Page 2 of 27

A. PHYSICIANS COMMITTEE FOR RESPONSIBLE MEDICINE (PCRM)

COMMENTS:

1. PCRM Comment:

“The Summary Document indicates that the Agency may request testing for avian acute oral 

toxicity. We strongly support the use of the newly revised OECD Test Guideline 223 for the 

acute avian oral toxicity test...”

EFED Response:

To date the OECD has adopted the TG 223 guideline and has issued a validation report. At this 

time EFED is actively evaluating the 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 data requirement as described in 40 CFR Part 158. Until the Agency‟s 

evaluation of that validation report is completed, EFED will not classify avian toxicity studies 

performed using the TG 223 protocol and the studies cannot be used to fulfill current data 

requirements. 

2. PCRM Comment:

“In response to past comments on the avian acute oral toxicity test... „EPA is not likely to accept 

studies conducted under the OECD guideline unless additional study validation is conducted for 

passerine species (from EFED Response to Comments on Preliminary Work Plan for Sodium 

Acifluorfen)‟... If the Agency is interested in collecting all data in consideration of the use of the 

223 then it should not state that it will not accept information gathered according to this 

protocol.”

EFED Response:

EFED will consider all data submitted regarding the potential toxicity of pesticides. In reading 

through the previous Agency response, we understand how the sentence „EPA is not likely to 

accept studies conducted under the OECD guideline...” could be misunderstood. To clarify 

what was meant, the Agency will not be able to classify studies conducted using TG223 and 

passerines as „acceptable‟ (and, thus, fulfilling guideline requirements) until it is verified that the 

OECD TG 223 using passerines adequately addresses the purposes of the passerine acute oral 

data requirement as described in 40 CFR Part 158.

2. PCRM Comment:

“... (T)he EFED document was not in the docket despite the final work plan stating it should be; 

this is also true for Hymexazol... Can this be checked so that we may access these documents?”
Page 3 of 27

EFED Response:

EFED was able to access the EFED Registration Review Problem Formulation for Cyfluthrin 

and Beta-cyfluthrin in the public docket (Document ID: EPA-HQ-OPP-2010-0684-0004) 

(Docket ID: EPA-HQ-OPP-2010-0684).

B. CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD – CENTRAL 

VALLEY REGION (CRWQCB-CVR) COMMENTS:

1. CRWQCB-CVR Comment:

“...(T)he current Clean Water Act Section 303(d) list for California... has 3 listings for 

pyrethroids in the Central Valley Region... The 2010 303(d) list contains an additional 10 

streams in the Central Valley which are exceeding water quality standards due to levels of 

pyrethroids in sediments.”

EFED Response:

EFED will include relevant information on 303(d) listings in the final environmental risk 

assessment. The preliminary EFED problem formulation for cyfluthrin and β-cyfluthrin reflects 

the current list of 303(d) impaired water bodies. The list with the 10 additional bodies of water 

identified as impaired due to pyrethroids has not been finalized, and, therefore, was not included 

in the problem formulation. 

2. CRWQCB-CVR Comment:

“While these pyrethroid-impaired streams are all in the Sacramento Area, there is no indication 

that pyrethroid concentrations are different in other urban areas in California. A statewide 

investigation by Holmes et al. (2008) showed pyrethroids present at toxic levels in benthic 

sediments... throughout California.”

EFED Response:

This study was included in the „Open Literature Information‟ appendix (Appendix C) in EFED‟s 

preliminary problem formulation for cyfluthrin and β-cyfluthrin. Information from the study will 

be considered when conducting the environmental risk assessment for the cyfluthrins.

3. CRWQCB-CVR Comment:

“A recently published study of sources of pyrethroid pesticides to the Delta (Weston and Lydy, 

2010) examined pyrethroids in urban runoff, municipal wastewater treatment plants and 

agricultural drains discharging to the Delta. Nearly all urban runoff samples were toxic to 

Hyalella azteca due to pyrethroids, particularly bifenthrin and cyfluthrin.” 
Page 4 of 27

EFED Response:

The article by Weston and Lydy (Weston and Lydy, 2010) was included in EFED‟s preliminary 

problem formulation and considered in making decisions on data requirements for cyfluthrin and 

β-cyfluthrin. 

4. CRWQCB-CVR Comment:

In response to the impairments identified in Weston and Lydy (2010), “... as required by the 

Clean Water Act, the Central Valley Water Board will soon be developing TMDLs to address 

cyfluthrin and other pyrethroids of concern... The Central Valley Water Board, and the 

dischargers we regulate, must direct considerable resources to our ongoing efforts to address the 

water quality impairments associated with current-use pesticides that impact water quality such 

as diazinon, chlorpyrifos, and now pyrethroids... In many ways, pollution prevention through 

effective regulation of pesticide use would be much more efficient and effective than the 

regulatory options available to water control agencies implementing the Clean Water Act.”

EFED Response:

EFED defers a specific response to this comment to OPP‟s Pesticide Re-evaluation Division 

(PRD) since it relates directly to risk management, labeling, and product registrations. 

5. CRWQCB-CVR Comment:

“As part of our TMDL development efforts, the Central Valley Water Board recently funded 

researchers as UC Davis to develop ambient water quality criteria for cyfluthrin. The resulting 

final criteria document... which is attached... should be useful to USEPA in this registration 

review.”

EFED Response:

The Agency appreciates the submission of this document and will consider it in the risk 

assessment conducted for cyfluthrin and β-cyfluthrin as part of the Registration Review process.

C. CALIFORNIA STORMWATER QUALITY ASSOCIATION (CASQA) COMMENTS:

1. CASQA Comment:

CASQA appreciates “... EPA‟s consideration of non-agricultural sources and exposure pathways 

in the proposed updated ecological risk assessments for cyfluthrin and beta-cyfluthrin. However,

EPA‟s proposed approach should more explicitly account for urban sources of these pesticides, 

including specifically outdoor applications to both landscaped and impervious surfaces.”

