2

Oxadiazon Preliminary Work Plan – Table of Contents 

OVERVIEW ................................................................................................................................... 3

ANTICIPATED DATA NEEDS .................................................................................................... 4

STATUTORY AND REGULATORY AUTHORITY ................................................................... 6

CHEMICAL FACTS ...................................................................................................................... 6

USE AND USAGE INFORMATION ............................................................................................ 7

RECENT ACTIONS ....................................................................................................................... 9

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW ................................ 9

TIMELINE .................................................................................................................................... 12

NEXT STEPS ............................................................................................................................... 13

Appendix – Additional Areas Considered in the Oxadiazon Registration Review .................. 14 

References:

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

based on the following documents: 

1. EFED Registration Review Problem Formulation for Oxadiazon. Yingling, H.; Ruhman, 

M. December 5, 2014. 

2. Oxadiazon. Human Health Scoping Document in Support of Registration Review. 

Collantes, M.; Hansen, L.; Swartz, C. December 5, 2014. 

3. Oxadiazon: Tier 1 Review of Human Incidents. Evans, E.; Recore, S. November 5, 2014. 

4. BEAD Chemical Profile (BCP) for Registration Review: Oxadiazon (109001). Ratnayake, 

S.; Atwood, D.; Smearman, S. September 23, 2014.

5. 109001 Oxadiazon EFED Label Data Report. July 24, 2014.

6. 109001 Oxadiazon HED Master Label Report. July 24, 2014.

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

in the docket EPA-HQ-OPP-2014-0782 at http://www.regulations.gov. 
3

OVERVIEW 

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

registration review (docket number EPA-HQ-OPP-2014-0782). Oxadiazon is a selective 

herbicide that is registered for use as pre- and early post-emergence treatments for the control of 

many annual broadleaf and grass weeds. It was first registered in the U.S. in 1978. Today, major 

use sites of oxadiazon are established or newly established bermudagrass, perennial ryegrass, 

fescue turf, and various ornamentals including landscape ornamental beds. There are no 

registered food or feed uses for oxadiazon. This Preliminary Work Plan (PWP) document 

explains what EPA's Office of Pesticide Programs knows about oxadiazon, 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 oxadiazon. 

 

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 oxadiazon and what types of new data or 

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

oxadiazon. 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 this chemical. 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 oxadiazon. Next, it 

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

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

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

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

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

 
4

ANTICIPATED DATA NEEDS 

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

anticipated data needs, see the EFED Registration Review Problem Formulation for Oxadiazon

and Oxadiazon. Human Health Scoping Document in Support of Registration Review.. 

Table 1: Anticipated Data Needs for the Oxadiazon Registration Review 

Guideline 

(GDLN) 

Number1

Study Title1 

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

or Status 

835.4100 Aerobic soil metabolism TGAI 24 

850.2100 Avian oral toxicity (passerine species) TGAI 12 

850.4550 Cyanobacteria toxicity TEP 12 

850.6100 Terrestrial field dissipation study (for turf) TEP 24 

850.6100 

Environmental chemistry methods and 

associated independent laboratory validations 

for the parent, oxadiazon, and three of its 

metabolites (methoxy, phenolic, and 

carboxylic) in soil/sediment and water 

TGAI and three 

metabolites 12 

Non-GDLN 

Special Study 

Acute oral toxicity to adult honey bees 

(OECD 213) TGAI 12 

Non-GDLN 

Special Study 

Acute oral toxicity to larval honey bees 

(OECD 237) TGAI 12 

Non-GDLN 

Special Study Chronic oral toxicity to adult honey bees TGAI 12 

Non-GDLN 

Special Study Chronic oral toxicity to larval honey bees TGAI 12 

Non-GDLN 

Special Study 

Pollinator feeding/semi-field/pollen and 

nectar residue studies2 TEP 24 

850.3040 Field testing for pollinators2 TEP 36 

870.3465 28-day inhalation toxicity TGAI 12 

875.2100 Dislodgeable foliar residue and turf 

transferable residues TGAI 12 

 

 

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

 The need for this anticipated data requirement is contingent on results of the tier 1 bee studies (including acute oral 

toxicity to adult honey bees, acute oral toxicity to larval honey bees, chronic oral toxicity to adult honey bees, and 

chronic oral toxicity to larval honey bees). 
5

Outstanding Data Requirements from GDCI-109001-247333

835.4300 Aerobic aquatic metabolism (address unidentified/un-extracted residue) TGAI 

Supplemental 

(MRID 

46594701) 

