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Atrazine Updates

Statement from Steve Owens, Assistant Administrator for the Office of Prevention, Pesticides and Toxic Substances (OPPTS)

Atrazine Evaluation

Current as of January 2010

FIFRA SAP Meeting on Atrazine -- On February 2 – 5, 2010, the FIFRA Scientific Advisory Panel will meet to review and consider the "Draft Framework and Case Studies on Atrazine, Human Incidents, and the Agricultural Health Study: Incorporation of Epidemiology and Human Incident Data into Human Health Risk Assessment.” The meeting will be held at the:

Environmental Protection Agency
Conference Center - Lobby Level
One Potomac Yard (South Bldg.)
2777 S. Crystal Dr.
Arlington, Virginia 22202
8:30 a.m. to 5:00 p.m.

For additional information, please see the FIFRA SAP web site.


One of the most widely used agricultural pesticides in the U.S., atrazine may be applied before and after planting to control broadleaf and grassy weeds.  It is used primarily on corn, sorghum, and sugarcane, and is applied most heavily in the Midwest.  Atrazine is used to a lesser extent on residential lawns, particularly in Florida and the Southeast.  Go to more information about atrazine.

On this page you will find:

Atrazine SAP Meetings

New Atrazine Evaluation

EPA is launching a new comprehensive evaluation of atrazine. This review is based on transparency and sound science, including independent scientific peer review, and will help determine whether a change in EPA’s regulatory position on atrazine is appropriate. Based on this evaluation, the Agency will decide whether to revise its current atrazine risk assessments and whether new restrictions are necessary to better protect health and the environment.

During the first year of the new evaluation, EPA is considering the potential for atrazine cancer and non-cancer effects, including data generated since 2003 from laboratory animal and human epidemiology studies. To be certain that the best science possible is used to inform its atrazine human health risk assessment, and to ensure transparency, EPA is seeking advice from the independent FIFRA Scientific Advisory Panel (SAP).

EPA is engaging the SAP this year to reevaluate the human health effects of atrazine. 

At the conclusion of this evaluation of atrazine’s human health effects, EPA will ask the SAP to review atrazine’s potential effects on amphibians and aquatic ecosystems. The meetings of the SAP will be open to the public.

In addition to the scientific review of atrazine’s human health and ecological effects, EPA plans to meet with interested groups to explore better ways to inform the public more quickly about results of atrazine drinking water monitoring.

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Triazine Cumulative Risk Assessment

EPA’s triazine cumulative risk assessment considered the combined effects of atrazine and simazine, two closely related triazine herbicides. In 2006 EPA concluded that cumulative exposures to these pesticides through food and drinking water are safe and meet the rigorous human health standards set forth in the Food Quality Protection Act (FQPA). This assessment showed that the levels of atrazine and simazine that Americans are exposed to in their food and drinking water, combined, are below the level that would potentially cause health effects.

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Atrazine Post-RED Results

Quick Resources
This section provides results to date from the programs, activities, and studies required by EPA’s Atrazine Reregistration Eligibility Decision (RED) (PDF) (323 pp, 187M, about PDF) of 2003, including:

Pesticide Programs' Monitoring in Community Water Systems

Status Update - August 2009

Atrazine Monitoring Data

Currently, an intensive monitoring program to look for atrazine residues in drinking water from approximately 150 community water systems (CWS) is ongoing. These systems, located primarily in the Midwest, are among the most vulnerable to atrazine exposure.

Through its review of these data, the Agency has confirmed that none of the systems have exceeded OPP's level of concern, a 90-day average of 37.5 parts per billion (ppb) of atrazine and its degradates. In fact, the Agency has released 20 CWS from the program because these systems have had no exceedences of EPA’s level of concern after five years of monitoring. EPA has added approximately 20 CWS into the program based on data gathered under the Safe Drinking Water Act (SDWA).

The data available are the following:

The following data complement the summary listed above. These seven spreadsheets present atrazine drinking water monitoring data that are required under the Agency’s 2003 Atrazine Reregistration Eligibility Decision (RED) and subsequent Memorandum of Agreement (MOA) with the atrazine registrants. These Atrazine Monitoring Program (AMP) data files contain the results of the required sampling, by year, for all CWS that have been monitored over a 6-year period from 2003-2008.

Each data file includes a “ReadMe” worksheet that explains the data contained in the file. AMP data for 2003 and 2004 do not contain simazine data. AMP data from the latter half of 2005 onward contain data for all triazine residues, including simazine.

