2 

Table of Contents 

I.     Introduction................................................................................................3 

II. Use and Usage.............................................................................................4 

III. Scientific Assessments....................................................................................5 

 A. Human Health Risk Assessment.......................................................................5 

 1. Risk Conclusions...................................................................................5 

 2. Tolerances..........................................................................................6 

 B. Environmental Assessment.............................................................................6 

 1. Environmental Fate and Exposure...............................................................6 

 2. Ecological Risk Characterization.................................................................6 

 3. Ecological Risk Uncertainties....................................................................7 

 4. Overview of Ecological Risk Conclusions.....................................................7 

 5. Effects on Aquatic Organisms...................................................................7 

 6. Effects on Terrestrial Organisms................................................................8 

 7. Ecological Risk Management Conclusions for Non-listed Species.........................9 

 C. Endangered Species Assessment .......................................................................9 

 D. Endocrine Disruptor Screening Program............................................................10 

IV. Proposed Interim Registration Review Decision....................................................11 

V. Next Steps and Timeline..................................................................................12

A. Interim Registration Review Decision..............................................................12 

B. Implementation of Mitigation Measures............................................................12 

Appendix A: Summary of Actions Taken for Hexythiazox...........................................13 

Appendix B: Hexythiazox Label Table..................................................................14 

 
3 

I. Introduction 

This document is the Environmental Protection Agency’s (EPA or the Agency) Proposed 

Interim Registration Review Decision for hexythiazox (PC code 128849) and is being issued 

pursuant to 40 CFR sections 155.56 and 155.58. A registration review decision is the Agency's 

determination on whether a pesticide meets, or does not meet, the standard for registration in the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The Agency may issue, when it 

determines it to be appropriate, a proposed interim registration review decision before 

completing a registration review final decision. Among other things, the proposed interim 

registration review decision may 1) require new risk mitigation measures; 2) impose interim risk 

mitigation measures; 3) identify data or information required to complete the review; and 4) 

include schedules for submitting the required data, conducting the new risk assessment and 

completing the registration review. For further information on hexythiazox, additional 

documents can be found in EPA’s public docket (EPA-HQ-OPP-2006-0114) at 

www.regulations.gov. 

 FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandated the 

continuous review of existing pesticides. All pesticides distributed or sold in the United States 

generally must be registered by the EPA based on scientific data showing that they will not cause 

unreasonable risks to human health or to the environment when used as directed on product 

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

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

meet the statutory standard of no unreasonable adverse effects. Changes in science, public 

policy, and pesticide use practices will occur over time. Through the registration review 

program, the Agency periodically re-evaluates pesticides to make sure that as these changes 

occur, products in the marketplace can continue to be used safely. Information on this program 

is provided as www.epa.gov/oppsrrd1/registration_review/. 

In 2006, the Agency implemented the registration review program pursuant to FIFRA 

section 3(g) and EPA will review each registered pesticide every 15 years to determine whether 

it continues to meet the FIFRA standard for registration. 

 This document comprises the proposed interim registration review decision for 

hexythiazox, an acaricide that acts primarily as a mite growth inhibitor/ovicide that is registered 

for use to control mites. Hexythiazox is registered for use on a variety of agricultural crops, turf, 

and various residential plants. It was first registered in 1989. Since hexythiazox was registered 

after 1984, it was not subject to the reregistration requirements of FIFRA. 

Pursuant to 40 CFR section 155.50, EPA formally initiated registration review for 

hexythiazox (case 7404). The following highlights significant events that have occurred during 

the registration review of hexythiazox: 

 February 2, 2007 – Publication of Hexythiazox Summary Document for a 90-day public 

comment period. The Summary Document included the preliminary work plan (PWP) 

and was accompanied by the scoping document and problem formulation. 
4 

 July 2, 2007 - Final Work Plan (FWP) for hexythiazox was signed -- Three public 

comments were received during the 90-day comment period for the Hexythiazox 

Summary Document, but the comments did not address the data requirements, work plan, 

or time line described in the Summary Document and, therefore, did not result in changes 

to the proposed work plan, which was made final in the Hexythiazox Final Work Plan. 

 September 22, 2008 – The Agency issued the Registration Review Data Call-In (GDCI128849-879) to the technical registrant for hexythiazox, Gowan Company. 

