In 1993, scientists from the National Cancer Institute, the National Institute of Environmental Health Sciences, and the U.S. Environmental Protection Agency began a study known as the Agricultural Health Study (AHS). Its goal is to follow a large population of men and women over time to evaluate the role of agricultural exposures in the development of cancer and other diseases in the farming community. (Agricultural Health Study homepage: http://www.aghealth.org)

The study also will provide an opportunity to assess the role that diet, cooking methods, and other lifestyle and genetic factors have on the cause of cancer and other diseases. The results of the study will provide information that can be used to create a safe work environment and healthy lifestyle for agricultural workers and their families.

Study Objectives

Specific research goals are to:

• Characterize the cancer risks among study participants who have direct exposure to pesticides and other agricultural agents;
• Characterize the non-cancer risks, such as asthma and other respiratory diseases; neurologic diseases including Parkinson's; reproductive defects including birth and developmental defects in children; kidney disease; and autoimmune diseases, including arthritis, among study participants who have direct exposure to pesticides and other agricultural agents;
• Characterize the disease risks among spouses and children of farmers that may arise from both direct and indirect contact with pesticides and agricultural chemicals used in the home;
• Define specific work practices associated with high levels of pesticide and other agricultural exposures;
• Define biomarkers that may be used to monitor exposure to pesticides and other agricultural agents;
• Measure the degree of pesticide exposure among farmers and their families, particularly children.
• Investigate interactions between specific gene alterations and pesticide exposures that lead to increased disease susceptibility;
• Characterize the role of diet and lifestyle factors in development of cancer and other diseases among this population.

Background

Farmers in many countries, including the United States, have lower overall death rates and cancer rates than the general population. Lower death rates among farmers for heart disease and cancers of the lung, esophagus, bladder and colon, in particular, are thought to be due to lower smoking rates, as well as physically active lifestyles and dietary factors.

However, compared to the general population, the rates for certain diseases appear to be higher among agricultural workers. For example, the rates of asthma, neurological diseases, and spontaneous abortions are higher, which may be related to agricultural exposures. Farming communities also often have higher rates of leukemia, non-Hodgkin's lymphoma, multiple myeloma, soft tissue sarcomas, and cancers of the skin, lip, stomach, brain, and prostate. The rates for several of these tumors (i.e., non-Hodgkin's lymphoma, multiple myeloma, skin, brain, and prostate) also appear to be increasing in the general population.

Even though no one set of risk factors explains the higher cancer rates, the range of environmental exposures in the farming community are of concern. Farmers, farm workers, and farm family members may be exposed to substances such as pesticides, engine exhausts, solvents, dusts, animal viruses, fertilizers, fuels, and specific microbes that may account for these elevated rates. However, human studies published to date have not allowed researchers to sort out which of these factors are linked to which cancers.

Study Population

The vast majority of the nearly 90,000 participants in the Agricultural Health Study are either farmers or wives of farmers; about 50,000 are farmers and 32,000 are wives of farmers. All were recruited in North Carolina or Iowa.

Those called "private pesticide applicators" are farmers or nursery workers; out of the approximately 52,000 private applicators, about 2,000 are nursery workers. The study includes a small percentage of "commercial pesticide applicators" from Iowa who work for pest control companies or for businesses such as warehouses or grain mills that use pesticides regularly; about 5,000 are commercial applicators.

The entire AHS cohort includes about 50,000 farmers, 32,000 wives of farmers, 2,000 nursery workers, and 5,000 commercial pesticide workers. Children of farm families are also included in some of the studies.

Data Collection

During the initial recruitment from 1993 through 1997 (Phase I), participants completed a questionnaire about pesticide use, crops grown, livestock raised, personal protective equipment used, pesticide application methods employed, other agricultural exposures such as solvents, grain dusts, and welding fumes, work practices that effect exposures, and non-farm 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, from 1999-2003, consists of data collection and determination of mortality and cancer incidence among participants. The specific components are:

• Computer-assisted telephone interview (CATI): These interviews are designed to obtain information on pesticide use since enrollment, changes in health status, and detailed information on farming and work practices.
• Mailed Dietary Health Questionnaire: This questionnaire is designed to provide detailed information on cooking practices and diet.
• Buccal (cheek) cell collection: Buccal cell collection allows scientists to determine whether specific genetic alterations found in the DNA in cheek cells play a role in agricultural exposures and disease susceptibilities.
• Determining which participants developed cancer by contacting the cancer registries in each state.
• Determining which participants died by contacting the U.S. National Death Index (NDI), a computerized index of death record information collected from all state vital statistics offices and available to scientists for medical and health research.