EFED Response:
Page 5 of 27

EFED is currently further exploring methods to assess urban and residential uses on a national 

basis. EFED will consider comments regarding the need to include models that consider 

transport of runoff from impervious surfaces and stormwater drainage systems while it develops 

these methodologies. At the present time, EFED considers the use of the impervious scenario (a 

Pesticide Root Zone Model (PRZM) modeling scenario) as the most suitable available modeling 

approach for impervious runoff and has used this approach for some assessments completed for 

Endangered Species in California. The PRZM impervious scenario may be used in the tier 2 

coupled aquatic models PRZM/Exposure Analysis Modeling System (EXAMS) along with a 

residential or other suitable scenario such as rights-of-way (ROW) to obtain Estimated 

Environmental Concentrations (EECs). The conceptual model for the residential scenario 

integrates simultaneous modeling of the individual use scenario with an impervious scenario. 

This approach assumes that no watershed is completely covered by either the 1⁄4 acre lot (the 

basis for the residential scenario) or undeveloped land (the basis for the ROW scenario) for 

residential and ROW use patterns; therefore, differential amounts of runoff will occur within the 

watershed. The impervious scenario was developed to represent the paved areas within a 

watershed not including roads, parking lots, sidewalks, and buildings outside the 1⁄4 acre lot (the 

1⁄4 acre lot scenario accounts for impervious surfaces such as buildings within the represented

area). By modeling a separate scenario for impervious surfaces, it is also possible to estimate 

that amount of exposure that could occur when the pesticide is oversprayed onto this surface. 

Using two scenarios in tandem requires post-processing of the modeled output in order to derive 

a weighted EEC that represents the contribution of both the pervious (i.e., residential and ROW 

scenarios) and the impervious surfaces. Exposure from both scenarios can also be weighted and 

aggregated. The daily time series from each model run from the times series file 

(NAME_TS.out) generated from the PRZM graphical user interface (PE5.pl) residential and 

impervious surface scenarios are combined using Microsoft EXCEL. The time series data are 

weighted based on percentage of impervious surface, the percentage of the pervious surface 

treated, and an adjusted time series is created. Rolling averages for the relevant durations of 

exposure (e.g., 21 day and 60 day averages) are calculated, and the relevant one-in-ten year EEC 

is generated from these distributions.

The Agency intends to use available non-agricultural use and usage data, such as the Kline 

database, the California Department of Pesticide Regulation‟s (CDPR) Pesticide Use Reporting 

Data and Pest Control Operator‟s usage survey, and the Residential Joint Venture Task Force 

homeowner survey data (2003), to make certain reasonable assumptions regarding various 

applications and information related to urban/residential use. Due to the limited data available, 

exposure to the environment and uncertainties will be characterized. Detailed information on 

non-agricultural use and usage of pyrethroid products, specifically cyfluthrin and β-cyfluthrin, 

would be useful in order to reduce those uncertainties for the final environmental risk assessment 

for cyfluthrin and β-cyfluthrin.

2. CASQA Comment:

“Water quality impacts must be prevented through use restrictions.”
Page 6 of 27

EFED Response:

EFED defers a specific response to this comment to OPP‟s PRD since it relates directly to risk 

management, labeling, and product registrations. 

3. CASQA Comment:

“The conceptual models must explicitly include urban sources.”

EFED Response:

A revised conceptual model that includes urban sources (specifically impervious surfaces) will 

be included in the risk assessment conducted for cyfluthrin and β-cyfluthrin as part of the 

Registration Review process.

4. CASQA Comment:

“Modeling of non-agricultural sources must use an urban runoff model.”

EFED Response:

See the response to C.1. above.

5. CASQA Comment:

“Most cyfluthrin use in California is urban...” and is applied by professional applicators.

EFED Response:

The use/usage information will be considered in the risk assessment conducted for cyfluthrin and 

β-cyfluthrin as part of the Registration Review process, especially as it relates to the 

urban/residential portion of the risk assessment.

6. CASQA Comment:

“The risk assessment must consider cumulative impacts.”

EFED Response:

EFED is continuing to explore ways in which cumulative effects could be accounted for in our 

ecological risk assessments.

7. CASQA Comment:

“The registration process must effectively prevent water quality impacts.”
Page 7 of 27

EFED Response:

EFED defers a specific response to this comment to OPP‟s PRD since it relates directly to risk 

management, labeling, and product registrations. 

8. CASQA Comment:

The risk assessment should “...(e)valuate exposures in both water column and sediments.”

EFED Response:

As stated in the preliminary problem formulation, sediment and water column exposures will be 

evaluated as part of the risk assessments conducted for cyfluthrin and β-cyfluthrin.

9. CASQA Comment:

“The NPDES monitoring data... are submitted to the State of California through the NPDES 

permitting system. We recommend that EPA contact the California State Water Resources 

Control Board for this data. We also recommend that EPA contact the California Department of 

Pesticide Regulation (DPR) for related information... We suggest that it is incumbent upon EPA 

to take a more active role in identifying and acquiring pertinent monitoring data.”

EFED Response:

All readily available or submitted monitoring data will be considered in the environmental risk 

assessment.

D. CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD – SAN 

FRANCISCO BAY REGION (CRWQCB-SFBR) COMMENTS:

1. CRWQCB-SFBR Comment:

“Pesticides that are applied per label instructions often pollute urban streams, largely because the 

pesticides runoff impervious surfaces during rain or irrigation events. In the long run, we request 

that the U.S. EPA develop tests and thresholds for washoff of pesticides from impervious 

surfaces...”

EFED Response:

As discussed in response C.1. above, EFED is currently developing methodologies to examine 

runoff from impervious surfaces on a national basis. EFED will consider these comments as 

these methods are developed.

2. CRWQCB-SFBR Comment:

“The Work Plan‟s problem formulation does not recognize cyfluthrin transport via urban runoff 

to surface waters of the United States.”
Page 8 of 27

EFED Response:

Please see the response to C.1. above.

3. CRWQCB-SFBR Comment:

“Based on available monitoring data..., we can readily conclude that urban runoff contains 

cyfluthrin that has been washed away from treated surfaces during rain events and cleaning 

operations, and by irrigation overflows. The risk hypothesis and conceptual model do not 

recognize cyfluthrin applications to impervious surfaces.”

