLF and its critical habitat are presented in Table 1 and in Table 2, respectively. These conclusi ons are based on potential effects of oxamyl to the terrestrial-phase CRLF and its prey, including terrestrial insects, small mammals and terrestrial-phase frogs. Furthe r information on the results of the effects determination is included as part of the Ri sk Description in Section 5.2. Given the LAA determination for the CRLF and potential modifi cation of designated cr itical habitat, a description of the baseline status and cumu lative effects for the CRLF is provided in Attachment 2

.

10Table 1. Description of evidence supporting effe cts determination for oxamyl use in California. Assessment endpoint is survival, growth and reproduction of CRLF individuals. Effects Habitat Basis for LAA Determination Direct Aquatic Direct effects to aquatic-phase CRLF resulting from acute and chronic exposures of oxamyl are not expected. - RQs for acute and chronic exposures resulting from all uses of oxamyl are below the levels of concern. Direct Terrestrial Oxamyl has the potential to directly affect the terrestrial-phase CRLF. -Acute and chronic RQs for all uses of oxamyl ex ceed the Agency’s LOCs for the terrestrial-phase CRLF.

- The likelihoods of individual mortality range from 0.00034% to 100% for terrestrial-phase CRLF on a field treated with uses of oxamyl that ha ve LOC exceedances (relevant to California). - Comparison of the LOAEC directly to chronic dietary-based EECs for CRLF consuming small insects and small herbivore mammals indicate that EECs for all uses are suffici ent to exceed the concentration where reproductive effects were observed in the laboratory. Indirect Aquatic Indirect effects to the CRLF through effects to its prey in the aquatic habitat are discountable. - prey - RQs representing exposures to non-vascular aquatic plants (which serve as prey to tadpole stage CRLF) are below LOCs for all uses of oxamyl. - RQs representing acute and chronic exposures to fish (which serve as prey to adult CRLF) are below LOCs for all uses of oxamyl. - Although some RQs representing acute exposures to aquatic invertebrates are above the LOC, the likelihood of individual effects chance indicates th at all uses of oxamyl ar e expected to result in ≤ 0.34% chance of effects to an individual aquatic invertebrate. Therefore, potential i ndirect effects to the CRLF due to effects of oxamyl to aquatic invertebrates resulting from acute exposures are discountable. - RQs representing chronic exposures to aquatic invertebrates (serving as prey to juvenile and adult CRLF) are below LOCs, with the exception of 2 uses (garlic and celery). EECs for garlic and celery do not reach the NOAEC for less sensitive species of aquatic invertebrates ( i.e.
, Daphnia magna ), suggesting that even though sensitive species of aquatic invertebrates may be affected by chronic exposures of oxamyl, less sensitive species, such as daphnids, may not be affected. Because the CRLF is an opportunistic feeder, the impact of effects to sensitive aquatic invertebrates from chronic exposures on the CRLF is discountable. Indirect Aquatic Indirect effects to the CRLF through modification of its aquatic habitat are not expected. - habitat -RQs representing exposures to non-vascular and vascular aquatic plants are below LOCs. -Estimated exposures of oxamyl to riparian vegetation are above the EC 25 values for monocots and dicots. Indirect Terrestrial Oxamyl has the potential to indirectly affect the terrestrial-phase CRLF through effects to its prey. - prey -RQs representing exposures to terrestrial ins ects are above the LOC for all uses of oxamyl. - The likelihood of individual mortality is >99.9% for a terrestrial invertebrate on a field treated with any use of oxamyl (relevant to California). - >22% chance of mortality to individual small insect s can occur within 950 feet from the edge of a field treated with 1 lb a.i./A oxamyl by aerial methods. -RQs representing acute and chronic exposures to small terrestrial mammals are above LOCs for all uses of oxamyl. - The likelihood of individual mortality is >99.9% for a small mammal consuming short grass on a field treated with any use of oxamyl (relevant to California). -Dose-based and dietary-based EECs are above levels where subacute effects to mammals were observed in chronic toxicity studies. -RQs representing exposures to terrestrial-phase frogs are above the LOC for all uses of oxamyl.

- There is a >10% chance of effects to an individualterrestrial phase frog (serving as prey to CRLF) consuming small insects for all oxamyl uses, and a >10% chance of effects to an individual terrestrial phase frog consuming large insects for a majority of oxamyl uses (relevant to California). -Dose-based and dietary-based EECs are above the levels where subacute effects to birds were observed in chronic toxicity studies. Indirect - habitat Terrestrial Indirect effects to the CRLF through modi fication of its terrestrial habitat are not expected. -Estimated exposures of oxamyl to terrestrial vegetation are above the EC 25 values for monocots and dicots.

11Table 2. Summary of effects determination for CRL F critical habitat based on uses of oxamyl in California. Assessment Endpoint Effects Determination Basis for Determination

Modification of aquatic-phase primary constituent elements Habitat Modification Modification of habitat based on the aquatic-phase PCEs is discountable. - RQs for acute and chronic exposures directly to the CRLF resulting from all uses of oxamyl are below the levels of concern. - Indirect effects to the CRLF through effects to its prey in the aquatic habitat are discountable (see Table 1). -RQs representing exposures to non-vascular and vascular aquatic plants are below LOCs. -Estimated exposures of oxamyl to riparian vegetation are above the EC 25 values for monocots and dicots. Modification of terrestrial-phase primary constituent elements Oxamyl has the potential to modify hab itat based on the terrestrial-phase PCEs. - Oxamyl has the potential to directly affect the terrestrial-phase CRLF (See Table 1). Oxamyl has the potential to indirectly affect the terrestrial-phase CRLF through effects to its prey (see Table 1). -Estimated exposures of oxamyl to terrestrial vegetation are below the EC 25 values for monocots and dicots.

Based on the conclusions of this assessment, a formal consultation with the U. S. Fish and Wildlife Service under Section 7 of the Endangered Specie s Act should be initiated.
When evaluating the significance of this ri sk assessment’s direct /indirect and adverse habitat modification effects determinations , it is important to note that pesticide exposures and predicted risks to the species and its resources ( i.e. , food and habitat) are not expected to be uniform across the action ar ea. In fact, given the assumptions of drift and downstream transport ( i.e. , attenuation with distance) , pesticide exposure and associated risks to the species and its resour ces are expected to decrease with increasing distance away from the treated field or site of application. Evaluation of the implication of this non-uniform distribution of risk to the species would re quire information and assessment techniques that are not currently avai lable. Examples of such information and methodology required for this type of an alysis would include the following:

• Enhanced information on the density and distribution of CRLF life stages within specific recovery units and/or designated critical habitat within the action area. This information would allow for quantitative extrapolation of the present risk assessment’s pred ictions of individual effects to the proportion of the population extant with in geographical areas where those effects are predicted. Furthermore, such population information would allow for a more comprehensive eval uation of the significance of potential resource impairment to individuals of the species.

• Quantitative information on prey base requirements for individual aquaticand terrestrial-phase frogs. Wh ile existing information provides a preliminary picture of the types of food sources util ized by the frog, it does not establish minimal requirements to sustain healthy individuals at varying life stages. Such informa tion could be used to establish biologically relevant thresholds of ef fects on the prey base, and ultimately

12establish geographical limits to those effects. This information could be used together with the density data discussed above to characterize the likelihood of adverse effects to individuals.

• Information on population responses of prey base organisms to the pesticide. Currently, methodologies are limited to predicting exposures and likely levels of direct mortality, growth or reproductive impairment immediately following exposure to the pesticide. The degree to which repeated exposure events and the inherent demographic characteristics of the prey population play into the ex tent to which prey resources may recover is not predictable. An e nhanced understanding of long-term prey responses to pesticide exposure would allow for a more refined determination of the magnitude and duration of resource impairment, and together with the information descri bed above, a more complete prediction of effects to individual frogs and potential modificati on to critical habitat.

2. Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By identifying the important components of the problem, it focuses the assessment on the most relevant life history st ages, habitat components, chemical properties, exposure routes, and endpoints. The structure of th is risk assessment is based on guidance contained in U.S. EPA’s Guidance for Ecol ogical Risk Assessment (U.S. EPA 1998), the Services’ Endangered Species Consul tation Handbook (USFWS/NMFS 1998) and is consistent with procedures and methodology outlined in the Overview Document (U.S. EPA 2004) and reviewed by the U.S. Fish and Wildlife Service and National Marine Fisheries Service (USFWS/NMFS 2004).

2.1. Purpose
The purpose of this endangered species assessme nt is to evaluate potential direct and indirect effects on individuals of the fede rally threatened California red-legged frog (Rana aurora draytonii ) (CRLF) arising from FIFRA regul atory actions regarding use of oxamyl on agricultural crops. In addition, this assessment evaluates whether use on agricultural crops is expected to result in m odification of the species ’ designated critical habitat. This ecological risk assessment has been prepared consiste nt with a settlement agreement in the case Center for Biological Diversity (CBD) vs. EPA et al. (Case No. 02­ 1580-JSW(JL)) settlement entered in Federal District Court for the Northern District of California on October 20, 2006.

In this assessment, direct a nd indirect effects to the CRLF and potential modification to its designated critical habitat are evaluated in accordance w ith the methods described in the Agency’s Overview Document (U.S. EP A 2004). Screening level methods include use of standard models such as PRZM/EXAM S, T-REX, TerrPlant, and AgDRIFT, all of which are described at length in the Over view Document. Additional refinements

13include use of the T-HERPS model to refine estimates of exposure to terrestrial-phase CRLF as well as a fugacity based approachfor estimating oxamyl concentrations in earthworms and resulting exposures to sma ll mammals consuming earthworms. Use of such information is consistent with the methodology described in the Overview Document (U.S. EPA 2004), wh ich specifies that “the a ssessment process may, on a case-by-case basis, incorporat e additional methods, models, and lines of evidence that EPA finds technically appropriate for risk management objectives” (Section V, page 31 of U.S. EPA 2004).

In accordance with the Overview Document, provisions of the ESA, and the Services’ Endangered Species Consultation Handbook, the assessment of effects associated with registrations of oxamyl is based on an action ar ea. The action area is the area directly or indirectly affected by the federal action, as indicated by the exceedance of the Agency’s Levels of Concern (LOCs). It is acknowle dged that the action area for a national-level FIFRA regulatory decision associated with a use of oxamyl may potentially involve numerous areas throughout the United States and its Territories. However, for the purposes of this assessment, attention will be focused on relevant sections of the action area including those geographic areas associat ed with locations of the CRLF and its designated critical habitat within the stat e of California. As part of the “effects determination,” one of the following three conclusions will be reached regarding the potential use of oxamyl in accordance with current labels:

• “No effect”;

• “May affect, but not likely to adversely affect”; or

• “May affect and likely to adversely affect.”
Designated critical habitat identifies specific areas that have the phys ical and biological features, (known as primary constituent elem ents or PCEs) essential to the conservation of the listed species. The PCEs for CRLFs ar e aquatic and upland areas where suitable breeding and non-breeding aquatic habitat is located, interspe rsed with upland foraging and dispersal habitat.

If the results of initial scr eening-level assessment methods show no direct or indirect effects (no LOC exceedances) upon individual CRL Fs or upon the PCEs of the species’ designated critical habitat, a “no effect” de termination is made for use of oxamyl as it relates to this species and its designated critic al habitat. If, however, potential direct or indirect effects to individual CRLFs are anticip ated or effects may impact the PCEs of the CRLF’s designated critical habitat, a preliminary “may affect” determination is made for the FIFRA regulatory action regarding oxamyl.
If a determination is made that use of oxamyl within the action area(s) associated with the CRLF “may affect” this species or its designated critical habitat, additional information is considered to refine the potential for e xposure and for effects to the CRLF and other taxonomic groups upon which these species depend ( e.g., aquatic and terrestrial vertebrates and invertebrates, aquatic plan ts, riparian vegetation, etc.). Additional information, including spatial analysis (to de termine the geographical proximity of CRLF

14habitat and oxamyl use sites) and further eval uation of the potential impact of oxamyl on the PCEs is also used to determine whethe r modification of designated critical habitat may occur. Based on the refined information, the Agency uses the best available information to distinguish those actions that “may affect, but are not likely to adversely affect” from those actions that “may affect and are likely to adversely affect” the CRLF or the PCEs of its designated cr itical habitat. This informati on is presented as part of the Risk Characterization in Sec tion 5 of this document.
The Agency believes that the analysis of di rect and indirect eff ects to listed species provides the basis for an analys is of potential effects on the designated critical habitat. Because oxamyl is expected to directly im pact living organisms within the action area (defined in Section 2.7), critical habitat analysis for oxamyl is limited in a practical sense to those PCEs of critical habitat that are bi ological or that can be reasonably linked to biologically mediated processes ( i.e. , the biological resource re quirements for the listed species associated with the cri tical habitat or impo rtant physical aspects of the habitat that may be reasonably influenced through biological processes). Activities that may modify critical habitat are those that alter the PCEs and appreciably diminish the value of the habitat. Evaluation of actions related to us e of oxamyl that may alter the PCEs of the CRLF’s critical habitat form the basis of the critical habitat impact analysis. Actions that may affect the CRLF’s designated critical habitat have been iden tified by the Services and are discussed further in Section 2.6.

2.2. Scope
The result of the EPA pesticide registration process ( i.e. , the FIFRA regulatory action) is an approved product label. The label is a lega l document that stipulates how and where a given pesticide may be used. Product labels (also known as end-use labels) describe the formulation type ( e.g. , liquid or granular), acceptable methods of application, approved use sites, and any restricti ons on how applications may be conducted. Thus, the use or potential use of oxamyl in accordance with th e approved product labels for California is “the action” relevant to this ecological risk assessment.
Oxamyl is an N-methyl carbamate currently registered for the control of a broad spectrum of insects, mites, ticks, and nemat odes on various field crops, vegetables, fruits, and non-bearing trees. Currentregistrations of oxamyl allow for use nationwide with many use patterns limited to specific states including or excluding California. This ecological risk assessment and effects determin ation addresses currently registered uses of oxamyl in portions of the action area thatare reasonably assume d to be biologically relevant to the CRLF and its de signated critical habitat. Fu rther discussion of the action area for the CRLF and its critical habitat is provided in Section 2.7.
Major degradates of oxamyl include oxime [2-hydroxyamino-N,N-dimethyl-2­ (methylthio)acetamide], DMOA [N,N-dim ethyl-oxalamic acid], DMCF [cyanomethanoic acid dimethylamide ], DMEA [N,N -dimethyl-oxalamide], and carbon dioxide. Similar to oxamyl parent, oxime is highly mobile; DMOA, DMCF, and DMEA are expected to be highly mobile as well. Furthermore, oxime and DMOA are more

15persistent than oxamyl in certain conditions. Degradates of oxamyl are not considered to be of toxicological concern, based on limite d mammalian toxicity data on oxime and DMCF that were considered in the RED (U.S. EPA 2000). Therefore, exposure to degradates of oxamyl was not c onsidered in this assessment.
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of active ingredients, either those mixtur es of multiple active ingredients in product formulations or those in the applicator’s tank. In the case of the product formulations of active ingredients (that is, a registeredproduct containing mo re than one active ingredient), each active ingredient is subj ect to an individual risk assessment for regulatory decision regarding the active ingredient on a particular use site. If effects data are available for a formulated product contai ning more than one active ingredient, they may be used qualitatively or quantitatively in accordance with the Agency’s Overview Document and the Services’ Evaluati on Memorandum (U.S. EPA 2004; USFWS/NMFS 2004). Nevertheless, oxamyl does not have a ny registered products that contain multiple active ingredients. No data were identified in the scientific literature to describe the effects of mixtures containing oxamyl on non-target organisms.

2.3. Previous Assessments
Oxamyl was first registered as an insecticid e in the U.S. in 1974. The Agency issued a Registration Standard for oxamyl in 1987, which was updated in 1991. In 2000, the Agency completed an Interim Reregistration Eligibility Decision (IRED) for oxamyl (U.S EPA 2000), which was finalized in 2007.
Since then, an ecological risk assessment fo r the new use of oxamyl on sugar beets has been conducted (U.S. EPA 2007).

2.4. Stressor Source and Distribution

2.4.1. Environmental Fate Properties
Oxamyl [(EZ)-N,N-dimethyl-2-methylcar bamoyloxyimino-2-(methylthio)acetamide; CAS# 23135-22-0; PC Code 103801] is hydr ophilic, highly mobile, and relatively nonvolatile. The compound dissipates in the environment by chemical and microbiallyinfluenced degradation and by leaching, with es timated half-lives on the order of several hours to several weeks. Table 3 summarizes the physiochemical and environmental fate properties of oxamyl.

16Table 3. Summary of Chemical Properties and Environmental Fate Parameters of Oxamyl. Parameter Value Reference Selected Physical/Chemical Parameters
Molecular mass 219.3 g/mol MRID 40499702 Vapor pressure (25°C) 3.84 x 10 -7 torr MRID 42526101 Water solubility (20°C) 2.82 x 10 5 mg/L MRID 40499702 n-Octanol-water partition coeff. (K OW ) 0.36 MRID 40499702
Persistence Hydrolysis half-life pH 5: >31 d pH 7: 8 d pH 9: 0.125 d MRID 40606516

Aqueous photolysis half-life 14.2 d (pH 5) MRID 40606515; 41058801 Soil photolysis half-life No evidence of degradation ACC.# 147704
Aerobic soil metabolism half-life 11 d (silt loam, pH 6.4, OM 2.8%) 17 d (silt loam, pH 6.4, OM 2.8%) ACC.# 63012

11 d (sandy clay loam, pH 7.7, OM 1.5%) MRID 42820001 2.9 d (silt loam, pH 7.0, OM 0.4%) 4.6 d (silt loam, pH 7.8, OM 2.1%) 112 d (silty clay loam, pH 4.8, OM 4.4%) MRID 45176602

Anaerobic soil metabolism half-life 5.2 d (silt loam, pH 4.6, OM 3.7%) 5.8 d (sandy clay loam, pH 7.7, OM 1.5%) MRID 41346201 MRID 42820001 Aerobic aquatic metabolism half-life (half-life corrected for hydrolysis at pH 7) 3.4 d (6.1 d) (sandy loam, pH 6.6-7.8) 3.5 d (6.3 d) (sandy loam, pH 6.9-8.3) MRID 45045305

Soil Mobility Organic carbon partition coefficient (K OC ) 10-60 L/kg OC (5 soils) 6-10 L/kg OC (3 soils) 2.5-8.7 L/kg OC (6 soils) MRID 46237301 Bilkert and Rao, 1985 Bromilow et al. , 1980 Column leaching (% parent in leachate; % identified residues in leachate) <0.2-83%; 89-100% (6 unaged soils) 21-50%; 37-67% (3 aged soils) ACC.# 141395/ MRID 40606514 Field Dissipation Terrestrial field dissipation half-life Not determined (NY) Not determined (CA) 4 d (DE) 3 d (FL), 4 d (CA), 19 d (WA)

8.6 d (MS) (Oxamyl detected at deepest sample depths of each study.) ACC.# 145302 ACC.# 149231 ACC.# 40494 MRID 41573201; 41963901 MRID 45045304

172.4.1.1. Degradation
Hydrolysis of oxamyl is pH-dependent, as oxamy l degrades rapidly in neutral to alkaline environments (half-life of 8 days and 3 hours at pH 7 and 9, respectiv ely) and persists in acidic conditions (relatively stab le at pH 5). Photolysis ap pears to be significant in acidic, clear, near-surface water (half-life of 14 days at pH 5), but not on soil (relatively stable). The major hydrolysis (pH 7 and 9) and aqueous photolysis transformation product is oxime, which comprised 83-93% of the applied radioactivity by the end of the hydrolysis studies (pH 7 and 9) and up to 75% of the applied by the end of the photolysis study. Although these studies were not conduc ted long enough to track a pattern of decline, they suggest oxime may be morepersistent to abiotic degradation ( i.e.
, hydrolysis and photolysis) than oxamyl.
In aerobic aquatic systems, oxamyl degrades with a half-life of 3.4-3.5 days at pH 6.6­ 8.3. The biodegradation half-lif e corrected for hydrolysis at pH 7 is 6.1-6.3 days ( i.e. , the pH 7 hydrolysis rate constant was subtractedfrom the degradati on rate constants in aerobic aquatic systems in order to yield thes e rate constants for biodegradation alone). The major transformation products are oxime, DMOA, DMCF, DMEA, and carbon dioxide. In one study system, oxime reached 59 % of the applied radi oactivity after 1 day and DMOA totaled 79% of the applied after 30 days. In another study system, DMCF and DMEA were up to 55% and 14% of the a pplied, respectively, after 2 days. Carbon dioxide in these systems to taled 31-75% of the applied.
In aerobic soil, oxamyl degrades with a half life ranging from 2.9 to 112 days (6 soils; pH 4.8-7.8). The wide range in half -lives is likely due to variation in pH, as degradation may reflect hydrolysis as well as microbial me tabolism. The major transformation products are oxime, DMOA, and carbon dioxide. In one aerobic metabolism study, oxime peaked at 24% of the applied radioactivity afte r 10 days, DMOA reached 20% of the applied after 21 days, and carbon dioxide comprised 45% of the applied after 51 days (MRID 42820001). In another study, oxime comprised up to 51% of the applied after 7 days; DMOA was a maximum of 35% of the applied in a separate soil af ter 10 days; in both soils, carbon dioxide tota led 73-76% of the applied at study termination (MRID 45176602).
In anaerobic soil, oxamyl degrades with a half-life of 5 to 6 da ys (2 soils; pH 4.6-7.7). In a 32-day anaerobic study, oxime peaked at 70% at 20 days of flooding, declining to 22% at the end of the study; DMOA peaked at 23% at 32 days (MRID 42820001). In another anaerobic study, oxime only formed a maxi mum of 2% of the applied, while DMOA peaked at 86% of the applie d after 30 days of flooding, rema ining 74% of the applied at study termination (MRID 41346201).
Major degradates of oxamyl include oxime [2-hydroxyamino-N,N-dimethyl-2­ (methylthio)acetamide], DMOA [N,N-dim ethyl-oxalamic acid], DMCF [cyanomethanoic acid dimethylamide ], DMEA [N,N -dimethyl-oxalamide], and carbon dioxide. Similar to oxamyl parent, oxime is highly mobile; DMOA, DMCF, and DMEA are expected to be highly mobile as well. Furthermore, oxime and DMOA are more

18persistent than oxamyl in certain conditions, such as abiotic conditions in the case of oxime.

2.4.1.2. Transport
Oxamyl has little affinity for adsorption on a variety of soils and is mobile to highly mobile according to the FAO so il mobility classification sc heme (U.S. EPA 2006). In a submitted batch equilibrium study (5 soils), average soil-water partition coefficients (K d ) ranged from 0.12 to 0.80 L/kg and organic carbon partitioning coefficients (K OC ) ranged from 10 to 60 L/Kg OC (adsorption to one soil was t oo low to calculate a Freundlich isotherm). Adsorption was correlated to or ganic carbon content, demonstrated by less variability in K OC values compared to that in K dvalues. Batch equilibrium studies in the open literature reported lowe r organic carbon partition coefficients (range of 2.5 to 10 L/Kg OC for 9 soils; Bilkert and Rao, 1985; Bromilow et al. , 1980). Oxime has similar mobility to oxamyl parent, with K dvalues ranging from 0.33 to 0.67 L/kg (5 soils) and K OC values ranging from 18 to 66 L/Kg OC . Soil column leaching studies confirm the mobility of oxamyl. In a study using 2 soils, 83-100% of the unaged parent was collected inthe leachate. In a second study with 4 soils, <0.2-83% of the unaged parent and 89- 95% of unaged residues were collected in the leachate. While aging reduces the mob ility of oxamyl residues, significant amounts were still detected; 67% of 7-day aged re sidues, and 37% of 18-day aged residues, compared to 95% in unaged residues (12- inch long column). Oxime and DMOA were found in both the unaged and aged residue leachate. In an 18-inch long column study, 61-63% of the applied radioactivity of oxamy l residues aged 30 days were recovered in the leachate.
Oxamyl has a relatively low partial vapor pressure (3.8 x 10 -7 torr at 25°C) and is soluble in water up to 2.8 x 10 5 mg/L at 20°C. This indicates that the compound will not readily volatilize from soil or water or precipitate from water. Oxamyl has a low n-octanol-water partition coefficient (K OW= 0.36) and, therefore, is not expected to bioaccumulate.

2.4.1.3. Field Dissipation
In the field, half of the applied oxamyl diss ipated from the surface in less than 3 weeks (DT 50 range of 3 to 19 days) in studies from Florida, California and Washington. When both oxamyl and oxime residues are considered, the combined DT 50 values range from 4 to 39 days. Field dissipation studies show that both oxamyl and oxime leach through the soil, confirming that these residues have a lo w affinity for adsorption and are mobile in soil. Oxamyl residues reached the lowest sampled soil depth within several weeks of application in a variety of crops and sites.

2.4.2. Mechanism of Action
Oxamyl is an N-methyl carbamate insecticide, acaricide, miticide, nematocide, and plant growth regulator. Carbamate toxicity (to target pests) is based on the inhibition of the

19enzyme acetylcholine esterase, which cleaves the neurotransmitter acetylcholine. Inhibition of acetylcholine esterase by carbamate insecticides, such as oxamyl, interferes with proper neurotransmission in cholinergic synapses and neuromuscular junctions.
In rodents and humans, which are non-targ et organisms, N-methyl carbamates cause neurotoxicity via the inhibition of cholineste rase by carbamylation of the serine hydroxyl group located in the active site of th e enzyme, which leads to accumulation of acetylcholine and ultimately c linical signs (U.S. EPA 2007).

2.4.3. Use Characterization
Analysis of labeled use information is the critical first step in evaluating the federal action. The current labels for oxamyl repres ent the FIFRA regulator y action; therefore, labeled use and application rates specified on th e label form the basis of this assessment. The assessment of use information is critical to the development of the action area and selection of appropriate mode ling scenarios and inputs.
Oxamyl is registered for 29 agricultural uses in the United States ; however, not all of these uses are federally labeled for use in California. Section 3 uses of oxamyl that are federally labeled for use in California include: tree fruit (apples, cherries, citrus, peaches, pears), fruits and vegetables (celery, cucumb er, eggplant, garlic, melons, onions, peppers, potatoes, pumpkins, squash and tomatoes), co tton, and tobacco. In addition, one special local need registration exists for use of oxamyl on clover grown for seed in California (SLN # CA-06-0028). Although current labe ls do not exclude the use of oxamyl on tobacco in California, tobacco is not grown in the State. U.S. Department of Agriculture census data confirm that tobacco has not beengrown in California from at least the 1992 report, forward (USDA 2008). It is unlikely th at tobacco agriculture will be initiated in California in the future. Therefore, use of oxamyl on tobacco was not quantitatively evaluated for exposure in this assessment. Th e 18 agricultural uses allowed in California for existing crops are evaluated fo r exposure in this assessment.
Oxamyl has some additional uses that are regi stered in other states , but prohibited (by the federal label) in California ( i.e. , bananas, carrots, ginger, mint, peanuts, pineapple, plantains, sweet potatoes, yams). Because oxa myl is not expected to be applied to these crops within California, which is the action area for oxamyl use that is relevant to the CLRF, these additional uses are not considered part of the federal action evaluated in this assessment.
Applications of oxamyl are made to soil, foliar surfaces of crops and to transplants. Application methods for soil uses include injection, band treatment, incorporation, infurrow, and broadcast. Foliar applications include the use of chemigation, ground and aerial equipment. Target pests of oxamyl in clude nematodes, mites and insects. Single maximum application rates of oxamyl range from 1-4 lb a.i./A, depending upon the specific use and application method. At th is time, there are 2 approved formulated products containing oxamyl that are used inthe United States (re gistrations 352-532 and 352-372). Both products are water soluble liquids. Table 4 and Table 5 present oxamyl

20uses and corresponding maximum application rates and application methods considered in this assessment.

Table 4. Oxamyl uses involving foliar a applications. These uses are registered for use in CA and considered part of the FIFRA regulatory action relevant to this endang ered species assessment.

Use Application Method Maximum Single Application Rate (lb a.i./A) Maximum # Applications per Season Apple (bearing fruit) Ground 2.0 1 Celery Ground and Aerial 1.0 6
Citrus (bearing fruit) Ground and Aerial 1.0 6 Chemigation 2.0 3 Clover (for seed) b Ground and Aerial 1.0 2
Cotton Ground and Aerial 1.0 3 Cucumber Ground, Aerial, Chemigation 1.0 6 Eggplant Ground 1.0 6

Garlic Ground and Chemigation 2.0 2.25 d
Aerial 1.0 4.5
Melons c Ground, Aerial, Chemigation 1.0 6
Onion (dry bulb) Ground and Chemigation 2.0 2.25 d
Aerial 1.0 4.5
Non-bearing fruit e Ground 2.0 4 Aerial 1.0 8 Pepper Ground, Aerial, Chemigation 1.0 6
Potato Ground, Aerial, Chemigation 1.0 8 Pumpkin Ground, Aerial, Chemigation 1.0 6 Squash Ground, Aerial, Chemigation 1.0 6

Tomato Ground and Aerial 1.0 8 Chemigation 2.0 4

a Foliar application includes groun d, aerial, and chemigation. b Use on clover is registered under FIFRA Section 24(c).

c Melons includes cantaloupe, honeydew, and watermelon. d Oxamyl product labels allow for a maximum of 2 applications for use on garlic and onion per season at 2.0 lb a.i./A with one additiona l application of 0.5 lb a.i./A.

e Non-bearing fruit includes apple, cherry, citrus, peach, and pear.

21Table 5. Uses of oxamyl involving soil applications. These uses are registered for use in CA and considered part of the FIFRA regulatory action relevant to this endang ered species assessment. Use Maximum Single Application Rate (lb a.i./A) Maximum # applications per

season Apples (bearing fruit) NA NA Celery 1.0 6 Citrus (bearing fruit) NA NA Clover (for seed) b NA NA
Cotton NA NA Cucumber 4.0 1 d Eggplant NA NA Garlic 2.0 2.25 Melons c 4.0 1 d Onion (dry bulb) 2.0 2.25 Non-bearing fruit e 4.0 1 d Pepper 1.0 6
Potato f 4.0 1 d Pumpkin 4.0 1 d Squash 4.0 1 d

Tomato 0.75-1.25 g 3 NA = not applicable

a Soil applications include injection, incorporation, or in-furrow. b Use on clover is registered under FIFRA Section 24(c).

c Melons includes cantaloupe, honeydew, and watermelon. d This application is intended to be made pr eplant soil; therefore, it is assumed that there is one application per season.

e Non-bearing fruit includes apple, cherry, citrus, peach, and pear uses. f Label allows for a preplant soil application of 4 lb a.i./A.
g For this use, maximum application rates should be as follows: the first application should be 0.75 lb a.i./A, the second should be 1.25 lb a.i./A, and the third should be 1.0 lb a.i./A.

