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Jessica Poppe Q&A

April 13, 2011 

1. At what stage in the process is the reevaluation of atrazine at currently? 

In 2010, EPA held three Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory 

Panel (SAP) meetings on human health issues related to atrazine. In February, EPA presented and 

sought scientific peer review of its proposed plan for incorporating epidemiology studies into the 

atrazine risk assessment. Later, in April, EPA presented and sought scientific peer review of its 

evaluation of atrazine effects based on experimental laboratory studies that will inform the selection of 

endpoints and safety factors in the risk assessment, and the sampling design used to monitor drinking 

water in community water systems. In September, EPA presented and sought scientific peer review of 

its evaluation of atrazine non-cancer effects based on experimental laboratory studies and epidemiology 

studies. The September review was intended to include any new experimental laboratory data since the 

April 2010 SAP meeting. 

This summer, EPA plans to hold another SAP meeting concerning the Agricultural Health Study findings 

as well as epidemiology and laboratory animal studies on atrazine. At the conclusion of this evaluation 

of atrazine’s human health effects, EPA plans to ask the SAP to review atrazine’s potential effects on

amphibians and aquatic ecosystems. 

After this extensive review of atrazine, EPA plans to make any needed risk management decisions. 

These decisions will be consistent with the science and our pesticide statutes. 

2. Where there any studies or research in particular that prompted the reevaluation or are 

playing a particularly important role in the reevaluation? 

EPA did not base its decision to formalize the re-evaluation process on the results of any one study. 

Over the last 8 years since the 2003 Atrazine Interim Reregistration Eligibility Decision (IRED) was 

completed, significant atrazine research has been done. Moreover, EPA has received an extensive 

amount of drinking water and ambient surface water monitoring data from the registrants of atrazine, 

as an ongoing condition of reregistration. As part of the 2010 SAP reviews, EPA evaluated close to 150 

studies published since 2003 investigating a wide array of potential cancer and non-cancer effects 

relevant to human health risk assessment. If you are interested in reading EPA’s reviews of these 

studies, as well as the meeting transcripts and the SAP’s recommendations, you may visit the Agency's 

2010 SAP Meetings Web page, http://www.epa.gov/scipoly/sap/meetings/2010/index.html. 

3. Does the EPA have an approximation for the number of people exposed to concentrations of 

atrazine (maybe the population within the 1,172 watersheds with potential vulnerability)? 

In its October 2003 Atrazine Interim Reregistration Eligibility Decision (IRED), EPA required the atrazine 

registrants to conduct watershed monitoring to ensure protection of aquatic ecosystems. The 

watershed monitoring program was designed to focus initially on flowing water bodies in the most 

vulnerable watersheds associated with corn and sorghum production. Monitoring occurred over a 

three-year period (2004 through 2006), and certain sites have had additional monitoring conducted 

from 2007-2010. During the initial sampling timeframe, 40 watersheds were monitored which were 

statistically representative of 1,172 watersheds identified as potentially vulnerable to atrazine exposure 

based on atrazine use and runoff potential in these watersheds. The ambient streams associated with 
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these 1,172 watersheds are not drinking water sources. Protection of drinking water sources are 

considered separately under the Safe Drinking Water Act (SDWA) as well as the Office of Pesticide 

Programs’ (OPP’s) monitoring of atrazine in Community Water Systems (CWSs). 

With regard to SDWA, the number of public water systems reporting violations of the atrazine MCL in 

the United States in any given year between 2002 and 2010 ranged from zero to 10. In fiscal year 2010, 

only one public water system in the United States reported a violation of the atrazine MCL. This public 

water system is now purchasing its drinking water from another public water system. 

With regard to the Office of Pesticide Programs’ (OPP’s) monitoring in CWSs, none of the CWSs in the 

monitoring program have exceeded OPP’s 37.5 ppb human health level of concern as a 90-day rolling 

average in raw water. Two exceedances of this level in raw water at a CWS in different years over a fiveyear period results in prohibition of further atrazine use in the associated watershed. Additional 

information regarding the Office of Pesticides’ monitoring in CWSs can be found at: 

http://www.epa.gov/opp00001/reregistration/atrazine/atrazine_update.htm 

4. What groups do you think are most vulnerable to the health effects of atrazine? 

Please refer to Sections 2, 3, and 4 of EPA’s Issue Paper for the September 14 - 17, 2010 FIFRA SAP 

Meeting located at www.regulations.gov docket number EPA-HQ-OPP-2010-0481-0030.