EFED Response:

Please see the responses to C.1. and C.3. above.

4. CRWQCB-SFBR Comment:

“We request that EPA examine both professional and non-professional cyfluthrin urban use... at 

a level of detail sufficient to determine which use patterns need modification or cancelation to 

end aquatic toxicity.”

EFED Response:

Please see the response to C.1. above.

5. CRWQCB-SFBR Comment:

“The modeling approaches described are inappropriate for urban runoff and urban watersheds 

because they do not account for the most important factors in urban runoff pollutant transport –

impervious surfaces and storm drainage system design.”

EFED Response:

Please see the response to C.1. above.

6. CRWQCB-SFBR Comment:

“To facilitate Work Plan improvements to assess surface water risks associated with urban 

cyfluthrin use, we have attached two detailed conceptual models linking urban pyrethroid 

application locations to receiving waters.”

EFED Response:

The Agency appreciates the submission of these documents and will consider them in the risk 

assessment conducted for cyfluthrin and β-cyfluthrin as part of the Registration Review process.
Page 9 of 27

7. CRWQCB-SFBR Comment:

“Cumulative risks with other pyrethroids must be evaluated.”

EFED Response:

Please see the response to C.6. above.

8. CRWQCB-SFBR Comment:

“All data necessary for a scientifically sound environmental risk assessment should be 

requested/reviewed...” including data for sensitive saltwater species (Americamysis bahia), 

chronic sediment toxicity data for salt water species found in the Western U.S., aquatic toxicity 

data to account for potential increased toxicity in cold water, and data needed for urban exposure 

assessments. 

“This list should be reviewed in light of available data from the open scientific literature and 

from studies required by California Department of Pesticide Regulation (DPR), as some of the 

needed data may already be available or be forthcoming.”

EFED Response:

Acceptable toxicity data using A. bahia are available for cyfluthrin and will be used in the 

cyfluthrin risk assessment. EFED currently recommends the use of the estuarine/marine 

amphipod, Letptocheirus plumulosus, for assessing chronic toxicity of pesticides in sediments 

because of its long history of development with EPA and by other Agencies (U.S. Army Corps 

of Engineers). Currently, L. plumulosus is the only estuarine/marine test species for which 

chronic sediment toxicity testing has been validated for use in the Agency1. Although L. 

plumulosus is distributed along the east coast of the United States, available literature indicates it 

has similar sensitivity as E. estuarius, H. azteca and Ampelisca abdita.2 Furthermore, the 

Agency will consider results from other test species provided they are scientifically defensible 

and appropriate for use in the Agency‟s forthcoming risk assessment. 

 

1

USEPA/USACE. 2001. Method for Assessing the Chronic Toxicity of Marine and Estuarine Sediment-associated 

Contaminants with the Amphipod Leptocheirus plumulosus. First Edition. EPA EPA 600/R-01/020. March 2001

2 DeWitt, T.H., B.L. McGee, R. Alden, H. Phelps, and A. Pinkney. 1992. A multi-species, multi-lab comparison of 

the toxicity of a Chesapeake Bay sediment. Presented at the Thirteenth Annual Meeting of the Society for 

Environmental Toxicology and Chemistry, Cincinnati, OH, November 8-12.

McGee, B.L., C.E. Schlekat, and E. Reinharz. 1993. Assessing sublethal levels of sediment contamination with the 

estuarine amphipod, Leptocheirus plumulosus. Environ Toxicol. Chem. 12:577-588.

SAIC. 1993a. Draft data report on comparative sensitivity of four amphipod species to sediment associated 

contaminants. Submitted to USEPA. EPA contract No. 68-CO-0044. Prepared by Science Applications International 

Corporation, Narragansett, RI. 15 pp.
Page 10 of 27

EFED acknowledges the documented negative correlation of the toxicity of pyrethroids with 

temperature (e.g., Weston et al. 2009 and Hardwood et al. 2009).3 EFED will consider available 

and submitted literature on the temperature effects on pyrethroid toxicity as part of its 

forthcoming risk assessment. EFED will take into account this factor in its characterization of 

risk (e.g., potentially as part of a sensitivity analysis).

EFED will consider all submitted studies and available open literature information while 

conducting its environmental risk assessment.

9. CRWQCB-SFBR Comment:

“Cyfluthrin in POTW effluent can be transferred to biosolids. The Work Plan should evaluate 

potential impacts from the use of pesticides to biosolids land application in cases where downthe-drain assessments indicate that pesticides would partition to biosolids.”

EFED Response:

Discharge of cyfluthrin and/or β-cyfluthrin into the environment via effluent will be considered 

to the best degree possible in the risk assessment. The Agency is actively evaluating the extent 

to which ecological risk from cyfluthrin and β-cyfluthrin via land application of biosolids should 

be addressed in its forthcoming environmental fate and ecological risk assessment, and by 

extension, any additional data that may be required. As part of this evaluation, OPP is working 

closely with the Office of Water which regulates land application of biosolids under the Clean 

Water Act.

10. CRWQCB-SFBR Comment:

“Please plan to obtain data submitted to the DPR under its pyrethroid reevaluation effort...”

EFED Response:

EFED will consider all submitted studies and available open literature information while 

conducting its environmental risk assessment.

11. CRWQCB-SFBR Comment:

“We appreciate U.S. EPA‟s recognition of monitoring information in the open literature. We 

have included a list of additional relevant references as an attachment.”

 

3 Weston, D.P., J. You, A.D. Harwood and M.J. Lydy. 2009. Whole Sediment Toxicity Identification Evaluation 

Tools for Pyrethroid Insecticides: III. Temperature Manipulation. Environ. Tox. & Chem., Vol. 28, No. 1, pp. 173–

180, 2009

Hardwood, A.D., J. You and M.J. Lydy. 2009. Temperature as a Toxicity Identification Evaluation Tool for 

Pyrethroid Insecticides: Toxicokinetic Confirmation. Environ Toxicol & Chem 28 (5) pp. 1051-1058, 2009
Page 11 of 27

EFED Response:

EFED appreciates the list of references provided by the commenter. These references will be 

considered for the environmental risk assessment conducted for cyfluthrin and β-cyfluthrin.