In order to understand the exte nt of the use of oxamyl, nati onal level data are considered. Figure 1 depicts estimated annual oxamyl use in th e continental United States in 2002. As of 2002, approximately 700,000 pounds of oxamy l were applied annually. The highest uses of oxamyl included cotton and potatoes (76% of total use).

22Figure 1. Estimated Annual Oxamyl Usage in the U.S.
(from http://water.usgs.gov/nawqa/pnsp/usag e/maps/show_map.php?year=02&map=m6045 ) [The pesticide use maps available from this site show the average annual pesticide use intensity expressed as average weight (in pounds) of a pesticide applied to each square mile of agricultural land in a county. The area of each map is based on state-level estimates of pesticide use rates for individual crops that were compiled by the CropLife Foundation, Crop Protection Research Institute during based on information collected during 1999 through 2004 and on 2002 Census of Agriculture county crop acreage. The maps do not represent a specific year, but rather show typical use patterns over the five year period 1999 through 2004.]
Data describing documented uses of oxamyl in the state of California are also considered. These data were obtained form the Califor nia’s Department of Pesticide Regulation Pesticide Use Reporting (CDPR PUR) database 1 . According to CDPR PUR data, the greatest quantity of oxamyl wa s applied in Fresno County with a yearly average application of 40,801 lbs a.i./year, followed by Kings County, Kern County and Ventura County with 22,642 lbs a.i./year, 11,738 lbs a.i./year, and 10,914 lbs a.i./year, respectively ( Table 6).

1 The California Department of Pesticide Regulation’s Pesticide Use Reporting database provides a census of pesticide applications in the state. See http://www.cdpr.ca.gov/docs/pur/purmain.htm.

23Table 6. Summary of California Department of Pesticide Registration (CDPR) Pesticide Use Reporting (PUR) Data from 1999 to 2006 by County.

County* Average Annual Application (lbs a.i./year) % of total average annual use in CA

Fresno 40,801 36.4% Kings 22,642 20.2%

Kern 11,738 10.5%

Ventura 10,914 9.7% Monterey 6,393 5.7%

Tulare 3,470 3.1%

Merced 3,264 2.9% Imperial 2,326 2.1%
Riverside 2,202 2.0% San Diego 2,066 1.8%
Santa Barbara 1,389 1.2%
San Benito 1,159 1.0%
* Orange , Santa Clara, San Luis Obispo, Madera, San Joaquin, Modoc, Stanlius, Colusa, Yolo, Santa Cruz, Los Angeles, Sutter, Siskiyou, contra Costa, Glenn, Solano, Yuba, Sacramento, Butte and Tehama Counties have <1000 pounds applied annually, which is <1% of the total average annu al use in the state of California.

According to data from the PUR database, from 1999 to 2006, oxamyl was used in greatest quantity on cotton withan average yearly application of 78,118 lbs a.i./year. Celery, tomatoes (produce), onions (dry), a nd peppers (fruiting) followed with 17,125 lbs a.i./year, 4,890 lbs a.i./year, 2,854 lbs a.i./year, and 2,484 lbs a.i. /year, respectively ( Table 7).

24Table 7. Summary of California Department of Pesticide Registration (CDPR) Pesticide Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered Oxamyl Uses.

Crop Average Annual StateWide Application (lbs a.i./ year) Application Rate (lbs a.i./acre)

Mean Maximum

Cotton 78,118 0.74 8.46 Celery 17,125 0.67 6.81 Tomato, produce 4,890 0.68 7.96 Onion, dry 2,854 0.91 9.37 Pepper, fruiting 2,484 0.69 7.47 Tomato, processing 1,672 0.73 4.98 Cantalope 1,505 0.87 3.93 Melon 1,397 0.88 14.93 Garlic 577 1.34 1.99 Apple 314 0.95 3.88 Eggplant 209 0.73 10.45 Watermelon 194 0.63 5.12
Potato 141 0.65 0.95 Cucumber 139 0.72 2.21 Squash 114 0.61 1.19 Orange 98 0.81 1.98 Squash, summer 77 0.79 1.99 Pumpkin 75 0.72 1.00 Pepper, spice 40 0.72 1.00 Pepper, pimento 19 0.43 0.50 Peach 13 10.16 10.35 Nectarine 7.5 5.04 9.96 Squash, zucchini 4.6 2.07 2.99
Lemon 3.1 0.91 1.00 Tangelo 2.5 0.66 0.66 Onion, green 2.0 0.50 0.50 Tangerine 0.62 0.50 0.50 Squash, winter 0.34 0.55 0.55
A number of maximum application rates for different uses exceeded the label-permitted rate. For example, the maximum rate give n for use on eggplant wa s 10.45 lbs a.i./acre, an exceedance from the maximum label rate by about 1000%. However, a review of the CDPR PUR individual recorded uses for the years 2005 and 2006 demonstrate that these extremely high values are either just rare in cidences of misuse, or perhaps misreported values. For 2005, the averag e application rate was 0.79 lbs a.i./year, the 75 th%ile application rate was 1.00 lbs a.i./year, and the 95 th%ile application rate was 1.00 lbs a.i./year. Similarly in 2006, the average application rate was 0.82 lbs a.i./year, the 75 th %ile was 1.00 lbs a.i./year, and the 95 thpercentile rate was 1.01 lbs a.i./year. These

25values are below or just at the maximum labe l-permitted application rates; thus, the usage data confirm that assessi ng exposure of oxamyl to the CRLF based on maximum label rates is reflective of actual use rates for a majority of use sites ( Table 7).

It should be noted that the uses considered in this risk assessment represent all currently registered uses according to a review of all cu rrent labels. No other uses are relevant to this assessment. Any reported use, such as may be seen in the CDPR PUR database, represent either historic uses that have been cancelled, misreported uses, or misuse. Historical uses, misreported uses, and misuse are not considered part of the federal action and, therefore, are not consid ered in this assessment.

2.5. Assessed Species
The CRLF was federally listed as a threaten ed species by USFWS effective June 24, 1996 (USFWS 1996). It is one of two subspecies of the red-legged frog and is the largest native frog in the western United States (U SFWS 2002). A brief summary of information regarding CRLF distribution, repr oduction, diet, and habitat re quirements is provided in Sections 2.5.1 through 2.5.4, respectively. Further information on the status, distribution, and life history of and specific threats to the CRLF is provided in Attachment 1.

Final critical habitat for the CRLF was designated by USFWS on April 13, 2006 (USFWS 2006; 71 FR 19244-19346). Further information on designated critical habitat for the CRLF is provided in Section 2.6.

2.5.1. Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically inhabited 46 counties in Ca lifornia including the Central Valley and both coastal and interior mountain ranges (USF WS 1996). Its range has b een reduced by about 70%, and the species currently resides in 22 counties in California (USFWS 1996). The species has an elevational range of near sea level to 1,500 meters ( 5,200 feet) (Jennings and Hayes 1994); however, nearly all of the known CRLF populations have been documented below 1,050 meters (3,500 feet) (USFWS 2002).
Populations currently exist along the northern California coast, northern Transverse Ranges (USFWS 2002), foothills of the Sierra Ne vada (5-6 populations), and in southern California south of Santa Barbara (two populat ions) (Fellers 2005a). Relatively larger numbers of CRLFs are located between Mari n and Santa Barbara Counties (Jennings and Hayes 1994). A total of 243 streams or draina ges are believed to be currently occupied by the species, with the greatest numbers in Monterey, San Luis Obispo, and Santa Barbara counties (USFWS 1996). Occupied drai nages or watersheds include all bodies of water that support CRLFs ( i.e. , streams, creeks, tributarie s, associated natural and artificial ponds, and adjacent drainages), and habitats through which CRLFs can move ( i.e. , riparian vegetation, uplands) (USFWS 2002).

26The distribution of CRLFs with in California is addressed inthis assessment using four categories of location including r ecovery units, core areas, desi gnated critical habitat, and known occurrences of the CRLF reported in the California Natural Diversity Database (CNDDB) that are not included within core ar eas and/or designated critical habitat (see Figure 2). Recovery units, core areas, a nd other known occurren ces of the CRLF from the CNDDB are described in further detail in Attachment I, and desi gnated critical habitat is addressed in Section 2.6. Recovery units are large areas defined at the watershed level that have similar conservation needs and mana gement strategies. The recovery unit is primarily an administrative designation, and land area within the recovery unit boundary is not exclusively CRLF habitat. Core areas are smaller areas withinthe recovery units that comprise portions of the species’ hi storic and current range and have been determined by USFWS to be important in th e preservation of the species. Designated critical habitat is generally contained within the core ar eas, although a number of critical habitat units are outside the boundaries of core areas, but within the bound aries of the recovery units. Additional information on CRLF occurrences from the CNDDB is used to cover the current range of the species not included in core areas and/or designated critical habitat, but within the recovery units.

Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in California. The CNDDB serves as a repositor y for historical and cu rrent species location sightings. Information regarding known occurrences of CRLFs outside of the currently occupied core areas and designated critical habitat is considered in defining the current range of the CRLF. See: http://www.dfg.ca.gov/bdb/html/cnddb_info.html for additional information on the CNDDB.

27and Western

o Bay

es and Tehachapi

nsular Ranges Recovery Units 1. Sierra Nevada Foothills and C entral Valley 2. North Coast Range Foothills Sacramento River Valley 3. North Coast and North San Fr ancisco Bayancisco Bay 4. South and East San Francisc 5. Central Coast 6. Diablo Range and Salinas Val ley 7. Northern Transverse Rang Mountains 8. Southern Transverse and Peni

Core Ar eas
1. Feather River Feather River 2. Yuba River- S. Fork Feather River Yuba River- S. Fork Feather River 3. Traverse Creek/ Middle Fork/ American R. Rubicon Traverse Creek/ Middle Fork/ American R. Rubicon 4. Cosumnes River Cosumnes River 5. South Fork Calaveras River* South Fork Calaveras River* 6. Tuolumne River* Tuolumne River* 7. Piney Creek* Piney Creek* 8. Cottonwood Creek Cottonwood Creek 9. Putah Creek – Cache Creek* Putah Creek – Cache Creek* 10. Lake Berryessa Tributaries 10. Lake Berryessa Tributaries 11. Upper Sonoma Creek 11. Upper Sonoma Creek 12. Petaluma Creek – Sonoma Creek 12. Petaluma Creek – Sonoma Creek 13. Pt. Reyes Peninsula 13. Pt. Reyes Peninsula 14. Belvedere Lagoon Belvedere Lagoon 15. Jameson Canyon – Lower Napa River Jameson Canyon – Lower Napa River 16. East San Francisco Bay East San Francisco Bay 17. Santa Clara Valley Santa Clara Valley 18. South San Francisco Bay South San Francisco Bay 19. Watsonville Slough-Elkhorn Slough 19. Watsonville Slough-Elkhorn Slough 20. Carmel River – Santa Lucia 20. Carmel River – Santa Lucia 21. Gablan Range 21. Gablan Range 22. Estero Bay 22. Estero Bay 23. Arroyo Grange River 23. Arroyo Grange River 24. Santa Maria River – Santa Ynez River 24. Santa Maria River – Santa Ynez River 25. Sisquoc River 25. Sisquoc River 26. Ventura River – Santa Clara River 26. Ventura River – Santa Clara River 27. Santa Monica Bay – Venura Coastal Streams 27. Santa Monica Bay – Venura Coastal Streams 28. Estrella River 28. Estrella River 29. San Gabriel Mountain* 29. San Gabriel Mountain* 30. Forks of the Mojave* 30. Forks of the Mojave* 31. Santa Ana Mountain* 31. Santa Ana Mountain* 32. Santa Rosa Plateau 32. Santa Rosa Plateau 33. San Luis Ray* 33. San Luis Ray* 34. Sweetwater* 34. Sweetwater* 35. Laguna Mountain* 35. Laguna Mountain*

* Core areas that were historically occupied by the California red-legged frog are not included in the map * Core areas that were historically occupied by the California red-legged frog are not included in the map Figure 2. Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for CRLF

282.5.2. Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams, marshes, and lagoons (Fellers 2005a). Accord ing to the Recovery Plan (USFWS 2002), CRLFs breed from November through late April. Peaks in spawning activity vary geographically; Fellers (2005b) re ports peak spawning as early as January in parts of coastal central California. Eggs are fertili zed as they are being laid. Egg masses are typically attached to emergent vegetation, such as bulrushes ( Scirpus spp.) and cattails ( Typha spp.) or roots and twigs, and float on or near the surface of the water (Hayes and Miyamoto 1984). Egg masses contain appr oximately 2000 to 6000 eggs ranging in size between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch 10 to 14 days after fertilization (Fellers 2005a) depending on water temperature. Egg predation is reported to be infrequent and most mortality is associated with the larval stage (particularly through predation by fish); however, predation on eggs by newts has also been reported (Rathburn 1998). Tadpoles re quire 11 to 28 weeks to me tamorphose into juveniles (terrestrial-phase), typica lly between May and September (Jennings and Hayes 1994, USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until the following year) (Fellers 2005b, USFWS 200 2). Males reach sexual maturity at 2 years, and females reach sexual maturity at 3 years of age; adults have been reported to live 8 to 10 years (USFWS 2002). Figure 3 depicts CRLF annual reproductive timing.

J F M A M J J A S O N D
Light Blue = Breeding/Egg Masses Green = Tadpoles (except those that over-winter) Orange = Young Juveniles Adults and juveniles can be present all year Figure 3. CRLF Reproductive Events by Month

2.5.3. Diet
Although the diet of CRLF aquatic-phase la rvae (tadpoles) has not been studied specifically, it is assumed that their diet is si milar to that of other frog species, with the aquatic phase feeding exclusiv ely in water and consuming diatoms, algae, and detritus (USFWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar, 1980) via mouthparts designed for effectiv e grazing of periphyton (Wassersug, 1984, Kupferberg et al. ; 1994; Kupferberg, 1997; A ltig and McDiarmid, 1999).
Juvenile and adult CRLFs forage in aquatic a nd terrestrial habitats, and their diet differs greatly from that of larvae. The main food source for juvenile aquatic- and terrestrialphase CRLFs is thought to be aquatic a nd terrestrial invert ebrates found along the shoreline and on the water surface. Hayes a nd Tennant (1985) report, based on a study examining the gut content of 35 juvenile a nd adult CRLFs, that the species feeds on as

29many as 42 different invertebrate taxa , including Arachnida, Amphipoda, Isopoda, Insecta, and Mollusca. The most commonly obs erved prey species were larval alderflies ( Sialis cf. californica ), pillbugs ( Armadilliadrium vulgare ), and water striders ( Gerris sp). The preferred prey species, however, was the sowbug (Hayes and Tennant, 1985). This study suggests that CRLFs forage primarily above water, although the authors note other data reporting that adults also feed under water, are cannibalistic, and consume fish. For larger CRLFs, over 50% of the prey mass may c onsists of vertebrates such as mice, frogs, and fish, although aquatic and terrestrial inve rtebrates were the most numerous food items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at night; for juveniles feeding o ccurs during the day and at ni ght (Hayes and Tennant 1985).

2.5.4. Habitat
CRLFs require aquatic habitat for breeding, but also use other habitat types including riparian and upland areas throughout their lif e cycle. CRLF use of their environment varies; they may complete their entire life cycl e in a particular habitat or they may utilize multiple habitat types. Overall, populations are most likely to exist where multiple breeding areas are embedded within varying habitats used for dispersal (USFWS 2002). Generally, CRLFs utilize habitat with perennial or near-perennial water (Jennings et al. 1997). Dense vegetation close to water, shadin g, and water of moderate depth are habitat features that appear especially impor tant for CRLF (Hayes and Jennings 1988). Breeding sites include streams, deep pools, b ackwaters within streams and creeks, ponds, marshes, sag ponds (land depressions between fault zones that have filled with water), dune ponds, and lagoons. Breeding adults have be en found near deep (0.7 m) still or slow moving water surrounded by dense vegetati on (USFWS 2002); however, the largest number of tadpoles have been found in sha llower pools (0.26 – 0.5 m) (Reis, 1999). Data indicate that CRLFs do not fre quently inhabit vernal pools, as conditions in these habitats generally are not suitable (Hayes and Jennings 1988).
CRLFs also frequently breed in artificial impoundments such as stock ponds, although additional research is needed to identify habitat requirements within artificial ponds (USFWS 2002). Adult CRLFs use dense, sh rubby, or emergent vegetation closely associated with deep-water pools bordered w ith cattails and dense stands of overhanging vegetation ( http://www.fws.gov/endangered/f eatures/rl_frog/rlfrog.html#where ).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability, and life stage. Adults rely on riparian vegetation for resti ng, feeding, and dispersal. The foraging quality of the riparian habitat depends on moisture, composition of the plant community, and presence of pools and backwa ter aquatic areas for breeding. CRLFs can be found living within streams at distances up to 3 km (2 miles) from their breeding site and have been found up to 30 m (100 feet) from water in dense riparian vegetation for up to 77 days (USFWS 2002).
During dry periods, the CRLF is rarely found far from water, although it will sometimes disperse from its breeding hab itat to forage and seek othe r suitable habitat under downed trees or logs, industrial debr is, and agricultural features (UWFWS 2002). According to

30Jennings and Hayes (1994), CRLFs also use sm all mammal burrows and moist leaf litter as habitat. In addition, CRLFs may also use larg e cracks in the bottom of dried ponds as refugia; these cracks may provide moisture for individuals avoidi ng predation and solar exposure (Alvarez 2000).

2.6. Designated Critical Habitat
In a final rule published on April 13, 2006, 34 se parate units of critical habitat were designated for the CRLF by USFWS (USF WS 2006; FR 51 19244-19346). A summary of the 34 critical habitat units relative to USFWS-designated recovery units and core areas (previously discussed in Section 2.5.1) is provided in Attachment I.

‘Critical habitat’ is defined in the ESA as th e geographic area occupi ed by the species at the time of the listing where the physical and biological features necessary for the conservation of the species exis t, and there is a need for special management to protect the listed species. It may also include ar eas outside the occupied area at the time of listing if such areas are ‘essential to the c onservation of the species.’ All designated critical habitat for the CRLF was occupied at the time of listing. Cr itical habitat receives protection under Section 7 of the ESA (Section 7) through prohibition against destruction or modification with regard to actions carri ed out, funded, or authorized by a federal Agency. Section 7 requires consultation on fede ral actions that are likely to result in the destruction or modificati on of critical habitat.

To be included in a critical habitat desi gnation, the habitat must be ‘essential to the conservation of the species.’ Critical hab itat designations identify, to the extent known using the best scientific a nd commercial data available, habitat areas that provide essential life cycle needs of the species or areas that contai n certain primary constituent elements (PCEs) (as defined in 50 CFR 414.12(b )). PCEs include, but are not limited to, space for individual and population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiolo gical requirements; cove r or shelter; sites for breeding, reproduction, rearing (or developmen t) of offspring; a nd habitats that are protected from disturbance or are represen tative of the histor ic geographical and ecological distributions of a species. The de signated critical habitat areas for the CRLF are considered to have the following PCEs that justify critical habitat designation:

• Breeding aquatic habitat;

• Non-breeding aquatic habitat;

• Upland habitat; and

• Dispersal habitat.
Further description of thes e habitat types is provided in Attachment I.
Occupied habitat may be include d in the critical habitat only if essential features within the habitat may require special management or protection. Theref ore, USFWS does not include areas where existing management is su fficient to conserve the species. Critical habitat is designated outside the geographic area presently occupied by the species only

31when a designation limited to its present ra nge would be inadequa te to ensure the conservation of the species. For the CRLF, all designated critical habi tat units contain all four of the PCEs, and were occupied by th e CRLF at the time of FR listing notice in April 2006. The FR notice designating critic al habitat for the CRLF includes a special rule exempting routine ranchi ng activities associated withlivestock ranching from incidental take prohibitions. The purpose of this exemption is to promote the conservation of rangelands, which could be bene ficial to the CRLF, and to reduce the rate of conversion to other land uses that are incompatible withCRLF conservation. Please see Attachment I for a full explanation on this special rule.

USFWS has established modification standard s for designated critical habitat (USFWS 2006). Activities that may destroy or adversel y modify critical habitat are those that alter the PCEs and jeopardize the continued existe nce of the species. Evaluation of actions related to use of oxamyl that may alter the PC Es of the CRLF’s critical habitat form the basis of the critical habitat impact analysis . According to USFWS (2006), activities that may affect critical habitat and therefore resu lt in adverse effects to the CRLF include, but are not limited to the following:

(1) Significant alteration of water chemistry or temperature to levels beyond the tolerances of the CRLF that result in di rect or cumulative adverse effects to individuals and their life-cycles. (2) Alteration of chemical characteristics n ecessary for normal growth and viability of juvenile and adult CRLFs. (3) Significant increase in sediment deposition within the stream channel or pond or disturbance of upland fora ging and dispersal habitat that could result in elimination or reduction of habitat necessary for the growth and reproduction of the CRLF by increasing the sediment deposition to levels that would adversely affect their ability to co mplete their life cycles. (4) Significant alteration of ch annel/pond morphology or geometry that may lead to changes to the hydrologic functioning of the stream or pond and alter the timing, duration, water flows, and levels thatwould degrade or eliminate the CRLF and/or its habitat. Such an effect coul d also lead to increased sedimentation and degradation in water quality to levels that are beyond the CRLF’s tolerances. (5) Elimination of upland foraging and/or aes tivating habitat or dispersal habitat. (6) Introduction, spread, or augmentation of non-native aquatic species in stream segments or ponds used by the CRLF. (7) Alteration or elimination of the CRLF ’s food sources or prey base (also evaluated as indirect effects to the CRLF).
As previously noted in Section 2.1, the Agency believes that the analysis of direct and indirect effects to listed species provides the basis for an analysis of potential effects on the designated critical habitat. Because oxa myl is expected to directly impact living organisms within the action area, critical ha bitat analysis for oxamyl is limited in a practical sense to those PCEs of critical habitat that are biological or that can be reasonably linked to biological ly mediated processes.

322.7. Action Area
For listed species assessment purposes, the action area is considered to be the area affected directly or indirec tly by the federal action and not merely the immediate area involved in the action (50 CFR 402.02). It is recognized that the overall action area for the national registration of oxamyl is likely to encompass considerable portions of the United States based on the large array of agri cultural uses. However, the scope of this assessment limits considerati on of the overall action area to those portions that may be applicable to the protection of the CRLF and its designated critical habitat within the state of California. The Agency’s approach to defining the action area unde r the provisions of the Overview Document (U.S. EPA 2004) cons iders the results of the risk assessment process to establish boundaries for that action area with the understanding that exposures below the Agency’s defined Levels of Concern (LOCs) constitute a no-effect threshold. For the purposes of this assessment, attenti on will be focused on the footprint of the action ( i.e. , the area where pesticide application occurs), plus all areas where offsite transport ( i.e. , spray drift, downstream dilution, et c.) may result in potential exposure within the state of California th at exceeds the Agency’s LOCs.
Deriving the geographical extent of this portion of the action area is based on consideration of the types of effects that oxamyl may be expected to have on the environment, the exposure levels to oxamyl thatare associated with those effects, and the best available information concerning the use of oxamyl and its fate and transport within the state of California. Specific measures of ecological effect for the CRLF that define the action area include any direct and indirect toxic effect to the CRLF and any potential modification of its critical habitat, including reduction in su rvival, growth, and fecundity as well as the full suite of sublethal effects av ailable in the effects lit erature. Therefore, the action area extends to a point where environmental exposures are below any measured lethal or sublethal effect thres hold for any biological entity at the whole organism, organ, tissue, and cel lular level of organization

The definition of action area requires a stepwise approachthat begins with an understanding of the federal action. The federal action is de fined by the currently labeled uses for oxamyl. An analysis of labeled us es and review of avai lable product labels was completed (See use characterization in secti on 2.4.3). For those uses relevant to the CRLF, the analysis indicates that, for oxamyl, only agricultural uses are considered as part of the federal action evaluated in this assessment: apple, celery, cherry, citrus, clover, cotton, cucumber, eggplant, garlic, melons (cantaloupe, honeydew, and watermelon), onion, peach, pear, pepper, potato, pumpkin, squash, and tomato.
Following a determination of the assessed uses , an evaluation of the potential “footprint” of oxamyl use patterns ( i.e. , the area where pesticide applic ation occurs) is determined. This “footprint” represents the initial area of concern, based on an analysis of available land cover data for the state of California. The initial area of concern is defined as all land cover types and the stream reaches with in the land cover areas that represent the labeled uses described above. A map represen ting all the land cover types that make up the initial area of concern for oxamyl is presented in Figure 4.

33Figure 4. Initial area of concern for oxamyl use in California.

34Once the initial area of concern is defined, the next step is to compare the extent of that area with the results of the screening level ri sk assessment. In this assessment, transport of oxamyl through runoff and spray drift is c onsidered in deriving quantitative estimates of oxamyl exposure to CRLF, its prey and its habitats. Since this screening level risk assessment defines taxa that are predicted to be exposed through runoff and drift to oxamyl at concentrations above the Agency’s Le vels of Concern (LOC), there is need to expand the action area to include areas that are affected indirectly by this federal action. Because of the lack of a NOAEC in the diet ary-based acute study for the bobwhite quail (MRID: 406065-11), described later in Sec tion 4.2.1, the action area for oxamyl is established as the entire state of California. Additional analysis related to the intersection of the oxamyl action area and CRLF habitat us ed in determining the final action area is described in Appendix A

.
2.8. Assessment Endpoints and Me asures of Ecological Effect
Assessment endpoints are defined as “explicit expressions of the ac tual environmental value that is to be protected.” 1 Selection of the assessment endpoints is based on valued entities ( e.g., CRLF, organisms important in the life cycle of the CRLF, and the PCEs of its designated critical habitat), the ecosystems potentially at risk ( e.g., waterbodies, riparian vegetation, and upland and dispersal habitats), the migration pathways of oxamyl ( e.g., runoff, spray drift, etc.), and the rout es by which ecological receptors are exposed to oxamyl (e.g., direct contact, etc.).

2.8.1. Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival, reproduction, and growth of the CRLF, as well as indirect effects, such as reduction of the prey base or modification of its habitat. In addition, potential m odification of critical habitat is assessed by evaluating potential eff ects to PCEs, which are components of the habitat areas that provide essential life cycle needs of the CRLF. Each assessment endpoint requires one or more “measures of ecological effect,” defined as changes in the attributes of an assessment endpoint or cha nges in a surrogate entity or attribute in response to exposure to a pesticide. Specific measures of ecological effect are generally evaluated based on acute and chronic toxicity information from registrant-submitted guideline tests that are performed on a limited number of organisms. Additional ecological effects data from the open literature are also considered. It should be noted that assessment endpoints are limited to dir ect and indirect effects associated with survival, growth, and fecundity, and do not incl ude the full suite of sublethal effects used to define the action area. According th e Overview Document (U.S. EPA 2004), the Agency relies on acute and chronic effects endpoi nts that are either direct measures of impairment of survival, growth, or fec undity or endpoints for which there is a scientifically robust, peer reviewed relationship that ca n quantify the impact of the measured effect endpoint on the assessment endpoi nts of survival, growth, and fecundity.

1 U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.

35A complete discussion of all the toxicity dataavailable for this risk assessment, including resulting measures of ecologica l effect selected for each taxonomic group of concern, is included in Section 4 of this document. A summary of the assessment endpoints and measures of ecological effect selected to characterize po tential assessed direct and indirect CRLF risks associated withexposure to oxamyl is provided in Table 8

.
Table 8. Assessment Endpoints and Measures of Ecological Effects. Assessment Endpoint Measures of Ecological Effects 3 Aquatic-Phase CRLF (Eggs, larvae, juveniles, and adults) a Direct Effects 1. Survival, growth, and reproduction of CRLF 1a. Rainbow trout ( Oncorhynchus mykiss ) LC 50 1b. Rainbow trout ( Oncorhynchus mykiss ) NOEC Indirect Effects and Critical Habitat Effects 2. Survival, growth, and reproduction of CRLF individuals via indirect effects on aquatic prey food supply ( i.e., fish, freshwater invertebrates, nonvascular plants) 2a. Algae (Navicula pelliculosa ) EC 50 2b. Rainbow trout ( Oncorhynchus mykiss ) LC 50 2c. Midge ( Chironomus plumosus) EC 50 2d. Rainbow trout ( Oncorhynchus mykiss ) NOEC 2e. Midge ( Chironomus plumosus) NOEC 3. Survival, growth, and reproduction of CRLF individuals via indirect effects on habitat, cover, food supply, and/or primary productivity ( i.e., aquatic plant community) 3a. Algae (Navicula pelliculosa ) EC 50 3b. Duckweed ( Lemna Gibba) EC 50

4. Survival, growth, and reproduction of CRLF individuals via effects to riparian vegetation 4a. Monocots: Seedling Emergence, Vegetative Vigor EC 25 4b. Dicots: Seedling Emergence, Vegetative Vigor EC 25 Terrestrial-Phase CRLF (Juveniles and adults) Direct Effects 5. Survival, growth, and reproduction of CRLF individuals via direct effects on terrestrial phase adults and juveniles 5a. Northern Bobwhite Quail ( Colinus virginianus ) LC 50 5b. Mallard duck ( Anas platyrhynchos ) NOEAC Indirect Effects and Critical Habitat Effects

6. Survival, growth, and reproduction of CRLF individuals via effects on terrestrial prey ( i.e., terrestrial invertebrates, small mammals , and frogs) 6a. Laboratory rat (Rattus norvegicus ) Female LD 50 and Male LD 50 6b. Laboratory rat ( Rattus norvegicus ) NOAEC 6c. Mallard duck ( Anas platyrhynchos ) LD 50 6d. Honey bee ( Apis mellifera ) LD 50 6e. Northern Bobwhite Quail ( Colinus virginianus ) LC 50 6f. Mallard duck ( Anas platyrhynchos ) NOEAC 7. Survival, growth, and reproduction of CRLF individuals via indirect effects on habitat ( i.e., riparian and upland vegetation) 7a. Monocots: Seedling Emergence, Vegetative Vigor EC 25 7b. Dicots: Seedling Emergence, Vegetative Vigor EC 25

2.8.2. Assessment Endpoints for De signated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related to the use of oxamyl that may alter the PCEs of the CRLF’s critical habitat. PCEs for the CRLF were previously described in Section 2.6. Actions that may modify critical habitat

3 All registrant-submitted and open literature toxicity da ta reviewed for this assessment are included in Appendix A.

36are those that alter the PCEs and jeopardi ze the continued existence of the CRLF. Therefore, these actions are id entified as assessment endpoints. It should be noted that evaluation of PCEs as assessment endpoints is limited to those of a biological nature ( i.e.
, the biological resource requirements for the list ed species associated with the critical habitat) and those for which oxamyl eff ects data are available (see Table 9). Modification to the critical habitat of the CRLF includes, but is not limited to, those listed in Section 2.6.
Measures of such possible effects by labele d use of oxamyl on cri tical habitat of the CRLF are described in section 2.6. Some components of these PCEs are associated with physical abiotic features ( e.g. , presence and/or depth of a water body, or distance between two sites), which are not exp ected to be measurably alte red by use of pesticides. Assessment endpoints used for the analysis of designated critical habitat are based on the modification standard es tablished by USFWS (2006).

