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Pesticide issues in the works: pesticide volatilization

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Current as of April 2014

EPA considers all pathways of exposure to ensure that all exposures are below levels of concern. Pesticides can move from the sites where they are applied into the surrounding environment through a number of different ways, including drift and volatilization.

Pesticide drift can occur when pesticides move off the application site in the air as particles or aerosols during application or when the pesticides move that are attached to dust.

Volatilization occurs when pesticide surface residues change from a solid or liquid to a gas or vapor after an application of a pesticide has occurred. Once airborne, volatile pesticides can move long distances off site. Fumigant pesticides (used to treat soil before planting and to treat structures such as homes or storage bins) are especially volatile. But, not all pesticides are volatile.

Past practices for evaluating volatile pesticides

Historically, EPA has assessed inhalation exposures through volatilization for pesticides that have high vapor pressures (a characteristic that allows them to move easily into a gaseous state). Certain indoor-use pesticides and fumigants meet this high vapor pressure criterion. EPA has assessed exposures and risks related to volatilization for these pesticides in its re-evaluation program for pesticides on the market, as well as, during its registration program before allowing use. As a result, measures have been taken or are proposed to reduce exposures and risks below levels of concern.

New data lead to possible new evaluation methods

In addition to this re-evaluation work, EPA has reviewed data on volatilization that have become available from the Pesticide Action Network of North America Exit EPA disclaimer as well as many studies from the California Air Resources Board Exit EPA disclaimer . EPA has been joined in this effort by the States of California, Florida, Minnesota, and Washington and by Canada. These data show that detectable exposures occur for semi-volatile pesticides. However, the data available to date show that the exposures are low and generally below levels of concern.

What EPA is doing

As a result of this analysis, EPA is in the process of reconsidering the criteria it uses to trigger an assessment of exposure from inhalation of pesticides that volatilize. Vapor pressure appears to have a major effect on pesticide volatilization. Other physical and chemical pesticide properties, agricultural practices, meteorological conditions, persistence of a pesticide on plant surfaces, and soil properties also appear to affect volatilization to some degree. This work will help the Agency to predict which pesticides have the potential to volatilize and under what conditions.

EPA also continues to work to determine the best way to estimate the levels of exposure resulting from volatilization, including the use of monitoring data from PANNA and CARB, single field modeling, and air-shed modeling. The Agency continues to work with states and other federal agencies, as well as seeking input from stakeholders to determine the most appropriate way to evaluate the significance of these exposures.

Due to the many science issues related to pesticide volatilization, including estimating the magnitude of exposures and determining the best method for assessing potential risks, the Agency sought the expert advice and input from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel in December 2009. Further information is available on the FIFRA SAP Meetings web page and in docket EPA-HQ-OPP-2009-0687 at regulations.gov.

For more information

If you are intested in more detail on how EPA evaluates pesticides to protect your health and environment, see:

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