12. CRWQCB-SFBR Comment:

“We do not have separate 303(d) listings for cyfluthrin; rather our 303(d) listings are for all 

pyrethroids. Thus, 303(d) listings are not a perfect indicator of the extent of surface water 

problems associated with cyfluthrin... Because their toxicity is additive, 303(d) listings are being 

made for „pyrethroids‟ as a group rather than for individual pyrethroids...”

EFED Response:

EFED will include relevant information on 303(d) listings in the final environmental risk 

assessment. 

E. TRI-TAC (TT) COMMENTS:

1. TT Comment:

“Tri-TAC supports EPA‟s decision to conduct a down-the-drain assessment for cyfluthrin. TriTAC also supports the decision by the Offices of Pesticide Programs and Water to work together 

to refine the down-the-drain assessments for registration review. Finally, Tri-TAC supports 

EPA‟s decision to request monitoring data and additional aquatic toxicity data from publiclyowned treatment works (POTWs).”

EFED Response:

No response needed.

2. TT Comment:

“This cover letter provides the comments we shared with the bifenthrin docket and requests that 

the workplan for cyfluthrin be modified to address the same issues.”

EFED Response:

The comments from Tri-TAC and the EFED responses for the bifenthrin problem formulation

are available in the registration review docket at www.regulations.gov (Docket ID: EPA-HQOPP-2010-0384). The EFED responses to the Tri-TAC comments on bifenthrin also apply for 

cyfluthrin and β-cyfluthrin. 
Page 12 of 27

F. BAYER CROPSCIENCE (BCS) COMMENTS:

1. BCS Comment:

“The agency has drafted a very thorough conceptual model and broad risk hypotheses, which 

Bayer believes can be more narrowly focused to better correspond to the compounds properties 

and uses. Sufficient information already exists to focus the ERA on arthropods, especially those 

residing in the aquatic environment.”

EFED Response:

Through registration review, EPA is reviewing each registered pesticide every 15 years to 

determine whether it still meets the FIFRA standard for registration. In addition, EPA intends to 

meet its responsibility under the Endangered Species Act in the registration review program. To 

ensure that the use of cyfluthrin and β-cyfluthrin will not adversely impact non-listed and/or 

listed species, a risk assessment involving all of the major taxonomic groups normally assessed 

by EFED will be conducted.

2. BCS Comment:

“Bayer CropScience proposes to conduct an ecological risk assessment for the cyfluthrins taking 

into account the established mitigations listed on product labels, in particular vegetative buffer 

zones and no-spray zones. We strongly recommend that the agency also accounts for these 

existing mitigations in its own risk assessment.”

EFED Response:

Currently EFED has methods to address the potential impacts of vegetative buffers and no-spray 

zones on potential exposures to non-target organisms from spray drift. There are currently no 

approved methods in EFED to address the impacts of buffer strips on runoff. EFED is 

continuously working on improving its risk assessment methods, including how to best address 

the impact of vegetative buffer strips on the estimated exposures to non-target organisms. 

CropLife has evaluated models that incorporate vegetative buffer strip efficiencies and effects on 

runoff. CropLife‟s evaluation will be considered when methods to evaluate the potential for 

vegetative buffers to reduce runoff are developed. EFED will incorporate, to the best of its 

abilities based on the available information and approved methodologies, the application 

restrictions that appear on approved labels at the time of the risk assessment into the exposure 

assessments for the cyfluthrins.

3. BCS Comment:

“Also, any risk assessment should include consideration of all studies available, even when they 

are discounted for legitimate reasons. The transparency that explicit inclusion of all studies 

allows is helpful in supporting weight of evidence approaches along with building confidence in 

the assessment.”
Page 13 of 27

EFED Response:

It is EFED‟s policy to consider all available submitted data and open literature studies relevant to 

the chemical(s) being assessed in our risk assessments. It is also EFED‟s policy to exclude 

information from studies that have been classified as „invalid‟ (i.e., not scientifically valid). It is 

unclear how the inclusion of studies that have been reviewed and found to be invalid would be 

“... helpful in supporting weight of evidence approaches along with building confidence in the 

assessment.” 

4. BCS Comment:

“We plan to submit a risk assessment to the agency at the end of the time period assigned for 

generation of data according to the agency‟s data call-in request.”

EFED Response:

EFED will consider all submitted data in the risk assessment conducted for cyfluthrin and βcyfluthrin. 

5. BCS Comment:

“We specifically ask the agency to consider in their evaluation of the cyfluthrins information 

previously submitted by the Pyrethroid Working Group. For example, in 1997 PWG performed 

an ecological risk assessment for pyrethroid use on cotton (Holmes et al., 1997; Maund et al., 

1997; Ritter et al., 1997; Travis, 1997). While the assessment was performed using cypermethrin 

as a representative pyrethroid, it is very much relevant to the cyfluthrins and the other 

pyrethroids (Dobbs and Maund, 2000).”

EFED Response:

EFED will consider these studies when conducting the risk assessment for cyfluthrin and βcyfluthrin.

6. BCS Comment:

“Bayer CropScience concurs with the agency that the degradates of cyfluthrin, resulting from 

cleavage of the ester bond are significantly less toxic than the parent compound and therefore are 

not stressors of concern for the ecological risk assessment. Additional ecotoxicity studies with 

the degradates, which confirm their lower toxicity, will be submitted by Bayer CropScience.”

EFED Response:

EFED would appreciate (and will consider) additional toxicity data on the cyfluthrin and βcyfluthrin degradates to help confirm the assumption that degradates are less toxic to non-target 

organisms than the parent(s). Such data would help reduce uncertainties associated with 

degradates in the risk assessment conducted for these chemicals.
Page 14 of 27

7. BCS Comment:

Bayer CropScience noted several errors in the pesticide use/usage tables provided in the problem 

formulation.

