### Docket Number EPA

- HQ

- OPP

- 201 0

- 0240

www.regulations.gov

2 Xylenol AMENDED FINAL WORK PLAN

The A gency is amending the 2010 Xylenol Final Work Plan (EPA

- HQ

- OPP

- 2010

- 0240

- 007 ) such that the anticipated ecological effects data consist of the following three studies:

 (GLN 850.1010) Acute aquatic invertebrate, Daphnia magna

 (GLN 850.1075) Acute fish, estuarine/marine fish

, Menidia sp.

 (GLN 850.2100) Acute avian oral, upland game bird
These changes reflect 1) re duction in the amount of avian data anticipated as needed to perform a hazard assessment; 2) corrections to what appears in the 2,4

- Xylenol: Product Chemistry/Environmental Fate and Ecological Effects Scoping document (EPA

- HQ

- OPP

- 2010

- 0240) to be differences between the list of anticipated ecological effects data section versus the data justification tables provided in Appendix B; and 3) modification of fish species required based on consideration of ecological effects structure activity models for xylenol

. In the 2010 Xylenol Final Work Plan and 2,4

- Xylenol: Product Chemistry/Environmental Fate and Ecological Effects Scoping document , two avian ecological effects studies were anticipated to be required for registration review, one an avian acute oral and the other an avian subacute dietary study. Testing with only one species, an upland game bird

— the northern bobwhite quail was antic ipated for both study types

. The A gency identified in the 2010 2,4

- Xylenol: Product Chemistry/Environmental Fate and Ecological Effects Scoping document that registration review would require only a hazard assessment, rather than an ecological risk assess ment. For purposes of conducting a hazard assessment rather than an ecological risk assessment only the avian acute oral study is critical . Therefore the A gency is removing the avian subacute dietary data requirement (Guideline 850.2200) for xylenol

. In the 2,4

- Xylenol: Product Chemistry/Environmental Fate and Ecological Effects Scoping document acute fish testing with both a freshwater species and an estuarine/marine species was anticipated to be required for registration review

. Testing with a fresh water species, the rainbow trout

, was identified as anticipated in the main body of the scoping document

, but additional testing of an estuarine/marine species, the Atlantic silverside was also identified in Appendix B (EPA

- HQ

- OPP

2010

- 0240

- 004). The estu arine/marine acute fish requirement was missed in the 2010 Xylenol Work Plan , only the freshwater species was identified

. The A gency estimated acute 96

- h LC 50 2,4

- xylenol values for a freshwater and estuarine/marine fish using a structure activity relationship model, ECOSAR (version (v) 1.11). The estimated 2,4

- xylen ol values from ECOSAR (v1.11) of 7.3 ppm and 2.9 ppm for a freshwater fish and a saltwater species, respectively, are based on relationships observed with phenol ic compound s . This relat ionship indicate s that estuarine/marine fish species may be more sensitive than freshwater fish for such compounds

. Both of the 96

- h LC 50 values are close to the Agency’s current pesticide hazard labeling standard of 1 ppm. Given how close the estuarine/ marine acute value is to th e hazard standard and the degree of uncertainty in the phenol structure activity relationship (SAR) model ( ECOSAR v1.11 On

- line Help for Phenols ), the A gency still anticipates requiring fish acute testing but only with the more s ensitive estuarine/marine fish taxonomic group. T he preferred test species is a silverside ( Men i dia sp.)

. The other anticipated ecological effect s data requirement in the 2010 Xylenol Final Work Plan and the 2010 2,4

- Xylenol: Product Chemistry/Environmental Fate and Ecological Effects Scoping document was for a freshwater daphnid. The A gency evaluated if the structure activity relationship model, E COSAR (v 1.11) could provide a reasonable acute 48

- h EC 50 value for daphnid, rather than

### Docket Number EPA

- HQ

- OPP

- 201 0

- 0240

www.regulations.gov

3 testing. The estimated 2,4

- xylenol value from ECOSAR (v1.11) of 2.9 ppm is based on relationships observed with phenolic compounds. Given how close this value is to the hazard standard and the degree of uncertainty in the phenol structure activity relationship (SAR) model (ECOSAR v1.11 On

line Help for Phenols) for daphnids, the A gency still anticipates requiring a freshwater acute daphnid study with 2,4

- xylenol. The preferred test species is still Daphnia magna

. Per 40 CFR part 152 there are a number of ways registrants can submit information to meet a data requirement. One way is generation of a new valid study (40 CFR §152.92), but alternatively the registrant can meet a data requiremen t per 40 CFR part 152.94 by cit ing, and submitting to the Agency a valid study from th e public literature. The A gency is aware that there are 2,4

- xylenol ecological effects data in the public literature for a number of freshwater and estuarine/marine species per information obtained from EPA’s ECOTOXicology database (ECOTOX version 4 [ 

### http://cfpub.epa.gov/ecotox/quick_query.htm ] ). Inland silverside ( Menidia beryllina ) was the most sensitive estuarine/marine fish species with 96

- h LC 50 values of 1.3 to 1.8 ppm. Daphnia
magna appeared to be the more sensitive freshwater invertebrate species with 48

- h EC 50 values ranging from 2.1 to 2. 4 ppm. The A gency has not reviewed t he validity of these studies for registration review purposes. If the registrant obtains these studies, they can be submitted to meet anticipated data requirements.
Summary of Data Requirements
A summary table of the data required to support the regist ration review of x ylenol is presented below.
Anticipated Data Requirements for the Registration Review of Xylenol (PC code 086804)

Guideline Number Anticipated Data Requirement Test Material Estimated Timeframe

(Measured in months from DCI receipt) 835.2120 Hydrolysis of parent and degradates as a function of pH

at 25 C PAI 12

850.1010 2 Aquatic invertebrate acute toxicity, test, freshwater

daphnids PAI 24

850.1075 3 Fish acute toxicity test, estuarine marine PAI 18

850.2100 1 Avian acute oral to xicity test PAI 12

i Unless otherwise stated by the Agency, all other elements of the Agency's December 2010 X ylenol FWP remain unchanged.

1 Results from a study using one upland game bird is required. Preferred specie is a bobwhite quail. OECD TG 233 using the “LD50

- Slope test” or “limit dose test” can be used instead of OCSPP 850.2100 for certain species and conditions (e.g., causes no delay ed effects, causes no regurgitation?. Details on the species and conditions under which TG 233 would not fulfill the data requirement are described at http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/terrestrial_biology_tech_team/re view_avian_acute_oral_oecd_tg223.htm

2 Results from a study using one freshwater daphnid species are required. Data are preferred on Daphnia magna.

3 Results from a study using one estuarine/ marine fish species must be submitted to satisfy this requirement. Preferred species is a Menedia spec ies.