2

Simazine Preliminary Work Plan – Table of Contents 

Overview 3 

Anticipated Data Needs 4 

Statutory and Regulatory Authority 4 

Simazine Facts 5 

Use and Usage Information 5 

Recent Actions 7 

Anticipated Risk Assessments for Registration Review 7 

Timeline 9 

Next Steps 10 

Appendix – Additional Areas Considered in the Simazine Registration Review 11 

References:

This Preliminary Work Plan summarizes the Environmental Protection Agency's current position 

based on the following documents: 

1. Registration Review – Preliminary Problem Formulation for the Ecological Risk 

Assessment for Simazine. F. Farruggia. May 28, 2013. 

2. Atrazine, Propazine, and Simazine. Human Health Risk Scoping Document in Support of 

Registration Review. W. Donovan. June 4, 2013 

3. Atrazine, Propazine, and Simazine: Review of Human Incident Reports. S. Recore. 

January 22, 2013. 

4. BEAD Chemical Profile for Registration Review: Simazine. B. Phillips. February 1, 2013.

5. Simazine Screening Level Usage Analysis. March 16, 2012.

6. PRD Label Data Report: Food/Feed & Non-Food/Non-Feed Uses Considered in 

Registration Review Work Planning. January 14, 2013.

These and other supporting documents for the simazine registration review case may be found in 

the docket EPA-HQ-OPP-2013-0251 at http://www.regulations.gov. 
3

OVERVIEW

The docket for simazine is now open, initiating the first public comment period for this 

registration review (docket number EPA-HQ-OPP-2013-0251). Simazine is a non-selective 

systemic triazine herbicide registered for use for pre- and post-emergent applications to control 

annual and perennial grasses and broadleaf weeds on a variety of crops, such as oranges and 

corn; and non-agricultural use sites, such as residential turf. For human health risk assessment, 

simazine is part of the triazine common mechanism group based on a common toxicity end-point 

and known mechanism of toxicity. The triazine common mechanism group consists of the 

pesticide active ingredients atrazine, simazine, propazine, and the metabolites desethyl-s-atrazine 

(DEA), desisopropyl-s-atrazine (DIA), and diaminochlorotriazine (DACT).1

 This Preliminary 

Work Plan (PWP) document explains what EPA's Office of Pesticide Programs knows about 

simazine, highlighting anticipated data and assessment needs, identifying the types of 

information that would be especially useful to the Agency in conducting the review, and 

providing an anticipated timeline for completing the registration review for simazine. 

 

The registration review process was designed to include a public participation component to 

solicit input from interested stakeholders. The Agency intends, by sharing this information in the 

docket, to inform the public of what it knows about simazine and what types of new data or other 

information would be helpful for the Agency to receive as it moves toward a decision on 

simazine. The Agency encourages all interested stakeholders to review the PWP and Appendix 

and to provide comments and additional information that will help the Agency’s decisionmaking process for simazine. In addition to general areas on which persons may wish to 

comment, there are some areas identified in the PWP and Appendix about which the Agency 

specifically seeks comments and information. Interested stakeholders could include: 

environmental non-profit or interest groups; pesticide manufacturers; agricultural labor or 

commodity groups; commercial, institutional, residential, and other users of pesticides; or the 

public at large. 

The Preliminary Work Plan begins by listing the anticipated data needs for simazine. Next, it 

discusses the statutory and regulatory authority for Registration Review. Then the document 

provides simazine facts, use and usage information, recent actions, the anticipated risk 

assessments, and a projected registration review timeline for simazine. Finally, the Appendix to 

this document includes identification and discussion of some areas that are considered generally 

in Registration Review along with some additional simazine case-specific information. 