EFED Response:

EFED appreciates these comments and will consider them when conducting the risk assessment 

for cyfluthrin and β-cyfluthrin. The risk assessment will be based on all approved labels (at the 

time of the risk assessment) for cyfluthrin and β-cyfluthrin. If the potential errors identified by 

BCS are relevant to the use/use patterns for cyfluthrin and β-cyfluthrin at the time the risk 

assessment is conducted, corrections to the use/usage data will be made, if applicable.

8. BCS Comment:

“Bayer CropScience agrees with the agency that the potential for ecological risks associated with 

interactions of cyfluthrin and the synergist PBO are small. Products containing the synergist are 

only registered as indoor aerosol sprays. Coincident exposure of cyfluthrin and PBO in the 

environment is extremely unlikely following indoor use of cyfluthrin products.”

EFED Response: 

EFED will confirm with OPP‟s Registration Division that the only cyfluthrin products that 

contain PBO are products registered for indoor use only and that cyfluthrin products are not 

tank-mixed with PBO when used outdoors. If it is confirmed that no cyfluthrin products with 

outdoor uses are registered at the time of the risk assessment and that PBO is not mixed with 

cyfluthrin products used outdoors, it will be considered in the exposure assessment. 

9. BCS Comment:

“The PWG has commissioned extensive studies of the urban waterways and Bayer CropScience 

asks that EFED consider the work of Hall et al. (2008a,b) in their assessment.”

EFED Response: 

EFED will consider all submitted data in the risk assessment conducted for cyfluthrin and βcyfluthrin. 

10. BCS Comment:

“The agency states that the cyfluthrins exhibit a potential for bioaccumulation in fish in the 

above mentioned documents. In reality, following a drift event, the cyfluthrins rapidly migrate 

from the water column to sediment (as described above) and there is only a short exposure period 

in which uptake to fish can occur. For this reason, the standard fish bioaccumulation testing 

protocol (at least 4 weeks of constant exposure in tanks without sediment) is a conservative 
Page 15 of 27

model for understanding the bioaccumulation potential of these compounds. The available 

information also demonstrate that during the elimination phase (14 days post-exposure) the 

cyfluthrins were rapidly eliminated from fish tissues (Carlisle & Roney, 1984). The cyfluthrins 

show no potential to bioaccumulate in fish.”

EFED Response: 

The problem formulation indicated a potential for bioaccumulation of cyfluthrin, based on its 

physicochemical properties (e.g., a very high K OW ). Cyfluthrin has some of the characteristics 

observed in chemicals that bioaccumulate. The potential for bioaccumulation will be examined 

using the K OW (based) Aquatic Bio-Accumulation Model (KABAM v.1.0), with adjustments for 

biotransformation rates (as indicated in the Section 7.2 of the problem formulation). The 

bioconcentration in fish study indicated a relatively low BCFs of 854x in whole fish (if 

compared to its high log K OW of 5.97), with moderately moderate depuration (~50% between 

≤3). Note that biotransformation rates can vary widely for different species and taxa.4

11. BCS Comment:

“EPA acknowledges that the review of open literature provided in Appendix C is, at this stage, a 

cursory evaluation, and Bayer urges that agency to do a more thorough evaluation. The current 

review gives an incomplete picture of current pyrethroid research... Bayer CropScience 

recommends a more complete evaluation of the open literature that includes an assessment of the 

quality of the research as part of an overall weight of evidence approach.”

EFED Response: 

All submitted studies and studies identified in the open literature using ECOTOX are reviewed 

for acceptability criteria. Those studies determined to be scientifically valid and usable for risk 

assessment purposes will be included in the risk assessment. Additionally, a bibliography 

containing all of the open literature studies (even those that do not pass acceptability criteria) 

will be provided in the risk assessment as an appendix.

12. BCS Comment:

Guideline #835.1230 Mobility Adsorption/Desorption

“Bayer CropScience agrees that a full adsorption/desorption study would provide valuable data 

to reduce uncertainty concerning the extent of adsorption with concentration as described by the 

Freundlich exponent.”

EFED Response:

No response needed.

 

4 DiGiulio, R. T., Benson, W. H., Sanders, B. M., & VanVeld, P. A. 2003. Biochemical Mechanisms: Metabolism, 

Adaptation, and Toxicity. In G. M. Rand (Ed.), Fundamentals of Aquatic Toxicology (pp. 523-560). New York: 

Taylor & Francis.
Page 16 of 27

13. BCS Comment: 

Guideline #835.4100 Aerobic Soil Metabolism

“Bayer CropScience is submitting the study report “Aerobic Soil Metabolism of β-Cyflutrhinphenoxy-1,2,3,4,5,6-14C6 (cyclopropanecarboxylic acid, 3-(2,2-dichloroethenyl)-2,2-diemthyl-, 

cyano(4-fluoro-3-phenoxyphenyl)methylester) in Sandy Loam from Fresno, California (Bayer 

Report M-079875-01-1) which was conducted at the request of the California Department of 

Pesticide Regulation (CDPR). This study will satisfy one of the β-cyfluthrin requirements.

Bayer CropScience agrees to submit an aerobic soil metabolism study in two soils with 

cyfluthrin and at least one of which cyclopropyl –labels, following issuance of the data call-in.

Bayer CropScience intends to submit a new study with β-cyfluthrin on four soils (two European 

soils and two US soils) with either fluorophenyl- or cyclopropyl- labels (at least one with 

cyclcoprorpyl- label), following issuance of the data call-in.”

EFED Response:

EFED will review these studies when they are received and will use all scientifically valid data 

in the risk assessment.

14. BCS Comment:

Guideline #835.4200 Anaerobic Soil Metabolism

“EPA has requested an anaerobic soil metabolism study conducted with cyfluthrin on one soil for 

the evaluation of transformation pathways and three additional soils for rates of transformation 

determination. 

