Decision Documents for 

Atrazine 

Combined PDF document consists of the following: 

• Finalization of Atrazine IRED, and Completion of 

Tolerance Reassessment and Reregistration 

Eligibility Process (April 6, 2006) 

• Revised Atrazine IRED (October 31, 2003) 

• Atrazine IRED (January 2003) 
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

PREVENTION, PESTICIDES AND TOXIC 

SUBSTANCES 

MEMORANDUM 

DATE:	 April 6, 2006 

SUBJECT:	 Atrazine: Finalization of Interim Reregistration Eligibility Decision and Completion of 

Tolerance Reassessment and Reregistration Eligibility Process 

FROM:	 Diane Sherman, Chemical Review Manager
 

Special Review Branch
 

Special Review and Reregistration Division (7508P)
 

Office of Pesticide Programs
 

THRU:	 Anne Overstreet, Team Leader
 

Special Review Branch
 

Special Review and Reregistration Division (7508P)
 

Office of Pesticide Programs
 

TO: 	 Robert McNally, Branch Chief
 

Special Review Branch
 

Special Review and Reregistration Division (7508P)
 

Office of Pesticide Programs
 

CC:	 Debbie Edwards, Director
 

Special Review and Reregistration Division (7508P)
 

Office of Pesticide Programs
 

Catherine Eiden, Branch Chief
 

Reregistration Branch II
 

Health Effects Division (7509P)
 

Office of Pesticide Programs
 

Robert Perlis, Assistant General Counsel 

Andrea Medici, Attorney 

Pesticides and Toxic Substances Law Office (2333A) 

Office of General Counsel 

Page 1 of 2 
On January 31, 2003 EPA issued an Interim Reregistration Eligibility Decision (IRED) for the 

herbicide atrazine. On October 31, 2003 EPA issued a Revised IRED for atrazine. In these 

documents, the Agency assessed whether pesticide products containing atrazine as an active ingredient 

were eligible for reregistration considering all relevant issues except those relating to cumulative risks 

associated with potential exposures to atrazine and other structurally-related members of the chlorinated 

triazine class of pesticides, including simazine, propazine, and their three chlorinated degradates. These 

pesticides share a common neuroendocrine mechanism of toxicity which results in both reproductive and 

developmental consequences. Before tolerances can be considered fully reassessed or the Agency can 

make a final determination of reregistration eligibility, the Food Quality Protection Act (FQPA) requires 

the Agency to evaluate food tolerances on the basis of cumulative risk from substances sharing a 

common mechanism of toxicity. 

The Agency recently completed its cumulative risk assessment for the chlorinated triazine class 

of pesticides and has concluded that, with the mitigation measures in the 2006 simazine Reregistration 

Eligibility Decision and the 2003 atrazine IREDs, the cumulative risks associated with these pesticides 

are below the Agency’s level of concern. The cumulative risk assessment and supporting documents 

are available in the public docket EPA-HQ-OPP-2005-0481 located on-line in the Federal Docket 

Management System (FDMS) http://www.regulations.gov. Based on that assessment, EPA has now 

concluded, after taking into account the cumulative risks associated with exposures to all of the triazines, 

that all of the established tolerances for the triazine herbicides propazine, simazine, and atrazine meet the 

safety standard under Section 408(b)(2)(A) of the FFDCA, taking into account the provisions of 

Sections 408(b)(2)(C) and 408(b)(2)(D). 

In other words, the Agency has found that there is a reasonable certainty that no harm will result 

to the general U.S. population, infants, children, or other major identifiable subgroups of consumers 

from aggregate exposure (from food, drinking water, and non-occupational sources) to cumulative 

residues of atrazine and the other chlorinated triazine pesticides. With that finding, and the earlier 

findings contained in the 2003 IREDs for atrazine, the Agency has now completed its task under section 

4(g) of FIFRA of determining whether products containing atrazine are eligible for reregistration, and it 

has completed its reassessment of atrazine tolerances under section 408(q) of the FFDCA. Please note 

that individual registrations of products containing atrazine will not be considered reregistered until they 

have successfully completed product-specific reregistration. 

Page 2 of 2 
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF 

PREVENTION, PESTICIDES 

AND TOXIC SUBSTANCES 

CERTIFIED MAIL 

Dear Registrants: 

This is to inform you that the Environmental Protection Agency (hereafter referred to as 

EPA or the Agency) has completed its revised Atrazine Interim Reregistration Eligibility 

Decision (IRED), consistent with the Consent Decree, as amended, entered in Natural Resources 

Defense Council v. Whitman, Case Number C -99-3701 CAL, N. D. California (2002)). It does 

not alter the conclusions of the January 31, 2003 IRED document except as described below. 

There will be a 90-day public comment period for this document. At a later date, the Agency 

will publish a comprehensive atrazine IRED incorporating changes, if any, resulting from public 

comment and combining the January and October documents into one document. 

In August 2002, the court supervising the implementation of the Consent Decree granted 

a request from EPA and Natural Resources Defense Council (NRDC) that the Decree’s deadline 

for the atrazine IRED be extended. The new schedule included the completion of an IRED by 

January 31, 2003, and a revised IRED by October 31, 2003. The amended Consent Decree states 

that the revised Interim RED for atrazine must address the following: (1) data received by EPA 

prior to February 28, 2003, relating to the potential effects of atrazine on amphibian species; and 

(2) to the extent not addressed in the January 31, 2003 Interim RED, data, received prior to 

February 28, 2003, relating to the association between atrazine exposure and the incidence of 

prostate or other cancer in humans. The amended Consent Decree also specifies that EPA is to 

hold FIFRA Science Advisory Panel (SAP) meetings on these two issues. 

Ecological monitoring of watersheds was required in the January IRED due to the 

potential for community-level and population-level risk to aquatic ecosystems from atrazine. 

The January IRED states that to mitigate these ecological risks to aquatic communities, the 

Agency is requiring that atrazine registrants, in consultation with EPA, develop a program under 

which the registrants monitor for atrazine concentrations and mitigate environmental exposures 

if EPA determines that mitigation is necessary. The program will focus on watershed impacts of 

atrazine use. 

This revision to the January 31, 2003 IRED consists of three sections: 1) potential 

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association between atrazine exposure and the incidence of prostate cancer and other cancers in 

humans; 2) potential effects of atrazine on amphibian endocrinology and development; and 3) 

ecological monitoring and mitigation of atrazine in watersheds. In each section, this document 

summarizes the conclusions in the January IRED pertaining to the section, developments since 

the IRED, and next steps, as appropriate. The technical documents supporting these revisions 

are listed below and appended to this IRED. 

A. Review of Atrazine Cancer Epidemiology, 

B. Potential Effects of Atrazine on Amphibian Gonadal Development, 

C. Final Reports of the Atrazine Ecological and Monitoring Subgroups, 

D. Atrazine Ecological Subgroup Final Report: Recommendations for aquatic 

community Level of Concern (LOC) and method to apply LOC(s) to monitoring 

data, 

E. Microcosm and Mesocosm Data, 

F. Atrazine Toxicity Data for CASM Simulations, 

G. CASM Results: Steinhaus Similarity Toxicity Scenario, 

H. Comparison of Annual Average CASM Steinhaus Similarity for a Series of 

Chemographs Calculated with the Logistic Regression vs. Actual CASM 

Simulations, 

I. Comparison of Simulated Change in Annual Production for Phytoplankton, 

Periphyton, Macrophytes, Zooplankton, Benthic Invertebrates, and Fish for 

CASM Parameterizations, 

J. Decrease in Annual Total Production, 

K. Atrazine Ecological Monitoring Program Subgroup: Recommendations for 

Monitoring Design, and 

L. Assessment of Potential Mitigation Measures for Atrazine, February 13, 2003. 

Potential Association Between Atrazine Exposure and Prostate Cancer and Other Cancers 

in Humans 

January 31, 2003 IRED 

The Agency’s human health risk assessment for the January 31, 2003, IRED did not 

include a quantitative risk assessment for cancer due to a determination by the EPA, consistent 

with conclusions reached by the SAP (June 2000), that it is unlikely that atrazine's cancer mode 

of action in the Sprague-Dawley rat is operative in humans. EPA’s Cancer Assessment Review 

Committee (CARC), in accordance with the 1999 Draft Guidelines for Carcinogen Risk 

Assessment, classified atrazine as “not likely to be carcinogenic to humans.” 

The review of the cancer epidemiology study for the January 31, 2003, IRED did, 

however, include epidemiological data on workers at the Syngenta St. Gabriel Louisiana plant 

where atrazine is manufactured. The study reported a statistically significant increase in the 

incidence of prostate cancer among plant workers. The Agency, upon review of this study, 

requested additional information on the exposure profile of the employees diagnosed with 

2
prostate cancer and this information was provided and reviewed. Based on this review, it 

appeared that most of the increase in prostate cancer incidence at the St. Gabriel plant was likely 

due to intensive prostate specific antigen (PSA) screening of employees. The study was 

insufficiently large and had limitations that prevent ruling out atrazine as a potential contributor 

to the increase observed. On balance, however, a role for atrazine seemed unlikely because 

prostate cancer was found primarily in current employees who received intensive PSA screening; 

there was no increase in advanced tumors or mortality; and proximity to atrazine manufacturing 

did not appear to be correlated with risk. 

Other cancers besides prostate were found to have an elevated, though not statistically 

significant, increase in risk at the St. Gabriel plant. Other studies have suggested an increased 

risk for ovarian, breast, and other cancers, including non-Hodgkin’s lymphoma (NHL). 

However, EPA had previously concluded that these studies were at best preliminary and should 

not serve as a basis for implicating atrazine as a human carcinogen due to their methodological 

limitations. 

July 17, 2003 SAP 

To further analyze the question of exposure to atrazine and prostate cancer, an SAP 

meeting was held on July 17, 2003 (http://www.epa.gov/scipoly/sap/index.htm). Given the 

limited nature of the new cancer data that stimulated the request for a second SAP meeting, 

EPA’s submission to the SAP focused primarily on the new prostate cancer data rather than the 

epidemiological data that the SAP in 2000 had judged inconclusive or later studies received 

since 2000 that EPA found to be inconclusive. EPA asked the Panel to comment on the 

Agency’s conclusion regarding prostate cancer and particularly the preliminary results from a 

nested case-control study of the St. Gabriel manufacturing plant in Louisiana. In addition to this 

study, the SAP was provided with other epidemiological studies on atrazine exposure and 

prostate cancer, a review by the Agency discussing the St. Gabriel data and epidemiological data 

bearing on prostate cancers, comments from four external peer reviewers, a Syngenta-sponsored 

expert panel review, and comments by the Natural Resources Defense Council. As stated in the 

January IRED, EPA’s view of the study was that the increase in PSA screening for the St. 

Gabriel workers could explain the increase in prostate cancer observed in these workers and 

therefore a role for atrazine seemed unlikely. EPA acknowledged, however, that due to 

limitations in the St. Gabriel study, atrazine could not be ruled out as a potential causal factor. 

The SAP’s analysis of the St. Gabriel study differed to a degree from the Agency’s 

conclusion. The SAP did conclude that “the increase in Prostate Specific Antigen (PSA) 

screening at the St. Gabriel plant likely led to an increase in the detection of cases of prostate 

cancer.” Further, the Panel noted that “[s]ubstantive and persuasive arguments have been made 

to support the EPA’s conclusion that PSA screening could explain the observed increase in 

prostate cancer incidence in the workers.” Nonetheless, the Panel did not believe there was 

sufficient evidence to conclude that it was “unlikely” that atrazine had a role in the increased 

prostate cancer cases seen in the St. Gabriel study “given the severe limitations of the St. Gabriel 

study, particularly those pertaining to small sample size, questionable exposure assessment and 

3
lack of an appropriate comparison group.” According to the SAP, PSA screening may be only a 

“partial explanation” for the increase in prostate cancer seen in the St. Gabriel study and that 

“atrazine cannot be ruled out as a potential cause.” 

The Agency agrees with the SAP’s analysis and has rewritten its conclusion as follows: 

The increase in prostate cancer incidence at the St. Gabriel plant in Louisiana is 

consistent with the intensive PSA screening. This is because prostate cancer was found 

primarily in active employees who received intensive PSA screening, there was no 

increase in advanced tumors or mortality, and proximity to atrazine manufacturing did 

not appear to be correlated with risk. No evidence was identified, such as dose-response 

evidence, that permit a determination that some of the increase was likely due to 

exposure to atrazine although atrazine exposure cannot be ruled out at this time as a 

cause. However, the study was insufficiently large and suffered from other limitations 

that prevent a determination that all of the increase in prostate cancer was probably due 

to the intensive screening program. Therefore, EPA concludes that the St. Gabriel study 

does not contribute any evidence supporting atrazine as a likely human carcinogen. (see 

Appendix A) 

The SAP suggested that the Agency consider additional analysis of the St. Gabriel 

cohort. However, the resulting sample size would still limit the opportunity to draw further 

conclusions. The Agency questions whether additional analysis is warranted for other potential 

risk factors (such as smoking, diet and previous work history, and non-occupational or preemployment exposure to triazine herbicides). Because of the way the study was designed, this 

information is not available to investigators and it may not be feasible to obtain such information 

for the St. Gabriel workers. 

The other epidemiologic studies investigating the relationship between atrazine exposure 

and prostate cancer did not alter the Panel's opinion that the evidence presented is inadequate to 

support the Agency's conclusion of atrazine as an "unlikely" cause of prostate cancer seen in the 

St. Gabriel study. One study by Mills (1998) found a borderline statistically significant positive 

association between atrazine use by county with prostate cancer incidence rates in African 

American males. A second study by Alavanja et al. (2003) showed no association of selfreported atrazine exposure with prostate cancer in cohort analysis of pesticide applicators. 

Epidemiological Data on Other Cancers 

EPA has re-reviewed the epidemiological data regarding atrazine and cancer that were 

examined for the SAP meetings on atrazine in 2000 and 2003. EPA has also reviewed data that 

have become available since the latest meeting of the SAP in 2003. The results of those reviews 

are also summarized in Appendix A to this document. In brief, the Agency does not find any 

results among the available studies that would lead us to conclude that a potential cancer risk is 

likely from exposure to atrazine. 

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Even though the epidemiological evidence and animal data, when viewed separately, do 

not support a positive cancer finding for atrazine, EPA examined the totality of animal and 

human data to determine if that approach showed that atrazine was likely to cause a carcinogenic 

response in humans. Specifically, EPA reviewed the available animal data to determine if a 

mechanism could be identified which supports the biological plausibility of atrazine as a human 

carcinogen taking into account the tumors that were identified in the epidemiological data. This 

review showed that (1) lymphomas, including NHL, were generally not seen in atrazine animal 

bioassays; (2) a mechanistic role for atrazine contributing to NHL has not been identified in 

laboratory studies; (3) tumors at any endocrine site other than mammary gland tumors in female 

SD rats (e.g., prostate, ovarian tumors) have not been identified in atrazine bioassays; (4) the 

SAP concluded in 2000 that the mammary gland tumors in rats caused by atrazine are produced 

via a mechanism not relevant to humans; and (5) the endocrine tumors that have been raised in 

epidemiological studies (other than mammary gland tumors) can not be biologically tied to 

atrazine’s mode of action (i.e., decrease prolactin, decrease luteinizing hormone (LH) and 

suppression of ovulation). Thus, at this time, joint consideration of the available animal cancer 

and mode of action data and epidemiological studies, does not indicate that atrazine is likely to 

cause cancer in humans. 

Conclusion 

In the January 31, 2003 IRED, EPA concluded that, considering the animal data and the 

human epidemiological data, atrazine is “not likely to be carcinogenic in humans”. That 

conclusion allowed EPA to find that there is a reasonable certainty of no harm from exposure to 

atrazine so far as cancer risk is concerned. Results in the St. Gabriel study and other recent 

epidemiological studies regarding atrazine’s potential link to cancer do not alter that conclusion. 

Further, any weight attributable to these data is weakened by the data in animals that fail to 

reveal any mechanism of action for atrazine consistent with the cancers observed in the studies. 

Accordingly, EPA concludes that atrazine is not likely to be a human carcinogen." 

Next Steps 

Since the July 2003 SAP meeting, EPA has received two new pieces of information: (1) a 

report from the National Cancer Institute (NCI) re-analyzing previous epidemiologic studies of 

atrazine and non-Hodgkin=s lymphoma using hierarchical techniques to adjust for the effects of 

multiple exposures; and (2) a nested case-control study conducted for Syngenta of workers at the 

St. Gabriel plant using more detailed job histories to evaluate exposure indices. The Agency 

plans to conduct a comprehensive review of both studies. EPA’s preliminary view of these 

studies is discussed in Appendix A. EPA is also expecting to receive additional epidemiological 

studies and analyses concerning atrazine and cancer from the NCI’s Agricultural Health Study in 

the next one to two years. These studies and analyses include the following: an update of the 

Agricultural Health Study on prostate cancer capturing additional prostate cancer cases; an 

analysis of all the non-Hodgkin’s lymphoma cases reported in the Agricultural Health Study; and 

a special analysis of all cancers related to atrazine exposure in the same Agricultural Health 

Study cohort. The latest projection is that the NCI will complete these studies and analyses in 

5
mid-2005. 

After all of the information has been submitted and reviewed, the Agency plans to 

convene another SAP meeting concerning atrazine and its possible association with carcinogenic 

effects. At that meeting, EPA intends to present the SAP with all of the data bearing on atrazine 

and cancer, including the old and new epidemiology studies. In the meantime, EPA will 

continue its review of all new data submissions. If at any time, results from any of the new data 

submissions raise significant questions that would benefit substantially from SAP review prior to 

submission of all of the data, the Agency will hold a SAP meeting before all aspects of the 

Agricultural Health Study are completed. 

EPA intends to thoroughly review any SAP report from any future meeting, once issued, 

and to revise its determinations regarding the cancer potential of atrazine, as necessary. Any 

revisions will be included in either a revision to the October 31, 2003 IRED or the final 

reregistration decision for atrazine depending on the timing of the future SAP meeting relative to 

issuance of the final atrazine reregistration decision. 

Potential Effects of Atrazine on Amphibian Endocrinology and Development 

January 31, 2003 IRED 

In the ecological risk assessment for the January 31, 2003 IRED, the Agency did not 

suggest that endocrine disruption, or potential effects on endocrine-mediated pathways, was 

regarded as a regulatory endpoint for ecological effects. Nor did the Agency have reliable 

evidence at that time to state that atrazine caused endocrine effects in the environment. The 

IRED stated that based on the existing uncertainties in the available database, atrazine should be 

subject to more definitive testing once the appropriate testing protocols have been established. 

The Agency was aware that several pertinent studies were being performed by researchers that 

may reduce some of the uncertainties in understanding potential atrazine effects on amphibian 

endocrinology and reproductive and developmental responses. 

June 17-20, 2003 SAP 

Since the January IRED, the Agency has conducted a comprehensive evaluation of the 

available data regarding the potential effects of atrazine on amphibian gonadal development and 

presented its assessment for external peer review to a SAP in June 2003. In a May 29, 2003 

white paper, the Agency summarized seventeen studies consisting of both open literature and 

registrant-submitted laboratory and field studies involving both native and non-native species of 

frogs (see Appendix B). In its white paper the Agency concluded that none of the studies fully 

accounted for environmental and animal husbandry factors capable of influencing endpoints that 

the studies were attempting to measure. The Agency also concluded that the current lines-ofevidence did not show that atrazine produced consistent effects across a range of exposure 

concentrations and amphibian species tested. 

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Based upon this assessment, the Agency concluded and the SAP agreed that there is 

sufficient evidence to formulate a hypothesis that atrazine exposure may impact gonadal 

development in amphibians, but there are currently insufficient data to confirm or refute the 

hypothesis (http://www.epa.gov/oscpmont/sap/2003/June/junemeetingreport.pdf). Because of 

the inconsistency and lack of reproducibility across studies and an absence of a dose-response 

relationship in the currently available data, the Agency has determined that it does not change 

the conclusions reached in the January 31, 2003 IRED regarding atrazine’s effects on 

amphibians. 

Next Steps 

Based on the conclusions from the Agency’s white paper and recommendations of the 

SAP, the Agency will seek additional data to reduce uncertainty regarding the potential risk to 

amphibians (http://www.epa.gov/oscpmont/sap/2003/june/dataevaluationreports.htm). This data 

collection will follow the multi-tiered process outlined in the Agency’s white paper. This 

approach to collecting additional information through further studies, which was endorsed by the 

SAP, can be used to address uncertainties associated with the potential causal relationships 

between atrazine exposure and gonadal development and characterize the nature of any 

concentration-response relationship. 

Ecological Monitoring and Mitigation of Atrazine in Watersheds 

January 31, 2003 IRED 

The ecological risk assessment for the January IRED stated that the Agency has 

ecological risk concerns from the use of atrazine and identified the potential for community-level 

and population-level risk to aquatic ecosystems at prolonged concentrations of atrazine from 10 

to 20 ppb. To mitigate these ecological risks to aquatic communities and to determine that 

atrazine is eligible for reregistration, the Agency required that atrazine registrants, in 

consultation with EPA, develop a program under which the registrants monitor for atrazine 

concentrations and mitigate environmental exposures if EPA determined that mitigation is 

necessary. This program would focus on watershed impacts of atrazine use. 

The January IRED further stated that the program will include an appropriate ecological 

level of concern (LOC), identified by EPA; development of a protocol for a monitoring program 

that specifies the frequency, location, and timing of sampling, as well as an appropriate 

coordination with Total Maximum Daily Load (TMDL) programs; triggers for mitigation 

measures; and description of mitigation measures that will be taken if triggers are exceeded. 

This monitoring and mitigation program would be designed, conducted and implemented on a 

tiered watershed level and must be consistent with existing state and federal water quality 

programs. 

Follow-up to January 31, 2003 IRED 

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The following description highlights how EPA developed the specifics of the ecological 

monitoring and mitigation program consistent with the January 2003 IRED. The Office of 

Pesticide Programs, the Office of Research and Development, and the Office of Water 

collaborated to integrate and develop this program. 

Level of Concern (LOC) 

The sensitive endpoint in the ecological assessment for atrazine is a change in the 

structure and function of primary producers in the aquatic community. Concentrations of 

atrazine that affect plant productivity and community structure typically occur at levels lower 

than those that directly intoxicate fish and aquatic invertebrates. By focusing on aquatic plant 

community structural changes, the most sensitive endpoint, the Agency intends to protect fish 

and invertebrates from the direct effects of atrazine as well as the effects that atrazine could have 

on the habitat and food sources of aquatic animals (see Appendices C- K). 

The Level of Concern (LOC) was derived to ensure that the atrazine concentrations in 

watersheds will not cause significant changes in aquatic plant community structure. The LOC is 

based on an analysis of 25 microcosm and mesocosm studies cited in the Final Report of a report 

provided in Appendix D. To establish the LOC, it was necessary to quantify the results of the 

mesocosm and microcosm studies by rating their reported results based on the significance of the 

effects on aquatic plant productivity and community structure. Each study was analyzed to 

establish the reported effect(s) and the atrazine exposure profile, which reflects the magnitude, 

frequency and duration of atrazine concentrations in the study. This analysis revealed a wide 

range of study designs and quality and also indicated that a wide range of atrazine exposure 

profiles could result in significant change in aquatic community productivity and structure. A 

method was developed to separate the reported results on plant community productivity and 

structure observed in these studies into those that were significant versus those with slight to noeffects. 

Since atrazine exposure profiles in natural systems, in this case streams, will typically be 

complex, it was necessary to develop a method to analyze monitoring data to determine when 

monitored exposure profiles are functionally-equivalent to those profiles observed in mesocosm 

and microcosm studies showing significant changes when the monitored profiles are 

functionally-equivalent to those studies that showed no significant effects. 

Using a range of atrazine exposure profiles representative of those that caused significant 

effects in the microcosm and mesocosm studies, as well as those that did not result in significant 

effects, an ecological food chain model that predicts changes in aquatic communities in streams 

(in this case, Comprehensive Aquatic Systems Model, CASM), was used to develop the means 

of interpreting whether or not any atrazine exposure profile observed in the monitoring study 

would likely be associated with a significant effect on aquatic communities. These analyses 

determined that a community similarity index (CSI) that quantifies the average changes in 

biomass for plant species of the modeled aquatic community, is the most useful model parameter 

to segregate those mesocosm and microcosm studies that exhibited significant effects from those 

8
that did not. Conceptually, this index is consistent with the observed effects of atrazine on 

primary producers in aquatic ecosystems. More specifically, through this analysis it was 

determined that an average CSI change of 5% or greater over the course of a study reasonably 

discriminated micro- and mesocosm exposure profiles associated with significant effects (i.e., 

irreparable changes to ecosystems) from those that did not show significant effects. 

Consequently, these analyses establish the LOC as any measured atrazine exposure 

profile obtained through a monitoring study that would result in a predicted 5% or greater 

average change in the CSI through the use of CASM. Additional analyses over the duration of 

the three year monitoring study will evaluate the use of additional aquatic community models 

(e.g., Aquatox), and comparable modeled indices, to provide additional model options for States, 

Tribes or other parties to evaluate data that may be collected in other monitoring programs. 

Monitoring Program Protocol 

The monitoring protocol is initially focused on flowing water bodies (i.e., streams) 

associated with corn and sorghum production (see Appendix K). Future efforts (see below) will 

address the need to monitor estuaries and water bodies associated with sugarcane production. In 

addition, results of raw water monitoring from the on-going atrazine monitoring program for 

drinking water, as described in the January 31, 2003 IRED, will be analyzed to determine its 

potential utility in evaluating potential ecological effects in static water bodies. 

The purpose of the monitoring program in flowing waters is to estimate the magnitude 

and extent to which water bodies with the greatest potential vulnerability to atrazine exposure 

(primarily based on atrazine use and runoff potential) are exceeding the level of concern 

consistent with the atrazine ecological risk assessment, which was described above. The initial 

analyses identified three tiers of watersheds relevant to atrazine use in corn and sorghum. The 

first tier of approximately 10,000 watersheds had some level of atrazine use on corn and 

sorghum. The watersheds identified in this assessment were primarily at the 5th, or Hydrologic 

Unit Code (HUC)-10/11, level of a hierarchal system of mapping watersheds established by the 

United States Geological Survey (USGS). At this level, watersheds are typically 40,000 to 

250,000 acres in size. From this first tier, a second tier of 5,860 HUC-10/11 watersheds was 

identified based on use intensities of 0.25 lb active ingredient (ai)/county acre or higher. From 

this second tier of watersheds, a third tier of 1,172 watersheds was identified based on their 

predicted potential to be among the most vulnerable to atrazine surface water loading from use 

on corn and sorghum. Through the development of a statistically-based survey design, EPA then 

selected 40 HUC-10/11 watersheds which will give a statistical representation of the third tier of 

1,172 such watersheds predicted to be most potentially vulnerable. These 40 monitored 

watersheds are located in 10 states: Ohio, Indiana, Kentucky, Illinois, Iowa, Missouri, Nebraska, 

Minnesota, Tennessee, and Louisiana. The selected watersheds averaged 129 square miles in 

size, with a median size of 121 square miles. Monitoring sites (index sites) will be located in 

flowing water bodies within the 40 watersheds. Two years of monitoring results from these sites 

will be compared to the LOC values. The registrant shall collect monitoring samples every 4 

days prior to, during, and following the growing season. In addition, the registrant is required to 

9
monitor 10 watershed sites daily following flow events to better estimate temporal variability for 

the data collected in the remaining 30 watersheds. Based on the results from the two-year 

monitoring study in each watershed, as interpreted by the LOC, the Agency will evaluate the 

need for more monitoring and/or mitigation actions in the 40 HUC-10/11 watersheds and the 

implications, if any, for the larger set of 1,172 most potentially vulnerable watersheds. 

Future Monitoring Decisions for Other Water Bodies 

Estuaries will not be monitored in 2004. Discussions will be conducted with the Oceans 

and Coastal Protection Division in the Office of Wetlands, Oceans, and Watersheds (OWOW) to 

review all relevant data to determine whether and to what extent monitoring for levels of atrazine 

should be undertaken for estuaries. The role of dilution and transport in estuaries must be 

determined. It may be possible to gather some information on these parameters by looking at 

nitrate concentrations or other chemical as a marker to ascertain how to approach an estuary 

monitoring program. This analysis will be completed by March 2004. If it is determined a 

monitoring study is required, it is recognized additional efforts will be necessary to develop a 

monitoring program. 

To evaluate the potential for ecological concerns in static water bodies (i.e., lakes and 

reservoirs), raw water data on atrazine concentrations collected from the approximately 140 

Community Water Systems that are being monitored for human health concerns will initially be 

used. In addition, the registrant will provide historical data from the Voluntary Monitoring 

Program (VMP) sites. The methods used to determine the LOC for flowing water bodies are 

amenable for use in static water bodies. The EPA must determine on a statistical and ecosystem 

basis to what extent the monitoring data from the drinking water monitoring program should be 

interpreted for a given water body and how statistical inferences from the results of this set of 

static water bodies can be made to a larger population of potentially vulnerable static water 

bodies. This information will provide the basis for developing a monitoring strategy for static 

water bodies. 

A strategy will be developed to select the most appropriate locations and number of sites 

for monitoring atrazine in sugarcane growing areas. The sugarcane use area is a unique situation 

which has clear freshwater and estuarine issues. As a pilot, the registrant has offered to monitor 

four additional sites distributed between Louisiana and Florida with one being the Iberville 

Community Water System already designated for increased monitoring in the drinking water 

program. The selection of these pilot sites for evaluating potential ecological effects and the 

protocol for monitoring will be completed by March 2004. 

Triggers for Mitigation Measures in Flowing Water Bodies 

For the 40 watersheds, the registrant shall monitor an index site within the watershed for 

two years, regardless if a decision to initiate remediation occurs in the first year. If monitoring 

within a watershed indicates exceedences of the 5% average CSI threshold, based on CASM 

model results, in each of the two years, the registrant will initiate and conduct a TMDL or 

10
comparable watershed management program within the particular watershed where the 

exceedence occurred, consistent with the state’s ongoing TMDL or watershed program. If a 

TMDL or comparable watershed management program is already in place by USDA, state, or 

other entity in a given watershed, the registrant will then work with these existing programs to 

address the atrazine exceedence. If an exceedence occurred in the first year of sampling within a 

watershed, the registrant will, at a minimum initiate stewardship outreach, preferably through an 

existing USDA or state-sponsored watershed management program if one exists. 

If an index site in a watershed has exceeded the similarity threshold over a two year 

period, the registrant shall initiate and conduct a TMDL (or similar) program to reduce atrazine 

concentrations associated with the stream reach at the index site by additional monitoring and 

managing atrazine uses in those portions of the watershed that feed into the index site and result 

in the exceedences. At the same time, the registrant shall conduct additional monitoring at other 

sites in the watershed suspected to be similar to the index site in order to determine if other water 

bodies in the watershed also exceed the 5% similarity threshold. If these areas are determined to 

exceed the similarity threshold, then the registrant shall initiate and conduct TMDL (or similar) 

mitigation in those areas. 

The registrant must also initiate and conduct remediation immediately in any watershed 

which shows an exceedence of $ 15% of the CSI rather than wait for a second year of data. 

However, monitoring will still continue at the original index site in the second year. 

If monitoring results indicate an exceedence in one of the two years for a given index site 

within a watershed, a decision regarding additional monitoring or other watershed management 

activities will be based on the specific data for the location and the results of the overall study. 

The data derived from all of the 40 watersheds will provide information needed to better quantify 

and interpret sampling variability in the context of the exceedence threshold. These future 

analyses will inform decision criteria for those cases where variability in monitoring data 

overlaps uncertainties in the LOC derivation. 

For an index site within a watershed, if monitoring results indicate no exceedences of the 

5% average similarity threshold index based on CASM model results in each of the two years, 

then no further action will be required in the watershed. 

For all of the data collected in the 40 watersheds, interpretation of monitoring data after 

two years would include an assessment as to whether or not unusual meterological conditions 

(e.g., high or low rainfall) existed during the monitoring period. This could require a third year 

of sampling to make an informed decision on a watershed's condition. 

In addition, if States or Tribes use the same or comparable LOC and monitoring protocols 

(e.g., comparable sampling frequencies and analytical techniques) at a selected stream reach 

outside of the 40 watersheds, as described in the ecological and atrazine monitoring subgroup 

reports (Appendix C-J), as well as, employ decision criteria comparable to those described 

above, the registrant will initiate and conduct a TMDL or comparable watershed management 

11
program within that watershed if the State or Tribal data shows an exceedence of the LOC for 

two years, consistent with the state’s ongoing TMDL or watershed program. 

After the Agency receives the data from the 40 watersheds, it will be analyzed to 

interpret the status of the 1,172 Tier 2 watersheds. Due to the nature of this monitoring design it 

will be possible to make statistical inferences with the data collected from the 40 watersheds as 

to the magnitude and extent to which LOC exceedences could be occurring in the remaining tier 

of 1,172 watersheds considered to be the most potentially vulnerable. After these statistical 

inferences are completed, a decision about monitoring in the remaining 1,172 vulnerable 

watersheds will be made, with the understanding it is possible that further monitoring and/or 

mitigation may be required of the registrant in these other watersheds. 

Description of Mitigation Measures 

The specific techniques to be employed by the registrant to reduce atrazine loads in a 

watershed that has atrazine concentrations that exceed the LOC will be watershed specific and 

undertaken in partnership with any existing watershed management programs. The registrant 

will follow steps that are typically employed in the Clean Water Act TMDL program or similar 

management programs as follows: 

1. Problem Identification - 

Identify pollutant causing impairment and impaired water body and determine the 

pollutant reductions needed to achieve water quality standards (note that in this 

specific situation exceedence of the atrazine LOC will have already established an 

impairment and a cause, with the understanding that for a given water body 

additional pollutants could also be contributing to biological impairment). 

2. Current Situation and Desired Objective -

Indicate desired outcome of TMDL process.

3. Source Assessment - 

Identify pollution source and contribution to impairment.

4. Allocation of loads -

 Allocate the pollutant loadings among the various pollutant sources. 

5. Implementation -

Describe actions to mitigate the sources of pollution (e.g., best management 

practices). 

6. Follow-up Monitoring -

Determine effectiveness of implemented mitigation measures.

7. Feedback Mechanism - 

12
Review of mitigation measures during implementation period to determine if 

adjustments are needed. 

The Clean Water Act requires that States identify waters that fail to attain water quality 

standards and establish TMDLs at levels that attain or maintain their water quality standards. 

EPA is required to review and approve or disapprove the list of impaired waters and TMDLs. If 

EPA disapproves the State’s list or the TMDL, EPA is required to identify the impaired waters 

or establish TMDLs. The States and EPA establish TMDLs in a particular watershed by 

determining pollutant loads that will allow the attainment of water quality standards, analyzing 

existing pollutant loads and sources, and specifying the pollutant load reductions necessary to 

attain water quality standards. TMDLs are implemented through existing Federal, State or local 

requirements and programs. EPA encourages TMDLs that are established and implemented as 

part of an overall watershed strategy for improving water quality. 

The Agency expects that the TMDL process (or similar watershed management program) 

will result in mitigation measures that, when implemented, will effectively lower the level of 

atrazine to below the level of concern. These mitigation measures could include: buffer zones, 

different application or incorporation methods, restrictions on the timing of application due to 

rain, and lower application rates. Implementation of these controls also will include 

confirmatory follow up monitoring to insure that the atrazine levels are below the LOC. Given 

the rapid progress the States have made by incorporating TMDL approaches in watershed 

management programs, EPA is confident that management activities undertaken by the registrant 

consistent with meeting the loading reductions identified in a TMDL are expected to be 

successful in reducing loadings of atrazine. Since 1996, more than 9000 TMDLs have been 

established and approved, leading to activities that have improved water quality. Pollutant 

loadings have been reduced and water quality improved as reported by the Office of Water's 

Office of Wetlands, Oceans and Watersheds (see http://www.epa.gov/owow/tmdl/). In the 

unlikely event that implementation of loading reductions identified in TMDLs is not effective, 

the Agency reserves the right to take further action under FIFRA to mitigate this risk from 

atrazine and will consider, as appropriate, the benefits of atrazine use in the particular watershed. 

Benefits of Atrazine Use 

The total or national economic impact resulting from the loss of atrazine to control grass 

and broadleafed weeds in corn, sorghum and sugarcane would be in excess of 2.0 billion dollars 

per year if atrazine were unavailable to growers (Appendix L, “Assessment of Potential 

Mitigation Measures for Atrazine”, February 13, 2003). 

A watershed-specific analysis has not been factored into this assessment because of the 

uncertainty surrounding potentially impacted watersheds and any required mitigation. However, 

economic impacts could be expected to parallel those for drinking water as described below. 

Specifically, EPA analyzed what would be the impact to the corn industry in areas in 

13
watersheds contributing to Community Water Systems which find atrazine concentrations 

exceeding the Agency's level of concern, and found that growers would incur an average loss of 

9 bushels per acre (nationwide corn yield averaged 138 bushels per acre in 2001), as well as an 

increased cost for a replacement herbicide. This yield loss plus increased herbicide cost may 

result in an average estimated loss of $28 per acre. This translates to a yearly loss of 1.6 billion 

dollars of lost revenue annually nationwide. 

Likewise, the impact to the sugarcane industry would also be substantial. If growers in 

the watersheds contributing to the Community Water Systems which find atrazine concentrations 

exceeding the Agency's level of concern, no longer had atrazine available to them, a 10 to 40 

percent crop loss would be incurred along with an increase in alternative herbicide cost. This 

translates to a yearly loss of $89.5 million but could be as much as $343.6 million if a 40 percent 

loss were realized. 

Finally, if atrazine were eliminated from the market, the most likely chemical broadleaf 

weed control options would be post-emergence applied herbicides (dicamba, 2,4-D, bromoxynil, 

and prosulfuron). Post-emergence application of herbicides carries certain risks. These include: 

1) greater competition of the weeds with the crop early in the season as weed control is delayed 

into the growing season; 2) crop injury from herbicides applied directly to the emerged crop and 

weeds; and 3) if the opportunity to apply the herbicide is missed due to weather or some other 

factor, there are fewer or no emergency remedies for weed control. Thus, there are nonmonetary costs that would be associated with the loss of atrazine as well as the substantial 

financial impacts. 

Determination of Interim Reregistration Eligibility 

The Agency has determined that atrazine products are eligible for reregistration provided 

that: (i) the circumstances described in this document (including implementation of any 

ecological risk mitigation measures identified through the monitoring program) are realized; (ii) 

any current data gaps and additional data needs are addressed; and, (iii) the consideration of the 

cumulative risk for the triazines supports a final reregistration eligibility decision. Further we 

have concluded that during the period of data collection and risk mitigation measures called for 

in this document, the benefits of continued use of atrazine will outweigh any potential ecological 

risk. 

Although the Agency has not considered the cumulative risk for all the triazines, the 

Agency is issuing this amendment to the interim reregistration eligibility decision now in order 

to identify risk reduction measures that are necessary to support the continued use of atrazine. 

Based on the current evaluation of atrazine, the Agency has determined that atrazine products, 

unless used in accordance with the conditions of this document, would present risks inconsistent 

with FIFRA. Accordingly, should a registrant fail to implement any of the risk mitigation 

measures identified in this document, the Agency may take further regulatory action to address 

the risk concerns from the use of atrazine products. 

14
Because the Agency has not yet considered cumulative risk for all of the triazines, this 

reregistration eligibility decision does not fully satisfy the reassessment of the existing atrazine 

food residue tolerances as called for by the Food Quality Protection Act (FQPA). When the 

Agency has completed the cumulative assessment, atrazine tolerances will be reassessed in that 

light. At that time, the Agency will reassess atrazine along with the other triazine pesticides to 

complete the FQPA requirements and make a final reregistration eligibility determination. By 

publishing this interim decision on reregistration eligibility and requesting mitigation measures 

now for the individual chemical atrazine, the Agency is not deferring or postponing FQPA 

requirements; rather, EPA is taking steps to assure that uses which exceed FIFRA’s unreasonable 

risk standard do not remain on the label indefinitely, pending completion of assessment required 

under the FQPA. This decision does not preclude the Agency from making further FQPA 

determinations or tolerance-related rulemakings that may be required on this pesticide or any 

other in the future. 

What Registrants Need to Do 

In order to be eligible for reregistration, registrants need to implement the risk mitigation 

measures outlined above, which include, among other things, development and submission of the 

following: 

Potential Effects of Atrazine on Amphibian Endocrinology and Development 

Phase I: Response of larval Xenopus laevis to estradiol: assessment of 

development and gonadal morphology. 

Response of larval Xenopus laevis to atrazine: assessment of development 

and gonadal morphology. 

Phase II:* Response of larval Xenopus laevis to atrazine: assessment of gonadal and 

plasma sex steroid concentrations. 

Phase III:* Response of larval Xenopus laevis to atrazine: assessment of gonadal 

aromatase activity. 

Phase IV:* Response of larval Xenopus laevis to atrazine and an aromatase inhibitor: 

assessment of development, gonadal morphology, sex steroid 

concentrations and aromatase activity. 

Phase V:* Response of Rana pipiens to atrazine: assessment of reproductive fitness. 

* Conducting the studies in phases II through V are conditional on the results from the 

previous phase indicating an effect. For example, if morphological abnormalities are observed in 

the gonads of larval Xenopus laevis after exposure to atrazine (Phase I) then the Phase II studies 

on gonadal and plasma sex steroid concentrations would be conducted. However, if the Phase I 

studies show negative results then the registrant does not need to proceed with the subsequent 

15
study. EPA requests to review all of the protocols before the studies are initiated. 

Ecological Monitoring and Mitigation of Atrazine in Watersheds 

Atrazine Monitoring For Potential Ecological Effects on Aquatic Communities: Part 1. 

Flowing Water Bodies in Corn and Sorghum Use Areas. 

Atrazine Monitoring For Potential Ecological Effects on Aquatic Communities: Part 2. 

Water Bodies in Sugarcane Use Areas. 

Atrazine Monitoring For Potential Ecological Effects on Aquatic Communities: Part 3. 

Static Water Bodies. 

Atrazine Monitoring For Potential Ecological Effects on Aquatic Communities: Part 4. 

Estuarine Water Bodies. 

Data Call-In data for the ecological monitoring of watersheds will be sent to Office of 

Pesticide Programs (OPP) and Office of Water (OW), as well as the State or Tribe where the 

data are collected. Once the monitoring data has been quality controlled it will be posted in 

OW’s publically available STORET database. 

If you have questions on this document, please contact the Chemical Review Manager, 

Eric R. Olson at (703) 308-8067. 

Sincerely, 

Betty Shackleford, Acting Director 

Special Review and Reregistration Division 

12 Attachments 

16
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES

 OFFICE OF PESTICIDE PROGRAMS

 SPECIAL REVIEW and REREGISTRATION 

DIVISION 

(7508C)

 Debra Edwards, Ph.D., Director 

Correction to the Existing Stocks Section in the January 2003 Atrazine IRED 

The October 1, 2003 deadline for distribution of product by persons other than the registrant in Existing 

Stocks provision in Chapter V, Section C of the January 2003 Atrazine IRED is incorrect. The new 

Existing Stocks policy for products containing atrazine is as follows: 

The Agency has determined atrazine products (other than product containing 4% or less atrazine active 

ingredient) bearing old labels/labeling cannot be sold to end users after January 1, 2005 unless these 

products have a sticker label attached which refers to supplemental labeling. The supplemental label 

must also be given out when it is sold to an end user. The products containing 4% or less atrazine 

active ingredient are not required to follow the January 1, 2005 date for sticker labels or supplemental 

labels. However, any product with less than 4% active ingredient that is manufactured six months after 

receiving new EPA approved label must bear the revised labeling. The residential turf products; 829­

268, 7401-318, 9404-72, 11715-347, and 51036-363 are also exempt from this January 1, 2005 

requirement. However, any of these products that are manufactured after January 1, 2005 must bear 

the revised labeling. 
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

PREVENTION, PESTICIDES 

AND TOXIC SUBSTANCES 

MEMORANDUM 

SUBJECT: Errata/Addendum Sheet for Changes to the Atrazine Interim Reregistration 

Eligibility Decision. 

FROM: Anne Overstreet 

Special Review Branch 

Special Review and Reregistration Divsion 

TO: Public Docket for Atrazine 

Listed below are changes/clarifications added to the Atrazine Interim Reregistration 

Eligibility Decision (IRED) which was published in January, 2003. The regulatory decision of 

the IRED did not change as a result of these clarifications. 

1) The occupational and non-occupational mitigation areas were updated to reflect more recent

data. Because the Agency recently updated several scenarios using ORTEF data, a respirator is

no longer necessary for backpack sprayers.

2) Appendices A-H were added to the IRED. They are as follows:

- Appendix A: Atrazine Use Patterns Eligible for Reregistration 

- Appendix B: Studies Used to Support the Reregistration of Atrazine 

- Appendix C: Technical Support Documents 

- Appendix D: Citations Considered to Be Part of the Database Supporting the Interim

 Reregistration Decision (Bibliography) 

- Appendix E: Generic Data Call-In 

- Appendix F: Product Specific Data Call-In 

- Appendix G: EPA’s Batching of Atrazine Products for Meeting Acute Toxicity Data 

 Requirements For Reregistration 

- Appendix H: Atrazine Monitored Watersheds 

Appendix B was previously posted on the web. It has been subsequently been amended to 

accurately reflect the data gaps and studies used in support of reregistration. 

3) The Label Table in Section IV has been added to the IRED. In order to be eligible for 

1
reregistration, all product labels are to be amended to incorporate the risk mitigation measures 

outlined in Section IV. Table 29 has been added to the IRED and describes how language on the 

labels should be amended 

4) Clarification was made relating to the atrazine cancer assessment language. The findings of 

the 2000 SAP meeting were included. 

5) Corrections were made pertaining to the baseline attire for occupational scenarios. Baseline 

clothing typically includes: long-sleeved shirt and long pants, shoes and socks. For scenario 5 

(Table 14 of the IRED), application of liquids via groundboom, baseline assessments also 

included gloves. This clarification was made in both the text and footnotes of Table 14. 

6) In Table 15, for scenarios 10&11 (application of liquids via backpack sprayer and lowpressure handwand), the number of acres treated changed from 1 to 5 based on further 

refinements to input parameters. 

7) In Table 15 for the following scenarios: 

-12(a) - application of liquid via handgun and compressed air sprayer 

- 12(b) - WDG via lawn handgun 

- 12(c) - WSP via lawn handgun

-13 - application of granular via push-type spreader

- 7 - application of liquids via handgun 

A footnote was added which specified that these scenarios considered baseline attire plus gloves. 

8) There has been harmonization between Sections IV and V with the MOA.

9) The Atrazine Water Management Information Center (AWMIC) has been changed to the

Atrazine Water Information Center (AWIC). It has been changed in Chapters four and five of

the IRED.

2
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

PREVENTION, PESTICIDES 

AND TOXIC SUBSTANCES 

CERTIFIED MAIL 

Dear Registrants: 

This is to inform you that the Environmental Protection Agency (hereafter referred to as 

EPA or the Agency) has completed its review of the available data and public comments 

received related to the preliminary and revised risk assessments for the pesticide atrazine. The 

public comment period on the revised risk assessment phase of the reregistration process is 

closed. Based on comments received during the public comment period and additional data 

received from the registrants, the Agency revised the human health and environmental effects 

risk assessments and made them available to the public on May 6, 2002. Additionally, the 

Agency held a Technical Briefing on April 16, 2002, where the results of the revised human 

health and environmental effects risk assessments were presented to the general public. This 

Technical Briefing concluded Phase 4 of the Public Participation Pilot Process developed by the 

Tolerance Reassessment Advisory Committee (TRAC), and initiated Phase 5 of that process. 

During Phase 5, all interested parties were invited to participate and provide comments and 

suggestions on ways the Agency might mitigate the estimated risks presented in the revised risk 

assessments. This public participation and comment period commenced on May 6, 2002, and 

closed on July 5, 2002. 

Based on its review, EPA has identified risk mitigation measures that the Agency 

believes are necessary to address the human health and environmental risks associated with the 

current use of atrazine. The EPA is now publishing its interim decision on the reregistration 

eligibility of and risk management decision for the current uses of atrazine and associated human 

health and environmental risks. The reregistration eligibility and tolerance reassessment 

decisions for atrazine will be finalized once the cumulative assessment for all of the triazine 

herbicides is complete. The enclosed “Interim Reregistration Eligibility Decision for Atrazine” 

was approved on January 31, 2003, and contains the Agency’s decision on the individual 

chemical atrazine. 

The Agency is aware that several pertinent studies are being performed at this time by 

3
researchers that may reduce some of the uncertainties in understanding potential atrazine effects 

on amphibian endocrinology and reproductive and developmental responses. The Agency has 

committed to provide these studies along with other available studies, a summary of the 

available data and methodologies and various data analyses for an external scientific review by 

the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) Science Advisory Panel (SAP) 

at a public meeting which is scheduled for June, 2003. The Agency anticipates that the results 

from this SAP meeting will provide significant input to enable it publish an amendment to this 

IRED in October 2003 which will address the issue of the potential effects of atrazine on 

amphibian endocrinology and development. 

A Notice of Availability for this Interim Reregistration Eligibility Decision (interim 

RED) is being published in the Federal Register. To obtain a copy of the interim RED 

document, please contact the OPP Public Regulatory Docket (7502C), US EPA, Ariel Rios 

Building, 1200 Pennsylvania Avenue NW, Washington, DC 20460, telephone (703) 305-5805. 

Electronic copies of the interim RED and all supporting documents are available on the Internet. 

See http:www.epa.gov/pesticides. 

The interim RED is based on the updated technical information found in the atrazine 

public docket. The docket includes background information and comments on the Agency’s 

preliminary risk assessments, the Agency’s April 2002 revised risk assessments for atrazine, and 

a document summarizing the Agency’s Response to Comments. The Response to Comments 

document addresses corrections to the preliminary risk assessments submitted by chemical 

registrants and responds to comments submitted by the general public and stakeholders during 

the comment period on the risk assessment. The docket also includes comments on the revised 

risk assessment, and any risk mitigation proposals submitted during Phase 5. For atrazine, a 

proposal was submitted by Syngenta Crop Protection, Inc. (Syngenta), a technical registrant. 

Comments on mitigation or mitigation suggestions were submitted by growers, agricultural 

extension agents, environmental organizations, university scientists, and various other 

organizations. 

This document and the process used to develop it are the result of a pilot process to 

facilitate greater public involvement and participation in the reregistration and/or tolerance 

reassessment decisions for pesticides. As part of the Agency’s effort to involve the public in the 

implementation of the Food Quality Protection Act of 1996 (FQPA), the Agency is undertaking a 

special effort to maintain open public dockets on pesticides and to engage the public in the 

reregistration and tolerance reassessment processes for these chemicals. This open process 

follows the guidance developed by TRAC, a large multi-stakeholder advisory body that advised 

the Agency on implementing the new provisions of the FQPA. The reregistration and tolerance 

reassessment reviews for atrazine are following this new process. 

Please note that the atrazine risk assessment and the attached interim RED concern only 

this particular triazine. This interim RED presents the Agency’s conclusions on the dietary and 

4
residential risks posed by exposure to atrazine alone. The Agency has also concluded its 

assessment of the ecological risk, with the exception of the potential atrazine effects on 

amphibian endocrinology and reproductive and developmental responses, and worker risks 

associated with the use of atrazine. Because the FQPA directs the Agency to consider available 

information on cumulative risk from substances sharing a common mechanism of toxicity, such 

as the toxicity expressed by the triazine herbicides through a common biochemical mechanism, 

the Agency will evaluate the cumulative risk posed by the entire triazine class of chemicals after 

considering the risks for the individual triazines. The Agency is working towards completion of 

a methodology to assess cumulative risk and the individual risk assessments for each triazine are 

likely to be necessary elements of any cumulative assessment. The Agency has decided to move 

forward with individual assessments and to identify mitigation measures necessary to address 

those human health and environmental risks associated with the current uses of atrazine. The 

Agency will issue the final tolerance reassessment decision for atrazine and finalize decisions on 

reregistration eligibility once the cumulative risks for all of the triazines are considered. 

This document contains a generic and/or a product-specific Data Call-In(s) (DCI) that 

outline(s) further data requirements for this chemical. Note that a complete DCI, with all 

pertinent instructions, is being sent to registrants under a separate cover. Additionally, for 

product-specific DCIs, the first set of required responses is due 90 days from the receipt of the 

DCI letter. The second set of required responses is due eight months from the date of the DCI. 

The Agency has determined that atrazine is eligible for reregistration provided that all the 

conditions identified in this document are satisfied, including implementation of the interim risk 

mitigation measures outlined in Section IV of the document. This determination does not include 

consideration of the cumulative risk from the use of the triazines. The Agency believes that 

certain current uses of atrazine pose unreasonable adverse effects to human health and the 

environment, and that such effects can be mitigated with the risk mitigation measures identified 

in this interim RED. Accordingly, the Agency recommends that registrants implement these 

interim risk mitigation measures immediately. Section V of this interim RED describes labeling 

amendments for end-use products and data requirements necessary to implement these interim 

mitigation measures. Instructions for registrants on submitting revised labeling and the time 

frame established to do so can be found in Section VI of this document. 