 

 

1

 There are other triazine pesticides, such as ametryn, prometryn, and prometon, but they are excluded from the 

triazine common mechanism group because they do not share the same toxicity profile. (Triazine Cumulative 

Risk Assessment. J. Morales. March 28, 2006.) 
4

ANTICIPATED DATA NEEDS

Table 1 below summarizes anticipated data needs for simazine. For additional discussion of the 

anticipated data needs, see the Registration Review – Preliminary Problem Formulation for the 

Ecological Risk Assessment for Simazine and Atrazine, Propazine and Simazine. Human Health 

Risk Scoping Document in Support of Registration Review. 

Table 1: Anticipated Data Needs for the Simazine Registration Review 

Guideline 

Number1 Study Title1

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

850.6100

Environmental chemistry methods (ECM) and 

associated independent laboratory validation 

(ILV) for soil2 

TGAI 12

TGAI = technical grade active ingredient 

1

 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850 – Ecological Effects Tests 

– including renumbering and other designations or changes for some guideline studies. See “Final Test 

Guidelines; OCSPP 850 Series; Notice of Availability” 77 FR 38282, June 27, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0154-0028 2

ECM and ILVs are used in the testing and identification of chemicals. 

STATUTORY AND REGULATORY AUTHORITY

The Food Quality Protection Act (FQPA) of 1996 mandated a registration review program. All 

pesticides distributed or sold in the United States (U.S.) generally must be registered by the 

Environmental Protection Agency (EPA or the Agency), based on scientific data showing that 

they will not cause unreasonable risks to human health or the environment when used as directed 

on product labeling. The registration review program is intended to make sure that, as the ability 

to assess risk evolves and as policies and practices change, all registered pesticides continue to 

meet the statutory standard of no unreasonable adverse effects to human health or the 

environment. Changes in science, public policy, and pesticide use practices will occur over time. 

Through the registration review program, the Agency periodically reevaluates pesticides to make 

sure that as change occurs, products in the marketplace can be used safely. Information on this 

program is provided on EPA’s website.2

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. The regulations governing registration review begin at 40 CFR 155.40. The 

Agency will consider benefits information and data as required by FIFRA. The public phase of 

registration review begins when the initial docket is opened for each case. The docket is the 

Agency’s opportunity to state what it knows about the pesticide and what additional risk analyses 

and data or information it believes are needed to make a registration review decision. After 

 

2

 http://www.epa.gov/oppsrrd1/registration_review/ 
5

reviewing and responding to comments and data received in the docket during this initial 

comment period, the Agency will develop a Final Work Plan (FWP) and anticipated schedule for 

the registration review of simazine. 

SIMAZINE FACTS

Table 2 provides a summary of the chemical facts for simazine. 

Table 2: Chemical Facts for Simazine

PC code 080807 

Case Number 7280 

CAS Number 122-34-9 

Year first registered 1957 

Pesticide Type Herbicide 

Chemical class Triazine 

Reregistration Eligibility 

Decision (RED) 

April 2006 

Tolerance Reassessment 

Eligibility Decision 

(TRED) 

N/A 

Cumulative group Triazine. The most recent human health cumulative risk 

assessment was completed in March 2006. (Triazine Cumulative 

Risk Assessment. J. Morales. March 28, 2006.) 

40 CFR Citation Tolerances for simazine are established in 40 CFR §180.213 

Dual-use Simazine is registered for conventional pesticidal uses only and has 

no registered antimicrobial or biopesticidal uses. 

Non-pesticidal uses There are no identified non-pesticidal uses of simazine 

Pesticide Re-evaluation 

Division, Simazine 

Review Manager 

Molly Clayton 

clayton.molly@epa.gov

703-603-0522 

Registration Division, 

Product Manager 

Kable Bo Davis 

davis.kable@epa.gov

703-306-0415 

USE AND USAGE INFORMATION

Table 3 summarizes the use and usage information for simazine. Please see BEAD Chemical 

Profile for Registration Review: Simazine in the registration review docket for more details. 