37Table 9. Summary of Assessment Endpoints and Measures of Ecological Effect for Primary Constituent Elements of Desi gnated Critical Habitat. Assessment Endpoint Measures of Ecological Effect Aquatic-Phase CRLF PCEs (Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat) Alteration of channel/pond morphology or geometry and/or increase in sediment deposition within the 1a. Algae (Navicula pelliculosa ) EC 50 stream channel or pond: aquatic habitat (including 1b. Duckweed ( Lemna Gibba) EC 50 riparian vegetation) provides for shelter, foraging, 1c. Monocots: Seedling Emergence, Vegetative Vigor EC 50 predator avoidance, and aquatic dispersal for juvenile 1d. Dicots: Seedling Emergence, Vegetative Vigor EC 25 and adult CRLFs. Alteration in water chemistry/quality including 2a. Algae (Navicula pelliculosa ) EC 50 temperature, turbidity, and oxygen content necessary 2b. Duckweed ( Lemna Gibba) EC 50 for normal growth and viability of juvenile and adult 2c. Monocots: Seedling Emergence, Vegetative Vigor EC 25 CRLFs and their food source. 2d. Dicots: Seedling Emergence, Vegetative Vigor EC 25 3a. Rainbow trout ( Oncorhynchus mykiss ) LC 50 Alteration of other chemical characteristics necessary 3b. Midge ( Chironomus plumosus) EC 50 for normal growth and viability of CRLFs and their 3c. Rainbow trout ( Oncorhynchus mykiss ) NOEC food source. 3d. Midge ( Chironomus plumosus) NOEC 3e. Algae (Navicula pelliculosa ) EC 50 Reduction and/or modification of aquatic-based food sources for pre-metamorphs ( e.g., algae) 4. Algae (Navicula pelliculosa ) EC 50 Terrestrial-Phase CRLF PCEs (Upland Habitat and Dispersal Habitat) Elimination and/or disturbance of upland habitat; ability of habitat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or dripline surrounding aquatic and riparian habitat that are comprised of grasslands, woodlands, and/or wetland/riparian plant species that provides the CRLF shelter, forage, and predator avoidance 5a. Monocots: Seedling Emergence, Vegetative Vigor EC 25 5b. Dicots: Seedling Emergence, Vegetative Vigor EC 25 5c. Laboratory rat (Rattus norvegicus ) Female LD 50 and

Male LD 50 5d. Laboratory rat ( Rattus norvegicus ) NOAEC 5e. Mallard duck ( Anas platyrhynchos ) LD 50 5f. Honey bee ( Apis mellifera ) LD 50 5g. Northern Bobwhite Quail ( Colinus virginianus ) LC 50 5h. Mallard duck ( Anas platyrhynchos ) NOEAC Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal habitat within designated units and between occupied locations within 0.7 mi of each other that allow for movement between sites including both natural and altered sites which do not contain barriers to dispersal Reduction and/or modification of food sources for terrestrial phase juveniles and adults Alteration of chemical ch aracteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food source.

a Physico-chemical water quality parameters such as salinity, pH , and hardness are not evaluated because these processes are not biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.

382.9. Conceptual Model

2.9.1. Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects ( i.e., changes in assessment endpoints) and may be based on theory and logic, empirical data, mathematical models, or probability models (U .S. EPA, 1998). For this assessment, the risk is stressor-linked, where the stressor is the release of oxamyl to the environment. The following risk hypotheses are presumedfor this endangered species assessment:
The labeled use of oxamyl w ithin the action area may:

• directly affect the CRLF by causing mortal ity or by adversely a ffecting growth or fecundity;

• indirectly affect the CRLF by reducing or changing the composition of food supply;

• indirectly affect the CRLF or modify designated critical habitat by reducing or changing the composition of the aquatic plant community in the ponds and streams comprising the species’ current rang e and designated critic al habitat, thus affecting primary productivity and/or cover;

• indirectly affect the CRLF or modify designated critical habitat by reducing or changing the composition of the terrestrial plant community ( i.e. , riparian habitat) required to maintain acceptable water qual ity and habitat in the ponds and streams comprising the species’ current range and designated critical habitat;

• modify the designated critical habitat of the CRLF by reducing or changing breeding and non-breeding aqua tic habitat (via modifi cation of water quality parameters, habitat morphology, and/or sedimentation);

• modify the designated critical habitat of the CRLF by reducing the food supply required for normal growth and viabili ty of juvenile and adult CRLFs;

• modify the designated critical habitat of the CRLF by reducing or changing upland habitat within 200 ft of the edge of the riparian vegetation necessary for shelter, foraging, and predator avoidance.

• modify the designated critical habitat of the CRLF by reducing or changing dispersal habitat within designated units and between occupied locations within 0.7 mi of each other that allow for moveme nt between sites including both natural and altered sites which do not contain barriers to dispersal.

• modify the designated critical habi tat of the CRLF by altering chemical characteristics necessary for normal growthand viability of juvenile and adult CRLFs.

2.9.2. Diagram
The conceptual model is a graphic representation of the structure of the risk assessment. It specifies the oxamyl release mechanisms , biological receptor types, and effects endpoints of potential concern. The concep tual models for terre strial and aquatic

39exposures are shown in Figure 5 and in Figure 6, respectively, which include the conceptual models for the aquatic and terrestr ial PCE components of critical habitat.
Based on available fate and transport data for oxamyl (describ ed in Section 2.4.1), potential transport mechanisms of this pe sticide include surface water runoff, ground water leachate, spray drift, and secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or more distant ecosystems. Because oxamyl is relatively nonvolatile and does not bind well to soil, secondary drift is not expected to appreciably occur. Also, because oxamy l degrades in aquatic environments by metabolism and hydrolysis in non-acidic envi ronments, and ground water flow tends to be attenuated relative to surf ace water flow, exfiltrated gr ound water is expected to contribute attenuated amounts of oxamyl to su rface water bodies afte r residues in runoff have largely dissipated. Ther efore, ground water discharge is not expected to contribute greater exposure to surface water bodies than surface water runoff. And, thus, the major routes of exposure for oxamyl are expectedonly to include surface water runoff and spray drift. Exposure routes shown in dashed lines are not quanti tatively considered because the contribution of thos e potential exposure routes to potential risks to the CRLF and modification to designated critical habitat is expected to be appreciably less than that of potential exposure routes shown in solid lines.

40Stresso r

Source

Exposure Media

Receptors

Attribute Oxamyl applied to agriculture use site

Spra ydrift

Surface water/ Sediment Runoff Long range atmospheric

transport

Wet/dry deposition Soil Groundwate r

Uptake/gills Uptake/cell,

Aquatic Animals Invertebrates Vertebrates or integument roots, leaves Uptake/gills or integument

Ingestion Ingestion A quatic Plants Non-vascular Vascula r Riparian plant terrestrial exposure pathways

Fish/aquatic

phase amphibians **Piscivorous mammals and birds
Habitat integrity Change Individual organisms Reduced survival Reduced growth Reduced reproduction Food chain Reduction in algae Reduction in prey Modification of PCEs related to prey availability Reduction in primary productivity Reduced cover Community change Modification of PCEs related to habitat

Figure 5. Conceptual Model for Pesticide effects on Aquatic-Phase of the CRLF and its Critical Habitat.

41Stressor

Source

Receptors

Attribute Oxamyl applied to agriculture use site

Direct application Spray drift

Birds/terrestrialphase amphibians/ reptiles/mammals

Terrestrial

insects

Individual organisms Habitat integrity Terrestrial/riparian plants grasses/forbs, fruit, seeds (trees, shrubs) Runoff

Mammals/ Birds Exposure Media Soil

Ingestion Ingestion

Ingestion Ingestion Dermal uptake/Ingestion Long range atmospheric

transport

Root uptake Wet/dry deposition

Terrestrialphase amphibians

Ingestion

Reduced survival Food chain Change Reduced growth Reduction in prey Reduced reproduction Modification of PCEs related to prey availability Reduction in primary productivity Reduced cover Community change Modification of PCEs related to habitat

Figure 6. Conceptual Model for Pe sticide Effects on Terrestrial-Ph ase of the CRLF and its Critical Habitat.

2.10. Analysis Plan
In order to address the risk hypothesis, the potential for direct and indirect effects to the CRLF, its prey, and its habitat is estimat ed. In the following sections, the use, environmental fate, and ecological effects of oxamyl are characterized and integrated to assess the risks. This is accomplished us ing a risk quotient (ratio of exposure concentration to effects concen tration) approach. Although ri sk is often defined as the likelihood and magnitude of adve rse ecological effects, the ri sk quotient-based approach does not provide a quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as outlined in the Overview Document (U.S. EPA, 2004), the likelihood of effects to individua l organisms from particular uses of oxamyl is estimated using the probit dose-response sl ope and either the level of concern (discussed below) or actual calculated risk quotient value.

422.10.1. Measures to Evaluate the Risk Hypothesis and Conceptual Model

2.10.1.1. Measures of Exposure
The environmental fate properties of oxa myl along with available monitoring data indicate that runoff and spra y drift are the principle potential transport mechanisms of oxamyl to the aquatic and terrestrial habitats of the CRLF. In this assessment, transport of oxamyl through runoff and spray drift is c onsidered in deriving quantitative estimates of oxamyl exposure to CRLF, its prey and its habitats.
Measures of exposure are based on aquatic and terrestrial models that predict estimated environmental concentrations (EECs) of oxamyl using maximum labeled application rates and methods of application. The mode ls used to predict aquatic EECs are the Pesticide Root Zone Model coupled with the Exposure Analysis Model System (PRZM/EXAMS). The model used to predict terrestrial EECs on food items is T-REX. The model used to derive EECs relevant to te rrestrial and wetland plants is TerrPlant. These models are parameterized using relevant reviewed registrant-submitted environmental fate data.
PRZM (v3.12.2, May 2005; Carousel et al. , undated) and EXAMS (v2.98.4.6, April 2005; Burns, 2004) are screening simulation mo dels coupled with the graphical user interface PE (v5.0, Aug 2007) to generate da ily exposures and 1-in-10 year EECs of oxamyl that may occur in surface water bodie s adjacent to application sites receiving oxamyl through runoff and spray drift. PRZM simulates pesticide application, movement and transformation on an agricu ltural field and the resultant pesticide loadings to a receiving water body via runoff, erosion and sp ray drift. EXAMS simulates the fate of the pesticide and resulting con centrations in the water body. The standard scenario used for ecological pesticide assessments assumes application to a 10-hect are agricultural field that drains into an adjacent 1-hect are water body, 2-meters deep (20,000 m 3 volume) with no outlet. PRZM/EXAMS was used to esti mate screening-level exposure of aquatic organisms to oxamyl. The measure of exposur e for aquatic species is the 1-in-10 year return peak or rolling mean concentration. The 1-in-10 year peak is used for estimating acute exposures of direct effects to the CRL F, as well as indirect effects to the CRLF through effects to potential prey items, includ ing: algae, aquatic invertebrates, fish and frogs. The 1-in-10-year 60-day mean is used for assessing chronic exposure to the CRLF and fish and frogs serving as prey items; the 1-in-10-year 21-day mean is used for assessing chronic exposure for a quatic invertebrates, which are also potential prey items.
Exposure estimates for the terrestrial-phase CRLF and terrestria l invertebrates and mammals (serving as potential prey) assumed to be in the target area or in an area exposed to spray drift are derived usi ng the T-REX model (v1.3.1, 12/07/2006; U.S. EPA. 2006 c ). This model incorporates the Kenega nomograph, as modified by Fletcher et al. (1994), which is based on a large set of actual field residue data. The upper limit values from the nomograph represented the 95th percentile of residue values from actual

43field measurements (Hoerger and Kene ga, 1972). For modeling purposes, direct exposures of the CRLF to oxamyl through contaminated food are estimated using the EECs for the small bird (20 g) which consum es small insects. Dietary-based and dosebased exposures of potential prey (small mammals) are a ssessed using the small mammal (15 g) which consumes short grass. The sma ll bird (20g) consuming small insects and the small mammal (15g) consuming short grass ar e used because these categories represent the largest RQs of the size and dietary categories in T-REX that are appropriate surrogates for the CRLF and one of its prey items. Estimated exposures of terrestrial insects to oxamyl are bound by using the diet ary based EECs for small insects and large insects.
Birds are currently used as surrogates for te rrestrial-phase CRLF. However, amphibians are poikilotherms (body temperature varies with environmenta l temperature) while birds are homeotherms (temperature is regulate d, constant, and largely independent of environmental temperatures). Therefore, am phibians tend to have much lower metabolic rates and lower caloric intake requirements than birds or mammals. As a consequence, birds are likely to consume more food than amphibians on a daily dietary intake basis, assuming similar caloric content of the f ood items. Therefore, the use of avian food intake allometric equation as a surrogate to amphibians is likely to result in an overestimation of exposure and risk for reptiles a nd terrestrial-phase amphibians. Therefore, T-REX (v.1.3.1) has been refined to the T- HERPS model (v. 1.0, 5/15/2007; U.S. EPA. 2007 a ), which allows for an estimation of food intake for poikilotherms using the same basic procedure as T-REX to estimate avian food intake.
EECs for terrestrial plants inhabiting dry a nd wetland areas are derived using TerrPlant (version 1.2.2, 12/26/2006; (U.S. EPA. 2006 b ). This model uses estimates of pesticides in runoff and in spray drift to calculate EECs. EECs are based upon solubility, application rate and minimu m incorporation depth.
In order to explore the potential exposures of mammals to oxamyl following applications involving ground application, a simple fugac ity approach was employed to estimate oxamyl concentrations in earthworms and s ubsequent exposures to mammals consuming earthworms.
The spray drift model, AgDRIFT, is used to assess exposures of terrestrial phase CRLF and its prey to oxamyl deposited on terre strial habitats by spray drift.

2.10.1.2. Measures of Effect

Data identified in Section 2.8 are used as measur es of effect for direct and indirect effects to the CRLF. Data were obtained from regi strant submitted studies or from literature studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched in order to provide more ecological effects data and in an attempt to bridge existing data gaps. ECOTOX is a source for locating single chemical toxicity data for aquatic life, terrestrial plants, and wildlife. ECOTOX was created and is maintained by the U.S. EPA,

44Office of Research and Devel opment, and the National Health and Environmental Effects Research Laboratory's Mid- Continent Ecology Division.

The assessment of risk for direct effect s to the terrestrial-phase CRLF makes the assumption that toxicity of oxamyl to birds is similar to or less than the toxicity to the terrestrial-phase CRLF. The same assumption is made for fish and aquatic-phase CRLF. Algae, aquatic invertebrates, fish, and amphi bians represent potential prey of the CRLF in the aquatic habitat. Terrestrial invertebrates, small mammals, and terrestrial-phase amphibians represent potential pr ey of the CRLF in the terrestrial habitat. Aquatic, semiaquatic, and terrestrial plants represent habitat of CRLF.

The acute measures of effect used for animal s in this screening level assessment are the LD 50 , LC 50 and EC 50 . LD stands for "Lethal Dose", and LD 50 is the amount of a material, given all at once, that is estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” and LC 50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. EC stands for “Effective Concentration” and the EC 50 is the concentration of a chemical that is estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic measures of exposure for listed and non-listed animals are the NOAEL/NOAEC an d NOEC. NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested dose of a substance that has been reported to have no harmful (adve rse) effects on test organisms. The NOAEC ( i.e. , “No-Observed-Adverse-Effect -Concentration”) is the highest test concentration at which none of the observed effects were statis tically different from the control. The NOEC is the No-Observed-Effects-Concentra tion. For non-listed plants, only acute exposures are assessed ( i.e. , EC 25 for terrestrial plants and EC 50 for aquatic plants).
The Agency uses the probit dose response rela tionship as a tool for providing additional information on the potential for acute direct effects to individual listed species and aquatic animals that may indirectly affect the listed species of concern (U.S. EPA, 2004). As part of the risk characterization, an inte rpretation of acute RQ for listed species is discussed. This interpretation is presented in terms of the chance of an individual event ( i.e. , mortality or immobilization) should exposur e at the EEC actually occur for a species with sensitivity to oxamyl on par with the acute toxicity endpoint selected for RQ calculation. To accomplish this interpretati on, the Agency uses the slope of the dose response relationship available from the toxicity study used to establish the acute toxicity measures of effect for each taxonomic group that is relevant to this assessment. The individual effects probability associated with the acute RQ is based on the mean estimate of the slope and an assumption of a probit dose response relationshi p. In addition to a single effects probability es timate based on the mean, upper and lower estimates of the effects probability are also pr ovided to account for variance in the slope, if available.
Individual effect probabilitie s are calculated based on an Ex cel spreadsheet tool IECV1.1 (Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental Fate and Effects Division (J une 22, 2004). The model allows for such calculations by entering the mean slope esti mate (and the 95% confidence bounds of that

45estimate) as the slope parameter for the spread sheet. In addition, the acute RQ is entered as the desired threshold.
It is important to note that the measures of effect for direct and indirect effects to the CRLF and its designated critical habitat are as sociated with impacts to survival, growth, and fecundity, and do not include the full suite of sublethal effects used to define the action area. According the Overview Docu ment (U.S. EPA 2004), the Agency relies on effects endpoints that are either direct measures of impairme nt of survival, growth, or fecundity or endpoints for which there is a scientifically robust, peer reviewed relationship that can quantify the impact of the measured effect endpoint on the assessment endpoints of survival, growth, and fecundity.

2.10.1.3. Integration of Exposure and Effects
Risk characterization is the integration of exposure and ecological e ffects characterization to determine the potential ecolo gical risk from agricultural and non-agricultural uses of oxamyl, and the likelihood of direct and indir ect effects to CRLF in aquatic and terrestrial habitats. The exposure and toxi city effects data are integrat ed in order to evaluate the risks of adverse ecological e ffects on non-target species. For the assessment of oxamyl risks, the risk quotient (RQ) method is used to compare exposure and measured toxicity values. EECs are divided by acute and chr onic toxicity values. The resulting RQs are then compared to the Agency’s levels of concern (LOCs) (U.S. EPA, 2004) (see Appendix B).
For this endangered species assessment, listedspecies LOCs are used for comparing RQ values for acute and chronic exposures of oxa myl directly to the CRLF. If estimated exposures directly to the CRLF of oxamyl resu lting from a particular use are sufficient to exceed the listed species LOC, th en the effects determination for that use is “may affect”. When considering indirect effects to the CRLF due to effects to animal prey (aquatic and terrestrial invertebrates, fis h, frogs, and mice), the listed speci es LOCs are also used. If estimated exposures to CRLF prey of oxa myl resulting from a particular use are sufficient to exceed the listed sp ecies LOC, then the effects de termination for that use is a “may affect.” If the RQ being considered also exceeds the non-listed species acute risk LOC, then the effects determination is a LAA. If the acute RQ is between the listed species LOC and the non-listed acute risk sp ecies LOC, then further lines of evidence ( i.e. probability of individual effects, species sensitivity distributions) are considered in distinguishing between a determination of NLAA and a LAA. When considering indirect effects to the CRLF due to effects to algae as dietary items or plants as habitat, the nonlisted species LOC for plants is used b ecause the CRLF does not have an obligate relationship with any particular aquatic and/ or terrestrial plant. If the RQ being considered for a particular use exceeds the non-listed species LOC fo r plants, the effects determination is “may affect”. Further in formation on LOCs is provided in Appendix B.

462.10.2. Data Gaps
Acceptable data regarding the anaerobic aquatic metabolism of oxamyl are not available. These data are relevant to the environmen tal fate of residues in anaerobic aquatic environmental compartments including saturated subsurface soils. However, submitted hydrolysis and anaerobic soil metabolism data indicate that oxamyl will not persist under anaerobic, aquatic environments , especially in neutral to alkaline conditions, due to hydrolysis.

3. Exposure Assessment
Oxamyl is formulated as a water-soluble liquid. Application me thods include aerial, air-blast, and ground foliar broadcasts, chemigation, soil injection, band treatment, row treatment, incorporati on, in-furrow spray or dren ch, and transplant water treatment. Application equipment include s various aircraft, ground booms, sprayers and irrigation equipment. Ground boom and aerial modes of application tend to use lower volumes of application applied in finer sprays than applications coincident with sprayers and spreaders and thus have a hi gher potential for off-target movement via spray drift. Therefore, risks from gro und boom and aerial applic ations are expected to result in the highest off-target concentr ations of oxamyl due to generally higher spray drift levels.

3.1. Label Application Rates and Intervals
Oxamyl labels may be categorized into tw o types: labels for manufacturing uses (including technical grade oxamyl and its fo rmulated products) and end-use products. While technical products, which contain oxamy l of high purity, are not used directly in the environment, they are used to make formulated products, which can be applied in specific areas to control nematodes, mites, and insects. The formulated product labels legally limit oxamyl’s potential use to only those sites that are specified on the labels.
Currently registered agricultu ral uses of oxamyl within California include apple, celery, cherry, citrus, clover, cotton, cucumb er, eggplant, garlic, melons (cantaloupe, honeydew, and watermelon), onion, peach, pe ar, pepper, potato, pumpkin, squash, tobacco, and tomato. Although use of oxamyl is not prohibited on tobacco in California, this crop is not gr own in the State, and is ther efore not considered in this endangered species assessment. The maximu m use patterns being assessed for uses of oxamyl are summarized in Table 10 and in Table 11. Current labels limit applications per season rather than per ye ar. However, the only assessed use for which multiple seasons may occur per year is celery. Therefore, labeled limits for number of applications per season can be in terpreted as annual limits for all uses except celery. In California, 2.5 crops of celery may be grown per year (USDA, 2000). Therefore, for this assessment, thr ee seasons of celery were assumed possible per year.

47Table 10. Oxamyl Uses by Foliar 1 Application Assessed for the CRLF. 2

Use Application Method Maximum Single Application Rate (lbs a.i./A) Maximum # Applications per Season Application Interval (days)
Apple (bearing fruit) Ground 2.0 1 ND Celery [1 season] 3 Ground, Aerial 1.0 6 5 Celery [3 seasons] 3 Ground, Aerial 1.0 18 5

Citrus (bearing fruit) Ground 1.0 6 14 Aerial 1.0 6 ND Chemigation 2.0 3 30 Clover (for seed) Ground, Aerial 1.0 2 14
Cotton Ground, Aerial 1.0 3 6

Cucumber Ground, Aerial 1.0 6 7 Chemigation 1.0 6 14 Eggplant Ground 1.0 6 7

Garlic Ground, Chemigation 2.0 2.25 14 Aerial 1.0 4.5 7

Melons 4 Ground, Aerial 1.0 6 7 Chemigation 1.0 6 14
Onion (dry bulb) Ground, Chemigation 2.0 2.25 14 Aerial 1.0 4.5 7
Non-bearing fruit 5 Ground 2.0 4 ND Aerial 1.0 8 ND
Pepper Ground, Aerial, Chemigation 1.0 6 7

Potato Ground, Aerial, Chemigation 1.0 8 5

Pumpkin Ground, Aerial 1.0 6 7 Chemigation 1.0 6 14
Squash Ground, Aerial 1.0 6 7 Chemigation 1.0 6 14

Tomato Ground and Aerial 1.0 8 5 Chemigation 2.0 4 7 ND = not defined 1 Foliar application includes groun d, aerial, and chemigation. 2 Uses assessed based on spreadsheet from BEAD dated June 10, 2008, confirmed by email from SRRD dated June 30, 2008. 3 If one season of celery is assumed per year, then 6 ap plications are modeled per year with an interval of 5 days. If three seasons of celery are assumed per year, then 18 applications are modeled per year with an interval of 5 days between within-season applications and between the last application in one season and the first application in the following season. 4 Melons include cantaloupe, honeydew, and watermelon. 5 Non-bearing fruit includes apple, cherry, citrus, peach, and pear uses.

48Table 11. Oxamyl Uses by Soil 1 Application Assessed for the CRLF. 2

Use Maximum Single Application Rate (lbs a.i./A) Maximum # Applications per Season Application Interval (days)
Apples (bearing fruit) NA NA NA Celery [1 season] 1.0 6 21 Celery [3 seasons] 1.0 18 21 Citrus (bearing fruit) NA NA NA Clover (for seed) NA NA NA
Cotton NA NA NA
Cucumber 4.0 1 NA Eggplant NA NA NA
Garlic 2.0 2.25 14
Melons 3 4.0 1 NA Onion (dry bulb) 2.0 2.25 14 Non-bearing fruit4 4.0 1 NA Pepper 1.0 6 7
Potato 4.0 1 NA Pumpkin 4.0 1 NA Squash 4.0 1 NA
Tomato 1.3 3 21 NA = not applicable 1 Soil applications include injection, incorporation, or in-furrow. 2 Uses assessed based on a spreadsheet from BEAD dated June 10, 2008 that was confirmed via an email from SRRD dated June 30, 2008. 3 Melons include cantaloupe, honeydew, and watermelon. 4 Non-bearing fruit includes apple, cherry, citrus, peach, and pear uses.

3.2. Aquatic Exposure Assessment

3.2.1. Modeling Approach
Aquatic exposures are quantitatively estimated for all of the assessed uses using scenarios that represent high exposure sites. Each of these sites represents a 10 hectare field that drains into a 1-hectare pond th at is 2 meters deep and has no outlet. Exposure estimates generated using the standard pond are intended to represent a wide variety of vulnerable water bodies that occur at the top of watersheds including pr airie pot holes, playa lakes, wetlands, vernal pools, man-made and natural ponds, and intermittent and first-order streams. As a group, there are factors that make these water bodies more or less vulnerable than the standard surrogate pond. Static water bodies that have larger ratios of drainage area to water body volume would be expected to have higher peak EECs than the standard pond. These water bodies will be either shallower or have large drainage areas (or both). Shallow water bodies tend to have limited additional storage capacity,

49and thus, tend to overflow and carry pesticid e in the discharge whereas the standard pond has no discharge. As watershed size in creases beyond 10 hectares, at some point, it becomes unlikely that the entire watershed is planted to a si ngle crop, which is all treated with the pesticide. Headwater streams can al so have peak concentrations higher than the standard pond, but they tend to persist for onl y short periods of time and are then carried downstream.
Crop-specific management practices for all of the assessed uses of oxamyl were used for modeling, including application rates, number of applica tions per year, application intervals, and the first applic ation date for each crop. The date of first application was developed within the constraints of the m odeled scenarios based on several sources of information including data provided by BEAD, a summary of individual applications from the CDPR PUR data, and Crop Profiles maintained by the USDA. More detail on the crop profiles and the previous assessments may be found at: http://www.ipmcenters.org/cropprofiles/index.cfm.

3.2.2. Model Inputs
The model input parameters used in PRZM to simulate oxamyl applications are provided in Table 12. These use patterns ar e those listed in Table 10 and in Table 11 that produce the maximum estimated aquatic exposure fo r each use. Because oxamyl use is not allowed on fruit-bearing cherri es, pears, or peaches, a us e pattern for non-bearing fruit was assessed that represents use on non-bear ing apples, cherries, citrus, pears, and peaches. Uses on fruit-bearing apples and citrus were assessed separately.
Applications were modeled as applied by airc raft for all uses other than fruit-bearing apples and citrus, eggplant, a nd garlic for the following reasons. The use patterns for fruit-bearing apples and eggpl ant do not include aerial app lication. Estimated exposure for ground applications to fruit- bearing citrus and garlic are higher than that for aerial applications. Furthermore, the application rate labeled for in-furrow applications to garlic is higher than that for other ground app lications. Therefore, garlic is the only use for which exposure was estimated assuming di rect application to the ground surface [chemical application method (CAM) = 1] rather than assuming application to the foliage (CAM = 2).
Although uses of oxamyl are seasonally limited, whereas model inputs must be annually limited, all uses of oxamyl have only one seas on per year with the exception of celery. Therefore, for uses other than celery, seas onal use patterns were modeled as annual use patterns. Use on celery was modeled assuming a range of one to three seasons per year in order to assess the potential exposure from different annua l cropping practices. However, the PRZM scenario used to model celery (C A row crop RLF) is parameterized for only one crop per year, which adds uncertainty to exposure estimates reflecting three seasons of use per year. Because the second and later seasons of use per ye ar occur in the model on a post-harvest field with no foliar interception, exposure es timates for three seasons of

50oxamyl use per year are expected to be more conservative than those that would result with a scenario parameterized for three crops per year.

Table 12. PRZM Scenarios and Input Parameters Describing Ox amyl Uses in California.

Uses Scenario 1 App. Rate (lbs a.i./A) App. per Year App. Interval (days) Date of Initial App. CAM Input IPSCND Input Application Efficiency/ Spray Drift Apple (bearing fruit) CA fruit STD 2.0 1 N/A May 1 2 3 0.99/0.01 Celery [1 season] 2 CA row crop RLF 1.0 6 5 Jan 15 2 1 0.95/0.05 Celery [3 seasons] 2 18 5 & 120 Citrus (bearing fruit) CA citrus STD 1.0 6 15 Mar 1 2 3 0.99/0.01
Clover CA alfalfa OP 1.0 2 14 Feb 1 2 1 0.95/0.05
Cotton CA cotton STD 1.0 3 6 Sep 19 2 1 0.95/0.05 Cucumber, melons, pumpkin, squash CA melons RLF 1.0 6 7 May 30 2 1 0.95/0.05
Eggplant CA melons RLF 1.0 6 7 May 30 2 1 0.99/0.01
Garlic CA garlic RLF 2.0 2.25 3 14 Mar 1 1 1 0.99/0.01 Non-bearing fruit CA fruit STD 1.0 8 7 Mar 1 2 3 0.95/0.05
Onion CA onion STD 1.0 4.5 3 7 Feb 1 2 1 0.95/0.05 Pepper CA row crop RLF 1.0 6 7 Feb 15 2 1 0.95/0.05
Potato CA potato RLF 1.0 8 5 Mar 1 2 1 0.95/0.05
Tomato CA tomato STD 1.0 8 5 Apr 15 2 1 0.95/0.05
1 All modeled scenarios were parameterized for irrigation. 2 If one season of celery is assumed per year, then 6 ap plications are modeled per year with an interval of 5 days. If three seasons of celery are assumed per year, then 18 applications are modeled per year with an interval of 5 days between within-season applications and an interval of 120 days between the last application in one season and the firs t application in the following season. 3 Fractions of applications per year indicate that a final application was modeled at that fraction of the maximum application rate. The general chemical and environmental fate data for oxamyl listed in Table 3 were used for generating model input paramete rs for PRZM and EXAMS (listed in Table 13). These inputs were determined in accordance with the Division’s “Guidance for Chemistry and Management Practice Input Parameters for Use in Modeling the Environmental Fate and Transport of Pestic ides” dated February 28, 2002. This guidance indicates that the hydrolysis rate at pH 7 (half-life of 8.0 days for oxamyl) should be modeled, which was done for risk estimation. However, oxamyl is relatively stable to hydrolysis in acidic water bodies. Therefore, stability to hydrolysis was also modeled in order to characterize potentia l exposure in acidic water bodies. Input/output files for PRZM/EXAMS modeling used to support risk estimation are available in Appendix C.