Should a registrant fail to implement any of the risk mitigation measures outlined in this 

document, the Agency will undertake appropriate action to address concerns about the risks 

posed by atrazine. Where the Agency has identified any unreasonable adverse effect to human 

health or the environment, the Agency must take action to address this concern. At that time, 

any affected person(s) may challenge the Agency’s action. 

5
If you have questions on this document or the label changes necessary for reregistration, 

please contact the Chemical Review Manager, Kimberly Nesci at (703) 308-8059. For questions 

about product reregistration and/or the Product DCI that accompanies this document, please 

contact Bonnie Adler at (703) 308-8523. 

Sincerely, 

Lois A. Rossi, Director 

Special Review and 

Reregistration Division 

Attachment 

6
Interim Reregistration Eligibility Decision

for

Atrazine

Case No. 0062

TABLE OF CONTENTS

Atrazine Team ............................................................... v

Glossary of Terms and Abbreviations .......................................... vii

Executive Summary ........................................................... 1

I. Introduction ............................................................ 7

II. Chemical Overview ...................................................... 9

A. Regulatory History ................................................. 9

B. Chemical Identification ............................................. 11

C. Use Profile ........................................................ 12

D. Estimated Usage of Pesticide ........................................ 13

III. Summary of Atrazine Risk Assessments .................................... 15

A. Human Health Risk Assessment ...................................... 15

1. Dietary Risk From Food ....................................... 16

a. Toxicity and Carcinogenicity .......................... 16

1) Atrazine and the Chlorinated Metabolites .... 16

2) Hydroxyatrazine .......................... 17

b. FQPA Safety Factor ................................. 17

1) Atrazine and the Chlorinated Metabolites ..... 17

2) Hydroxyatrazine .......................... 18

c. Population Adjusted Dose ............................ 19

d. Exposure Assumptions ............................... 20

e. Food Risk Characterization ........................... 20

1) Atrazine and Its Chlorinated Metabolites ..... 21

2) Hydroxyatrazine .......................... 21

2. Dietary Risk from Drinking Water .............................. 21

a. Drinking Water Levels of Comparison (DWLOC) ....... 22

1) Community Water Systems (CWS) Using Surface

Water ................................... 23

2) Groundwater ............................. 25

3) Domestic Rural Wells ...................... 26

2. Residential Risk .............................................. 26

a. Toxicity ........................................... 27

b. Exposure Assumptions ............................... 28

c. Residential Applicator Risk ........................... 29

d. Post-Application Residential Risk ...................... 30

3. Aggregate Risk ............................................... 32

a. Acute Aggregate Exposure and Risk Estimates ........... 32

b. Intermediate-Term and Chronic Aggregate Exposure and 

i 
Risk Estimates ...................................... 33

c. Short-Term Aggregate Exposure and Risk Estimates ..... 33

1) Adult Handlers ........................... 33

2) Adult Post-Application ..................... 34

3) Child Post-Application ..................... 35

4. Occupational Risk ............................................ 36

a. Toxicity ........................................... 36

b. Occupational Exposure .............................. 38

c. Occupational Handler Risk Summary .................. 39

1) Agricultural Handler Risk .................. 39

2) Lawn Care Operator Handler Risk .......... 50

3) Post-Application Occupational Risk ......... 52

4) Epidemiology Data ........................ 52

B. Environmental Risk Assessment ...................................... 53

1. Environmental Fate and Transport .............................. 53

2. Risk to Terrestrial Organisms .................................. 56

a. Toxicity (Hazard) Assessment ......................... 57

b. Exposure and Risk - Birds and Mammals ............... 58

c. Exposure and Risk - Terrestrial Plants ................. 60

3. Risk to Aquatic Species ........................................ 61

a. Toxicity (Hazard) Assessment ......................... 61

b. Exposure and Risk .................................. 63

5. Refined Aquatic Assessment .................................... 65

a. Ponds ............................................. 69

b. Lakes and Reservoirs ................................ 69

c. Streams ........................................... 70

d. Estuaries .......................................... 70

6. Risk to Endangered Species ..................................... 71

7. Ecological Incident Reports ..................................... 72

8. Endocrine Disruption .......................................... 73

IV. Interim Risk Management and Reregistration Decision ....................... 75

A. Determination of Interim Reregistration Eligibility ...................... 75

B. Summary of Phase 5 Comments and Responses ......................... 76

C. Regulatory Position ................................................ 78

1. FQPA Assessment ............................................. 78

a. “Risk Cup” Determination ........................... 78

b. Tolerance Summary ................................. 79

3. Codex Harmonization ......................................... 84

4. Endocrine Disruptor Effects .................................... 84

5. Labels ....................................................... 85

a. Agricultural Use Exposure Reduction Measures ......... 85

1) Mixing/Loading Scenarios: ................. 86

ii 
2) Applicator and Flagger Scenarios: 

......................................... 86

b. Non-Agricultural Use Exposure Reduction Measures ..... 87

1) Non-Agricultural Products including Lawns and

Turf (not Sod Farms) ...................... 87

2) Residential ............................... 87

c. Label Harmonization ................................ 87

D. Regulatory Rationale ............................................... 89

1. Human Health Risk Mitigation .................................. 89

a. Dietary (Food) ...................................... 89

b. Dietary (Drinking Water) ............................ 89

1) Community Water Systems (CWS) ........... 89

2) Rural Drinking Water Wells ................ 92

b. Residential Risk Mitigation ........................... 93

1) Residential Handler Risk ................... 93

2) Residential Post-Application Risk ............ 93

c. Aggregate Risk Mitigation ............................ 93

1) Acute Exposure ........................... 94

2) Intermediate-Term and Chronic Exposure .... 94

3) Short-Term Aggregate Exposure ............ 94

d. Occupational Risk Mitigation ......................... 95

1) Mixing/Loading Scenarios .................. 96

2) Applicator and Flagger Scenarios ........... 96

3. Non-Agricultural Products including Lawns and Turf (not Sod Farms) 97

2. Environmental Risk Mitigation ................................. 98

3. Other Labeling ............................................... 98

a. Endangered Species Statement ........................ 99

b. Spray Drift Management ............................. 99

V. What Registrants Need to Do ............................................ 101

A. Manufacturing Use Products ....................................... 101

1. Additional Generic Data Requirements .......................... 101

2. Labeling for Manufacturing Use Products ....................... 103

B. End-Use Products ................................................. 103

1. Additional Product-Specific Data Requirements .................. 103

2. Labeling for End-Use Products ................................ 103

C. Existing Stocks ................................................... 103

D. Labeling Changes Summary Table .................................. 104

Appendix A: ATRAZINE USE PATTERNS ELIGIBLE FOR 

REREGISTRATION ......................................... 127

iii 
Appendix B: STUDIES USED TO SUPPORT THE REREGISTRATION OF

ATRAZINE ................................................. 153

Appendix C: TECHNICAL SUPPORT DOCUMENTS ........................ 169

Appendix D: CITATIONS CONSIDERED TO BE PART OF THE DATA BASE 

SUPPORTING THE INTERIM REREGISTRATION DECISION 

(BIBLIOGRAPHY) .......................................... 173

Appendix F: PRODUCT SPECIFIC DATA CALL-IN ........................ 267

Appendix G: EPA'S BATCHING OF ATRAZINE PRODUCTS FOR MEETING 

ACUTE TOXICITY DATA REQUIREMENTS FOR 

REREGISTRATION ......................................... 277

Appendix H: ATRAZINE MONITORED WATERSHEDS ..................... 287

iv 
Atrazine Team 

Office of Pesticide Programs: 

Health Effects Risk Assessment 

Gary Bangs 

Vicki Dellarco 

Catherine Eiden 

Artensie Flowers 

Linda Taylor 

Environmental Fate Risk Assessment 

Tim Bargar 

Kevin Costello 

Mary Frankenberry 

James Lin 

William Rabert 

Thomas Steeger 

Douglas Urban 

Use and Usage Analysis 

Neil Anderson 

Nicole Mosz 

Steve Smearman 

Philip Villanueva 

Virginia Werling 

Registration Support 

Philip Errico 

Edith Minor 

Jim Tompkins 

Risk Management 

Mark Hartman 

Kimberly Nesci 

v 
vi
Glossary of Terms and Abbreviations 

AE Acid Equivalent 

a.i. Active Ingredient 

AGDCI Agricultural Data Call-In 

ai Active Ingredient 

aPAD Acute Population Adjusted Dose 

AR Anticipated Residue 

ARC Anticipated Residue Contribution 

BCF Bioconcentration Factor 

CAS Chemical Abstracts Service 

CI Cation 

CNS Central Nervous System 

cPAD Chronic Population Adjusted Dose 

CSF Confidential Statement of Formula 

CFR Code of Federal Regulations 

CSFII USDA Continuing Surveys for Food Intake by Individuals 

DCI Data Call-In 

DEEM Dietary Exposure Evaluation Model 

DFR Dislodgeable Foliar Residue 

DRES Dietary Risk Evaluation System 

DWEL Drinking Water Equivalent Level (DWEL) The DWEL represents a medium 

specific (i.e., drinking water) lifetime exposure at which adverse, noncarcinogenic 

health effects are not anticipated to occur. 

DWLOC Drinking Water Level of Comparison. 

EC Emulsifiable Concentrate Formulation 

EEC Estimated Environmental Concentration. The estimated pesticide concentration 

in an environment, such as a terrestrial ecosystem. 

EP End-Use Product 

EPA U.S. Environmental Protection Agency 

FAO Food and Agriculture Organization 

FDA Food and Drug Administration 

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act 

FFDCA Federal Food, Drug, and Cosmetic Act 

FQPA Food Quality Protection Act 

FOB Functional Observation Battery 

G Granular Formulation 

GENEEC Tier I Surface Water Computer Model 

GLC Gas Liquid Chromatography 

GLN Guideline Number 

GM Geometric Mean 

GRAS Generally Recognized as Safe as Designated by FDA 

HA Health Advisory (HA). The HA values are used as informal guidance to 

vii 
municipalities and other organizations when emergency spills or contamination 

situations occur. 

HAFT Highest Average Field Trial 

HDT Highest Dose Tested 

IR Index Reservoir 

LC50 Median Lethal Concentration. A statistically derived concentration of a substance 

that can be expected to cause death in 50% of test animals. It is usually expressed 

as the weight of substance per weight or volume of water, air or feed, e.g., mg/l, 

mg/kg or ppm. 

LD50 Median Lethal Dose. A statistically derived single dose that can be expected to 

cause death in 50% of the test animals when administered by the route indicated 

(oral, dermal, inhalation). It is expressed as a weight of substance per unit weight 

of animal, e.g., mg/kg. 

LEL Lowest Effect Level 

LOC Level of Concern 

LOD Limit of Detection 

LOAEL Lowest Observed Adverse Effect Level 

MATC Maximum Acceptable Toxicant Concentration 

MCLG Maximum Contaminant Level Goal. The MCLG is used by the Agency to 

regulate contaminants in drinking water under the Safe Drinking Water Act. 

mg/kg/day Milligram Per Kilogram Per Day 

mg/L Milligrams Per Liter 

MOE Margin of Exposure 

MP Manufacturing-Use Product 

MPI Maximum Permissible Intake 

MRID Master Record Identification (number). EPA's system of recording and tracking 

studies submitted. 

NA Not Applicable 

N/A Not Applicable 

NAWQA USGS National Water Quality Assessment 

NOEC No Observable Effect Concentration 

NOEL No Observed Effect Level 

NOAEL No Observed Adverse Effect Level 

NPDES National Pollutant Discharge Elimination System 

NR Not Required 

OP Organophosphate 

OPP EPA Office of Pesticide Programs 

OPPTS EPA Office of Prevention, Pesticides and Toxic Substances 

Pa Pascal, the pressure exerted by a force of one newton acting on an area of one 

square meter. 

PAD Population Adjusted Dose 

PADI Provisional Acceptable Daily Intake 

PAG Pesticide Assessment Guideline 

PAM Pesticide Analytical Method 

viii 
PCA Percent Crop Area 

PCO Pest Control Operator 

PDP USDA Pesticide Data Program 

PHED Pesticide Handler's Exposure Data 

PHI Preharvest Interval 

ppb Parts Per Billion 

PPE Personal Protective Equipment 

ppm Parts Per Million 

PRN Pesticide Registration Notice 

PRZM/ 

EXAMS Tier II Surface Water Computer Model 

Q1* The Carcinogenic Potential of a Compound, Quantified by the EPA's Cancer Risk 

Model 

RAC Raw Agriculture Commodity 

RBC Red Blood Cell 

RED Reregistration Eligibility Decision 

REI Restricted Entry Interval 

RfD Reference Dose 

RQ Risk Quotient 

RS Registration Standard 

RUP Restricted Use Pesticide 

SAP Science Advisory Panel 

SCI-GROW Tier I Ground Water Computer Model 

SF Safety Factor 

SLC Single Layer Clothing 

SLN Special Local Need (Registrations Under Section 24(c) of FIFRA) 

TC Toxic Concentration. The concentration at which a substance produces a toxic 

effect. 

TD Toxic Dose. The dose at which a substance produces a toxic effect. 

TEP Typical End-Use Product 

TGAI Technical Grade Active Ingredient 

TLC Thin Layer Chromatography 

TMRC Theoretical Maximum Residue Contribution 

torr A unit of pressure needed to support a column of mercury 1 mm high under 

standard conditions. 

TRR Total Radioactive Residue 

UF Uncertainty Factor 

Fg/g Micrograms Per Gram 

Fg/L Micrograms Per Liter 

USDA United States Department of Agriculture 

USGS United States Geological Survey 

UV Ultraviolet 

WHO World Health Organization 

WP Wettable Powder 

ix 
WPS Worker Protection Standard 

x 
Executive Summary 

EPA has completed its review of public comments concerning the revised atrazine risk 

assessments and is issuing its interim risk management decision for atrazine. The revised risk 

assessments are based on the Agency’s review of available data on the currently registered uses 

of atrazine and public comments received during the reregistration process. The Agency invited 

stakeholders to provide proposals, ideas or suggestions on appropriate mitigation measures 

before the Agency issued its risk mitigation decision for atrazine. After considering the risks 

identified, public comments, and mitigation options proposed by several entities, the Agency 

developed its interim risk management decision for atrazine. This decision is discussed fully in 

this document and in a January 31, 2003, Memorandum of Agreement between the Agency and 

the primary technical registrant, Syngenta Crop Protection, Inc. The Agency expects the atrazine 

technical registrants to agree to adopt the risk management measures presented in the IRED and 

in the MOA. Neither the risk assessments nor the interim risk management measures include 

consideration of cumulative risks posed by all of the triazines and amphibian risk issues. 

Atrazine is a triazine herbicide currently registered for use against broadleaf and some 

grassy weeds. Atrazine is currently registered for use on corn (field and sweet); guavas; 

macadamia nuts; sorghum; sugarcane; range grasses for the establishment of permanent grass 

cover on rangelands and pastures under USDA’s Conservation Reserve Program (CRP) in OK, 

NE, TX, and OR; wheat (where application is to wheat stubble on fallow land following wheat 

harvests; wheat is not the target crop); conifer forests; Christmas tree farms; sod farms; golf 

courses and residential lawns (Southern turfgrasses). Given the specific nature of the lawn uses, 

much of atrazine’s use on lawns is confined to Florida and the Southeast. Atrazine degrades into 

hydroxy compounds and chlorotriazine degradates. Atrazine was first registered in 1958 as an 

herbicide. Use data from 1990 to 1997 indicate that approximately 76.5 million pounds of 

atrazine active ingredient are used domestically each year. 

The Food Quality Protection Act of 1996 (FQPA) requires that, when considering 

whether to establish, modify, or revoke a tolerance, the Agency consider “available information” 

concerning the cumulative effects of a particular pesticide’s residues and other substances that 

have a common mechanism of toxicity with other pesticides. The Agency has classified the 

triazine herbicides (atrazine, simazine, and propazine) and their common chlorinated degradates 

as having a common mechanism of toxicity. The Agency has not yet completed its cumulative 

risk assessment for the triazine class, but the cumulative risks of these chemicals will be 

considered in the future. At that time, the Agency’s final tolerance reassessment decision for 

atrazine and the other triazines will be issued. The Agency may need to pursue further risk 

mitigation for atrazine to address any risks identified in the cumulative assessment for the 

triazines. 

Overall Risk Summary 

1
The Agency’s human health risk and ecological risk assessments for atrazine indicate 

risks of concern. Intermediate-term (seasonal) dietary risk from drinking water exceeds the 

Agency’s level of concern (>100% cPAD) at the 99.9th exposure percentile for infants, children 

1-6 years of age, and adults in 34 community water systems (CWS) primarily in the Midwest. 

Acute dietary drinking water risks, and acute and chronic dietary food risks (alone) are below the 

Agency’s level of concern for the U.S. population and all population subgroups. 

Further, there are some concerns for workers who mix, load and apply atrazine to 

agricultural and turf sites and for homeowners who apply atrazine products to home lawns. In 

addition, there are risks of concern for adults and children exposed to atrazine treated lawns after 

applications. 

For ecological effects, the Agency has conducted a screening level assessment for 

terrestrial impacts and a refined exposure assessment for aquatic impacts of atrazine use. These 

assessments indicate that atrazine is likely to result in community- and population-level risk at 

10 to 20 ppb. The ecological assessment does not address the potential for effects on amphibians 

endocrinology and reproductive and developmental responses. The Agency will consider 

amphibian risk after the Agency obtains further data and will address any risks identified in a 

revision to the IRED to be published by October 31, 2003. 

To mitigate risks of concern posed by the uses of atrazine, the Agency considered the 

mitigation proposal submitted by the technical registrants, as well as comments and mitigation 

ideas from other interested parties, and has decided on a number of label amendments to address 

the dietary (drinking water), worker, and residential concerns. In addition, to further address 

drinking water concerns and to address ecological concerns, the Agency and the technical 

registrants have agreed to a performance standard for atrazine that must be met in community 

water systems, prohibition of use in watersheds if the standard is not met, and monitoring data 

requirements as described in the Memorandum of Agreement. Results of the risk assessments, 

the necessary label amendments to mitigate those risks, and information on the Agreement 

between the Agency and the technical registrants are presented in this IRED. 

Dietary Risk (Food) 

Acute risk estimates for food and drinking water and chronic food risk estimates do not 

exceed the Agency’s level of concern; therefore, mitigation measures are not needed to address 

acute dietary risks or chronic food risk estimates. 

Dietary Risk (Drinking Water) 

Intermediate-term (seasonal) drinking water risk estimates do exceed the Agency’s level 

of concern in 34 CWS primarily in the Midwest. The registrant has added three CWS to these 34 

to make a total of 37 CWS that are of concern. To mitigate these risks, the Agency has 

determined that a performance standard that must be met in these CWS and prohibiting use in 

the watershed if the performance standard is not met is necessary to avoid unreasonable adverse 

2
effects. In addition, the Agency is requiring extensive monitoring data on these CWS and other 

CWS that are in atrazine use areas. 

To confirm that risks from atrazine in rural wells is not a concern, the Agency is 

requiring monitoring data for atrazine levels in rural wells in atrazine use areas. 

Residential Risk 

Residential and turf use results in risks of concern for children reentering treated atrazine 

turf and for homeowners applying product to turf using a bellygrinder. 

Restrict the application of granular lawn products when using hand-held devices (e.g. belly 

grinder) to spot applications only. 

C Prohibit applications of granular lawn products by hand 

C Reduce the maximum single application rate for liquid formulations on residential lawns 

and turf to 1 lb ai/A from 2 lb ai/A (liquid products containing >4% ai are restricted use) 

C Require that granular lawn products be watered in 

Occupational Risk 

Occupational exposure to atrazine is of concern to the Agency. For agricultural and turf 

lawn care operator uses of atrazine, several mixer/loader/applicator risk scenarios currently 

exceed the Agency’s level of concern at baseline PPE or label PPE. The Agency has determined 

that a number of measures are needed to mitigate these risks, as follows: 

Agricultural Uses 

1) Mixing/Loading Scenarios: 

Liquids: 

C require closed systems for mixing/loading to support aerial applications at 

greater than 3 lb ai/A 

C all mixers/loaders (including using engineering controls) must wear longsleeve shirt, long pants, shoes, socks, chemical-resistant gloves and 

chemical resistant apron 

Wettable Powders: 

C require water-soluble packaging for all WP formulations 

C all mixers/loaders must wear long-sleeve shirt, long pants, shoes, socks, 

chemical-resistant gloves and chemical resistant apron 

Dry Flowables: 

C water-soluble packaging optional 

C if in water-soluble packaging, all mixers/loaders must wear long-sleeve 

shirt, long pants, shoes, socks, chemical-resistant gloves and chemical 

resistant apron 

C if not in water-soluble packaging, mixers/loaders must wear coveralls over 

3
long-sleeve shirt and long pants, chemical-resistant gloves, chemicalresistant footwear, and chemical-resistant apron plus a NIOSH-approved 

dust/mist filtering respirator with any N, R, P, or HE filter. 

C if not in water-soluble packaging, aerial application is prohibited.

Granular Products:

C Loaders must wear long-sleeve shirt, long pants, shoes, and socks.

2) Applicator and Flagger Scenarios: 

C Pilots must use enclosed cockpits (40 CFR 170.240(d)(6)) for aerial applications. 

C Human flaggers supporting aerial applications must used enclosed cabs (40 CFR 

170.240(d)(5)). 

C Applicators applying sprays with motorized ground equipment (i.e., groundboom 

or rights-of-way sprayers) must wear long-sleeve shirt, long pants, shoes, socks, 

and chemical-resistant gloves. 

C Applicators applying granular products or impregnated fertilizer must wear longsleeve shirt, long pants, shoes, and socks. 

C Restrict the impregnation of bulk fertilizer to commercial facilities (prohibit onfarm impregnation) 

C Restrict the impregnation of dry bulk fertilizer to 500 tons per day for no more 

than 30 days per calender year per facility 

C Reduce the maximum application rate for handlers applying liquids with rightsof-way sprayers to 1.0 lb ai/A 

C Reduce the maximum application rate for liquids for chemical follow to 2.25 lb 

ai/A 

C Require a 60-day PHI for field corn forage uses 

C Require a 45-day PHI for sweet corn forage uses 

C Require a 60-day PHI for preemergent uses and a 45-day PHI for postemergent 

sorghum forage uses 

Non-Agricultural Products including Lawns and Turf (not Sod Farms) 

C Require that all wettable powder products be packaged in water soluble bags. 

C Granular formulations: loaders, applicators, and other handlers must wear longsleeve shirt, long pants, shoes, and socks. 

C Liquid, wettable powder, dry flowable (water-dispersible granule) formulations: 

- applicators using spray equipment mounted on their backs must wear coveralls 

worn over long sleeved shirt and long pants, chemical-resistant gloves and 

chemical-resistant footwear plus socks.

 - all other mixers, loaders, applicators, and other handlers must wear long-sleeved 

shirt and long pants, shoes and socks, and chemical resistant gloves. 

C Reduce the maximum single application rate for liquid formulations on residential lawns 

and turf to 1 lb ai/A from 2 lb ai/A (liquid products containing >4% ai are restricted use) 

C Require that granular lawn products be watered in 

4
The Agency does not have risks of concern for workers reentering treated fields; 

therefore, no mitigation is needed. 

Ecological Risk 

Ecological risks are also of concern to the Agency. The environmental risk assessment 

suggests that exposure to atrazine could result in community-level and population-level effects in 

aquatic communities at concentrations of 10-20 ppb atrazine. 

To address these risks, the Agency has determined that an ecological assessment process 

to identify waterbodies at risk and monitor these waterbodies for atrazine concentrations. In 

addition, it may be necessary to undertake mitigation in these vulnerable ecosystems. The 

specifics of this ecological program will be negotiated with the technical registrants and agreed 

to by April 30, 2003.

 The ecological assessment does not address the potential for effects on amphibian 

endocrinology and reproductive and developmental responses. The Agency will consider 

amphibian risk after the Agency obtains further data on this issue. Any risks identified will be 

addressed by the Agency in a revision to the IRED to be published by October 31, 2003. 

Conclusions 

The Agency is issuing this interim Reregistration Eligibility Decision (IRED) for 

atrazine, as announced in a Notice of Availability published in the Federal Register. This IRED 

includes guidance and time frames for implementing label changes for products containing 

atrazine. Note that the Agency has shortened the time period for implementation of risk 

mitigation measures outlined in this document and to establish monitoring programs so that the 

risks identified herein are addressed as quickly as possible. There is a 60-day comment period 

on this document. With the mitigation measures detailed in this document, the Agency has 

determined that, until the cumulative risks from all the triazines has been considered, most of the 

currently registered uses of atrazine may continue. Neither the tolerance reassessment nor the 

reregistration eligibility decision for atrazine can be considered final until the cumulative risk for 

all triazines is considered. 

5
6
I. Introduction 

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was amended in 1988 

to accelerate the reregistration of products containing active ingredients originally registered 

prior to November 1, 1984. The amended Act calls for the development and submission of data 

to support the reregistration of an active ingredient, as well as a review of all submitted data by 

the U.S. Environmental Protection Agency (EPA or “the Agency”). Reregistration involves a 

thorough review of the scientific database supporting a pesticide’s registration. The purpose of 

the Agency’s review is to reassess the potential hazards and benefits arising from the currently 

registered uses of the pesticide; to determine if there is a need for additional data on benefits, 

health and environmental effects; and to determine whether the pesticide meets the “no 

unreasonable adverse effects” criteria of FIFRA. 

On August 3, 1996, the Food Quality Protection Act of 1996 (FQPA) was signed into 

law. This Act amends the Federal Food, Drug and Cosmetics Act (FFDCA) to require 

reassessment of all existing tolerances. The Agency had decided that, for those chemicals that 

have tolerances and are undergoing reregistration, the tolerance reassessment will be initiated 

through this reregistration process. It also requires that by 2006, EPA must review all tolerances 

in effect as of August 2, 1996 (the day before FQPA was enacted). FQPA also amends the 

FFDCA to require a safety finding in tolerance reassessment based on several factors, including 

an assessment of cumulative effects of chemicals with a common mechanism of toxicity. 

Atrazine belongs to a group of systemic herbicides called triazines that share a common 

mechanism of toxicity. Agency is continuing its reregistration program while it resolves the 

remaining issues associated with the implementation of FQPA. 

This document presents the Agency’s revised human health and ecological risk 

assessments; its progress toward tolerance reassessment; and the interim decision on the 

reregistration eligibility of atrazine. It is intended to be only the first phase in the reregistration 

process for atrazine. The Agency will eventually proceed with its assessment of the cumulative 

risk of the triazine pesticides and issue a final reregistration eligibility decision for atrazine.

 The implementation of FQPA has required the Agency to revisit some of its existing 

views relating to the determination and regulation of dietary risk, and has also raised a number of 

new issues that need to be addressed. These issues were refined and developed through 

collaboration between the Agency and the Tolerance Reassessment Advisory Committee 

(TRAC), a committee that was composed of representatives from industry, environmental 

groups, and other interested parties. 

This interim Reregistration Eligibility Decision document consists of six sections. 

Section I contains the regulatory framework for reregistration/tolerance reassessment. Section II 

provides a profile of the use and usage of the chemical. Section III gives an overview of the 

revised human health and environmental effects risk assessments resulting from public 

comments and other information. Section IV presents the Agency's interim decision on 

reregistration eligibility and risk management decisions. Section V summarizes the label 

7
changes necessary to implement the risk mitigation measures outlined in Section IV. Section VI 

provides information on how to access related documents. Finally, the Appendices list Data 

Call-In (DCI) information. The revised risk assessments and related addenda are not included in 

this document, but are available on the Agency's web page: 

“www.epa.gov/pesticides/reregistration,” and in the Public Docket. 

8
II. Chemical Overview 

A. Regulatory History 

Atrazine was first registered in 1958 as an herbicide. On November 10, 1983, a 

Registration Standard for atrazine was issued. This document noted the Agency’s concern about 

the dietary carcinogenic risk from ground and surface water contamination. The Registration 

Standard also required the submission of generic and product-specific data to support the 

continued registration of atrazine products. Since the Registration Standard was issued in 1983, 

there have been a total of 4 DCIs issued (September 1990, September 1992, March 1995, 

October 1995). 

In 1988, EPA issued a preliminary notification of the Agency’s intention to initiate 

Special Review under FIFRA based on concerns regarding the carcinogenic potential of atrazine 

and possible risks resulting from exposure to atrazine in the diet from treated food and drinking 

water. 

In the early 1990s, atrazine's occurrence in the environment prompted the Environmental 

Protection Agency’s Office of Water (OW) to regulate atrazine under the Safe Drinking Water 

Act (SDWA). In 1991 OW established a Maximum Contaminant Level (MCL) of 3 parts per 

billion (ppb) for atrazine. Under the SDWA, atrazine has been subject to compliance 

monitoring. OW has also established a one-day Health Advisory Level (HAL) for atrazine of 

100 ppb. 

In the early 1990s, the registrant voluntarily instituted several risk reduction measures to 

address concerns raised about surface water and groundwater contamination by atrazine. In 

1990, the following measures were undertaken by the registrant to address groundwater exposure 

concerns: 

C Reduction of the application rate for corn and sorghum to 3.0 lbs ai/acre from 4.0 

lbs ai/acre. 

C Reduction of the maximum rate for non-cropland and total vegetation control to 

10 lbs ai/acre from 40 lbs ai/acre. 

C Require that postemergence applications to corn and sorghum be made before 

they reach 12 inches in height. 

C Deletion of rangeland, proso millet, and pineapple uses. 

C Prohibition of chemigation (applying atrazine through irrigation systems). 

C Institution of a well-head protection plan requiring 50 foot setbacks around all 

wells for mixing, loading, or applying atrazine-containing products. 

• Institution of construction requirements for bulk storage facilities to prevent point 

source contamination from spills 

• Classification of all atrazine-containing products (except for the lawn care, turf, 

and conifer uses) as Restricted Use Pesticides (RUPs). 

9
In 1992, the following additional measures were undertaken to address concerns about 

atrazine contamination of surface water sources: 

• Further reduction of the total seasonal application rates for corn and sorghum to 

2.5 lbs ai/acre per year. This rate includes a 1.5 lbs ai/acre per year pre-emergence 

use and a 1.0 lbs ai/acre per year post-emergence use. 

• Deletion of all uses for total vegetation control in non-cropland. 

• Expansion of restricted use criteria to include surface water concerns. 

• Expansion of the setback requirements, including: a 50 foot setback around 

surface water sources when workers are mixing and loading atrazine-containing 

products; a 66 foot application (ground and aerial) setback from points of entry 

where field surface water runoff enters surface water sources; and, a 200 foot 

application setback around lakes and reservoirs. 

In November 1994, EPA initiated a Special Review for the triazine pesticides (atrazine, 

simazine and cyanazine; 59 FR 60412) based on cancer risk concerns for people potentially 

exposed to atrazine through consumption of food and drinking water, and lawn treatments. The 

basis for the Special Review also included cancer risk concerns for workers exposed to atrazine 

in various agricultural settings and application scenarios. At the time that the Special Review 

was initiated, atrazine and the other triazines were classified as Group C carcinogens (possible 

human carcinogens). 

Further labeled use restrictions in 1996 reduced environmental exposure from tileterraced fields containing standpipes, as follows: 

• Restrictions against application within 66 feet of standpipes. 

• A requirement that applications be incorporated to a depth of 2 to 3 inches. 

• Restrictions against application to no-till fields unless practicing high crop 

residue management. 

In August 2002, the Agency and NRDC jointly agreed to request that the court extend the 

deadline for the IRED to January 31, 2003 (Consent Decree (as amended) entered in Natural 

Resources Defense Council v. Whitman, Case Number C -99-3701 CAL, N. D. California 

(2002)). The new schedule includes the completion of an IRED by January 31, 2003 (this 

document), and a revised IRED by October 31, 2003, to consider a number of additional new 

studies on potential amphibian risk. The Agency also agreed to bring to the FIFRA Scientific 

Advisory Panel issues regarding amphibian effects and carcinogenicity. 

10
B. Chemical Identification 

• Chemical Structure: 

• Common name: Atrazine 

• Chemical name: 6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4­

diamine 

• Chemical family: Triazines 

• Case number: 0062 

• CAS registry number: 1912-24-9 

• OPP chemical code: 080803 

• Empirical formula: C8H14ClN5 

• Molecular weight: 215.7 

• Vapor Pressure: 40 uPa at 20 EC 

• Technical registrants: Agan Chemical Manufacturing, LTD. 

Dow AgroSciences 

Drexel Chemical Company 

Oxon Italia S.P.A. 

Platte Chemical Company Inc. 

Syngenta Crop Protection Inc. 

Atrazine is a white crystalline solid with a melting point of 172-175E C, density of 0.35 

g/mL, octanol/water partition coefficient (log Pow) of 2.7645, and vapor pressure of 40 FPa at 

20E C. Atrazine is moderately soluble in water (33 ppm at 25E C), and is soluble in octanol 

(0.82 g/100 mL), ether (0.86 g/100 mL), methanol (1.4 g/100 mL), ethyl acetate (2.5 g/100 mL), 

and chloroform (7.8 g/100 mL) at 20E C. Atrazine has four hydroxyatrazine compounds and 

three chlorinated atrazine compounds as metabolites. The three chlorinated metabolites are 

desethylated atrazine, desisopropyl atrazine, and diaminochlorotriazine (DACT). 

C. Use Profile 

11
Atrazine is a systemic triazine herbicide registered for the control of broadleaf weeds and 

some grassy weeds. Currently, atrazine is one of the two most widely used agricultural 

pesticides in the United States. An estimated average of approximately 64 to 76 million pounds 

of active ingredient are applied per year. Annually, 75% of all field corn, 58.5% of all sorghum, 

and 76% of all sugarcane grown are treated with atrazine. Most of atrazine applied to corn and 

sorghum is applied pre-emergence. The following information is based on the currently 

registered uses of atrazine that were originally being supported for reregistration. Appendix A at 

the end of this document presents a summary of eligible uses and revised use conditions. 

Type of Pesticide: Triazine Herbicide 

Summary of Use Sites: 

Food: Atrazine is used on corn (field and sweet), guavas, macadamia nuts, 

sorghum, sugarcane, range grasses under USDA’s Conservation Reserve Program 

(CRP), and wheat (where application is to wheat stubble on fallow land following 

wheat harvests; wheat is not the target crop) 

Other Agricultural Sites: Atrazine is also used in conifer forests, on Christmas 

tree farms and on sod farms. 

Residential: Atrazine is used on golf courses and residential lawns. Given the 

specific nature of the lawn uses, much of atrazine’s use on lawns is confined to 

Florida and the Southeast. 

Other Sites: Atrazine in used on range grasses for the establishment of permanent 

grass cover on rangelands and pastures under the Conservation Reserve Program 

(CRP) in four states: OK, NE, TX, and OR. 

Public Health: None 

Target Pests: Broadleaf and some grassy weeds. 

Formulation Types Registered: 

Formulated as a flowable concentrate, a water dispersable granular (dry 

flowable), a ready-to-use product, and a granular. 

Method and Rates of Application: 

Equipment: Atrazine may be applied by groundboom sprayer, aircraft, 

tractor-drawn spreader, rights-of-way sprayer, low pressure handwand, 

backpack sprayer, lawn handgun, push-type spreader, and bellygrinder. 

12
Rates: Maximum application rates range from 0.4 lb ai/A or lb ai/gal to 

4.0 lb ai/A or lb ai/gal (conifer forests, sugarcane, Christmas tree farms, 

sod farms (FL), Bermuda grass highway rights-of-way). The number of 

maximum allowable applications ranges between 1 and 4 per season or 

year, when specified. 

Timing: 

Sugarcane: Applications to sugarcane are usually at planting (fall), in the spring 

after emergence, and an additional post-emergence application (often at layby 

(canopy closure)). However, these later applications are only used if pest 

pressure dictates need. Also, ratoon crops may face heavier weed pressure, and 

therefore additional applications are more likely during ratoon crops. 

Corn: Applications to corn are most often pre-emergence (mid-April through 

mid-May in the major corn growing areas). Post-emergence applications are most 

likely to occur up to the end of June, until corn reaches 12" in height. There will 

be some variability in timing based on geographical regions. 

Sorghum: Applications to corn are most often pre-emergence (mid-June to midJuly in the major sorghum growing areas). Post-emergence applications are most 

likely to occur up to the end of August. There will be some variability in timing 

based on geographical regions. 

Use Classification: Most atrazine products are restricted use pesticides. 

D. Estimated Usage of Pesticide 

This section summarizes the best estimates of available pesticide usage information for 

atrazine from 1990 to 1997. A full listing of all uses of atrazine, with the corresponding use and 

usage data for each site, has been completed and is in the January 10, 2001 “Quantitative Usage 

Analysis for Atrazine” document available in the public docket and on the internet. The data, 

reported on an aggregate and site basis, reflect annual fluctuations in use patterns as well as the 

variability in using data from various information sources. 

Estimates for total annual domestic use of atrazine averages approximately 76.5 million 

pounds of active ingredient. Crops with the highest weighted average percent crop treated are 

corn (75%), sugarcane (76%), sorghum (58.5%), sweet corn (processed) (58%) and sweet corn 

(fresh) (49%). In terms of pounds applied, corn (83%), sorghum (10%), and sugarcane (3%) 

account for the greatest use. Less than 2% of atrazine is believed to be applied in forestry, turf 

or other non-agricultural uses. 

Table 1. Atrazine Estimated Usage for Representative Sites 

13
Crop 

Pounds Active 

Ingredient Applied 

(000) (Wt. Avg.)1 

Estimated 

Maximum % 

Crop Treated 

Weighted Average 

Percent Crop 

Treated 

Food Crops 

Sweet Corn, Fresh 160 59.9 49.5 

Sweet Corn, Processed 250 64.6 58.2 

Sorghum 7,790 73.7 58.5 

Corn 63,800 84.0 75.0 

Winter Wheat 300 1.1 0.6 

Sugar Cane 2550 95 76.0 

Non-Food Crops 

Hay 150 0.7 0.4 

Pasture 46 0.1 0.0 

Summer Fallow 8 0.1 0.1 

Woody Ornamentals 140 na na 

Forestry 48 na na 

Turf - Lawn Care Operators 600 na na 

Sod 160 na na 

Golf Courses 78 na na 

1 Weighted Average is based on data for 1990-1997; the most recent years and more reliable data are weighted more 

heavily. Based on USDA/NASS and EPA proprietary data. 

14
III. Summary of Atrazine Risk Assessments 

The following is a summary of EPA’s revised human health and ecological risk findings 

and conclusions for the triazine herbicide atrazine. These findings and conclusions are fully 

presented in the following documents, available on EPA’s web page at www.epa.gov/pesticides 

and in the public docket: 

• Reregistration Eligibility Science Chapter for Atrazine - Environmental Fate and 

Effects Chapter (April 22, 2002); 

• Atrazine: HED’s Revised Human Health Risk Assessment for the Reregistration 

Eligibility Decision (April 16, 2002); 

• Addendum and corrections to Occupational and Residential Exposure Chapter for 

Atrazine (May 23, 2002); and 

• Atrazine: Addendum to Revised Human Health Risk Assessment for the 

Reregistration Eligibility Decision (RED) (January 31, 2003). 

These risk assessments for atrazine were presented at a Technical Briefing held on April 

16, 2002, and followed by an opportunity for public comment on risk management. The risk 

assessments presented here form the basis of the Agency’s risk management decision for atrazine 

only; the Agency must consider a cumulative assessment of the risks of all triazine pesticides 

before any final decisions can be made. 

A. Human Health Risk Assessment 

EPA issued its preliminary human health risk assessment for atrazine and its metabolites 

on February 14, 2001 (Phase 3 of the TRAC process). In response to comments and studies 

submitted during Phase 3, the risk assessment was updated and refined, and released on May 6, 

2002. In addition, any new Agency policies were incorporated as appropriate. Major revisions 

to the human health risk assessment are listed below: 

• Revisions to the occupational and residential risk assessments to incorporate more 

recent data and information received in the response to comments. 

• Revisions to the dietary drinking water risk assessment to include additional 

monitoring data received from the registrant. 

• A decision not to require tolerances for hydroxyatrazine. 

Exposure scenarios considered in the human health assessment are acute, intermediateterm, and chronic dietary exposure through food plus drinking water; short-term residential 

exposures from residential applications of atrazine; acute, chronic, and short-term aggregate 

exposure from all sources (food, drinking water, and residential); and short and intermediateterm occupational exposures. 

In the risk assessments presented in this document, the toxicity of atrazine and its 

chlorinated metabolites are considered to be equivalent; therefore, the risks associated with 

15
exposure to atrazine and its chlorinated metabolites are presented together. The toxicity of the 

metabolite hydroxyatrazine is considered to be independent of the effects of atrazine; thus, the 

risks from exposure to hydroxyatrazine are presented independently. 

1. Dietary Risk From Food 

a. Toxicity and Carcinogenicity 

1) Atrazine and the Chlorinated Metabolites 

The atrazine toxicity database is extensive. The Agency has reviewed these toxicity 

studies and has a high degree of confidence in the scientific quality of the toxicity studies 

conducted with atrazine. Special studies examining the toxicology of atrazine have been 

performed by the registrant in addition to the required guideline studies. Additionally, EPA's 

National Health and Environmental Effects Laboratory (NHEERL) has performed studies 

investigating atrazine's neuroendocrine mode of action and related reproductive and 

developmental effects. 

For the purposes of this risk assessment, the toxicity of atrazine’s chlorotriazine 

metabolites is considered to be equivalent to that of parent atrazine and exposure to those 

metabolites may occur. Therefore, the chlorotriazine metabolites are included in the atrazine 

human health risk assessment. 

In accordance with the 1999 Interim Guidelines for Carcinogen Risk Assessment, EPA’s 

Cancer Assessment Review Committee (CARC) classified atrazine as “not likely to be 

carcinogenic to humans”. As summarized by the FIFRA Scientific Panel (SAP), “there are 

considerable differences between hypothalamic-pituitary-ovarian function in rats and humans, 

and the effects of aging on the function of the axis also is quite dissimilar. Therefore, it is 

unlikely that the mechanism by which atrazine induces mammary gland tumors in female SD rats 

could be operational in humans. Nevertheless, it is not unreasonable to expect that atrazine 

might cause adverse effects on hypothalamic-pituitary function in humans” (SAP, 2000). 

Although the cancer mode of action may not be operative in humans, the SAP further to state 

that the same endocrine perturbations that induce tumors also appear to play a role in at least 

some reproductive developmental effects (not associated with reproductive aging) which may be 

relevant to humans. The Agency also concluded that the cancer mode of action is not relevant to 

humans. Consequently, a quantitative cancer risk assessment was not conducted for atrazine. 

However, EPA agreed in the August 2002 amendment to the Consent Decree in NRDC v. 

Whitman to present to the SAP data concerning atrazine exposure and prostrate or other cancers 

in humans that had been received by EPA after the May 2002 risk assessment but prior to 

February 28, 2003. Any risks identified will be addressed in the revised Atrazine IRED to be 

issued by October 31, 2003. 

As indicated above, the cascade of events triggered by atrazine leading to mammary 

gland tumors in female SD rats are not expected to occur in humans given the species difference 

16
in reproductive aging. However, the potential for disruption of the hypothalamic pituitary axis 

and consequent attenuation of the LH surge leading to other health consequences not associated 

with reproductive aging (e.g., delay in pubertal development) can not be dismissed. Thus, EPA 

has determined that the triazine pesticides (with a common mechanism group of atrazine, 

propazine, simazine and their chlorometabolites) have common mechanism of suppression of LH 

surge and consequent developmental and reproductive effects. It is expected that EPA will 

complete a preliminary cumulative risk assessment in the winter of 2005; this is contingent on 

completion of the IREDs for the individual chemicals. 

2) Hydroxyatrazine 

Atrazine is metabolized to hydroxyatrazine by plants and bacteria. Animals do not 

metabolize atrazine to hydroxyatrazine; however, they may receive hydroxyatrazine in their diets 

through forages and fodders. 

A limited toxicology database for hydroxyatrazine compounds is available. 

Hydroxyatrazine appears to be less acutely toxic than the parent atrazine. The only effects seen 

in any of the submitted studies that may be attributable to a single dose were developmental 

alterations in the developmental rat study. The developmental alterations seen in this study were 

seen only at the high dose, were few in number, and were deemed to be not of toxicological 

significance. Thus, the Agency did not select an acute endpoint for hydroxyatrazine, and 

concludes that no toxicologically significant endpoint to represent a single exposure can be 

found in the toxicology database for hydroxyatrazine. Hydroxyatrazine has not been classified 

as to its carcinogenic potential by the Agency. 

Further details on the toxicity of atrazine and its chlorinated and hydroxy metabolites can 

be found in the April 16, 2002, Revised Human Health Risk Assessment; the January 31, 2002, 

Addendum to the Revised Human Health Risk Assessment; and all supporting documents. An 

overview of the studies and safety factors used for the dietary risk assessment is outlined in 

Table 2. 

b. FQPA Safety Factor 

The FQPA safety factor is intended to provide up to an additional 10-fold safety factor 

(10X) to account for potential pre- and post-natal toxicity and the completeness of the data with 

respect to exposure and toxicity to infants and children. 

1) Atrazine and the Chlorinated Metabolites 

The FQPA Safety Factor of 10x was retained for atrazine and its chlorinated metabolites 

to protect the safety of infants and children in assessing risk from dietary (food and drinking 

water) exposures. 

The Agency concluded that, as to dietary risk, the default 10x FQPA safety factor is 

17
required because of the absence of reliable evidence showing that a different safety factor would 

be protective of infants and children. The principal grounds for this conclusion are: 

• residual concerns for the effects of the neuroendocrine mode of action described for 

atrazine on the development of the young. These concerns could not be accounted for in 

the determination of toxicity endpoints and traditional uncertainty factors to be used in 

risk assessment; and, 

• residual concerns with regard to the drinking water exposure assessment. The various 

water monitoring data sources that exist for atrazine and its chlorinated metabolites 

indicate that exposure via drinking water sources is high in some of the systems that have 

been monitored. In addition, widespread low levels are commonly detected. Limitations 

in the extent, frequency, and compounds tested for in the monitoring data raise 

significant uncertainties regarding the level of exposure to atrazine and its metabolites. 

The 10X FQPA safety factor is being applied across all aggregate risk assessments based 

on estimated dietary exposures for all populations considered in these risk assessments. 

For residential exposures, the FQPA safety factor was reduced to 3x. This is considered 

adequate to protect the safety of infants and children in assessing residential exposure and risks 

because the exposure concerns for drinking water included in the 10x FQPA safety factor for 

dietary exposure do not apply to residential exposure scenarios, although the concerns for the 

effect of the neuroendocrine mode of action on the development of the young remain. The 

assumptions inherent to the Agency’s residential risk estimates based on screening-level 

procedures are conservative and protective. The 3x FQPA safety factor is being applied across 

all aggregate risk assessments based on estimated residential exposures for all populations 

considered in these risk assessments. 

2) Hydroxyatrazine 

The FQPA Safety Factor of 10x was removed for atrazine’s hydroxymetabolites for the 

following reasons: 

• There was no evidence of increased susceptibility in the prenatal developmental toxicity 

study in rats with hydroxyatrazine; 

• There is no evidence of neurotoxicity from the submitted toxicity studies; 

• The neuroendocrine effects described for atrazine are postulated to be part of a cancer 

mode of action for atrazine. Because hydroxyatrazine is non-carcinogenic, the current 

belief is that the neuroendocrine effects described for atrazine are not occurring following 

hydroxyatrazine exposure; 

• The dietary and non-dietary exposure assessments do not underestimate the potential 

18
exposures for infants and children; and 

• The drinking water exposure concerns expressed for atrazine and the chlorinated 

metabolites do not apply to hydroxyatrazine, given its dissimilar toxicological profile and 

environmental fate properties that indicate that hydroxyatrazine is less mobile in 

soil/water systems. 

c. Population Adjusted Dose 

The population adjusted dose (or PAD) is a term that characterizes the dietary risk of a 

chemical. The PAD reflects the Reference Dose (RfD), either acute or chronic, that has been 

adjusted to account for the FQPA safety factor (i.e., RfD/FQPA safety factor). The RfD is 

calculated by taking the no observed adverse effect level (NOAEL) from an appropriate study 

and dividing it by an uncertainty factor (i.e., NOAEL/UF). Acute and chronic PADs are 

equivalent to the acute and chronic RfDs divided by 10, respectively. A risk estimate that is less 

than 100% of the acute PAD (aPAD) or chronic PAD (cPAD) does not exceed the Agency’s 

level of concern. In the case of atrazine, the FQPA safety factor of 10x was retained for dietary 

exposures; therefore, the RfD is ten times greater than the PAD. The PADs are presented in 

Tables 2 and 3 below for atrazine and hydroxyatrazine, respectively. 

Table 2. Summary of Toxicological Endpoints and Other Factors Used in the Dietary

Risk Assessment of Atrazine and Its Chlorinated Metabolites

Exposure 

Scenario 

Dose 

(mg/kg/day) UF FQPA SF Endpoint Study 

Acute 

Dietary 

(females 13 

to 50 yrs old) 

NOAEL= 10 

LOAEL = 70 100 10 

Delayed ossification of certain 

cranial bones in fetuses, decreased 

body weight gain in adult 

Developmental 

toxicity study in rat 

& rabbit (weight of 

evidence from four 

studies) 

Acute RfD = 0.1 mg/kg/day 

Acute PAD = 0.01 mg/kg/day 

Intermediate 

and 

Chronic 

NOAEL = 1.8 

LOAEL = 3.65 100 10 

Attenuation of pre-ovulatory 

lutenizing hormone (LH) surge, as a 

biomarker indicative of 

hypothalamic function disruption 

Six-month LH surge 

study-Rat 

Chronic RfD = 0.018 mg/kg/day 

Chronic PAD = 0.0018 mg/kg/day 

UF = Uncertainty Factor (100 is the result of a 10x for interspecies variability and 10x for intraspecies extrapolation); SF=Safety Factor; PAD 

= Population Adjusted Dose 

19
Table 3. Summary of Toxicological Endpoints and Other Factors Used in the Human 

Dietary (Food) Risk Assessment of Hydroxyatrazine, a Metabolite of Atrazine 

Exposure 

Scenario 

Dose 

(mg/kg/day) UF1 FQPA SF1 Endpoint Study 

Acute 

Dietary 

None selected na na 

An appropriate endpoint 

attributable to a single dose was 

not identified (no toxic effect 

seen) 

None selected 

Acute RfD = Not Established 

Chronic 

Dietary 

NOAEL = 1.0 

LOAEL = 7.75 100 1 Histopathological lesions of the 

kidneys 

Combined chronic 

toxicity/ 

carcinogenicity -Rat 

Chronic RfD = 0.01 

Chronic PAD = 0.01 mg/kg/day 

UF = Uncertainty Factor (100 is the result of a 10x for interspecies variability and 10x for intraspecies extrapolation); SF=Safety Factor; PAD 

= Population Adjusted Dose 

d. Exposure Assumptions 

The Agency conducts dietary (food) risk assessments using the Dietary Exposure 

Evaluation Model (DEEMTM). DEEM incorporates consumption data generated in USDA’s 

Continuing Survey of Food Intake by Individuals (CSFII), 1989-92. For the assessment of 

dietary exposure to residues of atrazine, monitoring data generated through the USDA Pesticide 

Data Program (PDP) and through the Food and Drug Administration (FDA) Surveillance 

Monitoring Program were used for wheat grain. Anticipated residue values from crop residue 

field trial studies and information from metabolism studies were used for most crops. For guava, 

tolerance level residues were used. 

For acute probabilistic dietary (food) risk assessments, the entire distribution of singleday food consumption events is combined with a distribution of residues to obtain a distribution 

of exposure in mg/kg/day. Chronic dietary (food) risk assessments use the three day average of 

consumption for each subpopulation combined with residues in commodities to determine 

average exposure in mg/kg/day. 

e. Food Risk Characterization 

Generally, a dietary (food) risk estimate that is less than 100% of the acute or chronic 

PAD does not exceed the Agency’s risk concern. Acute and chronic risk estimates from 

exposures to food associated with the use of atrazine did not exceed the Agency’s level of 

concern. 

20
1) Atrazine and Its Chlorinated Metabolites 

The percent acute PAD value for the relevant population subgroup considered under the 

acute risk assessment, females 13 to 50 years old, is less than 1 at the 99.9th percentile of 

exposure. The percent chronic PAD values for all exposed population subgroups were less than 

1, as well. These estimates of risk based on one-day and long-term exposures to atrazine and its 

chlorinated metabolites from residues on food alone are below the Agency’s level of concern. 

2) Hydroxyatrazine 

No acute toxicological endpoint was identified for hydroxyatrazine; therefore, an acute 

risk assessment for hydroxyatrazine and the hydroxylated metabolites was not conducted. The 

percent chronic PAD values were less than 1 for all population subgroups considered in the risk 

assessment. Therefore, estimates of risk based on long-term exposures to hydroxyatrazine from 

residues on food alone are below the Agency’s level of concern. 

