Docket Number EPA-HQ-OPP-2010-0240

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Xylenol AMENDED FINAL WORK PLAN

The Agency 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) reduction 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 

anticipated for both study types. The Agency 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 assessment. For purposes of 

conducting a hazard assessment rather than an ecological risk assessment only the avian acute oral 

study is critical. Therefore the Agency 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 freshwater 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-OPP2010-0240-004). The estuarine/marine acute fish requirement was missed in the 2010 Xylenol Work 

Plan, only the freshwater species was identified. The Agency estimated acute 96-h LC50 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-xylenol 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 phenolic compounds. This relationship indicates that estuarine/marine fish species 

may be more sensitive than freshwater fish for such compounds. Both of the 96-h LC50 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 the hazard standard and the degree of uncertainty in the phenol 

structure activity relationship (SAR) model (ECOSAR v1.11 On-line Help for Phenols), the Agency 

still anticipates requiring fish acute testing but only with the more sensitive estuarine/marine fish 

taxonomic group. The preferred test species is a silverside (Menidia sp.).

The other anticipated ecological effects 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 Agency evaluated if the structure activity relationship 

model, ECOSAR (v 1.11) could provide a reasonable acute 48-h EC50 value for daphnid, rather than 
Docket Number EPA-HQ-OPP-2010-0240

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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 Online Help for Phenols) for daphnids, the Agency 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 requirement per 40 CFR part 152.94 by citing, and submitting to the 

Agency a valid study from the public literature. The Agency 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 LC50 values of 1.3 to 1.8 ppm. Daphnia 

magna appeared to be the more sensitive freshwater invertebrate species with 48-h EC50 values 

ranging from 2.1 to 2.4 ppm. The Agency has not reviewed the 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 registration review of xylenol 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 toxicity test PAI 12

i

Unless otherwise stated by the Agency, all other elements of the Agency's December 2010 Xylenol

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 delayed 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 species.