### 1 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460



### PC Codes: 076901 DP Barcode : D428698 Date: November 13, 2015 MEMORANDUM

SUBJECT: Problem Formulation in Support of the Registration Review for Strychnine (PC Code 076901)

FROM: Nicholas Mastrota, Ph.D., Wildlife Biologist

James Wolf, Ph.D., Environmental Scientist

Rosanna Louie-Juzwiak, Risk Assessment Process Leader Environmental Risk Branch 3 Environmental Fate and Effects Division (7507P)

REVIEWED James Hetrick, Ph.D., Senior Advisor BY: Environmental Risk Branch 3 Environmental Fate and Effects Division (7507P)

THROUGH: Dana Spatz, Branch Chief Environmental Risk Branch 3 Environmental Fate and Effects Division (7507P)

TO: Kevin Costello, Branch Chief Cathryn Britton, Team Leader Sue Bartow, Chemical Review Manager Risk Management and Implementation Branch 2 Pesticide Re-Evalua tion Division (7508P)



## 1. Executive summary

The Environmental Fate and Effects Division (EFE D) has completed the problem formulation in support of the registration review of rodenticide uses of stry chnine (PC Code 076901). Use of strychnine has not changed, and no new environm ental fate or ecotoxicity testing has been submitted, since this rodenticide was previously assessed for reregistration in 1996. However, significant new information on the ecological risk of strychnine have become available in papers that have been published since 1996. In addition, more recent incident data are available that provide information on exposure a nd potential risk to non-target wildlife from current uses of strychnine. Of note are recent incidents of mortality involving the endangered San Joaquin kit

### 2 fox ( Vulpes macrotis mutica ). These incidents also raise concern about possible secondary poisoning of other mammalian predators and scavengers.



## 2. Nature of Chemical Stressor

Strychnine is an alkaloid compound that has been used for vertebrate pest control for centuries. Today the use of the poison in the United States is restricted to c ontrol of the pocket gopher (Order Rodentia, Family Geomyid ae), except in the state of Nevada where a special local need registration also allows its use to control the yellow-bellied marmot ( Marmota flaviventris ) and three species of ground squirrel.

Strychnine is a powerful convulsant . Strychnine acts as a selec tive competitive antagonist to block the inhibitory effects of glycine at a ll glycine receptors. The convulsant action of strychnine results from interference with posts ynaptic inhibition normally mediated by glycine, causing excessive excitation of mu scles that manifests itself as convulsions. Tetanic convulsions caused by a lethal dose of strychnine can l ead to rapid asphyxiati on and death. Death in mammals occurs within an hour after e xposure (Nolte and Wagner, 2001; MRID 43330301).

Chemical names, structures, and other id entifiers of strychnine are given in Table 1



### .

Table 1. Chemical Nomenclature and Structure of Strychnine.



### Common Name Strychnine Synonyms Strychnidin-10-one Strychnine alkaloid CAS Reg. No. 57-24-9 Empirical Formula C21H22N2O2 SMILE O=C1N2c3c(C45C6N(CC4) CC4=CCOC(C(C4C6)C25)C1)cccc3 Molecular Structure



## 3. Use Characterization

Strychnine is registered for use as an active ingr edient in rodenticide bait s. Currently, all but one of the registered products cont aining strychnine are solid bait s for controlling pocket gophers (Order Rodentia, Family Geomyidae). Numerous br ands of strychnine gopher bait products are available, but they are similar in that they are solid bait products containi ng 0.5% strychnine that

### 3 are designed to be placed within pocket gophe r burrows. Above ground application of these products is prohibited. The bait products must be placed either inside underground runways of existing gopher burrows, or into artificial burro ws that the gophers are expected to enter. Applications to existing burrow ar e made by digging an access hole, which is then sealed with soil after the bait is placed, or by using a probe to deposit the bait into the burrow. When used in artificial burrows, a piece of tractor-drawn ground equipment called a “burrow builder” is used. The burrow builder creates underground tunnels that intersect the gophe r’s existing burrows, while dropping measured amount of bait into the tunnels. The ba its may be used to control pocket gophers in various settings , including residentia l lawns, agricultura l cropland, pastures, forestry land, and rangeland. Many of the labels al so include “non-agricultural area” as a use site, and therefore may be used anywhere. Bait products may be used to control any of the numerous species of pocket gophers that occur in the United States ( Thomomys sp. and Geomys sp.). Species of pocket gopher are distri buted throughout centr al and western stat es, excluding Alaska and Hawaii, and in three s outheastern states, Florida, Georgia, and Alabama.

Up to 3 pounds of strychnine bait product, or 0.015 pound of strychnine active ingredient, may be applied per acre. The maximum rate for produ cts designed for resident ial use (EPA Reg No. 36029-1 and 909-2) range from 0.005 to 0.006 lb a.i. /A. The maximum rate for other strychnine bait products range from 0.005 to 0.015 lb a.i./A.

In addition to pocket gophers, strychnine may al so be used under a special local need (24C) registration for control of yellow-bellied marmots ( Marmota flaviventris ), Richardson ground squirrel ( Spermophilus richardsonil ), Beldin’s ground squirrel (S . beldingi ), and Piute ground squirrel ( S. mollis ) in the state of Nevada. This is a restricted use product containing 3.2% strychnine alkaloid paste registered by the Ne vada Department of Agriculture (EPA Reg. No. NV830009). This product may also be used to contro l four species of pocke t gopher that live in Nevada ( Thomomys sp.). The maximum use rate is 0.032 lb a.i./A.

EFED’s 2009 risk assessment for certain threat ened and endangered species in California (USEPA, 2009) included a summary of strychnine use in Califor nia reported by the California Department of Pesticide Registration (CDPR) in their Pesticide Use Re porting (PUR) data from 1999 to 2006. These data indicate that, in Californ ia, approximately 60% of the total pounds of strychnine applied was applied in nonagricultural sites. The nonagricultural sites included areas around domestic dwellings and other structures , landscape and recreational areas, and other “non-agriculture uncultivated areas/soils” such as ditch banks and right-of-ways. Agricultural sites in California with the greatest use of strychnine were grape vineyards, fruit and nut orchards, and alfalfa. Published papers indicate that strychnine bait is also commonly used to control pocket gophers in forestry sites in the Pa cific Northwest, in part icular in areas being reforested with conifer tree s eedlings (Nolte and Wagner, 2001, El Hani et al., 2002, Arjo and Bryson, 2007).



## 4. Conclusions from Previous Risk Assessments

EFED’s most recent ecological ri sk assessment for strychnine was completed in 2009 to assess risk to three species inhabiting California that are federally listed as th reatened or endangered

### 4 species: the Californi a 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 a dverse effects from strychnine e xposure due to labeled uses to control pocket gophers. The assessment concluded that the San Joaquin kit fox could be directly affected by oral exposure from consuming poisone d pocket gophers that it dug out of its burrow or found above ground, or by consuming soil inverteb rates that have been contaminated by the strychnine bait. It predicted that a gopher coul d carry enough strychnine bait in its cheek pouches to be lethal to a kit fox if it were consume d. The assessment concluded that the California redlegged frog and the California tiger salamander al so could be directly adversely affected, primarily from dermal exposure to strychnine if they were to use a strychnine-treated gopher burrow for shelter. It also concluded possible risk of secondary poisoning from these species consuming soil invertebrates that had been cont aminated by the strychnine bait. Finally, the assessment concluded that indirect adverse effect s were possible to all th ree species because use of strychnine bait could cause re duce prey abundance, and could i ndirectly adversely affect the red-legged frog and tiger salamander because of removal of gopher burrows which these species may use for shelter.