2. Dietary Risk from Drinking Water 

Exposure to pesticides from drinking water can occur through residues in ground water 

and surface water. In the assessment for atrazine, EPA considers both acute (one day), 

intermediate-term (seasonal), and chronic (annual) exposures to residues in drinking water risks 

and uses actual monitoring data to characterize those risks. 

Drinking water risk from the application of atrazine is assessed based on exposures to 

combined residues of atrazine and the chlorinated metabolites. These are the only atrazinerelated compounds expected to occur in drinking water in significant quantities. Extensive 

monitoring data are available for atrazine parent in finished drinking water, and some monitoring 

data are available for the chlorinated metabolites. This monitoring data is the basis for the 

Agency’s drinking water risk assessment. To estimate the levels of chlorinated metabolites in 

areas where monitoring data is not available for those metabolites, the Agency developed a 

model based on the available monitoring data which the Agency believes provides a reasonable 

estimate of the levels of the chlorinated metabolites that could be expected in drinking water. 

A qualitative assessment of exposure to the hydroxy metabolites of atrazine in drinking 

water has been conducted by the Agency. Exposure to these compounds is expected to be 

significantly less than exposure to atrazine and the chlorinated metabolites based on the 

characteristics of these metabolites. Therefore, the Agency has not included the hydroxy 

metabolites in its quantitative risk assessment for drinking water 

Risk estimates for exposures to residues of atrazine and its chlorinated metabolites in 

drinking water are provided for populations receiving their drinking water from community 

water systems (CWS) using surface water, CWS using groundwater; and individual rural wells 

located in atrazine use areas. Exposure assessments were conducted for about 33 percent of the 

CWS using surface water in the United States, serving approximately 65 million people in 31 

atrazine use states. These CWS represent about 99% of atrazine use. The Agency uses 

21
monitoring data for finished (i.e., treated) drinking water in the assessment presented here. 

The Agency initially conducted a deterministic (screening-level) drinking water risk 

assessment for atrazine and its chlorinated metabolites. The initial assessment identified specific 

CWS and rural wells as having concentrations of atrazine and its chlorinated metabolites above 

the Agency’s level of concern. The CWS of concern were assessed probabilistically to refine the 

risk estimates; insufficient data were available to refine the risk estimates for rural wells. 

a. Drinking Water Levels of Comparison (DWLOC) 

To determine the maximum allowable contribution of water containing pesticide residues 

permitted in the diet, EPA first looks at how much of the overall allowable risk is contributed by 

food (and if appropriate, residential uses) then determines a “drinking water level of 

comparison” (DWLOC) to determine whether modeled or monitoring levels exceed this level. 

The Agency uses the DWLOC as a surrogate to capture risk associated with exposure from 

pesticides in drinking water. The DWLOC is the maximum concentration in drinking water that, 

when considered together with dietary (food) exposure, does not exceed a level of concern. 

Calculated DWLOCs are presented in Table 4 below. 

The results of the Agency’s drinking water analysis are summarized here. Details of this 

analysis are found in the HED Human Health Risk Assessment dated April 16, 2002, the EFED 

Environmental Risk Assessment dated April 20, 2002. 

Table 4. Summary of Lowest DWLOC Values for Atrazine and Its Chlorinated

Metabolites

Population Subgroup 

DWLOC (ppb) 

Acute (One Day) 

Exposure 

Intermediate (Seasonal) and 

Chronic (Annual) Exposure 

General Population not available 68 

Infants < 1 year old not available 12.5 

Children 1 to 6 not available 23 

Children 7 to 12 not available 53 

Females 13 to 50 298 60 

Males 13 to 19 not available 68 

Males 20 and over not available 68 

Seniors not available 68 

1) Community Water Systems (CWS) Using Surface 

22 
Water 

a) Acute Risk 

Based on the Agency’s deterministic assessment, the measured maximum one-day 

concentrations of atrazine plus estimates of the chlorinated metabolites in drinking water do not 

exceed the Agency’s level of concern for acute effects, regardless of source, for any relevant 

population subgroup. 

Based on the Agency’s screening-level deterministic assessment, one-day concentrations 

less than the DWLOC of 298 ppb do not exceed the level of concern for acute effects. The 

maximum measured concentration of atrazine and its chlorinated metabolites in any CWS 

monitoring for atrazine from 1993 to 1998 was 89 ppb. 

b) Intermediate-Term (Seasonal) and Chronic 

(Annual) Risk 

As stated previously, the drinking water concerns expressed for atrazine and its 

chlorinated metabolites do not apply to hydroxyatrazine because of its toxicology profile and 

environmental fate profile. 

Under the Agency’s screening-level assessment for intermediate-term and chronic 

exposures to atrazine and its chlorinated metabolites, 34 out of the 3670 CWS assessed were 

above the Agency’s level of concern based on a comparison of average seasonal concentrations 

to the chronic infant DWLOC of 12.5 ppb. These CWS were identified with quarterly average 

concentrations of chlorotriazines above levels of concern for infants in one, two, or three years 

between 1993 and 2001. In addition, several of the 34 had annual average concentrations above 

the levels of concern for children 1 to 6 years old and adults. 

A probabilistic exposure assessment was conducted for 39 CWS, most of which were 

identified as being of concern under the screening-level assessment, as listed above. Risk 

estimates based on a probabilistic exposure assessment that estimated 90-day average exposures 

to atrazine and the chlorinated metabolites indicate that 34 CWS have seasonal concentrations 

that exceed levels of concern for infants at the 99.9th percentile of exposure. 

In total, 34 CWS serving ~230,000 to 240,000 people had 90-day average exposures that 

exceeded levels of concern for infants in one, two, three, or four years between 1993 and 2001. 

Risk estimates for these CWS ranged from 100% to 670% of the chronic PAD for infants at the 

99.9th percentile of exposure, and several exceeded levels of concern for children 1 to 6 years 

old and adults as well. The CWS identified and the cPADs for these systems are listed in Table 

5 below. 

Table 5. Risk Estimates for High Seasonal Exposures to Atrazine in Finished Drinking 

Water at the 99.9th Percentile of Exposure* (CalandexTM) 

23
Community Water System (City/State) Infant 

% cPAD 

Children 1 - 6 

% cPAD 

Adult

 % cPAD 

Chariton, IA 235 <100 <100 

Sorento, IL 183 <100 <100 

Flora, IL 211 <100 <100 

W. Salem, IL 189 100 <100 

Farina, IL 189 <100 <100 

White Hall, IL 278 117 <100 

Carlinville, IL 128 <100 <100 

Gillespie, IL 550 222 172 

Hettick, IL 544 222 172 

Shipman, IL <100 <100 <100 

Palmyra-Modesto, IL 350 155 111 

N. Otter Twp ADGPTV, IL 189 <100 <100 

Kinmundy, IL 150 <100 <100 

Salem, IL 528 267 200 

Centralia, IL 255 100 <100 

Hillsboro, IL 272 117 <100 

Louisville, IL 344 122 <100 

North Vernon, IN 200 117 <100 

Omaha, IL 250 111 <100 

Holland, IN 244 128 <100 

Batesville, IN 261 111 <100 

Scottsburg, IN 267 150 105 

Lewisburg, KY 317 128 <100 

Marion, KY 317 128 <100 

Iberville, LA 261 117 <100 

Dearborn, MO 555 228 155 

Bucklin, MO 250 100 <100 

Vandalia, MO 189 105 <100 

Sardinia, OH 667 305 205 

Delaware, OH 155 <100 <100 

24
Community Water System (City/State) Infant 

% cPAD 

Children 1 - 6 

% cPAD 

Adult

 % cPAD 

Clermont County, OH 144 <100 <100 

Williamsburg, OH 289 122 <100 

Mt. Orab, OH 200 <100 <100 

Newark, OH 111 <100 <100 

The Agency notes that the Shipman reservoir no longer serves as a drinking water source; 

in 1999 the town of Shipman was switched to an alternative source of drinking water. The 

drinking water source at White Hall was switched from surface water to groundwater in 1997. It 

is the Agency’s understanding that Hettick, IL is also in the process of defining a new source for 

their drinking water needs and will close down the Hettick reservoir in the next couple of years. 

The seasonal pulses of atrazine and the chlorinated metabolites detected in monitoring 

data that resulted in exposures above the Agency’s level of concern spanned from several weeks 

to several months. Typically, for the year with exposures of concern, pulses lasted from early 

spring through the summer and into the fall, and some CWS had high pulses almost all year long. 

The higher concentrations occurring in the spring and early summer influence the 90-day 

average concentrations all year long. 

2) Groundwater 

Risk estimates based on screening-level assessments for 14,500 CWS using groundwater 

(~33 percent of groundwater CWS in the U.S.) do not exceed the Agency’s level of concern for 

acute or chronic effects. 

Data to estimate concentrations of the chlorinated metabolites of atrazine in these CWS 

using groundwater in 21 major atrazine use states have been developed. The highest 

concentration of atrazine and the chlorinated metabolites measured in any CWS in the data set 

was ~11 ppb. The 99th percentile concentration value for chlorotriazines in CWS with prior 

detections of atrazine was 1.9 ppb. Both the maximum measured value and the 99th percentile 

value are less than the acute DWLOC of 298 ppb, and do not exceed the Agency’s level of 

concern for acute effects. 

The 50th percentile concentration value was 0.180 ppb for CWS with prior detections. 

The mean concentration value at the 95 percent upper confidence bound was 0.55 ppb for CWS 

with prior detections. Both are less than the lowest intermediate-term to chronic DWLOC of 

12.5 ppb, and do not exceed the Agency’s level of concern for chronic effects. 

The Agency believes that CWS using groundwater are not impacted as heavily by 

atrazine use as CWS using surface water. 

3) Domestic Rural Wells 

25
Approximately 10% of the U.S. population receives their drinking water from rural wells, 

cisterns or springs. These sources of drinking water are not regulated under the SDWA. Acute 

exposures to atrazine and the chlorinated metabolites in drinking water from rural wells do not 

exceed the Agency’s level of concern. The maximum measured concentration of atrazine plus 

the chlorinated metabolites in the rural drinking water wells in atrazine use areas monitored by 

the registrant was 18 ppb; much less than the acute DWLOC (females 13 to 50) of 298 ppb. In 

addition, chronic exposures of adult populations using rural wells for drinking water do not 

exceed the Agency’s level of concern. 

However, the Agency has some concerns for chronic exposures of infants and children 

drawing drinking water from rural wells located directly in atrazine use areas, i.e., adjacent to 

fields where atrazine was used. Eight wells out of 1505 wells monitored had residues of atrazine 

and the chlorinated metabolites approaching, equal to, or greater than the chronic DWLOC 

(infants <1 year old) of 12.5 ppb. The 1505 wells monitored were selected based on their 

location in areas with high atrazine use. Of these, eight wells were resampled in March 2001, 

one sample per well. All samples showed concentrations of atrazine and the chlorinated 

metabolites less than the DWLOC of 12.5 ppb. 

Although the data indicate that levels are decreasing in these wells over time, the Agency 

continues to have uncertainty regarding subchronic and chronic exposures of infants using 

private rural wells in close proximity to atrazine use areas for the several reasons. It is difficult 

to interpret typical exposures in rural wells close to atrazine use areas based on two samples 

taken many years apart. There are approximately 13 million drinking water wells in the U.S., 

thus, the rural well survey (1,505 wells) is inadequate to fully assess exposures to the entire U.S. 

population that uses rural wells for drinking water. And finally, limited sampling from the wells 

in the survey results in a high level of uncertainty regarding exposures to atrazine and the 

chlorotriazine metabolites for the population using rural wells for drinking water. 

2. Residential Risk 

Atrazine is registered for use by homeowners to control weeds in turf grass. 

Homeowners mixing, loading, and applying atrazine products to their lawns may be exposed to 

atrazine through their skin and by inhaling dusts or sprays during application. Residential 

exposures are only applicable for those regions of the United States where atrazine is used on 

turf grass, generally the Southeast (including Florida). 

Adults or children can also be exposed to atrazine after application has occurred through 

contact with treated lawns or other turf areas (i.e., golf courses). In this instance, inhalation 

exposures are not expected; however, post-application dermal exposures for homeowners and 

children (yard work, walking, playing, crawling) and incidental oral exposure for toddlers are 

possible. Exposure data are not available on atrazine’s chlorinated metabolites and hydroxy 

metabolites; however, residues of the chlorinated metabolites and hydroxy metabolites are not 

expected to occur on the surfaces of plants. Therefore, any residential exposure to these 

metabolites would be minimal, and risks were not assessed. 

26
The Agency recognizes that there may be concerns for the potential for children’s 

exposure in the home as a result of agricultural uses of atrazine. Environmental concentrations 

of atrazine in homes may result from spray drift, track-in, or from redistribution of residues 

brought home on the farmworker’s clothing. Potential routes of exposure for children may 

include incidental ingestion and dermal contact with residues on carpets/hard surfaces. Studies 

are currently being pilot-tested that will look for sources of major pesticide exposure (including 

exposure to atrazine) and will attempt to quantify these exposures. 

Risk for all of the potentially exposed populations is measured by a Margin of Exposure 

(MOE). A MOE determines how close the amount of residue that individuals are exposed to 

come to a No Observed Adverse Effect Level (NOAEL), whether exposures are from the use of 

a pesticide or from pesticide residues after application. For atrazine, MOEs greater than 300 (10 

interspecies uncertainty x 10 intraspecies variability x 3 FQPA) do not exceed the Agency’s 

level of concern. 

a. Toxicity 

The toxicity of atrazine is integral to assessing the residential risk. The toxicological 

endpoints and other factors used in the residential risk assessment for atrazine are described 

below and summarized in Table 6. 

As mentioned earlier, the FQPA safety factor for residential exposures was reduced to 3x. 

This is considered adequate to protect the safety of infants and children in assessing residential 

exposure and risks because the uncertainties relating to drinking water exposure and the existing 

monitoring data included in the 10x FQPA safety factor for dietary exposure do not apply to 

residential exposure scenarios. Concerns for the effect of the neuroendocrine mode of action on 

the development of the young remain. The assumptions inherent to the Agency’s residential risk 

estimates based on screening-level procedures are conservative and protective. The 3x FQPA 

safety factor is being applied across all aggregate risk assessments based on estimated residential 

exposures for all populations considered in these risk assessments. 

Table 6. Summary of Toxicological Endpoints and Other Factors Used in the Atrazine

Residential Human Health Risk Assessment

Exposure 

Scenario 

Dose 

(mg/kg/day) UF1 

FQPA 

Safety 

Factor 

Endpoint Study 

Oral, 

Short-Term 

NOAEL= 6.25 

LOAEL = 12.5 100 3 

Delayed preputial separation in 

male offspring after 30 days of 

dosing. 

Pubertal assay (30­

day) NHEERL 

published literature 

Oral, 

IntermediateTerm 

NOAEL = 1.8 

LOAEL = 3.65 100 3 

Attenuation of pre-ovulatory 

lutenizing hormone (LH) surge, as a 

biomarker indicative of 

hypothalamic function disruption 

Six-month LH 

surge- Rat 

27
Table 6. Summary of Toxicological Endpoints and Other Factors Used in the Atrazine 

Residential Human Health Risk Assessment 

Exposure 

Scenario 

Dose 

(mg/kg/day) UF1 

FQPA 

Safety 

Factor 

Endpoint Study 

Dermal, 

Short-Terma NOAEL= 6.25 

LOAEL = 12.5 100 3 

Delayed preputial separation in 

male offspring after 30 days of 

dosing. Use of the dermal 

penetration factor yields a dose of 

104 mg/kg/day. 

Pubertal assay (30­

day) NHEERL 

published literature

 Dermal, Attenuation of pre-ovulatory Six-month LH 

Intermediateand

 Long-Termb 

NOAEL= 1.8 

LOAEL = 3.65 100 3 

lutenizing hormone (LH) surge, as a 

biomarker indicative of 

hypothalamic function disruption 

surge- Rat 

Inhalation, 

Short-Term c 

NOAEL= 6.25 

LOAEL = 12.5 100 3 

Delayed preputial separation in 

male offspring after 30 days of 

dosing. 

Pubertal assay (30­

day) NHEERL 

published literature

 Inhalation, Attenuation of pre-ovulatory Six-month LH 

Intermediate 

and 

NOAEL= 1.8 

LOAEL = 3.65 100 3 lutenizing hormone (LH) surge, as a 

biomarker indicative of 

surge-Rat 

Long-Termc hypothalamic function disruption 

1

UF = Uncertainty Factor (100 is the result of a 10x for interspecies variability and 10x for intraspecies extrapolation)

a = The NOAEL of 6.25 mg/kg/day is multiplied by a 3.6 dermal penetration factor.

b = 6% dermal absorption factor for route-to-route extrapolation.

c = 100% absorption factor for route-to-route extrapolation.

Residential = A MOE of 300 is required and includes the 3x FQPA Safety Factor

b. Exposure Assumptions 

Residential exposures to atrazine are expected to be short-term in duration (1 to 30 days), 

based on label directions that specify no more than two applications of atrazine to home lawns. 

Exposures greater than 30 days are not expected because no currently registered residential use 

products would result in exposures of this duration due to the use pattern and turf residue 

dissipation data on atrazine. 

Chemical-specific exposure data, including a Turf Transferable Residue study on 

atrazine, and data on residential handlers applying granular and liquid formulations submitted by 

the Outdoor Residential Exposure Task Force (ORETF) were used to assess the exposure to 

atrazine as a result of residential application. In addition, analyses were performed using the unit 

exposure values in the Pesticide Handlers Exposure Database (PHED), Version 1.1 (August 

1998) and using standard assumptions (average body weight, work day, daily areas treated, 

volume of pesticide used, etc.). 

The quality of the data and exposure factors represents the best sources of data currently 

28
available to the Agency for completing these kinds of assessments. For example, if appropriate 

chemical-specific exposure data are available for atrazine, those data are used instead of the 

more generic PHED data. The quality of the data used for each scenario assessed, standard 

procedures, and any assumptions made are further discussed in the April 16, 2002, Revised 

Human Health Risk Assessment; the August 2002 Revised Occupational and Residential Risk 

Assessment; and the January 31, 2003, Addendum to the Revised Human Health Risk 

Assessment available in the public docket and online. 

Anticipated use patterns and application methods, range of application rates, and area of 

lawn treated per day were derived directly from current atrazine labels for residential products. 

Application rates specified on atrazine labels for residential uses range up to 2 pounds of active 

ingredient per acre on residential turf. 

The Agency also considered exposure to adults or children entering or playing on treated 

lawns or entering homes after application of atrazine products (post-application exposure). 

These activities are expected to result in short-term exposure (1 to 30 days), based on atrazine 

turf residue dissipation data and atrazine’s residential use pattern. These data show that atrazine 

has a half-life on turf of up to 5 days after spraying or 9 days after granular application, and 

requires several weeks to dissipate. However, the Agency does not expect exposures greater 

than 30 days, even considering the slow dissipation rates, because the label prohibits application 

more than twice per year. 

Residential post-application exposure assessments assumed residents wear the following 

attire: short sleeved shirt, short pants, shoes and socks, and no gloves. 

c. Residential Applicator Risk 

The anticipated use patterns and current labeling for atrazine homeowner products 

indicate 5 major exposure scenarios for residential applicators, as follows: 

(1) mixing/loading/applying liquid formulations using a backpack sprayer, 

(2) mixing/loading/applying liquid formulations for application with a low pressure 

handwand, 

(3) mixing/loading/applying liquid formulations for hose-end sprayer, 

(4) loading/applying granular formulations with a push type spreader, and 

(5) loading/applying granular formulations with a bellygrinder. 

The Agency does not believe the addition of personal protective equipment (PPE) to 

residential handlers (as used for assessing occupational handler risk) is appropriate for 

homeowner handler exposure assessments. Homeowners often lack access to PPE and do not 

possess expertise in the proper use of PPE. As a result, homeowner handler assessments are 

completed using a single scenario based on the use of short-sleeved shirts and short pants, 

common homeowner attire during the pesticide application season. In addition, as mentioned 

above, only short-term exposures were assessed, as the Agency does not believe homeowners 

who apply atrazine will be exposed for more than a few consecutive days. 

29
All of the residential handler exposure scenarios considered in the risk assessment, with 

the exception of the scenario for application of granular formulations via a bellygrinder as a 

broadcast application, were below the Agency’s level of concern (MOEs > 300). MOEs 

calculated for each homeowner handler scenario are presented in Table 7, as follows: 

Table 7. Homeowner Uses and Risk Concerns (combined dermal & inhalation MOEs) 

Scenario Rate 

(lb ai/A) Short-Term MOE 

(1) Mixing, loading, and applying liquid formulations via backpack 

sprayer 

2 28,000 

(2) Mixing, loading, and applying liquid formulations via low pressure 

handwand 2 1,600 

(3) Mixing, loading, and applying liquid formulations via hose-end 

sprayer 

2 640a 

(4) Loading and applying granular formulations via push type spreader 2 1,100a 

(5) Loading and applying granular formulations via bellygrinder 

2 

65 (broadcast) 

1,400 (spot 

treatment) 

a

 Calculated using ORETF Unit Exposure Values 

d. Post-Application Residential Risk 

Atrazine can be used on home lawns, golf courses, and on other turf areas where 

exposure to adults and children may occur. Dermal exposure to atrazine may result from 

entering the treated area, performing yard work (e.g., mowing), playing or performing other 

recreational activities (e.g., golfing) on the treated areas. In addition, incidental oral postapplication exposure to children may occur from “hand-to-mouth” (i.e., ingestion of grass, soil 

and/or granular pellets; or hand-to-mouth contact) exposure when reentering treated lawns. 

The Agency does not expect post-application inhalation exposure to atrazine to occur 

because of low chemical vapor pressure and dilution of vapor outdoors. Thus, this exposure was 

not assessed. Handler study data support this conclusion. 

Representative turf reentry activities include, but are not limited to: 

(1) Adults involved in a low exposure activity, such as golfing or walking on treated turf. 

(2) Adults mowing or other moderate contact activity, for 1-2 hours. 

(3) Adults involved in a high exposure activity, such as heavy yard work (doses similar to 

occupational scenarios for cutting and harvesting sod). 

(4) Children involved in high exposure activities on turf. 

The Agency has risk concerns for post-application residential exposures to children from 

incidental oral contact. In children exposed to treated lawns after application of liquid atrazine 

30
formulations, hand-to-mouth activities and combined oral exposures result in MOEs above the 

Agency’s level of concern. MOEs are 210 for hand-to-mouth activities and 200 for combined 

oral exposures. In addition, for children exposed to treated lawns after granular applications, the 

Agency has concerns for incidental ingestion of granules. The MOEs for this scenario range 

from 16 to 110. 

Table 8: Residential Short-Term Post-Application Risk Estimates from Atrazine 

Application to Lawns 

Scenario 

Application 

Rate 

(lb ai/A) 

MOE 

Liquid Granular 

GA NC GA1 FL1 

Adult 

Dermal 

Turf Contact 2 510 4300 1200 

Walking, Golfing 2 7400 62,000 17,000 

Push Mowing Lawn 2 15,000 120,000 34,000 

Child 

Dermal Turf Contact 2 310 2,600 690 

Oral 

Hand to Mouth Activity 2 210 950 

Turfgrass/Object 

Mouthing 

2 3300 

Ingestion of Soil 2 62,500 

Combined2 2 200 730 

Ingestion of Granules 2 n/a 16-31 (1.5% ai) 

57-110 (0.42% ai) 

1 The MOEs presented here represent non-irrigated turf. As these MOEs were acceptable, irrigated turf 

MOEs, generally higher than non-irrigated, were not presented. 2 Combined includes Hand-to-mouth activity, turfgrass/object mouthing; and ingestion of soil. Ingestion of 

granules is not included because this is considered an infrequent, episodic event. 

Adults may reasonably be expected to perform more than one activity on treated lawns in 

a single day, but an eight-hour duration of exposure is unlikely. Therefore, it is reasonable to 

aggregate the exposures from playing/gardening (highest exposure rate), walking, and mowing 

(lower exposure rate) for a single MOE. The MOE for all post-application adult exposures 

combined is 460 and is above the Agency’s level of concern. It is also possible that an adult 

would apply herbicide spray to a lawn and then play on it or mow it later that day. In such an 

event, the aggregated dermal MOE for the day would be slightly lower than the target 300 for 

that day (MOE=270), based on the liquid application study values, but not based on the granular 

residue data. However, this not very likely and is considered a high-end estimate of exposure. 

31
It is likely that dermal and oral incidental exposures may occur in the same day for 

children playing on atrazine-treated lawn. It can be seen from the MOEs presented in Table 8 

that the incidental hand-to-mouth (licking fingers) exposure estimate constitutes most of this oral 

exposure. The overall MOE of 200 is only slightly less than the MOE of 210 for the hand-tomouth estimate. The individual dermal and oral routes of exposure each exceed the level of 

concern, and aggregating these estimates results in an even lower MOE. Ingestion of granules is 

not aggregated because it is considered an infrequent, episodic event. 

3. Aggregate Risk 

Aggregate risk assessments have been conducted for acute, short-term, and intermediateterm to chronic exposures to atrazine and the chlorinated metabolites. Aggregate risk 

assessments look at the combined risk from dietary exposure (food and drinking water) and nonoccupational (e.g., residential, golfers, etc...). The acute aggregate risk assessment combines 

exposures to atrazine and the chlorinated metabolites in food and drinking water. The short-term 

aggregate risk assessment combines exposures to atrazine and the chlorinated metabolites in 

food and drinking water with residential exposures to atrazine, per se, occurring between 1 and 

30 days after use of atrazine products at home. The intermediate-term and chronic aggregate risk 

assessment combines exposures to atrazine and the chlorinated metabolites in food and drinking 

water alone because intermediate-term (30 days to several months) and chronic (several months 

to lifetime) exposure scenarios for the registered non-occupational uses of atrazine are not 

expected. 

Although a risk assessment for exposures to atrazine's hydroxylated metabolites in food 

was conducted, risk assessments aggregating exposures to atrazine's hydroxylated metabolites in 

food, drinking water, and in residential settings were not. There is limited data on 

hydroxyatrazine in water, and exposure to the hydroxy metabolites of atrazine in drinking water 

is not expected to be significant relative to the chlorinated metabolites. In addition, the Agency 

does not expect exposure to hydroxyatrazine from applications of atrazine to turf because 

hydroxyatrazine is formed within plant tissues, not on plant surfaces. 

a. Acute Aggregate Exposure and Risk Estimates 

The aggregate risk assessment for acute exposures to atrazine and the chlorinated 

metabolites combines high-end one-day exposures through food and drinking water alone. The 

Agency does not believe that high-end exposures through food, drinking water, and residential 

use will all occur on the same day. Therefore, acute aggregate risk estimates are the same as 

those presented for acute drinking water risks. Exposure to atrazine from food sources and 

drinking water do not exceed the Agency’s level of concern for acute dietary risk for any 

relevant subgroup, as described previously in Section III.A.2.a.3. 

b. Intermediate-Term and Chronic Aggregate Exposure and Risk 

Estimates 

The aggregate risk assessment for intermediate-term and chronic exposures to atrazine 

32
and the chlorinated metabolites combines estimates of high-end seasonal or long-term average 

exposures to atrazine in drinking water with long-term average exposures to atrazine in food. 

Neither intermediate-term nor long-term (chronic) exposures are expected to occur in the home 

from residential uses of atrazine. Therefore, intermediate-term and chronic aggregate risk 

estimates are the same as those presented for intermediate-term and chronic drinking water risks 

(see section III.A.2.a.3). Infants and children are potentially at risk from exposures to combined 

residues of atrazine plus its chlorinated metabolites from 34 CWS using surface water based on 

available monitoring data. Aggregate intermediate-term and chronic exposures in CWS using 

groundwater are not of concern. 

c. Short-Term Aggregate Exposure and Risk Estimates

 Short-term estimates of aggregate risk were calculated for adult applicators and children 

and adults exposed to residues of atrazine after application to home lawns. Short-term aggregate 

risk estimates that include residential exposures are only applicable for those regions of the 

United States where atrazine is used on turf grass (residential and golf courses), generally the 

Southeast (including Florida). 

The theoretical upper limit in drinking water for short-term exposures is referred to as a 

short-term DWLOC and is based on exposure estimates for adults and children from average 

residues of atrazine in food and exposure to high-end atrazine residues during application or 

immediately after application of atrazine to lawns. If the short-term DWLOC values are greater 

than the measured average concentrations for atrazine residues in surface water and 

groundwater, there is no concern for short-term aggregate exposures to atrazine residues through 

food, drinking water, and non-occupational uses. Measured concentrations of atrazine residues 

in surface water and groundwater from monitoring data (as presented earlier in this document) 

were compared to the calculated short-term DWLOCs. 

1) Adult Handlers 

Short-term estimates of aggregate risk to adults applying atrazine products to the lawn 

and garden combines exposures through the dermal, dietary (food and drinking water), and 

inhalation routes. These exposures have a common toxic effect, delayed puberty as a biomarker 

for neuroendocrine effects. 

Table 9 below presents the results of the Agency’s short-term aggregate risk assessment 

for adult handlers of atrazine. Of the five exposure scenarios evaluated, only applications of 

granular formulations of atrazine applied over 0.5 acres with a belly-grinder results in aggregate 

exposures that exceed the Agency’s level of concern. 

Aggregate short-term DWLOC values are presented for the five adult handler scenarios 

in Table 9. The first four DWLOCs presented are greater than the measured maximum weekly 

concentration of 89 ppb atrazine and the chlorotriazines in finished drinking water; thus, these 

scenarios are not of concern to the Agency. A DWLOC of 0 is assigned for adults applying via 

belly grinder because this residential scenario alone exceeds the Agency’s level of concern; thus, 

33
this scenario is also of concern when aggregated with dietary and drinking water routes of 

exposure. 

Table 9. Short Term Aggregate DWLOCs - Adults applying atrazine at 2 lb ai/A to lawns. 

Exposure Scenario Aggregate MOE 

(Dermal and Inhalation) 

Short Term 

DWLOC (ppb) 

(1) Mixing, loading, and applying liquid formulations via 

backpack sprayer 28,000 219 

(2) Mixing, loading, and applying liquid formulations via 

low pressure handwand 1,600 273 

(3) Mixing, loading, and applying liquid formulations via 

hose-end sprayer 

640 105 

(4) Loading and applying granular formulations via pushtype spreader 11,000 159 

(5) Loading and applying granular formulations via belly 

grinder 65 0 

2) Adult Post-Application 

Short-term estimates of aggregate risk for adults from post-application exposures 

combine dietary exposure and post-application dermal exposures after atrazine lawn treatment . 

Short-term dermal and dietary exposures have a common toxic effect: delayed puberty as a 

biomarker for neuroendocrine effects. 

Table 10 summarizes the results of the Agency’s aggregate risk assessment for short-term 

exposures of adults exposed to atrazine-treated lawns immediately after application. Short-term 

aggregate risk estimates do not exceed the Agency’s level of concern. Weekly concentrations of 

atrazine and the chlorotriazine metabolites have been measured in drinking water up to 89 ppb; 

since this concentration is less than the remaining DWLOCs, the aggregate risk is acceptable. 

Table 10. Short Term Aggregate DWLOCs - Adults exposed to atrazine after 

application to lawns at 2 lb ai/A. 

Exposure Scenario (formulation) Dermal MOE Short Term 

DWLOC (ppb) 

Dermal Turf Contact (liquid) 510 130 

Dermal Turf Contact (granular) 1200 157 

Dermal Contact Walking/Playing Golf (liquid) 7,800 210 

Dermal Contact Walking/Playing Golf (granular) 16,000 215 

Dermal Contact Pushing Lawn Mower (liquid) 16,000 214 

34
Table 10. Short Term Aggregate DWLOCs - Adults exposed to atrazine after 

application to lawns at 2 lb ai/A. 

Exposure Scenario (formulation) Dermal MOE Short Term 

DWLOC (ppb) 

Dermal Contact Pushing Lawn Mower (granular) 35,000 217 

3) Child Post-Application 

Short-term estimates of aggregate risk to toddlers from post-application residential 

exposure to atrazine combine dietary exposures with post-application dermal and incidental oral 

exposures after atrazine lawn treatment. 

Aggregate risk estimates for short-term exposures to toddlers playing on liquid atrazinetreated lawns exceed EPA’s level of concern. Risks to children from aggregated oral residential 

post-application exposures (hand-to-mouth transfer of residues, grass and soil ingestion activities 

by toddlers on grass) are of concern for liquid formulations (MOE = 200); therefore, any 

aggregation through the dermal, inhalation or dietary pathways would result in risk estimates that 

further exceed the Agency’s level of concern. 

Toddlers’ risk estimates from individual or aggregated (combined) pathways for 

incidental oral exposures based on granular formulations do not exceed the Agency’s levels of 

concern; i.e., a MOE of 730. Toddlers’ risk estimates from dermal exposures based on granular 

formulations also do not exceed the Agency’s levels of concern; i.e., MOEs of 690 (for 

applications that are not watered-in immediately after application and 2000 for applications that 

are watered-in immediately after application). Combined dermal and incidental oral exposures 

for toddlers result in a MOE of 350 or greater and also do not exceed the Agency's level of 

concern. Short-term DWLOCs for toddlers’ post application aggregate exposures, inclusive of 

dermal, incidental oral, and dietary (food + drinking water) exposures, do not exceed HED’s 

level of concern for granular formulations watered-in after application to turf. Short-term 

DWLOCs for toddlers’ post application aggregate exposures exceed the Agency’s level of 

concern for granular formulations. 

Exposure to atrazine through ingestion of granules by toddlers result in MOEs of 16 to 

110. Granule ingestion by toddlers is considered an episodic event (a stand alone incident) and 

has not been aggregated with either other incidental oral exposures or dermal and dietary 

exposures. 

Table 11 below presents the short-term aggregate MOEs and DWLOCs for toddlers 

exposed to atrazine after lawn applications. 

35
Table 11. Short-Term Aggregate DWLOCs - Toddlers exposed to atrazine after liquid 

and granular applications to lawns. 

Type of Exposure Formulation/Application 

Rate (lbs ai/acre) Dermal MOE 

Aggregate 

Incidental Oral 

MOE 

Short-Term 

DWLOC (ppb) 

Dermal Contact on Turf 2 lb ai/acre (liquid) 310 200 zero 

Dermal Contact on Turf 1 lb ai/acre (liquid) 610 390 zero 

Dermal Contact on Turf 2 lb ai/acre (granular) 

without watering-in 

690 730 12 - 14 

Dermal Contact on Turf 2 lb ai/acre (granular) 

with watering-in 

2000 730 35 - 39 

4. Occupational Risk 

Workers handling pesticide products can be exposed to atrazine through mixing, loading, 

and/or applying this pesticide, and through reentering treated sites. Occupational handlers of 

atrazine include: individual farmers and other growers who mix, load, and/or apply pesticides; 

commercial, professional, or custom agricultural applicators; commercial pest control operators; 

and lawn care and turf management professionals. The post-application occupational risk 

assessment considered exposures to workers entering treated sites in agriculture. Risk for all of 

these potentially exposed populations is measured by a Margin of Exposure (MOE) which 

determines how close the occupational or residential exposure comes to a No Observed Adverse 

Effect Level (NOAEL). Generally, MOEs greater than 100 do not exceed the Agency’s risk 

concern. 

a. Toxicity 

The toxicity of atrazine is integral to assessing the occupational risk. The Agency has 

conducted short-term and intermediate-term dermal and inhalation exposure assessments for the 

occupational handler. In addition, the Agency has conducted short-term post-application dermal 

and inhalation exposure assessments. Long-term (chronic) occupational exposures are not 

anticipated based on atrazine’s use pattern. 

All risk estimates are based on the most current toxicity information available for 

atrazine, including a 21-day dermal toxicity study. The toxicological endpoints, and other 

factors used in the occupational risk assessments for atrazine are summarized in Table 12 below. 

Please note that the occupational dermal and inhalation endpoints are the same as those used in 

the dietary drinking water assessment and in the residential risk assessment. 

A dermal absorption factor of 6% (rounded up from 5.6%) was selected, based on a 

human study in which 10 volunteers were exposed to a single topical dose of atrazine. An 

inhalation absorption factor of 100% is applied. The FQPA Safety Factor is not applicable to the 

Occupational Risk Assessment. 

36
Table 12. Summary of Toxicological Endpoints and Other Factors Used in the 

Atrazine Occupational Risk Assessment 

Exposure 

Scenario 

Dose 

(mg/kg/day) UF1 Endpoint Study 

Dermal, 

Short-Terma NOAEL= 6.25 

LOAEL = 12.5 100 

Delayed preputial separation in 

male offspring after 30 days of 

dosing. Use of the dermal 

penetration factor yields a dose of 

104 mg/kg/day. 

Pubertal assay (30­

day) NHEERL 

published literature

 Dermal, 

IntermediateTermb 

NOAEL= 1.8 

LOAEL = 3.65 100 

Attenuation of pre-ovulatory 

lutenizing hormone (LH) surge, as a 

biomarker indicative of 

hypothalamic function disruption 

Six-month LH 

surge- Rat 

Inhalation, 

Short-Term c 

NOAEL= 6.25 

LOAEL = 12.5 100 

Delayed preputial separation in 

male offspring after 30 days of 

dosing. 

Pubertal assay (30­

day) NHEERL 

published literature

 Inhalation, 

IntermediateTermc 

NOAEL= 1.8 

LOAEL = 3.65 100 

Attenuation of pre-ovulatory 

lutenizing hormone (LH) surge, as a 

biomarker indicative of 

hypothalamic function disruption 

Six-month LH 

surge-Rat 

1

UF = Uncertainty Factor (100 is the result of a 10x for interspecies variability and 10x for intraspecies

extrapolation)

a = The NOAEL of 6.25 mg/kg/day is multiplied by a 3.6 dermal penetration factor.

b = 6% dermal absorption factor for route-to-route extrapolation.

c = 100% absorption factor for route-to-route extrapolation.

Atrazine has low acute dermal and inhalation toxicity. It is non-irritating to skin, 

minimally irritating to the eyes and is not a skin sensitizer. It is classified under Category III for 

acute oral toxicity. Table 13 summarizes the acute toxicity of atrazine. 

Table 13. Summary of Results from Acute Toxicity Studies of Technical Atrazine 

Guideline 

No. Test Results Toxic Category 

81-1 Acute Oral LD50 - rat LD50 > 1,869 mg/kg (M&F 

combined)

 III 

81-2 Acute Dermal LD50 - rat LD50 > 2,000 mg/kg (M&F 

combined)

 III 

37
Guideline 

No. Test Results Toxic Category 

81-3 Acute Inhalation LC50 ­

rat 

LC50 > 5.8 mg/L (M&F combined) IV 

81-4 Eye Irritation - rabbit Non-irritant IV 

81-5 Dermal Irritation - rabbit Non-irritant IV 

81-6 Dermal Sensitization Non-sensitizer --­

b. Occupational Exposure 

Several chemical-specific studies that were submitted to the Agency by the technical 

registrant were used together were used to assess the occupational handler risks from use of 

atrazine for most exposure scenarios. Exposure studies submitted to the Agency by the Outdoor 

Residential Exposure Task Force (ORETF) were also used in the occupational (and nonoccupational) risk assessments for applicators. 

In addition, the Agency generated MOEs to assess risk to commercial handlers engaged 

in impregnating atrazine onto dry bulk fertilizer using dermal and inhalation unit exposure data 

from the Pesticide Handlers Exposure Database (PHED), Version 1.1 (August 1998). The 

PHED scenario for mixing/loading liquids using a closed system were used as a surrogate to 

estimate these exposures. However, such an exposure surrogate is less appropriate for 

estimating exposures due to transferring the treated dry bulk fertilizer from an auger truck to the 

application equipment. There are no data or reasonable surrogate available for this operation. 

Three chemical-specific studies, one of dislodgeable foliar residue on corn, and two of 

transferable turf residues (TTR), were submitted to the Agency and used in the post-application 

occupational risk assessment. In addition, transfer coefficients used were based on data 

submitted by the Agricultural Reentry Task Force (ARTF), where possible. Most of the atrazine 

used in agriculture is applied to corn and sorghum early in the season, either before weeds 

emerge or when the crops are quite small, generally less than 12 inches high. This, and the 

degree of mechanization in cultivating these crops, leads the Agency to conclude that postapplication exposure to workers is low. 

Anticipated use patterns and application methods, range of application rates, and daily 

amounts treated were derived from current labeling. Maximum application rates specified on 

atrazine labels were 2.0 lb ai/A, with a few exceptions. Maximum label rates were used to 

estimate handler exposure. The Agency uses acres treated per day values that are thought to 

represent an eight-hour workday for a particular type of application equipment or a specific crop. 

Occupational handler exposure assessments are conducted by the Agency using different 

levels of personal protection. The Agency typically evaluates all exposures with baseline 

protection and then adds additional protective measures using a tiered approach to obtain an 

appropriate MOE (i.e., going from minimal to maximum levels of protection). The lowest suite 

38
of personal protective equipment (PPE) is baseline PPE. If required (i.e., MOEs are less than 

100), increasing levels of risk mitigation PPE are applied. If MOEs are still less than 100, 

engineering controls (EC) are applied. The levels of protection that formed the basis for 

calculations of exposure from atrazine activities include: 

• Baseline: Long-sleeved shirt and long pants, shoes and socks (includes 

gloves for the applicator in scenario 5). 

• PPE: Baseline + coveralls, chemical-resistant gloves, and a dust/mist 

respirator (see table for specifics by scenario) 

• Engineering controls: Engineering controls, such as closed cab tractor for application 

scenarios, or a closed mixing and loading system such as a farm 

closed mechanical transfer system for liquids or a package based 

system. Some engineering controls are not feasible for certain 

scenarios. Some formulation types qualify as engineering controls 

for the purpose of controlling exposure during mixing and loading, 

such as water soluble packets. 

c. Occupational Handler Risk Summary 

Inhalation and dermal exposure to atrazine can result from occupational use. The 

Agency assessed dermal and inhalation risks (MOEs) for each crop currently registered for 

atrazine. For atrazine, occupational MOEs greater than 100 are not of risk concern to the 

Agency. 

1) Agricultural Handler Risk 

The Agency has determined that there is potential atrazine exposure to mixers, loaders, 

applicators, and other handlers using atrazine in accordance with the current use patterns. 

Fourteen major agricultural handler exposure scenarios were identified for atrazine, as listed 

below. The major handler scenarios involved multiple crops and application rates, resulting in 

several different exposure estimates. The largest agricultural use of atrazine involves the 

mixing, loading and application of atrazine to row crops and results in the largest potentially 

exposed occupational population. 

(1a) mixing/loading liquid formulations for aerial application, 

(1b) mixing/loading liquid formulations for groundboom application, 

(1c) mixing/loading liquid formulations for rights-of-way sprayer application to 

roadside, 

(1e) mixing/loading/incorporating liquid formulations into liquid and dry bulk 

fertilizer (commercial & on-farm techniques), 

(2a) mixing/loading dry flowable formulations for aerial application, 

(2b) mixing/loading dry flowable formulations for groundboom application, 

(2c) mixing/loading dry flowable formulations for rights-of-way sprayer application to 

roadside, 

(3) loading granular formulations, 

39
 (4) applying liquids with aircraft, 

(5) applying liquids with groundboom sprayer, 

(6) applying liquids to roadsides with rights-of-way sprayer, 

(8) applying impregnated dry bulk fertilizer with a tractor-drawn spreader, 

(9) applying granular formulations with a tractor-drawn spreader, 

(15) flagging for aerial spray applications 

(16a) mixing/loading wettable powder formulations for aerial application; and 

(16b) mixing/loading wettable powder formulations for groundboom application. 

PPE requirements on current atrazine labels are typically long-sleeved shirt, long pants, 

shoes, socks and waterproof gloves. Mixers and loaders must also wear protective eyewear. 

(mixers/loaders). 

As summarized in Table 14, occupational risks are of concern (i.e MOEs < 100) for some 

scenarios even when maximum PPE are utilized. Handler risks are also of concern for a few 

scenarios with engineering controls. Engineering controls are considered to be the maximum 

feasible mitigation. These involve several scenarios for the incorporation of atrazine into liquid 

or dry bulk fertilizer, handlers mixing and loading wettable powders for application to 350 acres 

of sugarcane at 4 lb ai/A, and handlers applying liquids with a right of way sprayer to 40 acres of 

roadsides at 2 lb ai/A. 

40
Table 14. Occupational Handler Aggregate (Dermal plus Inhalation) Margins of Exposure (PHED) 

Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Short Term 

Intermediate 

Term 

Short Term 

Intermediate 

Term 

Sho

Mixer/Loader 

(1a) Liquid formulations for aerial application 

Conifer forests Christmas tree farms 

4 350 2 0.4 248 61 520 

Sugarcane 4 

350 

2 0.4 248 61 520 

2.6 3 0.7 381 94 800 

Chemical fallow 3 1200 1 na 96 na 200 

350 2 0.6 330 82 690 

1.4 1200 1 na 206 na 430 

350 5 1.3 708 170 1500 

CRP or grasslands 2 1200 1 na 144 na 300 

350 4 0.9 495 120 1000 

Corn Sorghum 

2 1200 1 na 144 na 300 

350 4 0.9 495 120 1000 

1 1200 2 na 289 na 610 

350 7 2 991 240 2100 

Sod Farms 4 (FL) 350 2 0.4 248 61 520 

2 350 4 1 495 120 1000 

41
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

(1b) Liquid formulations for groundboom application 

Macadamia nuts Guava Conifers 

4 80 8 2 1084 270 2300 

Sugarcane 4 80 8 2 1084 270 2300 

2.6 80 12 3 1667 410 3500 

Chemical Fallow 3 450 2 na 257 na 540 

200 4 1 578 140 1200 

1.4 450 4 na 550 na 1200 

200 9 2 1238 310 2600 

CRP or grasslands 2 450 3 na 385 na 810 

200 6 2 867 210 1800 

Corn Sorghum 

2 450 3 na 385 na 810 

200 6 2 867 210 1800 

1 450 6 na 771 na 1600 

200 12 3 1734 430 3600 

Roadsides 1 40 62 15 8669 2100 18,0

2 31 8 4335 1100 9100 

Sod farms 4 (FL) 80 8 2 1084 270 2300 

2 80 16 4 2167 540 4600 

42
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

(1c) Liquid formulations for 

Roadsides 1 40 62 15 8669 2100 18,0

rights-of-way sprayer Bermuda grass rights-of-way 2 40 31 8 4335 1100 9100 (1e) Incorporating liquid formulations into liquid or dry bulk fertilizer 

Commercial fertilizer for corn, sorghum (PHED data) 

2 960 tons see engineering controls 64 

500 tons 120 

1 960 tons 120 

500 tons 230 

Commercial fertilizer for corn, 2 500 tons see engineering controls 170 sorghum (Helix study data) 

1 see engineering controls 350 

On-farm fertilizer for corn, 2 160 8 na 700 na 1900 sorghum 

1 160 15 na 1400 na 3800 

(2a) Dry flowable for aerial application 

Conifer forests Christmas tree farms 

4 350 66 16 105 26 380 

Sugarcane 4 350 66 16 105 26 380 

2.6 350 100 25 161 40 580 

Chemical fallow 3 1200 26 na 41 na 150 

350 88 22 140 35 500 

1.4 1200 55 na 87 na 320 

350 190 47 300 74 1100 

CRP or grasslands 2 1200 38 na 61 na 220 

43
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

350 130 33 210 52 750 

Corn 2 1200 38 na 61 na 220 Sorghum 

350 130 33 210 52 750 

1 1200 77 na 122 na 440 

350 260 65 420 100 1500 

Sod farms 4 (FL) 350 66 16 105 26 380 

2 350 130 33 210 52 750 

(2b) Dry flowable for groundboom application 

Macadamia nuts Guava Conifers 

4 80 290 71 459 110 1600 

Sugarcane 4 80 290 71 459 110 1600 

2.6 80 440 110 706 170 2500 

Chemical fallow 3 450 68 na 109 na 400 

200 150 38 245 61 880 

1.4 450 150 na 233 na 840 

200 330 82 525 130 1900 

CRP or grasslands 2 450 100 na 163 na 580 

200 230 57 367 91 1300 

Corn Sorghum 

2 450 100 na 163 na 580 

200 230 57 367 91 1300 

44
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

1 450 210 na 326 na 1200 

200 460 110 734 180 2600 

Roadsides 1 40 2300 570 3672 910 13,0

2 40 1200 290 1836 450 6600 

Sod farms 4(FL) 80 290 71 459 110 1600 

2 80 580 140 918 230 3300 

(2c)Dry flowable for rights-of-way 

Roadsides 1 40 2300 570 3672 910 13,0

2 40 1200 290 1836 450 6600 

(3) Granular formulations 

Sod farms 2 80 1200 310 5023 1200 62,0

(16a) Wettable powders for aerial application 

Sugarcane 4 350 1.2 5.2 17 4.1 580 

2.6 1.8 3 26 6.3 380 

Chemical Fallow 3 1200 0.5 na 6.5 na 150 

1.4 1 na 14 na 310 

Corn, Sorghum 2 1200 0.7 na 9.7 na 220 

350 2.4 4 33 8.2 750 

1 1200 1.4 na 19 na 440 

350 4.7 7 66 16 1500 

45
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

(16b) Wettable powders for groundboom application 

Macadamia nuts 4 40 10 16 150 36 3300 Sugarcane 4 200 2.1 3 29 7.2 660 Sod farms (FL) 4 80 5.2 8 73 18 1600 

Applicator 

(4) Applying liquids with aircraft 

Conifer forests Christmas tree farms 

4 350 See engineering controls 850 

Sugarcane 4 350 See engineering controls 850 

2.6 35 1300 

Chemical fallow 3 1200 See engineering controls 330 

350 1100 

1.4 1200 710 

350 2400 

CRP or grasslands 2 1200 See engineering controls 500 

350 1700 

Corn Sorghum 

2 1200 See engineering controls 500 

350 1700 

1 1200 990 

350 3400 

Sod farms 4 (FL) 350 See engineering controls 850 

2 350 1700 

46
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

(5) Applying liquids by groundboom 4 

Macadamia nuts Guava Conifers 

4 80 860 210 1690 420 4000 

Sugarcane 4 80 860 210 1690 420 4000 

2.6 80 1300 330 2600 640 6100 

Chemical fallow 3 450 200 na 401 99 940 

200 460 110 901 220 2100 

1.4 450 440 na 858 210 2000 

200 990 240 1931 480 4500 

CRP or grasslands 2 450 310 na 601 150 1400 

200 690 170 1352 330 3200 

Corn Sorghum 

2 450 310 na 601 150 1400 

200 690 170 1352 330 3200 

1 450 610 na 1202 300 2800 

200 1400 340 2704 670 6400 

Roadsides 2 40 3500 850 6759 1700 16,0

1 40 6900 1700 13519 3300 32,0

Sod farms 4(FL) 80 860 210 1690 420 4000 

2 80 1700 430 3380 840 8000 

47
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

(6) Applying liquids with a right of way sprayer 

Roadsides 

2 40 67 16 300 74 not f1 40 130 33 601 150 not f

(8) Applying impregnated fertilizer with a tractor-drawn spreader 

Corn Sorghum 

2 320 190 na 660 na 1000 

160 380 na 1300 na 1900 

1 320 380 na 1300 na 1900 

160 900 na 2600 na 4000 

(9) Applying granular product with a tractordrawn spreader 

On-farm fertilizer for corn, sorghum 

2 200 610 150 2221 550 3200 

80 1500 380 5553 1400 7900 

1 200 1200 300 4442 1100 6400 

80 3000 750 11,100 2700 16,0

Flagger 

(15) Flagging sprays 

Conifer forest Christmas tree farms 

4 350 310 76 466 120 910 

Sugarcane 4 350 310 76 466 120 910 

2.6 350 480 120 717 180 1400 

Chemical fallow 3 350 410 100 621 150 1200 

1.4 350 880 220 1331 330 2600 

CRP or grasslands 2 350 620 150 931 230 1800 Corn Sorghum 

2 350 620 150 931 230 1800 1 350 1200 310 1863 460 3600 

48
Scenario Crop/Use Site Rate1 Acres 

Levels of Protection 

Baseline PPE2 

Inter- Inter- 

Short Term mediate Short Term mediate Sho

Term Term 

Sod farms 4 (FL) 350 310 76 466 120 910 

2 350 620 150 931 230 1800 

1 lb ai/A or lb ai/gal 2 PPE Includes long-sleeved shirt and long pants, coveralls, chemical resistant gloves, and a respirator. 

(16a) and (16b) are listed using minimum ppe (single layer, gloves, dust/mist respirator). 

3 pounds of fertilizer treated per day 4 Scenario #5, Applying Liquids by Groundboom: the baseline assessment includes gloves. 

49
2) Lawn Care Operator Handler Risk 

The Agency has determined that there is potential for atrazine exposure to Lawn Care 

Operators (LCOs) and other handlers mixing, loading and/or applying atrazine to turf in 

accordance with the current use pattern. Fifteen major exposure scenarios have been identified 

and are listed below. 