51Table 13. PRZM and EXAMS Chemica l Input Parameters for Oxamyl. Input Parameter Value Comment Source (MRID) Molecular Mass (g/mol) 219 Product chemistry data 40499702 Vapor Pressure (torr) 3.8 x 10 -7 Product chemistry data 42526101 Solubility in Water (mg/L) 2.8 x10 5 Product chemistry data 40499702 Organic Carbon Partition Coefficient (K OC ) (L/kg OC ) 35 Represents the average K OC . 46237301

Aerobic Soil Metabolism Half-life (days) 52 Represents the upper 90% confidence bound on the mean of six half-lives. ACC.# 63012 42820001 45176602 Aerobic Aquatic Metabolism Half-life (days) 6.6 Represents the upper 90% confidence bound on the mean of two half-lives adjusted for hydrolysis at pH 7. 45045305

Anaerobic Aquatic Metabolism Half-life (days) 0 No data; assumed stable. Aqueous dissipation will be dominated by hydrolysis. Not applicable

Hydrolysis Half-life (days) 8.0 Half-life at pH 7 40606516 Aqueous Photolysis Half-life (days) 14 Represents the maximum environmental phototransformation half-life. 40606515; 41058801

3.2.3. Results
The aquatic 1-in-10-year EECs for the various scenarios and application practices are listed in Table 14

. The use pattern resulting in the highest potential aquatic exposure is use on celery, assuming multiple seasons occur per year. If use on celery is limited to one season per year, the use patterns of maxi mum aquatic exposure are garlic and celery, followed closely by tomato. The 1-in-10-year exposure estimates from all use patterns range across approximately one order of magnitude. Variab ility between these EECs is mainly due to variations in modeled application rates, dates of application, meteorological conditions, and soil conditions. Because California has a Mediterranean climate and receives less precipitation in the summer than in other seasons, use patterns modeled with initial application dates in Ma y produced the lowest exposure estimates.
If oxamyl is applied adjacent to acidic water bod ies, where it is expected to be relatively stable to hydrolysis, peak exposure estimates slightly increase and time-averaged exposure estimates increase by two- to three- fold. For example, 1-in-10-year peak, 21­ day mean, and 60-day mean EECs increase to 53 ppb, 41 ppb, and 24 ppb, respectively, for use on celery with three seasons per yearand assuming stability to hydrolysis. Respective EECs for one season of celery per year and assuming stability to hydrolysis are 37 ppb, 26 ppb, and 19 ppb.

52Table 14. Aquatic 1-in-10-year EECs ( μ g/L) for Oxamyl Uses in California.

Uses Scenario Seasonal App. Rate (lbs a.i./A) Date of Initial App. Peak EEC 21-day average EEC 60-day average EEC Celery (3 seasons/yr) CA row crop RLF 18 15-Jan 45 18 9.0 Celery (1 season/yr) CA row crop RLF 6 15-Jan 31 13 6.8
Garlic CA garlic RLF 4.5 1-Mar 34 13 5.6
Tomato CA tomato STD 8 15-Apr 28 8.1 4.4 Non-bearing fruit CA fruit STD 8 1-Mar 21 8.2 4.6
Cotton CA cotton STD 3 19-Sep 19 7.2 3.1 Pepper CA row crop RLF 6 15-Feb 18 7.5 4.5 Citrus (bearing fruit) CA citrus STD 6 1-Mar 12 3.4 1.2
Clover CA alfalfa OP 2 1-Feb 7.8 3.7 1.7
Onion CA onion STD 4.5 1-Feb 7.6 4.2 2.1
Potato CA potato RLF 8 1-Mar 7.3 4.8 3.3 Cucumber, melons, pumpkin, squash CA melons RLF 6 30-May 6.7 1.9 1.2 Eggplant CA melons RLF 6 30-May 3.3 1 0.52 Apple (bearing fruit) CA fruit STD 2 1-May 3.2 1.2 0.51

3.2.4. Existing Monitoring Data
A critical step in the process of characteri zing EECs is comparing the modeled estimates with available surface water monitoring data. Included in this assessment are available data on oxamyl and its degradates from monitoring conducted in California, as reported in the U. S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) program ( http://water.usgs.gov/nawqa ) and in the California Department of Pesticide Regulation (CDPR) Surface Water Database ( http://www.cdpr.ca.gov/docs/emon/surfwtr/surfdata.htm ). CDPR does not provide ground water monitoring data for oxamyl or its degradates because they are not currently listed on the Ground Water Protection List ( http://www.cdpr.ca.gov/docs/emon/grndwtr/ ). The only analysis of a degradate of oxamyl in these data was an analysis of the oxime degradate of oxamyl in ground water conducted for the NAWQA program.

3.2.4.1. USGS NAWQA Surface Water Data

NAWQA data indicate that 33 surface water sites in California were monitored for oxamyl at various times from March 1993 to September 2005. Degradates of oxamyl were not analyzed for. Oxamyl was detect ed once at 0.025 μg/L in Orestimba Creek in

53Stanislaus Country in April, 2002. All other resu lts are reported as le ss than the limit of quantitation (LOQ = 0.012-0.4 μg/L). Oxamyl was not detected in the ephemeral Orestimba Creek two weeks before or after the detection in April, 2002 (U.S. Geological Survey 2007).

3.2.4.2. USGS NAWQA Ground Water Data
NAWQA data indicate that oxamyl was anal yzed in ground water at 318 sites in California at various times from August 1993 to September 2006. Oxamyl was not detected in ground water above the level of quantitation (0.012-0.54 μg/L) at any site. The oxime degradate of oxamyl was anal yzed in ground water once in April 2001, yielding no detection (LOQ=0.064 μg/L).

3.2.4.3. California Department of Pe sticide Regulation (CDPR) Surface Water Database

The CDPR Surface Water Databa se indicates that oxamyl wa s analyzed at 183 surface water sites in California at various tim es from February 1991 to October 2006. Degradates of oxamyl were not analyzed for. Oxamyl was detected at 11 of those sites at concentrations ranging from less than the leve l of quantitation (0.1-0.5 μg/L) to 2.8 μg/L. Detections occurred in the San Jose River and its tributaries (Stanislaus and Merced counties) in April of 1991, 1992, and 2002 and in the Pajaro River and its tributaries (Santa Cruz and Monterey counties) on D ecember 13, 1994. The highest detection of 2.8 μg/L occurred in a drainage ditch connected to the Pajaro River. Sites with detections were often reanalyzed for oxamyl within a fe w weeks to a few months, resulting in no detections, which suggests that the presence of oxamyl likely correlates with upslope usage and that residues dissipate in flowing water bodies.
The NAWQA and CDPR monitoring data are no t targeted to observe peak runoff from local uses of oxamyl. Therefore, the highe st monitored detections of the compound are expected to reflect time-averaged concentrations, such as 21-day mean concentrations, rather than peak concentrations in the envi ronment. Also, monitored surface water sites are generally located in flowing water bodi es; whereas modeled exposure estimates are based on a static water body adjacent to the use site where dilution and flow do not occur. Therefore, the highest monitored concentrations are not expected to often exceed modeled time-average exposure estimates.
The highest detection of oxamyl (2.8 μg/L) in the NAWQA and CDPR monitoring data is consistent with or within an order of magn itude of 1-in-10-year 21-day mean EECs (1-18 μg/L) of oxamyl for uses on individual crops.

3.3. Terrestrial Animal Exposure Assessment

T-REX (Version 1.3.1) is used to calculate dietary and dose-based EECs of oxamyl for the CRLF and its potential prey ( e.g. small mammals and terrestrial insects) inhabiting

54terrestrial areas. EECs used to represent th e CRLF are also used to represent exposure values for frogs serving as potential prey of CRLF adults. T-REX simulates a 1-year time period. For this assessment, foliar spray applications of oxamyl are considered using TREX. Applications directly to th e soil are not modeled using T-REX.

Terrestrial EECs for foliar formulations of oxamyl were derived for the uses summarized in Table 15. Given that no suitable data on in terception and subseque nt dissipation from foliar surfaces is available for oxamyl, the EFED default foliar dissipation half-life of 35 days is used based on the work of Willis a nd McDowell (1987). Two values specific to oxamyl are available in Willis and McDowell; however, these half-lives represent data collected from dislodgable residue s, and are, therefore, not representative of the foliar dissipation half-life. Use-specific input values, including number of applications, application rate and application interval are provided in Table 15. The maximum application rate for each use is modele d in T-REX and upper bound EECs are used for RQ calculations. An example output from T-REX is available in Appendix D

.
Table 15. Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for oxamyl with T-REX. Use (Application Method) Application Rate (lbs a.i./A) Number of Applications Application Interval (days) Apple (bearing fruit) (ground) 2.0 1 NA Celery (ground) [1season] 1.0 6 5 Celery (ground) [3 seasons] 1.0 18 5 Citrus (bearing fruit) (ground) 1.0 6 5* Clover (for seed) (ground) 1.0 2 14 Cotton (ground) 1.0 3 6 Cucumber (ground) 1.0 6 7 Eggplant (ground) 1.0 6 7 Garlic (ground) 2.0 2.25 14
Melons (ground) 1.0 6 7 Onion (ground) 2.0 2.25 14 Non-bearing (ground) 2.0 4 5* Pepper (ground) 1.0 6 7 Potato (ground) 1.0 8 5 Pumpkin (ground) 1.0 6 7 Squash (ground) 1.0 6 7 Tomato (chemigation) 2.0 4 7 NA = not applicable *because application interval is undefined on product labels, a 5 day interval value is assumed for modeling purposes based on the lowest interval value listed for any use

55For modeling purposes, exposures of the CRLF, as well as other frog species serving as prey to the CRLF, to oxamyl through cont aminated food are estimated using the EECs for the small bird (20 g) which consumes sm all insects. Dietary-based and dose-based exposures of potential prey are assessed using the small mammal (15 g) which consumes short grass. Upper-bound Kenega nomogram values reported by T-REX for these two organism types are used for derivation of EECs for the CRLF and its potential prey ( Table 16).

As indicated above, T-REX is also used to calculate EECs for terres trial insects exposed to oxamyl. Dietary-based EECs calculated by T- REX for small and large insects (units of μg a.i./g) are used to bound an estimate of e xposure to terrestrial in sects. Available acute contact toxicity data for bees exposed to oxamy l (in units of μg a.i./bee), are converted to μg a.i./g (of bee) by multiplying by 1 bee/ 0.128 g. Dietary-based EECs for terrestrial insects are later compared to the adjusted acute contact toxicity data for bees in order to derive RQs. Dietary-based EECs for small and large insects reported by T-REX as well as the resulting adjusted EECs are available in Table 17.

Table 16. Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based Exposures of the CRLF and its Prey to Oxamyl.

Use EECs for CRLF EECs for Prey (small mammals) Dietary-based EEC (ppm) Dose-based EEC (mg/kg-bw) Dietary-based EEC (ppm) Dose-based EEC (mg/kg-bw) Apple (bearing fruit) 270 308 480 458 Celery (1 season) 641 730 1140 1087 Celery (3 seasons) 1191 1356 2117 2018 Citrus (bearing fruit) 641 730 1140 1087 Clover (for seed) 237 270 421 402 Cotton 361 411 642 612 Cucumber 588 670 1047 998 Eggplant 588 670 1047 998 Garlic 629 717 1119 1274 Melons 588 670 1047 998 Onion 629 717 1119 1274 Non-bearing 936 1066 1665 1587 Pepper 588 670 1047 998 Potato 783 892 1392 1327 Pumpkin 588 670 1047 998 Squash 588 670 1047 998 Tomato 887 1011 1578 1504

56Table 17. EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to Terrestrial Invertebrate Prey Items. Use Small Insect EEC Large Insect EEC Apple (bearing fruit) 270 30.0 Celery (1 season) 641 71.3 Celery (3 seasons) 1191 132 Citrus (bearing fruit) 641 71.3 Clover (for seed) 237 26.4 Cotton 361 40.2 Cucumber 588 65.4 Eggplant 588 65.4 Garlic 629 70.0 Melons 588 65.4 Onion 629 70.0 Non-bearing fruit 936 104 Pepper 588 65.4 Potato 783 87.1 Pumpkin 588 65.4 Squash 588 65.4 Tomato 887 98.6

3.4. Terrestrial Plant Exposure Assessment

TerrPlant (version 1.2.2) is used to calculat e EECs for non-target plants inhabiting dry and semi-aquatic areas. Parameter values for application rate, drift assumption and incorporation depth are based upon the use a nd related application method A runoff value of 0.05 is utilized based on oxamyl’s sol ubility, which is classified by TerrPlant as >100 mg/L. For aerial and ground application methods, drift is assumed to be 5% and 1%, respectively.
Terrplant was used to model EECs from soil and foliar applications relevant to terrestrial plants. These EECs are calculated in the apple scenario in Table 18. The non-bearing fruit scenario reflects the highest applications rates, and thus the highest EECs, for soil and foliar applications. All foliar applications rates ( ≤ 2 lbs a.i./acre) are below the exposure level at which no effects were observe d (2.1 lbs a.i./acre) in the available tier 1 study; however, soil application rates at 4 lbs a.i./ acre are above this exposure level. Thus, modeling for soil applications generated EECs with the potential to adversely affect terrestrial plants. Due to oxamyl’s solubility, all pesticide concentrations were considered in runoff where highest exposure wa s expected to occur. An example output from TerrPlant v.1.2.2 is available in Appendix E.

57Table 18. TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semi-aquatic Areas Exposed to Oxamyl via Runoff and Drift.

Use Application rate (lbs a.i./A) Application method Drift Value (%) Spray drift EEC (lbs a.i./A) Dry area EEC (lbs a.i./A) Semiaquatic area EEC (lbs a.i./A)

Nonbearing fruit 4.0 Soil – incorporation, injection, infurrow 0 0 0.2 2.0

2.0 Foliar - ground 0.01 0.02 0.12 1.02 1.0 Foliar – aerial 0.05 0.01 0.06 0.51

4. Effects Assessment
This assessment evaluates the potential for oxamyl to directly or indirectly affect the CRLF or modify its designated critical habitat. As discussed in Section 2.7, assessment endpoints for the CRLF effects determination in clude direct toxic effects on the survival, reproduction, and growth of CRLF, as well as in direct effects, such as reduction of the prey base or modification of its habitat. In addition, potential m odification of critical habitat is assessed by evaluating effects to th e PCEs, which are components of the critical habitat areas that provide esse ntial life cycle needs of the CR LF. Direct effects to the aquatic-phase of the CRLF are based on toxic ity information for freshwater fish, while terrestrial-phase effects are based on avian to xicity data, given that birds are generally used as a surrogate for terrestrial-phase am phibians. Because the frog’s prey items and habitat requirements are dependent on th e availability of fr eshwater fish and invertebrates, small mammals, terrestrial invert ebrates, and aquatic a nd terrestrial plants, toxicity information for these taxa are also discussed. Acute (short-term) and chronic (long-term) toxicity information is characte rized based on registrant-submitted studies and a comprehensive review of the open literature on oxamyl.
As described in the Agency’s Overview Document (U.S. EPA, 2004), the most sensitive endpoint for each taxon is used for risk estimation. For this assessment, evaluated taxa include aquatic-phase amphibians, freshwaterfish, freshwater i nvertebrates, aquatic plants, birds (surrogate for terrestria l-phase amphibians), mammals, terrestrial invertebrates, and te rrestrial plants.
Toxicity endpoints are established based on data gene rated from guideline studies submitted by the registrant, and from open literature studies that meet the criteria for inclusion into the ECOTOX database maintained by EPA/Office of Research and Development (ORD) (U.S. EPA, 2004). Inorder to be included in the ECOTOX database, papers must meet the following minimum criteria:

o the toxic effects are related to single chemical exposure;

58o the toxic effects are on an aquatic or terrestrial plant or animal species;

o there is a biological effect on live, whole organisms;

o a concurrent environmental chemical concentration/dose or ap plication rate is reported; and

o there is an explicit duration of exposure.
Data that pass the ECOTOX screen are ev aluated along with the registrant-submitted data, and may be incorporated qualitatively or quantitatively into this endangered species assessment. In general, effects data in the open literature that are mo re conservative than the registrant-submitted data are considered. The degree to which open literature data are quantitatively or qualitatively characterized for the effects determination is dependent on whether the information is releva nt to the assessment endpoints ( i.e. , maintenance of CRLF survival, reproduction, and growth) identified in Section 2.8. For example, endpoints such as behavior modifications are likely to be qualitativ ely evaluated, because quantitative relationships between modifications and reduction in species survival, reproduction, and/or growth ar e not available. Although the effects determination relies on endpoints that are relevant to the asse ssment endpoints of survival, growth, or reproduction, it is important to note that the full suite of subletha l endpoints potentially available in the effects literature (regardle ss of their significance to the assessment endpoints) are considered to defi ne the action area for oxamyl.
Toxicity data for oxamyl available in the ECOTOX database on 7/31/2008 were considered for this assessment. Citations of a ll open literature not c onsidered as part of this assessment because they were either re jected by the ECOTOX screen or accepted by ECOTOX but not used ( e.g. , the endpoint is less sensitive) are included in Appendix F. Appendix F also includes a rationale for rejec tion of those studies that did not pass the ECOTOX screen and those that we re not evaluated as part of this endangered species risk assessment. A detailed spreadsheet of the available accepted ECOTOX open literature data, including the full suite of lethal and subl ethal endpoints is presen ted in Appendix G. Appendix H includes a summary of the hum an health effects data for oxamyl.
In addition to registrant-submitted and open lite rature toxicity information, other sources of information, including use of the acute pr obit dose response rela tionship to establish the probability of an individual effect and re views of the Ecological Incident Information System (EIIS), are conducted to further refi ne the characterization of potential ecological effects associated with exposure to oxamyl . A summary of the available incident information for oxamyl is provided below.

It should be noted that where data were provided in study report s, sublethal effects observed during acute toxicity studies are described in this effects characterization. These sublethal effects raise concern about the effects of oxamyl; however, it is not possible to quantitatively li nk these effects to the select ed assessment endpoints for the listed CRLF ( i.e. , survival, growth, and reproduction of individuals and maintenance of critical habitat PCEs). Therefore, poten tial sublethal effects on specific taxa are

59evaluated qualitatively. Definitive endpoints, such as LC 50 s are used for quantifying RQs in this assessment.

4.1. Toxicity of Oxamyl to Aquatic Organisms Table 19 summarizes the most sensitive aquatic toxicity endpoints for the CRLF, based on an evaluation of the submitted studies as previously discussed. Open literature data for aquatic organisms was not considered re levant to this ecological risk assessment because none of the toxicity endpoints were more sensitive that those from submitted studies. Toxicity to aquatic fish and invertebrates is cate gorized using the system shown in (Table 20). Toxicity categories fo r aquatic plants have not been defined.

Table 19. Freshwater Toxi city Profile for Oxamyl. Assessment Endpoint Species Toxicity Value Used in Risk Assessment Citation MRID # Comment

Acute Direct Toxicity to Aquatic-Phase CRLF Oncorhynchus mykiss (Rainbow Trout) 96-hr LC 50 = 4.2 mg a.i./L
Slope = NA 400980-01 Supplemental – per EFED policy (USEPA 2006); some deviations from guideline requirements Chronic Direct Oncorhynchus NOAEC = Acceptable – NOEC is Toxicity to Aquatic­ mykiss 0.77 mg a.i./L 409011-01 based on embryo hatching Phase CRLF LOAEC = 1.5 mg a.i./L Slope = NA and larval swim-up

Indirect Toxicity to Aquatic-Phase CRLF via Acute Toxicity to Freshwater Invertebrates ( i.e. prey items) Chironomus plumosus (midge) 48-hr EC 50 = 0.18 mg a.i./L
Slope = NA 400980-01 Acceptable – NOAEC endpoint based on egg production and egg fertility

Indirect Toxicity to Aquatic-Phase CRLF via Chronic Toxicity to Freshwater Invertebrates ( i.e. prey items) Chironomus plumosus (midge) NOAEC = 0.012 mg a.i./L
Slope = NA N/A Based on an acute to chronic ratio using daphnid ( Daphnia magna ) endpoints [4.2/0.027 = 15.5 (ACR)]

Indirect Toxicity to Navicula 120-hourEC 50 = Acceptable – NOEC and Aquatic-Phase CRLFvia Toxicity to Nonpelliculosa (algae) 0.12 mg a.i./L 455461-04 EC 50 values are based on cell density. vascular Aquatic Slope = 0.872 (±) Plants 0.168 Indirect Toxicity to Lemna gibba 14-day EC 50 = Supplemental – due to Aquatic-Phase CRLF via Toxicity to (duckweed) 30 mg a.i./L 455461-03 lack of constant exposure of test organisms to the Vascular Aquatic Slope = 4.56 (±) test material Plants 0.441

60Table 20. Categories of Acute To xicity for Aquatic Organisms. LC 50 (mg/L) Toxicity Category < 0.1 Very highly toxic > 0.1 - 1 Highly toxic > 1 - 10 Moderately toxic > 10 - 100 Slightly toxic > 100 Practically nontoxic

4.1.1. Toxicity to Freshwater Fish
Given that oxamyl toxicity data are no t available for aquatic -phase amphibians, freshwater fish data are used as a surrogate to estimate direct acute and chronic risks to the CRLF. Freshwater fish toxicity data are also used to assess potential indirect effects of oxamyl to the CRLF. Effects to freshwater fish resulting from exposure to oxamyl could indirectly affect the CRLF via reduction in available food. As discussed in Section 2.5.3, over 50% of the prey mass of the CRLF ma y consist of vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).
Oxamyl is moderately toxic to freshwater fi sh on an acute exposure basis. The most sensitive freshwater species tested is rainbow trout, with a 96-hour LC 50 value of 4.2 mg a.i./L (MRID: 400980-01). Two acute stud ies available for bluegill sunfish ( Lepomis macrochirus ) and rainbow trout ( Salmo gairderii ) reported 96-hour LC 50 values of 5.6 mg a.i./L (MRID: 66914) and 4.2 mg a.i./L (MRID: 66916), respectively.
Chronic toxicity data are available for the fathead minnow and the rainbow trout exposed to oxamyl. The chronic exposure involving the fathead minnow resulted in effects observed at all test concentr ations and a LOAEC <1.0 mg/L (effects to larval survival were observed) (MRID: 94663). The chronic exposure involving the rainbow trout resulted in a discrete NOAEC of 0.77 mg/L and a LOAEC of 1.5 mg/L, with effects to embryo hatch and larval swim-up observ ed at the LOAEC (MRID 409011-01). The toxicity data from the rainbow trout study is used to represent the chronic toxicity endpoint for the aquatic-phase CRLF because both the NOAEC and the LOAEC are discrete values. By using the rainbow trout study, however , chronic risk is potentially underestimated due to lack of a NOAEC in the fathead minnow study.

4.1.2. Toxicity to Freshwater Invertebrates
Freshwater aquatic invertebrate toxicity data are used to as sess potential indirect effects of oxamyl to the CRLF. Effects to freshwat er invertebrates resulting from exposure to oxamyl could indirectly affect the CRLF vi a reduction in available food items. As discussed in Section 2.5.3, the main food s ource for juvenile aquatic- and terrestrialphase CRLFs is thought to be aquatic inve rtebrates found along the shoreline and on the water surface, including aquatic sowbugs, larval alderf lies and water striders.

61Oxamyl is highly toxic (defined as: LC 50 >0.1-1 mg a.i./L) to fr eshwater invertebrates on an acute exposure basis. The most sensitive species tested is Chironomus plumosus (midge), with a 48-hour EC 50 value of 0.18 mg a.i./L (MRI D: 400980-01). Acute toxicity data are also available for Daphnia magna (daphnid). Two studies on oxamyl exposure to daphnids resulted in a 48-hour LC 50 of 0.42 mg a.i./L (MRID: 400980-01) and 5.7 mg a.i./L (MRID: 94664).
The most sensitive chronic toxicity data av ailable indicated a NOAE C of 0.027 mg a.i./L and a LOAEC of 0.050 mg a.i./L based on effects to growth and reproduction of Daphnia magna (MRID: 450678-01). The 48-hour LC 50 (0.42 mg a.i./L) from the study on daphnids is higher than the lowest acute e xposure level tested in the aforementioned study on midges (MRID: 400980-01). Therefore, the chronic endpoint used in this assessment was derived using the acute-to-chr onic ratio (ACR) for daphnids applied to the more sensitive acute midge endpoint ( 0.18 mg a.i./L). The calculated NOAEC value for midge is 0.012 mg a.i./L based on the daphnid-derived ACR of 15.5.

4.1.3. Toxicity to Aquatic Plants
Aquatic plant toxicity studies were used as one of the measures of effect to evaluate whether oxamyl could affect primary production and the availability of aquatic plants as food for CRLF tadpoles. Primary productivity is essential for indi rectly supporting the growth and abundance of the CRLF.
A submitted study on algae indicated oxamyl has an EC 50 of 120-hour EC 50 value of for decreased cell density (MRID: 455461-04). A submitted study on aquatic vascular plants (duckweed, Lemna gibba ) reported a 14-day EC 50 value of 30 mg a.i./L based on decreased frond count (MRID: 455461-03).

4.2. Toxicity of Oxamyl to Terrestrial Organisms

Table 21 summarizes the most sensitive terrestrial toxicity endpoints for the CRLF, based on an evaluation of submitted studies. No additional toxicity data for terrestrial organisms exposed to oxamyl were identified in the open literature. Acute toxicity to terrestrial animals is categorized usin g the classification system shown in Table 22 (U.S. EPA, 2004). Toxicity categories for terrestrial plants have not been defined.

62Table 21. Terrestrial Toxicity Profile for Oxamyl. Endpoint Species Toxicity Value Used in Risk Assessment Citation MRID# Comment

Acute Direct Toxicity to Terrestrial-Phase CRLF (LD 50 ) Anas platyrhynchos (Mallard Duck) LD 50 = 3.16 mg/kg-bw Slope = NA 94660 Acceptable

Acute Direct Toxicity to Terrestrial-Phase CRLF (LC 50 ) (Colinus virginianus) (Northern Bobwhite Quail) LC 50 = 340 mg/kg-diet

Slope = NA 406065-11 Acceptabl e – NOAEC < 39 mg/kg-diet based on signs of toxicity and reduction in body weight gain and feed consumption Chronic Direct Toxicity to Terrestrial-Phase CRLF Anas platyrhynchos (Mallard Duck) NOAEC = 10 mg/kg-diet Slope = NA 00116609 Acceptable – NOAEC endpoint based on egg production and egg fertility
Indirect Toxicity to Terrestrial-Phase CRLF (via acute toxicity to mammalian prey items) Rattus norvegicus (laboratory rat) Male LD 50 = 3.1 mg/kg-bw Female LD 50=

2.5 mg/kg-bw 63011 Acceptable -Slope for male LD 50 =9.3 ± 4.6 -Slope for female LD 50 =18.0 ± 8.6 Indirect Toxicity to Terrestrial-Phase CRLF (via chronic toxicity to mammalian prey items) Rattus norvegicus (laboratory rat) NOAEC = 25 mg/kg-diet Slope = NA 416608-01 Acceptabl e – Decreased body weight and live pups/litter during lactation observed at LOAEC (75 mg/kg-diet) Indirect Toxicity to Terrestrial-Phase CRLF (via acute toxicity to terrestrial invertebrate prey items) Apis mellifera (Honey bee) LD 50 = 0.31 μg/bee Slope = NA 05001991 Acceptable

Indirect Toxicity to Terrestrial- and Aquatic-Phase CRLF (via toxicity to terrestrial plants) Seedling Emergence Monocots 21-day EC 25 >2.1 lbs a.i./A Slope = NA 455461-01 Acceptable –Tier I Terrestrial Plant Seedling Emergence toxicity study
Seedling Emergence Dicots 21-day EC 25 >2.1 lbs a.i./A Slope = NA 455461-01 Acceptable –Tier I Terrestrial Plant Seedling Emergence toxicity study
Vegetative Vigor Monocots 21-day EC 25 >2.1 lbs a.i./A Slope = NA 455461-02 Supplemental—per EFED policy (USEPA 2006); insufficient numbers of plants per treatment group Vegetative Vigor Dicots 21-day EC 25 >2.1 lbs a.i./A Slope = NA 455461-02 Supplemental—per EFED policy (USEPA 2006); insufficient numbers of plants per treatment group

63Table 22. Categories of Acute Toxicity for Avian and Ma mmalian Studies. Toxicity Category Oral LD 50 (mg/kg) Dietary LC 50 (ppm) Very highly toxic < 10 < 50 Highly toxic 10 - 50 50 - 500 Moderately toxic 51 - 500 501 - 1000 Slightly toxic 501 - 2000 1001 - 5000 Practically non-toxic > 2000 > 5000

4.2.1. Toxicity to Birds
As specified in the Overview Document, the Agency uses birds as a surrogate for terrestrial-phase amphibians when amphibian toxi city data are not available for this taxa (U.S. EPA, 2004). No terrestrial-phase amphibian data are available for oxamyl; therefore, acute and chronic avian toxicity data are used to assess the potential direct effects of oxamyl to te rrestrial-phase CRLFs.
Oxamyl is considered very highly toxic to birds on an acute oral exposure basis and highly toxic to birds on a dietary exposure basis ( Table 22). The oral acute LD 50 value for mallard duck ( Anas platyrhynchos ) , the most sensitive species tested, is 3.16 mg/kgbw (MRID: 94660).

