Docket Number: EPA-HQ-OPP-2010-0228 www.regulations.gov



## Linuron Final Work Plan Registration Review

December 20103 LINURON FINAL WORK PLAN

Introduction :

This is the Environmental Protection Agency’s (EPA’s) Final Work Plan for the registration review of linuron. This work plan includes the expected registration review timeline. The work plan also addresse s public comments received concerning the Preliminary Work Plan in the Summary Document , which was posted in the linuron registration review docket (EPA-HQ- OPP-2010-0228), and any other comments concerning the initial docket postings. The Summary Document provided information on what EPA knows about the pesticide and what additional risk analyses and data or information the Agency believes are needed to make a registration review decision.

The Agency is implementing the registra tion review program pursuant to Section 3(g) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered pesticide every 15 years to de termine whether it continues to meet the FIFRA standard for registration. Changes in science, public policy, and pesticide use practices will occur over time. The registra tion review program is intended to make sure that, as the ability to assess risk evolve s and as policies and practices change, all registered pesticides continue to meet th e statutory standard. The public phase of registration review begins when the initial docket is opened for each case. Information on this program is provided at: http://www.epa.gov/oppsrrd1/registration_review/

.

Linuron is an herbicide that is registered for use on certain terrestrial food and feed crops, and non-food and feed crops to control germinating and newly emerging grasses and broad-leafed weed s. Linuron is registered for use on asparagus, carrots, celery, corn (field and sweet), cotton, kenaf, lentils, parsley, parsnips, potato, sorghum, soybeans, and wheat. There are also re gistered uses on non- cropland (roadsides, fencerows, etc.), hybrid poplar plantations (pulpwood source) and ornamental bulbs. There are no registered residen tial uses. Linuron was first regi stered for use in the United States (U.S.) in 1966.

Comments Received on Preliminary Work Plan :

Multiple comments were received during the 60-day public comment period on

the Preliminary Work Plan

. These comments are summarized in this document and changes to the work plan set out in the Preliminary Work Plan are explained. In the Preliminary Work Plan , EPA also solicited comments on three specific topics: environmental justice, water body impairment, and trade irritants. No comments or information were received during the comment period concerning environmental justice, trade irritants, or water body impairment. Ho wever, several comments were received that change the anticipated data requirements fo r linuron. For further discussion on these comments please see the Summary of Comments and Agency Responses section below.

Anticipated Risk Assessment and Data Needs:4 The Agency anticipates requiring data needed to conduct comprehensive human health and ecological risk assessments, incl uding an endangered species assessment, for

the uses of linuron.

Ecological Risk:

• A screening-level environmental fate and ecological risk assessment for linuron was conducted in support of the 1995 Linur on Reregistration E ligibility Decision (RED).

• The Agency anticipates conducting an upda ted environmental fate and ecological risk assessment for linuron, including an endangered species assessment, during registration review.

• The Agency has not conducted a risk assessment that supports a complete endangered species determination for lin uron. The ecological risk assessment planned during registration review will a llow the Agency to determine whether linuron’s uses have “no effect” or “may affect” federally listed threatened or endangered species (listed species) or their designated critical habitats. When an

assessment concludes that a pesticide’s use “may affect” a listed species or its designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife Service and/or National Marine Fisheries Service (the Services), as appropriate.

• The Agency has conducted risk assessments for linuron that support endangered species determinations for the California red-legged frog (CRLF) in 2008 as well as for Pacific salmon and steelhead in 2004. In the 2008 CRLF endangered species assessment, the Agency made a “l ikely to adversely affect” determination for both direct and indirect effects of regist ered uses of linuron in California to the threatened red-legged frog. In the 2004 endangered species assessment for threatened Pacific salmon and steelhead, the Agency made a “may affect but are not likely to adversely affect” finding for seven listed Pacific salmon and steelhead Evolutionarily Significant Units (ESU) and a “no effect” finding on the remaining nineteen ESUs. The Agency concluded that the endangered species Level of Concern (LOC) for registered uses of linuron was exceeded for aquatic

invertebrates for all use sites and for fr eshwater fish for wheat, asparagus, and rights of way (ROW) uses.

