2

Strychnine Preliminary Work Plan – Table of Contents 

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

ANTICIPATED DATA NEEDS .................................................................................................... 3

STATUTORY AND REGULATORY AUTHORITY ................................................................... 4

CHEMICAL FACTS ...................................................................................................................... 4

USE AND USAGE INFORMATION ............................................................................................ 5

RECENT ACTIONS ....................................................................................................................... 6

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW ................................ 6

TIMELINE ...................................................................................................................................... 9

NEXT STEPS ................................................................................................................................. 9

Appendix – Additional Areas Considered in the Strychnine Registration Review ...................... 10

References: 

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

based on the following documents: 

1. Problem Formulation in Support of the Registration Review for Strychnine (PC Code 

076901). Nicholas Mastrota, James Wolf, and Rosanna Louie-Juzwiak. November 13, 

2015. 

2. Strychnine. Human Health Assessment Scoping Document in Support of Registration 

Review. Jaime D’Agostino and Matthew Crowley. December 15, 2015. 

3. Strychnine: Tier I (Scoping) Review of Human Incidents and Epidemiology. Shana Recore. 

November 17, 2015. 

4. BEAD Chemical Profile for Registration Review: Strychnine Alkaloid (076901). Colwell 

Cook. July 24, 2015.

5. EFED Table 1 Report. Ingredient: Strychnine (076901). June 1, 2015.

6. HED Master Label Report. Ingredient: Strychnine (076901). June 1, 2015.

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

in the docket EPA-HQ-OPP-2015-0754 at http://www.regulations.gov. 
3

OVERVIEW 

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

registration review (docket number EPA-HQ-OPP-2015-0754). Strychnine is an alkaloid 

compound registered for use as an active ingredient in rodenticide baits for vertebrate pest 

control. There are no registered food uses for strychnine. Strychnine products are used primarily 

in underground burrows on residential lawns, pastures, rangeland, and cropland. This 

Preliminary Work Plan (PWP) document explains what EPA’s Office of Pesticide Programs 

knows about strychnine, 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 strychnine. 

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 strychnine and what types of new data or 

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

strychnine. 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 strychnine. 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 strychnine. 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. 

ANTICIPATED DATA NEEDS 

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

anticipated data needs, see the Problem Formulation in Support of the Registration Review for 

Strychnine (PC Code 076901) and Strychnine. Human Health Assessment Scoping Document in 

Support of Registration Review. 

 
4

Table 1: Anticipated Data Needs for the Strychnine Registration Review 

Guideline 

Number Study Title Test Material 

Estimated Timeframe 

(Months from receipt of 

DCI) 

Non-Guideline Subacute Inhalation Toxicity Study TGAI 24 

TGAI = technical grade active ingredient 

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.1

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 strychnine. 

CHEMICAL FACTS 

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

 

 

1

 http://www2.epa.gov/pesticide-reevaluation 
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Table 2: Chemical Facts for Strychnine

PC code 076901 

Case Number 3133 

CAS Number 57-24-9 

Year first registered 1947 

Pesticide Type Rodenticide 

Chemical class Alkaloid 

Reregistration Eligibility 

Decision (RED) 

1996 

Tolerance Reassessment 

Eligibility Decision (TRED) 

Not applicable – there are no established tolerances for strychnine. 

Cumulative group Not applicable. Strychnine has not been identified as a member of a 

cumulative group that shares a common mechanism of toxicity. 

40 CFR Citation There are no established tolerances for strychnine. 

Dual-use Strychnine 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 strychnine. 

Pesticide Re-evaluation 

Division, Chemical Review 

Manager 

Susan Bartow, bartow.susan@epa.gov, 703-603-0065 

Registration Division, 

Product Manager 

Mark Suarez, Suarez.mark@epa.gov, 703-305-0120 

USE AND USAGE INFORMATION 

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

Chemical Profile for Registration Review: Strychnine Alkaloid (076901) in the registration 

review docket for more details. 

Table 3: Strychnine Use and Usage Information

Summary of Use Strychnine is a rodenticide currently registered only for underground 

use to control pocket gophers, except in the state of Nevada where a 

special local need registration also allows its use to control the yellowbellied marmot and 3 species of ground squirrel. 

Use Sites Orchards, pastures, rangelands, agricultural crops, non-agricultural 

uncultivated areas, irrigation systems, and residential outdoor premises. 

Summary of Usage EPA has no available usage data for strychnine. 

Formulation Type(s) Granular, pelleted/tableted, and ready-to-use solution/paste. 

Application Method(s) Products can be applied manually by spoon or bait dispensing probe or 

mechanically by “burrow builder” (which digs artificial tunnels) or an 

impinger (which “injects” bait into the animals tunnel). 

Technical Registrant(s) Fort Dodge Chemical Company and H Interdonati Inc. 

No. of Registrations 18 Section 3 products2and 1 section 24(c) product. 

Restricted Use All strychnine products, except for those products which contain 

strychnine at nominal concentrations no greater than 0.5% and which 

 

2

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

(http://oaspub.epa.gov/pestlabl/ppls.home). 
6

Table 3: Strychnine Use and Usage Information

are limited by their labels to manual below-ground applications, were 

classified as restricted use by the Agency in 1978. Currently there are 

10 section 3 products and 1 section 24(c) product classified as restricted 

use pesticides. 

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. 

 Information on why strychnine is selected rather than other rodenticides. 

 Descriptions of where, when, and how strychnine is used. 

 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 strychnine to the US 

market. 

