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



### PC Code: 059102

DP Code: 426737 April 1 3 , 2015

MEMORANDUM

SUBJECT: Chlorpyrifos

- methyl

- Preliminary Ecological Risk Assessment and Effects Determination in Support of Registrati on Review

TO: Joel Wolf, Chemical Review Manager Kevin Costello, Chief Risk Management and Implementation Branch 2
Pesticide Re

- evaluation Division (7508P)

FROM: Rosanna Louie

- Juzwiak, Risk Assessment Process Leader
Environmental Risk Branch II I Environmental Fate and Effects Division (7507P)

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

REVIEWED BY: James Hetrick, Ph.D., Senior Advisor Melissa Panger, Ph.D., Senior Scientist

E nvironmental Risk Branch III Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed the preliminary ecological risk assessment and federally listed, threatened, and endangered species (also refe rred to as “listed” species) effects determination in support of the Registration Review of the insecticide, chlorpyrifos

methyl (PC Code 059102)

. Chlorpyrifos

- methyl is registered as an insecticide used to target and kill a variety of stored grain insects including beetles, weevils, moths, and grain borers. The registered use s of chlorpyrifos

- methyl are limited to indoor applications made to the interior of empty grain storage bins or warehouses, or, directly to harvested small grains just prior to storage

. V irtually no exposure to non

target organisms is expected to occur when this product is use d as labeled ; therefore, risk is not expected to non

- target organisms, includ ing listed species.

ASSESSMENT

Chlorpyrifos

- methyl is registered in one end

- use prod uct (Storcide II Grain, Bin and Warehouse Insecticide end use product; EPA Reg. No. 264

- 992 ), and the technical product (Reldan F Insecticidal Chemical; EPA Reg. No. 62719

- 42) for treatment of grains in storage bins and warehouses. Chlorpyrifos

-methyl is applied indoors to empty storage grain bins or warehouses with one application per year by sprayer or automatic sprayer at a rate of 0.0253 pound of active ingredient per 1,000 square feet. Chlorpyrifos

- methyl can also be applied indoors directly to small grains prior to storage, to achieve a concentration of up to 3 parts per million. Based on available, but limited recent usage data provided by
the B iological and E conomic A nalysis D ivision, approximately 4,5 00 pounds of chlorpyrifos

- methyl is applied annu ally (EPA, 2015)

.

The labeled indoor uses and application methods of c hlorpyrifos

- methyl significant ly limits any potential
direct or indirect exposure (including drift and runoff) to outdoor terrestrial areas. In addition, the se use pattern s are unlike ly to result in exposure to aquatic resources or groundwater. Because of the indoor use pattern and very low potential for outdoor exposure to non

- target species, only limited data h ave been submitted for this chemical.

Although chlorpyrifos

- methyl is a n organophosphate, the available information indicates that when compared to its closely

- related structural analog chlorpyrifos, chlorpyrifos

- methyl is of lower toxicity to
vertebrates (Beavers, 1978) (Saltatos, et al

. , 1982). With the exception of potenti al toxicity to invertebrates (as expected for an insecticide), chlorpyrifos

- methyl is generally less toxic than other organophosphates ( e.g. , chlorpyrifos).

Other than exposure to the target pest inside of the storage bins, t he only potential exposure to non

target organisms would be treated seeds that were subsequently used for planting , which would occur
several months after the initial treatment . A cursory screen was conducted using the lowest reported avian acute (100 mg/kg/day) (MRID 00027855), acute oral mammalian (5,000 mg/kg body weight) (MRID 48868101), and a chronic mammalian endpoint (body weight gain) from a developmental study (50 mg/kg body weight) (MRID 44680603). This analysis showed that even if terrestrial vertebrates were exposed to seed s treated at the maximum chlorpyrifos

- methyl concentration ( i.e. , 3 ppm)

, potential risk would be low (see Appendix A for the T

- REX analysis )

.

CONCLUSIONS

Based on the use pattern whereby exposure from use of chlorpyrifos

- methyl is expected to be neglig ible, and the low potential for risk if expo sures occur via planted treated seeds , EPA concludes that the currently registered uses of chlorpyrifos

- methyl are not reasonably expected to cause direct or indirect effects to federally listed threatened and en dangered species. A No Effect determination is
made for all listed species, as well as a No Habitat Modification determination for all designated critical habitats for the currently registered use s of chlorpyrifos

- methyl.



### 2ENDOCRINE 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, ne urotoxicity, 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 gro ups. As part of its reregistration decision for chlorpyrifos

- methyl

, 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), chlorpyrifos

- methyl 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 c onsists 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

- rel ated 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 t est 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, 2013 1 and includes some pesticides sch eduled 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 chemic als, future lists, the test guidelines and the Tier 1 screening battery, please visit our website. 2

1 See http://www.regulations.gov/#!documentD etail;D=EPA

- HQ

- OPPT

- 2009

- 0477

- 0074 for the final second list of

chemicals.