Sublethal effects were noted in the acute or al exposure studies on mallard ducks (MRID: 94660) and bobwhite quail (MRID: 406065-11). Clinical observ ations of oxamyl-treated mallard ducks reported the following eff ects: loss of coordination at 1.00 and 3.16 mg/kg-diet; ruffled feathers at 1.00 mg/kg-diet; weakness and slow movement at 3.16 mg/kg-diet; discharge from eyes and nose at 3.16 and 10.0 mg/kg-diet; and apparent leg paralysis at 3.16, 10.0, 31.6, and 100 mg/kg-diet. Reported signs of overt toxicity in bobwhite quail occurred at test concentrations of 78 ppm and higher, and included lethargy, ruffled appearance, depression, wing droop, loss of coordination, reduced reaction to external stimuli, shallow and rapid respirati on, lower limb weakness, head tremors, and prostrate posture.
The dietary-based acute LC 50 value for the bobwhite quail is 340 mg/kg-diet (MRID: 406065-11). In the acute dietary-based study, the NOAEC was < 39 mg/kg-diet, the lowest test concentration, based on signs of toxicity and reduction in body weight gain and feed consumption.
Reproduction toxicity studies are used to a ssess chronic avian exposure to oxamyl. A study submitted to the Agency involving mallard ducks exposed to oxamyl (MRID: 00116609) reported a NOAEC of 10 mg/kg-diet and a LOAEC of 50 mg/kg-diet. The LOAEC determination was based on eff ects to egg production and egg fertility.

644.2.2. Toxicity to Mammals
Mammalian toxicity data are used to assess potential indirect effects of oxamyl to the terrestrial-phase CRLF. Effects to small mammals resulting from exposure to oxamyl could indirectly affect the CRLF via reduction in available food. As discussed in Section 2.5.3, over 50% of the prey mass of the CRLF ma y consist of vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).
Available data indicate that oxamyl is very highly toxic to mammals (LD 50 <10 mg/kg) on an acute oral exposure basis. The mostsensitive endpoint based on submitted studies on laboratory rats ( Rattus norvegicus ) is an LD 50 of 2.5 mg/kg-bw for females and 3.1 mg/kg-bw for males (MRID: 63011). Subletha l effects from acute exposure were also observed, although dosage concentration was not reported: tremors, fasciculations (muscle twitches), exophthalmos (eye bulgi ng), salivation, chrom odacryorrhea (bloody tears), stained faces and perineal ar eas, and slight weight loss.
A two-generation reproduction study on labor atory rats was conducted to determine effects of oxamyl on mamma lian reproduction. Reproductive toxicity was observed in both generations as a significantly decreased viability index and significantly decreased body weight and live pups/litter during lact ation. The study reported a NOAEC of 25 mg/kg-diet (approximately 1.7 and 2.0 mg/kg/da y for males and females, respectively) and a LOAEC of 75 mg/kg-diet (approximate ly 5.2 and 6.6 mg/kg/day for males and females, respectively) (MRID: 416608-01).

4.2.3. Toxicity to Terrestrial Invertebrates
Terrestrial invertebrate toxicity data are used to assess potenti al indirect effects of oxamyl to the terrestrial-phase CRLF. Effects to te rrestrial invertebrates resulting from exposure to oxamyl could indirectly affect the CRLF via reduction in available food.
Oxamyl is classified as very highl y toxic to beneficial insects (LD 50 = 0.31 μg/bee) on an acute exposure basis.
A 1986 study conducted by Atkins, E.L. and D. Kellum (ECOTOX reference #70351) examined the toxicological and morphoge nic effects to honeybee brood from the formulated product, Vydate® L, with a purity of 24% active ingredient oxamyl. Larvae inside of the hive of 1-2, 3-4, and 5-6 days old were exposed to varying levels of oxamyl in their food to determine LD 50 values for each group. According to the study, oxamyl was generally much more toxic to larvae than to adults, particul arly to those of 1-2 days. For larvae of 1-2 days old, LD 50 values were reported at 0.00013 μg/individual. For larvae 3-4 and 5-6 days old, LD 50 values were reported at 0.026 μg/individual and 0.057 μg/individual, respectively. The study resulted in an overall LD 50 value of 0.367 μg/individual for all larvae test ed. It should be noted, howe ver, that there are several limitations associated with this study. First, no raw mortality data were provided to allow

65the reviewer to recalculate the reported LD 50 values. Second, the formulation Vydate® L was used instead of the technical product. Third, dosage number and dosage levels were not reported directly.

4.2.4. Toxicity to Terrestrial Plants
Terrestrial plant toxicity data are used to evaluate the potential for oxamyl to affect riparian zone and upland vegetation within the action area for the CRLF. Impacts to riparian and upland ( i.e. , grassland, woodland) vegetation co uld result in indirect effects to both aquatic- and terrestrial-phase CRLFs , as well as modifi cation to designated critical habitat PCEs via increased sedi mentation, alteration in water quality, and reduction of upland and riparian habitat th at provides shelter, foraging, predator avoidance and dispersal for j uvenile and adult CRLFs.
In tests involving exposures of oxamyl to terr estrial plants, effects were only observed in dicots. In a Tier I seedling emergence study (MRID: 455461-01) involving 4 monocot species and 6 dicot species, significant eff ects were observed in tomatoes (significant effects to height) and percent inhibition ranged from -14.3% to 11.5% compared to the control; however no effect was ≥ 25% relative to the control. In a Tier 1 vegetative vigor study (MRID: 455461-02) involving 4 monocot sp ecies and 6 dicot species, significant effects to height and weight were observed in soybeans with a percent inhibition of -13.1%; however, no effect was ≥ 25% relative to the control. This study was classified as supplemental due to insufficient numb ers of plants per treatment group.

4.3. Incident Database Review

A search of the EIIS (Environmental Inci dent Information System) database for ecological incidents (run on December 2, 2008) identified 3 incidents involving exposures of oxamyl.

The first incident involved th e death of hundreds of fish and over 100 birds in Alamance County, North Carolina, in May of 1991. Fishkills were observed in several ponds ( ≥ 1 Acre in size) near farms following high runoff events. Several pesticides (See Table 23) had recently been used in the area, and motor oil ran into the ponds. More than 100 ducks, 1 turkey, 5 cardinals and 7 blackbirds we re observed dead. Th e certainty that the deaths of the animals were associated with exposure to oxamyl was considered probable but the legality of use was indicated as “intentional misuse” (Incident # I000799-003).

66Table 23. Pesticides and their asso ciated certainty classification as sociated with incident #I000799­ 003.

Pesticide Use Site Legality of Use Certainty that incident was associated with pesticide exposure* 2,4-D Home/lawn Undetermined Probable Carbaryl Shrubbery Undetermined Possible
Diazinon Residential turf Undetermined Possible
Dicamba NR Undetermined Unlikely Mecoprop NR Undetermined Unlikely

Oxamyl NR Intentional misuse** Probable Pentachlorophenol NR Undetermined Possible * Incidents included in EIIS are defined by a certainty index associated with the likelihood that the pesticide application described resulted in the observed incident. The certainty index defines incidents as unrelated, unlikely, possible, probable and highly probable. **Corn was laced with oxamyl as bait for ducks. NR = not reported
The second incident, with a certainty index of ‘possible’ and legality of use indicated as undetermined, involved the death of a red- cockaded woodpecker in Sussex County, Virginia, in February of 2003. The immediate cause of death was identified as head trauma. Tissue analysis identified the presen ce of oxamyl in the liver and gastrointestinal track at 7.3 and 1.2 ppm, respectiv ely. Brain acetylcholine estera se levels were depressed (83% of normal) (Incident #I014344-001).

The third incident involved the deaths of 13 laughing gulls and 1 cattle egret in the British Virgin Islands in 2004. The cause of mortality was defined as “toxicosis caused by both methomyl and oxamyl.” The certainty that the deaths of the birds were associated with exposure to either pesticide was cons idered possible and the legality of use was indicated as undetermined(Incident #I018980-010).
One source of uncertainty associated with this database is the natu re of reporting of incidents. Many more incidents may have o ccurred due to oxamyl exposures but may not have been reported due to various factors, such as a lack of reporting, or a lack of witnessing of effects. Therefore, the lack of an incident report does not necessarily indicate a lack of an incident.

675. Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations. Risk characterization is used to determine the potential for direct and/or indirect effects to the CRLF or for modification to its designated critical habitat from the use of oxamyl in CA. The risk characterization provides anestimation (Section 5.1) and a description (Section 5.2) of the likel ihood of adverse effects; articulates risk assessment assumptions, limitations, and uncertainties; and synthesi zes an overall conclusion regarding the likelihood of adverse effects to the CRLFor its designated critical habitat ( i.e. , “no effect,” “likely to adversely affect,” or “may affect, but not likely to adversely affect”). The risk characterization describes some of the uncertainties associated with this endangered species assessment (Section 5.3). Th e risk characterizati on is concluded by revisiting the risk hypotheses (Section 5.4) defined in the problem formulation.

5.1. Risk Estimation
Risk is estimated by calculating the ratio of e xposure to toxicity. Th is ratio is the risk quotient (RQ), which is then compared to pr e-established acute a nd chronic levels of concern (LOCs) for each category evaluated ( Appendix B ). RQs representing acute and chronic exposures to the CLRF, its prey a nd its habitat are defined below. For acute exposures to the CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the LOC is 0.05. For acute e xposures to the terres trial-phase CRLF and mammals, the LOC is 0.1. The LOC for chroni c exposures to CRLF and its prey, as well as acute exposures to plants is 1.0.

5.1.1. Exposures in the Aquatic Habitat

5.1.1.1. Direct Effects to Aquatic-Phase CRLF
Direct acute effects to the aquatic-phase CRLF are based on peak 1-in-10-year EECs in the standard pond and the lowest acute toxicity value for freshwater fish. In order to assess direct chronic risks to the CRLF, 1-in -10-year 60-day-mean EECs and the lowest chronic toxicity value for freshwater fish are used. These EECs are divided by acute and chronic toxicity data for the rainbow trout ( Table 19), a surrogate species for the aquaticphase CRLF.
RQs are derived based on the highest aqua tic EEC, which corresponds to 3 seasons of oxamyl applications to celery per year ( Table 14). The resulti ng RQs representing acute and chronic exposures to the aquatic-phase CRLF (both 0.01; Table 24) are less than the acute and chronic LOCs (0.05 and 1.0, respec tively). All other EECs would result in lower RQs. Therefore, all uses of oxamyl rele vant to California result in RQ values that are below LOCs for acute and chronic exposur es of the aquatic-phase CRLF to oxamyl.

68Table 24. Summary of Direct Effect RQs for the Aquatic-phase CRLF. Exposure 1-in-10-year EEC ( μ g/L) a Toxicity Value ( μ g/L) b RQ
Acute 45 (Peak) LC 50 = 4,200 0.01 Chronic 9 (60-d mean) NOAEC = 770 0.01

aThe highest 1-in-10-year EECs based on 3 applications per year of oxamyl to celery, ( Table 14). b Based on data for the rainbow trout, a su rrogate species for the aquatic-phase CRLF.

5.1.1.2. Indirect Effects to Aquati c-Phase CRLF via Reduction in Prey
Non-vascular Aquatic Plants
Indirect effects of oxamyl to the aquatic-phase CRLF (ta dpole stage) via reduction in non-vascular aquatic plants in its diet are based on 1-in-10-year peak EECs from the standard pond and the lowest toxicity value (EC 50 ) for aquatic non-vascular plants. The highest RQ for non-vascula r aquatic plants is 0.38, calculated by dividing the highest peak EEC (45 μg/L; Table 14) by the lowest toxicity value for non-vascular aquatic plants (120 μg/L; Table 19). RQs generated for a ll other uses of oxamyl are <0.38. Therefore, RQs representing exposures of non-va scular aquatic plants to oxamyl applied at maximum label rates to all uses relevant to California are less than the LOC for aquatic plants (1.0).
Aquatic Invertebrates
Indirect acute effects to the aquatic-phase CRL F via effects to aquatic invertebrates (prey of juvenile and adult aquatic-phase CRLF) are based on 1-in-10-year peak EECs in the standard pond and the lowest acute toxicity value for freshwater invertebrates. For chronic risks, 1-in-10-year 21-day-mean EECs and the lowest chronic toxicity value for invertebrates are used to derive RQs.
RQ values representing acute oxamyl exposures to aquatic invertebrate s indicate that the majority of oxamyl uses result in RQs ( Table 25) that are sufficient to exceed the listed species LOC (0.05). Celery, modeled with thre e seasons, has the highest acute RQ with a value of 0.25.
RQ values representing chronic oxamyl exposur es to aquatic inverteb rates indicate that two uses of oxamyl (specifically ce lery and garlic) result in RQs ( Table 25) that are sufficient to exceed the listedspecies LOC (1.0). The highe st RQ for chronic exposures of aquatic invertebrates to oxamyl is 1.5, cal culated by dividing the highest 1-in-10 year 21-day mean (18 μg/L; Table 14) by the lowest chroni c toxicity value for aquatic invertebrates (12 μg/L; Table 19).

69Table 25. Acute and Chronic RQs for aqua tic invertebrates exposed to oxamyl.

Use 1-in-10­ year Peak EEC (μg/L) Indirect Effects Acute RQ 1 Individual Chance of Effects 3 1-in-10-year 21-day-mean (μg/L) Indirect Effects Chronic RQ 4 Celery (3 seasons) 45 0.25 2 0.34% 18 1.5 5 Celery (1 season) 31 0.17 2 0.03% 13 1.1 5
Garlic 34 0.19 2 0.06% 13 1.1 5
Tomato 28 0.16 2 0.02% 8.1 0.7 Non-bearing fruit 21 0.12 2 <0.01% 8.2 0.7 Pepper 18 0.10 2 <0.01% 7.5 0.6 Cotton 19 0.11 2 <0.01% 7.2 0.6 Citrus (bearing fruit) 12 0.07 2 <0.01% 3.4 0.3 Potato 7.3 0.04 <0.01% 4.8 0.4 Clover 7.8 0.04 <0.01% 3.7 0.3 Onion 7.6 0.04 <0.01% 4.2 0.4 Cucumber, melons, pumpkin, squash 6.7 0.04 <0.01% 1.9 0.2 Apple (bearing fruit) 3.2 0.02 <0.01% 1.2 0.1 Eggplant 3.3 0.02 <0.01% 1.0 0.1
1 Acute RQ = use-specific 1-in-10-year peak EEC / acute freshwater invertebrate endpoint (EC 50 = 180 μg/L). 2 Exceeds listed species LOC fo r acute exposures (0.05). 3 Calculated using default slope = 4.5. 4 Chronic RQ = use-specific 1-in -10-year 21-day-mean EEC / chronic freshwater ACR endpoint (NOAEC = 12 μg/L). 5 Exceeds listed species LOC for chronic exposures (1.0).

Fish and Frogs
Fish and frogs also represent potential prey items of adult aquatic-phase CRLFs. RQs associated with acute and chronic direct toxi city to the CRLF are used to assess potential indirect effects to the CRLF based on a reduc tion in freshwater fish and frogs as food items. Acute and chronic RQs ( ≤ 0.01) are less than the acute and chronic LOCs for fish and frogs representing potential prey of CRLF (0.05 and 1.0, respectively).

5.1.1.3. Indirect Effects to CRLF via Reduction in Habitat and/or Primary Productivity (Freshwater Aquatic Plants)
Indirect effects to the aqua tic-phase CRLF via reduction in habitat resulting from oxamyl exposures are based on 1-in-10-year peak EECs from the standard pond and the lowest toxicity value (EC 50 ) for aquatic non-vascular and vascul ar plants. Because there are no obligate relationships between the CRLF and any aquatic plant species, the most sensitive EC 50 values, rather than NOAEC valu es, are used to derive RQs

70The highest RQ for non-vascular aquatic plan ts is 0.38, calculated by dividing the highest peak EEC (45 μg/L; Table 14) by the lowest toxicity value for non-vascular aquatic plants (120 μg/L; Table 19). Non-vascular plant RQs generated for all other uses of oxamyl relevant to California are <0.38. Th erefore, RQs for representing exposures of non-vascular aquatic plants to oxamyl applied to all labeled uses relevant to California are less than the LOC for aquatic plants (1.0).
The highest RQ for vascular aquatic plants is <0.01, calcu lated by dividing the highest peak EEC (45 μg/L; Table 14) by the lowest toxicity va lue for vascular aquatic plants (30,000 μg/L; Table 19). Vascular plant RQs generated for all other uses of oxamyl are <0.01. Therefore, RQs for representing exposures of vascular aquatic plants to oxamyl applied to all labeled uses relevant to Califor nia are less than the LOC for aquatic plants (1.0).

5.1.2. Exposures in the Terrestrial Habitat

5.1.2.1. Direct Effects to Terrestrial-phase CRLF
As discussed in Section 3.3, potential direct effects to terrestrial- phase CRLFs are based on foliar (ground, aerial, chemigation) applications of oxamyl. Only foliar applications are modeled, because T-REX is not appropria te for modeling soil applications with incorporation.

Potential direct acute effect s to the terrestrial-phase CRL F are derived by considering dose- and dietary-based EECs modeled in T- REX for a small bird (20 g) consuming small invertebrates ( Table 16) and acute oral and subacu te dietary toxicity endpoints for avian species ( Table 21). Available exposure and e ffects data for birds exposed to oxamyl are used as surrogates for the terres trial-phase CRLF. Resulting acute dietaryand dose-based RQs for all assessed uses of oxamyl exceed the Agency’s acute endangered species LOC of 0.1 for the CRLF ( Table 26).

Potential direct chronic eff ects of oxamyl to the terrestrial-phase CRLF are derived by considering dietary-based expos ures modeled in T-REX for a small bird (20g) consuming small invertebrates ( Table 16). Chronic effects are esti mated using the lowest available toxicity data for birds. EECs are divided by toxicity values to estimate chronic dietarybased RQs. The chronic dietary-based RQ s for the terrestrial-phase CRLF exceed the Agency’s chronic LOC of 1.0 ( Table 26) for all assessed uses of oxamyl.

71Table 26. RQs for the terrestrial- phase CRLF based on acute and chronic exposures from foliar applications of oxamyl at maximum use ra tes. These RQs were generated using T-REX.

Use Dosed-based Acute RQ Dietary-based Acute RQ Dietary-based Chronic RQ
Apple (bearing fruit) 187 0.79 27 Celery (1 season) 445 1.9 64 Celery (3 seasons) 827 3.5 119 Citrus (bearing fruit) 445 1.9 64 Clover (for seed) 164 0.70 24 Cotton 250 1.1 36 Cucumber 408 1.7 59 Eggplant 408 1.7 59 Garlic 437 1.9 63 Melons 408 1.7 59 Onion 437 1.9 63 Non-bearing fruit 650 2.8 94 Pepper 408 1.7 59 Potato 643 2.3 78 Pumpkin 408 1.7 59 Squash 408 1.7 59 Tomato 616 2.6 89

5.1.2.2. Indirect Effects to T errestrial-Phase CRLF via Reduction in Prey

Terrestrial Invertebrates

In order to assess the risks of oxamyl exposures to terrestrial invertebrates, which are prey of CRLF in terrestrial habitats, the honey bee is used to represent terrestrial invertebrates. The toxicity value for terrestrial invertebrates is based on the weight of an adult honey bee and is calculated by multiply ing the lowest available acute contact LD 50 of 0.31 μg a.i./bee by 1 bee/0.128g, which equals 2.4 ppm (μg a.i./g) of bee. EECs (μg a.i./g of bee) calculated by T- REX for small and large insects ( Table 17) are divided by the toxicity value for terrestrial invertebrates to generate RQs for terrestrial invertebrates. For all uses of oxamyl, RQ values exceedthe LOC (0.05) for acute exposures to terrestrial invertebrates by se veral orders of magnitude ( Table 27).

72Table 27. RQs for acute exposures to small and large terrestrial insects from foliar applications of oxamyl at maximum use rates.

Use Small Insect RQ Large Insect RQ Apple (bearing fruit) 113 13 Celery (1 season) 267 30 Celery (3 seasons) 496 55 Citrus (bearing fruit) 267 30 Clover (for seed) 98.7 11 Cotton 150 9.6 Cucumber 245 27 Eggplant 245 27 Garlic 262 29 Melons 245 27 Onion 262 29 Non-bearing fruit 390 43 Pepper 245 27 Potato 326 36 Pumpkin 245 27 Squash 245 27 Tomato 369 41

Mammals

In order to assess the risks of oxamyl exposures to small mammals, which are prey of CRLF in terrestrial habitats, dietary-based and dose-based exposur es are modeled in TREX for a small mammal (15g) consuming short grass ( Table 16). Acute and chronic effects are estimated using the most sensitive mammalian toxicity data ( Table 21). EECs are divided by the toxicity value to estimate acute and chronic dose-based RQs as well as chronic dietary-based RQs ( Table 28). RQs representing ac ute and chronic exposures of small mammals consuming short grass on the treated field contaminated with oxamyl exceed the LOCs for all uses of oxamyl relevant to California.

73Table 28. RQs for acute and chronic exposures of small mammals consuming short grass to oxamyl from foliar applications at maximum use rates. Use Chronic RQ Acute RQ Dose-based 1 Dietary-based 2 Dose-based 3 Apple (bearing fruit) 167 19 83 Celery (1 season) 395 46 197 Celery (3 seasons) 735 85 367 Citrus (bearing fruit) 395 46 197 Clover (for seed) 146 17 73 Cotton 222 26 111 Cucumber 363 42 181 Eggplant 363 42 181 Garlic 388 45 194 Melons 363 42 181 Onion 388 45 194 Non-bearing fruit 577 67 288 Pepper 363 42 181 Potato 483 56 241 Pumpkin 363 42 181 Squash 363 42 181 Tomato 547 63 273
1 Based on dose-based EEC and oxamyl rat NOAEL = 1.25 mg/kg-bw. 2 Based on dietary-based EEC and oxamyl rat NOAEC = 25 mg/kg-diet. 3 Based on dose-based EEC and oxamyl female rat acute oral LD 50 = 2.5 mg/kg-bw.
Frogs
An additional prey item of the adult terrestrial-phase CRLF is other species of frogs ( e.g. , the Pacific tree frog). In orde r to assess risks to these prey organisms, dietary-based and dose-based exposures modeled in T-REX for a small bird (20g) consuming small invertebrates are used ( Table 26). As noted in Sec tion 5.1.2.1, acute and chronic RQs representing exposures from all uses of oxamy l that are relevant to California exceed LOCs.

5.1.2.3. Indirect Effects to CRLF via Reduction in Terrestrial Plant Community (Riparian and Upland Habitat)

Potential indirect effects to the CRLF resu lting from effects on riparian and upland vegetation are assessed using RQs from te rrestrial plant seedling emergence and vegetative vigor studies. Based on all RQs fr om soil and foliar appl ications (represented by the non-bearing fruit scenario) being below the LOC of 1.0 ( Table 29), oxamyl will have no effect on the CRLF via reduction in terrestrial plants. Example output from TerrPlant v.1.2.2 is provided in Appendix E.

74Table 29. RQs for monocots and dicots inhabiting dry and semi-aquatic areas exposed to oxamyl via spray drift and runoff.

Plant type Applicatio n rate (lbs a.i./A) Application method Drift Value (%) Spray drift RQ Dry area RQ Semiaquatic area RQ

Monocot 4.0 Soil – incorporation, infurrow, injection 0 < 0.1 < 0.1 <0.95

2.0 Foliar – ground 0.05 < 0.1 < 0.1 <0.52 1.0 Foliar – aerial 0.01 < 0.1 < 0.1 <0.24

Dicot 4.0 Soil – incorporation, infurrow, injection 0 < 0.1 < 0.1 <0.95

2.0 Foliar – ground 0.05 < 0.1 < 0.1 <0.52

1.0 Foliar – aerial 0.01 < 0.1 < 0.1 <0.24

5.1.3. Primary Constituent Elements of Designated Critical Habitat

5.1.3.1. Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Three of the four assessment endpoints for the aquatic-phase primary constituent elements (PCEs) of designated critical habitat for the CRLF are related to potential effects to aquatic and/or terrestrial plants:

• Alteration of channel/pond morphology or ge ometry and/or increase in sediment deposition within the stream channel or pond: aquatic habitat (including riparian vegetation) provides for shelter, fora ging, predator avoidance, and aquatic dispersal for juvenile and adult CRLFs.

• Alteration in water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal growth and viability of juvenile and adult CRLFs and their food source.

• Reduction and/or modification of aquatic-b ased food sources for pre-metamorphs ( e.g., algae).
RQs used to determine potential effects to these assessment endpoints are provided in Sections 5.1.1.2, 5.1.1.3, and 5.1.2.3. As described inthese sections, non e of the RQs for aquatic or riparian plants exceed the LOC.
The remaining aquatic-phase PCE is “alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their food source.” To assess the impact of oxamyl on this PCE, acute and chronic freshwater fish and invertebrate toxicity endpoints, as well endpoints for aquatic non-vascular plants, are used as measures of effects. RQs for these endpoi nts were calculated in Sections 5.1.1.1 and 5.1.1.2. As discussed in these se ctions, RQs for direct effects to CRLF are below LOCs for acute and chronic exposures. RQs for non- vascular plants, repr esenting dietary items of the tadpole stage of the CRLF are below th e LOC. Some RQs for acute exposures of aquatic invertebrates to oxamyl exceed the LOC ( Table 25).

755.1.3.2. Terrestrial-Phase (Upland Habitat and Dispersal Habitat)
Two of the four assessment endpoints for the te rrestrial-phase PCEs of designated critical habitat for the CRLF are related to poten tial effects to terrestrial plants:

• Elimination and/or disturbance of upland ha bitat; ability of hab itat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or dripline surroundi ng aquatic and riparian ha bitat that are comprised of grasslands, woodlands, and/or wetland/riparian plant species that provides the CRLF shelter, forage, and predator avoidance

• Elimination and/or disturbance of dispersa l habitat: Upland or riparian dispersal habitat within designated un its and between occupied locations within 0.7 mi of each other that allow for movement be tween sites including both natural and altered sites which do not cont ain barriers to dispersal
RQs used to determine potential effects to these assessment endpoints are provided in Section 5.1.2.3. These RQs do not exceed the LOC for plants ( Table 29).
The third terrestrial-phase PCE is “reducti on and/or modification of food sources for terrestrial phase juveniles and adults.” To assess the impact of oxamyl on this PCE, acute and chronic toxicity endpoints for frogs, mamma ls, and terrestrial invertebrates are used as measures of effects. RQs for these endpoints were calculate d in Section 5.1.2.2. RQs for these endpoints exceed the LO Cs for all uses of oxamyl ( Table 26, Table 27 and Table 28).
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food source. Direct acute and chronic RQs for terrestrial-phase CRLFs are presented in Section 5.2.1.2. RQs for these endpoints exceed the LOCs for all uses of oxamyl ( Table 26).

5.2. Risk Description

The risk description synthesizes an overall conclusion regarding th e likelihood of adverse impacts leading to an effects determination ( i.e. , “no effect,” “may affect, but not likely to adversely affect,” or “likely to advers ely affect”) for the CRLF and its designated critical habitat.
If the RQs presented in the Risk Estimati on (Section 5.1) show no direct or indirect effects for the CRLF ( i.e. , there are no LOC exceedances), and no modification to PCEs of the CRLF’s designated critic al habitat, a “no effect” determination is made, based on oxamyl’s use within the action area. However, if direct or indire ct effect LOCs are exceeded or effects may modify the PCEs of the CRLF’s critical habitat, the Agency concludes a preliminary “may affect” dete rmination for the FIFRA regulatory action regarding oxamyl.

76Because some RQs exceeded their respective LOCs, the preliminary effects determination for exposures of oxamyl to the CLRF is “May Affect” based on direct and indirect effects and effects to the CRLF’s cri tical habitat. A summary of the results of the risk estimation results are provided in Table 30 for direct and indirect effects to the CRLF and in Table 31 for the PCEs of designated critical habitat for the CRLF.

Table 30. Risk Estimation Su mmary for Oxamyl - Direct a nd Indirect Effects to CRLF.

Assessment Endpoint LOC Exceedances (Y/N) Description of Results of Risk Estimation

Aquatic Phase (eggs, larvae, tadpoles, juveniles, and adults) Direct Effects Survival, growth, and reproduction of CRLF individuals via direct effects on aquatic phases No RQs for acute and chronic exposures to fish resulting from all uses of oxamyl are below LOCs.

Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects to food supply ( i.e., freshwater invertebrates, non-vascular plants) Yes RQs are above the LOC for acute and chronic exposures to aquatic invertebrates

RQs are below the LOC for exposures to nonvascular aquatic plants, acute and chronic exposures to fish

Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects on habitat, cover, and/or primary productivity ( i.e., aquatic plant community) No RQs for exposures of non-vascular and vascular aquatic plants are below aquatic plant LOC.

Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects to riparian vegetation, required to maintain acceptable water quality and habitat in ponds and streams comprising the species’ current range. No EECs are below level where no effects to plants were observed in Tier 1 test.

Terrestrial Phase (Juveniles and adults) Direct Effects Survival, growth, and reproduction of CRLF individuals via direct effects on terrestrial phase adults and juveniles Yes Acute and chronic RQs for all uses exceed LOCs for the CRLF.

Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects on prey ( i.e., terrestrial invertebrates, small terrestrial mammals and terrestrial phase amphibians) Yes Acute and chronic RQs for te rrestrial invertebrates, small terrestrial mammals, and terrestrial phase amphibians, exceed LOCs for all uses.

Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects on habitat ( i.e., riparian vegetation) No EECs are below level where no effects to terrestrial plants were observed in Tier 1 test.

77Table 31. Risk Estimation Summary for Oxamyl – PCEs of Designated Critical Habitat for the CRLF.
Assessment Endpoint LOC Exceedances (Y/N) Description of Results of Risk Estimation
Aquatic Phase PCEs (Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat) Alteration of channel/pond morphology or geometry and/or increase in sediment deposition within the stream channel or pond: aquatic habitat (including riparian vegetation) provides for shelter, foraging, predator avoidance, and aquatic dispersal for juvenile and adult CRLFs. No RQs for non-vascular and vascular aquatic plants are below aquatic plant LOC.

EECs are below level where no effects to terrestrial plants were observed in Tier 1 test.

Alteration in water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal growth and viability of juvenile and adult CRLFs and their food source. No RQs for non-vascular and vascular aquatic plants are below aquatic plant LOC.

EECs are below level where no effects to terrestrial plants were observed in Tier 1 test.

Alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their food source. Yes RQs for acute and chronic exposures to fish resulting from all uses of oxamyl are below LOCs.
Acute RQs for some uses of oxamyl exceed the LOC for aquatic invertebrates.
RQs for non-vascular plants are below aquatic plant LOC. Reduction and/or modification of aquatic-based food sources for pre-metamorphs ( e.g. , algae) No RQs for non-vascular plants are below aquatic plant LOC.
Terrestrial Phase PCEs (Upland Habitat and Dispersal Habitat) Elimination and/or disturbance of upland habitat; ability of habitat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or dripline surrounding aquatic and riparian habitat that are comprised of grasslands, woodlands, and/or wetland/riparian plant species that provides the CRLF shelter, forage, and predator avoidance No EECs are below level where no effects to plants were observed in Tier 1 test.

Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal habitat within designated units and between occupied locations within 0.7 mi of each other that allow for movement between sites including both natural and altered sites which do not contain barriers to dispersal No EECs are below level where no effects to plants were observed in Tier 1 test.

Reduction and/or modification of food sources for terrestrial phase juveniles and adults Yes Acute and chronic RQs for terrestrial invertebrates, small terrestrial mammals, and terrestrial phase amphibi ans, exceed the LOCs for all uses. Alteration of chemical characteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food source. Yes Avian acute and chronic RQs exceed the LOCs for all uses.

78Following a “may affect” determination, additio nal information is considered to refine the potential for exposure at th e predicted levels based on th e life history characteristics ( e.g., habitat range, feeding preferences) of the CRLF. Based on the best available information, the Agency uses the refined ev aluation to distinguish those actions that “may affect, but are not likely to adversely a ffect” from those actions that are “likely to adversely affect” the CRLF and its designated critical habitat.

The criteria used to make determinations thatthe effects of an acti on are “not likely to adversely affect” the CRLF and its designated critical habitat include the following:

• Significance of Effect : Insignificant effects are those that cannot be meaningfully measured, detected, or evaluated in the c ontext of a level of effect where “take” occurs for even a single individual. “T ake” in this context means to harass or harm, defined as the following:

 Harm includes significant habitat m odification or degradation that results in death or injury to listed species by significantly impairing behavioral patterns such as br eeding, feeding, or sheltering.

 Harass is defined as actions that crea te the likelihood of injury to listed species to such an extent as to significantly disrupt normal behavior patterns which include, but are no t limited to, breeding, feeding, or sheltering.

• Likelihood of the Effect Occurring : Discountable effect s are those that are extremely unlikely to occur.

• Adverse Nature of Effect : Effects that are wholly be neficial without any adverse effects are not considered adverse.
A description of the risk and effects determination for each of the established assessment endpoints for the CRLF and its designatedcritical habitat is provided in Sections 5.2.1 through 5.2.4

.
5.2.1. Direct Effects

5.2.1.1. Aquatic-Phase CRLF
The aquatic-phase of the CRLF’s life cycle is relevant to st ages that require that CRLF individuals inhabit aquatic areas . Relevant aquatic-phase li fe stages include eggs and larvae, as well as submerged juveniles and a dults, which spend a portion of their time in water bodies that may receive runoff and spray drift containing oxamyl.
For all uses of oxamyl that ar e relevant to California, acu te and chronic exposures to CRLF in the aquatic habitat are insufficient to result in RQs exceeding the LOC. For acute exposures, the probability of individual mortality to an aquatic phase CLRF is 1 in ≥ 8.9x10 18 (assuming default slope of 4.5). While the available fathead minnow chronic toxicity endpoint was not used definitively to measure direct effects to the CRLF, the reported LOAEC value of < 1000 μg a.i./L is a source of uncertainty in making a direct

79effects determination. However, this LOAEC value would have to be reduced by a factor of 100 to result in an LOC exceedance for chronic effects (1000 / 100 = 10 μg /L). Therefore, the determination for direct eff ects to the CRLF in aquatic habitats is “No Effect” for all uses of oxamyl th at are relevant to California.

5.2.1.2. Terrestrial-Phase CRLF
RQs representing acute dose-based, acute di etary-based and chr onic dietary-based exposures to the terrestrial-phase CRLF exceed ed their respective LOCs, resulting in a “may affect” determination for all uses of oxamyl ( Table 26). These RQs were derived using the T-REX model, which estimates e xposures that are specific to food intake equations for birds. RQs generated for birds ar e used as surrogates to represent RQs for the terrestrial-phase CRLF. The RQs gene rated by T-REX are based on the maximum application rates and exceeded the LOC of 0.1 by 7 to 6500 times.
In order to explore influences of amphibian -specific food intake equations on potential dose-based and dietary-based exposures of the terrestrial phase CRLF to oxamyl, THERPS is used. Modeling with T-HERPS inco rporates the same application rates, intervals and number of applications for each use as defined for modeling using T-REX (Table 16). The dose-based and dietar y-based EECs generated by T-HERPS are provided in Table 32 and in Table 33, respectively. An example output from T-HERPS is available in Appendix I

.

80Table 32. Upper-bound Kenega Nomogram T-HERP S EECs (mg/kg-bw) for Dose-based Exposures of the CRLF and its Prey to Oxamyl.

Scenario CRLF Size (g) Small Insects Large Insects Small Herbivore Mammals 1 Small Insectivore Mammals 1 SmallTerrestrialPhase Amphibians 1.4 10.5 1.17 NA NA NA Apple (bearing fruit) 37 10.3 1.15 299 18.7 0.358 238 6.76 0.751 46.5 2.91 0.235 Celery [1 season], Citrus (bearing fruit) 1.4 24.9 2.77 NA NA NA 37 24.5 2.72 711 44.4 0.850 238 16.1 1.78 111 6.91 0.557 1.4 46.3 5.14 NA NA NA Celery [3 seasons] 37 45.5 5.05 1320 82.5 1.58 238 29.8 3.31 205 12.8 1.04 1.4 9.22 1.02 NA NA NA Clover 37 9.06 1.01 263 16.4 2.55 238 5.94 0.660 40.9 0.315 0.206 1.4 14.0 1.56 NA NA NA Cotton 37 13.8 1.53 400 25.0 0.479 238 9.04 1.01 62.2 3.89 0.314 Cucumber, Melons, 1.4 22.9 2.54 NA NA NA Pumpkin, Squash, Eggplant, Pepper 37 22.5 2.50 653 40.8 0.781 238 14.7 1.64 101 6.31 0.512 1.4 24.5 2.72 NA NA NA Garlic, Onion 37 24.0 2.67 698 43.6 0.83 238 15.8 1.75 108 6.78 0.55 1.4 36.4 4.04 NA NA NA Non-bearing fruit 37 35.8 3.97 1037 64.9 1.24 238 23.4 2.60 161 10.1 0.814 1.4 27.7 3.07 NA NA NA Potato 37 16.6 1.85 483 30.2 0.577 238 8.24 0.916 56.7 3.55 0.286 1.4 34.5 3.83 NA NA NA Tomato 37 33.9 3.77 984 61.5 1.18 238 22.2 2.47 153 9.56 0.77

1 weight of small herbivore and insectivore mammals is 35g

81Table 33. Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for Dietary-based Exposures of the CRLF and its Prey to Oxamyl.

Scenario Small Insects Large Insects Small Herbivore Mammals 1 Small Insectivore Mammals 1 SmallTerrestrialPhase Amphibians Apple (bearing fruit) 270 30.0 316 19.8 9.37 Celery [1 season], Citrus (bearing fruit) 641 71.3 751 47.0 22.3 Celery [3 seasons] 1191 132 1395 87.2 41.3
Clover 237 26.4 278 17.4 8.24
Cotton 361 40.1 423 26.5 12.5 Cucumber, Melons, Pumpkin, Squash, Eggplant, Pepper 589 65.4 690 43.1 20.4

Eggplant, Pepper 589 65.4 690 43.1 20.4 Garlic, Onion 630 70.0 738 46.1 21.9 Non-bearing fruit 937 104 1097 68.6 32.5
Potato 785 87.1 918 57.4 27.2
Tomato 888 98.6 1040 65 30.8

1 weights of small herbivore and insectivore mammals are 35g

Acute RQs
RQs are calculated for the terrestrial-phase CRL F on the basis of dose and diet. It should be noted that although dietary- based RQ values are consider ably lower than dose-based RQ values, the former do not take into acc ount that different-sized animals consume differing amounts of food and that depending on the forage item, an animal has to consume varying amounts due to differing nutrit ion levels in the food item. If dietarybased RQ values are adjusted to account fo r differential food consumption, the adjusted RQ value would likely approximate the dose-based RQ value.
Refined dose-based RQs for small sized (1.4g) CRLF consuming small and large insects exceed the acute listed species LOC (0.1) for all uses of oxamyl ( Table 34), with larger exceedances for CRLF consuming small insects. RQs range from 0.39 to 42, suggesting that small CRLF consuming small and large insects are potentially affected by acute exposures to oxamyl.

82Table 34. Dose-based RQs for 1.4g CRLF cons uming different fo od items (calculated using THERPS).
Scenario Small Insects Large Insects Apple (bearing fruit) 9.5 1.1 Celery [1 season], Citrus (bearing fruit) 9.4 1.1 Celery [3 seasons] 42 4.7 Clover 3.5 0.39 Cotton 5.3 0.59 Cucumber, Melons, Pumpkin, Squash, Eggplant, Pepper 8.7 0.96
Garlic, Onion 22 2.5 Non-bearing fruit 33 3.7 Potato 28 3.1 Tomato 31 3.5

Refined dose-based RQs for medium sized ( 37g) CRLF consuming small insects, largeinsects, small herbivore mammals, small insectivore mammals, and small terrestrialphase amphibians exceed the acute listed sp ecies LOC (0.1) for all uses of oxamyl ( Table 35). LOC exceedances for all us es of oxamyl relevant to California indicate that the medium sized CRLF could potentially be a ffected by acute exposures to oxamyl.

Table 35. Refined Dose-based RQs for 37g CRLF cons uming different food items (calculated using THERPS).

Scenario Small Insects Large Insects Small Herbivore Mammals Small Insectivore Mammals SmallTerrestrialPhase Amphibians Apple (bearing fruit) 5.7 0.64 166 10 0.20 Celery [1 season], Citrus (bearing fruit) 14 1.5 395 25 0.47 Celery [3 seasons] 25 2.8 733 46 0.88 Clover 5.0 0.56 146 9.1 0.18 Cotton 7.7 0.85 222 14 0.27 Cucumber, Melons, Pumpkin, Squash, Eggplant, Pepper 13 1.4 362 23 0.43

Garlic, Onion 13. 1.5 388 24 0.46 Non-bearing fruit 20 2.2 58 36 0.69 Potato 17 1.9 483 30 0.58 Tomato 19 2.1 547 34 0.65

Refined dose-based RQs for large sized (238g) CRLF consuming small insects, largeinsects, small herbivore mammals, small insectivore mammals, and small terrestrialphase amphibians all exceed the acute listed species LOC (0.1) for all uses of oxamyl, except for clover ( Table 36). Only for the applicati on rate specified for clover, the scenario of CRLF (238g) consuming small te rrestrial-phased amphibians did not exceed

83the LOC (0.087). Due to exceedances for almost all uses, acute exposures to oxamyl have the potential to adversely aff ect the medium sized CRLF.

Table 36. Refined Dose-based RQs for 238g CRLF co nsuming different food items (calculated using T-HERPS).

Scenario Small Insects Large Insects Small Herbivore Mammals Small Insectivore Mammals Small Terrestrial-Phase Amphibians Apple (bearing fruit) 2.8 0.32 20 1.2 0.10 Celery [1 season], Citrus (bearing fruit) 6.8 0.75 47 2.9 0.23 Celery [3 seasons] 13 1.4 86 5.4 0.43 Clover 2.5 0.28 17 1.1 0.09 Cotton 3.8 0.42 26 1.6 0.13 Cucumber, Melons, Pumpkin, Squash, Eggplant, Pepper 6.2 0.69 43 2.7 0.22

Garlic, Onion 6.6 0.74 46 2.9 0.23 Non-bearing fruit 9.9 1.1 68 4.2 0.34 Potato 8.2 0.92 57 3.6 0.29
Tomato 9.3 1.0 64 4.0 0.32

Although dietary-based RQs are generally lo wer than dose-based RQs, they follow a similar trend when compared to dose-based RQs. Refined acute dietary-based RQs for CRLFs consuming small insects and small herbivorous mammals meet or exceed the acute listed species LOC (0.1) for all uses of oxamyl ( Table 37 ). For CLRF consuming large insects in the apple (bearing) and cl over scenario, and for CRLF consuming small insectivore mammals in the scenarios of appl e (bearing fruit), celery [1 season], citrus, clover, cotton, cucumber, melons, pumpkin, s quash, eggplant, or pepper, RQs do not exceed the listed species acu te dietary-based LOC.
While the CRLF consuming small terrestrial -amphibians may only be affected by acute dietary-based exposures from oxamyl uses on apple, cherry, citrus, peach, and pear, the range of RQs from the other food items indi cates that CRLF consuming small and large insects, and small herbivore and insectivor e mammals could potentially be affected by acute dietary-based exposures to oxamyl at maximum application rates.

84Table 37. Refined Acute Dietary-based RQs for CR LF consuming different food items (calculated using T-HERPS).

Scenario Small Insects Large Insects Small Herbivore Mammals Small Insectivore Mammals Small Terrestrial-Phase Amphibians Apple (bearing fruit) 0.79 0.09 0.93 0.06 0.03 Celery [1 season], Citrus (bearing fruit) 1.9 0.21 2.2 0.14 0.07 Celery [3 seasons] 3.5 0.39 4.1 0.26 0.12 Clover 0.70 0.08 0.82 0.05 0.02 Cotton 1.1 0.12 1.3 0.08 0.04 Cucumber, Melons, Pumpkin, Squash, Eggplant, Pepper 1.7 0.19 2.0 0.13 0.06

Garlic, Onion 1.9 0.21 2.1 0.14 0.06 Non-bearing fruit 2.8 0.31 3.2 0.20 0.10 Potato 2.3 0.26 2.7 0.17 0.08 Tomato 2.6 0.29 3.1 0.19 0.09

Based on an analysis of the likelihood of i ndividual mortality cons idering the range of refined acute dose-based RQs fo r terrestrial-phase CRLFs ( Table 34 - Table 36) and a probit dose-response of 4.5 (slope), the chan ce of mortality for RQs which meet or exceed the LOC (0.1) range from 1 in 294,000 individuals to 1 in 1 individual. Considering alternate probit dos e-responses of 9 and 2, the chance of mortality for RQs which exceed the LOC range from 1 in 8 E + 18 to 1 in 1 individual, and 1 in 44 to 1 in 1 individual, respectively ( Figure 7 ). This range of RQs is re levant to all sizes of CRLF consuming small and large insects, small herbivore and insectivore mammals, and small terrestrial-phase amphibians. This range is not relevant to large CRLF consuming small terrestrial-phase amphibians modeled by the clover scenario, for which there was no LOC exceedance.
The graph in Figure 7 shows the chance of i ndividual mortality for the terrestrial-phase CRLF considering three probit dose-responses of 4.5, 9, and 2. These dose-responses converge at an RQ of 1, equivalent to a chan ce of mortality of 1 in 2 individuals. All small sized CRLFs consuming small insects ex ceed this RQ of 1, and thus exceed an individual chance of mortality of 50%, as do all medium and large sized CRLF consuming small insects, small herbivore ma mmals, and small insectivore mammals. For medium and large sized frogs consuming small herbivorous mammals, the chance of individual mortality is approximately 1 in 1 individual for all uses of oxamyl. The range of acute dose-based RQs indicate s that most applications atmaximum labeled rates pose risks of mortality to the CRLF. In explor ing lower applications rates that result in reduced risks to the CRLF and do not cause LOC exceedances, a single application rate of 0.01 lbs a.i./acre was found to be the highe st application rate that would not incur acute dosed-based LOC exceedances for any sized frog consuming all food items.

85Acute Dosed BasedChance of individual effect (1 in ...) 1.00E+19
1.00E+18
1.00E+17
1.00E+16
1.00E+15
1.00E+14
1.00E+13
1.00E+12
1.00E+11
1.00E+10
1.00E+09
1.00E+08
1.00E+07
1.00E+06
1.00E+05
1.00E+04
1.00E+03
1.00E+02
1.00E+01
1.00E+00 Series1 Series2 Series3

0.1 1 10 100 1000 RQ
Figure 7. Chance of individual mortality to terrestrial-phase CR LF when considering dose-based RQs.
Considering acute dietary-based RQs for the terrestrial phase CRLF( Table 37 ) and a probit dose-response of 4.5 (slope), the chan ce for mortality of RQs exceeding the LOC (0.1) range from 1 in 294,000 indi viduals to 1 in 1 individual (Figure 8) . A probit doseresponse of 9 indicates that the chan ce for mortality ranges from 1 in 8 E + 18 individuals to 1 in 1 individual; considering a probit dose-response of 2, the chance for mortality ranges from 1 in 44 individuals to 1 in 1.12 individuals ( Figure 8)

. The graph in Figure 8 shows the chance of i ndividual mortality for the terrestrial-phase CRLF considering three probit dose-responses of 4.5, 9, and 2. These dose-responses converge at an RQ of 1, equivalent to a chance of mortality of 1 in 2 individuals. For the CRLF consuming small terrestrial-phase amphibians for all uses of oxamyl, all RQs are below the convergence point of an RQ of 1, and thus the chance of individual mortality is less than 50%. In exploring lower applications rates that present reduced risks to the CRLF and do not cause LOC exceedances, a single application rate of 0.21 lbs a.i./acre was found to be the highest application rate that would not caus e acute dietary-based LOC exceedances for any exposure based on any food item.

86Acute Dietary BasedChance of individual effect (1 in ...) 1.00E+19
1.00E+18
1.00E+17
1.00E+16
1.00E+15
1.00E+14
1.00E+13
1.00E+12
1.00E+11
1.00E+10
1.00E+09
1.00E+08
1.00E+07
1.00E+06
1.00E+05
1.00E+04
1.00E+03
1.00E+02
1.00E+01
1.00E+00 Series1 Series2 Series3

0.1 1 10 RQ
Figure 8. Chance of individual mo rtality to terrestrial-phase CRLF when considering acute dietarybase RQs.

Sublethal effects are an indicat or of direct effects from oxa myl exposure to the terrestrialphase CRLF. Two oral acute exposure studies on mallard ducks (MRID: 94660) and bobwhite quail (MRID: 406065-11) r ecorded sublethal effects. Clinical observations of oxamyl-treated mallard ducks reported the follo wing effects: loss of coordination at 1.00 and 3.16 mg/kg-diet; ruffled feathers at 1.00 mg /kg-diet; weakness and slow movement at 3.16 mg/kg-diet; discharge from eyes and nos e at 3.16 and 10.0 mg/kg-diet; and apparent leg paralysis at 3.16, 10.0, 31.6, and 100 mg/kg-diet . Reported signs of overt toxicity in bobwhite quail occurred at test concentrations of 78 mg/kg-diet and higher, and included lethargy, ruffled appearance, depression, wing droop, loss of coordination, reduced reaction to external stimuli, shallow and rapid respirati on, lower limb weakness, head tremors, and prostrate posture. The dose of 31.6 mg/kg-diet corresponds to the EEC value of 30.0 ppm in T-HERPS, and causes anLOC exceedance with an RQ value of 3.0. This indicates that oxamyl concentrations at which some of these sublethal effects occur at (>30 mg/kg-diet), have the potential to cause effects to survival, growth and reproduction of the CRLF.

87Based on the information in this section, for a ll uses of oxamyl, the effects determination for acute effects to the terrestrial phase CRLF is “likely to adversely affect (LAA)” based on potential mortality thr ough consumption of oxamyl-contaminated food items.

Chronic RQs
Refined chronic dietary-based RQs for CRLFs consuming insects and mammals using the T-HERPS model exceed the chronic listed speci es LOC (1.0) for all uses of oxamyl. The chronic listed species LOC is exceeded for CRLF consuming terrestrial-phase amphibians for every use except clover ( Table 38 )

.
Table 38. Revised Chronic Dietary-based RQs for CRLF consuming diff erent food items (RQs calculated using T-HERPS).

Scenario Small Insects Large Insects Small Herbivore Mammals Small Insectivore Mammals Small Terrestrial-Phase Amphibians Apple (bearing fruit) 27 3.0 32 2.0 0.94 Celery [1 season], Citrus (bearing fruit) 64.1 7.13 75.1 4.70 2.23 Celery [3 seasons] 119 13 140 8.7 4.13 Clover 23.7 2.64 27.8 1.74 0.824 Cotton 36.1 4.02 42.3 2.65 1.25 Cucumber, Melons, Pumpkin, Squash, Eggplant, Pepper 58.9 6.54 69.0 4.31 2.04

Garlic, Onion 63.0 7.00 73.8 4.61 2.19 Non-bearing fruit 93.7 10.4 110 6.86 3.25 Potato 78.3 8.71 91.8 5.74 2.72 Tomato 88.8 9.86 104 6.50 3.08

In the available chronic study where Northernbobwhite quail were exposed to oxamyl, the NOAEC was 10 mg/kg-diet, and the LOAEC was 50 mg/kg-diet, ba sed on effects to egg production and egg fertility. Comparison ofthe LOAEC directly to chronic dietarybased EECs for CRLF consuming small insect s and small herbivore mammals indicate that EECs for all uses are sufficient to exceed the concentration where reproductive effects were observed in the laboratory. For CRLF consuming large insects, the majority of the oxamyl uses have EECs which are insuffi cient to exceed the LOAEC. Therefore, for some CRLF feeding categories, oxamyl EE Cs are at levels where reproductive effects were observed in birds, which serve as surrogates for the CRLF.
In exploring lower applications rates that present reduced risks to the CRLF and do not cause LOC exceedances, a single application rate of 2.13 lbs a.i./acre was found to be the highest application rate that would not cause chronic dietary-based LOC exceedances for any exposure based on any food item.

88Based on this information, the effects determination for chronic effects from all oxamyl uses to the terrestrial-phase CRLF is “LAA” based on potential for effects to reproduction.

5.2.2. Indirect Effects (via Reductions in Prey Base)

5.2.2.1. Algae (non-vascular plants)

As discussed in Section 2.5.3, the diet of CRL F tadpoles is composed primarily of nonvascular aquatic plants ( i.e. , algae and diatoms) and detritu s. For all uses of oxamyl relevant to California, exposur es in the aquatic habitat to non-vascular aquatic plants areinsufficient to result in RQs exceeding the LOC. Therefore, there is no effect to tadpolestage CRLFs via effects on aquatic non-vascul ar plants from exposures resulting from any use of oxamyl.

5.2.2.2. Aquatic Invertebrates
RQ values representing acute exposures to aqua tic invertebrates indicate that several uses of oxamyl can potentially result in effects to invertebrates. Therefore, indirect effects are may affect CRLF juveniles and adults, through decr eases in prey base. The results of an analysis of the likelihood of individual mortality using acute RQs for aquatic invertebrates and a probit dos e-response of 4.5 (based on default) are displayed in Table 39

. Based on this analysis, all uses of oxamyl result in ≤ 0.34% chance of effects to an individual aquatic invertebra te. Therefore, although acute oxamyl exposures may affect individual CRLF through indirect effects cause d by effects to aquati c invertebrates, the impact of these effects on the CRLF is discountable for all uses. Therefore, effects to aquatic invertebrates resulting from acute expo sures are not likely to adversely affect the CRLF.
For the majority of uses of oxamyl relevantto California, chronic exposures in the aquatic habitat to aquatic invertebrates ar e insufficient to result in RQs exceeding the LOC. Chronic exposures for the uses of garlic and celery resulted in RQs exceeding the LOC. The chronic RQs are based on a deri ved chronic NOAEC for aquatic invertebrate (0.012 mg a.i./L) from an ACR. If the ACR method was used to derive an adjusted LOAEC for chironomids, that value would be 0.027 mg a.i./L. This adjusted LOAEC is above the chronic EECs for aquatic invert ebrates (max EEC = 0.018 mg a.i./L). In addition, EECs are below the available NOAEC value for daphnids (NOAEC=0.027 mg a.i./L and LOAEC=0.050 mg a.i./L, MRID : 450678-01), suggesting that even though sensitive species of aquatic invertebrates may be affect ed by chronic exposures of oxamyl, less sensitive species, such as daphnids are unlikely to be affected. Given that the CRLF is an opportunistic feeder, the im pact of effects to sensitive aquatic invertebrates from chronic exposures on the CRLF is discountable. Therefore, although chronic oxamyl exposures may affect indi vidual CRLF through indirect effects caused by effects to aquatic invertebrate s, the impact of these effect s on the CRLF is discountable for all uses. Therefore, effects to aquatic i nvertebrates resulting from chronic exposures are not likely to adversely affect the CRLF.

89Table 39. Acute RQs and corresponding likelihood of indivi dual effects and chro nic RQs for aquatic invertebrates exposed to oxamyl.

Use Indirect Effects Acute RQ 1 Individual Chance of Effects 3 Indirect Effects Chronic RQ 4 Celery (3 seasons) 0.25 2 0.34% 1.5 5 Celery (1 season) 0.17 2 * 0.03% 1.1 5
Garlic 0.19 2 * 0.06% 1.1 5

Tomato 0.16 2 0.02% 0.7 Non-bearing fruit 0.12 2 <0.01% 0.7 Pepper 0.10 2 <0.01% 0.6
Cotton 0.11 2 <0.01% 0.6 Citrus (bearing fruit) 0.07 2 <0.01% 0.3
Potato 0.04 <0.01% 0.4 Clover 0.04 <0.01% 0.3 Onion 0.04 <0.01% 0.4 Cucumber, melons, pumpkin, squash 0.04 <0.01% 0.2 Apple (bearing fruit) 0.02 <0.01% 0.1 Eggplant 0.02 <0.01% 0.1

1 Acute RQ = use-specific 1-in-10- year peak EEC / acute freshwater invertebrate endpoint (EC 50 = 180 μg/L). 2 Exceeds listed species LOC fo r acute exposures (0.05). 3 Calculated using default slope = 4.5. 4 Chronic RQ = use-specific 1-in-1 0-year 21-day-mean EEC / chronic freshwater ACR endpoint (NOAEC = 12 μg/L). 5 Exceeds listed species LOC for chronic exposures (1.0).

5.2.2.3. Fish and Aquatic-phase Frogs
For all uses of oxamyl acute and chronic exposures in the aquatic habitat to fish and aquatic-phase frogs (serving as prey to adult CRLF) are insufficient to result in RQs exceeding the LOC. Therefore, indirect e ffects of oxamyl by reductions in this food source of the adult CRLF are not expected ba sed on the animal’s diet during this life stage for all uses of oxamyl. Therefore, th ere is no effect to a quatic-phase CRLFs via effects on fish and aquatic-phase amphibians fr om aquatic exposures arising from any use of oxamyl that is relevant to California.

5.2.2.4. Terrestrial Invertebrates
When the terrestrial-phase CRLF reaches juveni le and adult stages, its diet is mainly composed of terrestrial invertebrates. RQ s representing acute expos ures of terrestrial invertebrates are represented by oxamyl exposur es to small and large terrestrial insects located on the treatment field. Resulting RQ values exceed the acute LOC (0.05) by several orders of magnitude, with values ranging 9.57-390 ( Table 27).

90An analysis of the likelihood of individual mortality indicates that an RQ of 5 or greater results in a >99.9% probability of mortality to an individual terre strial invertebrate located on a field treated with oxamyl (assu ming a default probit dose-response value of 4.5) Table 25

. Since all RQs for terr estrial invertebrates ar e >5, the likelihood of individual mortality to a terrestrial invertebrate on a field treated with any use of oxamyl (relevant to Calif ornia) is >99.9%.
Based on the lowest acute toxicity value for terrestrial invertebrates (LD 50 = 2.4 ppm), exposure concentrations <0.12 ppm would be be low levels of concern for this taxa. For large and small insects, this exposure would be expected at single applications of <0.008 and <0.0009 lbs a.i./A, respectively. These exposure concentrati ons are well below maximum single application rates allowed on pr oduct labels, as well as several orders of magnitude below estimated average single ap plication rates of oxamyl in California, which range 0.43-10 lbs a.i./A ( Table 7).
A spray drift exposure analysis (using AgDR IFT) indicates that oxamyl concentrations resulting from a single aerial application of 1 lb a.i./A would be at levels sufficient to exceed the LOC for large and small terrestrial insects at <990 feet from the edge of the treated field (assuming the default ASAE fine to medium droplet size distribution). A likelihood of individual mortality analysis (using IEC v. 1.1) indicates that >10% chance of mortality to individual large insects can o ccur <120 ft from the edge of the field and >22% chance of mortality to individual sma ll insects can occur <950 feet from the edge of the field ( Figure 9).

100 Large insect Small insect 90

80

70

60

50

40

30

20

10

0 0 100 200 300 400 500 600 700 800 900 1000 Distance from edge of field (ft)

Figure 9. Likelihood of in dividual mortality to terrestrial inve rtebrates at different distances from the edge of a field treated with a single aerial application of oxamyl at 1 lb a.i./A.Liklihood of individual mortality (%)

91A spray drift exposure analysis (using AgDR IFT) indicates that oxamyl concentrations resulting from a single ground application of 2 lb a.i./A would be at levels sufficient to exceed the LOC for large and small terrestrial insects at 209 and <990 feet from the edge of the treated field (assuming low boom, ASAE very fine to fine droplet size distribution). A likelihood of individual mo rtality analysis (usi ng IEC v. 1.1) indicates that >10% chance of mortality to individual large and small insects can occur within approximately 20 ft and 250 feet, respec tively, from the edge of the field ( Figure 10).

100.00 Large insect Small insect 90.00

80.00

70.00

60.00

50.00

40.00

30.00

20.00

10.00

0.00 0 100 200 300 400 500 600 700 800 900 1000 Distance from edge of field (ft)

Figure 10. Likelihood of individual mortality to terrestrial inve rtebrates at different distances from the edge of a field treated with a single gr ound application of oxamyl at 2 lb a.i./A.
Therefore, it is possible that there will be in direct effects to terrestrial-phase CRLFs via effects on terrestrial insects from oxamyl e xposures arising from any use of oxamyl that is relevant to California. The extent of ef fects is unknown because a range of sensitivities of invertebrates is expected to exist.

5.2.2.5. Mammals
Life history data for terres trial-phase CRLFs indicate that large adult frogs consume terrestrial mammals, including mice. RQs re presenting acute and chronic exposures of terrestrial mammals are represented by oxa myl exposures to animals located on the treatment field.

Acute ExposuresLiklihood of individual mortality (%)

92Acute dose-based RQ for small mammals consuming short grass exceed the acute LOC (0.1) by several orders of magnitude for all uses of oxamyl, with values ranging 73.2-288 ( Table 28). Single applications of 1 or 2 lb s a.i./A of oxamyl result in acute, dose-based RQs which are sufficient to exceed the LO C for small mammals consuming other food items, including tall grass, broadleaf plants, small insects, fruits, pods, large insects and seeds ( Table 40).