 June 26, 2013 – The Agency published the Preliminary Environmental Fate and 

Ecological Risk Assessment in Support of the Registration Review of Hexythiazox and the 

Hexythiazox. Registration Review Preliminary Human Health Risk Assessment for a 60-

day public comment period. One comment was received during the comment period. 

The National Alfalfa Forage Alliance (NAFA) commented on the importance of 

hexythiazox to alfalfa growers in the treatment of spider mite infestations and commented 

on its perceived lack of effects to beneficial insects. 

 July 2014 – The Agency is now publishing the Hexythiazox Proposed Interim 

Registration Review Decision, dated July 2014 in docket number EPA-HQ-OPP-2006-

0114 for a 60-day public comment period. 

II. Use and Usage 

As described in the April 28, 2014 Use and Usage, Pest Management Role, and Response 

to Comments for Hexythiazox, available in the hexythiazox docket, hexythiazox is a nonsystemic, foliar miticide registered for use on various fruit, nut, vegetable, and row crops, as well 

as on turf, and residential plants, with applications limited to once per year. Hexythiazox acts 

primarily as a mite ovicide, and it is used to control phytophagous mites, including problematic 

spider mite pests. Hexythiazox labels limit applications of either the end-use product or the 

hexythiazox active ingredient to once per year. It is often applied early in the growing season to 

target mite eggs in order to control the mite population throughout the rest of the growing 

season. 

Hexythiazox belongs to the Insecticide Resistance Action Committee’s (IRAC) Group 10 

and is classified as a mite growth inhibitor. There is some ambiguity in the Group 10 

designation, as this group’s actual defined modes of action are not well characterized. However, 

the chemicals in this group are presumed to be similar modes of action due to their shared 

ovicidal activity and observed instances of cross-resistance. While hexythiazox can be applied at 

various points in the season to kill mite eggs, it is often recommended for use as an early-season 

pest management tool, with the intention to get good control of eggs and thus prevent mite 

outbreaks from developing later in the season. Hexythiazox can be applied as a liquid foliar 

spray by air or ground application equipment. For most crops, applications are made at rates 

below the maximum application rate. 

While there are a number of miticide alternatives available that target adult mites (in 

several different IRAC groups), there are not many other ovicide alternatives to hexythiazox. 
5 

Clofentazine and etoxazole are the other Group 10 miticides registered for use in the United 

States. However, these alternatives are not registered for use on all crops covered by 

hexythiazox registrations. For dates, citrus, alfalfa (hay production) and sweet corn (grown for 

seed), hexythiazox is the only ovicidal chemical registered for mite control. 

Relative to other Group 10 miticide alternatives, the cost of application for hexythiazox is 

comparable to the alternative ovicide etoxazole but more expensive than clofentazine. On the 

whole, hexythiazox has a higher average cost per acre than some of the adulticidal alternatives 

such as abamectin, spirodiclofen, pyridaben, and fenbutatin oxide. However, some adulticides 

may be applied multiple times, depending upon both population pressure and the success of early 

season mite management efforts. 

 An updated Screening Level Usage Analysis (SLUA) for hexythiazox was conducted in 

April 2014. SLUA usage data (2004-2012) show a significant number of crops treated with 

hexythiazox. The crops with the greatest average annual usage are as follows: strawberries 

(25% crop treated); pluots (based on California Department of Pesticide Regulation data); 

caneberries, dates, nectarines and tangerines (15% crop treated); and almonds and peaches (10% 

crop treated). The updated report, Revised Usage Report in Support of a Registration Review 

Preliminary Risk Assessment Purposes for the Insecticide Hexythiazox, can be found in the 

hexythiazox registration review docket (EPA-HQ-OPP-2006-0114) at www.regulations.gov 

III. Scientific Assessments

A. Human Health Risk Assessment 

The Agency considered recently completed human health risk assessments and the most 

updated science policies and methodologies in the Hexythiazox. Registration Review Preliminary 

Human Health Risk Assessment published on June 26, 2013 in the public docket EPA-HQ-OPP2006-0114-0021, which can be accessed on http://www.regulations.gov/. The hexythiazox 

human health risk assessments, described below, that informed the Agency’s human health 

preliminary risk assessment are also available in the registration review docket. 

