UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C . 20460

MEMORANDUM Date: December 17, 2013 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

SUBJECT: Atraz in e. Response to Comments on the Human Health Risk Scoping Document in Support of Registration Review. PC Code: 080803 Decision No.: 485501 Petition No . : NA Risk Assess ment Type: Response to Comments TXRNo . :NA MRIDNo . :NA FROM : John Liccione, PhD, Toxicologist William Donovan, PhD, Ri s As Seyed Tadayon, Chemist Risk Assessment Branch V. B V) DP Barcode : D416486 Registration N o. : NA Regulatory Action : Registration Review Case No . : 0062

Health Effects Division (HED) (7509 P) THROUGH: Michael S. Metzger, Chief R isk As sessment Branch V Health Effects Division (7509P) TO : Kaitlin Keller, Chemical Review Manager Risk Management and Implementatio n Branch III (RMIB 3) Pesticide Re-Evaluation Divi sion (PRD ) (7508 P)

This memorandum contains HED's responses to atrazine comment s submitted during the public comment period regarding HED's "Atrazine, Propazine, and Simazine. Human Health Risk Scop ing Document in Support of Registration Review, June 04, 2013". The responses are provided after giving the document number, commenter affiliation, and a brief summary ofthe comment received. Page 1 of6Document Number: EPA-HQ-OPP-2013-0266-0299 Commenter Affiliation: Syngenta • Comment: "In the Human Health Risk Scoping document in support of registration review, the agency stated that toxicity endpoints for chlorotriazine herbicides will be reevaluated after consideration of recent studies in the published literature.'' Syngenta suggested a number of considerations for the agency that were discussed during the July 2011 SAP. These considerations included the following: (1) pulsatile LH is the most relevant for human risk assessment; (2) brief exposures to atrazine
- LH surge reduction and observed effects; and (3) extensive new studies on atrazine establish greater confidence in MOEs.
• Response: EPA will consider, on a total weight of evidence basis, all available studies on atrazine and LH (pulsatile and nonpulsatile), including duration of exposures and points of departure to atrazine as part of the registration review process . This will also entail critica l evaluation ofthe scientific quality of the studies to assess the adequacy and acceptability of the studies (e.g., validation of hormone assays, experimental bias, adequacy of sample size, sampling frequency, statistical methodology, study design, dose-response relationships, uncertainties, extrapolation to humans) for risk assessment purposes . In addition, the recommendations of the SAP on LH in the interpretation of atrazine health effects will be considered . Document Number : EPA
-HQ-OPP-2013-0266-0073 Commenter Affiliation: Beyond Pesticides
• Comment: "As a result of its endocrine disrupting ability, studies are finding associations between atrazine exposure, birth defects and certain cancers. EPA's past findings for the carcinogenic potential of atrazine- 'not likely to cause cancer in humans'- is at odds with current research which finds atrazine to impact mammary glands in the breast, increasing the risk for mammary cancer."

• Response: EPA has evaluated a plethora of published studies investigating a wide array of effects potentially relevant to human health risk assessment. These studies included mammary cancer in various rat strains (Long-Evans, Wistar, Fischer-344) as well as other species. Epidemiological data were also reviewed. As part of the weight-of-evidence approach, the agency also evaluated mechanistic studies to determine if a particular mode of action identified in an animal model is relevant to humans. This approach also included an evaluation of studies designed specifically to examine LH surge and atrazine. Page 2 of6The key events associated with the increased incidence of mammary tumors in rats were explored, and relevancy to humans addressed. To be certain that the best available science is used to inform its atrazine risk assessment, and to ensure transparency, the agency sought advice on key aspects of the science evaluation from the independent FIFRA Scientific Advi sory Panel (SAP). Based on the review ofavailable scientific studies, the agency determined in 2000 that atrazine is not likely to cause cancer in humans. Since 2000, there have been no new data that has changed the 2000 conclusion with re spect to mammary tumors. The agency will continue to monitor the literature and evaluate any new science that may impact our conclusion. Document Number: EPA-HQ-OPP-2013-0266
-0081 Commenter Affiliation: PANNA
• Comment: PANNA commented that the agency should consider the SAP's recommendations on the following points: ( 1) brief exposures to low levels of atrazine and LH surge reduction and observed adverse effects; (2) relevance of one day exposure to elicit adverse outcome(s) and of increase vs. decrease in LH; (3) evaluation ofdata about atrazine and mammary development; (4) sufficiency of agency's cancer epidemiology reviews.