Table 3: Simazine Use and Usage Information

Summary of Use Simazine is a non-selective systemic triazine herbicide that can be 

applied postemergence to weeds as a foliar-applied herbicide; 

however since it is readily absorbed through the root system, it is 

primarily applied as a pre-plant incorporated or soil applied 

herbicide. It is also registered for use on non-agricultural use sites.
6

Table 3: Simazine Use and Usage Information

Use Sites Agricultural: Registered for use on crops including but not limited 

to pome fruits, broccoli, brussel sprouts, cranberry, persimmon, 

strawberries, caneberries, grapes, citrus fruits, nut crops, stone 

fruits, artichokes, corn, asparagus, kale, cabbage, blueberries, 

alfalfa, avocado, and olives. 

Non-agricultural: Registered use sites include but are not limited to

forest trees, ornamental plants, ornamental ponds and aquaria, 

uncultivated agricultural areas, residential and golf course turf, 

Christmas tree farms, nursery stock, building perimeters, and 

shelterbelt plantings. 

Summary of Usage Agricultural: During the time period of 1998-2011, the annual total 

agricultural usage of simazine averaged approximately 6 million 

pounds active ingredient (a.i.) to treat approximately 4 million 

acres. During this time frame, the crops with the highest use in 

terms of percent of total pounds of active ingredient applied and 

acres treated were corn and oranges. 

Non-agricultural: The most recent non-agricultural usage data 

available to the EPA (2002-2006) indicate approximately 400,000 

pounds of simazine a.i. are applied to non-agricultural use sites per 

year. 

Formulation Type(s) Simazine is formulated either as a liquid, emulsifiable concentrate, 

dry flowable or a flowable concentrate.

Application Method(s) Applied by aerial and ground broadcast, band application, 

chemigation, and spot treatment.

Technical Registrant(s) Syngenta Crop Protection, LLC; Oxon Italia S.P.A.; Drexel 

Chemical Company 

No. of Registrations 22 Section 3 and 12 Section 24c (special local needs) registrations3

Restricted Use No 

Guidance for Commenters: Additional areas of use and usage related information

requested for this registration review, and of particular interest to EPA, are described below. 

 Certain simazine labels are unclear with respect to application parameters such as the size 

of the treated area, the extent of a treated “spot,” retreatment intervals, or maximum 

annual application rates. In the lack of further information, EPA expects to use 

conservative assumptions to approximate these parameters in order to conduct a 

quantitative risk assessment. However, the Agency will work with registrants to clarify 

information on simazine product labels, especially the maximum annual application rates 

for non-agricultural uses including golf courses, turf, and ornamental lawns. 

 

3

 Section 3 product labels can be obtained from the Pesticide Product Label System (PPLS) website 

(http://oaspub.epa.gov/pestlabl/ppls.home). 
7

 Confirmation of the following label information: sites of application; formulations; 

application methods and equipment; maximum application rates; frequency of 

application, application intervals, and maximum number of applications per season; and 

geographic limitations on use. 

 Use distribution (e.g., acreage and geographical distribution of relevant use sites). 

 Median and 90th percentile reported use rates (lbs ai/A) from usage data – national, state, 

and county. 

 Typical application timing (date of first application and application intervals) – national, 

state, and county. 

 Usage/use information for non-agricultural uses. 

 Typical application interval (days). 

 State or local use restrictions. 

 Foreign technical registrants not listed above who supply technical simazine to the US 

market. 

RECENT AND PENDING ACTIONS

The 2006 Simazine RED, which included a Memorandum of Agreement (MOA), and subsequent 

Data Call-In Notice (DCI), issued in 2007, required the registrants to establish an on-going 

drinking water monitoring program, called the Simazine Monitoring Program (SMP). The 

technical registrants for simazine are required to conduct an annual review of all Safe Drinking 

Water Act (SDWA) data for simazine to determine if any community water systems (CWS) have 

a drinking water annual average concentration of simazine-based Total Chlorotriazine (TCT) 

concentration at 2.6 parts-per-billion (μg/L or ppb) or greater as a criterion for participation in 

the SMP. SMP monitoring samples are analyzed for simazine, atrazine, and their chlorinated 

degradates, as all are considered equally toxic to humans. Currently, 7 CWS are included in the 

SMP. More specific details concerning the SMP may be found in the simazine RED. As new 

data become available, EPA conducts reviews of the registrant-submitted water monitoring data 

and other water monitoring programs looking for simazine, such as U.S. Geological Survey’s 

(USGS’s) National Water-Quality Assessment Program (NAWQA) and state monitoring 

programs. 