1. Risk Conclusions 

Dietary, residential, and aggregate risks for all registered uses of hexythiazox were 

assessed in the September 25, 2012 Hexythiazox. Human Health Risk Assessment to Support 

New Uses on Alfalfa and Timothy. There are no dietary, residential or aggregate risks of concern 

for hexythiazox. 

The occupational risks associated with the use of hexythiazox were assessed in the 

September 25, 2012 human health risk assessment; the June 22, 2011 Human Health Risk 

Assessment to Support Amended Use on Field Corn and New Use on Greenhouse Tomatoes; and 

the October 12, 2012 memorandum Hexythiazox: Summary of Hazard and Science Policy 

Council (HASPOC) Meetings, available in the hexythiazox docket (EPA-HQ-OPP-2006-0114). 

The recently conducted occupational risk assessments and the HASPOC memorandum address 

all registered uses of hexythiazox, and there are no occupational risks of concern. 
6 

2. Tolerances 

 The 2007 Hexythiazox Summary Document recommended the reduction of 7 tolerances 

established for hexythiazox under 40 CFR 180.448: pome fruit (crop group 11), apple, wet 

pomace, and the meat byproducts of cattle, sheep, goat, and horse. Since the 2007 Hexythiazox

Summary Document was completed, all of the recommended tolerance reductions have been 

finalized. See the Federal Register (54 FR 17948) for a listing of current hexythiazox tolerances. 

Maximum Residue Levels (MRLs) for hexythiazox have been established by Codex for 

apples, cherries, peaches, dry hops, pears, plums, fresh prunes, strawberries, citrus fruits, 

common bean (pods and immature seeds), cucumbers, currants (red and white), grapes and 

tomatoes. There are no Canadian MRLs established. One Mexican MRL is established for 

strawberries. The Codex and Mexican MRLs are not compatible with the U.S. tolerances 

because the U.S. tolerance expression currently includes parent hexythiazox and its metabolites 

containing the (4-chlorophenyl)-4-methyl-2-oxo-3-thiazolidine moiety, while the MRLs are 

established for hexythiazox alone. 

B. Environmental Assessment

The risk assessment supporting this Proposed Interim Registration Review Decision 

evaluates risks to species that are not subject to the Endangered Species Act (ESA) and provides 

a screening level assessment for potential risks to listed species under ESA. A summary of the 

Agency’s environmental risk assessment for hexythiazox is presented below. For detailed 

discussions of all aspects of the environmental risk assessment, see the Preliminary 

Environmental Fate and Ecological Risk Assessment in Support of the Registration Review of 

Hexythiazox, published on June 26, 2013 in the public docket EPA-HQ-OPP-2006-0114-0020, 

which can be accessed on http://www.regulations.gov/. 

1. Environmental Fate and Exposure 

 Parent hexythiazox is moderately persistent. It degrades to transformation products with 

a half-life of 27 to 43 days in aerobic soil and 30 to 40 days in aerobic aquatic systems. It is 

stable to hydrolysis though photolyzes in water with a half-life of 17 days. Given the low 

solubility of hexythiazox and its propensity to adsorb, it is likely that the compound will readily 

partition to soil and sediments. Although parent hexythiazox is considered slightly mobile, it 

may reach water through run-off of sediment-bound residues (i.e., erosion). Hexythiazox is not 

likely to volatilize and is not expected to bioaccumulate in aquatic organisms. 

2. Ecological Risk Characterization 

 To estimate potential ecological risk, EPA integrates the results of exposure and 

ecotoxicity studies using the risk quotient method. Risk quotients (RQs) are calculated by 

dividing peak or multi-day average estimated environmental concentrations (EECs) by acute or 

chronic ecotoxicity values for various wildlife and plant species. RQs are then compared to 

levels of concern (LOCs) and when the RQ exceeds the LOC for a particular category, the 
7 

Agency evaluates the potential for a risk of concern to that category. Risk characterization 

provides further information on potential adverse effects and the possible impact of those effects 

by considering the fate of the chemical and its degradates in the environment, organisms 

potentially at risk, and the nature of the effects observed. 

