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TRAC 5/28-29/98

Staff Paper # 4.2


TOPIC: EXPOSURE DATA FOR RESIDENTIAL RISK ASSESSMENTS

BACKGROUND:

In reassessing tolerances the Food Quality Protection Act (FQPA) requires that EPA consider aggregate pesticide exposure from all sources including food in the diet, drinking water, and residential use. The need to aggregate exposures has placed increased emphasis on developing methods to refine exposure estimates. Before the FQPA, EPA had begun to use Monte Carlo probabilistic exposure models to refine acute dietary risk estimates by considering the full range (distribution) of residues on food and consumption patterns. Since the enactment of FQPA, the Agency has increased its efforts to incorporate probabilistic methods in drinking water and residential assessments, but is not able to conduct probabilistic assessments for either drinking water or residential exposure at this time.

The most common residential uses include outdoor lawn and garden applications, indoor treatments for cockroaches and other pests, and applications to domestic animals to control fleas and ticks. Residents can be exposed while mixing and applying pesticides, by breathing the air in areas that have been recently treated, and by touching animals and surfaces that have been treated.

The amount of pesticides used in and around the home is relatively small compared to agricultural uses; however, approximately 10% of organophosphate use is in the residential environment, including application by residents, professional applicators, and mosquito control districts. The safety of pesticides used in and around the home is of increasing public concern. Poison control centers in the U.S. receive many calls from residents about the use of pesticides (about 90,000 calls per year, 25% of which relate to residents having symptoms related to pesticide use.)

Exposure Data Currently Used

Currently, in conducting residential exposure assessments for all chemicals, the Agency uses the best available information including:

The Agency intends to present a range of exposure estimates in order to provide a more complete understanding of exposure and risk.

Exposure Data Under Development

EPA is expecting new data from a variety of sources, including industry task forces, academia, and EPA's Office of Research and Development; however, much of these data are not currently available. Research and data development efforts for the future include:

Data derived from these research efforts will enable EPA to perform probabilistic exposure assessments and refine modeling approaches. The time frame for completion, validation and inclusion of these new data is approximately 1-3 years.

Science Peer Review

EPA's SOPs for Residential Exposure Assessment were presented to the FIFRA Scientific Advisory Panel (SAP) in 1997 and were published the same year. In addition, the components of the SOPs have undergone various levels of peer review both inside and outside the Agency. EPA's draft Post Application Exposure Monitoring Test Guidelines and draft Guidance for the Submission of Probabilistic Exposure Assessments were presented to the SAP in March, 1998.

ISSUES THAT TRAC MIGHT ADDRESS:

1) How should EPA take residential exposures into account in making tolerance reassessment decisions during the "interim" period while additional data are under development?

Discussion

EPA is working closely with researchers and industry task forces to design and develop protocols for collecting additional residential exposure data that will decrease the uncertainty associated with current estimates. These data will not be available for use in risk assessments for several years. A critical concern for EPA is how to proceed with tolerance decisions that are protective of the public health while additional data are being developed. Some possible options include:

2) How should EPA combine residential exposure estimates with dietary exposure estimates given differences in the level of uncertainty, and frequency of exposures?

Discussion

Currently, if a pesticide is used in the home as well as on food crops, EPA adds residential exposure estimates to a "background" level of dietary exposure. In some cases, dietary estimates have been refined by various factors including the percent of the food crop actually treated with pesticide, and reduction factors for cooking, processing, etc., whereas no data are available to define the range of exposure values for the residential component of exposure.


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updated April 1, 1998