Aggregate Risk Assessment of Chlorimuron ethyl

Chlorimuron ethyl is a sulfonylurea class herbicide that inhibits acetolactate synthase, which regulates plant growth. It is registered for use on soybeans and peanuts. Chlorimuron ethyl may be applied to soybean crops at preplant,preemergence, postemergence, or postharvest stages by band treatment, broadcast, ground spray, low volume spray, or soil incorporated treatment at the current maximum application rate of 0.08025 lbs active ingredient per acre per crop cycl. Chlorimuron ethy lmay be applied to peanut crops at the foliar stage by band treatment, broadcast, or low volume spray at the current maximum application rate of 0.0078125 lbs active ingredient per acre per crop cycl.

The preharvest intervals are 60 days for soybeans and 45 days for peanuts. Chlorimuron ethyl(CAS NO: 90982-32-4) may also be applied to non-crop land at the foliar stage by broadcast at the current maximum application rate of .03125 lbs active ingredient per acre. There are no residential uses for chlorimuron ethyl. Fifteen end-use products in water dispersible granular formulations have been identified, and one pending registration exists for a granular formulation. The percentage of active ingredient in these products ranges from 8.3 to 31.8%. A dditionally, there is a technical and an intermediate product with 97.8% and 54% active ingredient, respectively.

The uncertainty factors applied in the chlorimuron ethyl risk assessment consist of a standard uncertainty factor of 100X and an FQPA Safety Factor of 1x. The uncertainty factor of 100X includes both a 10X uncertainty factor for intraspecies variability i.e. differences among human and a 10X uncertainty factor for interspecies variability i.e. differences between humans and anim. The FQPA Safety Factor is a method of accounting for any increased susceptibility of infants and children to toxic effects. The A gency concluded that, because there are low concerns, no residual uncertainties with regard to pre- and/or postnatal toxicity, and high confidence that exposure estimates have not been underestimated, the factor could be reduced to 1x from the standard 10x.

Chlorimuron ethyl is classified as Toxicity Category III for acute dermal and Toxicity Category IV for acute oral toxicity and inhalation. It is a mild eye and skin irritant and does not cause skin sensitization. There is no evidence of potential neurotoxicity, mutagenicity, or carcinogenicity for chlorimuron ethyl provided in the available studies.

EPA is required under the FFDCA , as amended by FQPA , to develop a screening program to determine whether certain substances including all pesticide active and other ingredi "may have an effect in humans that is similar to an effect produced by a naturally occurring estrogen, or other such endocrine effects as the A dministrator may designate." Following the recommendations of its Endocrine Disruptor Screening and Testing A dvisory Committee EDSTA C, EPA determined that there was a scientific basis for including, as part of the program, the androgen and thyroid hormone systems, in addition to the estrogen hormone system.

EPA also adopted EDSTA Cs recommendation that the Program include evaluations of potential effects in wildlife. For pesticide chemicals, EPA will use FIFRA and, to the extent that effects in wildlife may help determine whether a substance may have an effect in humans, FFDCA authority to require the wildlife evaluations. A s the science develops andresources allow, screening of additional hormone systems may be added to the Endocrine Disruptor Screening Program EDSP.

Based on currently available data, chlorimuron ethyl does not appear to be an endocrine disruptor. However, when the appropriate screening and/or testing protocols being considered under the A gencys EDSP have been developed, chlorimuron ethyl may be subjected to additional screening and/or testing to better characterize effects related to endocrine disruption.

There are no studies identifying an acute dietary endpoint based on toxic effects observed following a single dose, therefore no acute dietary risk assessment was performed. For chronic dietary exposure, a no observed adverse effect level NOA EL of 9 mg/kg/day was identified from a chronic dog study in which mild anemia was observed at the lowest observed adverse effect level LOA EL of 51 mg/kg/day. Because chlorimuron ethyl has no residential uses, only dietary exposure was assessed.

For chlorimuron ethyl, the aggregate chronic dietary risk estimates including food and drinking wat for the general U.S. and all population subgroups are less than 1% of the cPA D and are below the A gencys level of concern.

Chronic aggregate dietary exposure to chlorimuron ethyl was calculated using a Tier 1 approach which assumes that 100% of each crop is treated with chlorimuron ethyl, that pesticide residues exist on food at the legal tolerance levels, and that levels in drinking water are at upper-bound estimates.

The Dietary Exposure Evaluation Model software was employed for the risk assessment with the Food Commodity Intake Database DEEM-FCIDtm, Version 1.3 which incorporates food consumption data from USDA s Continuing Surveys of Food Intakes by Individuals CSFII from 1994-1996 and 1998. Chronic aggregate risk was assessed by comparing chronic dietary exposure estimates to the chronic Population A djusted Dose cPA D, with risk expressed as a percent of the cPA D. Exposure estimates that are less than 100% of the cPA D indicate a determination of safety can be concluded. The degradates of chlorimuron ethyl are not expected to be more toxic nor exceed levels of the parent compound.