• EPA anticipates requiring the following guide line studies in order to conduct the planned environmental fate and ecological risk assessments during the registration

review of linuron:

o 835.4100 Aerobic soil metabolism

o 835.4200 Anaerobic soil metabolism

o 835.4300 Aerobic aquatic metabolism

o 850.1350 Aquatic invertebrate life cycle (estuarine/marine)5 o 850.1500 Fish full life cycle (freshwater)

o 850.1790 Whole sediment: chronic invert ebrates freshwater and marine examining survival, growth, and reproduction ( Hyaella azteca

, Chironomus dilutus or C. tentans , and Leptocheirus plumulosus are the required species)

o 850.2100 Avian oral toxicity (Passerine only)

o 850.4100 Seedling emergence, Tier II

o 850.4150 Vegetative vigor, Tier II

• Please refer to Registration Review – Prelimi nary Problem Formulation for Ecological Risk, Environmental Fate, and Endangered Species Assessments for Linuron (PC Code 035506; DP Barcode D375455) , dated April 2, 2010, located in docket EPA-HQ-OPP-2010-0228 on the internet at www.regulations.gov , for a detailed discussion of the anticipated eco logical risk assessment and data needs.

Human Health Risk:

• Human health risk assessments for li nuron were conducted in support of the 1995

Linuron RED and the 2002 Linuron TRED.

• The most recent human health risk a ssessment for linuron was conducted in 2008 to support a Section 18 Emergency Exemp tion for use on lentils in Washington

and Idaho.

• A drinking water exposure assessment was conducted in 2001 for linuron use on carrots in California. A drinking wate r exposure assessment for three linuron metabolites was conducted in 2002, also in support of linuron use on carrots in

California.

• U.S. tolerances for linuron, located in 40 CFR 180.184, are currently expressed in

terms of “linuron and its metabolites convert ible to 3,4-dichloroaniline, calculated as linuron.” During registration review , the Agency anticipates revising the residue definitions for plant commodities and for livestock commodities to include linuron and certain metabolites, in conjunction with the development of an improved enforcement method that is compound specific and more sensitive.

• Additional residue data for sweet corn have been submitted to the Agency in response to the linuron TRED Data Call -In (DCI). The Ag ency anticipates reviewing these studies du ring registration review.

• The Agency anticipates conducting new occupational handler and occupational postapplication exposure risk assessmen ts, including the establishment of a revised Re-Entry Interval (REI) cons istent with current policies, during registration review.6 • The Agency also anticipat es conducting new drinking water and dietary (food and water) exposure risk assessments during registration review to incorporate new field trial data. In conjunction with a pending review of proposed new uses, the Agency anticipates conducting a new a ggregate exposure risk assessment for

linuron.

• The toxicity database is complete with the exception of the following guideline studies, which the Agency anticipates re quiring in order to conduct the planned human health risk assessments during the registration review of linuron:

○ 870.3200 21/28-Day Dermal Toxicity

○ 870.3465 90-Day Inhalation Toxicity (only 28 days required)

○ 870.6200 Neurotoxicity Battery, Ac ute and Subchronic Studies

○ 870.7800 Immunotoxicity

• Please refer to Linuron: Human Health Assessme nt Scoping Document in Support of Registration Review , dated April 1, 2010

, and the Linuron: Addendum to the Human Health Assessment Scoping Docume nt in Support of Registration Review, dated May 28, 2010 located in docket EPA-HQ-OPP-2019-0228 on the internet at www.regulations.gov , for a detailed discussion of the anticipated human health

risk assessment and data needs.

Other Anticipated Data Needs:

• Guideline # 830.7050 UV/Visible Light Absorp tion – this study is a new data requirement under 40 CFR part 158 (Produc t Chemistry Data Requirements) for registration of a pesticid e (food and non-food uses). The Agency anticipates requiring this study to obtain basi c information a bout the compound’s identity/composition and the wavelengths at which the compound may be susceptible to photochemical degradation.

Endocrine Disruptor Screening Program :

As required under FFDCA section 408(p) , EPA has developed the Endocrine Disruptor Screening Program (EDSP) to dete rmine whether certain substances (including pesticide active and other ingred ients) may have an effect in humans or wildlife similar to an effect produced by a “natur ally occurring estrogen, or othe r such endocrine effects as the Administrator may designate.” The ED SP employs a two-tiered approach to making the statutorily required determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a chemical substa nce to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 screening and are found to have the potential to inte ract with E, A, or T hormonal systems will proceed to the next stage of the EDSP wher e EPA will determine which, if any, of the Tier 2 tests are necessary based on the avai lable data. Tier 2 te sting is designed to identify any adverse endocrine related eff ects caused by the substance, and establish a quantitative relationship between the dose and the E, A, or T effect.7 Between October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 chemicals, which c ontains 58 pesticide ac tive ingredients and 9 inert ingredients. This list of chemicals was selected based on the potential for human exposure through pathways such as food and wa ter, residential activity, and certain postapplication agricultural s cenarios. This list should not be construed as a list of known or likely endocrine disruptors.