(1b) mixing/loading liquid formulations for groundboom application, 

(1d) mixing/loading liquid formulations for lawn handgun application (LCO), 

(2b) mixing/loading dry flowable for groundboom application, 

(3) loading granular formulations, 

(5) applying liquids with groundboom sprayer, 

(7) applying with a lawn handgun or compressed air sprayer, 

(9) applying granular formulations with a tractor-drawn spreader, 

(10) mixing/loading/applying with a backpack sprayer, 

(11) mixing/loading/applying liquid formulations with a low pressure handwand, 

(12a) mixing/loading/applying liquids with a lawn handgun or compressed air sprayer, 

(12b) mixing/loading/applying WDG formulations with a lawn handgun, 

(12c) mixing/loading/applying water soluble powder formulations with a lawn handgun, 

(13) loading/applying granular formulations with a push type spreader, and 

(14) loading/applying granular formulations with a bellygrinder. 

The risk assessments for these scenarios are summarized in Table 15 below. With the 

use of PPE, all scenarios are acceptable. 

Table 15. Lawn Care Operator Margins of Exposure 

Scenario 

Crop/ 

Use 

Site 

Rate 

(lb 

ai/A) 

Acres 

Levels of Protection 

Baseline PPE ECs 

Short 

term 

Intermediate 

term 

Short 

term 

Intermediate 

term 

Short 

term 

Intermediate 

term 

Mixer/Loader 

(1b) Liquid 

formulations for 

groundboom 

application 

golf 

course 

turf 

2 40 31 8 4335 1100 9100 2300 

(1d) Liquid 

formulations for 

lawn handgun 

application 

lawn, 

golf 

courses 

2 100 12 3 1734 430 3600 900 

(2b) Dry flowable for 

groundboom 

application 

golf 

course 

turf 

2 40 1200 290 1836 450 6600 1600 

50
Scenario 

Crop/ 

Use 

Site 

Rate 

(lb 

ai/A) 

Acres 

Levels of Protection 

Baseline PPE ECs 

Short 

term 

Intermediate 

term 

Short 

term 

Intermediate 

term 

Short 

term 

Intermediate 

term 

(3) Granular 

formulations (loading) 

golf 

course 

turf 

2 40 2500 610 10,047 2500 120K 31,000 

Mixer/Loader/Applicator 

(10) Liquid via 

backpack sprayer 

lawns, 

golf 

courses 

2 5 see PPE 428 110 not feasible 

(11) Liquid via lowpressure handwand lawns, 

golf 

courses 

2 5 7 2 1549 380 not feasible 

(12a) Liquid via lawn 

handgun and 

compressed air sprayer

1 

lawns, 

golf 

courses 

2 5 see PPE 1400 

gloves 

340 

gloves 

not feasible 

(12b) WDG via lawn 

handgun1 

lawns, 

golf 

courses 

2 5 see PPE 1100 

gloves 

290 

gloves 

not feasible 

(12c) WSP via lawn 

handgun1 

lawns, 

golf 

courses 

2 5 see PPE 920 

gloves 

230 

gloves 

not feasible 

(13) Granular via push 

type spreader 

(ORETF)1 

lawns, 

golf 

courses 

2 5 1500 380 2100 

gloves 

520 

gloves 

not feasible 

(14) Granular via belly 

grinder 

lawns, 

golf 

courses 

2 1 330 82 616 150 not feasible 

Applicator 

(5) Applying liquids by 

groundboom 

golf 

course 

turf 

2 40 3500 850 6759 1700 16,000 3900 

(7) Applying liquids 

with a handgun 

(ORETF)1 

lawns, 

golf 

courses 

2 5 see PPE 980 

gloves 

240 

gloves 

not feasible 

(9) Applying granular 

formulations with a 

tractor-drawn spreader 

golf 

course 

turf 

2 40 3000 750 11,100 2700 16,000 4000 

Footnote: 

PPE for scenarios 12(a), 12(b), 12(c), 13 and 7, include baseline (long-sleeved shirt, pants, shoes and 

51 

1 
socks) plus gloves. 

3) Post-Application Occupational Risk 

Post-application exposure to workers through entry into agricultural fields treated with 

atrazine was also considered in the occupational risk assessment. These activities result in 

potential short-term exposures. All post-application risk estimates were below the Agency’s 

level of concern. MOEs ranged from 100 to 220,000. 

4) Epidemiology Data 

An epidemiology study was conducted of workers at the Syngenta St. Gabriel plant 

where atrazine is manufactured. That study reported a statistically significant increase in the 

incidence of prostate cancer among plant workers. The Agency, upon review of this study, 

requested additional information on the exposure profile of the employees diagnosed with 

prostate cancer and this information was provided and reviewed. Based on this review, it 

appears that most of the increase in prostate cancer incidence at the St. Gabriel plant is likely due 

to intensive prostate specific antigen (PSA) screening of employees conducted as part of the 

company’s “Wellness Program.” The study was insufficiently large and has limitations that 

prevent ruling out atrazine as a potential contributor to the increase observed. On balance, 

however, a role for atrazine seems unlikely because prostate cancer was found primarily in 

active employees who received intensive PSA screening; there was no increase in advanced 

tumors or mortality; and proximity to atrazine manufacturing did not appear to be correlated with 

risk. 

Atrazine has also been tied to inflammation of the prostate in laboratory animals and 

changes in testosterone levels at high doses. However, neither condition has been tied to the 

increased risk of prostate cancer and the Agency concludes the animal data do not provide 

biologically plausible evidence to support atrazine as a cause of prostate cancer. 

Other cancers besides prostate were found to have an elevated, though not statistically 

significant, increase in risk at the St. Gabriel plant. Other studies have suggested an increased 

risk for ovarian, breast, and other cancers, including non-Hodgkin’s lymphoma. However, these 

studies are at best preliminary and should not serve as a basis for implicating atrazine as a human 

carcinogen due to their methodological limitations. 

In addition, the Agency understands that Syngenta will be conducting a case control 

study on male employees at the St. Gabriel plant to examine the relationship between atrazine 

exposure estimates and the presence or absence of prostate cancer among cases and controls. 

We expect to receive and review this study during the third quarter of 2003 and to incorporate 

the results into the October revision to the IRED. 

Further, the National Cancer Institute’s (NCI) preliminary analysis of the National 

Institute of Environmental Health Sciences (NIEHS) Agricultural Health Study has found no 

association between prostate cancer and atrazine in one of the largest and best-designed 

52
epidemiological studies ever conducted. NCI expects to publish a final analysis this summer. 

The Agency will fully consider additional results from the NCI analysis when it becomes 

available. 

B. Environmental Risk Assessment 

A summary of the Agency’s environmental risk assessment is presented below. For 

detailed discussions of all aspects of the environmental risk assessment, see the April 22, 2002, 

Reregistration Eligibility Science Chapter for Atrazine - Environmental Fate and Effects Chapter 

and the “Steeger Document” available in the public docket and on the internet at 

www.epa.gov/pesticides/reregistration. There were no major revisions to the ecological risk 

assessment. 

1. Environmental Fate and Transport 

Atrazine is mobile and persistent in the environment and, as such, atrazine is expected to 

be present in surface water and groundwater. This is confirmed by widespread detection in 

surface water and groundwater. The main route of dissipation is microbial degradation under 

aerobic conditions. 

Atrazine can reach nearby non-target plants, soil, and surface water via spray drift during 

application. Atrazine is applied directly to target plants during foliar application or directly to 

soil during the more frequent pre-plant and pre-emergent applications. Atrazine can be 

transported indirectly to soil due to incomplete interception during foliar application and washoff 

subsequent to foliar application. Atrazine is unlikely to undergo rapid degradation on foliage 

because atrazine is resistant to abiotic hydrolysis (stable at pHs 5, 7, and 9), resistant to direct 

aqueous photolysis (stable under sunlight at pH 7), and is only moderately susceptible to 

degradation in soil (aerobic laboratory half-lives of 3-4 months). For aquatic environments 

reported half-lives were much longer. In an anaerobic aquatic study, atrazine’s overall half-life, 

water half-life, and sediment half-life were given as 608, 578, and 330 days, respectively. 

Atrazine is also unlikely to undergo rapid volatilization from foliage because it has a 

relatively low Henry’s Law constant (2.6 X 10-9 atm@m3/mol). But this may be offset by 

atrazine’s relatively low octanol/water coefficient (Log Kow = 2 .7), and soil/water partitioning 

coefficents (Freundlich Kads values < 3 and often < 1). In addition, atrazine has relatively low 

adsorption characteristics; this indicates that atrazine may undergo substantial washoff from 

foliage. 

In terrestrial field dissipation studies performed in Georgia, California, and Minnesota, 

atrazine dissipated with half lives of 13, 58, and 261 days, respectively. The differences between 

these reported half-lives could be attributed to the temperature variation between the studies in 

which atrazine was seen to be more persistent in colder climate. Long term field dissipation 

studies also indicated that atrazine could persist over a year in such climatic conditions. A 

forestry field dissipation study in Oregon (aerial application of 4 lb ai/A) estimated an 87 day 

half-life for atrazine on exposed soil, a 13 day half-life in foliage, and a 66 day half-life on leaf 

53
litter. 

Atrazine metabolites, desethylatrazine (DEA) and desisopropylatrazine (DIA) were 

detected in all anaerobic aquatic metabolism studies submitted, and hydroxyatrazine and 

diaminochloroatrazine (DACT) were detected in all but one of the anaerobic aquatic metabolism 

studies submitted. Desethylhydoxyatrazine (DEHA) and desisopropylhydroxyatrazine (DIHA) 

were also detected in one of the aerobic studies. All of the chlorinated metabolites and hydroxy 

compounds detected in laboratory metabolism studies were present at much less than 10% of 

applied atrazine; thus, are not considered by the Agency to be “major degradates.” 

For studies limited to several months, the relative concentrations of the metabolites in 

soil were generally as follows: DEA>DIA>DACT~hydroxyatrazine. However, for an aerobic 

soil metabolism study and an anaerobic aquatic metabolism study both lasting a year, the 

concentration of hydroxyatrazine was comparable to that of DEA over the last few months of the 

studies. In addition, some literature indicates that higher quantities of hydroxyatrazine can be 

formed in soil and in sediment under acidic conditions. Other hydroxy compounds have only 

rarely been detected in lab studies. 

The soil/water partitioning of atrazine, DEA, DIA, and DACT are relatively low as 

shown by Freundlich adsorption coefficients of < 3 and often < 1 for 4 different soils. The 

Freundlich adsorption constants for hydroxyatrazine are substantially greater, being 

approximately 2 for sand, but 6.5, 12.1, and 390 for a sandy loam, loam, and clay soil, 

respectively. No adsorption/desorption data are available for other hydroxy-triazine degradates. 

However, the higher soil/water partitioning exhibited by hydroxyatrazine compared to atrazine 

suggests that the other hydoxy-triazines are likely to exhibit higher soil/water partitioning than 

corresponding chloro-triazine degradates. 

In a limited study on atrazine and its chlorodegradates in surface water source CWS, the 

detection of all was relatively widespread. However, atrazine predominated with the relative 

order of concentrations generally being as follows: atrazine>>DEA>DIA~DACT. 

In a 1999 study of rural wells, the four hydroxy compounds were detected. 

Hydroxyatrazine was detected the most frequently and generally at the highest level, but not to 

the same extent as atrazine or the chlorinated metabolites. Unlike in surface water, where 

atrazine concentrations were generally much greater than chlorotriazine concentrations, the DEA 

and DACT concentrations in rural wells were often comparable to those of atrazine. The relative 

order of concentrations found in rural wells was generally 

atrazine~DEA~DACT>DIA>hydroxyatrazine . 

The relatively widespread detection of atrazine and various chlorinated metabolites in the 

surface water study on metabolites and in the 1999 rural well study is consistent with the 

widespread use of atrazine, the persistence of atrazine and the mobility of atrazine and its 

chlorinated metabolites. The lower frequency of detection and generally lower levels of the 

hydroxyatrazine in the rural well study is consistent with its higher soil/water partitioning than 

atrazine and the chlorinated metabolites. 

54
The available fate and ground water data indicate that hydroxy compounds are unlikely 

to significantly contaminate surface water. They are not appreciably formed in soil, and they are 

likely to exhibit higher soil/water partitioning than corresponding chlorinated metabolites. In 

addition, they were detected much less frequently and at much lower levels than the chlorinated 

metabolites in rural wells. However, hydroxyatrazine was detected at concentrations up to 6.5 

ppb in 6% of rural wells sampled. Also, there have been reported concentrations of 

hydroxyatrazine in soil sometimes approaching and possibly in some cases (e.g., acidic soils) 

exceeding that of DEA. 

Atrazine should be somewhat persistent in groundwater and in surface water with 

relatively long hydrologic residence times where advective transport is limited. The reasons for 

this are the resistence of atrazine to abiotic hydrolysis and to direct aqueous photolysis, its only 

moderately susceptibility to biodegradation, and its limited volatilization potential as indicated 

by a relatively low Henry’s Law constant. Atrazine has been observed to remain at elevated 

concentrations longer in some reservoirs than in flowing surface water or in other reservoirs with 

presumably much shorter hydrologic residence times in which advective transport greatly limits 

its persistence. 

The relatively low soil/water partitioning of atrazine and chlorinated metabolites 

indicates that their concentrations in or on suspended and bottom sediment will be in equilibrium 

with the residues in the water column. However, despite relatively low soil/water partitioning, 

limited data indicated that activated carbon can be effective in reducing atrazine and its triazine 

metabolite concentrations by several fold, depending upon the frequency and conditions of its 

use. 

Volatility as a route of field dissipation raises concerns about the atmospheric fate of 

atrazine, its aerial transport and whether aerial deposition poses the potential for risks to nontarget terrestrial plants. The potential for adverse effects on sensitive, non-target crops and 

plants from atmospheric deposition is uncertain. Atrazine has been widely detected in rainfall, 

with the highest concentrations occurring in the Midwestern corn belt during the application 

season (mid-April through mid- July). In addition, DEA and DIA were also detected in rainfall 

together with atrazine. High ratios of DEA to atrazine were attributed to atmospheric 

degradation. Mass deposition of atrazine and its metabolites is higher in the midwestern corn 

belt, and decreases with distance away from the corn belt. 

2. Risk to Terrestrial Organisms 

The Agency’s ecological risk assessment compares toxicity endpoints from ecological 

studies to estimated environmental concentrations (EECs) based on environmental fate 

characteristics and pesticide use data. To evaluate the potential risk to non-target organisms 

from the use of atrazine products, the Agency calculates a Risk Quotient (RQ) by determining 

the ratio of the EEC to the toxicity endpoint values, such as the median lethal dose (LD50) or the 

median lethal concentration (LC50). These RQ values are then compared to the Agency’s levels 

of concern (LOCs) to determine whether or not a chemical, when used as directed, has the 

potential to cause adverse effects to non-target organisms. In general, the higher the RQ, the 

55
greater the concern. When the RQ exceeds the LOC for a particular category (e.g., endangered 

species), the Agency presumes a risk of concern to that category of non-target organisms. The 

LOCs and the corresponding risk presumptions are presented in Table 16. 

Table 16. LOCs and Associated Risk Presumptions 

If... Then the Agency presumes.... 

Birds and Mammals 

Acute RQ > LOC of 0.5 acute risk 

Acute RQ > LOC of 0.2 risk that may be mitigated through restricted use classification 

Endangered Species 

Acute RQ > LOC of 0.1 

acute effects may occur in endangered species 

Chronic RQ > LOC of 1 chronic risk and chronic effects may occur in non-target organisms 

Aquatic Animals 

Acute RQ > LOC of 0.5 acute risk 

Acute RQ > LOC of 0.1 risk that may be mitigated through restricted use classification 

Endangered Species 

Acute RQ > LOC of 0.05 

acute effects may occur in endangered species 

Chronic RQ > LOC of 1 chronic risk and chronic effects may occur in non-target organisms 

Terrestrial and Semi-Aquatic Plants 

Acute RQ > LOC of 1 acute risk 

Acute RQ > LOC of 1 risk that may be mitigated through restricted use classification 

Endangered Species 

Acute RQ > LOC of 1 

acute effects may occur in endangered species 

Chronic RQ > LOC of 1 chronic risk and chronic effects may occur in non-target organisms 

a. Toxicity (Hazard) Assessment 

Atrazine is practically non-toxic to slightly toxic to birds and mammals, and relatively 

non-toxic to honey bees. 

As expected for a herbicide, atrazine is toxic to non-target plants. Terrestrial plant 

seedling germination tests indicate that cucumber is the most sensitive dicot and oats is the most 

sensitive monocot. Terrestrial plant seedling emergence tests indicate that the dicot most 

sensitive to atrazine is carrot, and the monocots most sensitive to atrazine are oats and ryegrass. 

Terrestrial plant vegetative vigor tests indicate that the most sensitive dicot is cucumber and the 

56
most sensitive monocot is onion. 

The acute and chronic toxicity values used to assess risks are presented in Tables 17 and 

18 below. 

Table 17. Summary of Toxicity Data for Terrestrial Animals 

Species 

Acute Toxicity (ppm) Chronic Toxicity (ppm) 

LD50 

Acute 

Oral 

Toxicity 

5-day 

LD50 

Subacute 

Dietary 

Toxicity 

NOAEC/ 

LOAEC Affected Endpoints 

Atrazine 

Northern bobwhite quail 

Colinus virginianus 

940 slightly 

toxic 

>5,000 practically 

non-toxic 

225/675 decreased egg 

production, increase 

in defective eggs, 

decreased embryo 

viability, decreased 

body weight 

Honey bee 

Apis meliferus 

96.69 relatively 

non-toxic 

-- -- -- --

Laboratory rat (mg/kg) 1,869 

-

3,080 

practicall 

y nontoxic 

-- -- 50 See health effects 

endpoints 

Table 18. Summary of Toxicity Data for Non-Target Terrestrial Plants 

Species 

Seedling Germination 

Toxicity 

Seedling Emergence 

Toxicity 

Vegetative Vigor 

Toxicity 

EC25/ 

EC05 Endpoint EC25/ 

NOAEC Endpoint EC25/ 

NOAEC Endpoint 

Monocots 

Oat - Avena sativa 1.8/0.12 reduction in 

radical length 

0.0004/ 

0.0025 

reduction 

in dry wt. 

2.4/2.0 reduction 

in dry wt. 

Onion - Allium cepa <4.0/<4.0 no effect 0.009/ 

0.005 

reduction 

in dry wt. 

0.61/0.5 reduction 

in dry wt. 

Dicots 

Carrot - Daucus carota <4.0/<4.0 no effect 0.003/ 

0.0025 

reduction 

in dry wt. 

1.7/2.0 reduction 

in plant 

height 

Cucumber - Cucumis sativus 0.80/0.60 reduction in 

radical length 

0.013/ 

0.005 

reduction 

in dry wt. 

0.008/ 

0.005 

reduction 

in dry 

weight 

57
b. Exposure and Risk - Birds and Mammals 

The Agency’s acute ecological risk assessment for terrestrial wildlife considers exposure 

to atrazine from the ingestion of residues on food. Terrestrial EECs were derived for the three 

major crops using the maximum labeled use rates (4 lb ai/A for sugarcane and 2 lb ai/A for corn 

and sorghum) and the highest value measured for foliar dissipation half-life from the application 

of atrazine to turf in the Southeastern United States: 17 days. Since foliar dissipation half-lives 

are used in estimating these EECs, the EECs better represent post-emergent applications than 

pre-plant and pre-emergence applications made directly to soil. 

No acute LOCs are exceeded for mammals; however, in some scenarios, restricted use 

and endangered species LOCs are exceeded. RQ values for small mammals are cited in the table 

below. Acute endangered species LOCs are exceeded for small herbivorous mammals (RQ 

range: 0.0092 - 0.13) at 1.1 and 1.2 lb ai/A. All acute avian RQs are significantly below all 

LOCs indicating that there is negligible potential for acute risks to birds 

The chronic LOC is exceeded for birds (RQ range: 0.08 - 4.3) and mammals (RQ range: 

1.6 - 96) suggesting the potential for chronic risks to mammals and birds from atrazine applied at 

typical and maximum use rates. 

It is important to consider that exposure of birds and mammals to atrazine applied as a 

pre-plant or pre-emergent herbicide is primarily a result of ingestion of earthworms and other 

soil organisms that can serve as a food source and inadvertent ingestion of soil. Methods are not 

available to determine the levels of atrazine that could occur in soil and in earthworms and other 

soil organisms that are used as food sources by birds and mammals. The resulting levels of 

atrazine in soil and soil organisms that can serve as a source of food for birds and mammals are 

expected to be considerably lower than estimated levels in plants used as food sources. As such, 

risk quotients based on EECs from maximum foliar dissipation half-life data, as presented in this 

document, are over-estimates for birds and mammals that are exposed from ingestion of soil 

organisms. 

The primary effects of concern for herbicides and wildlife are indirect. 

Table 19. Acute and Chronic Risk Quotients for Terrestrial Organisms 

Organism 

Size of 

Organism 

(grams) 

Range of EEC 

(ppm) Acute RQ Subacute 

Dietary RQ 

Chronic 

RQ 

(Repro) 

Sugarcane: 1 Preplant Aerial Application 4 lb ai/A (maximum labeled use rate) 

Mammalian Herbivores 15 60 - 960 0.031 - 0.49 -- 1.2 - 19.2 

Mammalian Insectivores 15 60 - 540 0.031 - 0.27 

Mammalian Granivores 15 60 0.0067 

58
Table 19. Acute and Chronic Risk Quotients for Terrestrial Organisms 

Organism 

Size of 

Organism 

(grams) 

Range of EEC 

(ppm) Acute RQ Subacute 

Dietary RQ 

Chronic 

RQ 

(Repro) 

Avian Species 60 - 960 -- <0.012 - <0.19 0.27 - 4.3 

Sugarcane: 1 Preplant Aerial Application 2.6 lb ai/A (typical use rate) 

Mammalian Herbivores 15 39 - 624 0.020 - 0.32 – 0.78 - 12.48 

Mammalian Insectivores 15 39 - 151 0.020 - 0.08 

Mammalian Granivores 15 39 0.0044 

Avian Species 39 - 624 -- <0.0078 ­

<0.12 

0.17 - 2.8 

Corn and Sorghum: 1 Preplant Aerial Application at 2.0 lb ai/A (maximum labeled rate) 

Mammalian Herbivores 15 30 - 480 0.015 - 0.24 -- 0.6 - 9.6 

Mammalian Insectivores 15 30 - 270 0.015 - 0.14 

Mammalian Granivores 15 30 0.34 

Avian Species 30 - 480 -- <0.0060 ­

<0.096 

0.13 - 2.1 

Corn: 1 Preplant Aerial Application at 1.1 lb ai/A (typical use rate) 

Mammalian Herbivores 15 16.5 - 264 0.0084 - 0.13 -- 0.3 - 5.28 

Mammalian Insectivores 15 16.5 - 148.5 0.0084 - 0.075 

Mammalian Granivores 15 16.5 0.0019 

Avian Species 16.5 - 264 -- <0.0033 ­

<0.053 

0.73 - 1.2 

59
Table 19. Acute and Chronic Risk Quotients for Terrestrial Organisms 

Organism 

Size of 

Organism 

(grams) 

Range of EEC 

(ppm) Acute RQ Subacute 

Dietary RQ 

Chronic 

RQ 

(Repro) 

Sorghum: 1 Preplant Aerial Application at 1.2 lb ai/A (typical use rate) 

Mammalian Herbivores 15 18 -288 0.0092 - 0.15 -- 0.36 - 5.76 

Mammalian Insectivores 15 18 - 162 0.0092 - 0.082 

Mammalian Granivores 15 18 0.0020 

Avian Species 18 - 288 -- <0.0036 ­

<0.058 

0.08 - 1.1 

c. Exposure and Risk - Terrestrial Plants 

Atrazine applications to crop and non-crop areas result in exposure to non-target plants in 

areas adjacent to treated fields via spray drift and/or runoff. The Agency’s assessment compares 

standard residue values for runoff and drift for exposure and compares these exposure values to 

toxicity data available for non-target species. Spray drift levels for ground and aerial 

applications are 1 and 5 percent, respectively. Atrazine is highly mobile in soils and has a low 

soil-water partitioning coefficient and a water solubility value of about 33 ppm. Its runoff is 

estimated at 2 percent. The scenario for plants growing in dry areas receive runoff from 1 hectare 

to 1 hectare, while a 1-hectare wet area receives runoff from 10 hectares. All plant toxicity 

values are present as pounds active ingredient per acre (lbs ai/A). The EC25 values are used to 

calculate risk quotients for the typical non-target plants and the NOAEC values are used for 

endangered and threatened plant species. Although the Agency currently only has data on crop 

species, the results are assumed to represent a range of wild plants. The assessment assumes that 

terrestrial plants living in wetter habitats are at greater risk because they are exposed to runoff 

more than drier areas. The assessment resulted in exceedences for ground and aerial applications 

of atrazine at typical and maximum labeled rates. RQs based on the maximum labeled use rate 

are presented in Table 20 below.

 RQs from three test species exceed the typical plant LOC from spray drift alone 

(cucumber, soybeans, and cabbage), 8 test species (in dry areas) or 9 test species (in wetter 

areas) exceeded the LOC from spray drift plus runoff. Both monocot and dicot species have 

exceeded the level of concern. 

Endangered species exceedences for direct effects on terrestrial plants indicate potential 

risks to endangered species. RQs from 9 test species exceeded the endangered species LOC 

from spray drift alone or from spray drift plus runoff. The level of concern for endangered 

terrestrial plant species is exceeded for both monocots and dicots. These results indicate concern 

for endangered plant species growing in areas adjacent to atrazine-treated fields from combined 

spray drift and runoff. 

60
A ground application of 2 lbs ai/A poses a diminished risk to adjacent crops compared to 

4 lb ai/A applications, but only one of these species (i.e., soybeans from spray drift) would no 

longer exceed the acute level of concern. At the typical corn use rate of 1.1 lbs ai/A, the nontarget crops at risk are cucumbers from spray drift, 7 out of 9 non-target species growing in dry 

habitats, and all 9 non-target species, if grown in semi-aquatic habitats. Risk quotients for 

endangered plant species indicate concern for endangered species growing in areas adjacent to 

atrazine-treated fields from combined spray drift and runoff. 

Table 20. Risk Quotients for Terrestrial Plants 

Crop 

4 lbs ai./A; Aerial Application 4 lbs ai./A; Ground Application 

Spray Drift 

(5%) Spray Drift + Runoff Spray Drift 

(1%) Spray Drift + Runoff 

Dry Areas Wet Areas Dry Areas Wet Areas 

Typ ES1 

Typ ES Typ ES 

Typ ES 

Typ ES Typ ES 

Carrot 0.12 0.10 83 99 230 270 0.024 0.02 40 48 280 340 

Oats 0.083 0.10 62 99 170 270 0.017 0.02 30 48 210 340 

Ryegrass <0.05 <0.05 62 50 170 140 <0.01 <0.01 30 24 210 170 

Lettuce 0.61 0.80 50 50 140 140 0.12 0.16 24 24 170 170 

Onion 0.33 0.40 28 50 76 140 0.066 0.08 13 24 93 170 

Cucumber 25 40 19 50 52 140 5.0 8.0 9.2 24 65 170 

Soybean 7.7 10 1.3 9.9 3.5 27 1.5 2.0 0.63 4.8 4.4 34 

Cabbage 14 40 18 25 49 68 2.9 8.0 8.6 12 60 84 

Tomato 0.28 0.40 7.3 25 20 68 0.056 0.08 3.5 12 25 84 

Corn <0.05 <0.05 <0.06 <0.06 <0.17 <0.17 <0.01 <0.01 <0.03 <0.03 <0.21 <0.21 

1 ES - Endangered Species; Typ. - Typical Species 

3. Risk to Aquatic Species 

To assess the risks to aquatic plants and animals from the use of atrazine, the Agency 

first conducted a screening-level RQ assessment similar to that described above for terrestrial 

organisms. This screening-level assessment was conducted only for freshwater species. The 

Agency also conducted a refined assessment to further evaluate the potential risks to aquatic 

organisms and local communities and populations. Estuarine and saltwater species were 

assessed as part of the refined assessment. 

a. Toxicity (Hazard) Assessment 

Atrazine is slightly to moderately toxic to freshwater fish and slightly to highly toxic to 

61
freshwater invertebrates. Atrazine is slightly to moderately toxic to estuarine/marine fish and 

slightly to very highly toxic to estuarine/marine invertebrates. Tables 21 and 22 summarizes the 

endpoints used in the screening-level risk assessment of aquatic animals and plants. 

Table 21. Summary of Toxicity Data for Aquatic Organisms 

Species 

Acute Toxicity (ppb) Chronic Toxicity (ppb) 

96-hr 

LC50 

Acute Toxicity NOAEC/ 

LOAEC 

Affected 

Endpoints 

Freshwater Fish 

Rainbow trout - Oncorhynchus mykiss 5,300 moderately toxic -- --

Brook trout - Salvelinus tontinalis 6,300 moderately toxic 65/120 reduced mean 

length, mean body 

weight 

Freshwater Invertebrates 

Midge - Chironomus tentans 720 highly toxic 110/230 reduction in 

pupation and adult 

emergence 

Scud - Gammarus fasciatus 5700 moderately toxic 60/140 reduction in 

development 

Mysid shrimp - Americamysis bahia 1000 highly toxic 80/190 reduction in adult 

survival 

5400 moderately toxic 

Table 22. Summary of Toxicity Data for Non-Target Aquatic Plants 

Species 

Short Term Exposure 

(10 days or less) 

Longer Term Exposure 

(>10 days) 

Concentration 

(ppb) 

Response 

Concentration 

(ppb) 

Response 

Freshwater Vascular Plants 

Duckweed - Lemna gibba 170 50% reduction in 

growth 

37 50% reductio in growth 

(LOAEC = 3.4, 19% 

reduction in growth; 

NOAEC < 3.4) 

43 50% reduction in growth 

(NOAEC = 10) 

Freshwater Non-Vascular Plants 

Chlorophyceae - Kirchneria 

subcapitata (Selenastrum 

capricornutum) 

49 50% reduction in cell 

growth (NOAEC = 

16) 

-- --

62
b. Exposure and Risk 

For the screening-level assessment, to assess potential risk to aquatic animals and plants 

in ponds, the Agency uses a computer model to predict the EECs of atrazine in water. Peak 

EECs are compared to acute toxicity endpoints to derive acute RQs. Normally, chronic RQs are 

derived using 96-hour and 21- to 90-day EECs, corresponding to the duration of the test. For 

atrazine, 21-day EECs were generally used for chronic exposures, because the difference in EEC 

values is small. To estimate chronic risk to fish, both 21-day and 90-day EECs were used. EECs 

are presented in Table 23 below. Calculated RQs of concern are summarized below and 

presented in Table 23. 

Table 23. EECs Used in the Atrazine Aquatic Risk Assessment for Ponds 

Crop Use Rates

 (lb ai/A) 

Atrazine EEC Values ppb (Fg/L) 

Peak Conc. 96-hour 

Average 

21-day 

Average 

60-day 

Average 

90-day 

Average 

Sugarcane 4.0 205 204 202 198 194 

2.6 133 133 131 129 126 

Corn 2.0 38.2 38.0 37.2 35.5 34.2 

1.1 21.0 20.9 20.5 17.7 18.8 

Sorghum 2.0 72.7 72.3 70.6 67.7 65.9 

1.2 43.6 43.4 42.4 40.6 39.5 

For the sugarcane scenarios, atrazine applied at either the 2.6 lbs/ai/A or 4.0 lbs ai/A rate 

exceeds the levels of concern for acute toxicity to aquatic plants, restricted use for aquatic 

invertebrates, and endangered species for aquatic invertebrates and aquatic vascular plants. In 

addition, the chronic LOC is exceeded for aquatic plants, fish and aquatic invertebrates resulting 

from both the maximum use rate and the typical use rate for sugarcane. 

For the 2.0 lb rate corn scenario, atrazine exceeds the levels of concern for acute toxicity 

for aquatic plants and for endangered species for aquatic invertebrates and aquatic vascular 

plants. The acute RQs for freshwater fish, and the chronic RQs for freshwater fish and aquatic 

invertebrates do not exceed levels of concern. For the 1.1 lb. rate corn scenario, atrazine 

exceeds the LOC for endangered species for aquatic vascular plants. The remaining calculated 

RQs do not exceed levels of concern. 

For the 2.0 lb rate sorghum scenario, atrazine exceeds the LOC for acute toxicity for 

aquatic plants, restricted use for aquatic invertebrates, endangered species for aquatic 

invertebrates, and aquatic vascular plant species. The levels of concern for chronic effects are 

exceeded by chronic RQs for aquatic plants, fish and aquatic invertebrates. For the 1.2 lb. Rate 

sorghum scenario, atrazine exceeds the LOC for acute toxicity for vascular plants, endangered 

species for aquatic invertebrates, and endangered species for aquatic vascular plants. The acute 

and chronic RQs for freshwater fish and aquatic invertebrates do not exceed levels of concern. 

63
Table 24. Acute and Chronic Risk Quotients for Freshwater Aquatic Species 

Organism 

Acute Chronic 

EEC 

( ppb) RQ EEC (ppb) RQ 

Sugarcane: 1 Preplant Aerial Application at 4.0 lb ai/A 

Freshwater Fish 205 0.039 194 - 202 2.9 - 3.1 

Aquatic Invertebrate 0.28 202 3.4 

Freshwater Vascular Plant 5.5 -- --

Freshwater Vascular Plant 

(NOEC)* 

>60.3 -- --

Freshwater Algae 4.2 -- --

Sugarcane: 1 Preplant Aerial Appliation at 2.6 lb ai/A 

Freshwater Fish 133 0.025 126 - 133 1.9 - 2.0 

Aquatic Invertebrate 0.18 131 2.2 

Freshwater Vascular Plant 3.6 -- --

Freshwater Vascular Plant 

(NOEC)* 

>39.1 -- --

Freshwater Algae 2.7 -- --

Corn: 1 Preplant Aerial Application at 2.0 lb ai/A 

Freshwater Fish 38.2 0.0072 34.2 - 37.2 0.53 - 0.58 

Aquatic Invertebrate 38.2 0.053 37.2 0.63 

Freshwater Vascular Plant 37.2 1.0 

Freshwater Vascular Plant 

(NOEC)* 

37.2 >11 -- --

Freshwater Algae 38.2 0.78 -- --

Corn: 1 Preplant Aerial Application at 1.1 lb ai/A 

Freshwater Fish 21.0 0.0040 18.8 - 20.5 0.29 - 0.32 

Aquatic Invertebrate 21.0 0.029 20.5 0.34 

Freshwater Vascular Plant 20.5 0.56 -- --

Freshwater Vascular Plant 

(NOEC)* 

20.5 >6.0 -- --

64
Table 24. Acute and Chronic Risk Quotients for Freshwater Aquatic Species 

Organism 

Acute Chronic 

EEC 

( ppb) RQ EEC (ppb) RQ 

Freshwater Algae 21.0 0.43 -- --

Sorghum: 1 Preplant Aerial Application at 2.0 lb ai/A 

Freshwater Fish 72.7 0.014 65.9 - 70.6 1.0 - 1.1 

Aquatic Invertebrate 72.7 0.10 70.6 1.2 

Freshwater Vascular Plant 72.7 2.0 -- --

Freshwater Vascular Plant 

(NOEC)* 

72.7 >21 -- --

Freshwater Algae 72.7 1.5 -- --

Sorghum: 1 Preplant Aerial Application at 1.2 lb ai/A 

Freshwater Fish 43.6 0.0082 39.5 - 42.4 0.61 - 0.65 

Aquatic Invertebrate 43.6 0.061 42.4 0.71 

Freshwater Vascular Plant 43.6 1.2 -- --

Freshwater Vascular Plant 

(NOEC)* 

43.6 >13 -- --

Freshwater Algae 43.6 0.89 -- --

* Endangered species RQ calculation 

In addition to the risks described above, indirect effects on fish and aquatic invertebrates 

may be severe due to the loss of up to 60 to 95 percent of the vegetative cover, which provides 

habitat to conceal young fish and aquatic invertebrates from predators. Numerous studies have 

described atrazine’s ability to inhibit photosynthesis, change community structure, and cause the 

mortality of aquatic flora at concentrations between 20 and 500 ppm. 

5. Refined Aquatic Assessment 

The refined atrazine aquatic risk assessment focuses on aquatic plants and invertebrates 

and the potential for effects on sensitive plant species to result in community-level impacts that 

affect a range of aquatic organisms. The assessment is broken down by the type of water body 

(i.e., small static fresh water bodies such as ponds, flowing fresh water such as streams and 

rivers, larger bodies of fresh water such as lakes and reservoirs, and estuarine and marine 

habitats). Exposure for these three types of aquatic environments was estimated using PRZMEXAMS modeling simulations (ponds) and monitoring data (streams, lakes and reservoirs, and 

estuarine/marine environments - refined aquatic assessment). The April 22, 2002, 

Environmental Fate and Effects Chapter presents figures that plot atrazine concentrations against 

65
exceedence probabilities to illustrate the effects that are likely or estimated to occur in these 

aquatic environments. 

The Agency’s refined aquatic risk assessment is based on ecotoxicological data, 

microcosm and mesocosm studies, and the monitoring data described above. A large number of 

laboratory, microcosm, mesocosm, and actual field studies found in the literature suggest that 

atrazine concentrations measured in the environment could reach levels that are likely to have 

negative impact on sensitive aquatic species and communities. 

Tables 25, 26 and 27 summarize the toxicological endpoints used in the refined risk 

assessment. 

Table 25. Key Endpoints for the Lentic Freshwater Environment (e.g., reservoirs, lakes). 

The Endpoints Chosen for Use in the Refined Risk Assessment are Bolded. 

Key Group of 

Non-target 

Organisms 

Type of Study Measurement Endpoint Test Organisms / 

Effect 

Assessment Endpoint 

Fish Lab Acute Fish (96-hours) LC50 = 

5,300 Fg/L 

Rainbow trout / 

Mortality 

Fish Mortality Estimated to Occur at 

5,300 Fg/L 

Lab Chronic Fish (44-weeks) 

NOAEC = 65 Fg/L; LOAEC= 

120 Fg/L; MATC= 88 Fg/L 

Brook trout / [7.2 

% red. mean 

length, 16 % red. 

mean body 

weight] 

Reduction in Fish Growth Estimated to 

Occur at 88 Fg/L 

Distribution of 

Lab Data 

10th centile value = 62 Fg/L Freshwater 

Aquatic Animal 

Chronic Data 

Fish Population Reductions Estimated 

to Occur at 62 Fg/L 

Field 

(mesocosms) 

96% Reduction in # of Young 

Fish Occurred at 20 Fg/L 

(Caused by Loss of Food and 

Habitat) 

Bluegill sunfish Fish Populations Likely to be 

Reduced at 20 Fg/L due to Loss of 

Food and Habitat 

Invertebrates Lab Acute Invertebrate (48-hour) 

LC50 = 720 Fg/L 

Midge / Mortality Invertebrate Mortality Estimated to 

Occur at 720 Fg/L 

Lab Chronic Invertebrate (48-hour) 

NOAEC = 60 Fg/L; LOAEC= 

140 Fg/L; MATC= 92 Fg/L 

Scud / [25 % red. 

in development of 

F1 to seventh 

instar] 

Reduction in Invertebrate Populations 

Estimated to Occur at 92 Fg/L 

Distribution of 

Lab Data 

10th centile value = 62 Fg/L Freshwater 

Aquatic Animal 

Chronic Data 

Reduction in Invertebrate Populations 

Estimated to Occur at 62 Fg/L 

Field 59-65% Reduction in Daphnid 

population growth occurred at 

10 Fg/L over 18-days 

Daphnids Invertebrate Populations Likely to be 

Reduced at 10 Fg/L 

Non-Vascular 

Plants 

Lab Acute Algae (1-week) EC50 = 1 

Fg/L 

Four species 

[41-93% 

reduction in 

chlorophyll 

production] 

Reduction in Primary Production 

Estimated to Occur at 1 Fg/L 

66
Key Group of 

Non-target 

Organisms 

Type of Study Measurement Endpoint Test Organisms / 

Effect 

Assessment Endpoint 

Distribution of 

Lab Data 

10th centile value = 32 Fg/L for 

acute effects on phytoplankton, 

and 2.3 Fg/L for chronic effects 

on plants 

Freshwater 

Aquatic Plant 

Data 

Acute Effects on Phytoplankton 

Estimated at 32 Fg/L and Reductions 

in Primary Production Estimated to 

Occur at 2.3 Fg/L 

Microcosm 23% Reduction in gross primary 

production 10 Fg/L (at day 2); 

recovery by day 7 

phytoplankton Reduction in Primary Production 

Estimated to Occur at 10 Fg/L 

Field 42% Reduction in 

phytoplankton biomass (at days 

2-7) occurred at 20 Fg/L 

phytoplankton Reduction in Primary Production 

Likely to Occur at 20 Fg/L 

Vascular Plants Lab Acute (14-days) EC50 = 37 Fg/L Duckweed [50% 

reduction in 

growth] 

Reduction in Macrophytes Estimated to 

Occur at 37 Fg/L 

Distribution of 

Data 

10th centile value = 18 Fg/L for 

acute effects on macrophytes, 

and 2.3 Fg/L for chronic effects 

on plants 

Freshwater 

Aquatic Plant 

Data 

Acute Effects on Macrophytes 

Estimated at 18 Fg/L and Reductions 

in Macrophyte Populations Estimated 

to Occur at 2.3 Fg/L 

Mesocosm 60% Reduction of macrophyte 

vegetation occurred at 20 Fg/L; 

by May of following year, 95% 

Reduction of macrophytes 

Macrophytes Reduction in Macrophytes (number & 

diversity) Likely to Occur at 20 Fg/L 

Table 26. Key Endpoints for the Lotic Freshwater Environment (e.g., streams). The 

Endpoints Chosen for Use in the Refined Risk Assessment are Bolded. 

Key Group of 

Non-target 

Organisms 

Type of Study Measurement Endpoint Test 

Organisms / 

Effect 

Assessment Endpoint 

Fish Lab Acute Fish (96-hours) LC50 = 

5,300 Fg/L 

Rainbow trout / 

Mortality 

Fish Mortality Estimated to Occur at 

5,300 Fg/L 

Lab Chronic Fish (44-weeks) 

NOAEC = 65 Fg/L; LOAEC= 

120 Fg/L; MATC= 88 Fg/L 

Brook trout / [7.2 

% red. mean 

length, 16 % red. 

mean body 

weight] 

Reduction in Fish Growth Estimated to 

Occur at 88 Fg/L 

Distribution of 

Lab Data 

10th centile value = 62 Fg/L Freshwater 

Aquatic Animal 

Chronic Data 

Fish Population Reductions Estimated 

to Occur at 62 Fg/L 

Invertebrates Lab Acute Invertebrate (48-hour) 

LC50 = 720 Fg/L 

Midge / Mortality Invertebrate Mortality Estimated to 

Occur at 720 Fg/L 

Lab Chronic Invertebrate (48-hour) 

NOAEC = 60 Fg/L; LOAEC= 

140 Fg/L; MATC= 92 Fg/L 

Scud / [25 % red. 

in development of 

F1 to seventh 

instar] 

Reduction in Invertebrate Populations 

Estimated to Occur at 92 Fg/L 

Distribution of 

Lab Data 

10th centile value = 62 Fg/L Freshwater 

Aquatic Animal 

Chronic Data 

Invertebrate Population Reductions 

Estimated to Occur at 62 Fg/L 

67
Key Group of 

Non-target 

Organisms 

Type of Study Measurement Endpoint Test 

Organisms / 

Effect 

Assessment Endpoint 

Outdoor Stream Significant Increase in daytime 

and nighttime invertebrate drift 

occurred at 22 Fg/L due to 

increased predation 

various species of 

stream dwelling 

invertebrates 

Invertebrate Populations Likely to be 

Reduced at 22 Fg/L 

Non-Vascular 

Plants 

Lab Acute Algae (1-week) EC50 = 1 

Fg/L 

Four species 

[41-93% 

reduction in 

chlorophyll 

production] 

Reduction in Primary Production 

Estimated to Occur at 1 Fg/L 

Distribution of 

Lab Data 

10th centile value = 32 Fg/L for 

acute effects on phytoplankton, 

and 2.3 Fg/L for chronic effects 

on plants 

Freshwater 

Aquatic Plant 

Data 

Acute Effects on Phytoplankton 

Estimated at 32 Fg/L and reductions 

in primary production estimated to 

occur at 2.3 Fg/L 

Stream (first 

order adjacent to 

corn field in 

Canada) 

79% (mean) Reduction in Total 

Phytoplankton Counts at 2.62 

Fg/L (mean; range = 0.211 ­

13.9) 

phytoplankton Reduction in Primary Production 

Likely to Occur at 2.62 (0.211 - 13.9) 

Fg/L 

Outdoor 

Artificial 

Streams 

Depression of Photosynthesis at 

10 Fg/L 

Various species of 

stream algae. 

Photosynthesis 

reduction 

measured by open 

water oxygen 

methods. 

Reduction in Primary Production 

Likely to Occur at 10 Fg/L 

Vascular Plants Lab Acute (14-days) EC50 = 37 Fg/L Duckweed [50% 

reduction in 

growth] 

Reduction in Macrophytes Estimated to 

Occur at 37 Fg/L 

Distribution of 

Lab Data 

10th centile value = 18 Fg/L for 

acute effects on macrophytes, 

and 2.3 Fg/L for chronic effects 

on plants 

Freshwater 

Aquatic Plant 

Data 

Acute Effects on Macrophytes 

Estimated at 18 Fg/L and Reductions 

in Macrophytes Estimated to Occur 

at 2.3 Fg/L 

Table 27. Key Endpoints for the Estuarine/Marine Environment (e.g., estuaries, tidal , 

marshes). Endpoints Chosen for Use in the Refined Risk Assessment are Bolded. 

Key Group of 

Non-target 

Organisms 

Type of Study Measurement Endpoint Test 

Organisms / 

Effect 

Assessment Endpoint 

Fish Lab Acute Fish (96-hours) LC50 = 

2,000 Fg/L 

Sheepshead 

minnow / 

Mortality 

Fish Mortality Estimated to Occur at 

2,000 Fg/L 

Lab Chronic Fish NOAEC = 1,900 

Fg/L; LOAEC= 3400 Fg/L; 

MATC= 2542 Fg/L 

Sheepshead 

minnow [89 % 

red. Juv. survival] 

Reduction in Fish Populations Estimated 

to Occur at 2542 Fg/L 

Distribution of 

Lab Data 

10th centile value = 23 Fg/L Saltwater Aquatic 

Animal Chronic 

Data 

Fish Population Reductions Estimated 

to Occur at 23 Fg/L 

Invertebrates Lab Acute Invertebrate LC50 = 94 

Fg/L 

Copepod (Acartia 

tonsa) 

Invertebrate Mortality Estimated to 

Occur at 94 Fg/L 

68
ute Effects on Phytoplankton Estimated at 32 Fg/L and Reductions in Primary Production Estimated to Occur at 2.3 Fg/L 

Key Group of 

Non-target 

Organisms 

Type of Study Measurement Endpoint Test 

Organisms / 

Effect 

Assessment Endpoint 

Distribution of 

Lab Data 

10th centile value = 23 Fg/L Saltwater Aquatic 

Animal Chronic 

Data 

Invertebrate Population Reductions 

Estimated to Occur at 23 Fg/L 

Lab Chronic Invertebrate NOAEC = 

80 Fg/L; LOAEC= 190 Fg/L; 

MATC= 123 Fg/L 

Mysid [37 % red. 

Adult survival] 

Reduction in Invertebrate Populations 

Estimated to Occur at 123 Fg/L 

Non-Vascular 

Plants 

Lab Acute (120-hours) Algae LC50 = 

22 Fg/L 

Algae 

(Chrysophyceae; 

Isochrysis 

galbana) 

 Algae Mortality Estimated to Occur at 

22 Fg/L 

Distribution of 

Lab Data 

10th centile value = 27 Fg/L for 

acute effects on phytoplankton, 

and 9.1 Fg/L for chronic effects 

on plants 

Saltwater Aquatic 

Plant Data

 Acute Effects on Phytoplankton 

Estimated at 27 Fg/L and Reductions 

in Primary Production Estimated to 

Occur at 9.1 Fg/L 

Vascular Plants Lab Significant reduction in dry 

weight occurred at 10 Fg/L 

(calculated MATC from 

NOAEC=7.5 and 

LOAEC=14.3) 

Sago Pondweed Reduction in Macrophytes Estimated to 

Occur at 10 Fg/L 

Distribution of 

Lab Data 

10th centile value = 9.1 Fg/L for 

chronic effects on plants 

Saltwater Aquatic 

Plant Data

 Reductions in Macrophytes 

Estimated to Occur at 9.1 Fg/L 

Microcosm 16% Reduction in Tuber 

formation; 55% Reduction in 

Biomass over reproductive 

season at 4 Fg/L 

Wild Celery 

(Vallisneria 

Americana) 

Reduction in Macrophytes Likely to 

Occur at 4 Fg/L 

a. Ponds 

Based on modeling simulations, it is possible that for months every year, atrazine 

concentrations in ponds from use on sorghum and sugarcane exceed the levels at which studies 

have shown reductions in fish and invertebrate populations, macrophytes, and primary 

production (>20ppb). For corn, modeling simulations indicate that atrazine concentrations in 

ponds exceed the levels at which studies have shown reductions in fish populations, invertebrate 

populations, macrophytes, and primary production in 70 to 83% of the years. From 70 to 75% of 

the years, atrazine concentrations in ponds from use on sugarcane exceed the levels at which 

reproduction studies have shown reductions in invertebrate populations and fish growth. For 

sorghum, the percentage of exceedences are from 2.8 and <5% of the years. 

b. Lakes and Reservoirs 

Monitoring data in lakes and reservoirs have indicated that a number of drinking water 

sites have atrazine concentrations greater than 20 ppb in the finished water. This is the level at 

which reductions in fish populations, invertebrate populations, macrophytes, and primary 

production has been observed in simulated field studies. 

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c. Streams 

The highest atrazine concentrations occur in brief pulses following rain events and are 

usually associated with the next rain event after an application. Atrazine concentrations in 

streams vary frequently, depending on usage and rainfall patterns, and vary from watershed to 

watershed, depending on the size of the watershed, the intensity of agricultural activity, and the 

flow volume and location of the watershed. 

Reductions in invertebrate populations and primary production were likely to occur in 12 

to 34% of the 129 Midwestern streams sampled following atrazine applications in 1989. In 

addition, based on simulated field testing and laboratory testing macrophytes may be reduced in 

52 to 63% of the streams sampled in the weeks following atrazine applications. Reduction in 

primary production is also possible at these levels. Later in the season, concentrations that 

would affect primary production and macrophytes were seen in only 1% of the 143 streams 

sampled. Based on sampling in 1995, reduction in invertebrate populations are primary 

production are likely to occur in 17 to 35% of the 50 Midwestern streams sampled following 

atrazine applications. In addition, based on laboratory testing, macrophytes may be reduced in 

64% of the streams sampled following atrazine applications. 

The highest pulse concentrations seen in streams exceed many of the assessment 

endpoints for non-target organisms. While the duration of these high concentrations is not likely 

to be long since pulses of runoff tend to move quickly downstream, they may last for hours, 

especially during the Spring and during runoff events when many fields in a watershed are being 

treated with atrazine around the same time. Thus, it is possible that reductions in invertebrate 

populations and primary production could occur as a result of post-application stream 

contamination from the Spring application of atrazine. The frequency of such reductions 

occurring may be low considering the frequency of the pulses above 10 ppb and depending upon 

the flow volume of each stream. The frequency of similar reductions occurring in rivers is 

probably lower than for streams since the peaks and average concentrations of atrazine are lower 

in rivers. 

Based on NAWQA monitoring data for 40 agricultural sites, 11 to 35% of the 40 sites 

exceed atrazine concentrations at which invertebrate populations and primary production occur, 

based on the maximum atrazine concentrations seen. NAWQA monitoring data, however, were 

not designed to time monitoring to correspond with atrazine treatment and may underestimate 

concentrations likely to be present in streams. 

d. Estuaries 

Based on maximum atrazine concentrations in Louisiana, 77% of the sites sampled 

exceed concentrations at which reductions in macrophytes occur. This falls to 26 to 61% for the 

mean concentration. About 30% of the sites based on maximum concentrations and about 7% 

based on mean concentrations exceed the concentrations at which reductions in fish and 

invertebrate populations occur. 

70
Maximum atrazine concentrations in the Chesapeake Bay exceed levels that are likely to 

reduce macrophytes for 8% of the site and year combinations sampled. Atrazine could be 

contributing to reductions in submerged aquatic vegetation at certain sites in the Bay. It is 

possible that atrazine and other herbicides are a source of stress to aquatic vegetation. This, 

combined with eroding sediment could negatively affect estuarine ecosystems. 

6. Risk to Endangered Species 

Endangered species LOCs are exceeded for terrestrial plants, birds and small mammals 

from the agricultural uses of atrazine. However, risks to endangered birds and mammals are not 

anticipated from the dietary residues based on the methods and timing of atrazine applications. 

The risk exceedences for endangered terrestrial plants are based on spray drift and runoff into the 

habitats for terrestrial and semi-aquatic plants. 

Endangered aquatic species LOCs are exceeded for some agricultural uses of atrazine. 