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



### 3References :

Beavers, J.B.; Fink, R.; Brown, R. (1978) Final Report: Eight

- Day Dietary LC 50 -- Bobwhite Quail: Project No.

103

- 186. U.S. EPA MRID 00039223.

Bryson, A.M. 1992. A Study of the Effect of Technical Reldan on the Pregnancy of the Rat. Huntingdon Research Centre Ltd. Laboratory Study ID: GHE

- 413. MRID 44680603.

U.S. EPA, 2015. Email communication from D. Atwood, Biological and Economic Analysis Di vision. March 26, 2015.

Cunningham and Schafer, 1968. Starling and Redwinged Blackbird. 1968. EPA Ascension No. 242149, Report #3a. U.S. EPA MRID 00028755

.

Saltatos, et al. 1982. Factors Involved in the Differential Acute Toxicity of the Insecticides Chl orpyrifos and Methyl Chlorpyrifos in Mice. Toxicology and Applied Pharmacology, 65, pp. 144

– 152.

Verma, et al. 2012. Acute Oral Toxicity Study of Chlorpyrifos Methyl TGAI in Rats. HAI Research

Foun d ation. Laboratory Project Study Number 401

- 1

- 01

- 4229. M RID 48868101.



### 4

### Appendix A. TREX Modeling for Exposure to Eating Treated Seed

A cursory analysis was conducted using the lowest reported avian acute (100 mg/kg/day) (MRID 00027855), acute oral mammalian (5,000 mg/kg body weight) (MRID 48868101), and a chro nic mammalian endpoint (body weight gain) from a developmental study (50 mg/kg body weight) (MRID 44680603).

The application rate for the end use product (EPA Reg. No. 264

- 992) for wheat is 12.4 fluid ounces of product per 1,000 bushels, to achieve a 3 p pm concentration on seed.

Chemical Name: chlorpyrifos methyl

Seed Treatment? (Check if yes) Yes, Seeding rate of 156.0 lb/acre

% A.I. (leading zero must be entered for formulations <1% a.i.): 21.60%

Application rate (fl oz/cwt) 0.02

Half

- life (days): 3 5

Application Interval (days): 0

Number of Applications: 1 Are you assessing applications with variable
rates or intervals? no

Reported Endpoints Tested Body Adjusted LD 50 Size class for adjusted LD 50 Weight (g)

Avian LD 50 : 100.00 29 94.58 Sma ll (20g) Avian repro.

NOAEC: 0.00 120.40 Medium (100g)

170.07 Large (1000g)

Mammalian

LD 50 : 2000.00 350 4395.66 Small (15g)

Mammalian

NOAEL: 6.60 3556.56 Medium (35g)

1538.32 Large (1000g)
Adjusted NOAEL for Mammals
Small ( 15g) 109.89 Medium (35g) 88.91
Large (1000g) 38.46



### 5Animal Size Crop Maximum Application

Rate Maximum
Seed Application

Rate Avian Nagy

Dose Mammalian Nagy Dose Available AI

(lb a

. i

. /A) (mg a

. i

. /kg seed) (mg a

. i

. /kg

bw/day) (mg a

. i

. /kg

bw/day) (mg ai

. ft

- 2)

Small wheat, all

or unspecified < 0.0 1 2.81 0.71 0.60

0.00 Medium 0.41 0.41

Large 0.18 0.10

Crop Risk Quotients†
Avian (20 g) Mammalian (15 g)
Acute (# 1) Acute (# 2) Chronic Acute (# 1) Ac ute (# 2) Chronic

wheat, all or unspecified 0.01 <0.01 N/A <0.01 <0.01 0. 01

Avian (100 g) Mammalian (35 g)
Acute (# 1) Acute (# 2) Chronic Acute (# 1) Acute (# 2) Chronic

wheat, all or unspecified < 0

. 0 1 <0.01 N/A <0.01 <0.01 <0.01

Avian (1000 g) Mammalian (1000 g)
Acute (# 1) Acute (# 2) Chronic Acute (# 1) Acute (# 2) Chronic
wheat, all or unspecified <0.01 <0.01 N/A <0.01 <0.01 <0.01

† Acute RQ #1 = (mg a.i. /kg

- bw/day) / LD 50 N/A = not assessed

Acute RQ #2 = mg a

. i

. ft

- 2 /(LD 50 *bw)

Avian Chronic RQ = m g kg

- 1 seed / NOAEL

Mammalian Chronic RQ = mg a.i./kg

- bw/day / adjusted NOAEL



### 6