Prior to this endangered species assessment, EF ED conducted an ecological risk assessment for the Reregistration Eligibility Decision (RED) 1 

### for strychnine in March, 1996 (D216629, USEPA, 1996). This assessment concluded that risk to plan ts and aquatic animals would be negligible, but non-target terrestrial animals could be at risk if they were able to access the strychnine bait. In addition, the assessment found that residues in th e gastrointestinal trac t of poisoned pocket gophers would pose a risk to predator and scavenge r wildlife if they were to eat the carcasses. They also noted that studies have found that ap plication of strychnine bait using mechanical burrow-builder equipment may pose a hazard to non- target wildlife because of the spillage of bait that occurs when the burrow-builder is lifted from the soil at the end of the rows. However, prior to the RED, additional instructions we re added for burrow-builders stating that the applicator must pick up spilled bait to mitigat e the risk from the burrow builder application.

The RED concluded that prohibi tion of above-ground application of bait effectively reduces exposure to non-target wildlife, and that the us e of strychnine to c ontrol the pocket gophers, according to the label directions, does not pose an unreasonable risk to non-target species, although it may cause harm to certain threatened or endangered terrestrial wildlife species. To mitigate risk to endangered species, the following warning statement was recommended for all labels of strychnine bait products:

“ENDANGERED SPECIES CONSIDERATIONS:

1 USEPA. 1996. Reregistration Eligibility Decision (RED ) Strychnine. United States Environmental Protection

Agency, Washington, DC. EPA 738-R96-33. Available at: www.epa.gov/oppsrrd1/reregistration/REDs/3133.pdf

### 5 The killing of a member of an endangered sp ecies during strychnine baiting operations may result in a fine under the Endangered Species Act. Before baiting, the user is advised to contact the Regional U.S. Fish and Wildlife Service (End angered Species Specialist) of the local Fish and Game Office for specific information on endangered species.”



## 5. Environmental Fate and Transport

Hydrolysis and soil photolysis are not signifi cant transformation path ways for strychnine. Aerobic soil metabolism studies demonstrate a half-life of approximately 1 month. Batch adsorption/desorption data demonstrate strychni ne’s strong binding to various soils. With the current use pattern of applying st rychnine into below-ground burrows, strychnine is not expected to reach ground or surface water.

Strychnine does not hydrolyze at pH 5, 7, or 9 (MRID 41122301). Strychnine is stable to soil photolysis (MRID 42973401), but degr ades in soil under aerobic condi tions with a half-life of 26.7 days (MRIDs 42234201 and 43407601). The data indica te that strychnine is immobile; the parent is adsorbed to organic matter and cl ay. In the mobility study, unaged strychnine had Freundlich K ads 

### in loamy sand, sandy loam, loam, a nd sandy clay loam soils of 39.79, 94.65, 118.87, and 168.97 mL/g, respectively; adsorption in creased with increasing cation exchange capacity (CEC). Desorption (K des 

### ) values were 55.0, 89.4, 114.6, and 146.1 mL/g for the loamy sand, the sandy loam, the loam, and the sa ndy clay loam soils, respectively (MRID 42366501).

Table 2 lists the environmental fate properties of strychnine.

Table 2. Summary of Strychnine Environmental Fate Properties

Study Value MRID # Study Status Solubility (20°C) 11.5 mg/L Dissociation Constant (pK a ) 8.26 Vapor Pressure (20°C) 2.9 x 10 -9 mm Hg
Henry’s Law Constant 6.0 x 10 -14 atm

m 3 /mol Octanol/Water Partitioning Constant (pK ow ) 4.0 at pH 7 114.0 at pH 9 Hydrolysis Stable 41122301 Acceptable Soil Photolysis Stable 42973401 Acceptable

Aerobic Soil Metabolism 26.7 days 42234201 and 43407601 Supplemental

K d-ads / K d-des 39-168 mL/g 42366501 Acceptable

### 6 

## 6. Ecotoxicity

a. Toxicity to Terrestrial Animals

Available data on the toxicity of strychnine to birds and mammals are presented in Table 3. Data from studies that were submitted to the EPA by pesticide registrants are supplemented by acute wildlife toxicity data from testing conducted by the Environmental Contaminant Evaluation Program of the U.S. Fish and Wildlife (summa rized in Hudson et al., 1984) and by the Denver Wildlife Research Center of the U.S. Department of Agriculture. Acute oral toxicity studies conducted by the U.S. Fish and Wildlife were co nsidered acceptable for use in risk assessment when they were conducted using at least 20 test birds. To be consistent with the 850.2100 test guideline, only acute oral studies conducted with adult birds are classified as acceptable. For each study type, the lowest toxici ty value derived from an acceptable study was selected to be used in the quantitative risk assessment. Th ese values are shown in bold font in Table 3.

Toxicity data classifies strychnine as very highly toxic to birds and mammals with acute oral exposure, and highly toxic to birds with subacute dietary e xposure. These data indicate that a broad range of birds and mammals are highly sensitive to strychnine, including passerines, waterfowl, corvids, raptors, rodents, canids, and mustelids, whereas quail appear to be less sensitive. Acute exposure of rats to lethal dose s caused rapid toxicity, with convulsions and death occurring within one hour afte r treatment (MRID 43330301). With chronic exposure, the mallard was the most sensitive test species, with reduced growth observed at diet ary concentrations as low as 68.9 mg a.i./kg-diet (NOAEC = 33.2 mg a.i./kg-diet). Reduced egg production was observed in mallards at 141 mg a.i./kg-diet.

Table 3. Summary of Available Data on the To xicity of Strychnine to Terrestrial Animals

Study Type Surrogate Species Toxicity Value 1 (95% C.I) Effects Author, Date MRID Acceptability

Birds

Acute Avian House sparrow ( Passer domesticus ) LD 50 = 4.18 mg/kg-bw (3.18-5.50) Mortality 00160000 (Hudson et al., 1984) Acceptable

Japanese quail ( Coturnix japonica ) LD 50 = 22.6 mg/kg-bw (11.9-42.9) Mortality 00160000 (Hudson et al., 1984) Acceptable

Black-billed magpie ( Pica hudsonia ) LD 50 = 2.84 mg/kg-bw (1.0-12.1) Mortality 40815201 Supplemental

Mallard, 36 hr ( Anus platyrhyncho s) LD 50 = 2.62 mg/kg-bw (1.94-3.55) Mortality 00160000 (Hudson et al., 1984) Supplemental

Mallard, 1 week LD 50 = 2.00 mg/kg-bw (1.51-2.65) Mortality 00160000 (Hudson et al., 1984) Supplemental

Mallard, 6 months LD 50 = 2.27 mg/kg-bw (1.26-4.11) Mortality 0016 0000 Acceptable

### 7 (Hudson et al., 1984)

Subacute dietary Avian American kestrel ( Falco sparverius ) LC 50 = 237 mg/kg-diet (188-363) Mortality 40815201 Supplemental

Black-billed magpie LC 50 = 98.7 mg/kg-diet (65-129) Mortality 40815201 Supplemental

Bobwhite LC 50 = 3536 mg/kg-diet (N.R.) NOAEC: 1250 ppm Internal bleeding, pale liver, gaseous intestines, loss of reflexes, immobility, death 41322602 Acceptable

Mallard LC 50 = 212 mg/kg-diet (N.R.) NOAEC: 78 ppm Lethargy, loss of reflexes, muscle spasms, death 41322601 Acceptable

Chronic Avian Bobwhite NOAEC: 1113 mg/kgdietLOAEC: > 1113 mg/kgdiet None 42716801 Acceptable

Mallard NOAEC: 33.2 mg/kgdietLOAEC: 68.9 mg/kgdiet Chick body weight 42716802 Acceptable

Mammals

Acute oral mammalian, TGAI Laboratory rat ( Rattus norvegicus) Females: LD 50 = 2.2 mg/kg-bw Males: LD 50 = 6.4 mg/kg-bw Mortality 40908901, 41210701 Supplemental

Desert kit fox Vulpes macrotis arsipus LD 50 = 0.75 mg/kg-bw Mortality Schitoskey, 1975 E35428 Supplemental

Acute oral mammalian, 0.5% bait (Wilco Gopher Getter Type 1 Bait and Wilco Gopher Getter AG Bait) Laboratory rat ( Rattus norvegicus) Females: LD 50 : 2.9-8.7 mg/kg-bw Males: LD 50 = 15.2 mg/kg-bw Combined: LD 50 = 7.84 mg/kg-bw (4.36-13.6) Mortality 43330301 Supplemental

Subacute dietary mammalian Red fox ( Vulpes fulva ) LC 50 = 64 mg/kg-diet (37-113) Mortality 40296503 Supplemental

European ferret ( Mustela putorius ) LC 50 = 198 mg/kg-diet (148-262) Mortality 40296502 Supplemental

1 

### All toxicity values are expressed in terms of active ingredient. Values shown in bold were selected to be used in the ecological risk assessment for strychnine.