Table 40. Acute, dose-based RQ values for small mammals (15 g) exposed to oxamyl through consumption of food items on the treated field. RQ s correspond to single applications of oxamyl at 1 lb a.i./A and 2 lb a.i./A. Diet 1 lb a.i./A 2 lb a.i./A
Short Grass 41.64 83.29 Tall Grass 19.09 38.17 Broadleaf plants/small insects 23.43 46.85 Fruits/pods/large insects 2.60 5.21 Seeds 0.58 1.16
An analysis of the likelihood of individual mortality indicates that an RQ of 3 or greater results in a >99.9% probability of mortalit y to an individual mammal located on a field treated with oxamyl (assuming a probit dose-response value of 9.3 and 18.0, MRID 00063011) Table 25

. Since all acute, dose-based RQs for small mammals consuming short grass are >3, the likelihood of individual mortality to a terres trial mammal on a field treated with any use of oxamyl (relevant to California) is >99.9%. In addition, the likelihood of individual mortal ity to mammals consuming ot her food items, besides short grass, is also >99.9%, based on RQs>3 ( Table 40).
Based on the lowest acute toxicity value for mammals (LD 50 = 2.5 mg/kg-bw), exposure concentrations <0.0025 lbs a.i./A would be be low levels of concern for small mammals. This exposure concentration is below ma ximum single application rates allowed on product labels, as well as se veral orders of magnitude be low estimated average single application rates of oxamyl in Califo rnia, which range 0.43-1.34 lb a.i./A ( Table 7). A spray drift exposure analysis (using AgDRIF T) indicates that oxamyl concentrations resulting from a single aerial application of 1 lb a.i./A would be at levels sufficient to exceed the LOC for small mammals at >990 feet from the edge of the treated field. Exposure concentrations up to 801 feet fr om the edge of a field treated by ground methods with 2 lb a.i./A oxamyl would be at levels sufficient to exceed the LOC for small mammals ( Table 41).

93Table 41. Concentration where LOC is not exceeded for small mammal s (15 g) receiving acute, dosebased exposures of oxamyl throug h consumption of contaminated f ood items and distance from edge of treatment field where LOC is not exceeded.

Diet Concentration (lb a.i./A) where acute LOC is not exceeded* Distance (ft) from edge of field where LOC is not exceeded Single aerial application of 1 lb a.i./A Single ground application of 2 lb a.i./A Short Grass 0.0025 >990** 801 Tall Grass 0.0050 >990** 423 Broadleaf plants/small insects 0.0044 >990** 479 Fruits/pods/large insects 0.0400 236 46 Seeds 0.1700 52 13

* Based on the lowest acute toxicity value for mammals (LD 50 = 2.5 mg/kg-bw) and LOC of 0.1 **The limit of AgDRIFT’s predictability is 990 ft from the edge of the treated field.
The T-REX model is useful for assessing expos ures of terrestrial animals to pesticides applied to foliar surfaces of crops. The model cannot be used to assess pesticide exposures to terrestrial animals resulting fr om applications invol ving soil incorporation. In order to explore the potential exposures of mammals to oxamyl following applications involving ground application, a simple fugac ity approach was employed to estimate oxamyl concentrations in earthworms and s ubsequent exposures to mammals consuming earthworms. This approach is explained in de tail in Appendix K. If it is assumed that the small mammal being assessed eats only earthworms on the day of treatment (meaning that there would be no degradation of oxa myl), the acute dose of oxamyl to a 20 g mammal would be 0.024 to 0.078 mg/kg-bw. This range of exposure values is 2 orders of magnitude below the LD 50 values for rats (2.5-3.1 mg/kg-bw; MRID 00063011) exposed to oxamyl. The likelihood of individual mo rtality to a small ma mmal consuming only earthworms from a treated field would be <0.01%.
Chronic Exposures

Dose-based chronic RQ values for small ma mmals (15 g) consuming short grass exceed the chronic LOC (1.0) by several orders of magnitude, with values ranging 146-577. Dietary-based chronic RQ values also exceed the chronic LOC (1.0) by several orders of magnitude, with values ranging 16.8-66.6 ( Table 28). Single applications of 1 or 2 lbs a.i./A of oxamyl result in chronic, dose-bas ed and dietary-based RQ s which are sufficient to exceed the LOC for small mammals consuming other food items, including tall grass, broadleaf plants, small insects, fruits, pods, large insects and seeds ( Table 42 and Table 43).

Chronic RQ values are derived with available NOAEC data. If chronic, dose-based and dietary-based EECs ( Table 16) were compared to the LOAEC and LOAEL values for mammals exposed to oxamyl, the EECs exceed these levels (75 mg/kg-diet) where effects to mammals were observed in the labo ratory. Observed effects include decreased body weight during lact ation (MRID 416608-01).

94Table 42. Chronic, dose-based RQ values for small mammals (15 g) exposed to oxamyl through consumption of food items on the treated field. RQ s correspond to single applications of oxamyl at 1 lb a.i./A and 2 lb a.i./A. Diet 1 lb a.i./A 2 lb a.i./A
Short Grass 83.29 166.58 Tall Grass 38.17 76.35 Broadleaf plants/small insects 46.85 93.70 Fruits/pods/large insects 5.21 10.41 Seeds 1.16 2.31

Table 43. Chronic, dietary-based RQ values for small mammals (15 g) exposed to oxamyl through consumption of food items on the treated field. RQ s correspond to single applications of oxamyl at 1 lb a.i./A and 2 lb a.i./A. Diet 1 lb a.i./A 2 lb a.i./A
Short Grass 9.60 19.20 Tall Grass 4.40 8.80 Broadleaf plants/small insects 5.40 10.80 Fruits/pods/large insects 0.60 1.20 Seeds 0.60 1.20

Summary
Based on this information, there are potential indirect effects to te rrestrial-phase CRLFs via effects on small mammals from oxamyl exposures arising from any use of oxamyl that is relevant to California.

5.2.2.6. Terrestrial-phase Amphibians
In order to explore influen ces of amphibian-specific food intake equations on potential dose-based and dietary-based exposures of am phibians (prey of CR LF) to oxamyl, the THERPS model is used. The Pacific tree frog is used to represent the amphibian prey species. The weight of the animal is assumed to be 2.3 g, and its diet is assumed to be composed of small and large insects. For frogs consuming small and large insects, the acute LOC (0.1) is exceeded for all uses of oxamyl ( Table 44).
Based on an analysis of the likelihood of individual mortality using acute dose-based RQs for terrestrial phase frogs and a defau lt probit dose-response of 4.5, the likelihood of individual mortality for each use is available in Table 44

. Based on this analysis all of uses of oxamyl result in >10% chance of e ffects to an individual terrestrial phase frog consuming small insects. The majority of us es of oxamyl also result in >10% chance of effects to an individual terrestrial phase frog consuming large insects. Based on acute dose-based RQs and individual e ffects chance for terrestrial- phase frogs (prey of CRLF) which consume small insects, there is potential for effects to this taxa due to oxamyl exposures from all uses.

95Table 44. Acute dose-based RQs and associated like lihood of individual eff ects to terrestrial-phase frogs (prey) due to oxamyl exposures. Frogs consuming Small Insects Frogs consuming Large Insects Use RQ Likelihood of individual acute effect (%) RQ Likelihood of individual acute effect (%) Apple (bearing fruit) 2.97 98 0.33 2 Celery [1 season], Citrus (bearing fruit) 7.05 ~100 0.78 31 Celery [3 seasons] 13.1 ~100 1.45 77 Clover 2.61 97 0.29 1 Cotton 3.97 ~100 0.44 5 Cucumber, Melons, Pumpkin, Squash, Eggplant, Pepper 6.47 ~100 0.72 26

Garlic, Onion 6.92 ~100 0.77 30 Non-bearing fruit 10.3 ~100 1.14 60 Potato 8.61 ~100 0.96 47 Tomato 9.75 ~100 1.08 56
Acute dietary-based RQs for the CRLF, which do not account for the weight of the animal being assessed, can also be used to assess risks to the terrestrial frog prey ( Table 37). For frogs which consume small insects, RQs exceed the acute LOC (0.1) for all oxamyl uses. For frogs which consume large in sects, the acute LOC is exceeded for all uses of oxamyl, with the ex ception of oxamyl use on clover.
Chronic dietary-based RQs fo r the CRLF, which do not account for the weight of the animal being assessed, can also be used to assess risks to the terrestrial frog prey ( Table 38). Refined dietary-based RQs indicate that, for all oxamyl us es, there is potential for chronic effects to terrestrial frogs feeding on small and large insects. Chronic RQs are exceeded by factors ranging 2.6X to 94X.
Summary
Based on this information, there are potential indirect effects to te rrestrial-phase CRLFs via effects on small terrestrial phase frogs fr om oxamyl exposures arising from any use of oxamyl that is relevant to California.

5.2.3. Indirect Effects (via Habitat Effects)

5.2.3.1 Aquatic Plants (Vascular and Non-vascular)
Aquatic plants serve several important functi ons in aquatic ecosystems. Non-vascular aquatic plants are primary producers and pr ovide the autochthonous energy base for aquatic ecosystems. Vascular plants provide structure as attachment sites and refugia for many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In addition, vascular plants al so provide primary productivity and oxygen to the aquatic ecosystem. Rooted plants help reduce se diment loading and provide stability to

96nearshore areas and lower streambanks. In a ddition, vascular aquatic plants are important as attachment sites for egg masses of CRLFs.

Potential indirect effects to the CRLF ba sed on impacts to habitat and/or primary production were assessed using RQs from fres hwater aquatic vascul ar and non-vascular plant data. RQs for both aqua tic vascular and non-vascularplants are below the LOC, indicating that exposures of oxamyl to aquatic pl ants will not result in effects to plants. In addition exposures of oxamyl to riparian vege tation are below levels where no effects to terrestrial plants were observed in greenhous e studies. Therefore, the determination for indirect effects to the CRLF caused by effect s to aquatic plants re sulting from use of oxamyl is “No Effect.”

5.2.3.2. Terrestrial Plants
Terrestrial plants serve several important ha bitat-related functions for the CRLF. In addition to providing habitat and cover for inve rtebrate and vertebrate prey items of the CRLF, terrestrial vegetation also provides sh elter for the CRLF and cover from predators while foraging. Terrestrial plan ts also provide energy to th e terrestrial ecosystem through primary production. Upland vegetation incl uding grassland and woodlands provides cover during dispersal. Riparian vegetation he lps to maintain the integrity of aquatic systems by providing bank and thermal stability, serving as a buffer to filter out sediment, nutrients, and contaminants before they r each the watershed, and serving as an energy

source.

Potential indirect effects to the CRLF ba sed on impacts to habitat and/or primary production were assessed using RQs from m onocot and dicot plant data. RQs for both monocots and dicots were below the Agency’s LOC, indicating that exposures of oxamyl to terrestrial plants will not result in effects to plants. While effects to height and weight were observed in dicots in the vegetative vigor and seedling emergence studies, these effects were ≤ 25% relative to the control. Based on the supplemental nature of the vegetative vigor study, the ≤ 25% effects relative to the controls, and no RQ exceedances, the determination for indirect effects to th e CRLF caused by effects to terrestrial plants resulting from use of oxamyl is “No Effect.”

5.2.4. Modification to Designated Critical Habitat

5.2.4.1. Aquatic-Phase PCEs
Three of the four assessment endpoints for the aquatic-phase primary constituent elements (PCEs) of designated critical habitat for the CRLF are related to potential effects to aquatic and/or terrestrial plants:

• Alteration of channel/pond morphology or ge ometry and/or increase in sediment deposition within the stream channel or pond: aquatic habitat (including riparian

97vegetation) provides for shelter, fora ging, predator avoidance, and aquatic dispersal for juvenile and adult CRLFs.

• Alteration in water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal growth and viability of juvenile and adult CRLFs and their food source.

• Reduction and/or modification of aquatic-b ased food sources for pre-metamorphs ( e.g., algae).
Based on the risk estimation for potential effect s to aquatic and terres trial plants provided in Sections 5.1.1.2, 5.1.1.3, and 5.1.2.3 ( i.e. , a lack of LOC ex ceedances by RQs) o xamyl is not likely to affect aquatic-phase PCEs of designated habitat related to effects on aquatic and/or terrestrial plants.
The remaining aquatic-phase PCE is “alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their food source.” Other than impacts to algae as food items for tadpoles (discussed above), this PCE is assessed by considering direct and indirect effects to the aquatic-phase CRLF via acute and chronic freshwater fish and invertebrate toxicity endpo ints as measures of effects. RQs for these endpoints were calculated in Sections 5.1.1.1 and 5.1.1.2. As discussed in these sections, RQs for direct effects to CRLF are below LO Cs for acute and chronic exposures. RQs for non-vascular plants, repres enting dietary items of the ta dpole stage of the CRLF are below the LOC. Although some RQs for acute exposures of aquatic invertebrates to oxamyl exceed the LOC, these effects are considered discountable. Therefore, oxamyl may affect, but is not likely to adversely affect aquatic- phase PCEs of designated habitat related to effects of alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their food source.

5.2.4.2. Terrestrial-Phase PCEs
Two of the four assessment endpoints for the te rrestrial-phase PCEs of designated critical habitat for the CRLF are related to poten tial effects to terrestrial plants:

• Elimination and/or disturbance of upland ha bitat; ability of hab itat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or dripline surroundi ng aquatic and riparian ha bitat that are comprised of grasslands, woodlands, and/or wetland/riparian plant species that provides the CRLF shelter, forage, and predator avoidance

• Elimination and/or disturbance of dispersa l habitat: Upland or riparian dispersal habitat within designated un its and between occupied locations within 0.7 mi of each other that allow for movement be tween sites including both natural and altered sites which do not cont ain barriers to dispersal
Based on the risk estimation for terrestrial-pha se PCEs of designate d habitat related to potential effects on terrestrial pl ants is provided in Section 5.1.2.3, oxamyl is not likely to affect terrestrial-phase PCEs of designat ed habitat related to effects on terrestrial plants.

98The third terrestrial-phase PCE is “reducti on and/or modification of food sources for terrestrial phase juveniles and adults.” To assess the impact of oxamyl on this PCE, acute and chronic toxicity endpoints for birds, mammals, and terrestrial invertebrates are used as measures of effects. RQs for thes e endpoints were calculated in Section 5.1.2.2. Based on RQ exceedances for acute and chronic exposure to frogs, mammals, and terrestrial invertebrates, oxamyl is likely to result in habitat modification based on potential impacts to the th ird terrestrial-phase PCE

. The fourth terrestrial-phase PC is based on alteration of chemi cal characteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food source. Direct acute and chronic RQs for terrestrial-phase CRLFs are presented in Section 5.2.1.2. Based on RQ exceedances for acute and chronic exposure to birds, mammals, and terrestrial invertebrates, oxamyl is likely to result in habitat modification based on potential impact s to the fourth terrestrial-phase PCEs

.

5.3. Uncertainties

5.3.1. Exposure Assessment Uncertainties
From 1994 to 2006 oxamyl was not used on cherries, based on the CDPR PUR data. While the lack of use indicates that oxamyl mo st likely was not used in the past decade on cherries, it is still a registered crop and has th e potential to be used in the future. Thus, risk to CRLF from use on cherries is considered in this assessment.
In contrast, U.S. Department of Agricultur e census data confirm that tobacco has not been grown in California from at least th e 1992 report, forward (USDA 2008) and it is unlikely that tobacco agriculture will be initiated in California in the future. Therefore, use of oxamyl on tobacco was not quantitatively evaluated for exposure in this assessment.

5.3.1.1. Maximum Use Scenario
The screening-level risk assessment focuses on characterizing poten tial ecological risks resulting from a maximum use scenario, which is determined from labeled statements of maximum application rate and number of appli cations with the shortest time interval between applications. The frequency at whic h actual uses approach this maximum use scenario may be dependant on pest resistance, timing of applications, cultural practices, and market forces.

5.3.1.2. Aquatic Exposure Modeling of Oxamyl
The standard ecological water body scenario (EXAMS pond) used to calculate potential aquatic exposure to pesticides is intended to represent conservative estimates, and to avoid underestimations of the actual exposure. The standard scenario consists of application to a 10-hectare field bordering a 1-hectare, 2-meter deep (20,000 m 3 ) pond

99with no outlet. Exposure estimates generated using the EXAMS pond are intended to represent a wide variety of vulnerable water bodies that occur at the top of watersheds including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural ponds, and intermittent and lower order streams. As a group, there are factors that make these water bodies more or less vulnerable than the EXAMS pond. Static water bodies that have larger ratios of pesticide-treate d drainage area to water body volume would be expected to have higher peak EECs than the EXAMS pond. These water bodies will be either smaller in size or have larger drainage areas. Sm aller water bodies have limited storage capacity and thus may overflow and carry pesticide in the discharge, whereas the EXAMS pond has no discharge. As waters hed size increases beyond 10-hectares, it becomes increasingly unlikely that the entire watershed is planted w ith a single crop that is all treated simultaneously with the pesticid e. Headwater streams can also have peak concentrations higher than the EXAMS pond, but they likely persist for only short periods of time and are then car ried and dissipated downstream.
The Agency acknowledges that there are so me unique aquatic habitats that are not accurately captured by this modeling scenario and modeling results may, therefore, under- or over-estimate exposure, depending on a number of variables. For example, aquatic-phase CRLFs may inhabit water bodies of different size a nd depth and/or are located adjacent to larger orsmaller drainage areas thanthe EXAMS pond. The Agency does not currently have sufficient information regarding the hydrology of these aquatic habitats to develop a specific alternate scenar io for the CRLF. CRLFs prefer habitat with perennial (present year-round) or near-perennial water and do not frequently inhabit vernal (temporary) pools because conditions in these habitats are generally not suitable (Hayes and Jennings 1988). Therefore, the EXAMS pond is assumed to be representative of exposure to aquatic-phase CRLFs. In addi tion, the Services agree that the existing EXAMS pond represents the best currently available approach for estimating aquatic exposure to pesticid es (USFWS/NMFS 2004).
Furthermore, if aquatic-phase CRLFs inhabit acidic water bodies that are exposed to oxamyl, the duration of exposure may be longe r than was estimated using the standard aquatic modeling guidance, as oxamyl is relativel y stable to hydrolysis at pH 5. In this case, aquatic invertebrates usedas prey may be at higher ri sk to chronic exposure and at slightly higher risk to acute exposure than was assessed. Although this is an uncertainty in the assessment, the increase in risk is rela tively small and potential indirect effects to the aquatic-phase CRLF due to effects of oxamyl to aquatic invertebrates are not expected.
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone Model is a process or “simulation” model that calculates what happens to a pesticide in an agricultural field on a day-to-day basis. It considers factors such as rainfall and plant transpiration of water, as well as how and when the pesticide is applied. It has two major components: hydrology and chemical transport. Water movement is simulated by the use of generalized soil parameters, including fi eld capacity, wilting point, and saturation water content. The chemical transport com ponent can simulate pesticide application on

100the soil or on the plant foliage. Dissolved, adsorbed, and vapor-phase concentrations in the soil are estimated by simultaneously cons idering the processes of pesticide uptake by plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection, dispersion, and retardation.

Uncertainties associated with each of thes e individual components add to the overall uncertainty of the modeled concentrations. Also, model inputs from the environmental fate degradation studies are chosen to re present the upper confid ence bound on the mean values that are not expected to be exceededin the environment approximately 90 percent of the time. However, the model input for the aerobic soil metabol ism half-life remains uncertain due to an uncharacteristically high value in the data. Mobility input values are chosen to be representative of conditions in the environmen t. The natural variation in soils adds to the uncertainty of modeled valu es. Factors such as application date, crop emergence date, and canopy cover can also aff ect estimated concentrations, adding to the uncertainty of modeled values. Factors with in the ambient environment such as soil temperatures, sunlight intensity, antecedent soil moisture, and surface water temperatures can cause actual aquatic concentrations to differ for the modeled values.
Unlike spray drift, tools are currently not av ailable to evaluate th e effectiveness of a vegetative setback on runoff and loadings. Th e effectiveness of vegetative setbacks is highly dependent on the condition of the vegetative strip. For example, a wellestablished, healthy vegetative setback can be a very eff ective means of reducing runoff and erosion from agricultural fields. Alternatively, a setbac k of poor vegetative quality or a setback that is channelized can be ine ffective at reducing loadings. Until such time as a quantitative method to estimate the effect of vegetative setbacks on various conditions on pesticide loadings becomes available, the aquatic exposure predictions are likely to overestimate exposure where h ealthy vegetative setbacks exist and underestimate exposure where poorly developed, channelized, or bare setbacks exist.

In order to account for uncertainties associ ated with modeling, available monitoring data were compared to PRZM/EXAMS estimates of peak EECs for the different uses. As discussed above, several data values we re available from NAWQA for oxamyl concentrations measured in surface waters receiving runoff from agricultural areas. The specific use patterns ( e.g. application rates and timing, crops) associated with the agricultural areas are unknown, however, they are assumed to be representative of potential oxamyl use areas.

5.3.1.3. Action Area Uncertainties
An example of an important simplifying assumption that may require future refinement is the assumption of uniform runoff characteri stics throughout a lands cape. It is well documented that runoff characteristics ar e highly non-uniform and anisotropic, and become increasingly so as the area under consideration becomes larger. The assumption made for estimating the aquatic action area (b ased on predicted in-stream dilution) was that the entire landscape exhi bited runoff properties identical to those commonly found in agricultural lands in this re gion. However, considering the vastly different runoff

101characteristics of: a) undeveloped (especially forested) areas, which exhibit the least amount of surface runoff but the greatest amount of ground water recharge; b) suburban/residential areas, which are do minated by the relationship between impermeable surfaces (roads, lots) and grasse d/other areas (lawns) plus local drainage management; c) urban areas, that are do minated by managed storm drainage and impermeable surfaces; and d) agricultural areas dominated by Hortonian and focused runoff (especially with row crops), a re fined assessment should incorporate these differences for modeled stream flow ge neration. As the z one around the immediate (application) target area expands, there will be greater variability in the landscape; in the context of a risk assessment, the runoff potential that is assumed for the expanding area will be a crucial variable (since dilution at th e outflow point is determined by the size of the expanding area). Thus, it important to know at least some approximate estimate of types of land use within that region. R unoff from forested areas ranges from 45 – 2,700% less than from agricultural areas; in mo st studies, runoff was 2.5 to 7 times higher in agricultural areas ( e.g. , Okisaka et al., 1997; Karvonen et al., 1999; McDonald et al., 2002; Phuong and van Dam 2002). Differe nces in runoff potential between urban/suburban areas and agricultural areas ar e generally less than between agricultural and forested areas. In terms of likely runoff potential (other variables – such as topography and rainfall – being equal), the relationship is ge nerally as follows (going from lowest to highest runoff potential):
Three-tiered forest < agroforestry < suburban < row-crop agriculture < urban.

There are, however, other uncertainties that should serve to counter act the effects of the aforementioned issue. For example, the di lution model considers that 100% of the agricultural area has the chemical applied, which is almost certainly a gross overestimation. Thus, there will be assumed chemic al contributions from agricultural areas that will actually be contributing only runoff water (dilutant); so some contributions to total contaminant load will really serve to lessen rather than increase aquatic concentrations. In light of these (and other) confounding factors, Agency believes that this model gives us the best available estimates under current circumstances.

5.3.1.4. Usage Uncertainties
County-level usage data were obtained from California’s Department of Pesticide Regulation Pesticide Use Reporti ng (CDPR PUR) database. F our years of data (2002 – 2005) were included in this analysis b ecause statistical methodology for identifying outliers, in terms of area treated and pounds applied, was provided by CDPR for these years only. No methodology for removing out liers was provided by CDPR for 2001 and earlier pesticide data; therefore, this inform ation was not included in the analysis because it may misrepresent actual usage patterns. CDPR PUR documentation indicates that errors in the data may include the following: a misplaced decimal; incorrect measures, area treated, or units; and reports of diluted pesticide c oncentrations. In addition, it is possible that the data may contain reports fo r pesticide uses that have been cancelled. The CPDR PUR data does not include home owner applied pesticides; therefore, residential uses are not likely to be reported. As with all pesticid e usage data, there may

102be instances of misuse and misreporting. The Agency made use of the most current, verifiable information; in cases where ther e were discrepancies, the most conservative information was used.

5.3.1.5. Terrestrial Exposure Modeling of Oxamyl
The Agency relies on the work of Fletcher et al. (1994) for setting the assumed pesticide residues in wildlife dietary it ems. These residue assumptions are believed to reflect a realistic upper-bound residue estimate, although the degree to which this assumption reflects a specific percentile estimate is difficult to quantify. It is important to note that the field measurement efforts used to devel op the Fletcher estimates of exposure involve highly varied sampling techniques. It is entirely possible that much of these data reflect residues averaged over entire above ground plan ts in the case of grass and forage sampling.
It was assumed that ingestion of food items in the field occurs at rates commensurate with those in the laborato ry. Although the screening a ssessment process adjusts dryweight estimates of food intake to reflect the increased mass in fresh-weight wildlife food intake estimates, it does not allow for gross energy differences. Direct comparison of a laboratory dietary concentrati on- based effects threshold to a fresh-weight pesticide residue estimate would result in an underestimation of field exposure by food consumption by a factor of 1.25 – 2.5 for most food items.
Differences in assimilative efficiency betw een laboratory and wilddiets suggest that current screening assessment me thods do not account for a potentially important aspect of food requirements. Depending upon species and dietary matrix, bird assimilation of wild diet energy ranges from 23 – 80%, and mamm al’s assimilation ranges from 41 – 85% (U.S. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is formulated to maximize assimilative efficiency ( e.g. , a value of 85%), a potential for underestimation of exposure may exist by assu ming that consumption of food in the wild is comparable with consumption during laboratory testing. In th e screening process, exposure may be underestimated because me tabolic rates are not related to food consumption.
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal was assumed to occupy either the treated field or adjacent areas receiving a treatment rate on the field. Actual habitat requirements of any particular terrestrial species were not considered, and it was assumed that species occupy, exclusively and permanently, the modeled treatment area. Spray drift model predictions sugges t that this assumption leads to an overestimation of exposure to species that do not occupy the treated field exclusively and permanently.

5.3.1.6. Spray Drift Modeling
Although there may be multiple oxamyl applications at a single site, it is unlikely that the same organism would be exposed to the maximum amount of spray drift from every

103application made. In order for an organism to receive the maximum concentration of oxamyl from multiple applications, each appl ication of oxamyl would have to occur under identical atmospheric conditions ( e.g. , same wind speed and – for plants – same wind direction) and (if it is an animal) the animal being exposed would have to be present directly downwind at the same distance afte r each application. Although there may be sites where the dominant wind direction is fairly consistent (at least during the relatively quiescent conditions that are most favorable for aerial spray applications), it is nevertheless highly unlikely that plants in any specific area would receive the maximum amount of spray drift re peatedly. It appears that in most areas (based upon available meteorological data) wind direction is temporal ly very changeable, even within the same day. Additionally, other factors, includi ng variations in topography, cover, and meteorological conditions over the trans port distance are not accounted for by the AgDRIFT model ( i.e. , it models spray drift from aeria l and ground applications in a flat area with little to no ground cover and a st eady, constant wind speed and direction). Therefore, the drift estimates from AgDRIFT may overestimate exposure even from single applications, especially as the distance increases from the site of application, since the model does not account for potential obstructions ( e.g. , large hills, berms, buildings, trees, etc .). Furthermore, conservative assumptions are often made regarding the droplet size distributions being modele d (‘ASAE Very Fine to Fine’ for orchard uses and ‘ASAE Very Fine’ for agricultural us es), the application method ( e.g. , aerial), release heights and wind speeds. Alterations in any of these inputs would change the area of potential effect.

5.3.1.7. Location of Wildlife Species
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal was assumed to occupy either the treated field or adjacent areas receiving a treatment rate on the field. Actual habitat requirements of any particular terrestrial species were not considered, and it was assumed that species occupy, exclusively and permanently, the modeled treatment area. Spray drift model predictions sugges t that this assumption leads to an overestimation of exposure to species that do not occupy the treated field exclusively and permanently.

5.3.2. Effects Assessment Uncertainties

5.3.2.1. Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test orga nism age may have a significant impact on the observed sensitivity to a toxicant. The acute toxicity data for fish are collected on juvenile fish between 0.1 and 5 grams. Aqua tic invertebrate acute testing is performed on recommended immature age classes ( e.g. , first instar for daphni ds, second instar for amphipods, stoneflies, mayflies, and third instar for midges).
Testing of juveniles may overe stimate toxicity at older age classes for pesticide active ingredients that act directly without me tabolic transformation because younger age classes may not have the enzymatic systems a ssociated with detoxifying xenobiotics. In so far as the available toxicity data may provide ranges of sensitivity information with

104respect to age class, this assessment uses th e most sensitive life-stage information as measures of effect for surrogate aquatic an imals, and is therefore, considered as protective of the CRLF.

5.3.2.2. Use of Surrogate Species Effects Data

CRLF
Guideline toxicity tests and open literature da ta on oxamyl are not available for frogs or any other aquatic-phase amphibian; therefore, freshwater fish are used as surrogate species for aquatic-phase amphibians. Endpoi nts based on freshwater fish ecotoxicity data are assumed to be protective of potential direct effects to a quatic-phase amphibians including the CRLF, and extrapolation of the risk conclusions from the most sensitive tested species to the aquatic-phase CRLF is likely to overestimate the potential risks to those species. Efforts are made to select th e organisms most likely to be affected by the type of compound and usage pattern; however , there is an inherent uncertainty in extrapolating across phyla. In addition, the Agency’s LOCs are intentionally set very low, and conservative estimates are made in the screening level risk assessment to account for these uncertainties.

Terrestrial Plants
Plant toxicity data from both registrant-submitted studies and studies in the scientific literature were reviewed for this assessment. Registrant-submitted studies are conducted under conditions and with species defined in EPA toxicity test gui delines. Sub-lethal endpoints such as plant growth, dry weight, and biomass are evaluated for both monocots and dicots, and effects are evaluated at both seedling emergence and vegetative life stages. Guideline studies generally evaluate toxicity to ten crop species. A drawback to these tests is that they ar e conducted on herbaceous crop species only, and extrapolation of effects to other species, such as th e woody shrubs and trees and wild herbaceous species, contributes uncertainty to risk conclusions.
Commercial crop species have b een selectively bred, and may be more or less resistant to particular stressors than wild herbs and forb s. The direction of this uncertainty for specific plants and stressors, including oxa myl, is largely unknown. Homogenous test plant seed lots also lack th e genetic variation that occurs in natural populations, so the range of effects seen from tests is likely to be smaller than would be expected from wild populations.

