Summary of the Preliminary Cumulative Risk Assessment for the Organophosphorus Pesticides December 3, 2001
Note: This information is provided for reference purposes only. Although the information provided here was accurate and current when first created, it is now outdated.
Status and Results of the Risk Assessment
- EPA has completed and released the preliminary cumulative risk assessment for the organophophorous pesticides.
- This assessment represents a new way of analyzing data about potential exposure to pesticides.
- The Agencyþs methods result in measurements of the probability of exposure to more than one organophophorous pesticide and an assessment of such combined exposure.
- The methods used to generate the results have received numerous scientific reviews by the FIFRA Scientific Advisory Panel before completion of this preliminary cumulative risk assessment.
- The risk mitigation measures that have already been taken on individual members of this group of pesticides have led to significant reduction in potential risk, and EPA is continuing to address risks as they are identified for individual organophosphorus pesticides.
- EPA remains confident in the continued safety of our food supply and continues to emphasize the importance of eating a varied diet rich in fruits and vegetables.
- Pesticide residues in drinking water do not appear to be a significant contributor to risk.
- Although most indoor uses of organophophorous pesticides have been eliminated through earlier risk reduction actions, a few remaining uses may be re-evaluated.
- The Food Quality Protection Act (FQPA) directs EPA to consider the combined effects to human health that can result from exposure to two or more chemicals that act the same way in the body.
- EPA has designed and conducted a sophisticated and complex preliminary cumulative risk assessment for the organophosphorus pesticides.
- This assessment is based on evaluation of the potential for people to be exposed to more than one member of this group of pesticides at a time and considers exposures from food, drinking water, and residential sources.
- The food assessment is national in scope because food consumption generally does not vary across the U.S. or during the year.
- The assessment incorporates regional exposures from residential and drinking water sources, as the most appropriate way to account for the considerable variation in potential exposures across the country.
Developing the Methods
- Shortly after enactment of FQPA, EPA began developing new methods and tools that would allow the consideration of combined risks from exposures to several pesticides via several pathways and routes of exposure.
- This process included consulting with a wide variety of scientific experts on possible approaches, working with stakeholders to develop improved sources of data, developing and implementing ways to increase the transparency of EPAþs deliberations and decision-making processes, all the while proceeding with risk assessments and risk reduction for individual organophosphorus pesticides.
- For example:
- EPA has presented aspects of the methods for this assessment to the FIFRA Scientific Advisory Panel for independent scientific peer review at more than 30 meetings
- There have been nine science policy papers related to the cumulative assessment process released for public comment
- EPA has held technical briefings on the cumulative assessment guidance and the methods for various portions of the cumulative assessment process
Pesticides and Uses Included in the Assessment
- The preliminary cumulative assessment of potential exposure includes the following pesticides. The letters following the names indicate in which assessment(s) they appear, food (F), water (W), residential (R):
- The OPs that are not included in the food assessment meet one of
- They have been voluntarily canceled
- They have only residential or public health uses
- They have no detectable residues in food
Sources of Data
- EPA considered data about potential sources of exposure from food, drinking water, and residential uses (for example, in-home, lawn and garden, public-health-related uses, and golf courses).
- This preliminary risk assessment is rich in data; EPA has gone to great lengths to obtain appropriate data to use in conducting this risk assessment.
- Each component of the risk assessment uses the best-available data; data mainly come from surveys of what people eat, their activities such as use of pesticides around the home, and monitoring studies of pesticide residues.
- For the food assessment, data sources include:
- U.S. Department of Agricultureþs (USDA) Pesticide Data Program
- USDAþs Continuing Survey of Food Intake by Individuals
- The Food and Drug Administration (FDA)Total Diet Study
- FDA monitoring data
- Data sources for the water component of the assessment included:
- USDA Agricultural Chemical Usage Reports for Field Crops, Fruits, and Vegetables
- USDA Typical Planting and Harvesting Dates for Field Crops and Fresh Market and Processing Vegetables
- Local sources for refinements
- Monitoring studies from U.S. Geological Survey and other sources
- For the residential assessment, data sources include:
- Information from surveys and task forces, e.g., National Home and Garden Pesticide Use Survey
- Special studies and reports from the published scientific literature, e.g., Non-Scripted Activities of Children Measured Using Fluorescent Tracers (Black, 1993)
- EPAþs Exposure Factors Handbook
- Other sources, e.g., State Cooperative Extension Service
Analyzing the Data
- In assessing hazard associated with the organophosphorus pesticides, EPA analyzed the common mechanism of toxicityÍinhibition of cholinesterase.
- The Agency chose an index chemicalÍ methamidophosÍto use for comparison of degree of cholinesterase inhibition among these pesticides.
- EPAþs assessment constructs realistic scenarios using all the available data; these scenarios are the basis for analysis of the probability of exposure.
- To perform the risk assessment, EPA used a calendar-based program called Calendex to calculate probabilities of exposure from food, water, and residential use.
- In developing the water assessment, EPA also used a computer modeling program called PRZM-EXAMS/IR, supplemented by water monitoring data. (The Pesticide Root Zone Model (PRZM) calculates what happens to a pesticide in a farmer's field on a day-to-day basis. It considers factors such as rainfall and how and when the pesticide is applied. EXAMS II assesses the fate, exposure, and persistence of pesticides in aquatic ecosystems. The Index Reservoir (IR) is representative of a number of reservoirs in the central Midwest. These models provide a basis for assessing potential of pesticides to contamintate water.)
- In assessing the potential exposure from food, EPA determined that the data supported looking at the exposure nationally, since food generally is distributed nationally.
- In assessing potential exposure to pesticides in drinking water and from residential uses, the Agency used a geographic approach. People generally obtain drinking water from local sources, and there are different pest issues in different regions, so the use of pesticides varies in different parts of the country, as well as seasonally, requiring a more localized approach.
- EPA plans to continue its work on the cumulative assessment after December 3rd, including conducting additional analyses that would be available for the technical briefing or February 2002 SAP meeting.
- Continuing in the effort to ensure transparency of its decision processes,
EPA is implementing several steps over the next few months following
the December 3, 2001 release of the preliminary cumulative risk assessment
for the organophosphorus pesticides:
- EPA will open a public comment period, which will close on or about March 8, 2002 (EPA will publish a Federal Register notice that will include information on submitting comments).
- On January 15, 2002, EPA will hold a technical briefing on the preliminary assessment.
- On February 5-8, 2002, EPA will present the preliminary cumulative risk assessment to the FIFRA Scientific Advisory Panel for peer review and comment.
- Following the comment period, EPA will consider the comments and plans to issue a revised risk assessment in summer 2002.
- The cumulative risk assessment along with individual risk assessments, will be the basis for completing tolerance reassessment for the organophophorus pesticides.