Agricultural Health Study
Closed for Recruitment
Study / Trial Background
Agricultural Health Study
The Agricultural Health Study (AHS) is a prospective study of cancer and other health outcomes in a cohort of licensed pesticide applicators and their spouses from Iowa and North Carolina. The AHS began in 1993 with the goal of answering important questions about how agricultural, lifestyle and genetic factors affect the health of farming populations. The study is a collaborative effort involving investigators from National Cancer Institute, the National Institute of Environmental Health Sciences, the Environmental Protection Agency, and the National Institute for Occupational Safety and Health.
More than 89,000 farmers and their spouses in Iowa and North Carolina have participated in the study. Their participation has provided, and continues to provide, the data that researchers need to help the current and future generations of farmers and their families live healthier lives.
The "Agricultural Health Study" (AHS) is a collaborative effort between the National Cancer Institute and the National Institute of Environmental Health Sciences. The U.S. Environmental Protection Agency and the National Institute for Occupational Safety and Health are providing support for a limited exposure assessment effort.
Initial data collection on a prospective cohort of 89,658 study subjects has been completed as of December 1997. Participants completed questionnaires that included items on pesticides used, other agricultural exposures, and work practices that modify exposure as well as on other activities that may affect either exposure or disease risks (e.g., diet, exercise, alcohol consumption, medical conditions, family history of cancer, other occupations and smoking history). Phase II of the study (1998-2003) updated information on occupational exposures, diet, work practices and medical history by means of a computer assisted telephone interview. We also collected buccal cells on sample of 34,000 study participants to assess the effect of inheritable polymorphisms and the interaction of environment and genomic predisposition.
The stimulus for this prospective investigation comes from the growing evidence that, despite a low mortality overall, farmers experience an excess of several cancers. These excesses have been observed in retrospective epidemiological studies among agricultural workers in several countries. Excess cancers are observed for the lymphatic and hematopoietic system, connective tissue, skin, brain, prostate, stomach and lips. Several of these tumors (brain, NHL, multiple myeloma, and prostate) are also increasing in the general population in many of these countries. This suggests a common set of exposures may explain the high rates in farmers and rising rates in the general population.
Farmers, their families, and other pest control workers may have contact with a variety of potentially hazardous substances including pesticides, solvents, fuels and oils, engine exhaust, dust and zoonotic viruses and other microbes. Our cohort study includes all registered pesticide applicators in Iowa and North Carolina and the spouse of applicators who are farmers. The health effects of pesticide use are the primary focus of the study. The influence of other farm exposures are also being evaluated.
The focus of the phase II follow-up period (2004-2008) is to update exposure information and health histories by means of a computer assisted interview and also following the cohort to determine disease incidence and mortality. The cohort is being followed through the cancer registries within Iowa and North Carolina, the Social Security Administration database, state vital statistics offices, National Death Index, and various in-state databases, such as the listing of registered pesticide applicators. Individuals who enrolled into the study but who are no longer at the address given during enrollment (based on subsequent attempts at follow up) have been submitted and will continue to be submitted (through NIOSH) in the standard format to the IRS under their Project 057 Taxpayer Address Request Program. Identifying data provided to the IRS include only SSN and the first four letters of last name of cohort member. IRS provides in return the most current address in IRS records if a match (SSN + all four letter of last name) is found. The purpose of this effort is to identify members of the cohort who have moved out of state, to enable adjustment of person-years for incidence and mortality calculations. Persons who have moved out of state can be followed for vital status and cause of death, but not for cancer incidence.
Continuation of the protocol will provide a valuable epidemiologic resource to help prevent cancers in the future by identifying risk factors in the rural/agricultural environment. Because more cases of important cancer outcomes occur in this cohort every year, potential cancer causes can be evaluated with increased statistical power. Larger number of cases also allows for statistical control of confounding factors, making more meaningful conclusions about cancer risk, and, for some relatively infrequent cancers, such as the lyphomas and leukemias, greater follow-up time is necessary to make any meaningful observations.
For more information on this study, please visit the Clinical Trials page for this study.
The study has completed enrollment.
- Genders Eligible for Study: Both
- Accepts Healthy Volunteers: No
- All registered pesticide applicators in Iowa and North Carolina and the spouse and children of applicators who are farmers.
Between 1993 and 1997, 52,394 licensed private pesticide applicators (mostly farmers) from Iowa and North Carolina enrolled, as did 32,345 of their spouses. The study also included 4,916 commercial pesticide applicators in Iowa in its first two phases. The average ages at enrollment were 47.1 years, 38.0 years, and 46.9 years for private applicators, commercial applicators and spouses.
What is NIEHS doing?
The study began by collecting baseline information from participants when they enrolled (1993-1997). Follow-up telephone interviews were conducted in the second (1999-2003) and third phases (2005-2010) of the study. The Phase 2 interview was completed by 64% of private applicators, 59% of commercial applicators, and 74% of spouses. Participants provided updated information on farming practices, lifestyle, and health and were asked to complete a dietary questionnaire and provide a sample of cheek cells as a source of DNA. The Phase 3 interview also updated information on farming practices, lifestyle, and health. It was completed by 46% of enrolled private applicators and 62% of enrolled spouses. A new follow-up effort began in 2013 and is expected to be completed in 2014. All participants who were eligible to participate at Phase 3 are being asked to complete a questionnaire by mail, telephone or through the Internet regardless of whether they participated at Phase 3. As needed, interviews will be completed with next-of-kin.
The cohort is also followed for mortality and cancer incidence through periodic linkage with vital statistics and state cancer registries.
Study / Trial Location
United States, Iowa
University of Iowa
Iowa City, Iowa, United States, 52242
United States, North Carolina
Research Triangle Institute
Research Triangle Park, North Carolina, United States, 27709
Protocol Number: OH93-NC-N013
Enrollment and Contact Information
To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.
Please refer to this study by its ClinicalTrials.gov identifier: NCT00352924
For general inquires about the AHS you can visit their website or contact them at
Agricultural Health Study
For questions about the ongoing AHS Study Follow-up:
Elizabeth O’Connell, RN, BSN, Study Manager