According to the anaerobic soil metabolism study guideline (#835.4200), the test system will be 

flooded and changed to anaerobic condition from aerobic condition at 30 days after treatment (or 

one half-life, whichever comes first). Bayer CropScience has conducted aerobic metabolism 

studies in two soils with cyfluthrin and one soil with β-cyfluthrin. The distribution of cyfluthrin, 

CO2, and bound residues was 60-69%, 6-17%, and 14-17%, respectively, at day 28 after 

treatment, accounting for 89-94% of the applied material (Wagner et al., 1983). The distribution 

of β-cyfluthrin, CO2, and bound residues was 66%, 15%, and 14% respectively, at day 30 after 

treatment, accounting for 95% of the applied material (Aga, 2002). Only one metabolite (PFBacid) was detected at 10% in one soil at day 28, no other metabolites were detected greater than 

5% at 28-30 days. Thus, at the point of converting the anaerobic soil test system from aerobic to 

anaerobic conditions by flooding the systems, the primary residue in the soil will be parent 

cyfluthrin (or β-cyfluthrin). Therefore, at that point the test system will be similar to the 

anaerobic aquatic test system, since in an aquatic system cyfluthrin will partition rapidly into the 

soil/sediment. Bayer CropScience believes the anaerobic aquatic metabolism study is an 

appropriate substitution for the anaerobic soil study (see anaerobic aquatic discussion below).”
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EFED Response: 

Anaerobic metabolism studies are requested in both soil and in aquatic systems because 

degradation rates and pathways can differ in these two environments. Therefore, both studies are 

needed.

15. BCS Comment:

Guideline #835.4300 Aerobic Aquatic Metabolism

“Bayer CropScience agrees to submit an aerobic aquatic metabolism study following issuance of 

the data call-in.”

EFED Response:

No response needed.

16. BCS Comment:

Guideline # 835.4400 Anaerobic Aquatic Metabolism

“Bayer CropScience agrees to submit an anaerobic metabolism study following issuance of the 

data call-in.”

EFED Response:

No response needed.

17. BCS Comment: 

Guideline #s 835.6100 and 6200 Environmental Chemistry Methods and Independent Laboratory 

Validations for Soil, Water, and Sediment

“Bayer CropScience agrees to submit modern mass-spectrometry methods for cyfluthrin in 

water, sediment, and soil. Bayer CropScience also agrees to conduct ILV on these methods. The 

methods will separate the four enantiomeric pairs of isomers, I, II, III, and IV. The quantitation 

of cyfluthrin will be based on the sum of all isomers, and the quantitation of β-cyfluthrin will be 

based on the sum of isomers II and IV. The methods are not intended for data collection in field 

dissipation studies, thus the inclusion of metabolites (FPB-acid, FPB-ald, and DCVA) is not 

necessary due to their low toxicity compared to parent.”

EFED Response: 

At this time, FPB-acid (4-fluoro-3-phenoxybenzoic acid), FPB-ald (4-fluoro-3-

phenoxybenzaldehyde), and DCVA (3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropanecarboxylic 
Page 18 of 27

acid) are not considered residues of toxicological concern; therefore, environmental chemistry 

methods do not need to include these residues for identification. 

18. BCS Comment:

“Regarding multi-residue methods, the Pyrethroid Working Group (PWG) has submitted a multi 

residue method (Robinson, 2007) and ILV (Reed, 2006) for pyrethroids in sediment (bifenthrin, 

cypermethrin, cyfluthrin, deltamethrin, esfenvalerate, fenpropathrin, γ-cyhalothrin and 

permethrin). This method does not distinguish the isomers of the individual pyrethroids.”

EFED Response: 

The multi-residue method will be a valuable tool for monitoring pyrethroids in sediments. The 

method will be reviewed and made available to the public, as appropriate.

19. BCS Comment:

“EPA has requested a study to be conducted according to the American Wood Preservers 

Association Standard Method of Determining the Leachability of Wood Preservatives (E11-06).

Bayer CropScience does not understand the justification for this study since we are not aware of 

any cyfluthrin and β-cyfluthrin products registered for use as wood preservative treatments.”

EFED Response: 

Applications to protect wood from wood-infesting pests are allowed on some labels such as EPA 

registration numbers 432-1363, 432-1377, 432-1483, 11556-124, and 11556-145. Therefore, 

EFED still recommends a study conducted according to the American Wood Preservers 

Association Standard Method of Determining the Leachability of Wood Preservatives (E11-06)

be requested. The method should be amended so that cyfluthrin is applied as specified on labels 

instead of impregnated into the wood. In the absence of data, EFED would assume that 100% of 

cyfluthrin applied to wood surfaces is available for washoff.

20. BCS Comment:

POTW Effluent Monitoring and Treatability Study

“Bayer CropScience is actively involved with the PWG in responding to the re-evaluation of 

pyrethroids by the California Department of Pesticide Regulation (CDPR). A key component of 

the response is to better characterize the risk associated with the detection of pyrethroids in the 

sediment of urban creeks. The PWG will provide updates of effluent monitoring and will 

conduct the treatability study according to a protocol agreed between EPA and PWG.”

EFED Response: 

No response needed.
Page 19 of 27

21. BCS Comment:

Guideline # 850.2100 Passerine Avian Oral (Cyfluthrin)

“While Bayer CropScience believes overall that the existing studies are sufficient to characterize 

the toxicity of the cyfluthrins to birds, we recognize that this study is mandatory and will conduct 

the study as requested. It is unlikely that conducting the passerine study will change the risk 

assessment for the cyfluthrins.”

EFED Response: 

No response needed.

22. BCS Comment:

Guideline # 850.2300 Avian Reproduction Study (Mallard duck only) (Cyfluthrin)

“In addition to the two cyfluthrin mallard reproduction studies (Carlisle, 1984 and Beavers, 

1986) that the agency has in their possession, Bayer has identified an additional mallard 

reproduction study (Beavers et al., 1990) which will be submitted to meet this data request. It 

must be noted that Bayer disagrees with the agencies finding of a lack of a NOAEL based on the 

studies currently in the agencies possession. The three cyfluthrin mallard reproduction 

consistently support a NOAEL of 250 ppm.”