The Agency is currently reviewing a request, dated March 28, 2012, submitted by a technical 

registrant for simazine, Syngenta Crop Protection, LLC, to remove 5 of the 7 CWS from the 

SMP. The request states that these 5 sites are eligible for removal from the SMP under the terms 

established by the MOA, since five consecutive years have passed without any 90-day rolling 

average concentration of simazine and its two chlorinated degradates meeting or exceeding 37.5 

ppb. EPA expects to complete its review of this request in summer 2013. 

The Agency is currently evaluating a tolerance petition for simazine (2F8006, 77 FR 50686) to 

establish crop group tolerances for stone fruit, pome fruit, citrus fruit, and tree nuts, and to 

remove individual tolerances which would be replaced by the new crop groups. EPA is in the 

process of reviewing this request which will likely necessitate an updated assessment for the 

triazine cumulative group. 

 
8

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW

The most recent comprehensive human health risk assessment for simazine was completed in 

2006 in preparation for the Reregistration Eligibility Decision. The most recent ecological and 

environmental fate risk assessment was completed in 2005 for the same purpose. Findings and 

conclusions from these risk assessments are summarized in the Registration Review – 

Preliminary Problem Formulation for the Ecological Risk Assessment for Simazine and Atrazine, 

Propazine, and Simazine; Human Health Risk Scoping Document in Support of Registration 

Review. 

During registration review, the Agency anticipates the need to conduct a comprehensive 

ecological risk assessment, including an endangered species assessment, for all uses of simazine. 

For human health, EPA anticipates the need to conduct revised dietary, residential, and 

occupational, and cumulative risk assessments during registration review. If toxicological 

endpoints or points of departure are revised, they will be considered in the new assessments, as 

well as any changes to the standard operating procedures or default exposure assumptions. 

Table 4 below summarizes the anticipated registration review risk assessments based on the 

EFED Problem Formulation and HED Scoping Document. 

Table 4: Anticipated Risk Assessments for the Simazine Registration Review 

Type of Risk Assessment Conduct? Notes 

Ecological and Environmental Fate 

Comprehensive ecological 

(species to be assessed 

include terrestrial and aquatic 

organisms), including 

endangered species 

Y The stressors of concern for terrestrial organisms are 

parent simazine and the degradate DIA. The stressor 

of concern for aquatic organisms is parent simazine 

alone. For additional information, see page 23 of the 

Problem Formulation. 

Incidents Will check for 

updates 

For a discussion of reported ecological incidents for 

simazine, see page 21 of the Problem Formulation. 

Human Health 

Dietary 

Food Y During registration review, an updated dietary 

assessment may be conducted to include any updates 

to toxicological endpoints, dietary exposure estimates, 

and changes to assessment SOPs. 

Drinking water Y EPA intends to use the data collected in the SMP in 

its drinking water assessment for simazine during 

registration review. EPA also intends to use data 

collected in the Atrazine Monitoring Program (AMP) 

in the drinking water assessment for simazine, as 

simazine is also detected in water samples analyzed 

for the AMP. 
9

Occupational 

Handlers (mixers, loaders, 

applicators) 

Y Since the most recent occupational risk assessment 

for simazine was conducted, EPA finalized new 

occupational risk assessment standard operating 

procedures (SOPs), including new potential exposure 

scenarios applicable to simazine that were not 

previously assessed (e.g. handheld equipment for turf 

and ornamentals). During registration review, EPA 

anticipates updating all relevant occupational 

exposure scenarios, along with any changes to 

toxicity endpoints and/or safety factors. 

