Pesticide volatilization can be defined as the movement of pesticide vapors through the air. People such as farm workers and bystanders can be exposed to pesticides by breathing these vapors after an application has occurred. Volatilization is considered differently than pesticide movement by spray drift, erosion, or windblown dust/soil particles. Exposure to pesticide vapors due to post-application volatilization is generally from three main sources. These include application of:

• Volatile agricultural pesticides (e.g., fumigants).
• Semi-volatile agricultural pesticides.
• Pesticides for indoor pest control.

Evaluating Pesticide Volatilization

Over many years, EPA has been actively engaged in evaluating possible exposures associated with pesticide volatilization. This includes developing consistent methods for assessing volatilization from fumigants as well as volatilization from indoor uses of pesticides.

More recently, EPA has been adapting the approaches developed for conducting risk assessments for the fumigants for use in assessing potential bystander inhalation risk resulting from the volatilization of other conventional pesticides (i.e., semi-volatile pesticides).We assess inhalation exposure for volatile pesticides as part of our human health risk assessments during pesticide registration and registration review.

As part of this process, we have evaluated a number of factors that appear to affect volatilization to some degree including the following:

• Physical and chemical pesticide properties, including vapor pressure which appears to have a major effect on volatilization.
• Soil properties.
• Persistence of a pesticide on plant surfaces.
• Meteorological conditions.
• Agricultural practices.

Improving Evaluation of Semi-Volatile Pesticides

EPA has worked with states and other federal agencies and sought input from stakeholders to determine the most appropriate way to evaluate exposures to semi-volatile pesticides. In December 2009, we sought expert advice and input on issues related to volatilization of pesticides from the Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel (SAP).  The panel submitted its final report on March 2, 2010.

In response to the report, we released for public comment a draft volatilization screening tool in March 2014. This tool, its development and examples of its use are described in Human Health Bystander Screening Level Analysis: Volatilization of Conventional Pesticides. During Registration Review, we will use this analysis to determine if data (i.e., flux studies, route-specific inhalation toxicological studies) or further analysis is required for specific pesticides.

For More Information

FIFRA SAP meeting on volatilization:

• December 1-4, 2009: Scientific Issues Associated with Field Volatilization of Conventional Pesticides .
• Materials related to the December 1-4, 2009 FIFRA SAP meeting: Docket EPA-HQ-OPP-2009-0687 at regulations.gov.

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

• How EPA assesses health risks from pesticides
• Reevaluation of pesticides