850.1350 

Mysid chronic toxicity test – life-cycle 

toxicity with Mysids (America mysis, 

formerly Mysidopsis bahia) 

TGAI 

In review 

(MRID 

46473304) 

850.1400 

Freshwater fish early-life stage (raw data for 

the previously submitted study with rainbow 

trout) 

TGAI 

In review 

(MRID 

41811601) 

850.4100 Terrestrial plant toxicity, seedling emergence TEP Outstanding 

850.4150 Terrestrial plant toxicity, vegetative vigor TEP Outstanding 

850.1735 

Whole sediment acute toxicity freshwater 

invertebrates: toxicity to freshwater 

amphipods (Hyalella azteca) during a 10-day 

sediment exposure 

TGAI 

In review 

(MRID 

46473303) 

850.1740 

Whole sediment acute toxicity freshwater 

invertebrates: toxicity to midge (Chironomus 

riparius) during a 10-day sediment exposure

TGAI 

In review 

(MRID 

46487301) 

Non-GDLN 

Special Study 

Freshwater fish early life-stage toxicity test 

with fathead minnow (Pimephales promelas) 

under high light conditions 

TGAI 

In review 

(MRID 

48759101) 

TGAI = technical grade active ingredient; TEP = typical end-use product 

 

 

3

 The studies listed in this section were previously required through a generic data call-in issued in November 2004 

and are still outstanding, or in review. These studies will not be included in the anticipated Registration Review 

DCI because they are already required through the earlier DCI. 
6

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.4

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 

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 oxadiazon. 

CHEMICAL FACTS 

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

Table 2: Chemical Facts for Oxadiazon

PC code 109001 

Case Number 2485 

CAS Number 19666-30-9 

Year first registered 1978 

Pesticide Type Light-dependent peroxidizing herbicide (LDPH) 

Chemical class Oxadiazolone 

Reregistration Eligibility 

Decision (RED) 

2003 

Tolerance Reassessment 

Eligibility Decision 

(TRED) 

Not applicable; tolerance reassessment was included in the RED. 

Cumulative group Not applicable; oxadiazon has not been identified as a member of 

a cumulative group that shares a common mechanism of toxicity. 

 

4

 http://www.epa.gov/oppsrrd1/registration_review/ 
7

Table 2: Chemical Facts for Oxadiazon

40 CFR Citation There are no established tolerances for oxadiazon. 

Dual-use Oxadiazon 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. 

Pesticide Re-evaluation 

Division, Chemical 

Review Manager 

Katherine St. Clair, stclair.katherine@epa.gov, 703-247-8778 

Registration Division, 

Product Manager 

Shaja Joyner, joyner.shaja@epa.gov, 703-308-3194 

USE AND USAGE INFORMATION 

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

Chemical Profile (BCP) for Registration Review: Oxadiazon (109001) in the registration review 

docket for more details. 

Table 3: Oxadiazon Use and Usage Information

Summary of Use Oxadiazon is a selective herbicide that is registered for use as preand early post-emergence treatments for the control of many 

annual broadleaf and grass weeds. Specific target weeds include 

crabgrass, goosegrass, annual bluegrass, and annual sedge. 

Use Sites Agricultural use sites: Oxadiazon is not registered for use on 

agricultural use sites, and there are no registered food or feed uses 

or anticipated food or feed uses for oxadiazon. The registered use 

sites for oxadiazon are considered non-agricultural. 

Non-agricultural use sites: Major use sites of oxadiazon are 

established or newly established bermudagrass, perennial 

ryegrass, fescue turf, and various ornamentals including landscape 

ornamental beds. Oxadiazon is registered for commercial use on 

turf grown in golf courses and in areas such as 

apartment/condominium complexes, parks, athletic fields, 

playgrounds, and cemeteries. In addition, oxadiazon is used on 

sod farms and on conifer nurseries and landscapes (i.e. industrial 

sites, ornamental, roadside plantings, woody, ornamental shrubs, 

vines and trees, and herbaceous ornamentals). 

Summary of Usage EPA has very limited usage data for oxadiazon due to its nonagricultural use pattern. Data for oxadiazon use on nonagricultural sites is limited to proprietary data. Based on 2012 

data, the usage of oxadiazon on non-agricultural use sites totaled 

approximately 273,000 pounds of active ingredient and the 

primary non-agricultural use site was golf courses with 

approximately 78% of oxadiazon use, followed by landscape sites 
8

Table 3: Oxadiazon Use and Usage Information

(7%), institutional turf (6%), and turf (5%). Data for earlier or 

more recent years were not available. 