Linuron is among the group of 58 pesticide ac tive ingredients on th e initial list to

be screened under the EDSP. For information on the status of the or ders issued under the EDSP for each chemical, please visit our website at http://www.epa.gov/endo/ and click

on the "Status of EDSP Orders/DCIs" in the Highlights Box. Additional information on the EDSP, including the policies and procedures , the list of 67 chemicals, the test guidelines and the Tier 1 sc reening battery, can also be found at the EDSP website.

Timeline :

The projected timeline for the completion of the linuron registration review is presented in Table 1.

Table 1. Projected Linuron Registration Review Timeline Activity Estimated Date Opening the docket Open Registration Review Docket and Open Public Comment Period 2010 June

Close Public Comment 2010 August Case Development Develop Final Work Plan (FWP) 2010 December Issue Data Call-In (DCI) 2011 July – September Data Submission 2013 July – September Complete Preliminary Risk Assessments and Open Public Comment Period 2015 January – March

Close Public Comment Period 2015 April – June Registration Review Decision Develop Proposed Registrati on Review Decision and Open Public Comment Period 2015 July – September

Close Public Comment Period 2015 October –

December Complete Final Registrati on Review Decision and Begin Post-Decision Follow-up 2016

Total (years) 6

Summary of Comments and Agency Responses :

The linuron registration review docket was open for a 60-day comment period beginning on June 23, 2010. During the comment period, multiple comments were received. Some of the comments received pr ompted changes in the linuron work plan.8 Comments received regarding data requirements and comments received that necessitated changes to the work plan are summarized below. Please see Linuron. Response to Public Comments on Registration Review Preliminary Workplan , dated October 1, 2010,

and Response to Comments on the Registra tion Review – Pre liminary Problem Formulation for Ecological Risk, En vironmental Fate, and Endangered Species Assessments for Linuron , dated November 23, 2010, located in docket EPA-HQ-OPP2010-0228 on the internet at www.regulations.gov , for EPA’s responses to other

comments received.

This document finalizes the work plan for the linuron registration review process.

Comments by the Physicians Committee fo r Responsible Medicine (PCRM) [EPA-HQOPP-2010-0228-0008]

Comment 1: PCRM would like EPA to use Orga nisation for Economic Co-operation and Development (OECD) guideline for acute avia n oral toxicity, whic h is on the verge of adoption by OECD.

Response 1: The Agency requires a toxicity test be conducted to estimate the acute oral LD50 of linuron to passerine species. P CRM recommends that the new OECD test guideline be used for this test because it uses considerably fewer animals than the traditional LD50 test described by Test Guideline 850.2100. The new OECD test guideline for measuring avian acute oral toxicity with a sequential dosing procedure is Test Guideline (TG) 223. Current po licy within the Office of Pesticide Programs/Environmental Fate and Effects Di vision (EFED) regarding the acceptance of avian acute effects studies conducted using th e TG 223 protocol states the following:

Until the OECD TG 223 validation process is completed and the guideline has been approved by OECD, studies that utilize this guideline should not be classified; pending results of the valida tion, they may then be classified as ‘acceptable,’ assuming that they meet all other guideline requirements.

To date the OECD has adopted the TG 223 gui deline and has issued a validation report. At this time, EFED is actively evaluating th e results of the OECD validation report to determine if the TG 223 effects endpoints and dose/response information adequately address the purposes of the avian acute oral da ta requirement as described in 40 CFR Part 158. Until the Agency has completed its evalua tion of that validati on report, EFED will not classify avian toxicity studies performed using the OE CD TG 223 protocol and the studies cannot be used to fulfill OPP data requi rements. Therefore, we cannot say at this time whether or not avian toxicity studies completed following TG 223 will be acceptable to meet our data requirements.

Validation work conducted on TG 223 to date ha s been limited to st udies with the upland game birds (e.g., northern bobwhite). Because to date this TG 223 has not been validated for passerine species, it is doubtful that we would accept studies done under this9 guideline for fulfilling requirements for passeri ne acute toxicity data until additional validation work with passerines is completed.