Acute risks to endangered freshwater invertebrates and aquatic vascular plants are exceeded for 

all crop uses except for the typical use rate on corn (1.1 lb ai/A.) Chronic levels of concern for 

endangered species are exceeded for fish and aquatic invertebrate reproduction for all use rates, 

except for corn and the typical use rate on sorghum. 

Atrazine was included in the formal Section 7 consultations with FWS for the 

rangeland/pastureland and the forest cluster reviews in 1984. The Biological Opinions for both 

reviews stated that these uses of atrazine would jeopardize the continued existence of over 60 

species of plants associated with rangeland and ten species of plants associated with forests. 

Atrazine was also included in the sorghum cluster review in 1983, and the Biological Opinion 

found possible jeopardy to several species of fish plus one insect (loss of habitat) and one plant 

species. 

In addition, atrazine was one of 109 active ingredients included in the reinitiated 

Biological Opinion of 1989 from the FWS. This Opinion was primarily for aquatic species. In 

this Opinion, FWS found jeopardy to nine species of freshwater fish, two freshwater crustaceans, 

four amphibians and twelve species of plants for its uses on field crops, rangeland and forests. 

FWS provided “Reasonable and Prudent Alternatives” (RPAs) for each jeopardized species and 

“Reasonable and Prudent Measures” (RPMs) for 43 non-jeopardized species to minimize 

incidental take of these latter species. These consultations and the findings expressed in the 

Opinions, however, are based on old labels and application methods, less refined risk assessment 

procedures and an older approach to consultation which is currently being revised through 

interagency collaboration. 

When the regulatory changes recommended in this IRED are implemented and the 

ecological effects and environmental fate data are submitted and accepted by the Agency, the 

Reasonable and Prudent Alternatives and Reasonable and Prudent Measures in the Biological 

Opinion(s) may need to be reassessed and modified based on the new information. 

The Agency is currently engaged in a Proactive Conservation Review with FWS and the 

71
National Marine Fisheries Service under section 7(a)(1) of the Endangered Species Act. The 

objective of this review is to clarify and develop consistent processes for endangered species risk 

assessments and consultations. Subsequent to the completion of this process, the Agency will 

reassess the potential effects of atrazine use to federally listed threatened and endangered 

species. At that time the Agency will also consider any regulatory changes recommended in the 

IRED that are being implemented. Until such time as this analysis is completed, the overall 

environmental effects mitigation strategy articulated in this document and any County Specific 

Pamphlets described in Section IV which address atrazine, will serve as interim protection 

measures to reduce the likelihood that endangered and threatened species may be exposed to 

atrazine at levels of concern. 

The potential adverse effects of atrazine on homing and reproduction in endangered 

salmon and other anadromous fish species is currently uncertain. The laboratory study of 

olfactory function in mature Atlantic salmon parr and the effect of atrazine in the range of 0.5 

Fg/L for sensing female hormones in urine and behavior to ground salmon skin is notable. This 

is so especially if the effects are significant on salmon reproduction at such a low atrazine 

concentration, because existing concentrations in streams inhabited by endangered salmonids 

may exceed this level for prolonged periods. Atrazine concentrations are likely to be their 

highest in the late spring and early summer following applications, at a time when salmon are 

returning from the ocean to spawn. It is unclear from the results of the test by Moore and 

Waring (1998) whether the effect on olfactory function is manifested in mature adult salmon and 

what effect it might have on reproduction and recruitment. These data are preliminary and 

additional studies are necessary to determine if there are adverse atrazine effects on adult salmon 

homing and adult male milt production responses to female hormones in ovulating female urine. 

Further study is also needed on whether those effects could be significant to reproduction and 

recruitment. 

7. Ecological Incident Reports 

The Agency received 109 ecological incident reports on atrazine between 1991 and 2001. 

Of the 109 incidents, thirteen are classified as “Unlikely,” 50 are listed as “Possible,” and two 

are “Unrelated.” In only one case, a 1996 cotton use in Louisiana, were casualties (fish) 

analyzed for atrazine residues. Shad and carp tested positive for atrazine, but the conclusion was 

that atrazine was unlikely to be the cause of mortality. Forty of the 109 incidents are considered 

“Probable,” and four incidents are listed as “Highly Probable.” The 4 incidents listed as “Highly 

Probable” include 3 home lawn use incidents and 1 corn use incident. The corn use incident 

reported affecting 100 bass and 100 bream resulting from a registered use. The three home lawn 

incidents were lawn applications that affected the turf itself; two were concluded to be accidental 

misuse, and the third was a registered use that affected grass and non-target plants. 

The forty “Probable” incidents include: 16 cases affecting corn; 11 affecting grass; 11 

fish kills; 1 bird kill; and affects on ornamentals, fruit trees, berries, garden, oats, vegetation 

around an atrazine/cyanazine-treated field (runoff), and greenhouse plants (pond irrigation 

water). Four “probable” incidents are classified as accidental misuse: two cases from corn use, 

pears, raspberry and oats and grass and ornamentals; and two lawn misuse cases affecting grass 

72
and bluegrass. 

Atrazine alone is not very toxic to the birds, mammals, and aquatic animals cited in most 

of these incidents. In none of these cases has evidence been provided that firmly demonstrate 

that atrazine has produced the reported effects. In many cases, the inference of these reported 

incidents to atrazine effects is likely due to the wide spread use of atrazine and the proximity of 

the atrazine application and timing to the occurrence to the incident. About 60 percent of the 

reported fish kills listed under atrazine in the incident record occur during the Spring when 

atrazine is applied, soils are saturated and heavy rainfall is frequent. Heavy runoff may carry 

atrazine, other pesticides and organic loads into surface waters. The high volume and widespread use of atrazine increases the probability of co-occurrence of fish kills with atrazine 

applications. 

8. Endocrine Disruption 

Atrazine has been associated with sub-lethal effects in aquatic organisms and amphibians 

in research presented in the open, peer-reviewed literature. These include potential effects on 

endocrine-mediated processes in frogs at ~ 0.1 Fg/L and in largemouth bass at ~ 50 Fg/L, as 

well as olfactory effects in salmon at ~ 0.5 Fg/L. In addition, some studies have been conducted 

to address this issue and found that these effects were not demonstrated. 

The Agency’s ecological risk assessment does not suggest that endocrine disruption, or 

potential effects on endocrine-mediated pathways, be regarded as an regulatory endpoint at this 

time. Nor does the Agency have evidence to state that there is no reliable evidence that atrazine 

causes endocrine effects in the environment. Based on the existing uncertainties in the available 

database, atrazine should be subject to more definitive testing once the appropriate testing 

protocols have been established. The Agency is aware that several pertinent studies are being 

performed at this time by researchers that may to reduce some of the uncertainties in 

understanding potential atrazine effects on amphibian endocrinology and reproductive and 

developmental responses. The Agency has committed to provide these studies along with other 

available studies, a summary of the available data and methodologies and various data analyses 

for an external scientific review by the Federal Insecticide, Fungicide and Rodenticide Act 

(FIFRA) Science Advisory Panel (SAP) at a public meeting which is scheduled for June, 2003. 

The Agency anticipates that the results from this SAP meeting will provide significant input to 

enable it publish an amendment to this IRED in October 2003 which will address the issue of the 

potential effects of atrazine on amphibian endocrinology and development. 

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74
IV. Interim Risk Management and Reregistration Decision 

A. Determination of Interim Reregistration Eligibility 

Section 4(g)(2)(A) of FIFRA calls for the Agency to determine whether products 

containing a specific active ingredient are eligible for reregistration after submission of the 

relevant data. The Agency has previously identified and required the submission of the generic 

data (i.e., data specific to an active ingredient) to support reregistration of products containing 

atrazine. 

The Agency has completed its assessment of the ecological and occupational risks 

associated with the use of currently registered pesticides containing the active ingredient 

atrazine, as well as an atrazine-specific dietary risk assessment and residential risk assessment 

that have not considered the cumulative effects of the triazines, as a class. The ecological 

assessment does not address the potential for effects on amphibian endocrinology and 

reproductive and developmental responses. As mentioned above, the Agency will publish an 

amendment to this IRED in October 2003 which will address the issue. Based on a review of the 

generic data, other special studies, and public comments on the Agency’s assessments, EPA has 

sufficient information on the human health and ecological effects of atrazine to make interim 

decisions as part of the tolerance reassessment process under FFDCA and reregistration under 

FIFRA, as amended by FQPA. The Agency has determined that atrazine products, based on 

currently approved labeling, pose unreasonable dietary, residential, occupational, and ecological 

risks. However, the Agency believes that these risks can be mitigated through routine changes to 

pesticide labeling and through actions designed to further prevent risks from occurring that are 

described in a Memorandum of Agreement with the registrants. Accordingly, the Agency has 

determined that the active ingredient atrazine is eligible for reregistration provided that: (i) the 

additional data needs that the Agency has identified are addressed; (ii) the risk mitigation 

measures outlined in this document are adopted, and label amendments are made to reflect these 

measures; (iii) the consideration of cumulative risk for the triazines supports a final reregistration 

eligibility decision; and (iv) the Memorandum of Agreement is implemented. Further mitigation 

measures and additional data requirements may be warranted following the completion of the 

stakeholder process outlined in this document. 

Although the Agency has not yet considered the cumulative risk for the triazines, the 

Agency is issuing this interim assessment now in order to identify risk reduction measures that 

are necessary to support the continued use of atrazine. Based on its current evaluation of 

atrazine alone, the Agency has determined that atrazine products, unless labeled and used as 

specified in this document, would present risks inconsistent with FIFRA. Accordingly, should a 

registrant fail to implement any of the risk mitigation measures identified in this document, the 

Agency may take regulatory action to address the risk concerns from use of atrazine. 

At the time that a cumulative assessment is conducted, the Agency will address any 

outstanding risk concerns. For atrazine, if all changes outlined in this document are incorporated 

into the labels and the Memorandum of Agreement is implemented, then all currently identified 

risks will be mitigated. However, because this is an interim RED, the Agency may take any 

75
necessary further actions to finalize the reregistration eligibility decision for atrazine after 

assessing the cumulative risk of the triazine class. Such an incremental approach to the 

reregistration process is consistent with the Agency’s goal of improving the transparency of the 

reregistration and tolerance reassessment processes. By evaluating each triazine in turn and 

identifying appropriate risk reduction measures, the Agency is addressing the risks from use of 

all of the triazines in as timely a manner as possible. 

Because the Agency has not yet considered cumulative risk for all of the triazines, this 

reregistration eligibility decision does not fully satisfy the reassessment of the existing atrazine 

food residue tolerances as called for by the Food Quality Protection Act (FQPA). When the 

Agency has completed the cumulative assessment, atrazine tolerances will be reassessed. At that 

time, the Agency will reassess atrazine along with the other triazine pesticides to complete the 

FQPA requirements and make a final reregistration eligibility determination for atrazine. By 

publishing this interim decision on reregistration eligibility and requesting mitigation measures 

now for the individual chemical atrazine, the Agency is not deferring or postponing FQPA 

requirements; rather, EPA is taking steps to assure that uses that exceed FIFRA’s unreasonable 

risk standard do not remain on the label longer than is necessary, pending completion of the 

cumulative assessment required under FQPA. This decision does not preclude the Agency from 

making further FQPA determinations or tolerance-related rulemakings that may be required on 

this pesticide or any other in the future. 

If the Agency determines, before finalization of the interim RED, that any of the 

determinations described in this interim RED are no longer appropriate, the Agency will pursue 

appropriate action, including, but not limited to, reconsideration of any portion of this interim 

RED. 

Label changes that are necessary to adequately mitigate the risks of atrazine use are 

described in Section V of this document. Appendix A summarizes the uses of atrazine that are 

eligible for reregistration. Appendix B identifies the generic data requirements that the Agency 

reviewed as part of its determination of reregistration eligibility, and lists the submitted studies 

that the Agency found acceptable. 

B. Summary of Phase 5 Comments and Responses 

When making its interim reregistration decision, the Agency took into account all 

comments received during Phases 3, 4, and 5 of the Public Participation Process for atrazine. 

These comments are available in the docket in their entirety. Numerous letters were received 

commenting on the atrazine risk assessments during Phase 5 of the public process. Comments 

that addressed human health and ecological concerns were received from the technical 

registrants (Syngenta Crop Protection, Inc., and Sipcam Agro USA); state and other regulatory 

agencies (California Department of Pesticide Regulation, California Regional Water Quality 

Control Board, State of New York Office of the Attorney General, Connecticut Office of the 

Attorney General,U.S. Department of the Interior, Fish and Wildlife Service); environmental and 

advocacy groups (Natural Resources Defense Council [NRDC], People for the Ethical Treatment 

of Animals, Beyond Pesticides/NCAMP, Center for Regulatory Effectiveness; universities (Yale 

76
University; Texas Tech University; U.C. Berkeley); grower and agricultural advocacy groups 

(National Agricultural Aviation Association, Sugar Cane Growers Cooperative of Florida, Weed 

Science Society of America, Triazine Network, Marion County Farm Bureau, American Farm 

Bureau Federation, Illinois Farm Bureau, Louisiana Farm Bureau Federation, Ohio Farm Bureau 

Federation, Minnesota Farm Bureau); water advocacy groups (American Water Works 

Association); and many private citizens and growers. Comments were received on the following 

topics: 

• Toxicology and Mode of Action of Atrazine and Endpoints Chosen; 

• Carcinogenicity of Atrazine; 

• Ecological Risks of Atrazine; 

• Exposure to Atrazine and its Degradates; 

• Other Atrazine Regulations; 

• Occupational and Residential Exposure to and Risk from Atrazine; 

• Atrazine Treatment Costs; and 

• Benefits of the Use of Atrazine. 

These comments have been addressed and the assessments refined as appropriate by the 

Agency. Response to Comments documents addressing most of these comments are available in 

the public docket and on the Agency’s web page at http://www.epa.gov/pesticides/reregistration. 

Three comments that were received are being addressed in the IRED, as follows: 

comments from the The New York State Office of the Attorney General (NYOAG) on the 

Endangered Species Act (ESA) and consultations with the U.S. Fish and Wildlife Service 

(FWS); comments from the Natural Resources Defense Council (NRDC) on the consideration of 

farm worker children in the assessment; and comments from the Center for Regulatory 

Effectiveness on the new Data Quality Act (DQA) 

Comment: The NYOAG commented to the Agency that EPA must initiate consultations with 

the FWS because EPA’s issuance of a reregistration decision for atrazine triggers 

the ESA consultation requirement and stated that the ESA requires that the 

Agency consider any existing FWS biological opinion. 

Response: Atrazine has been reviewed on several occasions by the FWS as described in 

Section III above under the discussion on endangered species. Currently, the 

Agency is developing a proposal to implement its Endangered Species Protection 

Program (ESPP). The Agency is soliciting public opinion on this proposal 

through issuance of a Federal Register Notice, Endangered Species Protection 

Program Field Implementation, December 2, 2002. The Agency obtained input 

on several key aspects of the program in a workshop held in September 2002 that 

included the pesticide industry, pesticide user groups, and environmental 

advocacy organizations. An Advance Notice of Proposal Rulemaking (ANPR), 

Endangered Species and Pesticide Regulation, was issued jointly by the Agency, 

the Department of Interior and the Department of Commerce on January 24, 2003. 

The ANPR is soliciting comments regarding methods to make the consultation 

77
process more efficient. 

Comment: The Center for Regulatory Effectiveness commented on November 25, 2002, 

requesting correction under the Environmental Protection Agency’s (EPA) 

Information Quality Guidelines. This Request for Correction was filed on behalf 

of the Kansas Corn Growers Association, the Triazine Network, and the Center 

for Regulatory Effectiveness. The complaint alleges that the April 22, 2002, 

Environmental Risk Assessment for Atrazine does not comply with the “Data 

Quality Act” because the document “states that atrazine causes endocrine effects 

in various organisms including frogs.” The comment requests that the 

environmental risk assessment be corrected to state that there is no reliable 

evidence that atrazine causes “endocrine effects” in the environment and that 

there can be no reliable, accurate or useful information regarding atrazine’s 

endocrine effects until and unless there are test methods for those effects that 

have been properly validated. 

Response: After reviewing the questions raised in the request, the Agency has decided that 

some minor clarifications of the April 2002 Environmental Risk Assessment for 

Atrazine may help to avoid any future misunderstanding of the Agency’s position 

on the environmental effects of atrazine. Any such clarifications will be included 

in a revised Environmental Risk Assessment for Atrazine. This Request for 

Correction is further addressed in the Agency’s Response to Comments document 

available in the public docket and on the Agency’s web page at 

http://www.epa.gov/pesticides/reregistration. 

The Agency is providing a 60-day public comment period on this IRED. While all 

comments are welcome, those with specific data or information bearing on the risk and benefit 

assessments are most useful. 

C. Regulatory Position 

1. FQPA Assessment 

a. “Risk Cup” Determination 

As part of the FQPA tolerance reassessment process, EPA assessed the risks associated 

with this triazine. The assessment was for this individual triazine, and does not attempt to fully 

reassess these tolerances as required under FQPA. FQPA requires the Agency to evaluate food 

tolerances on the basis of cumulative risk from substances sharing a common mechanism of 

toxicity, such as the toxicity expressed by the triazine pesticides through a common biochemical 

interaction. The Agency will evaluate the cumulative risk posed by the entire class of triazines 

once the policy concerning cumulative assessments is fully resolved. 

EPA has determined that risk from exposure to atrazine exceeds its own “risk cup” for 

the currently registered uses of atrazine. In reaching this determination, EPA has considered the 

78
available information on the special sensitivity of infants and children, as well as dietary (food 

and drinking water) and residential exposure to atrazine. However, if the use of atrazine is 

modified, the Memorandum of Agreement is implemented, and any other mitigation measures 

outlined in this document are implemented, the Agency believes that risks from the use of 

atrazine will not exceed the Agency’s level of concern (i.e., atrazine uses will “fit” within its risk 

cup). Therefore, the atrazine tolerances can remain in effect until a full reassessment of the 

cumulative risk from all triazines is completed. 

b. Tolerance Summary 

Tolerances for residues of atrazine per se are established under 40 CFR §180.220(a)(1). 

Tolerances for atrazine and its chlorinated metabolites are established under 40 CFR 

§180.220(a)(2). 

The Agency has determined that the tolerance expression in 40 CFR §180.220(a)(1) 

must be changed to reflect the combined residues of atrazine and its chlorinated metabolites, and 

that all tolerances based on atrazine and its chlorinated metabolites should be placed together 

under 40 CFR § 180.220 (a)(1). A summary of atrazine tolerance reassessments is presented in 

Table 28. Reassessments are based on tolerances redefined as atrazine and its chlorinated 

metabolites. 

The Agency has also determined that tolerance expressions for the combined residues of 

each of the four hydroxy compounds are not needed. 

The Agency will commence proceedings to revoke and modify existing tolerances, and to 

correct commodity definitions. The establishment of a new tolerance or raising tolerances will 

be deferred, pending consideration of cumulative risk for the triazines. “Reassessed” does not 

imply that all of the tolerances have been fully reassessed as required by FQPA, since these 

tolerances may only be fully reassessed once the cumulative risk assessment of all triazine 

pesticides is considered, as required by the statute. Rather, this IRED provides reassessed 

tolerances for atrazine in/on various commodities, supported by all the submitted residue data, 

only for atrazine. EPA will finalize these tolerances after considering the cumulative risks for all 

triazine pesticides. The Agency’s tolerance summary is provided in Table 28. 

Tolerances Listed Under 40 CFR §180.220(a)(1) 

Tolerances for residues in/on sweet corn forage and fodder can be lowered to 4.0 ppm 

and 2.0 ppm, respectively, to 1.5 ppm for field/pop corn forages, and to 0.5 ppm for field/pop 

corn fodder and the designation “fodder” should be revised to “stover.” The tolerances for 

residues in/on corn, fresh, K+CWHR and corn grain can be decreased to 0.20 ppm, each based 

on combined nondetectable residues at 0.05 ppm for atrazine and each chloro-metabolite. The 

tolerance for residues in/on macadamia nuts can be lowered to 0.20 ppm based on combined 

nondetectable residues at 0.05 ppm for atrazine and each chloro-metabolite. Tolerances for 

residues in/on sorghum forage and fodder can be lowered to 0.50 ppm, each; the designation 

“fodder” should be revised to “stover.” The tolerance for residues in/on sorghum grain can be 

79
lowered to 0.20 ppm based on combined nondetectable residues at 0.05 ppm for atrazine and 

each chloro-metabolite. The tolerances for residues in/on wheat fodder, grain, and straw can be 

lowered to 1.5, 0.10, and 0.50 ppm, respectively; the designation “fodder” should be revised to 

“forage.” The tolerance for sugar cane can be lowered to 0.20 ppm based on combined 

nondetectable residues at 0.05 ppm for atrazine and each chlorinated metabolite. The tolerances 

for residues in/on sugarcane, forage and fodder, should be revoked, as these are no longer 

regulated as livestock feed items. The tolerance for residues in/on guavas is adequate. 

Existing tolerances for residues in commodities from cattle, goats, horses, and sheep 

(0.02 ppm) must be increased to 0.10 ppm include combined residues of atrazine and chlorinated 

metabolites. Tolerances have been reassessed based on animal feeding study data. 

The tolerances for commodities from hogs, poultry, and eggs can be revoked as there is 

no reasonable expectation of finite residues. 

Syngenta proposes lowering the tolerances for sweet and field corn forages to 1.5 ppm, 

and the tolerance for sorghum forage to 0.25 ppm. For postemergent treatments, the registrant 

proposes a change from a 30-day PHI to a 45-day PHI for sweet corn and sorghum forages, and 

from a 30-day PHI to a 60-day PHI for field corn forage. For preemergent treatments on 

sorghum, they propose a change from a 45-day PHI to a 60-day PHI. Preemergent treatments on 

sweet and field corn will retain the existing 45-day and 60-day PHI, respectively. Existing labels 

contain 21 and 30-day PHIs for corn and sorghum forages. 

The Agency has reassessed the tolerance for sweet corn forages at 4.0 ppm based on field 

trial data showing the highest chlorotriazine residues detected at 3.2 ppm after one treatment, and 

a 30-day PHI. Syngenta states that a sweet corn forage tolerance of 1.5 ppm is supported by data 

representing a 45-day PHI. Maximum chlorotriazine residues on sweet corn forage harvested 45 

days after postemergent treatments at the 1X rate expected to result in the highest residues (0.5 + 

2.0 lbs ai/A) were approximately 1.15 ppm. The Agency concludes that if labels for 

postemergent sweet corn use are amended to allow a minimum PHI of 45 days, the tolerance for 

sweet corn forage be lowered to 1.5 ppm. 

The Agency has already reassessed the tolerance for field corn forage at 1.5 ppm based 

on the highest chlorotriazine residues detected at 1.1 ppm after a 1X treatment, at either a 30-day 

or a 60-day PHI. Maximum chlorotriazine residues on field corn forage harvested 60 days after 

postemergent treatments at the 1X rate expected to result in the highest residues (0.5 + 2.0 lbs 

ai/A) were approximately 1.11 ppm. The Agency concludes that all atrazine labels for 

postemergent field corn should be amended to allow a minimum PHI of 60 days. 

The tolerance for sorghum forage has already been reassessed at 0.5 ppm based on field 

trial data showing the highest chlorotriazine residues detected at 0.22 ppm after a 1X treatment, 

and a 23-day PHI. Maximum chlorotriazine residues on sorghum forage harvested 30 and 45 

days after postemergent treatments at the 1X rate were approximately 0.35 ppm and 0.09 ppm, 

respectively. Maximum chlorotriazine residues on sorghum forage harvested 45 and 60 days 

after preemergent treatments at the 1X rate were approximately 0.12 and 0.16 ppm, respectively. 

80
The Agency concludes that if all atrazine labels for postemergent sorghum use are amended to 

allow a minimum PHI of 45 days, and for preemergent sorghum use to allow a minimum PHI of 

60 days, the tolerance for sorghum forage be lowered to 0.25 ppm. 

The Agency has recalculated the maximum theoretical dietary burden (MTDB) for dairy 

cattle based on a reassessed sweet corn forage tolerance of 1.5 ppm. The resulting MTDB for 

dairy cattle is approximately 2.0 ppm chlorotriazines. Extrapolating the results from cattle 

feeding studies to this MTDB results in a reassessed milk tolerance of 0.03 ppm. If all atrazine 

labels are amended to the proposed PHIs discussed above for sweet and field corn forage and 

sorghum forage, the milk tolerance can be lowered to 0.03 ppm, based on available feeding 

studies and residue data. 

Tolerances Needed Under 40 CFR §180.220(a)(1) 

The Agency proposes establishing a tolerance for residues of atrazine and the chlorinated 

metabolites in wheat hay based on existing wheat forage residue data, and taking into account 

any concentration of residues during drying processes for hay. Alternatively, the registrant may 

submit field trials to determine an appropriate tolerance level for residues in/on wheat hay. 

An additional processing study is required for sugarcane, in order to determine the need 

for a separate tolerance for residues in molasses. 

Tolerances Currently Listed Under 40 CFR §180.220(a)(2) To Be Placed Under 40 CFR 

§180.220(a)(1) 

The Agency recommends that the established tolerances for residues of atrazine in or on 

orchard grass and orchard grass, hay be revoked, as these uses are not being supported. 

The Agency also recommends the revocation of the 15 ppm tolerance for Perennial rye grass and 

that the use be cancelled. In addition, the tolerance for Grass, range should be revoked and a 

crop group tolerance for Crop Group 17 (Grass, Forage, Fodder, and Hay) should be established 

under 180.220(a)(1), that will cover range grasses. Residue data on representative grasses to 

support the crop group tolerance are recommended. This will include residue data on bermuda 

grass, bluegrass, and bromegrass or fescue from 12 trials (four for each cultivar) conducted in 

concordance with the current label rates. If the registrant(s) do not wish to support a crop group 

tolerance with new residue data, the existing tolerances should be revoked and the uses 

cancelled. 

Table 28. Tolerance Reassessment Summary for Atrazine 

Commodity Established 

Tolerance, ppm 

Reassessed 

Tolerance, ppm 

Comments 

[Correct Commodity Definition] 

Tolerances Listed Under 40 CFR §180.220(a)(1)1 

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Table 28. Tolerance Reassessment Summary for Atrazine 

Commodity Established 

Tolerance, ppm 

Reassessed 

Tolerance, ppm 

Comments 

[Correct Commodity Definition] 

Cattle, fat 0.02 0.10 Reassessed tolerances based on reassessed sweet 

corn forage tolerance of 4.0 ppm. Registrant 

recommended lowering tolerances for sweet corn 

forage to 1.5 ppm pending amendment of all 

atrazine labels for postemergent sweet corn use to 

allow a minimum PHI of 45 days. 

Cattle, mbyp 0.02 0.10 

Cattle, meat 0.02 0.10 

Corn, fodder, field 15 0.5 corn, field, stover 

Corn, fodder, pop 15 0.5 corn, pop, stover 

Corn, fodder, sweet 15 2.0 corn, fresh, stover 

Corn, forage, field 15 1.5 

Amend all atrazine labels for postemergent and 

preemergent field corn use to require a minimum 

PHI of 60-days. 

Corn, forage, pop 15 1.5 

Corn, forage, sweet 15 1.5 

Amend all atrazine labels for postemergent and 

preemergent sweet corn use to require a minimum 

PHI of 45 days. 

Corn, fresh, 

K+CWHR 0.25 0.20 

Corn, grain 0.25 0.20 

Eggs 0.02 Revoke 

The Agency concludes that there is no reasonable 

expectation of finding quantifiable atrazine 

residues in eggs or the meat, fat, or meat 

byproducts of poultry 

Goats, fat 0.02 0.10 Reassessed tolerances based on reassessed sweet 

corn forage tolerance of 4.0 ppm. Registrant 

recommended lowering tolerances for sweet corn 

forage to 1.5 ppm pending amendment of all 

atrazine labels for postemergent sweet corn use to 

allow a minimum PHI of 45 days. 

Goats, mbyp 0.02 0.10 

Goats, meat 0.02 0.10 

Guava 0.05 0.05 

Hogs, fat 0.02 Revoke No reasonable expectation of finding quantifiable 

atrazine residues in the meat, fat, or meat 

byproducts of hogs. 

Hogs, mbyp 0.02 Revoke 

Hogs, meat 0.02 Revoke 

Horses, fat 0.02 0.10 Reassessed tolerances based on reassessed sweet 

corn forage tolerance of 4.0 ppm. Registrant 

recommended lowering tolerances for sweet corn 

forage to 1.5 ppm pending amendment of all 

atrazine labels for postemergent sweet corn use to 

allow a minimum PHI of 45 days. 

Horses, mbyp 0.02 0.10 

Horses, meat 0.02 0.10 

Macadamia nuts 0.25 0.20 

Milk 0.02 0.03 

All atrazine labels must be amended to the 

proposed PHIs for sweet and field corn forage and 

sorghum forage. 

82
Table 28. Tolerance Reassessment Summary for Atrazine 

Commodity Established 

Tolerance, ppm 

Reassessed 

Tolerance, ppm 

Comments 

[Correct Commodity Definition] 

Poultry, fat 0.02 Revoke The Agency concludes that there is no reasonable 

expectation of finding quantifiable atrazine 

residues in eggs or the meat, fat, or meat 

byproducts of poultry. 

Poultry, mbyp 0.02 Revoke 

Poultry, meat 0.02 Revoke 

Rye, grasses, 

perennial 15 Revoke 

Uses are restricted to the Conservation Reserve 

Program (CRP) lands in OK, OR, NE, and TX. 

Restrictions on grazing and cutting for hay apply. 

Sheep, fat 0.02 0.10 Reassessed tolerances based on reassessed sweet 

corn forage tolerance of 4.0 ppm. Registrant 

recommended lowering tolerances for sweet corn 

forage to 1.5 ppm pending amendment of all 

atrazine labels for postemergent sweet corn use to 

allow a minimum PHI of 45 days. 

Sheep, mbyp 0.02 0.10 

Sheep, meat 0.02 0.10 

Sorghum, fodder 15 0.50 Sorghum, stover 

Sorghum, forage 15 0.25 

Amend all atrazine labels for postemergent 

sorghum use to require a minimum PHI of 45 

days, and for preemergent sorghum use to require 

a minimum PHI of 60 days. 

Sorghum, grain 0.25 0.20 

Sugarcane 0.25 0.20 

Sugarcane, fodder 0.25 Revoke Not a significant livestock feed item 

Sugarcane, forage 0.25 Revoke Not a significant livestock feed item 

Wheat, fodder 5 1.5 Wheat, forage 

Wheat, grain 0.25 0.10 

Wheat, straw 5 0.50 

Tolerances Listed Under 40 CFR §180.220(a)(2) To be Places Under 40 CFR §180.220(a)(1)1 

Grasses, 

orchardgrass 15 Revoke Uses on orchard grass are not supported by the 

basic produce 

Grasses, 

orchardgrass, hay 15 Revoke Uses on orchard grass are not supported by the 

basic producer 

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Table 28. Tolerance Reassessment Summary for Atrazine 

Commodity Established 

Tolerance, ppm 

Reassessed 

Tolerance, ppm 

Comments 

[Correct Commodity Definition] 

Grasses, range 4 TBD 

Uses are restricted to the Conservation Reserve 

Program (CRP) lands in OK, OR, NE, and TX. 

Restrictions on grazing and cutting for hay apply. 

However, these grasses may be fed during drought 

and emergencies. Registrant may establish a crop 

group tolerance under Crop Group 17. Residue 

data on representative crops are recommended. 

Once data are submitted a crop group tolerance 

should be established under 180.220(a)(1). Table 

2 of OPPTS 860.1500 Crop Field Trials calls for 

12 trials (four for each cultivar). Existing 

tolerances are believed to be unsupportable based 

on today’s data requirements. If the registrant(s) 

do not wish to support a crop group tolerance with 

new residue data, the existing tolerances will be 

revoked and the uses cancelled. 

Tolerances Needed Under 40 CFR §180.220(a)(1)1 

Sugarcane molasses none TBD2 Additional data are required to determine the need 

for a separate tolerance. 

Wheat, hay none 5 

This tolerance is based on residue data for wheat 

forage, taking into account concentration of 

residues as forage is dried to hay. Alternatively, 

the registrants may provide residue data on wheat 

hay from field trials. 

Tolerances to be Proposed Under 40 CFR §180.220(d) 

[Indirect residues in 

foliage of legume 

vegetables] 

none TBD Additional data are required to determine the need 

for indirect residue tolerance(s). 

1

Tolerances reassessed based on combined residues of atrazine, G30033, G-28279, and G-28273. 2

TBD = To be determined. Reassessment of tolerance(s) cannot be made at this time because additional data are required. 3

Tolerances based on combined residues of 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine (G-34048), 2-amino-4-hydroxy-6­

isopropylamino-s-triazine (GS-17794), 2-amino-4-hydroxy-6-ethylamino-s-triazine (GS-17792), and 2,4-diamino-6-hydroxy-striazine (GS-17791). 

3. Codex Harmonization 

The Codex Alimentarius Commission has not proposed or established maximum residue 

limits (MRLs) for residues of atrazine in/on agricultural commodities. Therefore, there are no 

issues regarding harmonization or compatibility of U.S. tolerances with Codex MRLs. 

4. Endocrine Disruptor Effects 

EPA is required under the FFDCA, as amended by FQPA, to develop a screening 

program to determine whether certain substances (including all pesticide active and other 

ingredients) “may have an effect in humans that is similar to an effect produced by a naturally 

occurring estrogen, or other such endocrine effects as the Administrator may designate." 

84
Following the recommendations of its Endocrine Disruptor Screening and Testing Advisory 

Committee (EDSTAC), EPA determined that there were scientific bases for including, as part of 

the program, the androgen and thyroid hormone systems, in addition to the estrogen hormone 

system. EPA also adopted EDSTAC’s recommendation that the Program include evaluations of 

potential effects in wildlife. For pesticide chemicals, EPA will use FIFRA and, to the extent that 

effects in wildlife may help determine whether a substance may have an effect in humans, 

FFDCA authority to require the wildlife evaluations. As the science develops and resources 

allow, screening of additional hormone systems may be added to the Endocrine Disruptor 

Screening Program (EDSP). 

When the appropriate screening and/or testing protocols being considered under the 

Agency’s EDSP have been developed, atrazine may be subjected to additional screening and/or 

testing to better characterize effects related to endocrine disruption. 

5. Labels 

A number of label amendments, in addition to the existing label requirements, are 

necessary in order for atrazine products to be eligible for reregistration. The Agency has 

determined that these measures, in addition to the existing label requirements, will adequately 

reduce risks. 

Provided the following risk management measures are incorporated in their entirety into 

labels for atrazine-containing products, the Agency finds that all currently registered uses of 

atrazine are eligible for interim reregistration, pending consideration of cumulative risks of the 

triazines. While all uses are eligible at this time, the cotton use will be phased out over five 

years. The regulatory rationale for each of the risk management measures outlined below is 

discussed immediately after this list of required risk management measures. 

a. Agricultural Use Exposure Reduction Measures 

For agricultural use, the following measures are required, in addition to the existing label 

requirements to address risks of concern. 

Dietary (Drinking Water) 

• Require the following statement: 

“ANY USE OF THIS PRODUCT IN AN AREA WHERE USE IS PROHIBITED 

IS A VIOLATION OF FEDERAL LAW. Before using this product, you must 

consult the Atrazine Watershed Information Center (AWIC) to determine whether 

the use of this product is prohibited in your watershed. AWIC can be accessed 

through [website], [mailing address] or [1-800-toll-free number]. If use of this 

product is prohibited in your watershed, you may return this product to your point 

of purchase or contact [insert name of registrant] for a refund.” 

Occupational - Agricultural Uses 

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1) Mixing/Loading Scenarios: 

a) Liquids: 

• require closed systems for mixing/loading to support aerial applications at 

greater than 3 lb ai/A 

• all mixers/loaders (including using engineering controls) must wear longsleeve shirt, long pants, shoes, socks, chemical-resistant gloves and 

chemical resistant apron 

b) Wettable Powders: 

• require water-soluble packaging for all WP formulations 

• all mixers/loaders must wear long-sleeve shirt, long pants, shoes, socks, 

chemical-resistant gloves and chemical resistant apron 

c) Dry Flowables: 

• water-soluble packaging optional 

• if in water-soluble packaging, all mixers/loaders must wear long-sleeve 

shirt, long pants, shoes, socks, chemical-resistant gloves and chemical 

resistant apron 

• if not in water-soluble packaging, mixers/loaders must wear coveralls over 

long-sleeve shirt and long pants, chemical-resistant gloves, chemicalresistant footwear, and chemical-resistant apron plus a NIOSH-approved 

dust/mist filtering respirator with any N, R, P, or HE filter. 

• if not in water-soluble packaging, aerial application is prohibited. 

d) Granular Products: 

• Loaders must wear long-sleeve shirt, long pants, shoes, and socks. 

2) Applicator and Flagger Scenarios: 

a) Pilots must use enclosed cockpits (40 CFR 170.240(d)(6)) for aerial applications. 

b) Human flaggers supporting aerial applications must used enclosed cabs (40 CFR 

170.240(d)(5)). 

c) Applicators applying sprays with motorized ground equipment (i.e., groundboom 

or rights-of-way sprayers) must wear long-sleeve shirt, long pants, shoes, socks, 

and chemical-resistant gloves. 

d) Applicators applying granular products or impregnated fertilizer must wear longsleeve shirt, long pants, shoes, and socks. 

• Restrict the impregnation of bulk fertilizer to commercial facilities 

(prohibit on-farm impregnation) 

• Restrict the impregnation of dry bulk fertilizer to 500 tons per day for no 

more than 30 days per calender year per facility 

e) Reduce the maximum application rate for handlers applying liquids with rightsof-way sprayers to 1.0 lb ai/A 

f) Reduce the maximum application rate for liquids for chemical follow to 2.25 lb 

ai/A 

g) Require a 60-day PHI for field corn forage uses 

h) Require a 45-day PHI for sweet corn forage uses 

i) Require a 60-day PHI for pre-emergent uses and a 45-day PHI for postemergent 

86
sorghum forage uses 

b. Non-Agricultural Use Exposure Reduction Measures 

1) Non-Agricultural Products including Lawns and Turf 

(not Sod Farms) 

a) Require that all wettable powder products be packaged in water soluble bags. 

b) Granular formulations: loaders, applicators, and other handlers must wear longsleeve shirt, long pants, shoes, and socks. 

c) Liquid, wettable powder, dry flowable (water-dispersible granule) formulations: 

• applicators using spray equipment mounted on their backs must wear 

coveralls worn over long sleeved shirt and long pants, chemical-resistant 

gloves and chemical-resistant footwear plus socks. 

• all other mixers, loaders, applicators, and other handlers must wear longsleeved shirt and long pants, shoes and socks, and chemical resistant 

gloves. 

• Reduce the maximum single application rate for liquid formulations on 

residential lawns and turf to 1 lb ai/A from 2 lb ai/A (liquid products 

containing >4% ai are restricted use) 

d) Require that granular lawn products be watered in 

2) Residential 

z) Restrict the application of granular lawn products when using hand-held devices 

(e.g. belly grinder) to spot applications only. 

aa) Prohibit applications of granular lawn products by hand 

bb) Reduce the maximum single application rate for liquid formulations on residential 

lawns and turf to 1 lb ai/A from 2 lb ai/A (liquid products containing >4% ai are 

restricted use) 

cc) Require that granular lawn products be watered in 

c. Label Harmonization 

As described in Section II under the discussion of the regulatory history of atrazine, a 

number of risk mitigation measures have been instituted over the years to address exposure to 

atrazine. While most product labels have adopted these measures there are some that continue to 

reflect use patterns prior to the implementation of these risk mitigation measures. The listing 

below identifies measures that are not fully implemented on all current product labels. All of 

these measures, in addition to new label requirements as defined by this IRED, are needed on 

atrazine labels in order for products to be eligible for reregistration. 

• Atrazine products containing >4% active ingredient must be classified as restricted use 

• Maximum broadcast application rates for corn and sorghum must be as follows: 

a) Where both a preemergence and a postemergence are used, the total atrazine 

87
applied in the preemergence PLUS postemergence treatment cannot exceed 2.5 lb 

ai/A/calendar year. 

b) 2.0 lb ai/A as a single preemergence application on soils that are not highly 

erodible or on highly erodible soils if at least 30% of the soil is covered with plant 

residues; or 

c) 1.6 lb ai/A as a single preemergence application on highly erodible soils if <30% 

of the surface is covered with plant residues; or 

d) 2.0 lb ai/A if only applied postemergence. 

e) For all tank mixtures and sequential treatment of products containing atrazine, the 

total lbs. a.i. of atrazine applied cannot exceed the application limits described 

above. 

• Maximum application rates per crop must be as follows (single application and annual 

maximum): 

a) Conifers 4 lb ai/A; 4 lb ai/A per year maximum 

b) Sugarcane 4 lb ai/A (single application);10 lb ai/A per year maximum 

c) Rights-of-Way/Roadsides Treatment 1 lb ai/A; 1 application per year 

d) Guava 4 lb ai/A (single application); 8 lb ai/A per year maximum 

e) Macadamia Nuts 4 lb ai/A (single application); 8 lb ai/A per year maximum 

f) Conservation Reserve Program (CRP) 2 lb ai/A 

g) Chemical Fallow 2.25 lbs ai/Aa 

• Delete all uses for total vegetation control on non-cropland areas. This does not include 

rights-of-way/roadsides or CRP 

• Prohibit use in chemigation systems 

• Prohibit use, and mixing and loading within 50 feet of all wells, including abandoned 

wells, drainage wells, and sink holes 

• Prohibit mixing and loading within 50 feet of intermittent streams and rivers, natural or 

impounded lakes and reservoirs. 

• Prohibit application within 66 feet of the points where field surface water runoff enters 

perennial or intermittent streams and rivers. If land is highly erodible, the buffer must be 

planted to the crop or seeded with grass or other suitable crop. 

• Prohibit application within 200 feet of natural or impounded lakes and reservoirs. 

• Require that one of the following restrictions be used in applying Atrazine to tiledoutletted fields containing standpipes 

a) Do not apply within 66 feet of standpipes in tile-outletted fields 

b) Apply this product to the entire tile-outletted field and immediately incorporate it 

to a depth of 2-3 inches in the entire field 

c) Apply this product to the entire tile-outletted field under a no-till practice only 

when a high crop residue management practice is practiced. High crop residue 

management is described as a crop management practice where little or no crop 

residue is removed from the field during and after crop harvest. 

D. Regulatory Rationale 

The following is a summary of the rationale for managing risks associated with the 

current uses of atrazine. The Agency has discussed these measures with the technical registrants 

88
and in all cases the registrants have agreed to the measures presented here. Where labeling 

revisions are warranted, specific language is set forth in the summary tables of Section V of this 

document. 

1. Human Health Risk Mitigation 

a. Dietary (Food) 

The acute and chronic dietary risks from atrazine residues on food are well below the 

Agency’s level of concern at the 99.9th percentile of exposure. Therefore, no mitigation 

measures are necessary at this time. 

b. Dietary (Drinking Water) 

1) Community Water Systems (CWS) 

The Agency has identified 34 surface water CWS with levels of atrazine that have 

exceeded the Agency’s current DWLOC (12.5 ppb as a 90-day average) at least once since 

frequent monitoring for atrazine began in 1993. The 12.5 DWLOC was used as a screening tool 

to identify specific CWS that were of concern to the Agency. The registrant has since added 3 

CWS to the list of CWS of concern. These 37 CWS have been targeted for intensive monitoring, 

risk mitigation, and probabilistic risk assessments. 

The 12.5 ppb DWLOC was also used as a tool to establish a trigger value based on 

SDWA compliance monitoring data by which CWS with potential high-end seasonal exposures 

could be identified in the future. The Agency considered available data from SDWA compliance 

monitoring and determined that a trigger value of 2.6 TCT provides an appropriate early 

warning. If annual average concentrations of atrazine and its chlorinated metabolites (total 

chlorotriazines - TCT) in a surface water CWS reach 2.6 ppb, this triggers weekly (during the 

use season) and biweekly (during the remainder of the year) monitoring of that CWS for TCT 

concentrations. 

The 12.5 ppb DWLOC is based on an endpoint of 1.8 mg/kg/day and a 1000 fold 

uncertainty factor. The uncertainty factor includes a 10x factor for interspecies variation; a 10x 

factor for intraspecies variability, and a 10x FQPA Safety Factor. The 10x FQPA safety factor 

was applied to account for the uncertainties associated with atrazine’s toxic effects on the 

developing child and the extent and magnitude of exposure to atrazine in drinking water. 

Community water systems found to be potentially impaired by atrazine, as predicted by 

exceedences of an annual average of 2.6 ppb based on SDWA compliance monitoring data, and 

the 37 CWS identified above will be subject to an intensive monitoring program that includes 

weekly sampling for atrazine during the use season and biweekly sampling for atrazine during 

the remainder of the year. This monitoring program will determine the maximum 90-day 

average TCT concentration with sufficient accuracy to allow removal of that portion of the 10x 

FQPA safety factor associated with residual uncertainties regarding the extent and magnitude of 

89
drinking water exposure, thereby reducing the 10x FQPA safety factor to 3x for the risk 

assessments conducted in those community water systems for which there is available, reliable 

drinking water exposure data. 

For those specific CWS undergoing or preparing to undergo intensive monitoring, 

uncertainties regarding the extent and magnitude of exposure to chlorotriazines no longer exist; 

this supports a reduction in the FQPA safety factor to 3x for those CWS. Based on this, the 

Agency has recalculated the DWLOC using a total risk assessment 300x uncertainty factor for 

those CWS currently undergoing or targeted for future intensive monitoring. For these CWS, the 

DWLOC becomes 37.5 ppb for total chlorotriazines based on an endpoint of 1.8 mg/kg/day, and 

a 300x uncertainty factor reflecting a 10x factor for interspecies variation, a 10x factor for 

intraspecies variability, and a 3x FQPA safety factor. The 3x FQPA safety factor reflects 

residual uncertainties associated with atrazine’s toxic effects on the developing child only. For 

CWS without intensive monitoring as described above, the screening level DWLOC remains 

12.5 ppb for total chlorotriazines. 

As such, the Agency is establishing 37.5 ppb TCT (as a 90-day average) as a 

performance standard that must be met in CWS that are being intensively monitored. The 

Agency believes that its usual mitigation measures for pesticide chemicals (e.g., reduction in 

label rates, labeled use restrictions, etc.) are not appropriate in the case of atrazine because of the 

nature of the chemical. Exceedences do not appear to be linked to nation-wide use practices that 

can be amended on the label. Based on atrazine monitoring data, the Agency’s risk assessment 

for atrazine has determined that drinking water risks from atrazine use are localized problems 

and, as such, lend themselves to a localized mitigation plan. In addition, this localized approach 

is consistent with the conclusions from a February 2000 FIFRA Scientific Advisory Panel 

meeting (Partial Report May 25, 2000. Report Number 2000-01). OPP’s approach is also 

consistent with the intent of the Agency’s recent January 2003 Water Quality Trading Policy that 

encourages solutions within watersheds, provides incentives and encourages actions, and 

provides flexibility to meet local challenges and accountability to ensure improvements. 

The Agency’s approach to these CWS is as follows: 

• For 2 CWS that were identified in the screening-level assessment and are of concern to 

the Agency, Shipman, IL, and Hettick, IL, the Agency understands that these CWS will 

no longer be using the reservoir that has shown unacceptable atrazine levels as a water 

source for the community in the future. 

• For 8 CWS that were identified in the screening-level assessment (see Appendix H for a 

site-specific listing), the Agency is requiring frequent monitoring data. If an exceedence 

of 37.5 is detected in raw drinking water (pre-treatment) in any of these watersheds, 

further use of atrazine will be prohibited in that watershed. 

• For all remaining CWS, the Agency is requiring frequent monitoring data if an annual 

average of 2.6 total chlorotriazines is triggered through SDWA compliance monitoring 

data. If an exceedence is detected in raw drinking water (pre-treatment) twice in any 

90
watershed, further atrazine use will be prohibited in that watershed. 

• Frequent monitoring will continue annually for five years (minimum) and may only cease 

if no 90-day rolling average exceeds the performance standard of 37.5 ppb total 

chlorotriazines during the five year period. 

Based on the monitoring programs, the registrants are being required to submit annual 

reports to the Agency that include the results of that year’s analysis. Atrazine registrants must 

notify EPA in writing of any raw water exceedance within 30 days of date of the last water 

sample included in that result. 

As part of the Agency’s mitigation program for atrazine, registrants are also being 

required to submit to the Agency written mitigation plans for the 8 CWS of concern (or any other 

CWS that has an exceedence in the future) describing mitigation measures to be implemented 

and a strategy for communication with growers within the watershed and quarterly progress 

reports describing the measures taken during that quarter in each CWS. 

An important element of the mitigation program is the ability of the Agency to quickly 

prohibit use of atrazine in watersheds that have exceeded the applicable performance standard. 

This is possible because the mitigation program includes a mechanism that does not require 

lengthy administrative proceeding before the use prohibition goes into effect. The principle 

registrants of atrazine have agreed to this measure. Without this voluntary measure, it may have 

been necessary for the Agency to seek immediate cancellation of atrazine. 

In order to implement this agreement, if the product contains directions for use other than 

for reformulation and contains greater than 4% atrazine active ingredient, the label must include 

all of the following statements: 

“ANY USE OF THIS PRODUCT IN AN AREA WHERE USE IS PROHIBITED 

IS A VIOLATION OF FEDERAL LAW. Before using this product, you must 

consult the Atrazine Watershed Information Center (AWIC) to determine whether 

the use of this product is prohibited in your watershed. AWIC can be accessed 

through [website], [mailing address] or [1-800-toll-free number]. If use of this 

product is prohibited in your watershed, you may return this product to your point 

of purchase or contact [insert name of registrant] for a refund.” 

91
The atrazine registrants will establish an Atrazine Watershed Information Center (AWIC) 

that: 

• will provide detailed information on what Watershed Areas have become subject 

to a prohibition on Atrazine use. Only information approved by EPA may be 

included in the AWIC. 

• shall be accessible to the public daily, including weekends and holidays, through 

a toll-free telephone number available 24 hours a day and seven days a week, a 

World Wide Web site, and a regular mailing address. Contact information for the 

AWIC will be included on all Atrazine product labels. 

• shall be updated to include any Watershed Areas for which use is prohibited 

• will prominently display information regarding use prohibitions in a manner that 

is simple and convenient for users to access and understand. 

This localized drinking water mitigation program will ensure that mitigation actions 

taken in watersheds of concern are providing results in raw drinking water and will prevent any 

exceedences from occurring or going undetected in the future. The Memorandum of Agreement 

with the atrazine technical registrants provides further details on this mitigation plan, including 

the specifics of the monitoring programs being established and the mechanism by which use 

prohibitions will be implemented. 

This program allows the Agency to make a safety finding because future exceedences in 

raw water trigger use prohibitions in the watershed of concern. Since this exceedence is in raw, 

not finished water, treatment of water by CWS operators to meet the MCL may prevent actual 

exposures above the Agency’s level of concern. In addition, the Agency does not expect future 

exceedences to occur because of the responsible use programs being implemented and 

coordinated by the registrants as product stewardship. The Agency feels that the risk of use 

prohibitions is a strong incentive for atrazine users and the registrants to make every effort to 

prevent exceedences. The performance standard approach makes the prevention of atrazine 

water contamination the responsibility of the user, but will not result in unacceptable risks. 

2) Rural Drinking Water Wells 

To confirm that rural drinking water wells will not have atrazine levels that exceed the 

Agency's level of concern, the Agency will be requiring that the registrant(s) develop and 

conduct a program for the monitoring of rural wells. The Agency is requiring that the registrants 

define a protocol for monitoring total chlorotriazine levels in rural wells by April 30, 2003. The 

protocol must identify the number of wells to be sampled, the frequency of monitoring, the 

duration and timing of monitoring, and the timing of submission of data. The Agency may take 

appropriate regulatory action if EPA determines that additional label restrictions for the 

protection of rural drinking water wells are necessary. 

b. Residential Risk Mitigation 

92
1) Residential Handler Risk 

Residential handler risks were considered for homeowners who mix, load, and apply 

atrazine products to home lawns. 

One residential handler risk scenario was above the Agency’s level of concern, the 

broadcast application of granular formulations with a bellygrinder. To address these concerns, 

the following risk mitigation measures are needed in order for EPA to conclude that atrazine 

products are eligible for reregistration: 

• Restrict the application of granular lawn products when using hand-held devices 

to spot applications only. 

• Prohibit applications of granular lawn products by hand. 

2) Residential Post-Application Risk 

Residential post-application risks were considered for individuals that reenter lawns and 

golf courses treated with atrazine. 

The Agency has risk concerns for incidental oral exposures in children to atrazine 

residues. For lawns treated with liquid formulations of atrazine, the Agency has concerns for 

hand-to-mouth exposures alone (MOE = 210) and for combined oral routes of exposure (handto-mouth, turfgrass & object mouthing, and ingestion of soil; MOE = 200). For lawns treated 

with granular formulations, the Agency has concerns for incidental ingestion of granules. 