Formulation Type(s) Oxadiazon can be formulated as a granular product, wettable 

powder, emulsifiable concentrate, water soluble packets, or can be 

mixed with fertilizer. 

Application Method(s) Products can be applied by ground using spreader/granular 

applicator or calibrated sprayer. 

Technical Registrant(s) Bayer Environmental Science; Nufarm Limited. 

No. of Registrations 62 Section 3 registrations (2 technical products, 2 manufacturing 

use products, 58 end-use products)5

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. 

 EPA requests that the registrant provide the name, toxicity, structure, and CAS number 

for each of the degradates listed in Section 5 of the EFED Problem Formulation. 

 EPA requests that the registrants confirm their intentions regarding oxadiazon turf and 

lawn uses. If the registrants’ intentions are to restrict the use of oxadiazon on residential 

or home lawns/turf, then a residential handler exposure assessment is not required during 

registration review for these uses. However, if a site is restricted, then neither 

‘residential’ nor ‘occupational’/’commercial’ handlers may apply the specified product to 

the site. If the registrant intends to allow occupational/commercial handlers to apply 

oxadiazon to residential turf and lawns, then they cannot restrict the use on residential 

lawns by homeowners, and a residential handler assessment for turf/lawn will need to be 

conducted. 

 Certain oxadiazon labels are unclear with respect to application parameters. Without 

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 oxadiazon product labels, especially the 

maximum annual application rates for non-agricultural uses including golf courses, turf, 

and ornamental lawns. 

 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. 

 

5

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

(http://oaspub.epa.gov/pestlabl/ppls.home). 
9

 The following usage/use information for non-agricultural uses: total pounds a.i. applied; 

percent crop/site treated; application rates (typical and maximum); frequency of 

application by region of the country; methods of application; target or niche pests; 

efficacy in formation/product performance. 

 Typical application interval (days). 

 State or local use restrictions. 

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

market. 

RECENT ACTIONS 

The RED for oxadiazon was completed in 2003, and the product reregistration process was 

completed in 2009. 

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW 

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

2007 for a new use on residential landscape ornamentals by professional landscape personnel. 

The most recent ecological and environmental fate risk assessment was completed in 2001 for 

the oxadiazon Reregistration Eligibility Decision. Findings and conclusions from these risk 

assessments are summarized in the EFED Registration Review Problem Formulation for 

Oxadiazon and Oxadiazon. Human Health 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 

oxadiazon. For human health, EPA anticipates the need to conduct revised dietary (drinking 

water only), residential, and occupational risk assessments during registration review; EPA also 

anticipates re-evaluating the need for an aggregate (combined drinking water and residential) 

assessment based on currently available information and science/risk assessment policies. If 

toxicological endpoints or points of departure are revised based on the data that are anticipated to 

be required for registration review, they will be considered in the new assessments, as will 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. 
10

Table 4: Anticipated Risk Assessments for the Oxadiazon 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 

Yes EPA anticipates conducting an updated 

comprehensive ecological risk assessment during 

registration review. The new assessment will 

incorporate the most up-to-date modeling 

methodologies, updated toxicological endpoints, and 

data submitted under the anticipated registration 

review data call-in. 

Incidents Will check for 

updates 

For a discussion of reported ecological incidents for 

oxadiazon, see page 14 of the Problem Formulation. 

Human Health 

Dietary 

Food No There are no registered food uses for oxadiazon. EPA 

does not anticipate conducting an updated dietary 

assessment for registration review unless there are 

significant changes to the drinking water estimated 

concentrations or if there are significant changes to 

the points of departure, uncertainty factors, or safety 

factors. 

Drinking water Yes EPA anticipates conducting an updated drinking 

water assessment during registration review to 

incorporate updated estimated drinking water 

concentrations. 

Occupational 

Handlers (mixers, loaders, 

applicators) 

Yes The most recent occupational exposure assessment 

was conducted for the 2007 human health risk 

assessment. EPA anticipates conducting an updated 

occupational handler assessment during registration 

review. 

Post-application Yes The most recent occupational exposure assessment 

was conducted for the 2007 human health risk 

assessment. EPA anticipates conducting an updated 

occupational post-application assessment during 

registration review. 