If you need these data in a different format than the Excel spreadsheets for accessibility or other reasons, please contact Melanie Biscoe (biscoe.melanie@epa.gov) or 703-305-7106.

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Interpreting the Atrazine Drinking Water Monitoring Data

An EPA level of concern is specific to a particular issue (human health, for example) and an exposure period. For example, a long-term (or chronic) level of exposure would be associated with an exposure over many months or years, whereas an intermediate level of exposure would be looking at potential health effects over a three-month period. Through the atrazine monitoring programs in place, EPA can evaluate all these potential exposures.

Atrazine potential risk and how it is evaluated

Change in hormone levels is the most sensitive health effect observed in an extensive battery of atrazine toxicity tests. In other words, if the Agency’s standard is protective of hormonal effects, it will protect against all other effects that occur at higher levels. The Agency’s 2003 risk assessment supporting the re-registration of atrazine incorporates standard safety factors to ensure protection of public health, as well as an additional safety factor to ensure further protection for children.

As a result, EPA’s risk assessment includes a 300-fold margin of safety to help ensure that an exposure will not affect hormone levels, and a 1000-fold margin of safety to help protect against long-term or chronic effects. In other words, the exposure that the Agency allows under is at least 300 to 1000 times more protective than the level where the Agency saw no adverse effects in the most sensitive animal species tested. EPA applies these additional safety factors as a precaution to protect the public health of all consumers in the United States.

Based on this risk analysis the Agency determined that concentrations of atrazine and its metabolites in raw water below an average of 37.5 ppb over a 90-day period ensures protection of pregnant women and all others, and concentrations of atrazine in finished water that do not exceed 3 ppb as an annual average protect consumers from longer term chronic effects.

The following paragraphs describe the short-, intermediate-, and long-term exposure levels that EPA has evaluated and found to be protective of human health.

Short-term exposure - Based on the Agency’s screening-level assessment conducted for the Atrazine Interim Reregistration Eligibility Decision (IRED) from 2003, one-day concentrations less than the Drinking Water Level of Concern (DWLOC) of 298 ppb do not exceed the Agency’s level of concern for acute effects. In other words, occasional readings of atrazine that are below 298 ppb in water treated by municipalities do not pose a risk to human health.

Intermediate-term exposure - The Office of Pesticide Programs’ level of concern for drinking water is an intermediate level of exposure where the level is exceeded if, in a 90-day rolling average, the concentration exceeds 37.5 ppb for atrazine and its degradates in raw water. After six years of monitoring, although some amount of atrazine may be detected in community water systems, none of the 150 CWS in the monitoring program have exceeded the 37.5 ppb level of concern as a 90-day rolling average in raw water. This suggests that the more stringent restrictions and use practices required by the Agency in 2003 are working to reduce the amount of atrazine reaching water bodies, thereby protecting public health. If any CWS were to exceed this level twice within a five-year period, EPA would prohibit atrazine use in the watershed associated with the CWS.

Long-term exposure - Under the Safe Drinking Water Act (SDWA), the atrazine Maximum Contaminant Level (MCL) is intended to prevent longer-term, or chronic, health concerns from occurring even after years of exposure and is calculated against a running average from four quarterly samples. An occasional peak concentration above 3 ppb is, therefore, not cause for concern. Rather, a long-term, consistent value above a yearly average of 3 ppb would be of concern. The MCL is designed to protect all population subgroups.

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Background on CWS Monitoring Program

The January 2003 Atrazine Interim Reregistration Eligibility Decision (IRED) (323 pp, 1.87 MB) about PDF)and subsequent Memorandum of Agreement (MOA) (36 pp, 132k, about PDF) between EPA and the atrazine registrants initiated a monitoring program to focus on the most significant human health exposures associated with agricultural and residential uses -- exposures through drinking water. Through the CWS monitoring program, EPA is ensuring that exposures to atrazine in drinking water do not reach levels that pose a risk to public health. EPA’s regulatory program for atrazine ensures drinking water concentrations are below a level that could potentially cause changes in hormone levels, which is the most sensitive health effect observed in an extensive battery of toxicity tests. The Agency’s level of concern ensures protection of children and adults, including women of child-bearing age.