 3. Ecological Risk Assessment Uncertainties 

 While there are toxicity data gaps for some species, the database for hexythiazox is 

considered substantially complete and sufficient for risk assessment and regulatory decision 

making. The major area of uncertainty is the potential increased sensitivity of early lifestages of 

non-target terrestrial invertebrates to hexythiazox. The existing data indicate that hexythiazox is 

practically non-toxic to adult non-target terrestrial insects, including honey bees, on an acute 

basis. However, hazard to terrestrial arthropods is presumed to be greatest to egg, larval, and 

juvenile lifestages as hexythiazox is a mite growth inhibitor/ovicide. Gowan Company has 

committed to conduct a study designed to address this uncertainty. EPA will review these data 

once they are submitted and incorporate findings into an endangered species assessment for 

hexythiazox. 

4. Overview of Ecological Risk Conclusions 

There are no risks of concern expected for mammals, birds (including reptilian 

surrogates), pelagic (water column-dwelling) invertebrates, and aquatic plants. 

Potential acute risk from the use of hexythiazox is not expected to fish (surrogates for 

aquatic-phase amphibians) at its limit of solubility or to non-target terrestrial invertebrates. 

Potential chronic risk to fish and non-target terrestrial invertebrates is uncertain due to lack of 

data. 

Acute risk is not expected for terrestrial and semi-aquatic plants and benthic (sedimentdwelling) aquatic invertebrates. While there is uncertainty in the potential chronic risk to these 

taxa due to the lack of data, potential risk is not expected from the registered uses of hexythiazox 

based on the lines of evidence discussed below. 

5. Effects on Aquatic Organisms 

Aquatic Invertebrates 

Available toxicity data indicate that hexythiazox is not acutely toxic at its solubility limit 

to aquatic invertebrates, thus acute risks of concern are not expected. In addition, chronic risk to 

pelagic invertebrates, based on calculated RQs, does not exceed the Agency’s level of concern. 

Chronic risk to benthic aquatic invertebrates is uncertain due to a lack of sediment toxicity data. 

However, the No Observed Adverse Effects Concentration (NOAEC) for benthic invertebrates 

would have to be nearly two times more sensitive than the freshwater pelagic invertebrate growth 

NOAEC and eight times more sensitive than the reproduction NOAEC to trigger an LOC 

exceedance. In addition, a 21-day toxicity test with midges (Chironomus riparius) found no 

effect to either emergence or development at concentrations tested up to hexythiazox’s solubility 

limit (0.120 mg/L). By these lines of evidence, the potential for chronic effects to benthic 
8 

aquatic invertebrates is considered to be low. 

Fish 

As with aquatic invertebrates, hexythiazox is not acutely toxic at its solubility limit to 

fish, thus acute risks of concern are not expected. Potential chronic risk is uncertain due to lack 

of data. 

Aquatic Plants 

The RQs for aquatic vascular and non-vascular plants are below the Agency’s LOC and, 

therefore, are not of concern to the Agency. 

6. Effects on Terrestrial Organisms 

Mammals and Birds 

There are no acute or chronic risks of concern to birds (and to reptiles and terrestrialphase amphibians for which birds serve as surrogates) or mammals from the registered uses of 

hexythiazox based on calculated RQs. 

Terrestrial Plants 

 Risk to terrestrial and semi-aquatic plants is uncertain due to lack of Tier II seedling 

emergence data for two crop species and incomplete Tier I vegetative vigor testing (6 of 10 

species tested). While the dataset is incomplete, eight of 10 tested crop species in the Tier I 

seedling emergence test did not exhibit a phytotoxic response in excess of the 25% Tier II trigger 

risk and the available vegetative vigor testings gave no indication that hexythiazox causes 

excessive phytotoxic response when applied at the maximum labeled rate. Based on these lines 

of evidence, potential risk to terrestrial and semi-aquatic plants is not expected. 

 Terrestrial Invertebrates 

On an acute exposure basis, hexythiazox is classified as practically non-toxic to nontarget terrestrial insects, including honey bees. However, available data may not represent the 

sensitivity of other insect lifestages (e.g., eggs, larvae, juveniles). Given that hexythiazox’s 

mode of action affects the eggs and juvenile lifestages of mites and that chronic reproductive 

effects were observed in both the freshwater and saltwater aquatic invertebrate lifecycle tests, it 

is possible that non-target terrestrial invertebrates (e.g., bees) could be affected by applications of 

hexythiazox. Therefore, risk to non-target terrestrial invertebrates is considered uncertain. 