### 8 Terrestrial Field Studies

Numerous field studies have been conducted to investigate the primary and secondary poisoning hazards to non-target wildlife as sociated with rodenticide use of strychnine. Table 4 summarizes papers available in the open literature that re port on these field studies. The majority of studies evaluate risk to non-target small mammals, and secondary risk to scavengers and predators, associated with below-ground baiting to control pocket gophers in reforestation areas in the northwestern United States (Fagerstone et al., 1980; Anthony et al., 1984; Nolte and Wagner, 2001; El Hani et al., 2002). All of these stud ies have shown that below-ground placement of strychnine bait in pocket gopher burrows result in some mortality to non-target small mammals, although the losses usually had little or no long-term effects on small mammal populations. These studies also indicate that some risk of secondary exposure exists because some of the poisoned small mammals, in particular non-targ et species, will die above ground, and because some predators, such as weasels, may ente r into the burrows to scavenge pocket gopher

carcasses.

Arjo et al., 2006 evaluated resi dues in strychnine of insects feeding on carcasses. A risk assessment they conducted on insectivorous wildlife found little tertiary ri sk from consumption of strychnine-contaminated insects. Finally, Proulx and MacKenzie (2010) and Proulx (2011) studied the hazard to non-target wildlife associ ated with use of strychnine to control the Richardson ground squirrel in pastures and alfalfa fields in Saskatchewan. These studies showed similar conclusions as discussed in Arjo at al., 2006, with potential secondary exposures to poisoned mammals that died above ground, as we ll as to burrowing animals such as burrowing owls.

Table 4. Field studies published in the open lit erature on the hazard of rodenticide use of strychnine to non-target wildlife

Title Use	Studied Highlights	of	Paper Reference
Hazards	to	small	mammals associated	with	underground strychnine	baiti ng	for	pocket gophers Pocket	gopher control	in	pine reforestation

areas ● Field	study	on	mortality	and population	impacts	to	small mammals.

● Discussion	of	primary	and secondary	hazards Fagerstone	et al.,	1980

Hazards	to	golden‐mantled ground	squirrels	and	associated secondary	hazard	potential from	strychnine	for	forest secondary	pocket	gophers Pocket	gopher control	in	pine plantation ● Laboratory	toxic ity	studies	with the	golden‐mantled	ground squirrel.

● Field	study	on	mortality	and population	impacts	to	the	golden‐ mantled	ground	squirrels.

● Secondary	poisoning	feeding study	with	the	mink,	hawks	and owls. Anthony	et	al., 1984

Non‐target	impacts	of strychnine	baiting	to	reduce Pocket	gopher control	in ● Field	study	on	mortality	and population	impacts	to	golden Nolte and Wagner, 2001

### 9 pocket	gopher	populations	of forest	lands	in	the	United	States

and Response	of	non‐target	species to	underground	strychnine baiting	for	pocket	gopher	in southwest	Oregon reforestation

areas mantled	ground	squirrels	and yellow	pine	chipmunks.

● Observations	that	poisoned pocket	gophers	die	mostly underground.

● Discussion	of	secondary poisoning	hazard	to	weasels. and

El Hani et al. 2002

Potential non-target risks from strychnine-containing rodent

carcasses Pocket	gopher control	in reforestation

areas ● Evaluated	removal	of	small mammal	carcasses	by	scavengers and	insects.

● Measurement	of	strychnine concentrations	in	insects	that	feed

on	carcasses

● Assessment	of	risk	from	tertiary exposure	to	insectivores	feeding on	insects	that	feed	on	carcasses. Arjo et al. 2006

Strychnine for the control of Richardson’s ground squirrels: efficiency and selectivity issues

and Field evidence of non-target and secondary poisoning by strychnine and chlorophacinone used to control Richardson’s ground squirrels in southwest Saskatchewan Richardson’s ground squirrel control in grasslands and alfalfa fields ● Counted Richardson’s ground squirrels found dead on surface following strychnine baiting in Canada.

● Monitoring	of	mortality	of	non‐ target	wildlife.

● Discussion	of	secondary	hazard to	burrowing	owls. Proulx and MacKenzie, 2010

and
Proulx, 2011



### In addition to these field studies results reported in the open literatur e, six field studies have been submitted to the EPA by registrants in support of strychnine registration (Appendix A). These studies have been reviewed and disc ussed in previous risk assessments.

A field efficacy study conducted with strychnine baits (0.5, 1.15, and 1.8 % w:w) to control the Valley pocket gopher (Thomomys bottae) was assessed (MRID# 42488601; USEPA, 1994). Strychnine residues were found in the muscle tis sue of the gophers; the mean was approximately 0.5 ppm and ranged as high as 5.4 ppm. It was also found in the gastrointe stinal tract with a mean of approximately 5 ppm and as high as 35.8 ppm. Three dead vertebrates were found: a horned lark ( Eremophila alpestris ), a brewer’s blackbird ( Euphagus cyanocephalus ) and a striped skunk ( Mephitis mephitis ). Strychnine residues in th e horned lark were 0.3491 and 1.6133 ppm for the muscle tissue and gast rointestinal tract, respectively and, for the brewer's blackbird they were 0.5606 and 23.3283 ppm for the muscle ti ssue and gastrointestin al tract, respectively. The skunk was not analyzed for strychnine residues. This study confirmed the possibility of secondary exposure ( i.e. , dead gophers were preyed upon by red-tailed hawks) and that direct exposure occurs to birds.

### 10 b. Toxicity to Aquatic Animals

Aquatic toxicity data on strychnine are limite d to acute toxicity to freshwater fish and crustaceans. These tests classify strychnine as highly toxic to fish, and slightly to moderately toxic to aquatic invertebrates.

Table 5. Summary of Available Data on the Toxicity of Strychnine to Aquatic Animals
Study Type Surrogate Species Toxicity Value 1 LC 50 /EC 50 (95% C.I.) MRID Acceptability

Freshwater fish and aquatic-phase amphibians Acute Rainbow· trout (Oncorhynchus mykiss) 2.3 mg/L (1.7-3.2) 41126501 Acceptable
Bluegill sunfish (Lepomis macrochirus) 0.76 mg/L (0.61-0.96) 41126502 Acceptable

Chronic Waived -- -- -- Freshwater invertebrate

Acute Waterflea ( Daphnia magna) 10.6 mg/L (9.0-12.4) 41126503 Acceptable

1 

### All toxicity values are expressed in terms of active ingredient.



### c. Toxicity to Plants

No data are currently available on the toxicity of strychnine to terrestr ial or aquatic plants.

d. Ecological Incidents

A query of the Ecological Incident Information System (EIIS, version 2.1) was completed in August of 2015 to identify ecological incident of adverse field effects associated with the rodenticide use of strychnine. Ther e were 85 incidents in this database that were attributed to exposure to strychnine. The only incident involving aquatic organi sms was an incident of fish dying in a reservoir from strychnine exposure (B0000-227-002). This in cident was caused by intentional fouling of a reservoir with strychni ne, and therefore does not reflect exposure from legal rodenticide use.