To address those concerns, the risk mitigation measures listed below are necessary. 

These mitigation measures make it possible for EPA to conclude that atrazine products are 

eligible for reregistration. The mitigation measures are as follows: 

• Reduce the maximum 1 time application rate for liquid formulations on lawns and 

turf to 1 lb ai/A from 2 lb ai/A. 

• Require that granular lawn products be watered in. 

At the 1 lb ai/A rate for liquid formulations of atrazine, the short term MOE for hand-tomouth and combined incidental oral exposures becomes acceptable individually (420 and 370, 

respectively). If granular lawn products are watered in, the short-term MOE for ingestion of 

granules is no longer appropriate since the individual granules will no longer be present in the 

turf. 

c. Aggregate Risk Mitigation 

The Agency’s aggregate risk assessment for atrazine is based on exposure estimates for 

drinking water based on monitoring data and residential exposure estimates based on chemicalspecific exposure data. 

93
1) Acute Exposure 

Acute aggregate exposure estimates for atrazine are the same as those presented for acute 

drinking water risks because the Agency does not believe that high-end exposures through food, 

drinking water, and residential uses will all occur on the same day. Since acute drinking water 

risks do not exceed the Agency’s level of concern, acute aggregate risk is also acceptable, and no 

mitigation measures are necessary. 

2) Intermediate-Term and Chronic Exposure 

The aggregate risk assessment for intermediate-term and chronic exposures to atrazine 

and the chlorinated metabolites combines estimates of high-end seasonal or long-term average 

exposures to atrazine in drinking water with long-term average exposures in food. Neither 

intermediate-term nor long-term exposures are expected to occur in or around the home from 

residential uses of atrazine. Therefore, the intermediate-term and chronic aggregate risk for 

atrazine is the same as the intermediate-term and chronic drinking water risk. As such, 

mitigation measures presented above to address intermediate-term and chronic drinking water 

risk also mitigates the intermediate-term and chronic aggregate risk. No additional mitigation 

measures are needed to specifically address aggregate risk. 

3) Short-Term Aggregate Exposure 

The short-term (1-30 days) aggregate risk assessment combines short-term residential 

exposures with short-term drinking water exposures. If the short-term DWLOC is less than the 

measured average concentrations in surface water and groundwater, there is a risk of concern. 

Short-term aggregate risk estimates that include residential exposures to atrazine are only 

applicable for those regions of the United States where atrazine is used on turf, the Southeast 

(including Florida). 

For adult handlers applying granular formulations of atrazine via bellygrinder, both 

residential exposures alone and aggregate exposures are of concern. To address the residential 

concern, the Agency has concluded that the application of granular lawn products using handheld devices should be limited to spot applications only. 

For adults exposed to atrazine after it has been applied to turf or home lawns, neither 

residential exposure alone nor aggregate exposures are of concern. Therefore, no mitigation is 

needed. 

For children exposure to atrazine after it has been applied in liquid formulations to home 

lawns, aggregate exposure is of concern. Combined dermal and incidental oral exposures for 

toddlers result in a MOE of 180 for toddlers’ aggregate dermal and oral exposures, based on the 

1 lb ai/A rate necessary to address residential concerns alone. Since this is above the Agency’s 

level of concern, the short-term DWLOC is zero for aggregated exposures from liquid 

formulations across multiple exposure routes for toddlers. However, since the lawn use of 

atrazine is limited to the Southwest and Florida and the CWS of concern, with the exception of 

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Iberville, LA, are in the Midwest, it is highly unlikely that home lawn exposure will occur at the 

same time as high-end drinking water exposures. 

For children exposed to atrazine after it has been applied as a granular formulation to 

home lawns, and watered-in, aggregate exposure is not of concern. Toddlers’ risk estimates 

from combined pathways for incidental oral exposures based on granular formulations result in 

an MOE of 730 and thus do not exceed the Agency’s level of concern. Toddlers’ risk estimates 

from dermal exposures based on granular formulations also do not exceed HED’s levels of 

concern (MOE = 690 if not watered-in and 2000 if granules are watered-in immediately after 

application). For most CWS, short-term DWLOCs for toddlers’ post application aggregate 

exposures do not exceed the Agency’s level of concern for granular formulations watered-in 

after application to turf. Thus, mitigation measures required for residential concerns alone (i.e, 

requiring that granular formulations be watered-in) mitigate any aggregate post-application 

concerns. In addition, the few CWS that have 30-day average concentrations above the DWLOC 

are primarily located in the Midwest (outside of atrazine turf use areas), with the exception of 

Iberville, Louisiana. 

Further, all of the CWS with 30-day average concentrations above the DWLOC have also 

been identified under the intermediate-term drinking water risk assessment as of concern, 

including Iberville, Lousiana. As such, levels of atrazine in all of these CWS are being mitigated 

through the Agency’s localized atrazine drinking water mitigation plan described above. 

d. Occupational Risk Mitigation 

It is the Agency’s policy to mitigation occupational risks to the greatest extent necessary 

and feasible with personal protective equipment and engineering controls. In managing these 

risks, EPA must take into account the economic, social, and environmental costs and benefits of 

the pesticide’s use. A wide range of factors is considered in making risk management decisions 

for worker risks. These factors include, in addition to the calculated MOEs, incident data, the 

nature and severity of adverse effect, uncertainties in the risk assessment, the cost, availability 

and relative risk of alternatives, importance of the chemical in integrated pest management 

(IPM) programs, and other similar factors. 

Agricultural Handlers 

Several occupational handler scenarios are not of concern at baseline levels of PPE (longsleeved shirt and long pants, shoes and socks); therefore, no risk mitigation is necessary at this 

time in order for these uses to remain eligible for reregistration. These scenarios are described in 

Section III.A.4. of this document. 

For the remaining agricultural handlers scenarios, occupational risks are of concern when 

considering the use of PPE or engineering controls (the maximum feasible mitigation). To 

reduce mixer/loader and applicator risk so that atrazine products are eligible for reregistration, 

risk mitigation measures are necessary. These mitigation measures are explained in more detail 

below. 

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1) Mixing/Loading Scenarios 

Liquids: 

• require closed systems for mixing/loading to support aerial applications at 

greater than 3 lb ai/A 

• all mixers/loaders (including using engineering controls) must wear longsleeve shirt, long pants, shoes, socks, chemical-resistant gloves and 

chemical resistant apron 

Wettable Powders: 

• require water-soluble packaging for all WP formulations 

• all mixers/loaders must wear long-sleeve shirt, long pants, shoes, socks, 

chemical-resistant gloves and chemical resistant apron 

Dry Flowables: 

• water-soluble packaging optional 

• if in water-soluble packaging, all mixers/loaders must wear long-sleeve 

shirt, long pants, shoes, socks, chemical-resistant gloves and chemical 

resistant apron 

• if not in water-soluble packaging, mixers/loaders must wear coveralls over 

long-sleeve shirt and long pants, chemical-resistant gloves, chemicalresistant footwear, and chemical-resistant apron plus a NIOSH-approved 

dust/mist filtering respirator with any N, R, P, or HE filter. 

• if not in water-soluble packaging, aerial application is prohibited. 

Granular Products: 

• Loaders must wear long-sleeve shirt, long pants, shoes, and socks. 

2) Applicator and Flagger Scenarios 

• Pilots must use enclosed cockpits (40 CFR 170.240(d)(6)) for aerial 

applications. 

• Human flaggers supporting aerial applications must used enclosed cabs 

(40 CFR 170.240(d)(5)). 

• Applicators applying sprays with motorized ground equipment (i.e., 

groundboom or rights-of-way sprayers) must wear long-sleeve shirt, long 

pants, shoes, socks, and chemical-resistant gloves. 

• Applicators applying granular products or impregnated fertilizer must 

wear long-sleeve shirt, long pants, shoes, and socks. 

In Addition: 

• Restrict the impregnation of bulk fertilizer to commercial facilities 

(prohibit on-farm impregnation) 

• Restrict the impregnation of dry bulk fertilizer to 500 tons per day for no 

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more than 30 days per calender year per facility 

• Reduce the maximum application rate for handlers applying liquids with 

rights-of-way sprayers to 1.0 lb ai/A 

• Reduce the maximum application rate for liquids for chemical follow to 

2.25 lb ai/A 

• Require a 60-day PHI for field corn forage uses 

• Require a 45-day PHI for sweet corn forage uses 

• Require a 60-day PHI for preemergent uses and a 45-day PHI for 

postemergent sorghum forage uses 

3. Non-Agricultural Products including Lawns and Turf (not Sod 

Farms) 

For turf and LCO uses of atrazine, handler risks are of concern, but can be mitigated 

through the use of PPE. To reduce this risk so that atrazine turf products are eligible for 

reregistration, risk mitigation measures are necessary. These mitigation measures are explained 

in more detail below. 

• Require that all wettable powder products be packaged in water soluble 

bags. 

• Granular formulations: loaders, applicators, and other handlers must wear 

long-sleeve shirt, long pants, shoes, and socks. 

• Liquid, wettable powder, dry flowable (water-dispersible granule) 

formulations: 

- applicators using spray equipment mounted on their backs must 

wear coveralls worn over long sleeved shirt and long pants, 

chemical-resistant gloves and chemical-resistant footwear plus 

socks. 

- all other mixers, loaders, applicators, and other handlers must wear 

long-sleeved shirt and long pants, shoes and socks, and chemical 

resistant gloves. 

• Reduce the maximum single application rate for liquid formulations on 

residential lawns and turf to 1 lb ai/A from 2 lb ai/A (liquid products 

containing >4% ai are restricted use) 

• Require that granular lawn products be watered in 

Post-Application Occupational Risk 

The Agency has not identified any post-application occupational risks from atrazine. 

Therefore, no mitigation measures are needed at this time. 

2. Environmental Risk Mitigation 

The Agency has ecological risk concerns from the use of atrazine. The Agency has 

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identified the potential for community-level and population-level risk to aquatic ecosystems at 

concentrations of atrazine from 10 to 20 ppb. 

To mitigate these ecological risks to aquatic communities, the Agency is requiring that 

atrazine registrants, in consultation with EPA, develop a program under which the registrants 

monitor for atrazine concentrations and mitigate environmental exposures if EPA determines that 

mitigation is necessary. The program will focus on watershed impacts of atrazine use. 

The program will include an appropriate ecological level of concern (LOC), including for 

endangered species, identified by EPA; development of a protocol for a monitoring program that 

specifies the frequency, location, and timing of sampling, as well as an appropriate coordination 

with TMDL programs; triggers for mitigation measures; and description of mitigation measures 

that will be taken if triggers are exceeded. This monitoring and mitigation program would be 

designed, conducted and implemented on a tiered watershed level and must be consistent with 

existing state and federal water quality programs. 

The requirement that this process be established is presented in the Memorandum of 

Agreement between the Agency and the atrazine technical registrants. Per the Memorandum of 

Agreement, the Agency and the registrants must reach an agreement on the ecological 

monitoring program by April 30, 2003. If an agreement has not been reached, the Agency will 

identify any requirements the Agency deems necessary in the October 31, 2003, revision to the 

Atrazine IRED. The establishment of a process to address ecological risks on a watershed basis 

allows the Agency to conclude that atrazine products are eligible for reregistration. 

3. Other Labeling 

Other use and safety information need to be placed on the labeling of all end-use 

products containing atrazine, in addition to the mitigation measures listed above and other 

existing label requirements. For the specific labeling statements, refer to Section V of this 

document. 

The Agency reserves the right to require additional label amendment to mitigate risks 

from triazine residues. Any further amendments will be discussed in the triazine cumulative 

decision. 

a. Endangered Species Statement 

The Agency has developed the Endangered Species Protection Program to identify 

pesticides whose use may cause adverse impacts on endangered and threatened species, and to 

implement mitigation measures that address these impacts. The Endangered Species Act 

requires federal agencies to ensure that their actions are not likely to jeopardize listed species or 

adversely modify designated critical habitat. To analyze the potential of registered pesticide 

uses to affect any particular species, EPA puts basic toxicity and exposure data developed for 

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IREDs into context for individual listed species and their locations by evaluating important 

ecological parameters, pesticide use information, the geographic relationship between specific 

pesticide uses and species locations, and biological requirements and behavioral aspects of the 

particular species. This analysis will take into consideration any regulatory changes 

recommended in this IRED that are being implemented at this time. A determination that there 

is a likelihood of potential impact to a listed species may result in limitations on use of the 

pesticide, other measures to mitigate any potential impact, or consultations with the Fish and 

Wildlife Service and/or the National Marine Fisheries Service as necessary. 

The Endangered Species Protection Program as described in a Federal Register notice 

(54 FR 27984) is currently being implemented on an interim basis. As part of the interim 

program, the Agency has developed County Specific Pamphlets that articulate many of the 

specific measures outlined in the Biological Opinions issued to date. The Pamphlets are 

available for voluntary use by pesticide applicators on EPA’s website at www.epa.gov/espp. A 

final Endangered Species Protection Program, which may be altered from the interim program, is 

scheduled to be proposed for public comment in the Federal Register before the end of 2001. 

b. Spray Drift Management 

The Agency is currently working with stakeholders to develop appropriate generic label 

statements to address spray drift risk. Once this process has been completed, atrazine product 

labels will need to be revised to include this additional language. 

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V. What Registrants Need to Do 

In order to be eligible for reregistration, registrants need to implement the risk mitigation 

measures outlined in Section IV and V, which include, among other things, submission of the 

following: 

For products containing atrazine, registrants need to submit the following items for each 

product within eight months of the date of the PDCI: 

(1) an application for reregistration (EPA Form 8570-1, filled in, with a description 

on the application, such as, "Responding to Interim Reregistration Eligibility 

Decision” document); 

(2) five copies of the draft label incorporating all label amendments outlined in Table 

17 of this document; 

(3) responses to the generic and/or product specific Data Call-Ins (DCIs) as 

instructed in the enclosed DCIs; 

(4) two copies of the Confidential Statement of Formula (CSF); and 

(5) a certification with respect to data compensation requirements. 

Note that the first set of required responses for the product-specific DCI is due 90 days 

from the receipt of the DCI. The second set of required responses is due eight months from the 

date of the DCI. For questions about product reregistration and/or the product-specific DCI, 

please contact Bonnie Adler at (703) 308-8523. 

For the generic DCI, the following items are due: 

(1) DCI response form, due 90 days from the receipt of the DCI; 

(2) Registrant response form, due 90 days from the receipt of the DCI; and 

(3) the actual generic data in response to the DCI. 

A. Manufacturing Use Products 

1. Additional Generic Data Requirements 

The generic data base supporting the reregistration of atrazine for the above eligible uses 

has been reviewed and determined to be substantially complete. The following data gaps 

remain: 

Product Chemistry Data 

Product-Specific Product Chemistry data requirements have not been fulfilled (Series 

830). Please see Product-Specific Data Call-Ins. 

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Toxicology Data 

Non-Guideline Study 28-day inhalation toxicity study measuring LH surge and 

estrus cycle parameters 

Non-Guideline Study Assessment of CNS alterations after atrazine exposure 

(recommended) 

Occupational Data 

None 

Environmental Fate and Ecological Effects Data 

OPPTS 850.2100 (71-1(a)) Acute Avian Oral - Northern Quail (3 major degradates)

OPPTS 850.1075 (72-1(a)) Acute Fish Toxicity Bluegill (major degradate)

OPPTS 850.1075 (72-1(c)) Acute Fish Toxicity Rainbow Trout (major degradate)

OPPTS 850.1010 (72-2(a)) Acute Aquatic Invertebrate Toxicity (major degradate)

OPPTS 850.1025 (72-3(a)) Acute Estuarine/Marine Fish Toxicity (major degradate)

OPPTS 850.1025 (72-3(b)) Acute Estuarine/Marine Mollusk Toxicity (TGAI and

major degradate) 

OPPTS 850.1025 (72-3(c)) Acute Estuarine/Marine Shrimp Toxicity (major degradate) 

OPPTS 850.1400 (72-4(a)) Early Life-Stage Fish (Marine) (TGAI) 

OPPTS 850.1350 (72-4(b)) Life-Cycle Marine Invertebrate (TGAI) 

OPPTS 835.4300 (162-4) Aerobic Aquatic Metabolism - Lab 

OPPTS 835.1410 (163-2) Volatility (Lab) 

OPPTS 850.1950 (165-5) Accumulation in Aquatic Non-Target Organisms 

OPPTS 840.1100 (201-1) Spray Drift - Droplet Size Spectrum 

OPPTS 840.1200 (202-1) Spray Drift - Drift Field Evaluation 

OPPTS 830.7050 (NA) UV/Visible Absorption 

Residue Chemistry Data 

OPPTS 860.1380 (171-4e) Storage Stability 

OPPTS 860.1900 (165-2) Field Rotational Crop Study (in review)

OPPTS 860.1500 (171-4k) Crop Field Trials - Crop Group 17

OPPTS 860.1360 (171-4) Multi-Residue Method

Other Data Requirements 

Non-Guideline Study Rural Well Monitoring Program 

(see MOA & DCI for details) 

Non-Guideline Study Surface Water CWS Monitoring Program 

(see MOA & DCI for details) 

Non-Guideline Study Ecological Monitoring and Mitigation Program 

(see MOA & DCI for details - specifics to be negotiated) 

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2. Labeling for Manufacturing Use Products 

To remain in compliance with FIFRA, manufacturing use product (MUP) labeling should 

be revised to comply with all current EPA regulations, PR Notices and applicable policies. The 

MP labeling should bear the labeling contained in Table 17 at the end of this section. 

B. End-Use Products 

1. Additional Product-Specific Data Requirements 

Section 4(g)(2)(B) of FIFRA calls for the Agency to obtain any needed product-specific 

data regarding the pesticide after a determination of eligibility has been made. Registrants must 

review previous data submissions to ensure that they meet current EPA acceptance criteria and if 

not, commit to conduct new studies. If a registrant believes that previously submitted data meet 

current testing standards, then the study MRID numbers should be cited according to the 

instructions in the Requirement Status and Registrants Response Form provided for each 

product. 

A product-specific data call-in, outlining specific data requirements, accompanies this 

interim RED. 

2. Labeling for End-Use Products 

Labeling changes are necessary to implement the mitigation measures outlined in Section 

IV above. Specific language to incorporate these changes is specified in the Table 28 at the end 

of this section. 

C. Existing Stocks 

Registrants may generally distribute and sell products bearing old labels/labeling for 26 

months from the date of the issuance of this Interim Reregistration Eligibility Decision 

document. Persons other than the registrant may generally distribute or sell such products for 50 

months from the date of the issuance of this interim RED. However, existing stocks time frames 

will be established case-by-case, depending on the number of products involved, the number of 

label changes, and other factors. Refer to “Existing Stocks of Pesticide Products; Statement of 

Policy”; Federal Register, Volume 56, No. 123, June 26, 1991. 

The Agency has determined that registrants may not distribute or sell atrazine products 

bearing old labels/labeling after the date of cancellation or amendment unless it is for the 

purpose of relabeling in accordance with the terms of this interim RED. Persons other than the 

registrants may distribute or sell such products until October 1, 2003. Registrants and persons 

other than the registrants remain obligated to meet pre-existing label requirements and existing 

stocks requirements applicable to products they sell or distribute. In addition, EPA has agreed to 

allow the atrazine technical registrants to re-label cancelled products with new provisions or to 

create supplemental labeling that will allow distributors to provide new label language to 

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purchasers of atrazine products with labels that do not comply with this interim RED. 

D. Labeling Changes Summary Table 

In order to be eligible for reregistration, amend all product labels to incorporate the risk 

mitigation measures outlined in Section IV. Table 29 below describes how language on the 

labels should be amended. 

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Labeling Changes Summary Table 

In order to be eligible for reregistration, amend all product labels to incorporate the risk mitigation measure

The following table describes how language on the labels should be amended. 

Table 29: Summary of Labeling Changes for Atrazine 

Description Amended Labeling Language 

Manufacturing Use Products 

One of these statements may be added to a label to allow reformulation of the product for a specific use or all additional uses supported by a formulator or user group 

“Only for formulation into an herbicide for the following use(s) [fill blank only with those uses that are being supported by MP registrant].” Note: In addition to the uses previously classified as restricted use, all uses of products containing >4% active ingredient must be classified as restricted use. Uses for total vegetation control on non-cropland areas (not including rights-of-ways, roadsides, or CRprograms) are cancelled. Uses on pineapple, rangeland, and proso millet are also cancelled. Technical and end-use product labels must be revised to delete all references to and use-directions for these cancelled use patterns. “This product may be used to formulate products for specific use(s) not listed on the MP label if the formulator, user group, or grower has complied with U.S. EPA submission requirements regarding support of such use(s).” “This product may be used to formulate products for any additional use(s) not listed on the MP label if the formulator, user group, or grower has complied with U.S. EPA submission requirements regarding support of such use(s).” 

Text required from Memorandum of Agreement

 “This product may not be reformulated or repackaged into another product unless the registration of threformulated or repackaged product was either granted or amended after March 15, 2004, so as to be consistent with the terms and conditions set forth in the Atrazine January 31, 2003 Interim ReregistratioEligibility Document (IRED).” 

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Description Amended Labeling Language 

Text required from Memorandum of Agreement 

No product (other than products containing 4% or less atrazine active ingredient) may be formulated or repackaged from this product unless the formulated repackaged product bears a label including all of thfollowing statements: The following language must be prominently displayed in the DIRECTIONS FOR USE on the label: “ANY USE OF THIS PRODUCT IN AN AREA WHERE USE IS PROHIBITED IS A VIOLATION OF FEDERAL LAW. Before using this product, you must consult the Atrazine Watershed Information Center (AWIC) to determine whether the use of this product is prohibited in your watershed. AWIC cabe accessed through www.atrazine-watershed.info, or 1-866-365-3014. If use of this product is prohibited in your watershed, you may return this product to your point of purchase or contact [insert name of registrant] for a refund.” “No product containing 4% or less atrazine active ingredient may be formulated or repackaged from thproduct unless the registration of the resulting product includes the following terms and conditions: Thregistrant of this product shall immediately: i) cease all distribution and sale to any retailer or entity distributing or selling such product to any retailer located within all counties containing any portion of the Watershed Area listed in the AWIC; ii) ensure the removal of such Atrazine product from the shelvof any retailer located within all counties containing any portion of any Watershed Area listed in the AWIC; and iii) repurchase any such Atrazine product from any of the purchasers described above. In addition, such Registrant shall consult with the State(s) in which such counties are located to determine whether additional territory shall be included in the area to which these requirements will apply. If the State(s) determine that a larger area is warranted, the Registrant shall within 10 days of such determination notify the Director of EPA’s Special Review and Reregistration Division (SRRD) (7508C), Office of Pesticide Programs, of the specific boundaries within which the stop sale, removal, and repurchase shall take place.” 

Environmental Hazards “Do not discharge effluent containing this product into lakes, streams, ponds, estuaries, oceans, or othe

waters unless in accordance with the requirements of a National Pollutant Discharge Elimination System (NPDES) permit and the permitting authority has been notified in writing prior to discharge. Do not discharge effluent containing this product to sewer systems without previously notifying the local sewatreatment plant authority. For guidance, contact your State Water Board or Regional Office of the EPA

End Use Products Intended for Occupational Use (WPS and NonWPS) 

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Description Amended Labeling Language 

Restricted Use Pesticide (In addition to the uses previously restricted, all uses of products containing >4% active ingredient must be classified restricted use) 

“RESTRICTED USE PESTICIDE” “Due to ground and surface water concerns. For retail sale to and use only by certified applicators or persons under their direct supervision, and only for those uses covered by the certified applicator’s certification.” 

Text required from Memorandum of Agreement

 “ANY USE OF THIS PRODUCT IN AN AREA WHERE USE IS PROHIBITED IS A VIOLATION OF FEDERAL LAW. Before using this product, you must consult the Atrazine Watershed Information Center (AWIC) to determine whether the use of this product is prohibited in your watershed. AWIC cabe accessed through [www.atrazine-watershed.info], or [1-866-365-3014]. If use of this product is prohibited in your watershed, you may return this product to your point of purchase or contact [registrant] for a refund.” 

PPE Requirements Established by the IRED1 for liquid products that do NOT contain directions for use on lawns or other turfgrass 

“Personal Protective Equipment (PPE)” “Some materials that are chemical-resistant to this product are (registrant inserts correct chemicalresistant material). If you want more options, follow the instructions for category [registrant inserts A,B,C,D,E,F,G,or H] “on an EPA chemical-resistance category selection chart.” “Mixers, loaders, applicators, flaggers, and other handlers must wear: > Long sleeved shirt and long pants, > Chemical resistant gloves, such as (registrant insert correct chemical-resistant materials), > Shoes plus socks, and > Chemical-resistant apron, when mixing/loading, cleaning up spills, or cleaning equipment, or otherwexposed to the concentrate.” “See engineering controls for additional requirements.” 

107
Description Amended Labeling Language 

PPE Requirements Established by the IRED1 for liquid products that DO contain directions for use on lawns or other turfgrass 

“Personal Protective Equipment (PPE)”“Some materials that are chemical-resistant to this product are (registrant inserts correct chemicalresistant material). If you want more options, follow the instructions for category [registrant insertsA,B,C,D,E,F,G,or H] “on an EPA chemical-resistance category selection chart.”“Applicators using spray equipment mounted on their backs must wear:> Coveralls over long-sleeved shirt and long pants,> Chemical-resistant footwear plus socks, and> Chemical-resistant gloves, such as (registrant insert correct chemical-resistant materials).”

“Mixers, loaders, all other applicators, flaggers, and other handlers must wear:> Long sleeved shirt and long pants,> Chemical resistant gloves, such as (registrant insert correct chemical-resistant materials),> Shoes plus socks, and> Chemical-resistant apron, when mixing/loading, cleaning up spills, cleaning equipment, or otherwiseexposed to the concentrate.”“See engineering controls for additional requirements.”

108
Description Amended Labeling Language 

PPE Requirements Established by the IRED1 for wettable powder and dry flowable (water dispersible granular) formulations in water-soluble packets that do NOT contain directions for use on lawns or other turfgrass. Note: all wettable powder products with WPS uses on the label must be in water soluble packets to be eligible for reregistration. Dry flowable (water dispersible granular) formulations are not required to be in watersoluble packets. However aerial application is prohibited unless a dry flowable (water dispersible granular) formulation is packaged in water-soluble packets. 

“Personal Protective Equipment (PPE)” “Some materials that are chemical-resistant to this product are (registrant inserts correct chemicalresistant material). If you want more options, follow the instructions for category [registrant inserts A,B,C,D,E,F,G,or H] “on an EPA chemical-resistance category selection chart.” “Mixers, loaders, applicators, flaggers, and other handlers must wear: > Long sleeved shirt and long pants, > Chemical resistant gloves, such as (registrant insert correct chemical-resistant materials), > Shoes plus socks, and > Chemical-resistant apron, when mixing/loading, cleaning up spills, cleaning equipment, or otherwise exposed to the concentrate.” “See engineering controls for additional requirements.” 

109
Description Amended Labeling Language 

PPE Requirements “Personal Protective Equipment (PPE)” Established by the IRED1 for wettable powder and dry “Some materials that are chemical-resistant to this product are (registrant inserts correct chemical- flowable (water dispersible resistant material). If you want more options, follow the instructions for category [registrant inserts granular) formulations A,B,C,D,E,F,G,or H] “on an EPA chemical-resistance category selection chart.” packaged in water-soluble packets that DO contain “Applicators using spray equipment mounted on their backs must wear: directions for use on lawns > Coveralls over long-sleeved shirt and long pants, or other turfgrass. Note: all > Chemical-resistant footwear plus socks, and wettable powder products > Chemical-resistant gloves, such as (registrant insert correct chemical-resistant materials).” with WPS uses on the label must be in water soluble “Mixers, loaders, applicators, flaggers, and other handlers must wear: packets to be eligible for > Long sleeved shirt and long pants, reregistration. Dry flowable > Chemical resistant gloves, such as (registrant insert correct chemical-resistant materials), (water dispersible granular) > Shoes plus socks, and formulations are not > Chemical-resistant apron, when mixing/loading, cleaning up spills, cleaning equipment, or otherwise required to be in water- exposed to the concentrate.” soluble packets. However aerial application is “See engineering controls for additional requirements.” prohibited unless a dry flowable (water dispersible granular) formulation is packaged in water-soluble packets. 

110
Description Amended Labeling Language 

PPE Requirements Established by the IRED1 for dry flowable (water dispersible granule) products NOT packaged in water soluble packets that do NOT contain directions for use on lawns or other turfgrass.. Note: if not packaged in water-soluble packets, aerial application is prohibited. 

“Personal Protective Equipment (PPE)” “Some materials that are chemical-resistant to this product are (registrant inserts correct chemicalresistant material). If you want more options, follow the instructions for category [registrant inserts A,B,C,D,E,F,G,or H] on an EPA chemical-resistance category selection chart.” “Mixers, loaders, cleaners of equipment or spills, and other handlers exposed to the concentrate must 

wear: > Coveralls over long sleeved shirt and long pants, > Chemical-resistant gloves, such as (registrant insert correct chemical-resistant materials) 

> Chemical resistant footwear plus socks, > Chemical-resistant apron, and > A NIOSH-approved dust/mist filtering respirator with any N, R, P or HE filter or a NIOSH-approved dust/mist filtering respirator with approval number prefix TC-21C).” Applicators and all other handlers exposed to the dilute must wear: > Long sleeved shirt and long pants, > Shoes plus socks, and > Chemical resistant gloves, such as (registrant insert correct chemical-resistant materials).” “Aerial application is prohibited.” “See engineering controls for additional requirements.” 

111
Description Amended Labeling Language 

PPE Requirements Established by the IRED1 for dry flowable (water dispersable granule) products NOT packaged in water soluble packets that DO contain directions for use on lawns or other turfgrass.. Note: if not packaged in water-soluble packets, aerial application is prohibited. 

“Personal Protective Equipment (PPE)” “Some materials that are chemical-resistant to this product are” (registrant inserts correct chemicalresistant material). “If you want more options, follow the instructions for category” [registrant insert

A,B,C,D,E,F,G,or H] “on an EPA chemical-resistance category selection chart.” “Mixers, loaders, cleaners of equipment or spills, and other handlers exposed to the concentrate must 

wear: > Coveralls over long sleeved shirt and long pants, > Chemical-resistant gloves, such as (registrant insert correct chemical-resistant materials), 

> Chemical resistant footwear plus socks, > Chemical-resistant apron, and > A NIOSH-approved dust/mist filtering respirator with any N, R, P or HE filter or a NIOSH-approved dust/mist filtering respirator with approval number prefix TC-21C).” “Applicators using spray equipment mounted on their backs must wear: > Coveralls over long sleeved shirt and long pants, > Chemical-resistant gloves, such as (registrant insert correct chemical-resistant materials), and 

> Chemical resistant footwear plus socks.” “All other applicators and all other handlers exposed to the dilute must wear: > Long sleeved shirt and long pants, > Shoes plus socks, and > Chemical resistant gloves, such as (registrant insert correct chemical-resistant materials).” “Aerial application is prohibited.” “See engineering controls for additional requirements.” 

PPE Requirements Established by the IRED1 for granular products 

“Personal Protective Equipment (PPE)” “Loaders, applicators and other handlers must wear: > Long-sleeved shirt and long pants, and > Shoes plus socks.” 

112
Description Amended Labeling Language 

User Safety Requirements “Follow manufacturer's instructions for cleaning/maintaining PPE. If no such instructions for washable

exist, use detergent and hot water. Keep and wash PPE separately from other laundry.” If coveralls are specified in the handler PPE section of the label, use the following in addition to the above statement: “Discard clothing and other absorbent materials that have been drenched or heavily contaminated with this product’s concentrate. Do not reuse them.” 

Engineering Controls for liquid formulations that contain directions for use permitting aerial application. 

“Engineering Controls” “Mixers and loaders supporting aerial applications at a rate greater than 3 lbs ai/A must use a closed system that meets the requirements for dermal protection listed in the Worker Protection Standard (WPfor Agricultural Pesticides [40 CFR 170.240(d)(4) and must: -wear the personal protective equipment required for mixers and loaders, -wear protective eyewear if the system operates under pressure, and -be provided and have immediately available for use in an emergency, such as a spill or equipment breakdown: chemical resistant footwear.” “Pilots must use an enclosed cockpit in a manner that is consistent with the WPS for Agricultural Pesticides [40 CFR170.240(d)(6)]. Pilots must wear the PPE required on this labeling for applicators, however, they need not wear chemical-resistant gloves when using an enclosed cockpit.” “Flaggers supporting aerial applications must use an enclosed cab that meets the definition on the WorkProtection Standard for Agricultural Pesticides [ 40 CFR 170.240 (d)(5)] for dermal protection.” 

Engineering Controls for wettable powders and dry flowables (water dispersible granules) packaged in watersoluble packets. All wettable powders with WPS uses must be in water soluble packets to be eligible for reregistration. 

“Engineering Controls” “Water soluble packets when used correctly qualify as a closed mixing/loading system under the WorkProtection Standard for Agricultural Pesticides [40 CFR 170.240(d)(4). Mixers and loaders using watesoluble packets must: -wear the personal protective equipment required on this labeling for mixers and loaders, and -be provided and have immediately available for use in an emergency, such as a broken package, spill, equipment breakdown, chemical resistant footwear.” 

113
Description Amended Labeling Language 

Engineering Controls for wettable powders and dry flowables (water dispersible granules) packaged in watersoluble packets that contain directions for use permitting aerial application. All wettable powders with WPS uses must be in water soluble packets to be eligible for reregistration. 

“Pilots must use an enclosed cockpit in a manner that is consistent with the WPS for Agricultural Pesticides [40 CFR170.240(d)(6)]. Pilots must wear the PPE required on this labeling for applicators, however, they need not wear chemical-resistant gloves when using an enclosed cockpit.” “Flaggers supporting aerial applications must use an enclosed cab that meets the definition on the WorkProtection Standard for Agricultural Pesticides [ 40 CFR 170.240 (d)(5)] for dermal protection. 

Additional Engineering Controls Statement for all liquid, wettable powder, and dry flowable formulations. 

“When applicators use enclosed cabs in a manner that meets the requirements listed in the Worker Protection Standard (WPS) for agricultural pesticides (40 CFR 170.240(d)(5), the handler PPE requirements may be reduced or modified as specified in the WPS.” 

Engineering Controls for Granular Formulations 

Note to registrants: no engineering controls statement is needed on labels of granular formulations. 

User Safety Recommendations 

“User Safety Recommendations” “Users should wash hands before eating, drinking, chewing gum, using tobacco, or using the toilet.” “Users should remove clothing/PPE immediately if pesticide gets inside. Then wash thoroughly and puon clean clothing.” “Users should remove PPE immediately after handling this product. Wash the outside of gloves before removing. As soon as possible, wash thoroughly and change into clean clothing.” 

114
Description Amended Labeling Language 

Environmental Hazards “Atrazine can travel (seep or leach) through soil and can enter ground water which may be used as 

drinking water. Atrazine has been found in ground water. Users are advised not to apply atrazine to sand and loamy sand soils where the water table (ground water) is close to the surface and where these soils are very permeable; i.e., well-drained. Your local agricultural agencies can provide further 

information on the type of soil in your area and the location of ground water.” “Product must not be mixed or loaded within 50 feet of intermittent streams and rivers, natural or impounded lakes and reservoirs. Product must not be applied within 66 feet of points where field surface water runoff enters perennial or intermittent streams and rivers or within 200 feet of natural or impounded lakes and reservoirs. If this product is applied to highly erodible land, the 66 foot buffer or setback from runoff entry points must be planted to crop, or seeded with grass or other suitable crop.” “Product must not be mixed or loaded, or used within 50 feet of all wells, including abandoned wells, drainage wells, and sink holes. Operations that involve mixing, loading, rinsing, or washing of this product into or from pesticide handling or application equipment or containers within 50 ft. of any well are prohibited, unless conducted on an impervious pad constructed to withstand the weight of the heaviest load that may be positioned on or moved across the pad. Such a pad shall be designed and maintained to contain any product spills or equipment leaks, container or equipment rinse or wash wateand rain water that may fall on the pad. Surface water shall not be allowed to either flow over or form the pad which means the pad must be self-contained. The pad shall be sloped to facilitate material removal. An unroofed pad shall be of sufficient capacity to contain at a minimum 110% of the capacity of the largest pesticide container or application equipment on the pad. A pad that is covered by a roof osufficient size to completely exclude precipitation from contact with the pad shall have a minimum containment of 100% of the capacity of the largest pesticide container or application equipment on the pad. Containment capacities as described above shall be maintained at all times. The above-specified minimum containment capacities do not apply to vehicles when delivering pesticide to the mixing/loading sites.” “Additional State imposed requirements regarding well-head setbacks and operational area containmenmust be observed.” 

115
Description Amended Labeling Language 

Environmental Hazards Continued

 “One of the following restrictions must be used in applying atrazine to tile-outletted fields containing standpipes: - Do not apply within 66 feet of standpipes in tile-outletted fields. - Apply this product to the entire tile-outletted field and immediately incorporate it to a depth of 

2-3 inches in the entire field. 

- Apply this product to the entire tile-outletted field under a no-till practice only when a high cr

residue management practice is practiced. High crop residue management is described as a crmanagement practice where little or no crop residue is removed from the field during and after crop harvest.”

 “This pesticide is toxic to aquatic invertebrates. Do not apply directly to water, to areas where surface water is present, or to intertidal areas below the mean high water mark. Do not apply when weather conditions favor drift from treated areas. Runoff and drift from treated areas may be hazardous to aquatic organisms in neighboring areas. Do not contaminate water when disposing of equipment wash water.” 

Restricted-Entry Interval (for labels with WPS uses) 

“Do not enter or allow worker entry into treated areas during the restricted entry interval (REI) of 12 

hours.” 

Early Reentry Personal Protective Equipment established by the IRED (for labels with WPS uses. 

“PPE required for early entry to treated areas that is permitted under the Worker Protection Standard anthat involves contact with anything that has been treated, such as plants, soil, or water, is: > coveralls, > shoes plus socks, and > chemical resistant gloves, such as any waterproof material.” 

116
Description Amended Labeling Language 

Entry Restriction for Entry Restriction for non-WPS uses applied as a spray: NonWPS uses 

“Do not enter or allow others to enter until sprays have dried.” Entry Restriction for non-WPS uses applied dry: “Do not enter or allow others to enter until dusts have settled.” Entry Restriction for non-WPS uses applied as a solid (i.e. granular) and watered-in (for occupationuse to home lawns): “Do not enter or allow others to enter the treated area until dusts have settled. If soil incorporation is required after the application, do not enter or allow others to enter the treated area (except those personinvolved in the incorporation) until the incorporation is complete. If the incorporation is accomplished watering-in, do not enter or allow others to enter the treated area until the surface is dry after the watering-in.” 

117
Description Amended Labeling Language 

Other Application Restrictions (Risk Mitigation) 

All Products/Formulations Containing Atrazine “Do not apply this product through any type of irrigation system” “When tank-mixing or sequentially applying atrazine or products containing atrazine to corn or sorghumthe total pounds of atrazine applied (lbs ai/A) must not exceed 2.5 pounds active ingredient per year.” 

“When tank-mixing or sequentially applying atrazine or products containing atrazine to crops other thacorn or sorghum, the total pounds of atrazine applied (lbs ai/A) must not exceed the specific seasonal ralimits as noted in the use directions.” Delete all directions for use for the following use-patterns: >rangeland >total vegetation control on non-cropland areas (except Conservation Reserve Program(CRP), rights-oways, and roadsides) >proso millet, and >pineapple uses. Products with Guava Uses: – “Do not apply more than 4 pounds active ingredient per acre for any application.” – “Do not apply more than 8 pounds active ingredient per year.” Macadamia Nut Uses: – “Do not apply more than 4 pounds active ingredient per acre for any application.” – “Do not apply more than 8 pounds active ingredient per year.” Conifers Uses: – “Do not apply more than 4 pounds active ingredient per acre for any application.” – “Do not apply more than 4 pounds active ingredient per year.” 

118
Description Amended Labeling Language 

Other Application Restrictions (Risk Mitigation) 

Sod Farm Uses -For muck or peat soils:> “Do not apply more than 4 pounds active ingredient per acre for any application.”> “Do not apply more than 6 pounds active ingredient per year.”-For sandy soils:> “Do not apply more than 4 pounds active ingredient per acre for any application.” > “Do not apply more than 3 pounds active ingredient per year.”Conservation Reserve Program Uses: – “Do not apply more than 2 pounds active ingredient per acre for any application.” Chemical Fallow Uses: For soils in North and South Dakota with a pH of 7.5 or greater: – “Do not apply more than 1.5 pounds active ingredient per acre for any application.” – “Do not apply more than one application per year.” For soils in North and South Dakota with a pH of less than 7.5: – “Do not apply more than 2.0 pounds active ingredient per acre for any application.” – “Do not apply more than one application per year.” For all other locations: – “Do not apply more than 2.25 pounds active ingredient per acre for any application.” – “Do not apply more than one application per year.” 

119
Description Amended Labeling Language 

Other Application Restrictions (Risk Mitigation) continued 

Rights-of-Way Uses (applied as a spray): – “Do not apply more than 1.0 pounds active ingredient per acre for any application.” – “Do not apply more than one application per year.” Sugarcane Uses: – “Do not apply more than 4.0 pounds active ingredient per acre for any application.” – “Do not apply more than 10.0 pounds active ingredient per acre per year.” Corn and Sorghum Uses: -Field corn forage uses: 60-day PHI -Sweet corn forage uses: 45-day PHI - Preemergent sorghum forage uses: 60-day PHI - Postemergent sorghum forage uses: 45-day PHI -“Postemergence applications to corn and sorghum must be made before crop reaches 12 inches in height” “Maximum broadcast application rates for corn and sorghum must be as follows: 

> If no atrazine was applied prior to corn/sorghum emergence, apply a maximum of 2 lb ai/A broadcast. If a postemergence treatment is required following an earlier herbicide application, the total atrazine applied may not exceed 2.5 lb ai/A per calendar year. > Apply a maximum of 2.0 lb ai/A as a single preemergence application on soils that are not highly erodible or on highly erodible soils if at least 30% of the soil is covered with plant residues; or > Apply a maximum of 1.6 lb ai/A as a single preemergence application on highly erodible soif <30% of the surface is covered with plant residues; or 2.0 lb ai/A if only applied postemergence.” 

120
Description Amended Labeling Language 

Other Application Restrictions (Risk Mitigation) continued 

Roadsides Uses: – “Do not apply more than 1.0 pounds active ingredient per acre for any application.” – “Do not apply more than one application per year.” Dry Bulk Fertilizer Impregnation Uses: - “Impregnation of bulk fertilizer is restricted to commercial facilities. On-farm fertilizer impregnation prohibited.” - “No more than 500 tons of dry bulk fertilizer can be impregnated per day.” - “No single facility may impregnate fertilizer with this product for more than to 30 days per calendar year.” - “The commercial facility impregnating the dry bulk fertilizer must inform, in writing, the user (applicator) of the dry bulk fertilizer that: 

> “Applicators must wear long-sleeved shirt, long pants, shoes, and socks.” > “The restricted-entry interval is 12 hours.” 

Application Restrictions for Granular formulations that contain directions for use on turfgrass at residential sites, including homes, daycare facilities, schools, playgrounds, parks, recreational areas, and sports fields 

“Turfgrass at Residential Sites (including homes daycare facilities, schools, playgrounds, parks, recreational areas, and sports fields:” “This product must be watered in immediately after application. Watering-in must be performed by the commercial applicator or the commercial applicator must provide the following instructions to the resident or owner in writing: 

> “This product must be watered in immediately. > “Do not enter or allow others (including children or pets) to enter the treated areas (except those involved in the watering) until the watering-in is complete and the surface is dry.” 

121
Description Amended Labeling Language 

Application Restrictions for Liquid, Wettable Powder, or Dry Flowable (WaterDispersible Granule) formulations that contain directions for use on turfgrass at residential sites, including homes, daycare facilities, schools, playgrounds, parks, recreational areas, and sports fields 

“Turfgrass at Residential Sites (including homes daycare facilities, schools, playgrounds, parks, recreational areas, and sports fields):” – “Do not apply more than 1.0 pounds active ingredient per acre for any application.” – “Do not apply more than 2.0 pounds active ingredient per acre per year.” 

Application Restrictions for Dry Flowable Formulations NOT packaged in watersoluble packets 

“Aerial application is prohibited.” 

End Use Products Intended Primarily for Use by Homeowners 

Environmental Hazards “Atrazine can travel (seep or leach) through soil and can enter ground water which may be used as 

drinking water. Atrazine has been found in ground water. Users are advised not to apply Atrazine on sand and loamy soils where the water table (ground water) is close to the surface and where these soils are very permeable; i.e., well drained. Your local agricultural agencies can provide further information on the type of soil in your area and the location of ground water. This product is toxic to aquatic invertebrates. Do not apply directly to water, to areas where surface water is present or to intertidal are

below the mean high water mark. Runoff and drift from treated areas may be hazardous to aquatic organisms in neighboring areas. Do not contaminate water when disposing of equipment washwaters.” 

122
Description Amended Labeling Language 

Application Restrictions All products: 

“Do not apply this product in a way that will contact any person or pet, either directly or through drift. Keep people and pets out of the area during application.” Granular Products Applied Dry: “This product must be watered in immediately after application.” 

Entry Restriction Products Applied as a Liquid: 

“Do not allow people or pets to enter the treated area until sprays have dried.” Products Applied Dry: “Do not enter or allow others (including children or pets) to enter the treated areas (except those involvin the watering) until the watering-in is complete and the surface is dry.” 

123
Description Amended Labeling Language 

Precautionary Statements For Granular Lawn Products: 

“Do not apply granular lawn products by hand. Avoid contact with hands or skin.” “Broadcast applications must NOT be made using hand-held devices, such as a belly grinder or handherotary applicator. Such equipment may only be used for spot treatments.” For Liquid products: - “Maximum rate per application turfgrass (including lawns) is [registrant insert the maximum rate of thformulated product per unit area – such as 2 pints per 1,000 square feet – that reflects an maximum application rate of 1 pound active ingredient per acre].” – “Maximum of two applications per year.” 

124
APPENDICES

125
126
Appendix A: ATRAZINE USE PATTERNS ELIGIBLE FOR REREGISTRATION 

Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

FOOD/FEED USE PATTERNS Corn Broadcast or banded Early Preplant; preplant surface or incorporated, preemergence, or postemergence to corn #12" tall Ground or aerial applications 

90% DF 

4 lb/gal FlC 

Others d 

1.6 

preemergence on 

highly erodible 

soil if < 30% 

surface covered 

with plant 

residues 

2 preemergence 

on not highly 

erodible soil or if 

> 30% surface 

covered with 

plant residues 

2 postemergence 

NS 

(Not 

specified) 

2.5 60 for 

forage 

60 for 

field corn 

45 for 

sweet 

corn 

NS For preplant surface 

medium or fine-texttillage systems only KY, MN, MO, MT, WY, up to 45 days ptextured soils, do noplanting. 

Broadcast Fallow weed control (and continued control in following minimum tillage corn). Applied to stubble ground after wheat harvest in a wheat-corn-fallow crop rotation. Ground or aerial applications 

90% DF 

4 lb/gal FlC 

3 

1.5 

(ND & SD soils 

with pH>7.5) 

2.0

 (ND & SD soils 

with pH<7.5) 

1 NS NS NS Use limited to CO, K

WY. Wheat-corn-famust be followed. Do not apply followmonth plant-back reall crops other than tGrazing or feeding oareas are prohibited. 

127
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

Broadcast Winter weed control in TX Ground or aerial applications 

90% DF 

4 lb/gal FlC 

0.8-1.0 NS NS NS N/A For postemergence c

only on fall bedded and Blacklands of Tcontrol programs mafollowing corn, graiforage crops the follprohibits planting angrain sorghum, or fospring following thi

Guava Broadcast Ground application 

90% DF 

4 lb/gal FlC 

4.0 3 8.0 NS 120 Use only on establis

months old. Label stfrequntly than at 4-m“Do not apply more ingredient per acre f“Do not apply more ingredient per year.” 

Grain Sorghum or Sorghum-sudan hybrids (grain and forage types) 

128
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

Broadcast or banded Early Preplant; preplant surface or incorporated, preemergence, or postemergence to sorghum #12" tall Ground or aerial applications 

90% DF 

4 lb/gal FlC 

Others d 

1.6 

preemergence on 

highly erodible 

soil if < 30% 

surface covered 

with plant 

residues 

2 preemergence 

on not highly 

erodible soil or if 

> 30% surface 

covered with 

plant residues 

2 postemergence 

NS 2.5 60 for 

forage 

60 for 

preemerg. 

use 

45 for 

postemer. 

use 

NS A 60-day PGI or PH

For preplant surface medium or fine-texttillage systems only KY, MN, MO, MT, WY, up to 45 days ptextured soils, do noplanting. Do not apincorporated in AL, NC, NM, OK, SC, Tpreemergence in NMnortheast OK, the TX Blacklands areas. 

Broadcast Winter weed control in TX Ground or aerial applications 

90% DF 

4 lb/gal FlC 

0.8-1.0 NS NS NS NA For postemergence c

only on fall bedded and Blacklands of Tcontrol programs mafollowing corn, graiforage crops the follprohibits planting angrain sorghum, or fospring following thi

Broadcast Fallow weed control (and continued control in minimum tillage sorghum) applied to stubble ground following wheat harvest in a wheat-sorghumfallow crop rotation. Ground or aerial applications 

90% DF 

4 lb/gal FlC 

3 1 NS NS NA Wheat-sorghum-fall

must be followed. Do not apply follow18-month plant-back for all crops other thGrazing or feeding oareas are prohibited. 

Macadamia nuts 

129
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

Broadcast Ground application 

90% DF 

4 lb/gal FlC 

4.0 NS 8.0 NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Soybeans (Unspecified) 

43% EC 2.5 NS NS NS NS 

Sugarcane Broadcast or banded Preemergence (at-planting or ratooning) followed by one application at emergence, and up to two interline post-emergence directed applications prior to closein (lay-by). Ground or aerial application 

90% DF 

4 lb/gal FlC 

2-4 4 10 NS NS Treatments may be m

minimum of 20 gal/and 5 gal/A of water interval between laybe 120-150 days, prIn FL and TX, 0.5-1 of spray may be useof 2 lb ai/A may be weeds during summplanting applicationai/A. 

Fallow Wheat Stubble (Wheat is not a target crop) Broadcast Fallow weed control applied to stubble ground following wheat harvest in a wheat-fallow-wheat crop rotation. Ground or aerial applications 

90% DF 

4 lb/gal FlC 

0.5-1 1 NS NS NA Use limited to CO, K

WY. Grazing of treated amonths, and a 12-mfor wheat is specifie

NON FOOD/NON FEED USE PATTERNS Agricultural Fallow/Idleland 

130
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

At Planting 43% EC 

43% SC/L 

90% DF 

2.25 1 2.25 NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Established Plantings 90% DF 1 1 NS NS NS Fall 43% EC 

90% DF 

1 NS NS NS NS 

Fallow 20.9% EC 

21.92% FlC 

43% EC 

43% FlC 

43% SC/L 

80% WP 

85.5% DF 

90% DF 

90% WP 

2.25 1 2.25 NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

February March 

90% DF 1 NS NS NS NS 

Late Fall 43% FlC 0.4 1 0.4 NS NS 

85.5% DF 

90% DF 

Postharvest 22% FlC 1 1 1 NS NS 

43% EC 

90% WP 

Preemergence 43% EC 2 NS NS NS NS Preplant 43% SC/L 

85.5% DF 

90% DF 

131
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

Renovation 43% EC 2 NS 2 NS NS Spring 85.5% DF 

90% DF 

Stubble 22% EC 

22% FlC 

43% EC 

43% SC/L 

53.5% EC 

80% WP 

90% DF 

90% WP 

2.25 1 2.25 NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Bermudagrass Dormant, spring 43% EC 

90% DF 

2 NS NS NS NS 

Christmas Tree Plantations Fall, Early Spring 

21.42 EC 

80% WP 

4 NS NS NS NS 

Commercial/industrial Lawns Early Spring 

.58% G .92% G 

0.046 lb 1Kft 2 NS NS NS NS 

Fall 

.45% G 0.046 lb 1Kft 2 NS NS NS NS .92% G 

1.05% G 

Post-plant 

25% FIC .75 NS NS NS NS 

Spring 

132
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

.45% G .92% G 

1.05% G 

0.046 lb 1Kft 2 NS NS NS NS 

Conifers (Seed Orchard) Dormant 

43% EC 

90% WP 

4 NS 4 NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Forest Plantings (Reforestation Programs)(Tree Farms, Tree Plantations, Etc.) Early Spring 

80% WP 4 1 NS NS NS 

Fall 

80% WP 90% WP 

4 1 NS NS NS 

Forest Trees (Softwoods, Conifers) Dormant 

43% EC 

43% FIC 

85.5% DF 

90% DF 

4 1 4 NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Early Spring 

25% FIC 

90%DF 

90% WP 

3.96 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Established Planting 

133
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% EC 

43.6% EC 

53.48% EC 

80% WP 

85.5% DF 

90% DF 

4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Fall 

25% FIC 

43% EC 90% DF 

90% WP 

4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Post-Plant 

43% DF 43% EC 

4.4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Post-transplant 

43% EC 

43% SC/L 

43.5% EC 43.6% EC 

53.48% EC 

80% WP 

85.5% DF 

90% DF 

90% WP 

4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Pre-plant (Spring) 

134
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% DF 43% EC 

4.4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Pre-transplant 

43% RC 

43% SC/L 

43.5% EC 43.6% EC 

53.48% EC 

80% WP 

85.5% DF 

90% DF 

90% WP 

4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Spring 

43% DF 43% EC 

4.4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Transplant 

43% EC 

43% SC/L 

43.5% EC 

85.5% DF 

90% DF 

4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Winter 

135
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% DF 43% EC 

4.4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more ingredient per year.” 