Post-application Y 

Residential 

Handlers Y Since the most recent residential assessment for 

simazine was conducted, new residential risk 

assessment procedures containing additional turf 

scenarios have been finalized. During registration 

review, EPA anticipates updating all relevant 

residential handler and post-application assessments, 

along with any changes to toxicity endpoints and/or 

safety factors. 

Post-application Y 

Other 

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures. 

Cumulative Y An assessment of the triazine cumulative group is 

expected as part of registration review. 

Tolerances Y Tolerances are established under 40 CFR §180.213 

for the combined residues of simazine and its two 

chlorinated metabolites in/on a variety of crops and 

livestock commodities. EPA anticipates updating the 

residue definition for the tolerance expression for 

simazine in accordance with current policy on 

tolerance definitions. 

Incidents Will check for 

updates 

For a discussion of reported human incidents for 

simazine, see page 12 of the Scoping Document and 

the Atrazine, Propazine, and Simazine: Review of 

Human Incident Reports. 

TIMELINE

EPA has created the following estimated timeline for the completion of the simazine registration 

review in Table 5 below. 

Table 5: Projected Simazine Registration Review Timeline

Activities Estimated Date

Opening the Docket 

Open Docket and 60-day Public Comment Period 2013 – June 
10

Table 5: Projected Simazine Registration Review Timeline

Activities Estimated Date

Close Public Comment 2013 – August 

Case Development 

Final Work Plan 2013 – November 

Issue DCI 2014 – July - September 

60-day Public Comment Period for Draft Risk Assessments4,5 2015 – April - June 

Data Submission 2016 – July - September 

Registration Review Decision 

60-day Public Comment Period for Proposed Registration Review 

Decision 

2015 – Oct. - Dec. 

Registration Review Decision and Begin Post-Decision Follow-up 2016 

Total (years) 3 

NEXT STEPS

After the 60-day public comment period closes, the Agency will review and respond to any 

comments received in a timely manner and then issue a Final Work Plan for the registration 

review of simazine. 

 

 

4

 The registration review schedule for most conventional pesticides includes a 6 month period after the Final Work 

Plan to issue a data call-in and then an appropriate time period for the required data to be submitted to EPA. 

However, because the one anticipated data requirement for simazine, Guideline 850.6100 (environmental chemistry 

methods and associated independent laboratory validation for soil), will not affect the preliminary risk assessments 

for simazine registration review, the schedule has been modified as appropriate. 

5

 The regulations governing Registration Review generally require the Agency to provide a public comment period 

of at least 30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the 

Agency plans to provide a 60 calendar day public comment period for draft risk assessments. 
11

Appendix – Additional Areas Considered in the Simazine Registration Review

PUBLIC COMMENTS AND FEEDBACK:

Guidance for Commenters: The areas below highlight topics of special interest to the Agency 

where your comments, data submissions, or reference to sources of additional information could 

be of particular use.

Trade Irritants: 

Through the registration review process, the Agency intends to solicit information on trade 

irritants and, to the extent feasible, take steps toward facilitating irritant resolution. The Agency 

will work to harmonize tolerances and international maximum residue limits (MRLs) and may 

modify tolerance levels to do so, when possible. Growers and other stakeholders are asked to 

comment on any trade irritant issues resulting from lack of MRLs or disparities between U.S. 

tolerances and MRLs in key export markets, providing as much specificity as possible regarding 

the nature of the concern 

Water Quality: 

Simazine is identified as a cause of impairment, as defined under section 303(d) of the Clean 

Water Act, for three water bodies in California, based on information provided at EPA’s 

website.6

 Total Maximum Daily Loads (TMDLs) are needed for simazine for one impaired 

water body in Oregon and one in Michigan, based on information provided at the website.7 

More information on impaired water bodies and TMDLs can be found at EPA’s website.8

 The 

Agency invites submission of water quality data for this pesticide. To the extent possible, 

data should conform to the quality standards in Appendix A of the OPP Standard Operating 

Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process9

 in order to ensure they can be 

used quantitatively or qualitatively in pesticide risk assessments. 