The remaining 84 reported incidents involved mort ality of non-target wildlife. The wildlife incidents that occurred prior to April 1988 are less relevant for assessing current use of strychnine because, prior to that date, above-ground uses of strychnine bait were permitted, and these uses were likely to have caused much more exposure to non-target species than the current below-ground uses. In addition, us es of strychnine to control other vertebrate pests besides pocket gophers were permitted during these early years but have since been cancelled. Of the 38 reported incidents occurring since April 1988, 31 are either associated with a registered rodenticide use of strychnine, or the legality of the use could not be determined. These incidents, which are summarized in Table 6, will be the primar y set of incidents used to evaluate non-target wildlife risks associated with curr ent uses of strychnine. Reported incidents occurring since April 1988 that have been identified as being the result of illegal use of strychni ne are listed in Table 7.

### 11 Further evaluation of these incidents listed in Ta ble 6 may identify additional incidents that are associated with misuse of strychnine.

Table 6. Wildlife Mortality Incidents Attri buted to Strychnine Poisoning, Excluding Known Misuses, Occurring since 1988

Incident ID Location Date Legality Certainty Species No. Dead

I013810-022 San Diego, CA 3/15/1989 Unknown Probable Blackbird 1

I007651-002 I013810-019 Yolo, CA 12/11/1990 Unknown Highly Probable Dunlin (36), killdeer (2) 38 I005525-002 Siskiyou, CA 1/29/1991 Unknown Probable Goose 6
I005525-003 Fresno, CA 2/5/1991 Unknown Highly Probable Sparrow (2), dove(1) 3

I003351-022 El Dorado, CA 6/23/1994 Unknown Highly Probable Canada Goose (32), California gull (1), mallard (1) 34

I003351-023 Fresno, CA 7/7/1994 Unknown Highly Probable Goose (17) 17

I004993-007 San Bernardino, CA 5/30/1996 Unknown Probable Mallard (30) 30

I010002-003 Marin, CA 2/3/1999 Unknown Highly Probable Rock dove 17

I010002-016 Marin, CA 4/30/1999 Unknown Highly Probable Rock dove 4

I010002-023 I010002-024 Marin, CA 9/23/1999- 9/30/1999 Unknown Highly Probable Rock dove 11

I018980-021 Washburn, WI 4/1/2000 Unknown Highly Probable Brewer's blackbird (10), brown-headed cowbird (10), red-winged blackbird (10) 30

I020627-027 Franklin, WA 5/19/2001 Unknown Highly Probable Dog

I018980-016 Hall, HA 6/15/2002 Unknown Highly Probable Mallard 22

I018980-019 Sandoval, NM 9/26/2005 Unknown Highly Probable American coot, mallard 30

I019703-002 Maricopa, AZ 10/12/2007 Unknown Possible Dove (1), mourning dove (2), house sparrow (3), unidentified species (52) 58

I019703-009 Maricopa, AZ 1/30/2008 Unknown Highly Probable Inca dove, mourning dove, pigeon 20

I020995-002 Rice, CA 12/16/2008 Unknown Possible Canada goose (55), goose (47), mallard 190

### 12(1), whitefronted goose (87)
I023104-001 Kern, CA 11/1/2010 Unknown Highly Probable San Joaquin Kit Fox 4

I023104-002 Kern, CA 1/10/2011 Registered Use Highly Probable San Joaquin Kit Fox 1

I023104-003 Kern, CA 1/27/2011 Registered Use Highly Probable San Joaquin Kit Fox 1

I023104-004 Kern, CA 1/31/2011 Registered Use Highly Probable San Joaquin Kit Fox 1

I024443-014 San Diego, CA 6/15/2011 Unknown Highly Probable Duck approx. 30
I024821-002 Kern, CA 6/27/2011 Unknown Highly Probable San Joaquin Kit Fox 1

I025049-001 I026953-008 McClain, OK 3/3/2013 Unknown Highly Probable Meadowlark, mourning dove, red-winged blackbird 80-100

I025151-001 Riverside, CA 3/3/2013 Unknown Highly Probable Goose Several

I026953-011 Midland, TX 7/12/2013 Unknown Highly Probable Dove

I026953-001 Maricopa, AZ 1/15/2014 Unknown Highly Probable Dove, greattailed grackle, Inca dove, mourning dove, pigeon 18

I026174-001 I026953-002 El Dorado, CA 1/28/2014 Unknown Highly Probable Brewer's blackbird over 30

I026261-001 Trinity, CA 2/10/2014 Unknown Highly Probable Dog 1

I026953-005 Ector, TX 10/22/2014 Unknown Highly Probable White-winged dove 6

I024528-029 I025150-007 Kern, CA 

### 5/30/2012 Unknown Highly Probable Mourning dove (many), sparrow (few), dog (1), raptor (1) 30-50



### Table 7. Wildlife Mortality Incidents Attributed to Misuse of Strychnine Occurring since 1988

Incident ID Location Start Date Certainty Species No. Dead

I001566-002 NE 10/1/1994 Probable Sparrow (285), owl (2), blue jay (1) 288

I006925-001 Wise, VA 3/11/1998 Highly Probable Crow 4

I011233-001 Henderson, TX 6/1/2001 Probable Birds (several), dog (1) Several

I017034-001 Tuolumne, CA 1/11/2006 Probable Red-winged blackbird (6), birds (>100) >100

### 13 I021792-003 Wabasha, MN 12/18/2009 Highly Probable Dog 2

I024152-010 San Luis Obispo, CA 4/9/2011 Highly Probable Red fox 1



### The 47 reported incidents that occurred before April 1988 are shown in Table 8. While they may not represent non-target wildlife exposure from current below-ground uses of strychnine, they do provide information on the non-target species that mi ght be impacted if they were to gain access to the strychnine bait, or ingest ot her animals that had access to the bait.

Table 8. Wildlife Mortality Incidents Attribut ed to Strychnine Poisoning Occurring before April 1988

Incident ID Location Date Legality Certainty Species No. Dead
B0000-503-18 Yolo, CA 1/1/1966 Misuse (accidental) Highly Probable Deer 2

B0000-503-19 San Benito, CA 1/1/1968 Registered Use Probable Dove 50

B0000-503-10 Torrance, NM 2/7/1972 Misuse (intentional) Highly Probable Bald eagle 1

B0000-300-83 MI 5/4/1973 Misuse (intentional) Probable Birds 15

B0000-503-24 San Bernardino, CA 12/1/1973 Registered Use Probable Canada goose 14

B0000-503-45 Siskiyou, CA 5/1/1974 Unknown Highly Probable Ring-billed gull 11

B0000-503-25 Canyon, ID 6/3/1976 Suspected misuse Highly Probable Starlings,robins, greathorned owl, short-eared owl, goshawk Thousands

B0000-503-28 Whitman, WA 6/4/1976 Unknown Highly Probable Mourning dove 5

B0000-503-33 Douglas, WI 4/30/1976 Unknown Highly Probable Blackbird 6 B0000-503-09 Carbon, UT 2/22/1977 Unknown Probable Bald eagle 1 B0000-503-12 B0000-503-13 Conejos, CO 3/6/1977 Unknown Highly Probable Bald eagle 2

B0000-503-06 Kossuth, IA 4/9/1978 Unknown Highly Probable Bald eagle 1

B0000-503-36 St. Louis, MN 2/16/1978 Unknown Highly Probable Rough legged hawk, owl, pigeon 3

B0000-503-16 Ketchikan, AK 6/21/1979 Unknown Probable Bald eagle 1

B0000-503-17 Ketchikan, AK 8/1/1979 Unknown Highly Probable Bald eagle 1

B0000-503-29 B0000-503-42 Franklin, OH 6/11/1979 Misuse (intentional) Highly Probable Mourning dove, Killdeer, other 8