RECENT ACTIONS 

There are no recent actions for strychnine. 

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW 

The most recent comprehensive human health risk assessment for strychnine was completed on 

January 22, 1996 in preparation for the Reregistration Eligibility. The most recent ecological risk 

assessment was completed 2009 to assess risk to three species inhabiting California that are 

federally listed as threatened or endangered species—California red-legged frog, California tiger 

salamander, and the San Joaquin kit fox. Findings and conclusions from these risk assessments 

are summarized in the Problem Formulation in Support of the Registration Review for 

Strychnine (PC Code 076901) and Strychnine. Human Health Assessment 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 

strychnine. For human health, EPA anticipates the need to conduct a revised occupational risk 

assessment during registration review. In the previous RED, no endpoints were set due to the 

lack of toxicity studies available from which to identify endpoints. Since the Agency plans to 
7

perform a quantitative occupational inhalation exposure assessment, an inhalation endpoint will 

be chosen during Registration Review. Any changes to the standard operating procedures or 

default exposure assumptions also will be considered in the new assessment. 

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

EFED Problem Formulation and HED Scoping Document. 
8

Table 4: Anticipated Risk Assessments for the Strychnine 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 The risk assessment will focus on risk from primary 

exposure to non-target wildlife that consume strychnine 

bait, and secondary exposure to predators and scavengers 

that feed on small mammals (target and non-target) which 

feed on strychnine bait. 

Incidents Will check for 

updates 

For a discussion of reported ecological incidents for 

strychnine, see page 10 of the Problem Formulation. 

Human Health 

Dietary 

Food No Strychnine is a non-food use rodenticide and its limited 

and targeted underground uses do not warrant estimation 

of concentrations in drinking water; therefore, a dietary 

exposure assessment is not applicable. 

Drinking water No 

Occupational 

Handlers (mixers, loaders, 

applicators) 

Yes Registration Review will include an inhalation 

occupational handler exposure assessment only. Based on 

the estimated low dermal absorption, a dermal exposure 

assessment will not be conducted. Exposures are 

anticipated to be short-term only; intermediate-term and 

chronic exposures are not expected. 

Post-application No No post-application exposure assessment will be 

conducted. Due to strychnine’s formulation as a solid or 

paste and its targeted underground use, no inhalation 

exposure or dermal contact with residues are expected 

following applications. 

Residential 

Handlers No Residential handler assessments will not be conducted 

based on existing label requirements for clothing and 

PPE. 

Post-application No A residential post-application exposure assessment will 

not be conducted because contact with or ingestion of 

residues is not expected due to the underground use.

Exposure via drift or volatilization is not expected due to 

strychnine’s formulation as solids/pastes and its 

underground use. 

Other 

Aggregate No Because strychnine is a non-food use rodenticide with 

limited and targeted underground uses, dietary and 

residential exposures are not expected. 

Cumulative No Unlike other pesticides for which EPA has followed a 

cumulative risk approach based on a common mechanism 

of toxicity, EPA has not made a common mechanism of 

toxicity finding as to strychnine and any other substances 

and strychnine does not appear to produce a toxic 

metabolite produced by other substances. 

Tolerances No There are no established tolerances for strychnine. 
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Incidents Will check for 

updates 

For a discussion of reported human incidents for 

strychnine, see page 8 of the Scoping Document and 

Strychnine: Tier I (Scoping) Review of Human Incidents 

and Epidemiology. 

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). 

TIMELINE 

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

registration review in Table 5 below. 

Table 5: Projected Strychnine Registration Review Timeline

Activities Estimated Date

Opening the Docket 

Open Docket and 60-day Public Comment Period 2015 December 

Close Public Comment 2016 February 

Case Development 

Final Work Plan 2016 May 

Issue DCI 2016 July - September 

Data Submission 2018 July - September 

60-day Public Comment Period for Draft Risk Assessments3 2020 January - March

Registration Review Decision 

60-day Public Comment Period for Proposed Registration 

Review Decision 

2020 October - December 

Registration Review Decision and Begin Post-Decision 

Follow-up 

2021 

Total (years) 6 

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 strychnine. 

 

 

3

 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. 
10

Appendix – Additional Areas Considered in the Strychnine 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 strychnine 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: 

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

under section 303(d) of the Clean Water Act.4

 In addition, no Total Maximum Daily Loads 

(TMDL) have been developed for strychnine.5 More information on impaired water bodies and 

TMDLs can be found at the Agency’s website.6 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 Process7 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 strychnine compared to the general population. Please 

 

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

5

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

group_name=PESTICIDES 6 http://www.epa.gov/owow/tmdl/

7 http://www2.epa.gov/pesticide-reevaluation/opp-guidance-submission-state-and-tribal-water-quality-monitoringdata
11

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

exposure compared to the general population.

ENDANGERED SPECIES: 

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

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

allow the Agency to determine whether use of strychnine 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. 

A previous endangered species assessment was conducted for strychnine in 2009 to assess risk to 

three species inhabiting California that are federally listed as threatened or endangered species: 

the California red-legged frog (Rana aurora draytonii), California tiger salamander (Ambystoma 

californiense), and the San Joaquin kit fox (Vulpes macrotis mutica). The assessment made a 

“Likely to Adversely Affect” conclusion for all three species because of potential direct and 

indirect adverse effects from strychnine exposure due to labeled uses to control pocket gophers. 

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 strychnine, 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), strychnine 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. 
12

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, 20138

 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. 

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.9

 

8

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

chemicals. 9 http://www2.epa.gov/endocrine-disruption