How CWS were Chosen - Of the approximately 50,000 CWS in the United States, 40,000 are served by ground water and 10,000 are served by surface water. Because atrazine levels in surface water tend to be higher than those in ground water, surface water is EPA's focus for this monitoring program. In 2003, the Agency identified 3,600 systems where atrazine was used and monitoring information was available. OPP used Safe Drinking Water Act (SDWA) data to screen CWS nationwide to see which systems might be more likely to have higher seasonal atrazine contamination. An initial group of CWS was identified for more intensive monitoring based upon the Agency's review of data submitted voluntarily by the registrant. Under conditions of the Atrazine RED and MOA, EPA required an intensive drinking water monitoring program in these CWS. This monitoring program began in 2003.

Information developed by EPA's Office of Water under the SDWA is continually reviewed to determine whether additional CWS should be monitored more intensively through OPP’s required atrazine monitoring program. Since 2003, a number of CWS have been added to OPP’s monitoring program based on SDWA monitoring data as detections approached or exceeded the Office of Water's Maximum Contaminant Level (MCL) for atrazine as an average of four quarterly samples.

CWS Monitoring - Since 2003, raw and finished water at approximately 150 CWS has been monitored under the atrazine MOA to ensure that levels of atrazine and its chlorinated degradates do not reach the level of concern of 37.5 ppb.  Because CWS enter and exit the program on an ongoing basis, the number of systems that have taken part in this program ranges from about 130 to 150 in any given year.  These CWS have been monitored on a weekly basis during the peak atrazine use season and biweekly during the rest of the year.

Under the MOA, monitoring is conducted for at least five years. Two exceedances in raw water at a CWS in different years over a five-year period will result in prohibition of further atrazine use in the associated watershed. If a CWS does not have exceedances during five years of monitoring, it may be released from this monitoring program. To date, 20 systems have been released from the program, and no system has had two exceedances. And about 20 CWS have been added to program.

EPA will continue to review monitoring data under the SDWA. If any CWS in the future have detections approaching the MCL, then the intensive monitoring requirements and regulatory oversight of the Pesticide Program will be invoked.

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Ecological Watershed Monitoring Program

Status Update - July 2009

In mid-2009, EPA released additional atrazine ecological watershed monitoring program data from 2004-2008. These data include results from monitoring of Midwestern streams, as well as results from monitoring of water bodies associated with sugarcane crop production. The data are available in public docket EPA-HQ-OPP-2003-0367. The Agency’s atrazine watershed monitoring program, conducted to ensure protection of aquatic ecosystems, is helping EPA and the states determine the extent to which additional monitoring and/or mitigation may be needed to protect aquatic resources.

Background on Ecological Watershed Monitoring Program

In its October 2003 Atrazine Interim Reregistration Eligibility Decision (IRED) (323 pp, 1.87 MB, about PDF), EPA required the registrants to conduct watershed monitoring to ensure protection of aquatic ecosystems. To gather the necessary data in corn and sorghum-producing areas, EPA required the registrants to implement an innovative, intensive ecological watershed monitoring program, as well as a risk mitigation process if atrazine water concentrations exceed the Agency's levels of concern.

Corn and Sorghum - 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 had additional monitoring conducted in 2007 and 2008.  During the sampling timeframe, 40 watersheds were monitored, and each watershed had at least two years of monitoring data.  The 40 watersheds are statistically representative of 1,172 watersheds identified as potentially vulnerable to atrazine exposure, out of 10,000 watersheds with some atrazine use in the U.S. The results of this survey will inform a decision on the extent to which additional water bodies may need to be surveyed. The study design and results will also aid the states in developing any atrazine monitoring they may wish to undertake. A list of the 40 watersheds (PDF) (2 pp, 125k, about PDF) included in this monitoring program is provided on the atrazine web page. Additionally, monitoring data from the 40 watersheds are available in public docket EPA-HQ-OPP-2003-0367.

For this monitoring program, the level of concern is approximately 10 to 20 parts per billion (ppb) for atrazine over a relatively prolonged period of time (approximately two weeks to three months). This level of concern is consistent with the Office of Water's draft aquatic life criteria.

The level of concern is based on atrazine testing in 33 studies of artificial pond and stream ecosystems. The results of these studies indicated that changes in aquatic plant communities were the most sensitive effects that are caused by atrazine. By focusing on protection of aquatic plant communities, EPA is protecting fish and invertebrates from effects that atrazine could have on habitat and food sources. The severity of atrazine effects on aquatic community structure is highly dependent on the frequency, magnitude and duration of exposure. The Agency has a refined method to evaluate any pattern of atrazine exposure to determine if the level of concern has been exceeded.