### 14 migratory birds
B0000-503-50 Kiowa, CO 1/12/1979 Unknown Highly Probable Golden eagle 1

B0000-503-01 Newport News City, VA 12/29/1980 Unknown Highly Probable Peregrine falcon 1

B0000-503-04 Denver, CO 1/5/1980 Unknown Highly Probable Prairie falcon 3

B0000-503-08 Baltimore City, MD 11/1/1980 Unknown Probable Peregrine falcon 1

B0000-503-31 Butler, OH 12/12/1980 Registered Use Highly Probable N/R 17

B0000-503-47 Rawlins, KS 12/23/1980 Unknown Highly Probable Golden eagle 1

B0000-503-07 Baltimore City, MD 8/7/1981 Unknown Highly Probable Peregrine falcon 1

B0000-503-14 Modoc, CA 3/16/1981 Unknown Highly Probable Bald eagle 1

B0000-503-32 York, PA 8/4/1981 Misuse (accidental) Highly Probable American kestrel 3

B0000-503-35 Tom Green, TX 1/28/1981 Unknown Highly Probable Golden eagle, jackrabbit (2) 3

B0000-503-39 Modoc, CA 3/13/1981 Unknown Highly Probable Golden eagle 1

B0000-503-41 Ramsey, MN 2/7/1981 Unknown Highly Probable Great-horned owl 4 B0000-503-48 Grant, KS 3/13/1981 Unknown Probable Golden eagle 1 B0000-300-88 B0000-503-03 Ferguson, MT 4/21/1982 Registered Use Highly Probable Bald eagle 1

B0000-503-26 Alameda, CA 10/20/1982 Unknown Highly Probable Canada goose 8

B0000-503-27 King, WA 6/2/1982 Misuse (intentional) Highly Probable Mallard 1

B0000-503-34 Jefferson, NY 5/19/1982 Misuse (intentional) Highly Probable Bear 1

B0000-503-40 Ramsey, MN 3/26/1982 Unknown Highly Probable Great-horned owl 1

B0000-503-46 Pierce, WA 1/27/1982 Unknown Highly Probable Glaucous gull, mallard, rock dove 9

I013810-017 King, WA 1/27/1982 Unknown Probable Peregrine falcon 1 I013810-018 Pierce, WA 5/1/1982 Unknown Probable Duck (10) 10 B0000-503-05 Talbot, MD 1/21/1983 Unknown Probable Bald eagle 1 B0000-503-15 Navajo, AZ 1/22/1983 Unknown Highly Probable Bald eagle 1

B0000-503-38 Baltimore City, MD 4/28/1983 Unknown Highly Probable Peregrine falcon 1

B0000-503-43 Hubbard, MN 5/4/1983 Unknown Highly Probable Red-tailed hawk 1

B0000-503-02 Judith Basin, MT 4/6/1984 Unknown Highly Probable Bald eagle 1

### 15 B0000-503-11 Judith Basin, MT 4/18/1984 Registered Use Highly Probable Bald eagle 1

B0000-503-30 Deschutes, OR 8/30/1985 Misuse (intentional) Highly Probable Blue jay, Brewer's blackbird, cowbird, chipmunk, green-tailed towhee, house finch, mourning dove 15

B0000-503-44 Modoc, CA 3/21/1985 Misuse (intentional) Highly Probable Red-tailed hawk 3

B0000-503-49 Thomas, KS 12/4/1986 Unknown Highly Probable Golden eagle 1



### A review of the Avian Monitoring Information System (AIMS), which is maintained by the American Bird Conservancy, identified 55 avia n incidents associated with exposure to strychnine. All but four of these incidents were ones that are also recorded in the EIIS database. The four incidents not included in EIIS are de scribed in Table 9. The incident occurring in Washburn, Washington in 2000 that re sulted in the deaths of a pproximately 30 blackbirds and cowbirds (AIMS ID # 1741) was attributed to use of strychnine for pocket gopher control, although it is not known if the applic ation was done legally. The stry chnine uses associated with the other three report ed incidents are unknown.

Table 9. Bird Mortality Incident s Attributed to Strychnine Po isoning that Are Reported in the AIMS Database but not Reported in EIIS
AIMS Incident ID Location Date Legality Certainty Species No. Dead

2191 Washington, NY 4/23/1973 Unknown Possible Blue jay(2),

common grackle (6) 8

2251 Modoc, CA 4/1/1987 Unknown Probable Bald eagle 1 2252 Modoc, CA 3/19/1995 Unknown Probable Bald eagle 1

1741 Washburn, WA 4/1/2000 Unknown Highly Probable Red-winged blackbird, Brewer’s blackbird, cowbird 30



### In addition to the incidents reco rded in EIIS and AIMS, the Agen cy maintains a database that stores counts of minor incidents th at pesticide registrants record in quarterly aggregated incident reports. Ecological incidents recorded in these ag gregated reports include those categorized as ‘minor fish or wildlife’ (W-B), ‘minor plant’ (P-B), and ‘other non-target’ (ONT) incidents. A review of this database in August 2015 identify no reported fish or wildlife, plant, or other nontarget incident attributed to a product cont aining strychnine as the active ingredient.

### 16 

## 7. Exposure Pathways of Concern

The primary route of exposure to strychnine ba it would be from terrest rial wildlife directly consuming the bait (primary exposure), or by cons uming animals that have fed recently on the bait and contain significa nt residues of strychnine within their bodies (secondary poisoning). Numerous field studies have documented primary poisoning of non-target animals from belowground application of gopher bait containing strychnine (Fagerstone et al., 1980; Anthony et al., 1984; Nolte and Wagner, 2001; El Hani et al ., 2002). Small fossorial rodents like ground squirrels and chipmunks, which may enter into poc ket gopher burrows, are part icularly at risk of primary exposure (Anthony et al. 19 84, El Hani et al., 2002). Also, for the special local need use of strychnine in the state of Nevada (EPA Reg. No. NV830009), the labe l requires strychnine bait to be placed 8 inches down the opening of th e burrows of the yellow-bellied marmot and ground squirrel; however, considerin g the large opening of the burro ws of these species, this depth may not be enough to prevent some anim als from accessing the bait. Primary poisoning of non-target species has been observed with use of strychnine for ground squirrel control in Canada (Proulx and MacKenzie, 2010; Proul x, 2011). Secondary exposure may occur when predators or scavengers consume a pocket gopher or non-target animal that has consumed the strychnine bait. Because strychnine is a very fast-acting poison, prey animals that consume a lethal dose of strychnine bait ar e expected to die before they have absorbed and assimilated a significant amount of strychnine re sidues into their tissue. However, those animals may die with a significant amount of strychnine remaining with in their gastrointestin al tract, with a high enough dose that could be lethal to the predat or/scavenger. Furthermore, pocket gophers and other seed-eating rodents with cheek pouches, such as ground squirrels and chipmunks, may have a significant amount of st rychnine bait remaining stored within their cheek pouch when they die (Hegdal and Gatz, 1976).

Pocket gophers poisoned by strychnine mostly die underground (Nolte and Wagner, 2001; El Hani et al., 2002), which would likely limit exposu re to predators and scavengers. Secondary poisoning may occur to some predators that may access the dead and dying pocket gophers by entering into their underground burrows ( e.g. , weasels and snakes). Other predators and scavengers may dig to access the gophers underg round, or may be exposed to the occasional gopher or other non-target animals that di es above ground. Ground squirrels poisoned by strychnine mostly die above ground (Anthony et al., 1984), and therefor e, there is a higher potential for secondary poisoning from the use of strychnine in Nevada for ground squirrel control.

Conceivably, tertiary exposure could occur if insects feed on the carcasses of poisoned rodents, and then insectivores feed on the contaminated in sects. Arjo et al. (2006) measured strychnine residues in insects collecte d from carcasses of strychni ne poisoned pocket gophers, and conducted a risk assessment to eval uate the potential for risk from this route of exposure to three species of insectivorous animal s, the house sparrow, the house mouse, and the bullfrog. Risk quotients were calculated based on predicted diet ary exposures from this route and estimated LD 50 

### values for these species. Risk quotients ranged from 0.009 to 0.064, indicating negligible risk from this route. Therefore, tertiary exposure to insectivores will not be further considered as a significant route of exposu re in the risk assessment.

