OFFICE OF PESTICIDES PROGRAMS UNITED ST AT ES ENVIRONMENT AL PROTECTION A GENCY

WA SHINGTON D.C., 20460 Chemical: Chlorpy rifos - methyl PC Code: 059102 DP Barcode: 370120 DATE: November 23 , 2009 MEMORANDUM SUBJECT: Registration Review

– Problem Formulation for Chlorpy rif os - methyl FROM: Donna Judkins, Biologist

M ark Corbin, Senior Environmental Scientist THROUGH: Dana Spatz, Branch Chief

Environmental Risk Branch 3 Environmental Fate and Effects Division Office of Pesticide Programs TO: Veronique LaCapra, Chemical Review Manager

R eregistration Branch 2 Pesticide Re - Evaluation Division Office of Pesticide Programs Attached is the preliminary problem formulation, a part of the registration review, f or the insecticide C hlorpy

rifos - meth yl .2 

### REGISTRATION REVIEW PROBLEM FORMULATION FOR: 

## CHLORPYRIFOS - METHYL

Chlorpy rifos - methyl (CAS 5598 - 13 - 0)

PREPARED BY: Donna Judkins, Ph.D., Biologist Mark Corbin, Senior Environmental Scientist APPROVED BY: Dana Spatz , Branch Chief Environmental Risk Branch 3 Environmental Fate and Effects Division Office of Pesticide Programs3 STRESSOR SOURCE AND DISTRIBUTION Chlorpy rifos - methyl is an insecticide used to target and kill a variet y of insects including beetles, weevil s, moths, and grain borers. Chlorpy rifos - methyl has two current registrations (EPA Reg # 264 - 992 and 62719 - 42) for treatment of grains in storage bins and warehouses. Chlorpy rifos methyl is applied indoors with one application per y ear by spray er or auto matic spray er at a rate of 0.0253 lbs ai/1,000 square feet. Based on the most recent usage data provided by BEAD chlorpy rifos - methyl has been applied predominantly on stored grains with approximately 110,000 lbs applied annually . Table 1. Chemical Reg istration Data Summary Common name Chlorpy rifos - methyl Chemical name Chlorpy rifos - methyl [ C 7 H 7 Cl 3 NO 3 PS] CAS number 5598 - 13 - 0 Pesticide ty

pe Insecticide PC Code 059120 EPA Registration Numbers 264 - 992 (Bay er Crop Science STORCIDE II (21.6% active)) & 62719 - 42 (Dow AgroSciences Reldan* F Insecticidal Chemical (97% active)) INTEGRATION OF AVAILABLE INFORMATION The documents available in the Office of Pesticide Programs Regulatory Docket and which serve as the basis for this problem formulation incl ude the following:

 1980 Ecological Risk Assessment  December 2000 Tolerance Reassessment  October 2000 Pesticide Fact Sheet  December 2007 Product Cancellation Order ECOLOGICAL EFFECTS No ecotoxicological data have been required b y EPA in past assessments of chlorp yrifos - methyl since all uses were indoor. However, according to product labels, all end - use products are toxic to extremely

toxic to fish, birds and other wildlife; therefore, it is not allowed to be used on or near water or on seed to be fed to birds or wildlife. Data from earlier risk assessments indicate that chlorpy

rifos - methyl is practicall y nontoxic to moderatel y toxic to avian wildlife based on dosing studies (LD 50 , 100 - >2000 mg/Kg); practically nontoxic to slightly

toxic to avian wildlif

e based on dietary

studies (LC 50 , 1835 - >5000 mg/L); moderatel y toxic to very highl y toxic to fish based on acute data (L C 50 , 0.014 - 4.58 mg/L); and slightly toxic to very

highly toxic to aquatic invertebrates based on acute tests (L C 50 , 0.00017 - 45.8 mg/L); and very highly toxic to honey

bees based on acute studies (LD 50 , 0.088 - 0.383 μ g/bee).4 EXPOSURE CHARACTERISTICS No acceptable environmental fate data have been submitted to EPA for chlorpy rifos - methyl. The environmental fate and metabolism of chlorpy r ifos - methyl are expected to be similar to the environmental fate and metabolism for chlorp yri fos. Previously , data summaries were prepared by EFED that present overviews of the environmental fate as captured in open literature. These data suggest that ch lorp yrifos - methyl is relativel y non - persistent under biotic (aerobic soil metabolism and field dissipation studies) and abiotic conditions (hy drol ys is) based on both laboratory

and field data with half lives generally less than 30 day s. An exception to th is is that hy drol ys is half lives are longer (i.e., up to 76 day s) at colder temperatures (i.e., 15 degrees Celsius) and is more stable under acidic conditions . Finally , chlorpy rifos - methyl is relativel y immobile with K oc ’s between 3,000 and 4,500. Chl orpy rifos - methyl does not appear in any of the surface or groundwater monitoring data sets reviewed, however, this could be due to the fact that most monitoring programs are not anal yz ing for it. Table 2 . Phy sical and Chemical Properties of Chlorpy rifo s - methyl Empirical formula C 7 H 7 Cl 3 NO 3 PS Molecular mass (g/mol) 322.6 Vapor pressure 4.22 x 10 - 5 mm Hg at 25 o C Solubility in water 4 mg/L K ow 4.3 pK a NA Hydrolysis half

- life 3 days to 7 6 days

ANALYSIS PLAN Chlorpy rifos - methyl is used as an in door treatment for small grains in storage bins and warehouses. The product is applied by manual and automatic spray er in self - contained units applied in discrete locations with a spatial extent limited to building size areas with negligible potential for offsite transport. The application method does not allow for drift to terrestrial areas or to water bodies. The units are not intended for moist areas and do not contain amounts of active ingredient sufficient for runoff to be a concern. D irect or indi rect exposure to humans or ecological receptors is not expected. If used as directed on the product label, then the likelihood of exposure to non - target wildlife is minimal. Therefore, ecological exposure and effects are not expected from this use. In ad dition, the use pattern is unlikely to result in exposure in aquatic resources or groundwater and thus drinking water is unlikely to be impacted by

this use. According to 40 CFR Part 158, avian oral toxicity , freshwater fish acute toxicity and freshwater invertebrate acute toxicity data are conditionally required for the indoor use pattern, depending on whether or not there is a potential for environmental exposure. Since the use of the currently registered products containing chlorp yrifos - methyl is not e xpected to result in environmental exposure, no additional ecological effects data are required.5

The Agency

anticipates that no quantitative ecological risk assessment or drinking water assessment will be needed. Because these uses are indoors, it is unli kely that listed species will be impacted and thus a quantitative endangered species assessment will not be conducted .