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Agricultural Health Study – EPA’s Role and Plans
Current as of March 5, 2009
This Web page describes information that the Agricultural Health Study (AHS) is providing to EPA about the relationships between pesticide exposure and possible health effects on farmers and their families. It also discusses how EPA is using this information to improve its understanding of the potential risks of pesticides and to strengthen our regulatory programs.
On this page:
Management of the Agricultural Health Study
The AHS began in 1993. It is a collaboration of EPA, the National Institute of Environmental Health Sciences (NIEHS), the National Cancer Institute (NCI), and the National Institute for Occupational Safety and Health (NIOSH). EPA’s Office of Pesticide Programs is working closely with these federal partners so that relevant new findings on pesticides are translated into sound regulatory policies and practice.
Designed as a large, long-term, prospective epidemiological study, the AHS collects and analyzes data on the health and work practices of licensed pesticide applicators in Iowa and North Carolina. Individuals enrolled in the study were healthy before enrollment. This study includes:
- 52,000 private applicators
- 32,000 spouses of private applicators
- 5000 commercial applicators
The study focuses particularly on the farmers’ exposure to 50 chemicals, including many of the most widely used pesticides. The study also collects information on other possible agricultural exposures and many lifestyle factors. As data are collected over a period of years for this otherwise healthy population, investigators can study factors such as lifestyle or pesticide exposure associated with cancer and other health outcomes. Since data are observational, it is difficult to establish definitive links between specific chemical exposure and health outcomes.
Scientists can compare overall health outcomes for groups of people who differ in whether they have had exposure to the various chemicals. These comparisons cannot conclusively demonstrate how exposure affects health, but they can show statistical associations. To evaluate whether a cause and effect relationship may exist, EPA will analyze these data further, along with the broader database of information on these pesticides.
More than 100 publications are available on the Agricultural Health Study Web site.
The AHS is looking at both cancer and non-cancer effects. Partners in the study have various lead roles. NCI is responsible for the aspects of the study that evaluate cancer results. NIEHS is managing the studies related to non-cancer effects, e.g., Parkinson’s disease, macular degeneration, and asthma. NIOSH has been conducting pesticide exposure assessment field studies among applicators and farm families.
How EPA Plans to Use AHS Results
The AHS is a potentially valuable source of data to augment the information we currently analyze in our pesticide risk assessments. Because this information is new, we need to carefully evaluate it and determine how it to make the best use of it. Our science-based approach to these data will be rigorous, structured, and transparent.
Epidemiology provides a different insight
EPA has extensive hazard and exposure information to characterize the risks of pesticide products. The hazard and exposure information comes primarily from studies with laboratory animals. In the past, information from well designed epidemiology studies on pesticides, like that of AHS, has not been typically available.
The AHS is generating a wealth of new information. Some of the most important results are the epidemiological data that address the association between pesticide exposure and health outcomes, especially cancer. Epidemiological studies, such as AHS, evaluate whether diseases occur more frequently in groups of people that have higher exposure to a specific chemical, for example a pesticide. Because there can be many potential causes for a disease, statistical associations do not prove that exposure to a chemical is necessarily the cause, but, along with other hazard and exposure information, it can improve the scientific understanding of the safety of the compound.
Published papers from the early years of the AHS have suggested that a higher disease incidence, for example for certain cancers, may be related to specific occupational exposures on the farm, including exposure to some pesticides that are widely used or of special interest to EPA. In some cases, findings are preliminary in that only a small number of participants have developed specific outcomes or the number of years the participants have been followed is too few for results to be certain. In many cases results will be clarified with additional years of follow-up.
EPA is currently awaiting the release of second evaluations of some chemicals from AHS. These second evaluations are designed to replicate the results and are important in confirming the initial observations. Over the next few years, the AHS is also generating biochemical and molecular data to help interpret results from the epidemiological studies.
Developing a science-based process
In anticipation of results from current AHS studies, EPA is developing an approach for incorporating epidemiology information into human health risk assessments for pesticide chemicals. As a basis for this approach, EPA is using existing Agency and international guidance including:
- U.S. EPA 2005 Guidelines for Carcinogen Risk Assessment
- Reference Dose guidance
- IPCF Framework for Analysing the Relevance of a Cancer Mode af Action for Humans and Case-Studies (PDF) (About PDF)
EPA relies on multiple lines of evidence to evaluate the safety of a pesticide, including animal toxicology studies as well as other sources of information such as how effects are caused (mechanisms of action), use patterns, what happens to the pesticide in the environment and how long it remains (environmental fate and persistence), food residue levels, and human exposure potential. Scientists evaluate all available data and weigh the evidence rather than relying on any one study. Incorporating epidemiology data into this process will expand the range of the evaluation.
EPA’s approach to incorporating the AHS findings into existing hazard and exposure information will focus on:
- how the pesticide may cause potential harm (i.e., the pesticide’s mode of action)
- how the body handles the compound once exposed
- what the compound does when it is in the body
An evaluation of exposure pathways, route (e.g., dermal, inhalation, oral), and duration will be an important component of the proposed approach. Another aspect of the approach will be to compare results of the AHS to those obtained from toxicology studies done with rodents and other experimental animals. There are a variety of sophisticated models and tools available, which EPA will use as available and appropriate to evaluate risk.
EPA’s Pesticide Regulatory Program
EPA registers pesticide products sold in the United States. EPA receives its authority to register pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Before registering a new pesticide, EPA must first determine that the pesticide can be used without posing unreasonable risks to human health or the environment. To make such determinations, EPA requires pesticide companies to provide scientific data from more than 100 different scientific studies. Pesticide companies must perform the studies according to rigorous EPA guidelines. EPA then evaluates the data to assess a wide variety of potential human health and environmental effects associated with use of the product. Read more about the registration process.
In addition to registering new products, EPA constantly reexamines regulatory decisions made in the past about pesticides. In recognition that science is continually evolving, EPA’s registration review program collects new scientific information and, as necessary, revisits and revises previous decisions. Read more about the registration process.
Obtaining peer review and involving the public
EPA will present its scientific approach to integrating exposure, toxicology, and epidemiology in a white paper, which will be available along with draft case studies for review by the FIFRA Scientific Advisory Panel in 2009. EPA will also solicit comments from the public on the proposed approach.
Regulatory use of data
EPA intends to use the information from the AHS in its regulatory processes. EPA will, in the course of surveying the overall AHS findings, consider the results of the studies in the course of its regularly scheduled registration reviews and take appropriate regulatory action using its normal public participation process. EPA will evaluate whether there is any need for immediate action or acceleration of planned periodic reevaluations in the registration review program.