Golf Course Turf At Planting 

90% DF 099 NS NS NS NS 

Dormant 

53.48% EC 

90% DF 

2.5 NS NS NS NS 

Early Spring 

90% DF 1.98 NS NS NS NS 

Fall 

.45% G 

.6% G 

.92% G 

43% EC 

43% FIC 

53.48% EC 

89% WP 

90% DF 

90% WP 

2 NS NS NS NS 

Foliar 

53.48% EC 

90% DF 

2.5 NS NS NS NS 

Late Winter 

136
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

.6% G 

43% EC 

43% FIC 

53.48% EC 

80% WP 

90% DF 

90.1% DF 

2 NS NS NS NS 

Post-plant 

25% FIC .75 NS NS NS NS 

Spring 

.45%G 

.6% G 

.92% G 

.046 lb/1Kft2 NS NS NS NS 

Winter 

90% DF 1.98 2 NS NS NS 

Grasses Grown for Seed Dormant 

43% FIC 

90% DF 

1 NS NS NS NS 

Nonagricultural Rights of way/fencerows/hedgerows Delayed Dormant 

43% EC 1 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Dormant 

137
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% EC 

53.48 EC 

2.5 NS NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Early Spring 

90% DF 

90.1% FIC 

3.96 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Fall 

43% EC 

43% FIC 

43% SC/L 

43.5% EC 43.6% EC 

53.48% EC 

80% WP 

85.5% DF 

90% DF 

90% WP 

90.1% DF 

90.1% FIC 

2.4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Foliar 

43% EC 

53.48% EC 

2.5 NS NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Spring 

138
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% EC 

43% FIC 

43% SC/L 

43.5% EC 43.6% EC 

53.48% EC 

80% WP 

85.5% DF 

90% DF 

90% WP 

90.1% DF 

90.1% FIC 

4 1 NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

When Needed 

43% EC 2 NS NS NS NS “Do not apply more 

ingredient per acre f“Do not apply more year.” 

Ornamental And/or Shade Trees Dormant 

43% EC 90% DF 

4 1 NS NS NS 

Early Spring 

53.48% EC 

90.1% DF 

4 1 NS NS NS 

Established Planting 

90% DF 3.96 1 NS NS NS 

Fall 

53.48% EC 

90.1% DF 

4 1 NS NS NS 

139
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

Post-transplant 

43% EC 

53.48% EC 

90% DF 

90.1% DF 

4 1 NS NS NS 

Pre-transplant 

43% EC 

53.48% EC 

90% DF 

90.1% DF 

4 1 NS NS NS 

Transplant 

43% EC 

90.1% DF 

4 1 NS NS NS 

Ornamental Lawns and Turf Dormant 

23.6% FIC 

43% EC 

43% FIC 

43% SC/L 

53.48% EC 

90% DF 

4 1 NS NS NS “This product must 

immediately after ap

Early Spring 

.58% G .92% G 

43% FIC 

90% DF 

1.98 NS NS NS NS “This product must b

immediately after ap

Early Winter 

.92% G .046 lb/1Kft2 NS NS NS NS “This product must b

immediately after ap

Fall 

140
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

042% G 

.57% G 

.6% G 

.63% G .79% G .83% G .91% G .92% G 

1.05% G 1.11% G 1.15% G 1.16% G 1.28% G 1.41% G 

1.5% G 

43%EC 

43% FIC 

80% WP 

85.5% DF 

90% DF 

90% WP 

2 NS NS NS NS “This product must 

immediately after ap

Foliar 

1.1% G 

23.6% FIC 

43% EC 

43% FI43% 

SC/L 

53.48% EC 

80% WP 

90% DF 

2.5 NS NS NS NS “This product must b

immediately after ap

Late Winter 

141
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

.6% G .8% G 

1.11% G 

43% EC 

43% FIC 

43% SC/L 

43.5% EC 43.6% EC 

80% WP 

90% DF 

90.1% DF 

4 NS NS NS NS “This product must 

immediately after ap

Postplant 

.42% G .44% G .91% G 

.75 NS NS NS NS “This product must 

immediately after ap

Preemergence 

90% DF 1.98 2 NS NS NS “This product must 

immediately after ap

Spring 

142
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

.42% G .57% G 

.6% G 

.63% G .79% G .83% G .91% G .92% G 

1.05% G 1.11% G 1.15% G 1.16% G 1.28% G 

1.5% G 

.048 lb/1Kft2 NS NS NS NS “This product must b

immediately after ap

Summer 

.6% G 

1.05% G 

.046 lb/1Kft2 NS NS NS NS “This product must b

immediately after ap

When Needed 

08% G 

.83% G .92% G 

1.22% G 1.41% G 

43% EC 

2 NS NS NS NS “This product must 

immediately after ap

Winter 

.42% G .63% G .91% G 

1.05% G 

90% DF 

1.98 NS NS NS NS “This product must b

immediately after ap

Ornamental Sod Farm (Turf) 

143
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

At Planting 

90% DF 3.96 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Dormant 

53.48% EC 

90% DF 

2 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Early Spring 

90% DF 2 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Fall 

144
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

.45% G .92% G 

43% EC 

43% FIC 

53.48% EC 

85.5% DF 

90% DF 

90% WP 

2 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Foliar 

43% EC 

43% FIC 

53.48% EC 

85.5% DF 

90% DF 

90% WP 

43% EC 

4 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Late Winter 

43% EC 

43% FIC 

53.48% EC 

85.5% DF 

90% DF 

90% WP 

90.1% DF 

43% EC 

2 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Post Harvest 

145
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% EC 

43% FIC 

53.48% EC 

85.5% DF 

90% DF 

90% WP 

90.1% DF 

4 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Post Plant 

43% EC 

43% FIC 

53.48% EC 

85.5% DF 

90% DF 

90% WP 

90.1% DF 

4 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Post-transplant 

80% WP 4 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Preemergence, Pretransplant and Preplant 

146
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% DC/L 4 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Spring 

.455G 

.92% G 

.046 lb 1Kft2 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

When Needed 

43% EC 90% DF 

3.96 NS NS NS NS “For muck or peat s

than 4 pounds active any application.” “Do not apply more ingredient per year.” “For sandy soils: do pounds active ingredapplication.” “Do not apply more ingredient per year.” 

Rangeland Established Planting 

147
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

43% EC 90% DF 

1 1 NS NS NS 

March 

90% DF 1 1 NS NS NS 

Preemergence 

43% EC 1 1 NS NS NS 

Recreation Area Lawns Dormant 

43% EC 

43% FIC 

43% SC/L 

53.48% EC 

90% DF 

2.5 NS NS NS NS 

Early Spring 

43% FIC 

90% DF 

1.98 NS NS NS NS 

Fall 

1.05% G 0.046 lb 1Kft 2 NS NS NS NS 

Foliar 

43% Ec 

43% FIC 

43% SC/L 

53.48% EC 

90% Df 

2.5 NS NS NS NS 

Late Winter 

80% Wp 

90% DF 

2 2 NS NS NS 

Post-plant 

25% FIC .75 NS NS NS NS 

148
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

Spring 

1.05% G 0.046 lb 1Kft 2 NS NS NS NS 

Recreational Areas Fall 

.45% G .92% G 

0.046 lb 1Kft 2 NS NS NS NS 

Spring 

.45% G .92% G 

0.046 lb 1Kft 2 NS NS NS NS 

Residential Lawns Dormant 

14% EC 

23.6% FIC 

43% EC 

43% FIC 

53.48% EC 

90% DF 

2.5 NS NS NS NS “This product must b

immediately after ap

Early Spring 

14% EC 

43% FIC 

90% DF 

1.98 NS NS NS NS “This product must b

immediately after ap

Early Summer 

14% Ec 0.046 lb 1Kft 2 NS NS NS NS “This product must b

immediately after ap

Fall 

149
Site 

Application Type Application Timing Application Equipment Formulation 

Max. Single 

Application Rate

 (lb ai/A) 

Max. # 

Apps/ 

season 

Max Annual 

Application 

Rate (lb ai/A) 

Preharvest 

Interval 

(days) 

Minimum 

Retreatment 

Interval 

(days) Use L

.45% G 

.6% G 

.92% G 

1.05% G 

14% EC 

0.046 lb 1Kft 2 NS NS NS NS “This product must b

immediately after ap

Foliar 

23.6% FIC 

43% EC 

43% FIC 

53.48% EC 

90% DF 

2.5 NS NS NS NS “This product must b

immediately after ap

Late Winter 

.6% G 

14% EC 

80% WP 

90% DF 

2 NS NS NS NS “This product must 

immediately after ap

Mid-Winter 

14% EC 0.046 lb 1Kft 2 NS NS NS NS “This product must b

immediately after ap

Post-Plant 

25% FIC .75 NS NS NS NS “This product must b

immediately after ap

Spring 

.45% G 0.6% G .92% G 

1.05% G 

14% EC 

0.046 lb 1Kft 2 NS NS NS NS “This product must b

immediately after ap

150
151
Appendix B: STUDIES USED TO SUPPORT THE REREGISTRATION OF ATRAZINE 

GUIDE TO APPENDIX B 

Appendix B contains listing of data requirements which support the reregistration for 

active ingredients within the case atrazine covered by this IRED. It contains generic data 

requirements that apply to atrazine in all products, including data requirements for which a 

"typical formulation" is the test substance. 

The data table is organized in the following formats: 

1. Data Requirement (Column 1). The data requirements are listed by Guideline Number. 

The Guideline Numbers accompanying each test refer to the test protocols set in the 

Pesticide Assessment Guidance available from the National Technical Information 

Service, 5285 Port Royal Road, Springfield, VA 22161 (703) 487-4650. 

2. Use Pattern (Column 2). This column indicates the use patterns for which the data 

requirements apply. The following letter designations are used for the given use patterns. 

A . Terrestrial Food H. Greenhouse Food 

B. Terrestrial Feed I. Greenhouse Non-Food 

C. Terrestrial Non-Food J. Forestry 

D. Aquatic Food K. Residential 

E. Aquatic Non-Food Outdoor L. Indoor Food 

F. Aquatic Non-Food Industrial M. Indoor Non-Food 

G. Aquatic Non-Food Residential N. Indoor Medical 

O. Indoor Residential 

3. Bibliographic Citation (Column 3). If the Agency has acceptable data in its files, this 

column list the identify number of each study. This normally is the Master Record 

Identification (MRID) number, but may be a "GS" number if no MRID number has been 

assigned. Refer to the Bibliography appendix for a complete citation of the study. 

152
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

PRODUCT CHEMISTRY 

830.1550 61-1 Product Identity and Composition All 40566501, 4318830.1600 830.1620 830.1650 

61-2A Starting Materials and Manufacturing Process All 40566501 

830.1670 61-2B Formation of Impurities All 00142160, 4204830.1700 62-1 Preliminary Analysis All 00142160, 0016

42211401, 428744488801 

830.1750 62-2 Certification of Limits All 40566501, 4292830.1800 62-3 Analytical Method All 00142160, 0016830.6302 63-2 Color All 00142160 830.6303 63-3 Physical State All 00142160 830.6304 63-4 Odor All 00142160 830.7050 None UV/Visible Absorption All data gap 830.7200 63-5 Melting Point All 00142160, 0016830.7220 63-6 Boiling Point All not applicable 830.7300 63-7 Density All 00023548, 430

153
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

830.7840 830.7860 

63-8 Solubility All 00023497, 4333

830.7950 63-9 Vapor Pressure All 00142160, 0016830.7370 63-10 Dissociation Constant in Water All 00022855 830.7550 830.7560 830.7570 

63-11 Partition Coefficient (Octanol/Water) All 00142160, 0016

830.7000 63-12 pH All 00142160, 4333830.6313 63-13 Stability All 00023497, 0002

43337901, 4379

830.6314 63-14 Oxidizing/Reducing Action All 43016501, 4318830.6315 63-15 Flammability All not applicable 830.6316 63-16 Explodability All 43016501, 4318830.6317 63-17 Storage Stability All 0023548, 43395830.7100 63-18 Viscosity All not applicable 830.6319 63-19 Miscibility All not applicable 830.6320 63-20 Corrosion Characteristics All 00142160, 430

ECOLOGICAL EFFECTS 

850.2100 71-1 Avian Acute Oral Toxicity Test 

ABCJK 

00024721 (paredata gap (3 ma

154
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

850.2200 71-2 Avian Dietary Toxicity ABCJK 00022923 850.2300 71-4 Avian Reproduction ABCJK 42547102, 4254850.1075 72-1 (a & b) Fish Acute Toxicity - Freshwater ABCJK 00024717, 0002

data gap (majo

850.1010 72-2 Acute Aquatic Invertebrate Toxicity ABCJK 00024377 (pare

data gap (majo

850.1075 72-3a Acute Estuarine/Marine Toxicity - Fish ABCJK 43344901 (pare

data gap (majo

850.1025 

72-3b Acute Estuarine/Marine Toxicity - Invertebrate (Mollusk) ABCJK data gap (pare

degradate) 

72-3c Estuarine/Marine Toxicity - Invertebrate (Shrimp) ABCJK 43344902 (pare

data gap (majo

850.1400 72-4a Early Life-Stage Fish (Freshwater) ABCJK 45208304 

72-4a Early Life-Stage Fish (Marine) ABCJK data gap 

45202920 (upgr

850.1300 72-4b Life-Cycle Aquatic Invertebrate ABCJK 00024377 850.1350 72-4b Life-Cycle Marine Invertebrate ABCJK 45202920, data 850.1500 72-5 Life-Cycle Fish ABCJK 00024377 850.4225 850.4230 

123-1a Seedling Germination/Seedling Emergence ABCJK 42041403 

155
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

850.4250 1231b Vegetative Vigor ABCJK 42041402 850.4400 123-2 Aquatic Plant Growth ABCJK 41065203a & b 

43074801, 4307

850.3020 141-1 Nontarget Insect Acute Contact Toxicity (Honey Bee) ABCJK 00036935 

TOXICOLOGY - Parent Atrazine 

870.1100 81-1 Acute Oral - Rat All 00024706, 0002

Accession No. 2

870.1200 81-2 Acute Dermal - Rabbit All 00024708, 0002

Accession Nos. 

870.1300 81-3 Acute Inhalation - Rat All 42089901, 430870.2400 81-4 Primary Eye Irritation - Rabbit All Accession No. 2

00024709 

870.2500 81-5 Primary Dermal Irritation - Rabbit All Accession No. 

00024709, 0002

870.2600 81-6 Dermal Sensitization All 00105131 870.3100 82-1 90-Day Feeding All 44723701 870.3200 82-2 21-Day Dermal Toxicity - Rat All 42089902 870.3700 83-3 Developmental Toxicity All 41065201, 0014

Accession No. 200143006, 4056

870.3800 83-4 Reproduction and Fertility Effects - 2 Generation Repro All 40431303, 4274

156
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

870.4100 870.4300 

83-1A 83-5 

Chronic Feeding Toxicity - Rodent Combined Chronic Toxicity/Carcinogenicity 

All 40629302, 4222

00158930, 4353

870.4100 83-1B Chronic Feeding Toxicity - Non-Rodent (dog) All 40431301 870.4200 83-2A Oncogenicity - Rat All 40629302, 4222

43934402, 0015

870.4200 83-2B Oncogenicity - Mouse All 40431302 non-guideline non-guideline Special Studies - Neurotoxicity All 44152102, 4393

45166901 

870.5100 84-2 Bacterial Reverse Mutation Assay All 00060642, 4024870.5385 84-2 Micronucleus Assay All 40722301 870.5450 84-2 Rodent Dominant Lethal Assay All 42637003 870.5550 84-2 UDS Assay All 00161790, 4072870.7485 85-1 General Metabolism All 40431304, 4043

42165503, 447

870.7600 85-2 Dermal Absorption All 43314302 (rat) 

44152114 (hum

non-guideline non-guideline Special Studies - Assays of Direct Estrogenic Activity of 

Triazines 

All 43598617, 4359

43934403 

non-guideline non-guideline Special Study - Estrous Cycle Alterations and LH Surge 

Attenuation - Method Validation 

All 43934405 

non-guideline non-guideline Special Study - Estrous Cycle Alterations and LH Surge 

Attenuation - Pilot 

All 43934404 

157
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

non-guideline non-guideline Special Study - Estrous Cycle Alterations and LH Surge 

Attenuation - 28-day 

All 43934406 

non-guideline non-guideline Special Study - Estrous Cycle Alterations and LH Surge 

Attenuation - 6-month 

All 44152102 

non-guideline non-guideline Special Study - Hormone and Estrous Cycle Measurements in 

SD Rats 

All 42085001, 4274

non-guideline non-guideline Special Study - Mammary Gland and Ovarian 

Histomorphology in SD Rats 

All 43598622, 4208

non-guideline non-guideline Special Study - Two-Year Bioassay in F-344 Rats All 42146101, 4274non-guideline non-guideline Special Study - Hormone and Estrous Cycle Measurements in 

F-344 Rats 

All 42743902, 4214

non-guideline non-guideline Special Study - Mammary Gland and Ovarian 

Histomorphology in F-344 Rats 

All 43598622, 4214

44917701 

non-guideline non-guideline Special Study - Two-year Bioassay with the SD Strain of Rate All 42204401 non-guideline non-guideline Special Study - Tumor Incidence in Ovariectomized (OVX) vs 

Intact Animals 

All 44544701 

non-guideline non-guideline Special Study - Sexual Maturation All 45058702, 4572non-guideline non-guideline Long-Term Estrous Cycle Measurements All Unaudited draft 

estrous cycle da

non-guideline non-guideline Direct Comparison of LH Surge Attenuation of Atrazine, 

Simazine, and Dact 

All 45471002, 4505

158
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

non-guideline non-guideline Other published literature All Cooper et al. 19

Shafer et al. 199Das et al. 2000 Cummings et alNarotsky et al. Laws et al. 200Stoker et al. 200

TOXICOLOGY - Degradate DACT 

870.1100 81-1 Acute Oral - Rat All 43013201 870.3100 82-1A Subchronic Oral Toxicity in Rats All 43013207 870.3150 870.4100 

82-1B 83-1B 

Subchronic & Chronic Oral Toxicity in Dogs All 41392401 

870.3700 83-3 Developmental Toxicity in Rats All 41392402 870.5100 84-2 Mutagenicity Study - Bacterial Reverse Mutation All 40722302 870.5550 84-2 Mutagenicity Study - UDS Assay All 40722303 

TOXICOLOGY - Degradate Desisopropyl Atrazine 

870.1100 81-1 Acute Oral - Rat All 43013201 870.3100 82-1A Subchronic Oral Toxicity in Rats All 43013205 870.3150 82-1B Subchronic Oral Toxicity in Dogs All 43013203 870.3700 83-3 Developmental Toxicity in Rats All 43013208 870.5100 84-2 Mutagenicity Study - Bacterial Reverse Mutation Assay All 43093101 

159
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

870.5385 84-2 Mutagenicity Study - Mammalian Bone Marrow Chromosome 

Aberration Test 

All 43093103 

870.5550 84-2 Mutagenicity Study - UDS Assay All 43093105 

TOXICOLOGY - Degradate Deethyl Atrazine 

870.1100 81-1 Acute Tox - Rat All 43013202 870.3100 82-1A Subchronic Oral Toxicity in Rats All 43013206 870.3150 82-1B Subchronic Oral Toxicity in Dogs All 43013203 870.3700 83-3 Developmental Toxicity in Rats All 43013209 870.5100 84-2 Mutagenicity Study - Bacterial Reverse Mutation Assay All 43093102 870.5385 84-2 Mutagenicity Study - Mammalian Bone Marrow Chromosome 

Aberration Test 

All 43093104 

870.5550 84-2 Mutagenicity Study - UDS Assay All 43093106 

TOXICOLOGY - Degradate Hydroxyatrazine 

870.3100 82-1A Subchronic Oral Toxicity in Rats All 41293501 870.3700 83-3 Developmental Toxicity in Rats All 41065202 870.4100 870.4300 

83-1A 83-5 

Chronic Toxicity - Rat All 43532001 

870.5100 84-2 Mutagenicity Study - Bacterial Reverse Mutation Assay All 40722304 870.5385 84-2 Mutagenicity Study - Mammalian Bone Marrow Chromosome 

Aberration Test 

All 41479401 

160
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

870.5550 84-2 Other Genetic Effects All 40722305, 4088

EPIDEMIOLOGY 

non-guideline non-guideline Cancer Epidemiologic Studies - Submitted to EPA All 45152101, 455non-guideline non-guideline Cancer Epidemiologic Studies - Other Published Literature All Alvanja et al. 2

Breckenridge 2Breckenridge 2MacLennan et aMacLennan et aMills 1998 

OCCUPATIONAL/RESIDENTIAL EXPOSURE 

875.1100 875.1300 875.1500 

231 232 235 

Applicator Exposure Monitoring (Dermal outdoor exposure, Inhalation outdoor exposure, Biological monitoring) 

ABCJK 43934416, 4393

44152109, 441544315403, 443

875.1500 235 Biological Monitoring ABCJK 44597605 

44597606 

875.1100 231 Dermal Exposure ABCJK 43016506 875.1100 875.1300 

231 232 

Exposure Monitoring (ORETF) ABCJK 44972201 

875.2100 132-1 Foliar Dislodgeable Residue Dissipation ABCJ 44883601 875.2100 132-1 Transferable Residue Dissipation: Lawn and Turf CK 44958001, 4495840.1100 201-1

 202-1 

Droplet Size Spectrum Drift Field Evaluation 

ABCJK data gap 

161
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

non-guideline non-guideline Dermal Transfer Efficiency of Granular Atrazine Residues 

From Turf to Dry and Wetted Palms 

CK 45622310, 4562

non-guideline non-guideline Exposure Assessments ABCJK 44152106, 4415

44597604 

ENVIRONMENTAL FATE 

835.2120 161-1 Hydrolysis of Parent and Degradates ABCJK 40431319 835.2240 161-2 Photodegradation - Water ABCJK 42089904, 4554835.2410 161-3 Photodegradation - Soil ABCJK 40431320 

42089905 

835.2370 161-4 Photodegradation - Air ABCJK not applicable 835.4100 162-1 Aerobic Soil Metabolism ABCJK 42089906 835.4200 162-2 Anaerobic Soil Metabolism ABCJK 42089906 835.4400 162-3 Anaerobic Aquatic Metabolism ABCJK 40431323 835.4300 162-4 Aerobic Aquatic Metabolism ABCJK data gap 835.1240 163-1 Leaching/Adsorption/Desorption ABCJK 40431324, 4043

40431327, 4043

835-1410 163-2 Volatility-Lab ABCJK data gap 835.6100 164-1 Terrestrial Field Dissipation ABCJK 42165504, 4216

42165506, 4043

835.1200 164-2 Aquatic (sediment) Dissipation ABCJK not applicable 835.1300 164-3 Forestry Dissipation ABCJK 40431340, 4204

162
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

835.1500 164-5 Soil, Long Term Dissipation ABCJK 40431339, 4208

42089912, 404340431336, 4208

850.1730 165-4 Bioaccumulation in Fish ABCJK 40431344 850.1950 165-5 Bioaccumulation in Non-Target Organisms ABCJK data gap 

ENVIRONMENTAL FATE - DRINKING WATER MONITORING DATA 

non-guideline non-guideline Atrazine Drinking Water Monitoring Data (PLEX & VMP) All 43598634, 4393

44152122, 441544315414, 445944856901, 449945058703, 450545209601, 452545475102, 4554

non-guideline non-guideline Atrazine Drinking Water Monitoring Data (ARP) All 45728401, 4573

Acetochlor Reg(ARP) Final ReMonitoring Pro

non-guideline non-guideline Atrazine Rural Well Monitoring Data ALL data gap non-guideline non-guideline Atrazine Ground-Water Monitoring Data All 43934414, 4422

45399906, 4554

RESIDUE CHEMISTRY 

163
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

860.1300 171-4A Nature of Residue - Plants AB 00023324 0002

00024786 000500161854 00042547116 42543048501 435944152119 441544315408 443

860.1300 171-4B Nature of Residue - Livestock AB 00022857 0003

00016306 000340431353 404340431356 404341209802 412041209806 412042925601 4350

860.1340 171-4C Residue Analytical Method - Plants AB 00016401 000

00023499 000200024482 000540431365 413942547119 43043395502 

860.1340 171-4D Residue Analytical Method - Animals AB 00023280 0002

40431364 404340431422 404342547120 42542547123 

860.1360 Multiresidue Methods AB 41423401, data 

164
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

860.1380 171-4E Storage Stability AB 00024482 4043

41258601 41241397101 433

860.1480 171-4J Magnitude of Residues - Meat, Milk, Poultry, Eggs 

Milk and the Fat, Meat, and Meat Byproducts of Cattle, 

Goats, Hogs, Horses, and Sheep 

Eggs and the Fat, Meat, and Meat Byproducts of Poultry 

AB 

00026977, 000840431424 

40431422, 4043

860.1500 171-4K Crop Field Trials - Macadamia Nuts AB 00024799, 4043860.1500 171-4K Crop Field Trials - Corn, field and sweet, K+CWHR AB 00094135, 0009

42547117, 435944315410, 4459

860.1500 171-4K Crop Field Trials - Sorghum grain AB 00093523, 4043

43598632, 441544597603, 4539

860.1500 171-4K Crop Field Trials - Wheat grain AB 00024475, 4043860.1500 171-4K Crop Field Trials - Corn forage and stover AB 00093520 0009

40431401 435944315410 445

860.1500 171-4K Crop Field Trials - Sorghum forage and stover AB 00093523 4043

43598632 443

860.1500 171-4K Crop Field Trials - Wheat forage, fodder, straw, grasses, and 

forage 

AB 00024475 0006

43160502 data gap 

165
APPENDIX B. Data Supporting Guideline Requirements for the Reregistration of Atrazine 

DATA REQUIREMENT CIT

New Guideline 

Number 

Old 

Guideline 

Number 

Study Title Use Pattern MRI

860.1500 171-4K Crop Field Trials - Orchardgrass, orchardgrass hay, rye, 

perennial 

AB 00024487 

860.1500 171-4K Crop Field Trials - RangeGrasses AB 00126712 

data gap 

860.1500 171-4K Crop Field Trials - Guava AB 00055643 860.1500 171-4K Crop Field Trials -Sugarcane AB 00115588, 4316860.1520 171-4L Processed Foods (Corn) AB 43160505 860.1520 171-4L Processed Foods (Sorghum) AB 43160503 860.1520 171-4L Processed Foods (Sugarcane) AB 43160504, 4339860.1520 171-4L Processed Foods (Wheat) AB 43160502 860.1850 165-1 Confined Rotational Crop AB 43016505 860.1900 165-2 Field Rotational Crop AB 43160501 

PROBABILISTIC ASSESSMENTS 

non-guideline non-guideline Probabilistic Drinking Water Exposure Assessment All 45503101, 4550

45629401, 457

non-guideline non-guideline Probabilistic Ecological Risk Assessment All 45299501, 4529

45622303 

166
167
Appendix C: TECHNICAL SUPPORT DOCUMENTS 

Additional documentation in support of this IRED is maintained in the OPP docket, 

located in Room 119, Crystal Mall #2, 1921 Jefferson Davis Highway, Arlington, VA. It is open 

Monday through Friday, excluding legal holidays, from 8:30 am to 4 pm. 

The docket initially contained the February 14, 2001 preliminary human health risk 

assessment, and the September 26, 2001 preliminary ecological fate and effects risk assessment 

and related documents. EPA then considered comments on these risk assessments, revised the 

risk assessments, and added the formal “Response to Comments” documents and the revised risk 

assessments to the docket in May 2002. Additional response to comments documents and 

documents supporting the IRED were published in January 2003. 

All documents, in hard copy form, may be viewed in the OPP docket room or 

downloaded or viewed via the Internet at the following sites: 

www.epa.gov/pesticides/op 

http://cascade.epa.gov/RightSite/dk_public_home.htm 

These documents include: 

SRRD Documents: 

• Atrazine Memorandum of Understanding. January 31, 2003 

• Atrazine Summary. May 2, 2002 

• Atrazine Overview. May 2, 2002 

HED Documents: 

IRED Supporting Documents 

• Atrazine: Addendum to Revised Human Health Risk Assessment for the Reregistration 

Eligibility Decision (RED) dated April 16, 2002. January 31, 2003 

• Atrazine: Reassessment of DWLOC value for use in human health risk assessment. 

January 31, 2003 

• Atrazine: Addendum to Revised Occupational and Residential Exposure Assessment and 

Recommendations for the Reregistration Eligibility Decision Document. January 31, 

2003 

• Atrazine: Response to Public Comments on the EPA’s April 16, 2002, Revised Human 

Health Risk Assessment and Associated Documents for the Reregistration Eligibility 

Decision (RED). January 31, 2003 

• Review of Additional Data on Potential Atrazine Exposure and Review Comments 

Submitted by Syngenta and NRDC on Atrazine Cancer Epidemiology Study: “Follow-up 

Study of Cancer Incidence Among Workers in Triazine-related Operations at the 

Novartis St. Gabriel Plant” by Elizabeth Delzell et al. January 15, 2003. 

168
• Atrazine: Response to Syngenta’s Comments on the EPA’s April 16, 2002, Revised 

Human Health Risk Assessment and Associated Documents for the Reregistration 

Eligibility Decision (RED). November 22, 2002 

Revised Risk Assessments and Supporting Documents 

• Atrazine: HED’s Revised Human Health Risk Assessment for the Reregistration 

Eligibility Decision (RED). April 16, 2002 

• Atrazine: Response to Public Comments on the EPA’s January 19, 2001, Revised 

Preliminary Human Health Risk Assessment and Associated Documents for the 

Reregistration Eligibility Decision (RED). April 16, 2002 

• Atrazine: Response to Syngenta’s Comments on the EPA’s January 19, 2001, Revised 

Preliminary Human Health Risk Assessment and Associated Documents for the 

Reregistration Eligibility Decision (RED). April 16, 2002 

• Atrazine/DACT - Reassessment Report of the FQPA Safety Factor Committee. April 8, 

2002 

• Atrazine/DACT - Fourth Report of the Hazard Identification Assessment Review 

Committee. April 5, 2002 

• Atrazine: Metabolism Assessment Review Committee. Residues to be Regulated and 

Residues of Concern for Dietary Assessment. November 15, 2000 

• Atrazine: Toxicology Chapter of the Reregistration Eligibility Decision. Second 

Revision. April 11, 2002 

• Atrazine: HED Product and Residue Chemistry Chapters. April 16, 2002 

• Atrazine: Revised Occupational and Residential Exposure Assessment and 

Recommendations for the Reregistration Eligibility Decision Document. April 25, 2002 

• Response to Comments from Sipcam Agro. April 18, 2002 

• Atrazine: Review of Probabilistic Exposure Assessment for Drinking Water from 28 

Community Water Systems. April 23, 2002. 

• Addendum and Corrections to Occupational and Residential Exposure Chapter for 

Atrazine. May 23, 2002. 

• Review of Atrazine Cancer Epidemiology Studies: “A Follow-up Study of Mortality 

Among Workers at the Novartis St. Gabriel Plant” “Follow-up Study of Cancer Incidence 

Among Workers in Triazine-related Operations at the Novartis St. Gabriel Plant” both by 

Elizabeth Delzell et al. March 25, 2002. 

• Review of Atrazine Cancer Epidemiology Study “Follow-up Study of Cancer Incidence 

Among Workers in Triazine-related Operations at the Novartis St. Gabriel Plant” by 

Elizabeth Delzell et al. December 13, 2001. 

Preliminary Risk Assessments and Supporting Documents 

• EPA’s Response to Syngenta’s Comments on the Preliminary Human Health Risk 

Assessment for Atrazine in Support of the Reregistration, Tolerance Reassessment, and 

Special Review. January 23, 2001 

• Atrazine - Drinking Water Exposure Assessment for Atrazine and Various ChloroTriazine and Hydroxy-Triazine Degradates. January 23, 2001 

169
• Atrazine - Toxicology Chapter of the Reregistration Eligibility Decision - Revised. 

January 19, 2001 

• Atrazine - HED’s Revised Preliminary Human Health Risk Assessment for the 

Reregistration Eligibility Decision (RED). January 19, 2001 

• Atrazine - Anticipated Residues and Acute and Chronic Dietary Exposure Assessments 

for Atrazine, Revised January 2001. January 18, 2001 

• Atrazine - HED Product and Residue Chemistry Chapters. January 18, 2001 

• Atrazine - Occupational and Residential Exposure Assessment and Recommendations for 

the Reregistration Eligibility Decision Document. January 18, 2001 

• Atrazine - 3rd Report of the Hazard Identification Assessment Review Committee. 

December 21, 2000 

• Atrazine - Evaluation of Carcinogenic Potential. December 13, 2000 

• Atrazine - Reevaluation by the FQPA Safety Factor Committee. November 14, 2000 

• Atrazine - Cancer Peer Review Committee Meetings - Provisional Conclusions. 

November 1, 2000 

• Review of Atrazine Incident Reports. October 31, 2000 

• Diaminochlorotriazine (DACT) - Report of the Hazard Identification Assessment Review 

Committee. August 28, 2000 

• Hydroxyatrazine - Report of the Hazard Identification Assessment Review Committee. 

August 28, 2000 

EFED Documents: 

IRED Supporting Documents 

• EPA Response to Comments from Syngenta and its Contractors, the Triazine Network, 

the Center for Regulatory Effectiveness, the American Water Works Association, the 

State of New York Office of Attorney General, the U.S. Department of Interior Fish and 

Wildlife Service, the California Regional Water Control Board, the American Farm 

Bureau Federation, and the Louisiana Farm Bureau Federation, about the EPA 

Reregistration Eligibility Science Chapter for Atrazine, Environmental Fate and Effects 

Chapter, dated April 22, 2002. March 2003 (Replaces January 2003 Response to 

Comments document) 

• Reregistration Eligibility Science Chapter for Atrazine: Environmental Fate and Effects 

Chapter (and Appendices). January 31, 2003 

• EPA Response to Comments. January 28, 2003 

Revised Risk Assessments and Supporting Documents 

• Reregistration Eligibility Science Chapter for Atrazine. Environmental Fate and Effects 

Chapter (and appendices). April 22, 2002. 

• EFED Review of Comments from Syngenta and Its Contractors About the EPA Revised 

Environmental Risk Assessment for Atrazine. April 22, 2002 

• EFED Review of Public Comments in Reponse to the EPA Revised Environmental Risk 

170
Assessment for Atrazine. April 10, 2002 

• Response to Comments Contained in Attachment 6 of Syngenta’s Comments on 

“Atrazine. HED’s Revised Human Health Risk Assessment for the Reregistration 

Eligibility Document.” April 9, 2002 

Preliminary Risk Assessments and Supporting Documents 

• Response to Syngenta’s Error Corrections of EPA’s Atrazine RED and Environmental 

Fate and Effects Chapter (including Appendices). March 16, 2001 

171
Appendix D: CITATIONS CONSIDERED TO BE PART OF THE DATA BASE 

SUPPORTING THE INTERIM REREGISTRATION DECISION 

(BIBLIOGRAPHY) 

GUIDE TO APPENDIX D 

1. CONTENTS OF BIBLIOGRAPHY. This bibliography contains citations of all studies 

considered relevant by EPA in arriving at the positions and conclusions stated elsewhere 

in the Reregistration Eligibility Document. Primary sources for studies in this 

bibliography have been the body of data submitted to EPA and its predecessor agencies 

in support of past regulatory decisions. Selections from other sources including the 

published literature, in those instances where they have been considered, are included. 

2. UNITS OF ENTRY. The unit of entry in this bibliography is called a "study." In the 

case of published materials, this corresponds closely to an article. In the case of 

unpublished materials submitted to the Agency, the Agency has sought to identify 

documents at a level parallel to the published article from within the typically larger 

volumes in which they were submitted. The resulting "studies" generally have a distinct 

title (or at least a single subject), can stand alone for purposes of review and can be 

described with a conventional bibliographic citation. The Agency has also attempted to 

unite basic documents and commentaries upon them, treating them as a single study. 

3. IDENTIFICATION OF ENTRIES. The entries in this bibliography are sorted 

numerically by Master Record Identifier, or "MRID” number. This number is unique to 

the citation, and should be used whenever a specific reference is required. It is not 

related to the six-digit "Accession Number" which has been used to identify volumes of 

submitted studies (see paragraph 4(d)(4) below for further explanation). In a few cases, 

entries added to the bibliography late in the review may be preceded by a nine character 

temporary identifier. These entries are listed after all MRID entries. This temporary 

identifying number is also to be used whenever specific reference is needed. 

4. FORM OF ENTRY. In addition to the Master Record Identifier (MRID), each entry 

consists of a citation containing standard elements followed, in the case of material 

submitted to EPA, by a description of the earliest known submission. Bibliographic 

conventions used reflect the standard of the American National Standards Institute 

(ANSI), expanded to provide for certain special needs. 

a Author. Whenever the author could confidently be identified, the Agency has 

chosen to show a personal author. When no individual was identified, the Agency 

has shown an identifiable laboratory or testing facility as the author. When no 

author or laboratory could be identified, the Agency has shown the first submitter 

as the author. 

172
b. Document date. The date of the study is taken directly from the document. When 

the date is followed by a question mark, the bibliographer has deduced the date 

from the evidence contained in the document. When the date appears as (1999), 

the Agency was unable to determine or estimate the date of the document. 

c. Title. In some cases, it has been necessary for the Agency bibliographers to 

create or enhance a document title. Any such editorial insertions are contained 

between square brackets. 

d. Trailing parentheses. For studies submitted to the Agency in the past, the trailing 

parentheses include (in addition to any self-explanatory text) the following 

elements describing the earliest known submission: 

(1) Submission date. The date of the earliest known submission appears 

immediately following the word "received." 

(2) Administrative number. The next element immediately following the 

word "under" is the registration number, experimental use permit number, 

petition number, or other administrative number associated with the 

earliest known submission. 

(3) Submitter. The third element is the submitter. When authorship is 

defaulted to the submitter, this element is omitted. 

(4) Volume Identification (Accession Numbers). The final element in the 

trailing parentheses identifies the EPA accession number of the volume in 

which the original submission of the study appears. The six-digit 

accession number follows the symbol "CDL," which stands for "Company 

Data Library." This accession number is in turn followed by an alphabetic 

suffix which shows the relative position of the study within the volume. 

173
BIBLIOGRAPHY 

MRID Citation 

00002875 Frear, D. E. H. and J. E. Boyd. 1967. Use of Daphnia magna for the 

microbioassay of pesticides. I. Development of standardized techniques for 

rearing Daphnia and preparation of dosage-mortality curves for pesticides. J. 

Econ. Entomol. 60(5):1228-1236. 

00016306 Hermes, P. (1972) Biphasic Extraction of Radioactive Metabolites from Treated 

Biological Material. Method no. AG-214 dated Aug 15, 1972. (Unpublished study 

received Sep 26, 1974 under 5F1606; submitted by Ciba-Geigy Corp., 

Greensboro, N.C.; CDL: 094385-Q) 

00016401 Cannizzaro, R.D.; Li, C. (1972) Determination of Atrazine Residues in Dry 

Crops by Gas Chromatography. Method no. AG-145 dated Nov 29, 1972. 

(Unpublished study received Feb 18, 1977 under 100-583; submitted by 

Ciba-Geigy Corp., Greensboro, N.C.; CDL: 228126-L) 

00016402 Cullen, T.; Balu, K. (1972) Determination of 2-Chloro-4,6-diamino s-triazine 

(G-28273) Residues in Sorghum by Gas Chromatography. Method no. AG-232 A 

dated Dec 20, 1972. (Unpublished study received Feb 18, 1977 under 100-583; 

submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:228126-M) 

00016403 Cheung, M.W.; Hsieh, K. (1974) Determination of Atrazine, G-30033, and 

G-28279 Residues in Rangeland Forage by Gas Chromatography. Method no. 

AG-269 dated Seted by Ciba-Geigy Corp., Greensboro, Method no. AG-269 

dated Sep 12, 1974. (Unpublished study received Feb 18, 1977 under 100-583; 

submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:228126-O) 

00022474 Malina, M. (1964) Dissipation of Banvel D from Bermuda Grass (Ap- plied 

6/28/63 in Texas): Report No. 3. (Unpublished study re- ceived Aug 30, 1965 

under 6F0466; submitted by Velsicol Chemical Corp., Chicago, Ill.; 

CDL:090517-G) 

00022855 Esser, H.O.; DuPuis, G.; Ebert, E.; et al. (1974) s-Triazines. Pages 129­

208,~In~Without Title|. By N.P. (Also~In~unpub- lished submission received 

Oct 7, 1977 under 100-566; submitted by Ciba-Geigy Corp., Greensboro, N.C.; 

CDL:231969-C) 

00022857 Bakke, J.E.; Larson, J.D.; Price, C.E. (1972) Metabolism of Atrazine and 2­

Hydroxyatrazine by the rat. Journal of Agricultural and Food Chemistry 

20(3):602-607. (Also~In~unpublished submission received Oct 7, 1977 under 

100-566; submitted by Ciba-Geigy Corp., Greensboro, N.C.,; CDL:231969-F) 

174
00022923 Hill, E.F.; Heath, R.G.; Spann, J.W.; et al. (1975) Lethal Dietary Toxicities of 

Environmental Pollutants to Birds: Special Scien- tific Report--Wildlife No. 191. 

(U.S. Dept. of the Interior, Fish and Wildlife Service, Patuxent Wildlife Research 

Center; unpublished report) 

00023280 Mattson, A.M.; Solga, J. (1966) The Determination of Atrazine, Simazine and 

Prometryne in Cow's Milk by Gas Chromatography. Method dated Nov 11, 1966. 

(Unpublished study received Jul 15, 1968 under 7F5034; submitted by Geigy 

Chemical Co., Ardsley, N.Y.; CDL:092912-A) 

00023324 Ciba-Geigy Corporation (19??) The Uptake of Atrazine by Corn Plants from a 

Post-emergence Application. (Unpublished study received May 17, 1960 under 

100-439; CDL:120785-E) 

00023497 Ciba-Geigy Corporation (19??) Name, Chemical Identity and Composition of 

Atrazine. (Unpublished study received Aug 10, 1973 un- der 4F1425; submitted 

by BASF Wyandotte Corp., Parsippany, N.J.; CDL:093800-A) 

00023499 Kahrs, R.A.; Gemma, A.A. (1970) Determination of Atrazine Residues in 

Bermuda Grass by Microcoulometric Gas Chromatography. Method AG-126 

dated Jan 29, 1970. (Unpublished study received Aug 10, 1973 under 4F1425; 

submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:0938-C) 

00023502 Geigy Chemical Corporation (19??) The Determination of Chlorotriazine 

Residues in Plant Material, Animal Tissues and Water Using the Ultraviolet 

Method: Anng, Including a Description of the the Ultraviolet Method: Analytical 

Bulletin No. 7. (Unpublished study received Aug 10, 1973 under 4F1425; 

CDL:093800-F) 

00023529 Humphreys, T.E. (1961) The Metabolism of Atrazine by Sugarcane Plants 

following Soil Application of the Herbicide. (Unpublished study received Apr 

Project Number: HWI 6117-178: 51-91. lished study received Apr 5, 1961 under 

100-439; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:101149-A) 

00023543 Foy, C. L. and H. Hiranpradit. 1977. Herbicide movement with water and effects 

of contaminant levels on non-target organisms. Virginia Polytech. Instit. State 

Univ., VA Water Resources Res. Center, OWRT Proj. A-046-VA. 89 p. 

00023544 Torres, A. M. R. and L. M. O’Flaherty. 1976. Influence of pesticides on 

Chlorella, Chlorococcum, Stigeoclonium (Chlorophyceae), Tribonema, 

Vaucheria (Xanthophyceae) and Oscillatoria (Cyanophyceae). Phycologia 

15(1):25-36. 

00023548 Ciba-Geigy Corporation (1977) Atrazine: Chemical Data Section. (Unpublished 

study received Jun 2, 1977 under 100-529; CDL: 230302-A) 

175 
00023963 Burkhard, N. (1976) Project Report 17/76: Hydrolysis of 2-Chloro- and 2­

Methylthio-4,6-bis-(alkylamino)-s-triazines under Laboratory Conditions. 

(Unpublished study received Apr 27, 1977 under 100-588; prepared by CibaGeigy, Ltd., submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:229641-A) 

00024328 Burkhard, N. and J. A. Guth. 1976. Photodegradation of atrazine, atraton and 

ametryne in aqueous solution with acetone as a photosensitizer. Pesticide Science 

7(1):65-71. (Also In: Unpublished submission received July 19, 1978 under 

 201-403; submitted by Shell Chemical Co., Washington, D.C.; CDL:234469-C). 

00024377 Macek, K. J., K. S. Buxton, S. Sauter, S. Gnilka and J. W. Dean. 1976. Chronic 

toxicity of atrazine to selected aquatic invertebrates and fishes. Prepared by EG 

& G Bionomics, Inc., Duluth, MN; submitted by Shell Chemical Co., 

Washington, D.C. 

00024377 Macek, K. J., K. S. Buxton, S. Sauter, S. Gnilka and J. W. Dean. 1976. Chronic 

toxicity of atrazine to selected aquatic invertebrates and fishes. US. EPA, Off. 

Res. Dev., Environ. Res. Lab. Duluth, MN. EPA-600/3-76-047. 49 p. 

00024395 Union Carbide Corp. 1975. Acute toxicity of SD 12011, Code 4-1-2-1 and Code 

4-1-3-1 to fiddler crabs, Uca pugilator. Prepared by Union Carbide Corp.; 

submitted by Shell Chemical Co., Washington, D. C. 

00024475 Forsythe, J.R.; King, E. (1967) Residue Report: Winter Wheat: AG-A No. 1608. 

(Unpublished study received Dec 29, 1967 under 7F0620; submitted by Geigy 

Chemical Co., Ardsley, N.Y.; CDL:090810-B) 

00024480 Solga, J.; Mattson, A. (1967) The Determination of 

2-Chloro-4-amino-6-isopropylamino-s-triazine (I) and 2-Chloro-4-amino-6­

ethylamino-s-triazine (II). (Unpublished study received Dec 29, 1967 under 

7F0620; submitted by Geigy Chemical Co., Ardsley, N.Y.; CDL:090810-G) 

00024482 Mattson, A.M.; Kahrs, R.A. (1967) Efficiency of Various Extraction Procedures 

in Removing Residual Atrazine from Field-Treated Sorghum. (Unpublished 

study received Dec 29, 1967 under 7F0620; submitted by Ciba-Geigy Chemical 

Co., Ardsley, N.Y.; CDL:090810-I) 

00024487 Lee, W.O.; Torrell, P.J.; Freeman, E.; et al. (1967) [Residues of Atrazine in 

Grasses]: AG-A No. 244. (Unpublished study including AG-A nos. 280, 463, 

1038..., received Dec 29, 1967 under 7F0620; prepared in cooperation with 

Oregon State Univ., Farm Crops Dept. and others, submitted by Geigy Chemical 

Co., Ardsley, N.Y.; CDL:090810-Q) 

00024706 Sachsse, K.; Bathe, R. (1975) Acute Oral LD450^ of Technical Atrazine (G 

30027) in the Rat: Project No. Siss 4569. (Unpublished study received Jun 2, 

176
1977 under 100-529; prepared by Ciba-Geigy, Ltd., submitted by Ciba-Geigy 

Corp., Greensboro, N.C.; CDL:230303-E) 

00024708 Sachsse, K.; Bathe, R. (1976) Acute Dermal LDI50^ in the Rat of Technical G 

30027: Project No. Siss 5663. (Unpublished study received Jun 2, 1977 under 

100-529; prepared by Ciba-Geigy, Ltd., submitted by Ciba-Geigy Corp., 

Greensboro, N.C.; CDL: 230303-G) 

00024709 Sachsse, K.; Ullmann, L. (1976) Eye Irritation in the Rabbit of G 30027: Project 

No. Siss 5663. (Unpublished study received Jun 2, 1977 under 100-529; prepared 

by Ciba-Geigy, Ltd., submitted by Ciba-Geigy Corp., Greensboro, N.C.; 

CDL:230303-H) 

00024710 Sachsse, K.; Ullmann, L. (1976) Skin Irritation in the Rabbit after Single 

Application of G 30027: Project No. Siss 5663. (Unpublished study received Jun 

2, 1977 under 100-529; prepared by Ciba-Geigy, Ltd., submitted by Ciba-Geigy 

Corp., Greensboro, N.C.; CDL:230303-I) 

00024716 Beliles, R. P. and W. J. Scott, Jr. 1965. Atrazine safety evaluation on fish and 

wildlife Bobwhite quail, mallard ducks, rainbow trout, sunfish, goldfish): 

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product chemistry data requested in agency letter of Oct. 9, 1986 - Atrazine 

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40246601 Deparade, E. (1986) Atrazine: Salmonella/Mammalian--Microsome Mutagenicity 

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40389109 McKay, J. (1987) Sutan + (Butylate) 6.7-E Field Accumulation on Rotational 

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prepared by Stauffer Chemical Co., Richmond Research Center. 124 p. 

40389110 McKay, J. (1987) Sutan + (Butylate) 6.7-E Field Accumulation on Rotational 

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40431301 O'Connor, D.; McCormick, G.; Green, J. (1987) Chronic Toxicity Study in Dogs: 

Atrazine Technical: Laboratory Study No. 852008. Unpublished study prepared 

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40431302 Hazelette, J.; Green, J. (1987) Oncogenicity Study in Mice: Atrazine Technical: 

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40431303 Mainiero, J.; Youreneff, M.; Giknis, M.; et al. (1987) Two-generation 

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40431304 Orr, G. (1987) Disposition of Atrazine in Rat: (General Metabolism): Atrazine: 

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40431305 Thede, B. (1987) Study of Carbon 14F-Atrazine Dose/Response Relationship in 

the Rat: (General Metabolism): Laboratory Study No. ABR-87087. Unpublished 

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40431306 Miles, B. (1987) Characterization and Identification of Atrazine Metabolites from 

Rat Urine: (General Metabolism): Laboratory Study No.: ABR-87115. 

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40431319 Spare, W. 1986. Determination of the hydrolysis rate constants of atrazine: 

Laboratory Study. No. 1236. 33 p. Unpublished study prepared by Agrisearch 

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40431320 Spare, W. 1987. Photodegradation of atrazine on soil surfaces exposed to 

artificial and natural sunlight: Laboratory Study No.1237. 68 p. Unpublished 

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Corp., Greensboro, NC. 

40431321 Rustum, A. 1987. Aerobic, aerobic/anaerobic, and sterile soil metabolism of 

carbon 14-atrazine: Laboratory Study No. 6015-185. 133 p. Unpublished study 

prepared by Hazleton Laboratories America, Inc., Madison, WI; submitted by 

Ciba-Geigy Corp., Greensboro, NC. 

40431322 Klaine, S. 1987. Biotic and abiotic degradation of atrazine and three of its 

metabolites in a west Tennessee soil: Laboratory Study No. TX-431. 63 p. 

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submitted by Ciba-Geigy Corp., Greensboro, NC. 

40431323 Spare, W. 1987. Anaerobic aquatic metabolism of atrazine: Laboratory Study 

No. 1231. 69 p. Unpublished study prepared by Agrisearch, Inc., Frederick, MD; 

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40431324 Yu, W. C. 1986. Determination of adsorption/desorption constants of atrazine: 

Laboratory Study No. 59-1A. 33 p. Unpublished study prepared by Cambridge 

Analytical Associates, Inc., Boston, MA; submitted by Ciba-Geigy Corp., 

Greensboro, NC. 

40431325 Yu, W. C. 1986. Determination of adsorption/desorption constants of G-28279: 

Laboratory Study No. 59-6A. Unpublished study prepared by Cambridge 

Analytical Associates, Inc., Boston, MA; submitted by Ciba-Geigy Corp., 

Greensboro, NC. 

40431326 Yu, W. C. 1986. Determination of adsorption/desorption constants of G-34048: 

Laboratory Study No. 59-7A. Unpublished study prepared by Cambridge 

Analytical Associates, Inc., Boston, MA; submitted by Ciba-Geigy Corp., 

Greensboro, NC. 

40431327 Yu, W. C. 1986. Determination of adsorption/desorption constants of G-28273: 

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Greensboro, NC. 

40431328 Yu, W. C. 1986. Determination of adsorption/desorption constants of G-30033: 

Laboratory Study No. 59-6A. Unpublished study prepared by Cambridge 

 Analytical Associates, Inc., Boston, MA; submitted by Ciba-Geigy Corp., 

Greensboro, NC. 