• Response: See response to comment to document number EPA-HQ-OPP
-2013-0266 -007 3 for background on the agency's weight of evidence approach to the evaluation ofhuman health data on atrazine. In regard to the sufficiency of the agency ' s cancer epidemiology reviews, the SAP concluded that substantive and persuasive arguments have been made to suppo rt the agency's conclus ions. The agency wi ll consider any new data as part ofthe registration review proce ss for the triazines. This will also entail consideration of the SAP's recommendations on LH surge, relevance of one day exposures and adverse outcomes , mammary tumor development, and epidemiological data as part of the registration review of !he triazines. Document Number: EPA-HQ-OPP-20 1 3-0266-0035 Commenter Affiliation: Anonymous
• Comment: Several comments were received pertaining to mammary tumors; these included: ( 1) please comment on the appropriateness of these other models [e.g., ovariectomized inbred Fischer
-344 (MT-insusceptible), Long-Evans, and Wistar rat strains] in mechanistic explorations of MT induction by atrazine, and whether alternatives to the LH-dependent/hypothalamic site of action have been investigated sufficiently in appropriate models and ruled out; (2) please explain specifically why the Agency and registrants have not robustly inve s tigated the direct/LH-independent effects Page 3 of6of atrazine in aromatase-positive granulosa cells derived from SD rat and pr imary human 

### fo ll icles in straightforward and cost-effective cell culture studies; and (3) please also clarify why MT-promoting events following LH attenuation in the outbred SD rat are not relevant to humans.
• Response : See response to comment to document number EPA
-HQ
- OPP-2013
-0266- 0073 for background on the agency's weight of evidence approach to the evaluation of human health data on atrazine. I n 2000, the SAP considered all possible alternative models, and concluded that increased hormone levels, and the increased hormone levels alone, can account for the increased incidence of mammary tumors in Sprague
-Dawley female rats. Although atrazine has been shown to increase aromatase in granulosa-lutein cell cultures, the concentrations needed to induce the observed change is considered to be outside the range likely to be achieved in human tissues. The agency will consider any new data including cell culture studies as part ofthe registration review process for the triazines. Document Number: EPA-HQ
- OPP
-2013
- 0266-0036 Commenter Affiliation : Anonymous
• Comment: Several comments were received pertaining to LH and mammary tumors; these included: (1) please explain how the hypothesized hypothalamic/LH-dependent effect of anovulation and 'accelerated reproductive senescence' can be reconciled with elevated estrogen levels in ovariectomized and male rats exposed to atrazine (2) regarding mechanisms of mammary tumor induction in the ovary-intact SD rat, the registrants and Agency repeatedly claim atrazine merely 'accelerates reproductive senescence' and 'early onset of mammary tumors' (not incidence, per se). Please explain to a female researcher why; and (3) please comment on whether "changes in LH secretion as a sentinel endpoint for HPG perturbations and the basis of the atrazine risk assessment" are still sufficient indicators of mammary and breast tumor hazard given recent Agency and external studies demonstrating atrazine has direct/LH-independent effects on aromatase and estradiol production in both rat and human adrenal cells at very low biologically relevant doses.