5.3.2.3. Sublethal Effects
When assessing acute risk, the screening risk assessment relies on the acute mortality endpoint as well as a suite of sublethal respon ses to the pesticide, as determined by the testing of species response to chronic expos ure conditions and subsequent chronic risk assessment. Consideration of additional sublethal data in the effects determination t is exercised on a case-by-case basis and only after careful consideration of the nature of the

105sublethal effect measured and the extent and quality of available data to support establishing a plausible relationship between the measure of effect (sublethal endpoint) and the assessment endpoints. However, the fu ll suite of sublethal effects from valid open literature studies is considered for th e purposes of defining th e action area. To the extent to which sublethal effect s are not considered in this as sessment, the potential direct and indirect effects of oxamyl on CRLF may be underestimated.

5.3.2.4. Reproductive effects to plants
Potential reproductive effects to plants are no t considered as endpoint s in this assessment. The toxicity data used in this assessment in dicate that 2.1 lb a.i./Aof oxamyl causes less than 25% effects to the vegetative vigor and s eedling emergence of tested (crop) species. However, oxamyl is used to thin apples at single application rate s of 0.5-1.0 lb a.i./A (registration # 352-372). Based on this informati on, it is possible that oxamyl applications could result in reproductive e ffects to non-target plants.

5.4. Addressing the risk hypotheses

In order to conclude this ri sk assessment, it is necessary to address th e risk hypotheses defined in Section 2.9.1. Based on the result s of this assessment, several hypotheses can be rejected, meaning that they are not of c oncern for the CRLF. However, several of the original hypotheses cannot be rejected, meaning that the stat ements represent concerns in terms of effects of oxamyl on the CRLF.
Based on the results of this assessment, the following hypotheses canbe rejected:

• Labeled uses of oxamyl within the ac tion area may indirectly affect the CRLF and/or adversely modify designated critic al habitat by reducing or changing the composition of the aquatic plant commun ity in the ponds and streams comprising the species’ current range and designated critical habitat, thus affecting primary productivity and/or cover;

• Labeled uses of oxamyl within the acti on area may indirectly affect the CRLF and/or adversely modify designated critic al habitat by reducing or changing the composition of the terrestrial plant community ( i.e. , riparian habitat) required to maintain acceptable water quality an d habitat in the ponds and streams comprising the species’ current range and designated critical habitat;

• Labeled uses of oxamyl within the action area may adversely modify the designated critical habitat of the CRLF by reducing or changing upland habitat within 200 ft of the edge of the riparian vegetation nece ssary for shelter, foraging, and predator avoidance.

• Labeled uses of oxamyl within the action area may adversely modify the designated critical habitat of the CRLF by reducing or changing dispersal habitat within designated units and between o ccupied locations within 0.7 mi of each

106other that allow for movement between sites including both natural and altered sites which do not contain barriers to dispersal.

• Labeled uses of oxamyl within the action area may adversely modify the designated critical habitat of the CRL F by reducing or changing breeding and non-breeding aquatic habitat (via modification of water quality parameters, habitat morphology, and/or sedimentation).

Based on the results of this assessm ent, the following hypotheses can not be rejected.

• Labeled uses of oxamyl within the ac tion area may directly affect the CRLF by causing mortality or by adversely a ffecting growth or fecundity;

• Labeled uses of oxamyl within the acti on area may indirectly affect the CRLF by reducing or changing the composition of food supply;

• Labeled uses of oxamyl within the action area may adversely modify the designated critical habitat of the CRLF by reducing the food supply required for normal growth and viability of juvenile and adult CRLFs;

• Labeled uses of oxamyl within the action area may adversely modify the designated critical habitat of the CRLF by altering chemical characteristics necessary for normal growth and viab ility of juvenile and adult CRLFs.

6. Risk Conclusions
In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the information presented in this endangered specie s risk assessment represents the best data currently available to assess the potential risks of oxamyl to the CRLF and its designated critical habitat.
Based on the best available information, the Agency makes a May Affect, and Likely to Adversely Affect (LAA) determination for the CRLF from the use of oxamyl. Additionally, the Agency has determined th at there is the potential for modification of CRLF designated critical habita t from the use of the chemical. These conclusions are based on potential effects of oxamyl to the terrestrial-phase CRLF and its prey, including terrestrial insects, small mammals and terrestrial-phase frogs. Summaries of the risk conclusions and effects determinati ons for the CRLF and its critical habitat are presented in Table 45 and Table 46, respectively. Analysis related to the intersection of the oxamyl action area and CRLF habitat used in determining use patterns that result in LAA determinations are described in Appendix A . The LAA determination for the CRLF and potential modification of designated cr itical habitat is described in the baseline status and cumulative effects fo r the CRLF and is provided in Attachment 2

.

107Table 45. Description of evidence supporting effe cts determination for oxamyl use in California. Effects Habitat Basis for LAA Determination Direct Aquatic Direct effects to aquatic-phase CRLF resulting from acute and chronic exposures of oxamyl are not expected. - RQs for acute and chronic exposures resulting from all uses of oxamyl are below the levels of concern. Direct Terrestrial Oxamyl has the potential to directly affect the terrestrial-phase CRLF. -Acute and chronic RQs for all uses of oxamyl ex ceed the Agency’s LOCs for the terrestrial-phase CRLF.

- The likelihoods of individual mortality range from 0.00034% to 100% for terrestrial-phase CRLF on a field treated with uses of oxamyl that ha ve LOC exceedances (relevant to California). - Comparison of the LOAEC directly to chronic dietary-based EECs for CRLF consuming small insects and small herbivore mammals indicate that EECs for all uses are suffici ent to exceed the concentration where reproductive effects were observed in the laboratory. Indirect Aquatic Indirect effects to the CRLF through effects to its prey in th e aquatic habitat are not expected. - prey - RQs representing exposures to non-vascular aquatic plants (which serve as prey to tadpole stage CRLF) are below LOCs for all uses of oxamyl. - RQs representing acute and chronic exposures to fish (which serve as prey to adult CRLF) are below LOCs for all uses of oxamyl. - Although some RQs representing acute exposures to aquatic invertebrates are above the LOC, the likelihood of individual effects chance indicates th at all uses of oxamyl ar e expected to result in ≤ 0.34% chance of effects to an individual aquatic invertebrate. Therefore, potential i ndirect effects to the CRLF due to effects of oxamyl to aquatic invertebrates resulting from acute exposures are discountable. - RQs representing chronic exposures to aquatic invertebrates (serving as prey to juvenile and adult CRLF) are below LOCs, with the exception of 2 uses (garlic and celery). EECs for garlic and celery do not reach the NOAEC for less sensitive species of aquatic invertebrates ( i.e.
, Daphnia magna ), suggesting that even though sensitive species of aquatic invertebrates may be affected by chronic exposures of oxamyl, less sensitive species, such as daphnids, may not be affected. Because the CRLF is an opportunistic feeder, the impact of effects to sensitive aquatic invertebrates from chronic exposures on the CRLF is discountable. Indirect Aquatic Indirect effects to the CRLF through modification of its aquatic habitat are not expected. - habitat -RQs representing exposures to non-vascular and vascular aquatic plants are below LOCs. -Estimated exposures of oxamyl to riparian vegetation are above the EC 25 values for monocots and dicots. Indirect Terrestrial Oxamyl has the potential to indirectly affect the terrestrial-phase CRLF through effects to its prey. - prey -RQs representing exposures to terrestrial ins ects are above the LOC for all uses of oxamyl. - The likelihood of individual mortality is >99.9% for a terrestrial invertebrate on a field treated with any use of oxamyl (relevant to California). - >22% chance of mortality to individual small insect s can occur within 950 feet from the edge of a field treated with 1 lb a.i./A oxamyl by aerial methods. -RQs representing acute and chronic exposures to small terrestrial mammals are above LOCs for all uses of oxamyl. - The likelihood of individual mortality is >99.9% for a small mammal consuming short grass on a field treated with any use of oxamyl (relevant to California). -Dose-based and dietary-based EECs are above levels where subacute effects to mammals were observed in chronic toxicity studies. -RQs representing exposures to terrestrial-phase frogs are above the LOC for all uses of oxamyl.

- There is a >10% chance of effects to an individualterrestrial phase frog (serving as prey to CRLF) consuming small insects for all oxamyl uses, and a >10% chance of effects to an individual terrestrial phase frog consuming large insects for a majority of oxamyl uses (relevant to California). -Dose-based and dietary-based EECs are above the levels where subacute effects to birds were observed in chronic toxicity studies. Indirect - habitat Terrestrial Indirect effects to the CRLF through modi fication of its terrestrial habitat are not expected. -Estimated exposures of oxamyl to terrestrial vegetation are above the EC 25 values for monocots and dicots.

108Table 46. Summary of effects determination for CRLF critical habitat based on uses of oxamyl in California. Assessment Endpoint Effects Determination Basis for Determination

Modification of aquatic-phase primary constituent elements Habitat Modification Modification of the aquatic-phase PCE is not expected. - RQs for acute and chronic exposures directly to the CRLF resulting from all uses of oxamyl are below the levels of concern. - Indirect effects to the CRLF through effects to its prey in the aquatic habitat are not expected (see Table 1). -RQs representing exposures to non-vascular and vascular aquatic plants are below LOCs. -Estimated exposures of oxamyl to riparian vegetation are above the EC 25 values for monocots and dicots. Modification of terrestrial-phase primary constituent elements Oxamyl has the potential to modify the terrestrial-phase PCE. - Oxamyl has the potential to directly affect the terrestrial-phase CRLF (See Table 1). Oxamyl has the potential to indirectly affect the terrestrial-phase CRLF through effects to its prey (see Table 1). -Estimated exposures of oxamyl to terrestrial vegetation are below the EC 25 values for monocots and dicots.

Based on the conclusions of this assessment, a formal consultation with the U. S. Fish and Wildlife Service under Section 7 of the Endangered Specie s Act should be initiated.
When evaluating the significance of this ri sk assessment’s direct/indirect and habitat modification effects determinations, it is im portant to note that pesticide exposures and predicted risks to the species and its resources ( i.e. , food and habitat) are not expected to be uniform across the action area. In fact, given the assumptions of drift and downstream transport ( i.e. , attenuation with distan ce), pesticide exposure and associated risks to the species and its resources are expected to d ecrease with increasing di stance away from the treated field or site of application. Eval uation of the implication of this non-uniform distribution of risk to the species would require information and assessment techniques that are not currently available. Examples of such information and methodology required for this type of analysis would include the following:

• Enhanced information on the density and distribution of CRLF life stages within specific recovery units and/or designated critical habitat within the action area. This information would allow for quantitativ e extrapolation of the present risk assessment’s predictions of individual effects to the proportion of the population extant within geographical areas where those effects are predicted. Furthermore, such population information would allow for a more comprehensive evaluation of the significance of potential resource impairment to individuals of the species.

• Quantitative information on prey base requirements for individual aquatic- and terrestrial-phase frogs. While existing info rmation provides a preliminary picture of the types of food sources utilized by the frog, it does not establish minimal requirements to sustain healthy individuals atvarying life stages. Such information

109could be used to establish biologically releva nt thresholds of effects on the prey base, and ultimately establish geographical limits to those effects. This information could be used together with the density data discussed above to ch aracterize the likelihood of adverse effects to individuals.

• Information on population responses of prey base organisms to the pesticide. Currently, methodologies are limited to pr edicting exposures and likely levels of direct mortality, growth or reproductive impairment immediately following exposure to the pesticide. The degree to which re peated exposure events and the inherent demographic characteristics of the prey population play into the extent to which prey resources may recover is not predictable. An enhanced understanding of long-term prey responses to pesticide exposure would allow for a more refined determination of the magnitude and duration of resource impairment, and together with the information described above, a more complete predic tion of effects to individual frogs and potential modification to critical habitat.

7. References
Altig, R. and R.W. McDiarmid. 1999. Body Plan: Development and Morphology. In R.W. McDiarmid and R. Altig (Eds.) , Tadpoles: The Biology of Anuran Larvae.University of Chicago Press, Chicago. pp. 24-51.

Alvarez, J. 2000. Letter to the U.S. Fi sh and Wildlife Service providing comments on the Draft California Red-le gged Frog Recovery Plan.
Atkins. E.L., E.A. Greywood, and R.L. MacD onald. 1975. Toxicity of pesticides and other agricultural chemicals to honey bees . Laboratory studies. Univ. of Calif., Div. Agric. Sci. Leaflet 2287. 38 pp. (MRID# 000369-35).
Burns, L.A. 2004. Exposure Analysis M odeling System (EXAMS): User Manual and System Documentation. Revision G. EP A/600/R-00/081. National Exposure Research Laboratory, Office of Resear ch and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC. May, 2004.

Carousel, R.F., J.C. Imhoff, P.R. Hummel, J.M. Cheplick, A.S. Donigian, Jr., and L.A. Suarez. Undated. PRZM-3, A Model for Pred icting Pesticide and Nitrogen Fate in the Crop Root and Unsaturated Soil Zones: Users Manual for Release 3.12.2. National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Athens , GA; AQUA TERRA Consultants, Mountain View, CA; Waterborne Envir onmental, Inc., Leesburg, VA.

Crawshaw, G.J. 2000. Diseases and Pathology of Amphibians and Reptiles in: Ecotoxicology of Amphibians and Reptiles; ed: Sparling, D.W., G. Linder, and C.A. Bishop. SETAC Publication Series, Columbia, MO.

110Fellers, G. M., et al. 2001. Overwintering tadpoles in the California red-legged frog ( Rana aurora draytonii ). Herpetological Review, 32(3): 156-157.

Fellers, G.M, L.L. McConnell, D. Pratt, S. Datta. 2004. Pesticides in Mountain YellowLegged Frogs (Rana Mucosa) from the Sierra Nevada Mountains of California, USA. Environmental Toxicology & Chemistry 23 (9):2170-2177.
Fellers, Gary M. 2005a. Rana draytonii Baird and Girard 1852. California Red-legged Frog. Pages 552-554. In : M. Lannoo (ed.) Amphibian Declines: The Conservation Status of United States Species, Vol. 2: Species Accounts. University of California Press, Berkeley, California. xxi+1094 pp. ( http://www.werc.usgs.gov/ptreyes/pdfs/Rana%20draytonii.PDF )
Fellers, Gary M. 2005b. California red-legged frog, Rana draytonii Baird and Girard. Pages 198-201. In : L.L.C. Jones, et al (eds.) Amphibians of the Pacific Northwest. xxi+227.
Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeg er. 1994. Literature review and evaluation of the EPA food-chain (Kenaga) nomogram, and instrument for estimating pesticide residues on plants. Environmental To xicology and Chemistry 13 (9):1383-1391.
Hayes, M.P. and M.R. Jennings. 1988. Habitat correlates of distribution of the California red-legged frog (Ran a aurora draytonii) and the foothill yellow-legged frog (Rana boylii): Implications for manageme nt. Pp. 144-158. In Proceedings of the symposium on the management of amphibians, reptiles, and small mammals in North America. R. Sarzo, K.E. Severson, and D. R. Patton (technical coordinators). USDA Forest Service General Technical Report RM-166.
Hayes, M.P. and M.M. Miyamoto. 1984. Biochemical, behavioral and body size differences between Rana aurora aurora and R. a. draytonii . Copeia 1984(4): 1018-22.
Hayes and Tennant. 1985. Diet and feeding be havior of the California red-legged frog. The Southwestern Naturalist 30(4): 601-605.
Hoerger, F., and E.E. Kenaga. 1972. Pe sticide residues on plants: Correlation of representative data as a basi s for estimation of their magnitu de in the environment. In F. Coulston and F. Korte, eds ., Environmental Quality and Safety: Chemistry, Toxicology, and Technology, Georg Thieme Publ, Stuttgart, West Germany, pp. 9-28.
Jennings, M.R. and M.P. Hayes. 1985. Pre- 1900 overharvest of Ca lifornia red-legged frogs ( Rana aurora draytonii ): The inducement for bullfrog (Rana catesbeiana ) introduction. Herpetological Review 31(1): 94-103.
Jennings, M.R. and M.P. Hayes. 1994. Amphibianand reptile species of special concern in California. Report prepared for the California Department of Fish and Game, Inland Fisheries Division, Rancho Cordova, California. 255 pp.

111Jennings, M.R., S. Townsend, and R.R. Duke. 1997. Santa Clara Vall ey Water District California red-legged frog di stribution and status – 1997. Fi nal Report prepared by H.T. Harvey & Associates, Alviso, California. 22 pp.

Karvonen, T., Koivusalo, H., Jauhiainen, M., Palko, J. and Weppling, K. 1999. A hydrological model for predicti ng runoff from different la nd use areas, Journal of Hydrology, 217(3-4): 253-265.
Kuhn, J.O. 1991. Acute Oral Toxicity Study in Rats. CIBA -GEIGY Corporation, Agricultural Division, Greensboro, NC. Study Number 7803-91.
Kupferberg, S. 1997. Facilitation of pe riphyton production by tadpole grazing: Functional differences between spec ies. Freshwater Biology 37:427-439.
Kupferberg, S.J., J.C. Marks and M.E. Power. 1994. Effects of variation in natural algal and detrital diets on larval anuran ( Hyla regilla ) life-history traits. Copeia 1994:446-457.

LeNoir, J.S., L.L. McConnell, G.M. Fellers, T.M. Cahill, J.N. Seiber. 1999. Summertime Transport of Current -use pesticides from California’s Central Valley to the Sierra Nevada Mountain Ra nge,USA. Environmental Toxicology & Chemistry 18(12): 2715-2722.
Majewski , M.S. and P.D. Capel. 1995. Pesticid es in the atmosphere: distribution, trends, and governing factors. Ann ArborPress, Inc. Chelsea, MI.
Mayer, F. L. J. and Ellersieck, M. R. 1986. Manual of Acute Toxic ity: Interpretation and Data Base for 410 Chemicals and 66 Species of Freshwater Animals. Resour.Publ.No.160, U.S.Dep.Interior, Fish Wildl.Serv., Washington, DC 505 p.
McConnell, L.L., J.S. LeNoir, S. Datta, J.N. Seiber. 1998. Wet deposition of current-use pesticides in the Sierra Nevada mountain range, California, USA. Environmental Toxicology & Chemistry 17(10):1908-1916.
McDonald M.A.1; Healey J.R.; Stevens P. A. 2002. The effects of secondary forest clearance and subsequent land-use on erosi on losses and soil properties in the Blue Mountains of Jamaica. Agriculture, Ecosyste ms & Environment, Volume 92, Number 1: 1-19.

Okisaka S.; Murakami A.; Mizukawa A.; Ito J.; Vakulenko S.A.; Molotkov I.A.; Corbett C.W.; Wahl M.; Porter D.E.; Edwards D.; Moise C. 1997. Nonpoint source runoff modeling: A comparison of a forested wate rshed and an urban watershed on the South Carolina coast. Journal of Experiment al Marine Biology and Ecology, Volume 213, Number 1: 133-149.

112Phuong V.T. and van Dam J. Linkages between fo rests and water: A review of research evidence in Vietnam. In : Forests, Water and Livelihoods European Tropical Forest Research Network. ETFRN NEWS (3pp).

Rathburn, G.B. 1998. Rana aurora draytonii egg predation. Herp etological Review, 29(3): 165.
Reis, D.K. Habitat characteristics of California red-legged frogs ( Rana aurora draytonii ): Ecological differences between eggs, tadpoles , and adults in a coastal brackish and freshwater system. M.S. Thesis. San Jose State University. 58 pp.
Seale, D.B. and N. Beckvar. 1980. The comparative ability of anuran larvae (genera: Hyla
, Bufo and Rana ) to ingest suspended blue-g reen algae. Copeia 1980:495-503.
Sparling, D.W., G.M. Fellers, L.L. McC onnell. 2001. Pesticides and amphibian population declines in California, USA. E nvironmental Toxicology & Chemistry 20(7): 1591-1595.

U.S. Department of Agriculture (USDA). 2000. Crop Profile for Celery in California. United States Department of Agriculture, Cooperative State Research, Education and Extension Service. ( http://www.ipmcenters.org/cropprofiles/docs/cacelery.html ) January, 2000.
USDA. 2008. The Census of Agriculture. National Agricultural Statistic Service (NASS). ( http://www.agcensus.usda.gov/ ) Accessed November 10, 2008.

U.S. Environmental Protection Agency (U.S . EPA). 1998. Guidance for Ecological Risk Assessment. Risk Assessment Fo rum. EPA/630/R-95/002F, April 1998.

U.S. EPA. 2000. Interim Reregistration Eligibility Decision: Oxamyl. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances. EPA-738-R-015. October, 2000.

U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs. Office of Prevention, Pe sticides, and Toxic S ubstances. Office of Pesticide Programs. Washington, D.C. January 23, 2004.

U.S. EPA. 2006. Standardized Soil Mob ility Classification Guidance. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects Division, Memorandum. Apr. 21, 2006.

U.S. EPA. 2006 a . Review and classification of data from Mayer and Ellersieck (1986). Internal memorandum from Steven Bradbury to Environmental Fate and Effects Division. United States Envir onmental Protection Agency.

113U.S. EPA. 2006 b . User’s Guide: TerrPlant Versio n 1.2.2 (Terrestrial Residue Exposure model). United States Environmental Pr otection Agency. Environmental Fate and Effects Division. Office of Pesticide Program s. U.S. Environmental protection Agency. Washington, D.C. December 26, 2006.

U.S. EPA. 2006 c . User’s Guide: T-REX Version 1.3.1 (Terrestrial Residue Exposure model). United States Environmental Pr otection Agency. Environmental Fate and Effects Division. Office of Pesticide Programs. U.S. Environmental Protection Agency. Washington, D.C. December 07, 2006.

U.S. EPA. 2007. Echeverria, M. Tier II Drinking Water Exposure Assessment for the Section 3 New Use Registration of Oxamyl on Sugar Beets. U.S. Environmental Protection Agency, Office of Prevention, Pes ticides and Toxic Substances, Office of Pesticide Programs. Memorandum from the Envi ronmental Fate and Effects Division to the Registration Division and the He alth Effects Division. July 16, 2007.

U.S. EPA. 2007 a . User’s Guide. T-HERPS Version 1.0. Environmental Fate and Effects Division. Office of Pesticide Programs. U.S. Environmental Protection Agency. Washington, D.C. May 15, 2007.

U.S. Fish and Wildlife Service (USFWS). 1996. Endangered and threatened wildlife and plants: determination of threatened status for the California red- legged frog. Federal Register 61(101):25813-25833.
USFWS. 2002. Recovery Plan for the California Red-legged Frog ( Rana aurora draytonii ). Region 1, USFWS, Portland, Oregon. ( http://ecos.fws.gov/doc /recovery_plans/2002/020528.pdf )
USFWS. 2006. Endangered and threatened wildli fe and plants: determination of critical habitat for the California red-legged frog. 71 FR 19244-19346.

USFWS. Website accessed: 30 December 2006. http://www.fws.gov/endangered/f eatures/rl_frog/rlfrog.html#where

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. Endangered Species Consultation Handbook: Procedures for Conducting Consultation and Conference Activ ities Under Section 7 of the Endangered Species Act. Final Draft. March 1998.

USFWS/NMFS. 2004. Memorandum to Office of Prevention, Pesticides, and Toxic Substances, U.S. EPA conveying an evaluation by the U.S. Fish and Wildlife Service and National Marine Fisherie s Service of an approach to a ssessing the ecological risks of pesticide products.

U.S. Geological Survey (USGS). 2007. San Joaquin - Tulare NAWQA Program. Webpage last updated: Oct. 15, 2007. http://ca.water.us gs.gov/sanj/sw_11274538.html

114Willis, G.H. and L.L. McDowell. 1987. Pesticide Persistence on Foilage in Reviews of Environmental Contaminati on and Toxicology. 100:23-73.
Wassersug, R. 1984. Why tadpoles love fast food. Natural History 4/84.

Submitted Environmental Fate Studies
Acc. # 40494. Harvey, Jr., J. and J. Han. 1977. Decomposition of Oxamyl in Soil and Water. Unpublished study prepared and submitted by E.I. du Pont de Nemours & Co., Wilmington, DE. 38 p.
Acc. # 63012. Dulka, J. and A. Julius. 1978. Microbial Degradation of 1- 14 C-Oxamyl in Soil. Unpublished study submitted by E.I. du Pont de Nemours & Co., Wilmington, DE. 22 p.
Acc. # 141395. Chrzanowski, R. 1984. Soil Column Adsorption Studies with Vydate® Oxamyl Insecticide/Nematicide. Unpublished study prepared and submitted by E.I. du Pont de Nemours & Co., Inc. 12 p.

Acc. # 145302. E. I. du Pont de Nemours a nd Co., Inc. 1982. Data Supporting the Use of Vydate® L Insecticide/Nematicide on Potatoes: Ground Water Analyses and Soil Residue Determinations of Oxamyl, Long Island, New York, 1981. Unpublished study prepared and submitted by E. I. du Pont de Nemours and Co., Inc., Wilmington, DE. Jan. 1982. 59 p.
Acc. # 147704. Barefoot, A. 1985. Photodegradation of 14 C-Oxamyl on Soil. Document No. AMR-334-85. Unpublished study prepared and submitted by E.I. du Pont de Nemours and Co., Inc., Wilmington, DE. 23 p.
Acc. # 149231. McIntosh, C., J. Jenkins, D. Burgoyne, D. Ferguson. 1984. A Two-year Field Study to Determine the Fate of Oxamyl in Soil during Flood Irrigation. Unpublished study prepared and submitted by E.I. du Pont de Nemours and Co., Inc., Wilmington, DE. 14 p.
MRID 40499702. Silveira, E. 1988. Oxamyl Physical and Chemical Characteristics. Laboratory Project ID: D1410.B. Unpublishe d study prepared by E.I. du Pont de Nemours and Company, Inc., Wilmington, DE. Jan. 21, 1988. 79 p.
MRID 40606514. Rhodes, B., R. Hughes, J. Nolker. 1987. Soil Column Leaching Studies with [1- 14 C]Oxamyl. Laboratory Projec t ID: AMR- 865-87. Unpublished study prepared and submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE. Nov. 20, 1987. 43 p.

115MRID 40606515. McNally, M. and J. Wheel er. 1988. Photodegradation of [1- 14 C] Oxamyl in Buffer Solution pH 5 (Conducted in Simulated Sunlight). Lab Project ID: AMR-960-87. Unpublished study prepar ed by E.I. du Pont de Nemours & Company, Inc., Wilmington, DE. Mar. 30, 1988. 52 p.
MRID 40606516. McNally, M. and J. Wh eeler. 1988. Hydrolysis of [1- 14 C] Oxamyl. Laboratory Project ID: AMR-961-87. U npublished study prepared and submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE. Mar. 30, 1988. 45 p.
MRID 41058801. McNally, M. 1988. Suppl ement #1 to: Photodegradation of [1- 14 C] Oxamyl in Buffer Solution pH 5 (Conducte d in Simulated Sunlight). Laboratory Project ID: AMR-960-87. Unpublished study prepared and submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE. Mar. 30, 1988. 7 p.
MRID 41346201. Hawkins, D., B. Mayo, A. Pollard, W. Donschak. 1989. The Metabolism of 14 C-Oxamyl in Silt Loam Soil under Aerobic and Anaerobic Conditions. Lab Project Number: HRC/DPT 198/891478; DuPont Protocol No. AMR-1200-88. Unpublished study preparedby Huntingdon Research Centre Ltd., Cambridgeshire, England; sponsored and submitted by E.I. du Pont de Nemours and Company, Wilmi ngton, DE. Oct. 31, 1989. 53 p.

MRID 41573201. Lin, W. and J. Eble. 1990. Fiel d Soil Dissipation of Vydate® Insecticide/Nematicide. DuPont Projec t ID: AMR-1151-88. Unpublished study performed by McKenzie Laboratories, Inc ., Phoenix, AZ and E. I. Du Pont de Nemours & Co., Wilmington, DE; submitted by E. I. Du Pont de Nemours & Co., Wilmington, DE. May 21, 1990. 167 p.

MRID 41963901. Lin, W. and J. Eble. 1991. Field Soil Dissipation of Vydate® Insecticide/ Nematicide. DuPont Pr oject ID: AMR-1151-88; Revision No. 1. Unpublished study performed by E.I. du P ont de Nemours and Co., Wilmington, DE and McKenzie Laboratories, Inc., P hoenix, AZ; submitted by E.I. du Pont de Nemours and Co., Wilmington, DE. Jul. 25, 1991. 64 p.

MRID 42526101. Barefoot, A. and L. Cooke. 1989. Vapor Pressure of Oxamyl. Lab Project Number: AMR-1267-88. Unpublished study prepared by E.I. du Pont de Nemours & Company, Inc. May 23, 1989. 19 p.
MRID 42820001. Spare, W. 1991. An aerobic Soil Metabolism of [1- 14 C]Oxamyl in Madera, California Soil. Lab Project Number: 1712; Du Pont Protocol No. AMR1851-90. Unpublished study prepared by Agrisearch Inc., Frederick, MD; submitted by E. I. du Pont de Nemour s & Co., Inc., Wilmington, DE. Nov. 22, 1991. 53 p.
MRID 45045304. McClory, J., D. Orescan. 199 6. Field Soil Dissipation of Oxamyl Following Application of Vydate® L Insecticide. Lab Project ID: 1708; DuPont Project ID: AMR 2889-93. Unpublished study prepared by E. I. du Pont de

116Nemours & Co., Inc., Wilmington, DE and Ra llis India Limited, Bangalore, India. Mar. 28, 1996. 144 p.
MRID 45045305. Spare, W. 1995. De gradability and Fate of [1- 14 C]Oxamyl in Water/Sediment Systems. Lab Project Number: 1743; DuPont Protocol No. AMR 3143-94. Unpublished study prepared by Agrisearch Inc., Frederick, MD; sponsored and submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE. Dec. 4, 1995. 81 p.
MRID 45176602. Mattson, S. and B. Smyser. 2000. Rate of Degradation of Oxamyl in Three Aerobic Soils. DuPont Projec t ID: DuPont-2957. Unpublished study prepared and submitted by E.I. du Pont de Nemours and Company, Wilmington, DE. Jul. 14, 2000. 64 p.
MRID 46237301. Santos, L., M. Ohm, A. Van-Nguyen. 2001. Absorption/Desorption of 14 C-Oxamyl in Five Soils. Proj ect Number: 3166; Revision No. 1. Unpublished study prepared and submitted by E.I. du Pont de Nemours and Company, Wilmington, DE.; Ne wark DE. Aug. 3, 2001. 49 p.

117