If any of the watersheds show levels of atrazine above the Agency’s level of concern for two years, the registrants must initiate watershed-based management activities in concert with state or local watershed programs to reduce atrazine exposure. These remedies must be consistent with the EPA Office of Water's Total Maximum Daily Load (TMDL) program requirements but are enforceable under FIFRA through the 2003 Atrazine IRED and MOA.

As of mid-2009, two Missouri monitoring sites and one Nebraska site have exceeded the Agency’s level of concern. The two Missouri sites are in the South Fabius River and Youngs Creek watersheds. The Nebraska site is in the Big Blue River (Upper Gage) watershed.

Missouri Site Stewardship

  • The atrazine registrant, Syngenta, has collected detailed soil, slope and cropping maps, rainfall measurements, crop rotation patterns, and other useful information about the Missouri sites.

  • In 2005, Syngenta began discussions with stakeholders in Missouri to determine atrazine use patterns in these watersheds.

  • Syngenta is now conducting watershed stewardship and outreach activities with these growers and other stakeholders in the Missouri watersheds, including a series of label education and best management practice (BMP) meetings. Through these meetings, growers are learning how to modify their atrazine use to protect local water quality.

  • To evaluate the progress of this outreach effort, Syngenta will continue to monitor the two Missouri sites, as well as additional sites in these Missouri watersheds. This further monitoring will help EPA determine whether additional mitigation steps are necessary, such as changes in use rates or, potentially, prohibition of atrazine use.

Nebraska Site Stewardship

  • Since the Agency’s determination that the Missouri sites exceeded the level of concern, EPA has revised its model for evaluating the effects of atrazine in Midwestern streams and determined in 2009 that the Nebraska site has also exceeded the level of concern.

  • As a result of this determination, stewardship activities in the Nebraska watershed are being initiated and monitoring is continuing.

In a public peer review meeting on December 4-6, 2007, EPA consulted with the FIFRA Scientific Advisory Panel (SAP) on the approaches and methodologies of the atrazine ecological monitoring program, and the Agency's preliminary interpretations of monitoring results. As a body of independent scientific experts, the SAP provides advice and recommendations to the Agency on important scientific issues. The 2007 SAP recommendations can be found in docket EPA-HQ-OPP-2007-0934.

EPA revised its approach to the program based on recommendations from the 2007 SAP and presented its revised approach in another SAP meeting on May 12-15, 2009. The Agency is looking forward to receiving the 2009 SAP's final report and recommendations, which will be posted to the public docket (EPA-HQ-OPP-2009-0104) by late August 2009. Feedback from the SAP in this area will guide EPA’s work to refine the level of concern and identify, within the 1,172 watersheds vulnerable to atrazine exposure, a set of watersheds that may require additional monitoring and/or mitigation.

Sugarcane - A pilot atrazine monitoring program in water bodies associated with sugarcane crop production was initiated in 2005. Monitoring began in Louisiana in March 2005 and Florida in December 2005; however, the monitoring effort in Louisiana was delayed in the latter half of 2005 because of Hurricane Katrina. In 2008 the Agency received results from the pilot monitoring program, which are available in public docket EPA-HQ-OPP-2003-0367. Advice from the 2009 SAP cited above will help the Agency interpret these data to determine whether additional monitoring and/or mitigation is needed.

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Cancer

Status Update - July 2009

Based on the review of available scientific studies, EPA has determined that atrazine is not likely to cause cancer in humans. This determination is the result of a transparent process that invited public participation, solicited development and submission of the best scientifically available data, and allowed preeminent independent scientists to ensure that the Agency was using the highest quality data in its regulatory decision-making process. This determination is based on results from the full spectrum of animal test data that the Agency requires, as well as numerous research studies on atrazine’s mechanism of action.

In an abundance of caution, EPA is sponsoring epidemiological studies through the National Cancer Institute (NCI) to evaluate the potential for any association between atrazine exposure to people and cancer, even though rigorously conducted animal studies show that this result is unlikely.

Background

EPA has received several epidemiological cancer studies for atrazine and expects to receive and review other studies after they are completed. The Agency has received the following studies:

EPA expects to receive and review two additional epidemiological studies and analyses concerning atrazine and cancer from NCI's Agricultural Health Study in late 2009, including:

So far, the results of the completed Agricultural Health Studies have shown no relationship between atrazine and prostate cancer or non-Hodgkin’s lymphoma.