Comment 2: PCRM recommends that the Agen cy resolve residual uncertainties regarding the 21/28-day Dermal Toxicity study (GLN 870.3200) by in vitro or in vivo
percutaneous means.

Response 2: The Agency appreciates the expresse d concern and agrees with PCRM that unnecessary animal sacrifice should be minimized. However, in vivo studies provide results for assessing the systemic effe cts in a living animal. Therefore, in vivo testing remains the Agency’s current criteria for testing and affirming dermal toxicity.

Comment 3: PCRM would like clarification on the data requirement for inhalation toxicity based on a discrepancy in the antic ipated data needs section of the Summary

Document.

Response 3: The Agency would like to clarify that, based on exposure duration, the 28- day inhalation study is the only study requi red, not a 90-day inhalation study or both

studies.

Comments by the FIFRA Endangered Species Task Force (FES TF) [EPA-HQ-OPP2010-0228-0008]

Comment 1: The FIFRA Endangered Species Task Force (FESTF) submitted a comment that the Agency should ensure any company w ho is a technical registrant for linuron, but not a member of the FESTF (or a company ha ving met its data compensation obligations) provide a formal offer-to-pay to FESTF in conjunction with their support of the active ingredient.

Response 1: The Agency thanks FESTF for its comment and will consider this information as it completes the endangered species assessment and makes its registration

review decisions.

Comments by Tessenderlo Kerley, In c. (TKI) [EPA-HQ-OPP-2010-0228-0009]

Comment 1: TKI provided information on the use and usage of linuron.

Response 1: The Agency will ensure that the assessments conducted for the registration review of linuron will incorporate only currently registered use sites and formulations. The Agency thanks TKI for its assist ance in clarifying that information.

Comment 2: TKI submitted comments on the linuron SLUA and stated that linuron is not registered for use on almonds, cabbage, onions , oranges, green peas, sweet corn, and tomatoes. TKI believes the treatment information for these crops is incorrect.10 Response 2 : The Agency updated the SLUA with new data and these crops continue to show up in the updated version, possibly due to factor(s) including, but not limited to, usage from when the crop(s) did appear on la bels, illegal usage, experimental usage, misreporting, etc. In the updated SLUA, th e Agency has marked these “currently-notregistered” crops with plus signs to denote th at these crops, which do not appear to have section 7, special local needs, or section 18 re gistrations according to our records. Please refer to the updated SLUA, dated Se ptember 13, 2010, in the linuron docket.

Comment 3 : TKI submitted two attachments summarizing current approved and typical use patterns for linuron. In a ddition, TKI stated that linuron is not registered for use on sweet corn (see comment 2 above).

Response 3 : The Agency concurs with TKI about sweet corn use not being listed on an active linuron registration. The most current linuron label (66330-218) in question, dated September 23, 1999, does not have sweet corn listed on the product label. The Agency did not find any Section 18 registra tions in a database review.

Comment 4 : TKI submitted a comment stating that there are no Section 3 linuron products currently registered for use on lentils.

Response 4 : The Agency concurs with TKI’s st atement. However, there are multiple active linuron lentil Section 18 registrations for control of dog fennel and prickly lettuce in Idaho and Washington state.

Comment 5: TKI commented on the use of the da phnid acute toxicity studies and the acute-to-chronic ratio (ACR) de termination. TKI requests the Agency reconsider the use of the chronic daphnid study in conducting its risk assessments. Specifically, TKI believes the Agency’s approach to determini ng the acute-to-chronic ratio is flawed and that the Agency should disregard th e earlier acute daphnid toxicity study.

Response 5: The Agency notes the following:

• MRID 43996501 is an acceptable acute daphni d toxicological study that fulfills the guideline requirement for an acute freshwater invertebrate study

• MRID 42153401 is an acceptable chronic daphnid toxicological study that fulfills the guideline requirement for a freshwater invertebrate life cycle test

Because the daphnid acute toxicity study (MRID 00142932) is the most sensitive and scientifically sound endpoint, the acute EC50 from this study will continue to be used in the risk assessment. The Agency encourages TKI to submit any additional information or evidence addressing the quality parameters and/or test substance that could inform the

linuron hazard database.

The Agency has determined that although th e daphnid life cycle toxicity study is an acceptable guideline study, it will not serve as the sole basis for establishing a chronic invertebrate endpoint for use in risk assessm ent because the chronic value (derived from11 MRID 42153401) is inconsistent with the acu te toxicity value (derived from MRID 00142932) for daphnia. A new freshwater invert ebrate lifecycle study is not requested.