### 17 Strychnine is not expected to volat ilize; therefore, very little i nhalation exposure to strychnine is expected, even to animals that enter treated burrows. Some derm al exposure would be possible, but only to small mammals, amphibians, and re ptiles which might enter into treated pocket gopher burrows. Dermal exposure may be particularly significant to amphib ians because they are susceptible to absorbing contaminants through the seat patch, an area of absorbant skin on their lower abdomen used to absorb water. Dermal exposure would likely be less than exposure from direct consumption of bait, but may be important to amphibians which may enter into the treated burrows but would not consume the gopher bait.

Use of strychnine is limited to bait placed be low the ground within burrow systems, which is expected to greatly limit potential surface water contamination. Additionally, adsorption/ desorption data show that stryc hnine binds strongly to soil, limiting movement through the soil profile. Therefore, strychnine expos ure to fish, aquatic invertebrate s, and aquatic plants is not a significant exposure route of concern.

Placement of strychnine bait in underground burrows of rodents is not expected to result in significant exposure to plants. Any absorption of strychnine residues from the soil would be minimal and extremely localized. As very little strychnine is expected to be absorbed and translocated into the flowers of plants, exposur e to pollinators is assumed to be negligible.



## 8. Analysis Plan

The only stressor of concern that will be cons idered in the risk assessment is the parent compound, strychnine. The risk assessment will be focused 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. Risk quotients for primary exposure will be calculated by dividing of the strychnine concentration in the bait (5000 mg a.i./kg) to dietary LC 50 

### of birds and mammals measured in subacute dietary toxicity studi es. In addition, dose-based terre strial risk q uotients will be calculated by predicting the doses (mg a.i./kg-bodyweight) that bi rds and mammals would ingest if they were to feed on strychnine bait, a nd then dividing those doses by the acute oral LD 50 

### values obtained in acute toxicity tests with the mallard and the laboratory rat. The number of grains of strychnine bait th at birds and mammals would need to consume to reach the LD 50 

### will also be calculated as an other index for assessing ri sk from primary exposure.

Risk to terrestrial wildlife from secondary exposure will also be assessed with dietary- and dosebased risk assessments. First, the amount of strych nine that is potentially contained within the body of a small mammals will be es timated. The northern pocket gopher ( Thomomys talpoides ) and the golden mantled-ground squirrel ( Spermophilus lateralis ) will be used as model prey species. Strychnine residues in the prey will be based on the estimated amount of strychnine bait grains that could be present with in the GI tract and cheek pouches of an animal that has been feeding on the bait, and the strychnine concentr ation in the bait (0.5%). A dietary-based risk assessment will be conducted by comparing the predicted whole- body concentration of strychnine in the modeled prey to the dietary LC 50 

### of the red fox and the American kestrel. Dosebased risk assessments will be conducted for predatory mammals using the red fox and the red-

### 18 tailed hawk ( Buteo jamaicensis ) as model species. A daily dose (mg a.i./kg-bodyweight) will be predicted for these species based on the assumption that they cons ume the strychnine-killed prey at their average daily food intake rate. Acute risk quotients will be calculated by dividing the daily dose by the acute LD50 for birds and mammals. The acute oral LD 50 

### measured in the desert kit fox ( Vulpes macrotis arsipus ), 0.075 mg a.i./kg-bodyweight (S chitoskey, 1975) will be used for the red fox RQ. Because no acute LD 50 

### is available for a predatory bird species, the acute oral LD 50 

### of the mallard will be used. In addition to these assessments , the secondary-poisoning risk assessments for owls, hawks and minks that we re reported in Anthony et al. (1984) will be evaluated.

Chronic risk quotients will be calculated for birds by dividing the chronic mallard NOAEC by the predicted dietary concentration of strychnine in strychnine ba it (for primary exposure) and in strychnine-killed pocket gophers and ground squirrels (for sec ondary exposure).

As in previous risk assessments, exposure to te rrestrial plants, bees, a nd aquatic organisms is assumed to be negligible from underground st rychnine bait uses, a nd therefore no risk assessment will be conducted to these groups of organisms.



## 9. Status of Fate and Ecological Effects Data

a. Environmental Fate

Table 10 identifies the environmental fate studies submitted for strychnine for each guideline requirement, as well as study cl assifications. With the limite d dissipation or movement of strychnine expected to occur in the environment, no further fate data are needed in order to support the pending risk assessment.

Table 10. Submitted Environmental Fate Data for Strychnine.

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed to conduct risk assessment? 835.2120 Hydrolysis 4 1122301 Acceptable No 835.2240 Aqueous photolysis -- -- No 835.2410 Soil photolysis 42973401 Acceptable No

835.4100 Aerobic soil metabolism 42234201 and 43407601 Supplemental 1 No

835.4200 Anaerobic soil metabolism -- -- No 835.4300 Aerobic aquatic metabolism -- -- No 835.4400 Anaerobic aquatic metabolism -- -- No
835.1230 835.1240 Adsorption/ desorption and l eaching 42366501 Acceptable No
835.1410 Volatility – laboratory -- -- No 835.6100 Terrestrial field dissipation -- -- No

850.6100 Environmental Chemistry Method and Independent Laboratory Validation -- -- No

850.1730 Fish bioconcentration -- -- No

### 19 1 The aerobic soil metabolism studies did not use radiolabeled material and thus material balances and degradate identification were not completed. However, sufficient in formation was provided to allow determination of the halflife of parent strychnine.



### b. Ecological Effects

Available ecotoxicity data for terrestrial or ganisms are shown in Table 11. No additional terrestrial data are needed for completing the ecological risk a ssessment. Toxicity data on honey bees and terrestrial plants are not needed because th e use of strychnine is limited to solid bait that is placed below ground for rodent co ntrol, and this use is not exp ected to result in significant exposure to insect pollinato rs or terrestrial plants.

Table 11 . Available Terrestrial Ecological Effects Data for Strychnine

OCSPP Guideline Data Requirement Submitted Studies (MRID) Test Species Study Classifications Are data needed for risk assessment? Current Additional Data Need

850.2100 Avian oral toxicity 00160000 Mallard Acceptable

No -- 00160000 Japanese quail Acceptable

00160000 House
sparrow Acceptable

40815201 Blackbilled magpie Supplemental

850.2200 Avian dietary toxicity 41322602 Bobwh ite Acceptable

No -- 41322601 Mallard Acceptable

40815201 American kestrel Supplemental

40815201 Blackbilled magpie Supplemental

850.2300 Avian reproduction 42716801 Bobwh ite Acceptable No -- 42716802 Mallard Acceptable

Nonguideline Avian inhalation -- -- (N/A) No Because inhalation is not expected to be a significant route of exposure for below-ground bait use, an avian inhalation study is not requested.

870.1100 Acute oral mammalian, TGAI 40908901, 41210701 Laboratory
rat Supplemental No --

### 20 OCSPP Guideline Data Requirement Submitted Studies (MRID) Test Species Study Classifications Are data needed for risk assessment? Current Additional Data Need

870.1100 Acute oral mammalian, TEP 43330301 Laboratory
rat Supplemental No --

870.3150 Subacute dietary mammalian 40296503 Red fox Supplemental
No 40296502 European ferret Supplemental --

870.4100 Chronic Mammalian -- -- -- No --

850.3020 Honey bee acute contact toxicity -- -- -- No

Because underground bait use is expected to result in negligible exposure to insect pollinators, no bee studies are being requested.Nonguideline Honey bee acute oral toxicity -- -- -- No

Nonguideline Honey bee chronic larvae toxicity -- -- -- No

Nonguideline Honey bee chronic adult toxicity -- -- -- No

850.3030 Honey bee residue on foliage -- -- -- No

850.3040 Field testing for pollinators -- -- -- No

850.4100 Seedling Emergence and Seedling Growth -- -- -- No Because underground bait use is expected to result in negligible exposure to terrestrial plants, no terrestrial plant studies are requested. 850.4150 Vegetative Vigor -- -- -- No



### Available ecotoxicity data for aquatic orga nisms are shown in Table 12. Acceptable acute toxicity data are available for freshwater fish and freshwater invertebrates. Because the belowground rodenticide use of strychnine bait applied is not expected to result in significant exposure to aquatic ecosystems, all other aquatic toxicity data requirements have been waived, including studies with saltwater species a nd all chronic toxicity studies.