• Response: See response to comment to document number EP A-HQ
- OPP-20 13-0266-0073 for background on the agency's weight of evidence approach to the evaluation of human health data on atrazine. Based on the available data, the SAP concluded that atrazine treatment is associated with an early onset ofmammary tumors in female Sprague-Dawley rats. Although in vitro studies have demonstrated that atrazine can alter aromatase activity and gene transcription, the total weight of evidence of all data indicate that atrazine
-related changes in steriodogenesis is not likely mediated by aromatase. The agency will continue to Page 4 of6monitor the literature and consider any new data as part of the registration review process for the triazines. Document Number : EPA-HQ
-OPP-2013
-0266-0064 Commenter Affiliation: Pesticide Action Network
• Comment: Several comments were received pertaining to LH and mammary tumors; these included: (1) please describe "the particular cascade of events leading to tumor formation" in the SD rat, and how thi s differs from the cascade of events that follow LH attenuation in the Fisher-344 rat; (2) please also clarify why MT-promoting events following LH attenuation in the outbred SO rat are not relevant to humans, but mechanisms oftoxicity via LH suppression in the inbred MT-insusceptible Fisher-344 rat can be relied upon to inform regulatory decisions; (3) p lease also comment the decision of the 2003 IRED to "use changes in LH secretion as a sentinel endpoint for HPG perturbations and the basis of the atrazine ri sk assessment" in the absence of robust cell culture studies that could easily capture the direct effects of atrazine on estrogen/progesterone biosynthesis in rat and human ovarian granulosa/luteal cells; (4) please explain how the hypothesized hypothalamic/LH
-dependent effect of anovulation and 'accerated reproductive senescence' can be reconciled with elevated estrogen levels in ovariectomized and male rats exposed to atrazine; (5) please comment on whether "changes in LH secretion as a sentinel endpoint for HPG perturbations and the basis of the atrazine risk assessment" are still sufficient indicators of mammary and breast tumor hazard given recent Agency and external studies demonstrating atrazine has direct /LHindependent effects on aromatase and estradiol production in both rat and human adrenal cells at very low biologically relevant doses; (6) please explain how LH-independent effects of atrazine in the rat ovary (aromatase) are not relevant to human breast cancer (aromatase misregula tion in the breast).

• Response: See response to comment to document number EPA-HQ-OPP-2013-0266- 0073 for background on the agency's weight of evidence approach to the evaluation of human health data on atrazine. The agency will continue to monitor the literature and consider any new data and the comments as part ofthe registra tion review process for the triazines. Document Number: EPA-HQ
-OPP-2013
- 0266
- 0037 Commenter Affiliation: Anonymous Public Comment

• Comment: Several comments were received pertaining to LH and mammary tumors; these included: (1) please explain how LH-independent effects of atrazine in the rat ovary (aromatase gonadal promoter) are not relevant to human breas t cancer (aromatase gonadal promoter misregulation in the breast); (2) please ask the Agency Lab: if one Page 5 of6transfects human breast cancer cells with a rat gonadal aromatase-r eporter gene and treats 

### these with atrazine, would the gene to light up? Would this indicate mechanisms are conserved between species?; (3) please discuss whether epigenetic background is considered in 'species- specific ' responses to atrazine and whether the outbred SD strain (mammary-tumor susceptible) or inbred Fisher-344 rat strain (used by registrants and Agency in 'mechanistic studies') would be expected to have epigenetic variation more relevant to human health.

• Response: See response to comment to document number EP A
-HQ-OPP-20 13-0266- 0073 for background on the agency's weight of evidence approach to the evaluation of human health data on atrazine. The agency will continue to monitor the literature and consider any new data and comments as part ofthe registration review process for the triazines. Document Number: EPA-HQ
-OPP
-20 13
- 0266-0015 and EPA-HQ-OPP-20 13-0266
-0305 Commenter Affiliation : PANNA
• Comment: PANNA commented that the agency has not responded to the SAP's recommendations on the cancer classification of atrazine, and comments on increased risks of reproductive harms and birth defects linked to low-level atrazine exposures.
• Response: Even though the Panel agreed with EPA that the epidemiologic evidence does not strongly suggest a link between atrazine and cancer, the Panel noted some suggestive epidemiologic findings for specific tumors that warrant additional analyses prior to EPA's full weight-of-evidence review ofthe cancer classification for atrazine. Following the EPA's Cancer Assessment Guidelines, the Agency will weigh and integrate all ofthe lines of scientific evidence (e.g., toxicology, metabolism, epidemiology , mode of action studies). EPA plans to take the recommendations from the SAPs into account as it updates the state of the science on the health effects of atrazine.

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