Phase III follow-up began in 2004 and is scheduled to conclude in 2008. It will include the collection of additional data on diseases among the participants, additional agricultural exposures, and continued tracking of mortality and cancer incidence among participants. In addition, a series of smaller studies focus on the risk factors for specific diseases. These may involve additional questionnaires and the collection of blood, tumor, or urine samples.

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Related NCI materials and Web pages:

• Agricultural Health Study Home Page ¹
  (http://www.aghealth.org)
• Cancer Causes and Risk Factors Home Page ²
  (http://www.cancer.gov/cancertopics/prevention-genetics-causes/causes)
• Understanding Cancer Series: Cancer and the Environment ³
  (http://www.cancer.gov/cancertopics/understandingcancer/environment)

NCI's Cancer Information Service

Telephone (toll-free): 1–800–4–CANCER (1–800–422–6237)
TTY (toll-free): 1–800–332–8615
LiveHelp® online chat: https://cissecure.nci.nih.gov/livehelp/welcome.asp

Glossary Terms

A disease that causes inflammation and pain in the joints.

A chronic disease in which the bronchial airways in the lungs become narrowed and swollen, making it difficult to breathe. Symptoms include wheezing, coughing, tightness in the chest, shortness of breath, and rapid breathing. An attack may be brought on by pet hair, dust, smoke, pollen, mold, exercise, cold air, or stress.

A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease. A biomarker may be used to see how well the body responds to a treatment for a disease or condition. Also called molecular marker and signature molecule.

The organ that stores urine.

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.

A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

The longest part of the large intestine, which is a tube-like organ connected to the small intestine at one end and the anus at the other. The colon removes water and some nutrients and electrolytes from partially digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus.

The things a person eats and drinks.

The molecules inside cells that carry genetic information and pass it from one generation to the next. Also called deoxyribonucleic acid.

The muscular tube through which food passes from the throat to the stomach.

A record of the relationships among family members along with their medical histories. This includes current and past illnesses. A family history may show a pattern of certain diseases in a family. Also called family medical history.

Inherited; having to do with information that is passed from parents to offspring through genes in sperm and egg cells.

The number of new cases of a disease diagnosed each year.

One of a pair of organs in the abdomen. Kidneys remove waste from the blood (as urine), produce erythropoietin (a substance that stimulates red blood cell production), and play a role in blood pressure regulation.

Cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of blood cells to be produced and enter the bloodstream.

One of a pair of organs in the chest that supplies the body with oxygen, and removes carbon dioxide from the body.

A type of cancer that begins in plasma cells (white blood cells that produce antibodies). Also called Kahler disease, myelomatosis, and plasma cell myeloma.

Having to do with nerves or the nervous system.

Any substance that is used to kill insects and other pests.

A gland in the male reproductive system. The prostate surrounds the part of the urethra (the tube that empties the bladder) just below the bladder, and produces a fluid that forms part of the semen.

Something that increases the chance of developing a disease. Some examples of risk factors for cancer are age, a family history of certain cancers, use of tobacco products, being exposed to radiation or certain chemicals, infection with certain viruses or bacteria, and certain genetic changes.

A cancer that begins in the muscle, fat, fibrous tissue, blood vessels, or other supporting tissue of the body.

An organ that is part of the digestive system. The stomach helps digest food by mixing it with digestive juices and churning it into a thin liquid.

An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancer), or malignant (cancer). Also called neoplasm.

Fluid containing water and waste products. Urine is made by the kidneys, stored in the bladder, and leaves the body through the urethra.

In medicine, a very simple microorganism that infects cells and may cause disease. Because viruses can multiply only inside infected cells, they are not considered to be alive.