### 21 Table 12 Submitted Aquatic Ecological Effects Data for Strychnine

OCSPP Guideline Data Requirement Submitted Studies (MRID) Test Species Study Classifications Are data needed to conduct risk

assessment?

850.1010 Freshwater invertebrate acute toxicity 41126503 Water flea Acceptable No

850.1035 850.1045 Saltwater crustacean acute toxicity (Waived) -- -- No

850.1025 850.1055 Saltwater bivalve acute toxicity (Waived) -- -- No

850.1075 Freshwater fish acute toxicity 41126502 Bluegill sunfish Supplemental No 41126501 Rainbow trout Supplemental

850.1075 Saltwater fish acute toxicity (Waived) -- -- No

850.1300 Freshwater invertebrate life cycle (Waived) -- -- No

850.1350 Saltwater invertebrates life cycle (Waived) -- -- No

850.1400 Freshwater fish early-life stage (Waived) -- -- No

850.1400 Saltwater fish early-life stage (Waived) -- -- No

850.1500 Fish life cycle (Waived) -- -- No

850.4400 Aquatic plant Toxicity Test using Lemna spp. (Waived) -- -- No

850.4500 Algal toxicity (Waived) -- -- No
850.4550 Cyanobacteria (Waived) -- -- No



## 10. Endangered Species Assessments

Consistent with EPA’s responsib ility under the Endangered Species Act (ESA), the Agency will evaluate risks to federally listed threatened and endangered (listed) species from registered uses of pesticides in accordance with the Joint In terim Approaches developed to implement the recommendations of the April 2013 Nationa l Academy of Sciences (NAS) report, Assessing Risks to Endangered and Threat ened Species from Pesticides . The NAS report outlines recommendations on specific scientific and tech nical issues related to the development of pesticide risk assessments that EPA and the Se rvices must conduct in connection with their obligations under the ESA and FIFRA. EPA will ad dress concerns specific to strychnine in connection with the development of its fina l registration review decision for strychnine

. In November 2013, EPA, the U.S. Fish and Wild life Service, National Ma rine Fisheries (the Services), and USDA released a white paper containing a summary of their joint Interim Approaches for assessing risks to listed species from pesticides. These Interim Approaches were developed jointly by the agencies in respons e to the NAS recommendations, and reflect a

### 22 common approach to risk assessment shared by th e agencies as a way of addressing scientific differences between the EPA and the Services. Details of the joint Interim Approaches are contained in the November 1, 2013 white paper

, Interim Approaches for National-Level Pesticide Endangered Species Ac t Assessments Based on the Recommendations of the National Academy of Sciences April 2013 Report.

Given that the agencies are continuing to de velop and work toward implementation of the Interim Approaches to assess the potential risk s of pesticides to listed species and their designated critical habitat, th is ecological problem formulati on supporting the Preliminary Work Plan for strychnine does not desc ribe the specific ESA analysis, including effects determinations for specific listed species or designated critical habitat, to be conducted during registration review. While the agencies continue to devel op a common method for ESA analysis, the planned risk assessment for the registration review of stry chnine will describe the level of ESA analysis completed for this particular registration review case. This 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 agenci es have been fully vetted. Once the agencies have fully developed and implemented the scie ntific methods necessary to complete risk assessments for listed species and their designated critical habitats, these methods will be applied to subsequent analyses of strychnine as pa rt of completing this registration review.



## 11. Endocrine Disruptor Screening Program

Strychnine was not included in the first group of 67 chemicals issued an order to conduct Tier 1 EDSP testing. For additional info rmation the EDSP program, visit http://www.epa.gov/endo/

.



## 12. Clean Water Act Programs

Strychnine has not been identif ied as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act 2 

### . In addition, no Total Maximum Daily Loads (TMDL) have been developed for strychnine 3 

### . More information on impaired water bodies and TMDLs can be found at the Agency’s website 4 

### . The Agency invites submission of water quality data for this pesticide. To the exte nt possible, data should conform to the quality standards in Appendix A of the OPP Standard Operating Procedur e: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s Regist ration Review Risk Assessment and Management Process 5 

### in order to ensure they can be us ed quantitatively or qualitatively in pesticide risk assessments. Aquatic benchmarks 6 

### have not been established for these chemicals. Any data submitted or otherwise located as part of the registration review process may be used to update aquatic life benchmar ks, if applicable.

2 http://iaspub.epa.gov/tm dl_waters10/attains_nation_cy.ca use_detail_303d?p_cause_group_id=885

3 http://iaspub.epa.gov/tmdl_w aters10/attains_nation.tmd l_pollutant_detail?p_pollutant _group_id=885&p_pollutant_group_name= PESTICIDES

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

5 http://www.epa.gov/oppsrrd1/registra tion_review/water_quality_sop.htm

6 http://www.epa.gov/oppefed1/ecoris k_ders/aquatic_life_benchmark.htm

### 23 

## 13. References

Anthony, R.M., G.D. Lindsey, and J. Evans. 1984. Hazards to golden-mantled ground squirrels and associated secondary hazard potential fr om strychnine for forest secondary pocket gophers. Proceedings of the Eleventh Ve rtebrate Pest Conference (1984). Paper 2. Available online: http://digitalcommons.unl.edu/vpc11/2

. Arjo, W.M., K.K. Wagner, D.L. Nolte, S.S. Stah l, and J. J. Johnston. 2006. Potential non-target risks from strychnine-containing rodent carcasses. Crop Protection 25:182-187.

Arjo, W.M. and D.T. Bryson. 2007. Reduc ing non-target hazards of rode nticides in forest settings. In Proceedings of the 12 th 

### Wildlife Damage Conference ( D.L. Nolte, M. Argo, and D H. Stalman, Eds .)

El Hani, A., D.L. Nolte, J.R. Mason, and S. Bulkin. 2002. Response of non-target species to underground strychnine baiting for pocket gopher in southwest Or egon. Western Journal of Applied Forestry. 17(1): 9-13.

Fagerstone, K., V.G. Barnes, Jr., M. Anthony, and J. Evans. 1980. Hazards to small mammals associated with underground strychnine baiti ng for pocket gophers. Proceedings of the 9 th 

### Vertebrate Pest Conference (1980). Paper 10.

Hegdal and Gatz, 1976. Hazards to wildlife associated with underground strychnine baiting for pocket gophers. Proc. 6 th 

### Vert. Pest. Conf., Monterey, CA, p. 258-266.

Hudson, R.H., R.K. Tucker and M.A. Haegele. 1984. Handbook of toxicity of pesticides to wildlife. USDI Resource Publication No. 153. Washington, DC. 92 pp. MRID 00160000.

Nolte, D. and K. Wagner. 2001. Non-target impact s of strychnine bai ting to reduce pocket gopher populations of forest lands in the United States. USDA National Wildlife Research Center – Staff Publications. Paper 607.