Comment 6: TKI believes the Agency should use the sheepshead minnow data (MRID 43996502) for freshwater early lifestage instead of surrogate phenylurea herb icide data, and that there is no difference between fresh and saltwater species for risk assessment purposes.

Response 6: The Agency believes the weight of evidence shows there may be differences between saltwater fish and freshwater fish species based on acute LC50 data from freshwater and saltwater fish. The Agency used surrogate phe nylurea herbicide data for risk assessment purposes instead of sheepshead minnow data (MRID 43996502) because of the low number of replicates in the study. Other available data are in sufficient for risk assessment purposes. If acceptable chronic aquatic toxico logical data for linuron are submitted, the Agency may reconsider this approach.

Comment 7: TKI submitted comments on the majority of the studies proposed to be required in the linuron registra tion review data call-in.

Response 7: A summary of TKI’s comments and EP A’s responses is presented below in

Table 3.

Table 3. Summary of TKI Comments on An ticipated Linuron Data Requirements and EPA Response

Guideline Number TKI Comment EPA Response

830.7050 UV/Visible light absorption TKI states that DuPont previously submitted a study to satisfy this data requirement and requests that the Agency review this study prior to issuing a DCI for these data. The Agency than ks TKI for the

comment and will review the submitted study to address the study acceptability in fulfilling the current data requirement prior to issuing the DCI. 835.1230 Leaching and adsorption/desorption The Agency did not require the

submission of these data in the Summary Document although it was identified as a data gap in the

Problem Formulation. TKI provided additional information on previously submitted studies. TKI

believes these studies should provide EPA with the transport data it had previously requested in

the linuron RED and mentioned again in the Preliminary Problem

Formulation document and no further data should be required. The Agency has removed this data requirement from the linuron work plan based on the information submitted by TKI. A new leaching and adsorption/desorption study is no longer required based on a review of information submitted by TKI.

835.2410 Photodegradation in soil TKI provided additional

information and calculations on two soil photodegradation studies previously submitted by DuPont. TKI believes the second study (MRID 4171701) fulfills the data The Agency has removed this data requirement from the linuron work plan. Based on submitted calculations, MRID 40171701 is upgraded to acceptable and a new soil photodegradation study is no longer required based on calculations12 requirement, should be used for the environmental fate, ecological, and endangered species risk assessments, and no additional data should be required. submitted by TKI.

835.4100 Aerobic soil

metabolism TKI commits to conducting a new aerobic soil metabolism study as requested by the Agency. Acknowledged.

835.4200 Anaerobic soil

metabolism TKI commits to conducting a new anaerobic soil metabolism study as requested by the Agency. Acknowledged.

835.4300 Aerobic aquatic

metabolism TKI commits to conducting a new aerobic aquatic metabolism study as requested by the Agency. Acknowledged.

835.4400 Anaerobic aquatic metabolism TKI provided additional information on a study (MRID 40142501) previously submitted by DuPont and requested that the Agency reconsider its requirement for a new study. TKI believes the existing study provides sufficient

information to conduct a risk

assessment. The Agency has removed this data requirement from the linuron work plan. The Agency concur s with TKI that MRID 40142501 provides sufficient

information to characterize the soil mobility of linuron degradates and that a new anaerobic aquatic metabolism study is no longer required.

835.6100 Terrestrial field dissipation TKI has reserved comment on this data requirement until the Agency completes a science review and

rebuttal to information TKI submitted to the Agency in response to the 2004 linuron

TRED. Acknowledged.

850.1035 Estuarine/

marine invertebrate acute toxicity using TEP (Mysid is the preferred species)

850.1055

Estuarine/marine invertebrate acute toxicity using TEP (Eastern Oyster is the preferred species) TKI states that linuron is not expected to enter into

marine/estuarine environments because its rights-of-way uses are very limited and linuron is not widely used in these areas. As such, TKI does not believe that acute toxicity to saltwater

invertebrates is warranted. TKI intends on submitting additional, more detailed, information to the Agency addressing these data requirements in the near future. The Agency has removed these data requirements from the linuron work plan. The Agency concurs with TKI and

these estuarine/marine invertebrate acute toxicity studies are no longer required

because the maximum EECs do not trigger the TEP data requirement.