EFED Response: 

EFED looks forward to receiving the data and reviewing them for adequacy and suitability for 

use in risk assessment.

23. BCS Comment:

Guideline # 850.1025/1035 Oyster and Mysid Acute Toxicity (saltwater; cyfluthrin TEP only)

(Cyfluthrin)

“Mollusks are one of the least sensitive taxa to pyrethroids, so additional testing is unlikely to 

influence the aquatic risk assessment. Two studies (Barrows, 1984 and Carr, 1986) examining 

the toxicity of cyfluthrin to the eastern oyster exist. The EC50 values reported by the authors 

were 5 and 3.42 μg/L; slightly different from the value of 2.69 μg/L cited by agency. Bayer 

requests clarification from the agency on this discrepancy. Also Table 7.2 (page 75) of EPA 

problem formulation does not accurately reflect the existence of the two available oyster studies 

(MRID‟s: 00146118 and 00158783), although they are listed in the bibliography.”

EFED Response: 

Based on the available data evaluation records (DERs) for these studies, the Barrows and Dillon 

(1984) oyster study (ACC. No.: 250816; MRID: 00146118) is classified as invalid and is not 
Page 20 of 27

acceptable for use in risk assessment. The results were based on a static, rather than a flowthrough system. 

Based on the available DER for Carr (1986) (ACC. No.: 262443; MRID 00158783), the results 

from this study were found to be acceptable for use in risk assessment. The discrepancy between 

the study reported EC50 value (i.e., 3.42 μg a.i./L) and the one reported in the problem 

formulation (i.e., 2.69 μg a.i./L) is due to the fact that the analysis conducted by EFED (unlike 

what was done by the study author) did not use the pooled controls (the negative and solvent 

controls combined).

24. BCS Comment:

Non-Guideline Study: Aquatic Invertebrate Acute Toxicity (Hyalella azteca) (Cyfluthrin)

“Besides considering additional single species data on non-standard test organisms, will the 

agency also consider more complex studies (e.g., mesocosoms and population modeling) that are 

useful in putting the results of single species studies into an ecological context?”

“Will the agency accept studies with closely related species (e.g., Gammurus spp.) as meeting 

this data requirement? Bayer does have a study (Heimbach, 2000) conducted with a non-USA 

formulation for Gammurus pulex which Bayer will submit for review. If the existing data is 

deemed inadequate to meet the data requirement, Bayer will, upon confirmation that a robust test 

protocol is available, conduct the study as requested.”

EFED Response: 

EFED will consider all submitted data for use in the risk assessment conducted for cyfluthrin and 

β-cyfluthrin. It is unlikely that a mesocosm study would be adequate to fulfill the data 

requirement for an acute toxicity study with H. azteca. Additionally, unless it can be 

demonstrated that a related species is at least as sensitive to cyfluthrin as H. azteca, a study with 

a related species would likely not be adequate to fulfill this data requirement since H. azteca has 

been demonstrated to be substantially more sensitive to pyrethroids than Daphnia magna. 

Furthermore, a study using a non-USA formulation is not adequate for use in risk assessments 

conducted by the agency unless it can be demonstrated that the non-USA formulation is 

representative of a formulation registered in the USA. 

25. BCS Comment:

Non-Guideline Study: Whole sediment: chronic invertebrates freshwater and marine (Cyfluthrin)

“... Bayer would like to work with the agency, industry and experts in the scientific community 

to ensure that the methods used are robust, reliable, and predictive. 

With respect to existing marine 28-day sediment study (MRID 46591506) with Leptocheirus 

plumulosus, reproduction was not included in the initial protocol because amphipod reproduction 

is not a robust endpoint. However, an analysis of reproduction was performed post study 
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termination on preserved samples. Please see Giddings (2006) for a reporting and analysis of the 

available data. Bayer believes this existing study, conducted at EPA‟s request and with their 

guidance, should meet the data requirement for a marine chronic sediment study. “

EFED Response: 

EFED is actively working with the PWG to develop an acceptable methodology for a whole 

sediment chronic toxicity invertebrate study that would provide results that are adequate for use 

in risk assessment. 

Regarding the Giddings (2006) summary (MRID 46871501), the study author made the 

following conclusion: 

“... (B)oth growth (dry weight at 28 d) and reproduction of L. plumulosus appeared to be 

subject to unknown sources of variability among and within studies. Until the cause(s) of 

this variability have been identified and brought under control, results of the L. 

plumulosus tests must be interpreted with caution, and the reproduction data are 

considered unreliable” (p. 27).

Although, EFED will consider the information in this report in the risk assessment for the 

cyfluthrins, based on Giddings‟ (2006) own evaluation of the cyfluthrin study, it is unlikely that 

these data would be adequate to fulfill the data requirement for a marine chronic sediment study.

26. BCS Comment:

Guideline # 850.4100 and 850.4150 Vegetative vigor and Seedling emergence, Tier I/ Tier II

(Cyfluthrin)

“The screening study (Lechelt-Kunze, 2002a) addresses the potential effect of cyfluthrin to nontarget plants and should fulfill the regulatory data requirement.... Because cyfluthrin works in 

insects as a neural toxin, and unlike insects, plants do not have neural networks, it is highly 

unlikely that cyfluthrin would cause phytotoxicity. Cyfluthrin has been registered for use on a 

very wide range of plants for many years and while Agency‟s review of the available incident 

data found three phytotox incidents, those incidents are much more likely to be due to other 

factors (e.g. herbicide contamination resulting from improperly cleaned spray tanks) rather than 

cyfluthrin... We request that considering the properties of cyfluthrin and its long history of safe 

use on a range of plants, that additional plant testing of cyfluthrin be waived.”

EFED Response: 

The Agency received this study [Lechelt-Kunze, C. (2002): Cyfluthrin EC 050: Post-emergence screening 

for herbicidal activity. Bayer AG, Monheim, Germany. M-056722-01-2; MRID 48350619] on January 

11, 2011; it is still being processed and is not currently available to EFED for review. Therefore, we are 

not able to address whether or not this study can be used to fulfill this data requirement at this time. 