Subsequent to the completion of EPA’s 2013 Preliminary Environmental Fate and 

Ecological Risk Assessment in Support of the Registration Review of Hexythiazox, Gowan 

Company submitted a honey bee semi-field study conducted in the United Kingdom to address 

uncertainty regarding potential risk to early lifestages of non-target terrestrial invertebrates such 

as bees. However, this study is of limited utility because it was conducted at a rate of 0.09 

pounds active ingredient/acre (lbs ai/A). The U.S. maximum application rate is 0.1875 lb ai/A 
9 

and the typical application rates for hexythiazox, which vary by crop, are generally above 0.09 lb 

ai/A. 

7. Ecological Risk Management Conclusions for Non-Listed Species 

The database for hexythiazox is considered substantially complete and sufficient for 

regulatory decision making. While chronic risk to fish and non-target terrestrial invertebrates is 

uncertain due to data gaps, the risk potential is expected to be low as hexythiazox is applied once 

per year at a low application rate and is not highly persistent in the environment. Thus, any 

effects to non-target organisms are expected to be transient and not result in significant chronic 

effects. Gowan Company has committed to conduct a study to address potential effects to early 

lifestages of non-target terrestrial invertebrates. EPA will review these data upon submission 

and consider them in the upcoming endangered species assessment. 

The Agency is currently working with Gowan Company to ensure that all product labels 

clearly state that only one application of hexythiazox active ingredient is allowed per year. Some 

labels restrict the number of applications of product (not active ingredient), which may lead to 

use of more than one hexythiazox product per site per year. In addition, any label language 

indicating that hexythiazox products are safe to beneficial insects must, in the absence of data to 

support this claim, be removed from hexythiazox labels. 

As previously described, there are not many ovicide alternatives to hexythiazox, and it is the 

only ovicidal chemical registered for mite control for dates, citrus, alfalfa (hay production) and 

sweet corn (grown for seed). Early season control of mite eggs can preclude the need for 

subsequent miticide applications in many crops. 

C. Endangered Species Assessment 

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the 

National Marine Fisheries Service (NMFS) (collectively, the Services), and the U.S. Department 

of Agriculture (USDA) released a summary of the joint Interim Approaches in the white paper

“Interim Approaches for National-Level Pesticide Endangered Species Act Assessments Based 

on the Recommendations of the National Academy of Sciences April 2013 Report,” dated 

November 1, 2013. 

The Interim Approaches were developed jointly by the agencies in response to the 

National Academy of Sciences’ (NAS) recommendations and reflect a common approach to risk 

assessment shared by the agencies as a way of addressing scientific differences between the EPA 

and the Services. The NAS report outlines recommendations on specific scientific and technical 

issues related to the development of pesticide risk assessments that EPA and the Services must 

conduct in connection with their obligations under the Endangered Species Act (ESA) and 

FIFRA. 

The joint Interim Approaches were released prior to a stakeholder workshop held on 

November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the 

December 2013 Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues 

Research and Evaluation Group (SFIREG) meetings, and held a stakeholder workshop in April 
10 

2014, allowing additional opportunities for stakeholders to comment on the Interim Approaches. 

As part of a phased, iterative process for developing the Interim Approaches, the agencies will 

also consider public comments on the Interim Approaches in connection with the development of 

upcoming Registration Review decisions 

Given that the agencies are continuing to develop and work toward implementation of the 

Interim Approaches to assess the potential risks of pesticides to endangered and threatened 

(listed) species and their designated critical habitat, the ecological risk assessment supporting 

this Proposed Interim Registration Review Decision for hexythiazox does not contain a complete 

ESA analysis that includes effects determinations for specific listed species or designated critical 

habitat. Although EPA has not yet completed effects determinations for specific species or 

habitats, for this preliminary assessment EPA conducted a screening-level assessment for all taxa 

of non-target wildlife and plants that assumes for the sake of the assessment that listed species 

and designated critical habitats may be present in the vicinity of the application of hexythiazox. 

This screening level assessment will allow EPA to focus its future evaluations on the types of 

species where the potential for effects exists once the scientific methods being developed by the 

agencies have been fully vetted. While the agencies continue to develop a common method for 

ESA analysis, the regulatory section of the Proposed Interim Registration Review Decision 

document will describe the level of ESA analysis completed for this particular registration 

review case. Once the agencies have fully developed and implemented the scientific methods 

necessary to complete risk assessments for listed species and their designated critical habitats, 

these methods will be applied to subsequent analyses for hexythiazox as part of completing this 

registration review. 