850.1350 Aquatic invertebrate life cycle (estuarine/marine) TKI states the existing data for

linuron do not indicate a significant difference in marine to freshwater sensitivity. TKI does

not believe a new marine invertebrate study is warranted

based on the additional

information submitted for the chronic daphnid study. An estuarine/marine invertebrate life cycle study is needed because chronic exposure is likely to occur based on linuron’s Rights-Of-Way uses and linuron’s persistence in the environment.

850.1400 Fish early life stage (freshwater) TKI agreed to conduct a new freshwater fish early life stage study as originally requested by A fish early life stage study on freshwater fish is no longer required. The Agency has removed this data13 the Agency. requirement from the linuron work plan.

850.1500 Fish full life cycle (freshwater & estuarine/marine) TKI does not believe there is

sufficient evidence that marine species are more sensitive to linuron than freshwater species. TKI requests that the Agency reserve these data requirements

until after the data from the freshwater fish early life stage toxicity study is complete. TKI intends on submitting additional, more detailed, information to the Agency addressing this requirement in the near future. The fish full life cycle studies (freshwater/estuarine/marine) are required. The Agency notes the acute data demonstrates toxicity differences

between saltwater and freshwater fish species. The Agency needs these data to complete the planned risk assessments

for linuron based on an evaluation of linuron’s use pattern, mobility, potential reproductive effects in fish and birds,

and the EEC.

850.1790 Whole

sediment: chronic

invertebrates freshwater and marine examining survival, growth, and reproduction ( Hyaella

azteca

, Chironomus

dilutus or C. tentans and, Leptocheirus plumulosus ) TKI states that they do not believe that rights-of-way uses are of consequence and new information would not provide new

information for the risk

assessment. Based on the criteria in 40 CFR 158, the parameters in the acute daphnid, aerobic soil and aquatic metabolism studies trigger the need for the whole sediment chronic toxicity data. The Agency acknow ledges that TKI plans to submit additional information to the Agency to address these study requirements. However, these studies remain as data requirements.

850.2100 Avian oral toxicity (Passerine only) TKI commits to conducting a new avian oral toxicity (passerine species) study as requested by the Agency. Acknowledged.

850.4100 Seedling emergence, Tier II TKI commits to conducting a new seedling emergence study as requested by the Agency. Acknowledged.

850.4150 Vegetative vigor, Tier II TKI commits to conducting a new vegetative vigor study as requested by the Agency. Acknowledged.

870.3200 21/28-Day dermal toxicity TKI commits to conducting a new 21/28-Day dermal toxicity study as requested by the Agency. Acknowledged.

870.3465 90-Day inhalation toxicity (only 28 days required) TKI indicates that a 2-week inhalation study was previously submitted to EPA by DuPont. TKI acknowledges that the 2-week study does not contain all the testing parameters in the current subchronic inhalation toxicity study protocol, but believes this study provides adequate scientific

information to conduct a risk

assessment. The Agency is in the process of reviewing the 2-week inhalation study to determine whether the parameters are

sufficient for the needs of the human health risk assessment. Until the Agency makes this determination, the 28-day inhalation toxicity study remains to be a data requirement.

870.6200 Neurotoxicity battery, acute and

subchronic studies TKI commits to satisfying these data requirements. Acknowledged.

870.7800 Immunotoxicity TKI commits to conducting a new immunotoxicity study as requested by the Agency. Acknowledged.14 Comment 8: TKI submitted a number of comments regarding the details of the toxicity

values and/or concentrations in various EFED studies including: the freshwater fish acute toxicity study, the freshwater fish early life stage study, the acute estuarine/marine invertebrate study, freshwater diatom study, and the acute and chronic data referenced in Appendix B of the EFED “Preliminary Pr oblem Formulation for Ecological Risk, Environmental Fate, and Endangered Speci es Assessments for Linuron (PC Code 035506; DP Barcode D375455).”

Response 8: Specific responses to each comment toxi city value/concentration have been

addressed in detail in Linuron. Response to Public Comments on Registration Review Preliminary Workplan , dated October 1, 2010, and Response to Comments on the Registration Review – Preliminary Probl em Formulation for Ecological Risk, Environmental Fate, and Endangered Species Assessments for Linuron , dated November 23, 2010, located in docket EPA-HQ- OPP-2010-0228 on the internet at www.regulations.gov

.

Next Steps :

The Agency plans to issue a DCI for linur on in 2011 for the data gaps listed under

the Risk Assessment and Data Needs section of this document. The information received in response to this DCI will be used to c onduct the planned human health, ecological, and endangered species risk assessments for linuron.