Environmental Justice: 

EPA seeks to achieve environmental justice, the fair treatment and meaningful involvement of all 

people, regardless of race, color, national origin, or income, in the development, implementation, 

and enforcement of environmental laws, regulations, and policies. To help address potential 

environmental justice issues, the Agency seeks information on any groups or segments of the 

population who, as a result of their location, cultural practices, or other factors, may have 

atypical, unusually high exposure to simazine compared to the general population. Please 

comment if you are aware of any sub-populations that may have atypical, unusually high 

exposure compared to the general population.

 

6 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

7

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_

group_name=PESTICIDES

8 http://www.epa.gov/owow/tmdl/

9 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
12

ENDANGERED SPECIES:

A risk assessment that supports a complete endangered species determination has not been 

conducted for simazine. The ecological risk assessment planned during registration review will 

allow the Agency to determine whether use of simazine has “no effect” or “may affect” federally 

listed threatened or endangered species (listed species) or their designated critical habitats. 

When an assessment concludes that a pesticide’s use “may affect” a listed species or its 

designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife Service 

and/or National Marine Fisheries Service (the Services), as appropriate. 

ENDOCRINE DISRUPTOR SCREENING PROGRAM: 

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its reregistration decision for simazine, EPA reviewed these data 

and selected the most sensitive endpoints for relevant risk assessment scenarios from the existing 

hazard database. However, as required by FFDCA section 408(p), simazine is subject to the 

endocrine screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. Simazine was 

included on that list and has been issued an order to conduct the Tier 1 testing. Once all required 

Tier 1 and Tier 2 data have been received and reviewed, the endpoints and safety factors used for 

risk assessment purposes will be examined and a new risk assessment performed if necessary. 

For further information on the status of the EDSP, the policies and procedures, the list of 67 
13

chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our 

website.10

HUMAN STUDIES:

Occupational and Residential 

Past simazine risk assessments rely in part on data from studies in which adult human subjects 

were intentionally exposed to a pesticide to determine their dermal and inhalation exposure. 

Many such studies, involving exposure to many different pesticides, comprise generic pesticide 

exposure databases such as the Pesticide Handlers Exposure Database (PHED), the Agricultural 

Reentry Task Force (ARTF) Database, and the Outdoor Residential Exposure Task Force 

(ORETF) Database. EPA has reviewed all the studies supporting these multi-pesticide generic 

exposure databases, and has found no clear and convincing evidence that the conduct of any of 

them was either fundamentally unethical or significantly deficient relative to the ethical 

standards prevailing at the time the research was conducted. All applicable requirements of 

EPA’s Rule for the Protection of Human Subjects of Research (40 CFR Part 26) have been 

satisfied, and there is no regulatory barrier to continued reliance on these studies. 

AGRICULTURAL HEALTH STUDY:

Simazine is among several agricultural chemicals included in the Agricultural Health Study 

(AHS). The AHS began in 1993 and is a collaboration of the National Institute of 

Environmental Health Sciences (NIEHS), the National Cancer Institute (NCI), the EPA, and the 

National Institute for Occupational Safety and Health (NIOSH). Designed as a large long-term 

epidemiological study, the AHS collects and analyzes data on the health and work practices of 

nearly 90,000 farmers and their families in Iowa and North Carolina who enrolled in the study 

before any disease developed. The study focuses particularly on farmers' exposure to 50 

chemicals including many of the most widely used pesticides. As data are collected over a 

period of years, scientists can compare overall health outcomes for people who differ in whether 

they have had exposure to various chemicals. While these comparisons cannot conclusively 

demonstrate how exposure affects health, they can show some statistical associations. More 

information on the AHS can be found at: http://aghealth.nci.nih.gov. EPA is monitoring the 

results of the AHS and will consider this study in the registration review of simazine as 

appropriate. 

 

10 http://www.epa.gov/endo/