Proulx, G., N. Mackenzie, K. Mackenzie, K. Walsh, B. Proulx, and K. Stang. 2010. Strychnine for the control of Richardson’s ground squirrel s: efficiency and selectivity issues. Proc. 24 th 

### Vertebr. Pest. Conf. (R.M. Timm and K.A. Fagerstone, Eds.) Univ. of Calif., Davis. 2010 Pp. 125-128.

Proulx, G. 2015. Field evidence of non-target and secondary poisoning by strychnine and chlorophacinone used to control Rich ardson’s Ground Squirrels in Southwest Saskatchewan. In Proc. 9 th 

### Prairie Conserv. and Endang. Species Conf. Winnipeg, Manitoba. 2010. Pp. 128-134.

USEPA, 1993. Wildlife Exposure Factor Handbook . Office of Research and Development, U.S. Environmental Protection Agen cy. Washington, DC. EPA/600/R-93/187a

### 24 

## Appendix

OPPIN Bibliography

Ecotoxicity



## 71-1 Avian Si ngle-Dose Oral Toxicity

MRID Citation Reference

40815201 Garrison, M.; Schafer, E.; Harris, P.; et al. (1988) Dietary LC50 of Strychnine Alkaloid to the Black-billed Magpie and American Kestrel: BDC 896.39. Prepared by USDA, Denver Wildlife Research Center. 29 p.



## 71-2 Avia n Dietary Toxicity

MRID Citation Reference

41322601 Pedersen, C. (1989) Strychnine: Avian Di etary LC50 (8 Day) in Mallard Ducklings: Lab Project Number: 89/DC/128. Unpublished study prepared by Bio-Life Associates, Ltd. 76 p.
41322602 Pedersen, C. (1989) Strychnine: Avian Di etary LC50 (8 Day) in Bobwhite Quail: Lab Project Number: 89/QC/131. Unpublished study prepared by Bio-Life Associates, Ltd. 78 p.



## 71-4 Avian Reproduction

MRID Citation Reference

42716801 Pedersen, C.; DuCharme, D.; Lesar, C. (1993) Strychnine Alkaloid: Toxicity and Reproduction Study in Bobwhite Quail: Lab Project Number: 89 QR 37: QA-207. Unpublished study prepared by Bio-Life Associates, Ltd. 1053 p.
42716802 Pedersen, C.; Lesar, C. (1993) Strychnine Alkaloid: Toxicity and Reproduction Study in Mallard Ducks: Lab Project Number: 89 DR 33: QA-206. Unpublished study prepared by Bio-Life Associates, Ltd. 1342 p.



## 71-5 Simulated or Actual Field Testing

MRID Citation Reference

### 25 40022016 Marsh, R.; Schmidt, R.; Howard, W. (19 86) Secondary Hazards to Coyotes of Ground Squirrels Poisoned with 1080 or Strychni ne. Unpublished study prepared by Univ. of Calif., Davis. Wildlife and Fisheries Biology. 17 p.
40936908 Hegdal, P.; Gatz, T. (1977) Hazard s to Wildlife Associated with Underground Strychnine Baiting for Pocket Gophers. Final Report. Denver Wildlife Research Center. EPA-IAG-D4-0449, 53 pp.
40936909 Hegdal, P.; Gatz, T. (1976) Hazard s to Wildlife Associated with Underground Strychnine Baiting for Pocket Gophers. Proc Vertebrate Pest Control Conference 7:258-266, 12 pp.
41147801 Savarie, P.; Matschke, G. (1989) Secondary Feeding Hazard of Strychnine to the Domestic Ferret: Final Report: Project ID 612.31. Unpublished study prepared by Denver Wildlife Research Center. 87 p.
42027201 Hegdal, P.; Gatz, T. (1977) Hazard s to Wildlife Associated with Underground Strychnine Baiting for Pocket Gophers. Unpublished study prepared by Denver Wildlife Research Center. 53 p.
42488601 Poche, R. (1992) Field Evaluation of Three Concentrations of Strychnine Baits (0.5, 1.15, and 1.8% Strychnine) to Control t he Valley Pocket Gopher (Thomomys bottae) in California Using an Artificial Burr ow Builder: Lab Project Number: 91001. Unpublished study prepared by Genesis Labs. 108 p.



## 72-1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

41126501 Bowman, J. (1989) Acute Toxicity of Strychnine to Bluegill Sunfish (Lepomis macrochirus): Project ID: 37645. Unpublis hed study prepared by Analytical Biochemistry Laboratories, Inc. 79 p.
41126502 Bowman, J. (1989) Acute Toxicity of Strychnine to Rainbow Trout (Salmo gairdneri): Project ID: 37646. Unpublish ed study pre- pared by Analytical Biochemistry Laboratories, Inc. 89 p.



## 72-2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

41126503 Forbis, A. (1989) Acute Toxicity of Strychnine to Daphnia magna: Project ID: 37647. Unpublished study prepared by Analyt ical Bio-chemistry Laboratories, Inc. 80 p.
93203006 Elias, D. (1990) H Interdonati In c. Phase 3 Summary of MRID 41126503. Strychnine Alkaloid- Hazard Evaluati on- Wildlife and Aquatic Organisms. Prepared by Denver Wildlife Research Center. 11 p.



## 81-1 Acute Oral Toxicity in Rats

### 26 MRID Citation Reference

40908901 Cerven, D. (1988) Strychnine Alkaloid Tech nical: Oral Toxicity in Albino Rats: Project ID MB 88-9165 A. Unpublished study prepared by MB Research Laboratories, Inc. 22 p.

41210701 Cerven, D. (1988) Strychnine Alkaloid Technical: Single Dose Oral Toxicity in Rats/LD 50 in Rats: Revised Final Report: Laboratory Project ID 88-9165 A. Unpublished study prepared by MB Re search Laboratories, Inc. 24 p.

43330301 Baroch, J. (1994) Acute Oral Toxicity study with Rats (Rattus norvegicus) Using: Wilco Gopher Getter Type 1 Bait and Wilco Gopher Getter AG Bait: Lab Project Number: 94002. Unpublished study pr epared by Genesis Labs, Inc. 35 p.



## 82-1 Subchronic Or al Toxicity: 90-day Study

MRID Citation Reference

40296502 Record, C. (1987) Tests To Determine the Dietary LC-50 of Strychnine Alkaloid to European Ferrets (Mustela putorius furo ): Lab- oratory I.D. No. 112. Unpublished study prepared by Summit Lab- oratories. 19 p.

40296503 Record, C. (1987) Tests To Determine the Dietary LC-50 of Strychnine Alkaloid to Red Foxes (Vulpes fulva): Laboratory I.D. No. 113. Unpublished study prepared by Summit Laboratories. 19 p.



### Environmental Fate


## 161-1 Hydrolysis

MRID Citation Reference

41122301 Mishalanie, E.; Griffin, D.; Bullard, R. (1989) Environmental Fate Study: Strychnine Alkaloid Hydrolysis: Laboratory Project ID : QA-57. Unpublished study prepared by Denver Wildlife Research Center. 42 p.



## 162-1 Aerobic soil metabolism

MRID Citation Reference

42234201 Starr, R.; Hurlbut, D.; Timm, R. (1992) T he Aerobic Degradation of Strychnine in Soil Under an Optimum Incubation Temperature and Moisture Regimen: Lab Project Number: QA-128. Unpublished study prepared by Denver Wildlife Research Center. 167 p.

### 27 43407601 Starr, R.; Timm, R.; Hurlbut, D.; et al. (1994) The Aerobic Biodegradation of Strychnine in Soil Under an Optimum Incubation Temperature and Moisture Regimen: Supplement: Lab Project Number: QA/346. Un published study prepared by Denver Wildlife Research Center. 192 p.



## 163-1 Leaching/ adsorption/desorption

MRID Citation Reference

42366501 Timm, R.; Starr, R.; Hurlbut, D.; et al . (1992) Mobility of Strychnine in Soil: The Sorption/Desorption of the Parent Compound in Four Soil Systems: Lab Project Number: QA-190. Unpublished study prepared by Denver Wildlife Research Center. 353 p.