Based on recommendations from a 2000 FIFRA Scientific Advisory Panel (SAP) and substantiated in a 2003 SAP, the Agency determined that atrazine is “not likely to be carcinogenic to humans.” EPA considered all available animal and human epidemiological data available. Although atrazine has been linked to mammary gland tumors in rats, this mode of action does not lead to breast cancer in humans. However, as discussed earlier on this Web page, and as indicated in the 2003 Atrazine RED, EPA plans to convene an SAP meeting concerning atrazine and its possible association with carcinogenic effects in September 2010. At this SAP, the Agency will present its assessment of all available data about the potential carcinogenicity of atrazine - both epidemiology studies and laboratory animal studies – including its review of the most recent results from the National Cancer Institute’s Agricultural Health Study, anticipated for publication in 2010.

EPA will continue to review all new data submissions. If at any time results from any new studies raise significant questions, the Agency will convene another SAP meeting before all of the anticipated NCI Agricultural Health Study results concerning atrazine become available.

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Amphibians

Status Update - July 2009

EPA concluded in 2007 that atrazine does not adversely affect amphibian gonadal development based on a review of laboratory and field studies, including studies submitted by the registrant and studies published in the scientific literature. At this time, EPA believes that no additional testing is warranted to address this issue.

Background

In June 2003, after evaluating the available literature on the potential effects of atrazine on amphibian gonadal development, EPA concluded that there was sufficient information to formulate a hypothesis that atrazine exposure can affect amphibian gonadal development; however, there was insufficient information to refute or confirm that hypothesis, mainly because of the limitations of the study designs and uncertainties in the data. The Agency’s 2003 White Paper (PDF) (8 pp, 62k, about PDF) carefully evaluated the data from 17 laboratory and field studies, discussed remaining uncertainties in evaluating the potential effects of atrazine on amphibian development, and outlined future studies that could address these uncertainties. The FIFRA Scientific Advisory Panel (SAP) reviewed EPA’s White Paper and concluded that the Agency’s review was thorough, the conclusions were valid, and the approaches and criteria for new studies were appropriate. The SAP also agreed that additional studies were warranted and that a tiered testing approach was appropriate.

In response to a November 2004 Data Call-In (DCI) Notice from EPA, Syngenta, the principal atrazine registrant, developed a testing protocol for determining the effects of atrazine on amphibian gonadal development, and conducted two studies consistent with the first tier of testing described in the 2003 White Paper and the SAP review. In June 2007, Syngenta submitted to EPA its final report regarding the potential effects of atrazine on gonadal development of amphibians.

To ensure the quality and transparency of its assessment of atrazine’s potential to affect amphibian gonadal development, EPA solicited advice from the SAP at a second public peer review meeting on October 9 - 11, 2007. During this meeting, EPA presented its assessment of 19 laboratory and field studies, including the registrant-submitted studies and additional studies available in the public literature since the 2003 SAP. Of the 19 studies, only the two DCI studies submitted by the registrant incorporated all of the design elements recommended by the Agency and the 2003 SAP to address uncertainties identified in the 2003 White Paper. The 2007 SAP agreed with the Agency that, although both DCI studies contained some limitations, the overall design and conduct of the studies reflected a high degree of quality control that allowed them to be used to evaluate whether or not atrazine exposure affects amphibian gonadal development. The 2007 SAP also agreed with the Agency that other laboratory and field studies reviewed by the Agency did not fully account for experimental and environmental conditions that could influence relevant endpoints. The 2007 SAP's final report and recommendations are available in public docket EPA-HQ-OPP-2007-0498.

Based on the Agency’s thorough examination of the 19 studies and the 2007 SAP’s subsequent concurrence with the Agency’s assessment of those studies, EPA finds that atrazine does not adversely affect amphibian gonadal development. If new papers in the scientific literature regarding the potential effects of atrazine on amphibians become available, the Agency will review the information as part of its ongoing atrazine program.

Although EPA is not currently requiring additional testing of atrazine on amphibians, as discussed earlier on this Web page, EPA has begun a comprehensive reevaluation of atrazine’s ecological effects, including potential effects on amphibians, based on data generated since 2007. The Agency also is awaiting the results of studies examining the potential for any association between atrazine exposure to people and cancer, and has received and is analyzing additional monitoring data from community water systems and data from an ecological watershed monitoring program. If at any time atrazine data raise new risk concerns, EPA will modify its regulation of atrazine as appropriate.

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