When the study becomes available, EFED will review the study to determine if it can be used to fulfill 

this data requirement.
Page 22 of 27

In addressing this comment, it was determined that a search of OPP‟s Aggregate Incident 

Database was not included in EFED‟s cyfluthrin problem formulation. Therefore a search of the 

Aggregate Incident Database was conducted on January 4, 2011, for cyfluthrin in order to gather 

more information regarding potential plant incidents associated with the use of the chemical. 

There are currently 132 “minor” plant incidents listed in the Aggregate Incident Database for 

cyfluthrin that date from 1999 to 2004 (see APPENDIX A). Since detailed information is not 

available for the aggregate incidents, it is current EFED policy to assume that these incidents are 

the result of registered uses unless information is provided that indicates otherwise. Therefore, 

EFED does not recommend waiving the terrestrial plant toxicity data requirement for cyfluthrin 

at this time.

27. BCS Comment:

Guideline # 850.4400 Aquatic Vascular Plant Growth-Lemna spp. Tiers I/II (Cyfluthrin) 

“Because the cyfluthrin is a pyrethroid and non-phytotoxic, no study has been requested by any 

regulatory authority in the past, and to our knowledge no such study currently exists. Conduct of 

a study with cyfluthrin is not expected to impact the overall risk assessment.”

EFED Response: 

Due to the terrestrial plant incidents associated with cyfluthrin and a lack of phytotoxicity data 

for the chemical, there is uncertainty regarding the potential impacts of cyfluthrin on non-target 

plants (including aquatic plants). Therefore, EFED still recommends that these data be 

requested.

28. BCS Comment:

Guideline # 850.1400 or 850.1300/850.1350 Fish Early Life Stage or Invertebrate Life Cycle (βcyfluthrin)

“Bayer CropScience understands the agency‟s interest in a Mysidopsis bahia life-cycle study and 

will conduct it as requested.”

EFED Response: 

No response needed.

29. BCS Comment:

Guideline # 850.4100 or 850.4150 Seedling emergence or Vegetative vigor (β-cyfluthrin)

“The screening study (Lechelt-Kunze 2002b), addresses the potential effect of β-cyfluthrin to 

non-target plants and fulfills the regulatory data requirement... We request that considering the 

properties of β-cyfluthrin and its history of safe use on a range of plants that additional plant 

testing of β-cyfluthrin be waived. If, after considering the available information, the Agency 

decid(es) additional plant testing is necessary, we propose that the agency rely on a study with 
Page 23 of 27

cyfluthrin and hold additional testing with β-cyfluthrin in reserve. It is highly unlikely that 

additional toxicity testing with plants will generate data that will result in significant impacts to

the ecological risk assessment or use pattern.”

EFED Response: 

The Agency received this study [Lechelt-Kunze, C. (2002): Β-cyfluthrin EC 025: Post-emergence 

screening for herbicidal activity. Bayer AG, Monheim, Germany. M-055590-02-2; MRID 

48350620] on January 11, 2011; it is still being processed and is not currently available to EFED for 

review. Therefore, we are not able to address whether or not this study can be used to fulfill this 

data requirement at this time. When the study becomes available, EFED will review the study to 

determine if it can be used to fulfill this data requirement.

There are two plant incidents listed for β-cyfluthrin in the Aggregate Incident Database (see 

APPENDIX A). Since detailed information is not available for the aggregate incidents, it is 

current EFED policy to assume that these incidents are the result of registered uses unless 

information is provided that indicates otherwise. These incidents along with those plant 

incidents reported from the EIIS database for cyfluthrin and β-cyfluthrin (not all of which can be 

attributed to other chemicals) and those reported for cyfluthrin in the Aggregate Incident 

Database, indicate a potential risk to plants from the use of these chemicals. 

As described in the data request justification table from the problem formulation for cyfluthrin 

and β-cyfluthrin (see p. 110 of the document) and per current EFED policy, terrestrial plant data 

for β-cyfluthrin are only required for the most sensitive monocot and dicot species (as identified 

from the cyfluthrin plant studies). EFED still recommends that these data be requested.

30. BCS Comment:

Guideline # 850.4400 Aquatic Vascular Plant Growth-Lemna gibba (β-cyfluthrin)

“Because the β-cyfluthrin is a pyrethroid and non-phytotoxic, no study has been requested by 

any regulatory authority in the past, and to our knowledge no such study currently exists. 

Conduct of a study with β-cyfluthrin is not expected to impact the overall risk assessment. 

If, after considering the available information, the Agency deciding additional plant testing is 

necessary, we propose that the agency rely on a study with cyfluthrin and hold additional testing 

with β-cyfluthrin in reserve.”

EFED Response: 

Due to the terrestrial plant incidents associated with β-cyfluthrin and a lack of phytotoxicity data 

for the chemical, there is uncertainty regarding the potential impacts of β-cyfluthrin on nontarget plants (including aquatic plants). Therefore, EFED still recommends that these data be 

requested for both cyfluthrin and β-cyfluthrin, per current EFED policy.
Page 24 of 27

References:

Holmes, R.W., B.S. Anderson, J.W. Hunt, D.B. Crane, A. Mekebri and V. Connor. 2008. Statewide 

Investigation of the Role of Pyrethroid Pesticides in Sediment Toxicity in California‟s Urban Waterways. 

Environ. Sci. Technol. 2008, 42, 7003–7009.

Weston, D.P. and M.J. Lydy. 2010. Urban and Agricultural Sources of Pyrethroid Insecticides to the 

Sacramento-San Joaquin Delta of California. Environ. Sci. Technol. 2010, 44, 1833–1840.

USEPA, 2010. Response to Public Comments on the EFED Registration Review Problem Formulation 

for Bifenthrin (PC Code No. 128825; DP Barcode D382626). Office of Pesticide Programs, United 

States Environmental Protection Agency, Washington, DC. December 22, 2010.
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APPENDIX A: Incidents Reported in the Aggregate Incident Database for Cyfluthrin and 

β-cyfluthrin
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