Residential 
11

Handlers Yes A residential handler assessment has not been 

performed. EPA anticipates conducting a residential 

handler risk assessment during registration review if 

the registrants intend to support use of oxadiazon on 

residential property. 

In the 2007 human health assessment for ornamentals 

and landscape use, it was assumed that there would be 

no residential handler exposure since the product 

could only be applied by professional landscape 

personnel (in accordance with the label). However, 

since the oxadiazon labels do not identify the end-use 

products as restricted use, a residential handler 

exposure assessment is now required to be protective 

of potential homeowners who apply oxadiazon to 

ornamentals. 

Regarding lawn/turf use of oxadiazon, EPA requests 

that the registrants confirm their intentions for these 

uses. If the registrants’ intentions are to restrict the 

use of oxadiazon on residential or home lawns/turf, 

then a residential handler exposure assessment is not 

required during registration review for lawn and turf 

uses. However, if a site is restricted, then neither 

‘residential’ nor ‘occupational’/’commercial’ handlers 

may apply the specified product to the site. If the 

registrant intends to allow occupational/commercial 

handlers to apply oxadiazon to residential turf and 

lawns, then they cannot restrict the use on residential 

lawns by homeowners, and a residential handler 

assessment for turf/lawn will need to be conducted. 

Post-application Yes The most recent residential post-application exposure 

assessment was conducted for the 2007 human health 

risk assessment. EPA anticipates conducting an 

updated residential post-application assessment 

during registration review. 

Other 

Aggregate No An aggregate assessment evaluates the combined risk 

from dietary and residential exposures. Due to the 

lack the of food uses, an aggregate assessment is not 

appropriate for oxadiazon. However, the Agency will 

determine if it is appropriate to consider the combined 

exposure from drinking water and residential sources. 

Cumulative No Not applicable; oxadiazon has not been identified as a 

member of a cumulative group that shares a common 

mechanism of toxicity. 
12

Tolerances No Not applicable; there are no established tolerances for 

oxadiazon. 

Incidents Will check for 

updates 

For a discussion of reported human incidents for 

oxadiazon, see page 15 of the Scoping Document and 

the Oxadiazon: Tier 1 Review of Human Incidents. 

Guidance for Commenters: Additional ecological information requested for this 

registration review, and of particular interest to EPA, is described below. 

 Ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and 

mammalian mortalities) not already reported to the Agency. 

 Water quality monitoring data (see Appendix for further details). 

 The name, toxicity, structure, and CAS number for each of the degradates listed in 

Section 5 of the EFED Problem Formulation 

TIMELINE 

EPA has created the following estimated timeline for the completion of the oxadiazon 

registration review in Table 5 below. 

Table 5: Projected Oxadiazon Registration Review Timeline

Activity Estimated Date

Opening the Docket 

Open Docket and 60-day Public Comment Period 2014 – December 

Close Public Comment Period 2015 – February 

Case Development 

Issue Final Work Plan 2015 – May 

Issue DCI 2015 July – Sept.

Data Submission 2018 July – Sept.

Open 60-day Public Comment Period for Draft Risk 

Assessments6

2020 Jan. - March 

Registration Review Decision 

Open 60-day Public Comment Period for Proposed 

Registration Review Decision 

 2020 Oct. – Dec.

Issue Registration Review Decision and Begin PostDecision Follow-up 2021 

Total (years) 7 

 

6

 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 generally for draft risk assessments. 
13

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 oxadiazon. 
14

Appendix – Additional Areas Considered in the Oxadiazon 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. Because oxadiazon is not registered for food/feed uses in the U.S., it 

has no U.S. tolerances; therefore, the Agency does not anticipate any trade irritant issues for it. 

Water Quality: 

Oxadiazon is not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act.7

 In addition, no Total Maximum Daily Loads 

(TMDL) have been developed for oxadiazon.8 More information on impaired water bodies and 

TMDLs can be found at the Agency’s website.9 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 Process10 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 oxadiazon 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.

 

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

8

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

group_name=PESTICIDES 9 http://www.epa.gov/owow/tmdl/

10 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
15

ENDANGERED SPECIES: 

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

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

allow the Agency to determine whether use of oxadiazon 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 most recent registration decision for oxadiazon, 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), oxadiazon 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. A second list of 

chemicals identified for EDSP screening was published on June 14, 201311 and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors. 

 

11 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 
16

For further information on the status of the EDSP, the policies and procedures, the lists of 

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

website.12

HUMAN STUDIES: 

Occupational and Residential 

Past oxadiazon 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. 

 

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