D. Endocrine Disruption 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 hexythiazox, 

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), 

hexythiazox 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 
11 

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, including hexythiazox, identified for EDSP screening was published on June 14, 

20131

 and includes some pesticides scheduled for Registration Review and chemicals found in 

water. 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.2 In this interim decision, EPA is making no human health or environmental safety 

findings associated with the EDSP screening of hexythiazox. Before completing this 

Registration Review, the Agency will make an EDSP FFDCA section 408(p) determination. 

IV. Proposed Interim Registration Review Decision 

In accordance with 40 CFR Sections 155.56 and 155.58, the Agency is issuing this 

Proposed Interim Registration Review Decision Document for hexythiazox. Except for the 

EDSP and ESA components of the hexythiazox registration review case, the Agency has made 

the following interim decision: (1) additional data are required to assess the potential 

reproductive effects to beneficial pollinators; and (2) changes are required to hexythiazox 

product labels. Gowan Company has agreed to amend any product labels that do not clearly 

state that no more than one application of hexythiazox active ingredient is allowed per year. In 

addition, Gowan must remove statements claiming that hexythiazox is safe to beneficial insects 

in the absence of data to support these claims. 

In the interim, EPA is making no human health or environmental safety findings 

associated with the EDSP screening of hexythiazox. Before completing this Registration 

Review, the Agency will make an EDSP FFDCA section 408(p) determination. Likewise, before 

completing this Registration Review, the Agency will conduct an ecological risk assessment to 

address the Agency’s obligations under both the ESA and FIFRA. While the risk assessment 

supporting this Proposed Interim Registration Review Decision evaluates risks to species that are 

not subject to the ESA, EPA is still in the process of conducting a risk assessment for listed 

species and their designated critical habitats for hexythiazox. In this Proposed Interim Decision, 

therefore, EPA has not completed effects determinations for listed species associated with the 

registered uses of hexythiazox. The Agency is issuing a Proposed Interim Registration Review 

Decision pending completion of the ESA and EDSP assessments. 

 

1

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

chemicals. 

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

V. Next Steps and Timeline 

A. Interim Registration Review Decision

A Federal Register Notice will announce the availability of this proposed interim 

registration review decision for hexythiazox and allow a 60-day comment period. If there are no 

significant comments or additional information submitted to the docket during the comment 

period that leads the Agency to change its decision, EPA may issue a final interim registration 

review decision for hexythiazox. A final decision on the hexythiazox registration review case 

will occur after an ESA and EDSP FFDCA section 408(p) determination have been made. 

B. Implementation of Mitigation Measures 

Once the Final Interim Registration Review Decision is issued, registrants must submit 

proposed amended labels that include the agreed-upon risk mitigation, described in Appendices 

A and B below, to the Agency for approval within 60 days of such issuance.
Docket Number EPA-HQ-OPP-2006-0114 

www.regulations.gov 

Appendix A: Summary of Actions Taken for Hexythiazox 

Registration Review Case#:7404 PC Code: 128849 Chemical Type: Acaracide Chemical Family: Thiazolidine Mode of Action: Unknown; acts as a mite growth inhibitor/ovicide 

Potentially-Affected 

Population(s) 

Source of 

Exposure 

Route of Exposure Duration of 

Exposure 

Risk(s) of Concern Action(s) 

Non-target terrestrial 

insects (early lifestages, i.e., egg, larval, and 

juvenile) 

Residues on treated pollen potentially transported 

back to 

hive via adult worker bees 

Dermal and/or oral Chronic Reproductive effects to 

non-target terrestrial insects 

- limit applichexythiazox ingredient to year per treatsite - remove langstatements clproducts are beneficial ins
14 

Appendix B: Hexythiazox Label Table - Summary of Labeling Changes for Hexythiazox U

Description Amended Labeling Language for Hexythiazox Products 

End Use Products

Language limiting number of applications “Do not make more than one application of hexythiazox per year.” Language relating to beneficial insects Remove statements claiming that hexythiazox products are safe to beneficial insects.