40431330 Saxena, A. M. 1987. Determination of the mobility of soil-aged 14C-atrazine 

residues by thin-layer chromatography: Laboratory Study No. HLA 6015-186. 

Unpublished study prepared by Hazleton, Laboratories America, Inc., Madison, 

WI; submitted by Ciba-Geigy Corp., Greensboro, NC. 

40431336 White, S. 1987. Field dissipation study on Aatrex Nine-O for terrestrial uses on 

bareground, Ripon, California: Laboratory Study No. 1641-86-71-01-21E-23. 

300 p. Unpublished study prepared by Minnesota Valley Testing Labs, Inc., New 

Elm, MN; Submitted by Ciba-Geigy Corp., Greensboro, NC. 

40431337 White, S. 1987. Field dissipation study on Aatrex Nine-O for terrestrial uses on 

bareground, Hollandale, Minnesota: Laboratory Study No. 

1641-86-71-01-21E-25. 356 p. Unpublished study prepared by Minnesota Valley 

Testing Labs, Inc., New Elm, MN; submitted by Ciba-Geigy Corp., Greensboro, 

NC. 

40431338 White, S. 1987. Field dissipation study on Aatrex Nine-O for terrestrial uses on 

corn, Ripon, California: Laboratory Study No.1641-86-71-01-06B-22. 311 p. 

Unpublished study prepared by Minnesota Valley Testing Labs, Inc., New Elm,

 MN; submitted by Ciba-Geigy Corp., Greensboro, NC. 

40431339 White, S. 1987. Field dissipation study on Aatrex Nine-O for terrestrial uses on 

corn, Hollandale, Minnesota: Laboratory Study No. 1641-86-71-01-06B-24. 372 

p. Unpublished study prepared by Minnesota Valley Testing Labs, Inc., New Elm, 

MN; submitted by Ciba-Geigy Corp., Greensboro, NC. 

40431340 Schofield, M. 1986. Combined field dissipation and aquatic non-target organism 

accumulation Studies on Aatrex Nine-O for forestry use at Oregon City, Oregon: 

Laboratory Study No. 32989. 135 p. Unpublished study prepared by Analytical 

Bio-Chemistry Laboratories, Inc., Columbia, MO; submitted by Ciba-Geigy 

Corp., Greensboro, NC. 

40431344 Forbis, A. 1986. Uptake, depuration, and bioconcentration and metabolite 

characterization of carbon 14-atrazine by bluegill sunfish (Lepomis 

macrochirus): Laboratory Study No. 34737. 107 p. Unpublished study prepared 

 by Analytical Bio-Chemistry Laboratories, Inc.; submitted by Ciba-Geigy Corp., 

185
 Greensboro, NC . 

40431352 Caballa, S. (1973) The in vitro Metabolism of Carbon 14 -Atrazine and 

Derivatives by Rat and Sheep Liver under Tissue Culture Conditions: (Nature of 

Residue--Metabolism): Laboratory Study No.: GAAC-73035. Unpublished 

study prepared by Ciba-Geigy Corp. 30p. 

40431353 Simoneaux, B. (1987) Distribution and Characterization of Carbon 14 -Atrazine 

in a Goat: (Nature of Residue--Metabolism): Laboratory Study No.: ABR-86056. 

Unpublished study prepared by Ciba-Geigy Corp. 42 p. 

40431354 Thede, B. (1987) Study of Solubilized Residues from Protease Treated Tissues of 

Carbon 14 -Atrazine Dosed Chickens and Goat: (Nature of 

Residue--Metabolism): Laboratory Study No.: ABR- 87105. Unpublished study 

prepared by Ciba-Geigy Corp. 44 p. 

40431355 Farrier, D. (1987) Study of Protease Released Metabolites in Selected Tissues of 

Lactating Goats Dosed with Carbon 14 -Atrazine: (Nature of 

Residue--Metabolism): Laboratory Study No.: ABR-87109. Unpublished study 

prepared by Ciba-Geigy Corp. 130 

40431356 Simoneaux, B. (1986) Distribution and Characterization of Carbon 14 -Atrazine 

in a Chicken: (Nature of Residue--Metabolism): Laboratory Study No.: 

ABR-86045. Unpublished study prepared by Ciba-Geigy Corp. 29 p. 

40431357 Madrid, S. (1987) Metabolism of Carbon 14 -Atrazine in Laying Hens Dosed for 

Eight Consecutive Days at 50 ppm: (Nature of Residue-Metabolism): Laboratory 

Stlism): Laboratory Study No.: ABR- Metabolism): Laboratory Study No.: 

ABR-87099. Unpublished study prepared by Ciba-Geigy Corp. 84 p. 

40431364 Bade, T. (1986) Determination of Atrazine, G-28279, G-30033 and G-28273 

Residues in Milk (including Sour Milk) using a Strong Cation Exchange Column 

Isolation and Cleanup: (Residue Analytical Method): Laboratory Study No.: 

AG-496. Unpublished studyprepared by Ciba-Geigy Corp. 19 p. 

40431365 Bade, T. (1987) Determination of Atrazine, G-30033, G-28279 and G-28273 

Residues in Forage, Fodder, Grain and Grain Fractions from Grain Crops Using 

Capillary Gas Chromatography: (Residue Analytical Method): Laboratory Study 

No.: AG-484. Unpublished study prepared by Ciba-Geigy Corp. 50 p. 

40431369 Bade, T. (1985) Determination of Atrazine, G-28279, G-30033 and G-28273 

Residues in Milk: (Residue Analytical Method): Laboratory Study No.: AG-463. 

Unpublished study prepared by Ciba-Geigy Corp. 19 p. 

40431370 Bade, T. (1985) Determination of Atrazine, G-28279, G-30033 and G-28273 

Residues in Beef Tissues (Blood, Muscle, Liver, Kidney, Fat): (Residue 

186
Analytical Method): Laboratory Study No.: AG-476. Unpublished study prepared 

by Ciba-Geigy Corp. 60 p. 

40431383 Bade, T. (1987) Residues of Atrazine and Its Chlorometabolites in Grain 

Sorghum (Forage, Fodder, Grain and Grain Fractions) following Application of 

Aatritions (Storage Stability): Study No. lowing Application of Aatrex 4L, 80W 

or Nine-O Herbicide: (Magnitude of Residues): Laboratory Study No.: 

ABR-87056. Unpublished study prepared by Ciba-Geigy Corp. 368 p. 

40431401 Bade, T. (1987) Residues of Atrazine and Its Chlorometabolites in Corn (Forage, 

Fodder, Grain and Grain Fractions) following Application of Aatrex 4L, 80W or 

Nine-O Herbicide (Magnitude of Residues): Study No. ABR-87057. Unpublished 

compilation prepared by Ciba-Geigy Corp. 947 p. 

40431418 Bade, T. (1987) Residues of Atrazine and Its Chlorometabolites in Macadamia 

Nutmeat following Application of Aatrex Herbicide (Magnitude of Residues): 

Study No. ABR-87096. Unpublished compilation prepared by Ciba-Geigy Corp. 

54 p. 

40431420 Bade, T. (1987) Residue of Atrazine and its Chlorometabolites in Wheat and 

Wheat Fractions Following Application of Aatrex Herbicide (Magnitude of 

Residues): Study No. ABR-87107. Unpublished study prepared in cooperation 

with Ciba-Geigy Corp and En-Cas A Analytical Laboratories. 130 p. 

40431421 Cheung, M. (1987) Residue Stability Study of Atrazine and Chlorometabolites in 

Sweet Corn, Field Corn and Field Corn Fractions under Freezer Storage Cond 

No.: AG-175. Unpublished study pre- under Freezer Storage Conditions 

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188
Micronucleus Test, Mouse: Study No. 871546. Unpublished study prepared by 

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189
ABR-89060. Unpublished study prepared by Ciba-Geigy Corp. 170 p. 

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41258601 Cheung, M. (1989) Simazine, Atrazine, and Chlorometabolites: Residue Stability 

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G-2827ex 4L, 80W or Nine-O Herbicide: (Mag- 30033, G-28279, and G-28273 

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42547102 Pedersen, C. A. and D. R. DuCharme. 1992. Atrazine technical: Toxicity and 

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42547103 Dionne, E. 1992. Atrazine technical – Chronic toxicity to the fathead minnow 

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42547105 Hertner, T. (1992) Autoradiographic DNA Repair Test on Rat Hepatocytes Tests 

for Other Genotoxic Effects: Lab Project Number: 911246. Unpublished study 

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42547115 Simoneaux, B.; Wurz, R. (1992) Atrazine--Overview of the Nature and 

Magnitude of Potential Market Metabolites in Corn and Sorghum: Analysis of 

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195
42547118 Wurz, R. (1992) Validation of Analytical Method AG-596 by the Analysis of 

[carbon 14]-Atrazine Treated Corn and Sorghum Raw Agricultrual Commodities: 

Deasso or Lasso + Atrazine Agricultrual Commodities: Determination of the 

Radioactive Accountability of Hydroxy-and Chloro-metabolites of Atrazine in 

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42547119 Wurz, R. (1992) Atrazine: Analytical Method for the Determination of G-34048 

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Enforcement Method (...) for the Determination of Residues of Atrazine, 

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43013208 Marty, J. (1992) G-28273 Technical: Teratology Study in Rats: Developmental 

Toxicity (Teratogenicity) Study in Rats with G-28279 Technical (Oral 

Administration): Lab Project Number: 901262. Unpublished study prepared by 

Ciba-Geigy Ltd. 298 p. 

197
43013209 Marty, J. (1992) G-30033 Technical: Teratology Study in Rats: Developmental 

Toxicity (Teratogenicity) Study in Rats with G-30033 Technical (Oral 

Administration): Lab Project Number: 901265. Unpublished study prepared by 

Ciba-Geigy Ltd. 296 p. 

43016501 Stubbs, D. (1993) Technical Atrazine: Product Chemistry: Lab Project Number: 

PC/93/014. Unpublished study prepared by Ciba Plant Protection. 5 p. 

43016502 Sova, J. (1993) Atrazine Technical: Response to the EPA Review of the Acute 

Inhalation Toxicity Study. Unpublished study prepared by Ciba Plant Protection. 

5 p. 

43016503 Larson, J. (1993) Carbon 14--Atrazine: Nature of Residue in Sugarcane: Final 

Report Amendment No. 1: Lab Project Number: HWI/6117/181: 95/91. 

Unpublished study prepared by Hazleton Wisconsin, Inc. 307 p. 

43016504 Wurz, R. (1993) Validation of Analytical Method AG-596 for the Determination 

of G-34048 and GS-17794 in Sugarcane and Wheat: Determination of the 

Radio-use activated carbon filters. Determination of the Radioactive 

Accountability of Hydroxy-and Chloro-metabolites of Atrazine in (carbon 

14)-Atrazine Treated Crops by Analytical Methods AG-596 and AG-484, 

IncludingResidue Data: Lab Project Number: ABR/93053. Unpublished 

studyprepared by Ciba Plant Protection. 87 p. 

43016505 Larson, J. (1993) Uptake and Metabolism of Atrazine in Field Rotational Crops 

Following Corn and Sorghum Treated at a Rate of 3.0 lb. AI/Acre: (carbon 

14)-Atrazine: Lab Project Number: HWI/6117/183. Unpublished study prepared 

by Hazleton Wisconsin, Inc. 273 p. 

43016506 Rosenheck, L.; Phillips, J.; Selman, F. (1993) Worker Mixer/Loader and 

Applicator Exposure to Atrazine: Lab Project Number: AE/91/511: 126/91. 

Unpublished study prepared by Pan-Agricultural Labs, Inc. 309 p. 

43048501 Ciba-Geigy Corp. (1993) Atrazine: Supplement to Nature of Residue in Corn and 

Sorghum: Lab Project Number: HWI 6117-178: 51-91: PM-013. Unpublished 

study. 50 p. 

43074801 Hoberg, J. R. 1993. Atrazine technical: Toxicity to the marine diatom, 

(Skeletonema costatum). SLI Rep. No. 93-4-4753. Prepared by Springborn 

Laboratories, Inc., Wareham, MA.; submitted by Ciba-Geigy Corporation, 

Greensboro, NC. 

43074802 Hoberg, J. R. 1993. Atrazine technical: Toxicity to the freshwater green alga, 

(Selenastrum capricornutum). SLI Rep. No. 93-4-4751. Prepared by Springborn 

Laboratories, Inc.,Wareham, MA.; submitted by Ciba-Geigy Corporation, 

198 
Greensboro, NC. 

43074803 Hoberg, J. R. 1993. Atrazine technical: Toxicity to duckweed, (Lemna gibba). 

SLI Rep. No. 93-11-5053. Prepared by Springborn Laboratories, Inc., Wareham, 

MA.; submitted by Ciba-Geigy Corporation, Greensboro, NC. 

43074804 Hoberg, J. R. 1993. Atrazine technical: Toxicity to duckweed, (Lemna gibba). 

SLI Rep. No. 93-4-4755. Prepared by Springborn Laboratories, Inc., Wareham, 

MA.; submitted by Ciba-Geigy Corporation, Greensboro, NC. 

43093101 Deparade, E. (1990) Salmonella and Escherichia/Liver-Microsome Test: G-28279 

Technical: Gene Mutations Test: Lab Project Number: 891243. Unpublished 

study prepared by Ciba-Geigy Limited. 39 p. 

43093102 Deparade, E. (1989) Salmonella and Escherichia/Liver-Microsome Test: G-30033 

Technical: Gene Mutations Test: Lab Project Number: 891236. Unpublished 

study prepared by Ciba-Geigy Limited. 37 p. 

43093103 Ogorek, B. (1991) Structural Chromosomal Aberration Test: Micronucleus Test, 

Mouse: G-28279 Technical: Lab Project Number: 901307. Unpublished study 

prepared by Ciba-Geigy Limited. 37 p. 

43093104 Ogorek, B. (1991) Structural Chromosomal Aberration Test: Micronucleus Test, 

Mouse: G-30033 Technical: Lab Project Number: 901309. Unpublished study 

prepared by Ciba-Geigy Limited. 40 p.

 43093105 Geleick, D. (1991) Tests for Other Genotoxic Effects: Autoradiographic DNA 

Repair Test on Rat Hepatocytes: G-28279 Technical: Lab Project Number: 

901308. Unpublished study prepared by Ciba-Geigy Limited. 94 p. 

43093106 Geleick, D. (1991) Tests for Other Genotoxic Effects: Autoradiographic DNA 

Repair Test on Rat Hepatocytes: G-30033 Technical: Lab Project Number: 

901310. Unpublished study prepared by Ciba-Geigy Limited. 94 p. 

43160501 Selman, F. (1993) Magnitude of Residues in Field Corn and Rotational Indicator 

Crops Following an Application of AATREX 4L Plus Crop Oil Concentrate 

(COC): Lab Project Number: ABR-93046: 101175: 25-91-B2. Unpublished 

study prepared by Biochemistry Department, Ciba-Geigy Corp. 1062 p. 

43160502 Ross, J. (1994) Atrazine--Magnitude of Residues in or on Wheat Following an 

Application of AATREX Nine-O to Wheat Stubble (Wheat-Fallow-Wheat): Lab 

Project Number: ABR-93045: 119-89-B1: 101171. Unpublished study prepared 

by Biochemistry Department, Ciba-Geigy Corp. 716 p. 

43160503 Ross, J. (1994) Atrazine--Magnitude of the Residues in or on Grain Sorghum, 

199
Used for Processing, Following Post Application of AATREX Nine-O: Lab 

Project 1979 under 100-583; prepared in of AATREX Nine-O: Lab Project 

Number: ABR-93079: 58-89-A: 101170. Unpublished study prepared by 

Biochemistry Department, Ciba-Geigy Corp. 252 p. 

43160504 Ross, J. (1994) Atrazine--Magnitude of the Residues in or on Sugarcane and 

Processed Fractions Following Applications of AATREX Nine-O or AATREX 

4L: Lab Project Number: ABR-93044: 101173: 25-89. Unpublished study 

prepared by Biochemistry Department, Ciba-Geigy Corp. 658 p. 

43160505 Selman, F. (1994) Atrazine--Magnitude of the Residues in Corn Samples 

Following Applications of AATREX Nine-O: Amendment No. 1 to Add Results 

of Processing of Corn Grain: Lab Project Number: ABR-92028: 101168: 57-89. 

Unpublished study prepared by Biochemistry Department, Ciba-Geigy Corp. 507 

p. 

43188901 Jackson, W. (1994) Atrazine Technical: Product Chemistry: Lab Project Number: 

PC-94-003. Unpublished study prepared by Ciba-Geigy Corp. 12 p. 

43188902 Stubbs, D. (1994) Atrazine Technical: Product Chemistry: Lab Project Number: 

PC-94-003: MP94-001. Unpublished study prepared by Ciba-Geigy Corp. 15 p. 

43314302 Chengelis, C. (1994) A Dermal Radiotracer Absorption Study in Rats with 

(carbon 14) Atrazine: Final Report: Lab Project Number: 82048: 89/90/B. 

Unpublished study prepared by WIL Research Laboratories, Inc. 510 p. 

43337901 Stubbs, D. (1994) Technical Atrazine: Product Chemistry: Lab Project Number: 

PC/94/008. Unpublished study prepared by Ciba Plant Protection. 174 p. 

43344901 Machado, M. W. 1994. Atrazine technical -- Acute toxicity to sheepshead 

minnow (Cyprinodon variegatus) under flow-through conditions. Prepared by 

Springborn Laboratories, Inc., Wareham, MA; submitted by Ciba-Geigy Corp., 

Greensboro, NC. 

43344902 Machado, M. W. 1994. Atrazine technical -- Acute toxicity to mysid shrimp 

(Mysidopsis bahia) under flow-through conditions. Prepared by Springborn 

Laboratories, Inc., Wareham, MA; submitted by Ciba-Geigy Corp., Greensboro, 

NC. 

43395501 Stubbs, D. (1994) Product Chemistry: Technical Atrazine: Lab Project Number: 

PC/94/015: PPD/228/93/F. Unpublished study prepared by Ciba-Geigy Corp. 23 

p. 

43395502 Wurz, R. (1992) Validation of Analytical Methods AG-571 and AG-572 for the 

200
Analysis of G-34048 and GS-17794 in Crops by High Performance Liquid 

Chromatography with Column Switching: Lab Project Number: ABR/91032: 

101982. Unpublished study prepared by Ciba-Geigy Corp. 37 p. 

43395503 Wurz, R. (1994) Stability of the Atrazine and Ametryn Metabolites G-34048 and 

GS-17794 in Crop Substrates Under Freezer Storage Conditions: Lab Project 

Number: ABR/94053. Unpublished study prepared by Ciba-Geigy Corp. 68 p. 

43395504 Ross, J. (1994) Atrazine: Magnitude of Residues in or on Sugarcane and 

Processed Fractions Following Applications of AATREX NINE-0 or AATREX 

4L-Amendment 1 (Supplement to EPA MRID No. 43160504): Lab Project 

Number: ABR/93044. Unpublished study prepared by Ciba-Geigy Corp. 41 p. 

43934407 Hui, X.; Wester, R.; Maibach, H. (1995) Disposition of Atrazine in Rhesus 

Monkey Following Intravenous Administration: Interim Report: Lab Project 

Number: UCSF 95SU04: 333-95. Unpublished study prepared by University of 

California. 63 p. 

43505801 Stubbs, D. (1994) Atrazine Technical: Supplement to Product Chemistry: Lab 

Project Number: PC-94-018: AK-53/2. Unpublished study prepared by Ciba Crop 

Protection. 71 p. 

43508501 Tortora, N. (1993) Metabolism of (Triazine-(carbon 14)-Hydroxy-Atrazine in 

Lactating Goats: Addendum 1 to F-00123: Lab Project Number: G-34048: 

F-00123. Unpublished study prepared by Ciba-Geigy Corp. 12 p. 

43532001 Chow, E.; Hart, S. (1995) 2-Year Dietary Toxicity/Oncogenicity Study with G34048 (Hydroxyatrazine) in Rats: Final Report: Lab Project Number: F-00125. 

Unpublished study prepared by Ciba-Geigy Corp. 2599 p. 

43598602 Simoneaux, B. (1995) Nature of Atrazine and Simazine Metabolism in Animals 

and Plants: Lab Project Number: ABR-95039. Unpublished study prepared by 

Ciba-Geigy Corp. 67 p. 

43598604 Cheung, M. Analysis of Human Urine to Determine Residues of Atrazine, G28273, G-28279, and G-30033 Resulting From Oral Ingestion of Atrazine 

Including Storage Stability Results. Ciba-Geigy Corp.[now Syngenta] March 7, 

1990. 44 p. 

43598608 Johnson, E. (1993) An Evaluation and Critique of Atrazine Developmental 

Toxicology Safety Evaluations and Human Epidemiological Data: A Review of 

Published and Unpublished Studies for Hazard Potential and Risk Estimation: 

Lab Project Numbers: 832020: 832039. Unpublished study prepared by CibaGeigy Corp. 43 p. 

43598609 Austin, H. (1995). A Critique of a Document Entitled “Summary: Low Birth 

201
Weight in Relation to Source and Characteristic of Drinking Water Supplies in 

Rural Areas of Iowa” by Peter Isacson, Dated October, 1989. No Laboratory 

Number. Unpublished study prepared by Ciba-Geigy Corp.[now Syngenta] 7 p. 

43598610 Johnson, E. (1993) The Effects of Representative Groundwater Pesticides on 

Reproduction and in utero Development of Experimental Animals: Lab Project 

Number: 311U-4349-16: 356/311U--3698. Unpublished study prepared by CibaGeigy Corp. 19 p. 

43598614 Eldridge, J.; Fleenor-Heyser, D.; Extrom, P.; et al. (1994) Short-term effects of 

chlorotriazines on estrus in female Sprague-Dawley and Fischer 344 rats. Journal 

of Toxicology and Environmental Health 43:155-167. 

43598616 Tennant, M.; Jerome, W.; Eldridge, J. (1993) Ultrastructural changes in rat 

hypothalamic arcuate nucleus following long-Term diaminochlorotriazine 

feeding. Steroid Biochemistry (Life Sci. Adv.) 12:21-26. 

43598617 Tennant, M.; Hill, D.; Eldridge, J.; et al. (1994) Possible antiestrogenic properties 

of chloro-s-triazines in rat uterus. Journal of Toxicology and Environmental 

Health 43:183-196. 

43598618 Tennant, M.; Hill, D.; Eldridge, J.; et al. (1994) Chloro-s-triazine antagonism of 

estrogen action: Limited interaction with estrogen receptor binding. Journal of 

Toxicology and Environmental Health 43:197-211 

43598619 Safe, S.; Chen, I.; Liu, H.; et al. (1995) Failure of Atrazine and Simazine to 

Induce Estrogenic Responses in MCF-7 Human Breast Cancer Cells. 

Unpublished study prepared by Texas A&M Univ.; and Univ. of Western 

Ontario. 25 p. 

43598620 Simpkins, J. (1995) Evaluation of a Hormonal Mechanism for Mammary 

Carcinogenesis of the Chlorotriazine Herbicides; Consensus Panel Report. 

Unpublished study prepared by Univ. of Florida. 44 p. 

43598621 Wetzel, L.; Tisdel, M. (1995) Ciba Response to May 3, 1994, EPA Letter by 

Penelope Fenner-Crisp, Director, Health Effects Division, Office of Prevention, 

Pesticides and Toxic Substances, U.S. EPA. Unpublished study prepared by CibaGeigy Corp. 43 p. 

43598622 McConnell, R. (1995) A Histomorphologic Reevaluation of the Ovaries, Uterus, 

Vagina, Mammary Gland, and Pituitary Gland From Sprague-Dawley and 

Fischer-344 Female Rats Treated With Atrazine: Lab Project Numbers: 483-278: 

483-279. Unpublished study prepared by Ciba-Geigy Corp. 107 p. 

202 
43598624 Lamb, J. (1995) Weight of the Evidence on the Oncogenic Potential of Atrazine: 

Consensus Panel Report. Unpublished study prepared by Jellinek, Schwartz & 

Connolly, Inc. 38 p. 

43598625 Delzell, E.; Sathiakumar, N. (1995) An Evaluation of Epidemiologic Studies of 

Exposure to Triazines and Cancer in Humans: Triazine. Unpublished study 

prepared by Ciba-Geigy Corp. 51 p. 

43598626 Sathiakumar, N.; Delzell, E.; Cole, P. (1995) Mortality Among Workers at Two 

Triazine Herbicide Manufacturing Plants. Unpublished study prepared by 

University of Alabama (at Birmingham). 31 p. 

43598627 Breckenridge, C. (1995) Response to EPA Review of Retrospective Triazine 

Mortality Studies. Unpublished study prepared by Ciba-Geigy Corp. 25 p. 

43598628 Larson, J.; Ash, S. (1993) (Carbon 14)-Atrazine: Nature of the Residue in 

Sugarcane: Supplement No. 1 to the Final Report: Lab Project Numbers: HWI 

6117-181: 95-91. Unpublished study prepared by Hazleton Wisconsin, Inc. 231 

p. 

43598629 Larson, J.; Ash, S. (1992) (Carbon 14)-Atrazine: Nature of the Residue in Corn 

and Sorghum: Amendment No. 2 to the Final Report: Lab Project Numbers: HWI 

6117-178: 51-91. Unpublished study prepared by Hazleton Wisconsin, Inc. 146 

p. 

43598630 Gold, B. (1995) Magnitude of Residues in Field Corn Forage, Silage-Stage 

Forage, Fodder, and Grain and Sweet Corn Ears and Forage Following 

Applications of AATREX 4L to Field Corn: Atrazine: Lab Project Numbers: 

ABR-91070: 35-A-88. Unpublished study prepared by Ciba-Geigy Corp. 563 p. 

43598631 Gold, B. (1995) Magnitude of Residues in Grain Sorghum Forage, Hay, 

Silage-Stage Forage, Fodder, Grain, and Processed Grain Fractions Following 

Applications of AATREX 4L to Grain Sorghum: Atrazine: Lab Project Number: 

ABR-91071: 34-88. Unpublished study prepared by Ciba-Geigy Corp. 503 p. 

43598632 Selman, F. (1995) Atrazine and Metolachlor--Magnitude of Residues in Soil and 

Grain Sorghum Following Applications of AATREX 4L and DUAL 8E With and 

Wi6117-178: 51-91. Unpublished AATREX 4L and DUAL 8E With and Without 

the Addition of Acrysol G-110: Lab Project Numbers: 02-HR-002-91 CA: 

03-HR-004-91 MS: 04-HR-002-91 IL. Unpublished study prepared by 

Ciba-Geigy Corp. 326 p. 

43598633 Wurz, R. (1995) Dietary Risk Exposure Assessment for Atrazine: Lab Project 

Number: ABR-94021. Unpublished study prepared by Ciba-Geigy Corp. 65 p. 

203
43598634 Clarkson, J.; Golden, K. (1995) Human Exposure to Atrazine and Simazine Via 

Ground and Surface Drinking Water: Lab Project Number: 2852.0410. 

Unpublished study prepared by Ciba-Geigy Corp. 1350 p. 

43598637 Selman, F. (1995) Summary of Assessment of Worker Exposure for Atrazine in 

Response to the U.S. Environmental Protection Agency Issuance of "The Triazine 

Herbicides Position Document 1 Initiation of Special Review.": Lab Project 

Number: ABR-95041. Unpublished study prepared by Ciba-Geigy Corp. 17 p. 

43598638 Selman, F. (1995) Assessment of Worker Exposure for Atrazine in Response to 

the U.S. Environmental Protection Agency Issuance of "The Triazine Herbicides 

Position Document 1 Initiation of Special Review.": Lab Project Number: ABR95038. Unpublished study prepared by Ciba-Geigy Corp. 115 p. 

43598639 Kendall, R.; Soloman, K.; Baker, D.; et al. (1995) Ecological Risk Assessment of 

Atrazine in North American Surface Waters: Lab Project Number: WEI 242.12­

A. Unpublished study prepared by Atrazine Ecological Risk Assessment Panel. 

926 p. 

43689801 Krautter, G. 1995. 14C-Propazine: disposition and metabolism in the rat. PTRL 

East, Inc. . Richmond, KY. PTRL Project No. 821, June 16, 1995. 

43796001 Stubbs, D. (1995) Product Chemistry: Technical Atrazine: (Stability): (Final 

Report): Lab Project Number: PC-95-032: 458-95F. Unpublished study prepared 

by Ciba-Geigy Corp. 35 p. 

43934402 Pettersen, J.C. and Turnier, J.C. 1995. One-year chronic toxicity study with 

atrazine technical in rats. Ciba-Geigy Environmental Health Center, Farmington, 

CT. Lab Study no. F-00171. 

43934403 Safe, S. (1995) Failure of chloro-s-triazine derived compounds to induce 

estrogenic responses in vivo and in vitro. in Fundamental Applied Toxicology (in 

Press). 

43934404 Morseth, S. (1996) Evaluation of the Luteinizing Hormone (LH) in Female 

Sprague-Dawley Rats--Pilot Study: Final Report: Lab Project Number: CHV 

2386-109: 6791. Unpublished study prepared by Corning Hazleton Inc. (CHV). 

33 p. 

43934405 Morseth, S. (1996) Evaluation of the Luteinizing Hormone (LH) in Female 

Sprague-Dawley Rats--Method Validation: Final Report: Lab Project Number: 

CHV 2386-110: 6791F: 2386-110. Unpublished study prepared by Corning 

Hazleton Inc. (CHV). 32 p. 

43934406 Morseth, S. (1996) Evaluation of the Luteinizing Hormone (LH) Surge in 

204
Atrazine-Exposed Female Sprague-Dawley Rats: Interim Report: Lab Project 

Number: CHV 2386-111: 6791E: 2386-111. Unpublished study prepared by 

Corning Hazleton Inc. (CHV). 624 p. 

43934407 Hui, X.; Wester, R.; Maibach, H. (1995) Disposition of Atrazine in Rhesus 

Monkey Following Intravenous Administration: Interim Report: Lab Project 

Number: UCSF 95SU04: 333-95. Unpublished study prepared by University of 

California. 63 p. 

43934408 Maibach, H. (1996) Disposition of Atrazine in Rhesus Monkey Following 

Intravenous Administration: Interim Report: Lab Project Number: ABR-95131: 

333-95. Unpublished study prepared by Ciba-Geigy Corp. and University of 

California. 59 p. 

43934411 Hackett, D.; Bray, L. (1996) Updated Dietary Exposure Assessment for Atrazine: 

Lab Project Number: ABR-96009. Unpublished study prepared by Ciba-Geigy 

Corp. 48 p. 

43934412 Thalacker, F. (1996) Determination of Transfer Rate and Nature of the Residue(s) 

in Milk from (carbon 14)-Atrazine Treated Cows: Lab Project Number: CHW 

6117-325: 287-95: AM044. Unpublished study prepared by Corning Hazleton, 

Inc. 105 p. 

43934413 Clarkson, J.; Golden, K.; Tierney, D.; et al. (1996) Human Exposure to atrazine 

and Simazine via Ground and Surface Drinking Water: Update-I: Lab Project 

Number: 2852.0480: 696-95. Unpublished study prepared by Montgomery 

Watson. 1840 p. 

43934414 Balu, K. and P. W. Holden. 1996. Ciba/State ground-water monitoring study for 

atrazine and its major degradation products in the United States. Final Report. 

Ciba Study No. 174-91. 24 p. Unpublished study prepared by Waterborne 

 Environmental, Inc. Leesburg, VA.; submitted by Ciba-Geigy Corp., Greensboro, 

NC. 

43934415 Sielken, R.; Bretzlaff, R.; Valez-Flores, C. (1996). Preliminary Risk 

Characterization for Atrazine and Simazine: Lab Project Number: 56. 

Unpublished study prepared by Sielken, Inc. 1254 p. 

43934416 Brady, J.F. (1995). Analytical Method for the Semi-Quantitative Determination 

of Atrazine Mercapturate in Urine by Enzyme Immunoassay including Validation 

Study. Laboratory Project Identification Analytical Method Number AG-638. 

Unpublished study prepared by Ciba-Geigy Corp. [now Syngenta] 34 p. 

43934417 Evaluation of the Potential Exposure of Workers to Atrazine During 

Commercial Mixing, Loading, and Spray Applications to Corn. Biological Field 

205
Phase. Honeycutt, R., Bennet, R., and DeGeare, M. (1996). HERAC, Inc. No. 95­

501HE. Ciba Study No. 178-95. Unpublished study prepared by Ciba Crop 

Protection.[now Syngenta] 839 pages. 

43934418 Selman, F. (1996). Assessment of Potential Worker Exposure to Atrazine During 

Commercial Mixing, Loading, and Application to Corn: Interim Report: Lab 

Project Number: ABR-95133: 101930: 178-95. Unpublished study prepared by 

Ciba-Geigy Corp. [now Syngenta] 64 p. 

43934419 Solomon, K. R., D. B. Baker, R. P. Richards, K. R. Dixon, S. J. Kline, T. W. La 

Point, R. J. Kendall, C. P. Weisskopf, J. M. Giddings, J. P. Giesy, L. W. Hall, Jr., 

and M. Williams. Ecological risk assessment of atrazine in North American 

surface waters. Environ. Toxicol. Chem. 15(1):31-76. 

43934420 Ecorisk, Inc. (1995) Ecological Risk Assessment of Atrazine in North American 

Surface Waters: Additional Considerations of Exposure and Ecological Effects. 

Unpublished study. 35 p. 

43934421 Benjamin, R. (1996) Characterization of Selenastrum Capricornutum Response to 

Episodic Atrazine Exposure: Lab Project Number: 09524: TIWET 09542: 

TIWET-09524. Unpublished study prepared by The Institute of Wildlife and 

Environmental Toxicology, Clemson University. 92 p. 

43934422 Drewing, L. (1996) Supplement to Ciba's Benefits Analysis of Atrazine and 

Simazine: Lab Project Number: EV-1991-3: OPP-30000-60: SS-AGR-9. 

Unpublished study prepared by Ciba-Geigy Corp. 532 p. 

44008601 Delzell, E, I. Brill, and C. Beall. (1996). A follow-up Study of Workers at the 

Ciba-Geigy St. Gabriel Plant. Laboratory Study No. Supplemental Document No. 

11181. Unpublished study prepared by Ciba-Geigy Corp.[now Syngenta] 42 p. 

44008602 Gass, R. and G.A. Stalder. (1993). Atrazine: An Epidemiology Study at the 

Schweizerhalle Plant. Laboratory Study No. Supplemental Document No. 

11182. Unpublished study prepared by Ciba-Geigy Corp.[now Syngenta] 36 p. 

44152102 Morseth, S. (1996) Evaluation of the Luteinizing Hormone (LH) Surge in 

Atrazine-Exposed Female Sprague-Dawley Rats--(Final) 6-Month Interim 

Report: Lab Project Number: CHV 2386-111: 2386-111: 6791E. Unpublished 

study prepared by Corning Hazleton Inc. 727 p. 

44152104 Simpkins, J. (1996) Evaluation of a Hormonal Mode of Action for Mammary 

Carcinogenesis of the Chlorotriazine Herbicides: Second Concensus Panel 

Report. Unpublished study prepared by Ciba-Geigy Corp. 37 p. 

44152105 Consensus Panel (1995) Weight of the Evidence on the Oncogenic Potential of 

206
Atrazine: Consensus Panel Report. Unpublished study. 38 p. 

44152106 An Updated Assessment of Worker Exposure for Atrazine in Response to the U.S. 

Environmental Protection Agency Issuance of the “Triazine Herbicides Position 

Document 1 Initiation of Special Review”. Supplement to ABR-95038: 

Assessment of Worker Exposure for Atrazine in Response to the U.S. 

Environmental Protection Agency Issuance of the “Triazine Herbicides Position 

Document – Initiation of Special Review” (MRID 435986-38). Laboratory 

Project Number: ABR-96071. Unpublished study by Ciba Crop Protection.[now 

Syngenta] 124 pages. 

44152108 Selman, F.B. (1996). Supplemental Data and Evaluation of Exposure to Lawn 

Care Operators Using Atrazine in the Southern United States. Supplement to 

ABR-95038: Assessment of Worker Exposure from Atrazine in Response to the 

U.S. Environmental Protection Agency Issuance of the “Triazine Herbicides 

Position Document – Initiation of Special Review” (MRID 435986-38). 

Laboratory Project Number: ABR-96069. Unpublished study by Ciba Crop 

Protection.[now Syngenta] 13 pages. 

44152109 Selman, F.B. and L. Rosenheck. (1996). Evaluation of the Potential Exposure of 

Workers to Atrazine During Commercial Mixing, Loading, and Spray 

Applications to Corn: (Final Report): Lab Project Number: ABR-95133. 

Unpublished study prepared by Ciba Crop Protection.[now Syngenta] 199 p. 

44152110 Bodalbhai, L. (1996) Analytical Method for the Determination of Residues of 

Atrazine, G-30033, G-28279, and G-28273 in Urine by Gas 

Chromatography/Mass Selective Detection Including Validation Data: Lab 

Project Number: 264-95: AG-637: 101930. Unpublished study prepared by Ciba 

Crop Protection. 91 p. 

44152111 Honeycutt, R.C., Bennett, R.M. and DeGeare, M.A. (1996). Evaluation of the 

Potential Exposure of Workers to Atrazine during Commercial Mixing, Loading, 

and Spray Application to Corn (EPA-Subpart U) -- Biological Field Phase: Final 

Report: Lab Project Number: 178-95: 95-501HE: 95-517. Unpublished study 

prepared by Ciba Crop Protection [now Syngenta]. 687 pages, 2 volumes. 

44152113 Hui, X.; Wester, R.; Simoneaux, B.; et al. (1996) Disposition of Atrazine in 

Rhesus Monkey Following Oral Administration: Lab Project Number: ABR96094: UCSF 96SU01: 306-96. Unpublished study prepared by University of 

California, San Francisco and Ciba Crop Protection. 171 p. 

44152114 Hui, X.; Gilman, S.; Simoneaux, B.; et al. (1996) In vivo Percutaneous Absorption 

of Atrazine in Man: Lab Project Number: ABR-96067: BDH-081-2: H832-11835­

01. Unpublished study prepared by UCSF; UC Davis; and Ciba Crop Protection. 

297 p. 

207
44152115 Bray, L. (1996) Revised Dietary Exposure Assessment for Atrazine: Lab Project 

Number: ABR-96105. Unpublished study prepared by Ciba-Geigy Corp. 97 p. 

44152117 Boyette, S. (1996) Atrazine--Magnitude of the Residues In or On Corn: (Final 

Report): Lab Project Number: ABR-96087: 25-96: 101930. Unpublished study 

prepared by Ciba-Geigy Corp. 211 p. 

44152118 Boyette, S. (1996) Atrazine--Magnitude of the Residues In or On Grain Sorghum: 

Lab Project Number: ABR-96088: 26-96: 101930. Unpublished study prepared 

by Ciba-Geigy Corp. 286 p. 

44152119 Thalacker, F.; Ash, S. (1996) (Carbon 14)-Atrazine: Nature of the Residues in 

Corn and Sorghum: Amendment No. 3 to the Final Report: MRID 42547116: Lab 

PW 6117-325: 287-95: AM044. Report: MRID 42547116: Lab Project Number: 

HWI 6117-178: 51-91. Unpublished study prepared by Hazleton Wisconsin, Inc. 

31 p. 

44152120 Thalacker, F.; Ash, S. (1996) (Carbon 14)-Atrazine: Nature and Magnitude of the 

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1992. A reconnaissance study of herbicides and their metabolites in surface water of the

midwestern United States using immunoassay and gas chromatography/mass spectroscopy. 

Environ. Sci. Technol. 26:2440-2447. 

Thursby, G. B. and M. Tagliabue. 1990. Effect of atrazine on sexual reproduction in the kelp, 

Laminaria saccharina. (Memorandum to D. J. Hansen, US. EPA, Narragansett, RI. September

14.)Timchalk, C., Dryzga, M. D., Langvardt, P. W., Kastl, P. E., and Osborne, D. W. 1990.

Determination of the effect of tridiphane on the pharmacokinetics of [14C]-atrazine following

oral administration to male Fischer 344 rats. Toxicology 61: 27-40. 

Trapp, S., M. Matthies, I. Sceunert and E. M. Topp. 1990. Modeling the bioconcentration of

organic chemicals in plants. Environ. Sci. Technol. 24:1246-1252. 

Trentacoste, S. V., Friedmann, A. S., Youker, R. T., Breckenridge, C. B., and Zirkin, B. R. 2001.

Atrazine effects on testosterone levels and androgen-dependent reproductive organs in 

250
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Trochimowicz, H. J., Kennedy, G. L., and Krivanek, N. 1994. Heterocyclic and Miscellaneous

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Urinary 2-hydroxy estrone ratio and risk of breast cancer in postmenopausal women. J. Nat. 

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van den Brink, P. J., E. van Donk, R. Gylstra, S. J. H. Crum and T. C. M. Brock. 1995. Effects 

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development of non-Hodgkin’s lymphoma. Scan J Work Environ Health 19:108-114. 

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Appendix E: GENERIC DATA CALL-IN 

Note that a complete Data Call-In (DCI), with all pertinent instructions, will be sent to

 registrants under separate cover. 

253
Generic DCI Page 1 of 9 

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Generic DCI Page 2 of 9 

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Generic DCI Page 3 of 9 

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Generic DCI Page 4 of 9 

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Generic DCI Page 5 of 9 

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Generic DCI Page 6 of 9 

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Generic DCI Page 7 of 9 

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Generic DCI Page 8 of 9 

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Generic DCI Page 9 of 9 

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Appendix F: PRODUCT SPECIFIC DATA CALL-IN

 Note that a complete Data Call-In (DCI), with all pertinent instructions, will be sent to

registrants under separate cover. 

265
Product Specific DCI Page 1 of 7 

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Product Specific DCI Page 2 of 7 

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Product Specific DCI Page 3 of 7 

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Product Specific DCI Page 4 of 7 

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Product Specific DCI Page 5 of 7 

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Product Specific DCI Page 6 of 7 

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Product Specific DCI Page 7 of 7 

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274
Appendix G: EPA'S BATCHING OF ATRAZINE PRODUCTS FOR MEETING ACUTE 

TOXICITY DATA REQUIREMENTS FOR REREGISTRATION 

In an effort to reduce the time, resources and number of animals needed to fulfill the 

acute toxicity data requirements for reregistration of products containing ATRAZINE as the 

active ingredient, the Agency has batched products which can be considered similar for purposes

of acute toxicity. Factors considered in the sorting process include each product's active and inert

ingredients (identity, percent composition and biological activity), type of formulation (e.g.,

emulsifiable concentrate, aerosol, wettable powder, granular, etc.), and labeling (e.g., signal

word, use classification, precautionary labeling, etc.). Note that the Agency is not describing

batched products as "substantially similar" since some products within a batch may not be

considered chemically similar or have identical use patterns. 

Using available information, batching has been accomplished by the process described in

the preceding paragraph. Notwith-standing the batching process, the Agency reserves the right to

require, at any time, acute toxicity data for an individual product should the need arise. 

Registrants of products within a batch may choose to cooperatively generate, submit or

cite a single battery of six acute toxicological studies to represent all the products within that

batch. It is the registrants' option to participate in the process with all other registrants, only

some of the other registrants, or only their own products within a batch, or to generate all the

required acute toxicological studies for each of their own products. If a registrant chooses to

generate the data for a batch, he/she must use one of the products within the batch as the test

material. If a registrant chooses to rely upon previously submitted acute toxicity data, he/she

may do so provided that the data base is complete and valid by today's standards (see acceptance

criteria attached), the formulation tested is considered by EPA to be similar for acute toxicity,

and the formulation has not been significantly altered since submission and acceptance of the

acute toxicity data. Regardless of whether new data is generated or existing data is referenced,

registrants must clearly identify the test material by EPA Registration Number. If more than one

confidential statement of formula (CSF) exists for a product, the registrant must indicate the

formulation actually tested by identifying the corresponding CSF. 

In deciding how to meet the product specific data requirements, registrants must follow

the directions given in the Data Call-In Notice and its attachments appended to the RED. The

DCI Notice contains two response forms which are to be completed and submitted to the Agency

within 90 days of receipt. The first form, "Data Call-In Response," asks whether the registrant

will meet the data requirements for each product. The second form, "Requirements Status and

Registrant's Response," lists the product specific data required for each product, including the

standard six acute toxicity tests. A registrant who wishes to participate in a batch must decide

whether he/she will provide the data or depend on someone else to do so. If a registrant supplies

the data to support a batch of products, he/she must select one of the following options:

Developing Data (Option 1), Submitting an Existing Study (Option 4), Upgrading an Existing

Study (Option 5) or Citing an Existing Study (Option 6). If a registrant depends on another's

data, he/she must choose among: Cost Sharing (Option 2), Offers to Cost Share (Option 3) or

Citing an Existing Study (Option 6). If a registrant does not want to participate in a batch, the

choices are Options 1, 4, 5 or 6. However, a registrant should know that choosing not to

participate in a batch does not preclude other registrants in the batch from citing his/her studies

and offering to cost share (Option 3) those studies. 

275
One hundred and thirty-five products were found which contain Atrazine as the active 

ingredient. These products have been placed into fourteen batches and a "No Batch" category in

accordance with the active and inert ingredients and type of formulation. Furthermore, the 

following bridging strategies are deemed acceptable for this chemical: 

• Batch 11: EPA Reg. No. 524-493 and 524-497 may cite the data generated with EPA

Reg. No. 524-510. 

• Batch 13: Each product in this Batch should generate their own primary eye irritation

study utilizing the fertilizer with the highest levels of nitrogen. 

• Batch 14: Each product in this Batch should generate their own primary eye irritation

study utilizing the fertilizer with the highest levels of nitrogen. 

• No Batch: Each product in this Batch should generate their own data. 

NOTE: The technical acute toxicity values included in this document are for informational

purposes only. The data supporting these values may or may not meet the current acceptance 

criteria.

 Batch 1 EPA Reg. No. % Active Ingredient 

100-529 98.00 

11603-32 98.81 

19713-7 97.00 

19713-375 97.00 

34704-784 97.00 

35915-6 98.50 

62719-456 97.60

 Batch 2 EPA Reg. No. % Active Ingredient 

100-585 90.0 

1381-159 90.0 

1386-660 90.0 

2749-485 90.0 

5905-522 90.0 

9779-253 90.1 

11773-13 90.0 

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 Batch 2 EPA Reg. No. % Active Ingredient 

19713-76 90.0 

19713-499 90.0 

33270-9 90.0 

34704-622 90.0 

34704-689 90.0 

35915-3 90.0 

42750-53 90.0 

55467-4 90.0 

59639-106 90.0 

62719-313 90.0 

66222-37 90.0

 Batch 3 EPA Reg. No. % Active Ingredient 

9779-254 80.0 

34704-490 80.0 

51036-9 80.0 

51036-159 80.0

 Batch 4 EPA Reg. No. % Active Ingredient 

19713-80 53.48 

19713-291 53.48

 Batch 5 EPA Reg. No. % Active Ingredient 

100-497 43.5 

534-97 43.5 

829-268 43.0 

1381-158 43.0 

277
 Batch 5 EPA Reg. No. % Active Ingredient 

1386-647 43.0 

2749-336 43.0 

5905-470 43.0 

7401-318 43.0 

9404-72 43.0 

9779-255 43.0 

11773-1 43.6 

19713-11 43.0 

19713-498 43.0 

33270-10 43.5 

34704-69 43.0 

34704-690 43.0 

35915-4 43.0 

42750-44 43.0 

42750-45 43.0 

48273-11 43.5 

51036-158 43.0 

55467-5 43.5 

62719-312 43.0 

66222-36 43.6

 Batch 6 EPA Reg. No. % Active Ingredient 

100-817 Atrazine: 33.7 

S-Metolachlor: 26.1 

100-886 Atrazine: 33.7 

S-Metolachlor: 26.1 

278
 Batch 7 EPA Reg. No. % Active Ingredient 

352-600 Atrazine: 28.4 

Dimethenamid: 24.8 

7969-146 Atrazine: 28.4 

Dimethenamid: 24.8

 Batch 8 EPA Reg. No. % Active Ingredient 

7969-136 Atrazine: 22.23 

Dicamba K Salt: 13.42 

42750-41 Atrazine: 22.23 

Dicamba K Salt: 13.42 

51036-307 Atrazine: 22.23 

Dicamba K Salt: 13.42 

70907-16 Atrazine: 21.92 

Dicamba K Salt: 13.45

 Batch 9 EPA Reg. No. % Active Ingredient 

264-477 Atrazine: 21.62 

Bromoxynil Octanoate: 15.74 

9779-348 Atrazine: 21.62 

Bromoxynil Octanoate: 15.74 

51036-255 Atrazine: 21.62 

Bromoxynil Octanoate: 15.74 

71368-27 Atrazine: 21.62 

Bromoxynil Octanoate: 15.74 

279
 Batch 10 EPA Reg. No. % Active Ingredient 

51036-363 Atrazine: 25.0 

Bentazon: 27.0 

60063-18 Atrazine: 25.0 

Bentazon: 27.0

 Batch 11 EPA Reg. No. % Active Ingredient 

524-493 Atrazine: 16.1 

Acetochlor: 21.5 

Glyphosate: 8.1 

524-497 Atrazine: 16.2 

Acetochlor: 21.6 

Glyphosate: 8.2 

524-510 Atrazine: 15.9 

Acetochlor: 21.2 

Glyphosate: 15.9

 Batch 12 EPA Reg. No. % Active Ingredient 

19713-513 Atrazine: 16.6 

Acetochlor: 24.8 

62719-371 Atrazine: 16.6 

Acetochlor: 24.8

 Batch 13 EPA Reg. No. % Active Ingredient 

538-18 1.055 

538-163 0.600 

538-229 1.320 

538-234 0.600 

280
 Batch 13 EPA Reg. No. % Active Ingredient 

9198-186 1.110

 Batch 14 EPA Reg. No. % Active Ingredient 

769-943 0.92 

7138-14 0.90 

7401-336 0.83 

8660-12 1.16 

8660-18 1.18 

8660-32 0.58 

8660-41 0.92 

8660-187 0.63 

8660-204 0.92 

8660-223 1.05 

8660-224 0.91 

8660-245 0.42 

9198-153 0.92 

9404-51 0.92 

9404-55 0.79 

9404-56 1.50 

9404-80 0.57 

9404-81 1.28 

9404-82 1.15 

9779-359 0.92 

9779-360 0.80 

10404-39 0.80 

10404-94 1.05 

10404-95 0.45 

10404-96 0.92 

34704-822 0.92 

281
 Batch 14 EPA Reg. No. % Active Ingredient 

35512-14 0.80 

35512-34 0.57 

35512-41 1.22 

35512-42 0.44 

35512-46 0.92 

59144-32 1.16 

No Batch EPA Reg. No. % Active Ingredient 

100-827 Atrazine: 28.7 

S-Metolachlor: 35.8 

100-928 Atrazine: 23.3 

Flumetsulam: 1.0 

S-Metolachlor: 29.1 

100-956 Atrazine: 74.93 

Prosulfuron: 1.78 

100-962 Atrazine: 25.7 

Glyphosate: 18.0 

239-2618 14.0 

241-353 Atrazine: 32.54 

Imazethapyr: 4.36 

264-573 Atrazine: 43.2 

Isoxaflutole: 3.2 

264-668 Atrazine: 33.42 

Glufosinate-ammonium: 10.00 

270-288 23.6 

352-585 Atrazine: 86.78 

Nicosulfuron: 1.34 

Rimsulfuron: 1.34 

524-329 Atrazine: 16.3 

Alachlor: 27.2 

282
No Batch EPA Reg. No. % Active Ingredient 

524-418 Atrazine: 15.3 

Alachlor: 27.05 

524-480 Atrazine: 18.3 

Acetochlor: 46.3 

524-485 Atrazine: 26.9 

Acetochlor: 33.4 

524-509 Atrazine: 20.9 

Glyphosate: 20.9 

524-511 Atrazine: 14.5 

Acetochlor: 29.0 

3125-523 Atrazine: 50.5 

Flufenacet: 19.6 

Metribuzin: 4.9 

7969-192 Atrazine: 35.3 

Dimethenamid-P: 18.2 

7969-200 Atrazine: 29.5 

Dimethenamid-P: 24.1 

19713-6 80.0 

19713-171 Atrazine: 21.42 

Simazine: 21.41 

34704-728 Atrazine: 25.00 

2,4-D: 16.58 

42750-50 Atrazine: 21.62 

Bromoxynil: 15.74 

62719-368 Atrazine: 21.1 

Acetochlor: 31.6 

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284
Appendix H: ATRAZINE MONITORED WATERSHEDS 

LA1047002 Iberville Water Works District #3 Louisiana 

MO1010204 Dearborn Missouri 

IL1170400 Gillespie Illinois 

KY0280267 Marion Water Department Kentucky 

KY0710247 Lewisburg Water Works Kentucky 

IA5903011 Chariton Municipal Water Works Iowa 

MO2010112 Bucklin Missouri 

IN5299001 Batesville Water Utility Indiana 

285