5. Is there any current information on the mechanism of how atrazine might specifically affect 

pregnant women? Since atrazine seems to affect the hypothalamic pituitary axis, is it know 

what affect these changes could have on a fetus? 

Please refer to Sections 2, 3, and 4 of EPA’s Issue Paper for the September 14 - 17, 2010 FIFRA SAP 

Meeting located at www.regulations.gov docket number EPA-HQ-OPP-2010-0481-0030.

6. Are there any pre-existing health conditions that are known to possibly intensify the health 

effects of atrazine on any population? 

Please refer to Sections 2, 3, and 4 of EPA’s Issue Paper for the September 14 - 17, 2010 FIFRA SAP 

Meeting located at www.regulations.gov docket number EPA-HQ-OPP-2010-0481-0030.

7. Has atrazine caused any major potential health effects outside of the reproductive or 

endocrine systems? 

Please refer to Sections 2, 3, and 4 of EPA’s Issue Paper for the September 14 - 17, 2010 FIFRA SAP 

Meeting located at www.regulations.gov docket number EPA-HQ-OPP-2010-0481-0030.

8. An additional question that I have, regarding the risk management of atrazine in drinking 

water, is whether the EPA is involved in any health education practices in the communities 

found with elevated levels of atrazine in their drinking water? 

EPA's approach to providing safe drinking water focuses on addressing contamination before water 

reaches consumers, either by source water protection efforts such as those implemented through the 
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pesticide registration process or by setting drinking water standards for treated water from public water 

utilities. 

Under the Safe Drinking Water Act (SDWA), monitoring and reporting requirements exist for the 

Maximum Contaminant Level (MCL) of 3 ppb, which is based on chronic exposure and is calculated 

against a running average from four quarterly samples. If any sample result taken for compliance 

purposes will cause the running annual average to exceed the MCL at any sampling point, the system is 

out of compliance with the MCL immediately. 

When a water system violates an MCL, the water system must notify the people who drink its water 

about the violation, what it means, and how they should respond. Atrazine violations are reported in 

the Consumer Confidence Reports (CCRs) that water systems are required to provide their customers 

annually. 

Under the EPA’s atrazine Interim Reregistration Eligibility Decision and Memorandum of Agreement 

with atrazine registrants, the primary atrazine registrant provides EPA with monitoring data from the 

previous year that allows EPA to check for compliance with the Office of Pesticides Program’s 

intermediate-term level of concern of 37.5 ppb, measuring atrazine and its degradates in raw water. 

EPA uses the data to determine whether the Agency will allow continued use of atrazine in watersheds 

associated with the most vulnerable community water systems. Within a particular Community Water 

System, two exceedances of the 37.5 ppb level of concern in raw water, calculated as a 90 day rolling 

average, in two different years over a five-year period results in prohibition of further atrazine use in the 

associated watershed. 

What types of control does the EPA endorse (at the source, along the path, and at a personal level) in

order to limit the levels of atrazine exposure through drinking water?

Under its Safe Drinking Water Act authority and in order to limit the amount of atrazine allowed in 

finished drinking water that is served by public water systems, EPA has established a national primary

drinking water regulation (NPDWR) that specifies an enforceable Maximum Contaminant Level (MCL) of 

3 ppb. As part of the NPDWR, public water systems are required to takes steps (i.e., monitoring and 

possibly treat) to ensure that the finished drinking water does not exceed the 3 ppb standard. 

During the atrazine reregistration process in 2003, EPA felt that it was important to ensure the 

protection of raw drinking water – that is, water that had not yet been treated by drinking water 

utilities. Therefore, as part of atrazine’s reregistration, EPA established a drinking water monitoring 

program where raw water is monitored in water systems more likely to have higher seasonal atrazine 

contamination, and where exceedences in raw water trigger use prohibitions in the watershed of 

concern This raw water performance standard approach makes the prevention of atrazine water 

contamination the responsibility of atrazine users rather than water treatment plant operators. 

 

Since use prohibitions result from exceedences is in raw, not finished water, the Agency believes there is 

a strong incentive for atrazine users and the registrants to make every effort to prevent exceedences. 

Additionally, the public water utility’s monitoring and potential treatment of water to meet Safe 

Drinking Water Act standard of 3 ppb is more likely to prevent actual exposures above the Agency’s 37.5 

ppb intermediate-term level of concern for atrazine.