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Welcome to PSR's Environmental Health Policy Institute, where we ask questions -- then we ask the experts to answer them. Join us as physicians, health professionals, and environmental health experts share their ideas, inspiration, and analysis about toxic chemicals and environmental health policy.

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The Health Costs of Our Food Production System: Pesticide Exposure and Effects on Farmers, Farm Workers, and Rural Residents

By Susan Kegley, PhD

This essay is in response to: How does our nation's reliance on pesticides affect the health of those who plant and harvest our food?

Our current conventional agricultural system relies heavily on synthetic pesticides, and when pesticide exposure is mentioned, the first thought that may come to mind is pesticide residues on food. But for those who live in agricultural areas or work on conventional farms, exposure is a full-body experience. Farm workers have the highest exposures, since they are often involved in applying pesticides or working in the crop soon after the pesticides are applied. And ironically, people seeking a bucolic rural lifestyle may also have higher exposures simply from living near farms where pesticides are used.

Exposure Routes

Farm workers and rural residents are exposed to pesticides through touching plants or other surfaces contaminated with pesticides, drinking water, and merely breathing the air.

Dermal contact with treated plants can be a significant source of exposure for workers reentering fields after pesticide applications, particularly for workers involved in tasks that require contact with treated plants, such as picking fruit, pruning branches, and training vines. Also a concern for farm worker families is take-home exposure, where workers bring pesticide residue into the home on their clothes and shoes.

Drinking water may also be a source of exposure in agricultural areas. Many pesticides are soluble enough in water to leach through the soil and into groundwater or run off to surface waters. If they do not readily degrade, they can contaminate ground and surface water sources of drinking. Herbicides are particularly problematic in this regard, and the US Geological Survey water monitoring program indicates that many areas in the Midwest and other locations have extensive ground and surface water pesticide contamination, predominantly from herbicides such as atrazine, metolachlor, acetochlor, and alachlor used on corn and soybean fields.[1]

Airborne spray drift of pesticide aerosols and dusts from a poorly done application is also a major source of exposure for both farm workers and rural residents. While spray drift can occur with any pesticide, a subset of chemicals are inherently volatile and can evaporate off of the application site for several days to several weeks after the application. This volatilization drift is a more insidious, but no less problematic, source of inhalation exposure for some pesticides. While EPA attempts to regulate spray drift through label instructions, the agency is only now beginning to consider exposures from volatilization drift.

California’s Air Resources Board[2] and Pesticide Action Network (PAN)[3] have both done air monitoring to evaluate the scope and magnitude of airborne pesticides, and have found that for some pesticides, legal use results in inhalation doses that far exceed levels of concern set by regulatory agencies. The most problematic pesticides for inhalation exposure are the fumigants methyl bromide, 1,3-dichloropropene, metam sodium, chloropicrin and methyl iodide. For these pesticides, the high application rates (hundreds of pounds per acre) and very high volatility of these nearly gaseous chemicals contribute to their drift potential, and acute poisoning incidents that affect tens to hundreds of people are not uncommon.[4] Volatilization drift is also an issue for insecticides such as endosulfan, chlorpyrifos, diazinon, and malathion, and certain fungicides and herbicides, including chlorothalonil and trifluralin, which PAN found repeatedly in several studies.

Several research centers, most notably the Pacific Northwest Agricultural Safety and Health (PNASH) Center at the University of Washington[5] and the Center for Environmental Research and Children’s Health at the University of California, Berkeley,[6] have studied how the proximity of pesticide use relates to pesticide residues in house dust and pesticide metabolites in urine. Their results show that homes within a few hundred feet of fields have higher concentrations of pesticides in dust; correspondingly, the children living in those homes have higher levels of pesticide metabolites in their urine than those who live further away. Children are particularly vulnerable to exposure because of their behaviors—they spend more time on the ground or floor and put objects in their mouths as a means of exploring. They also breathe more air, drink more water, and eat more food per pound of body weight than an adult does, which provides a higher dose of chemical.

Health Effects of Pesticides

The acute and chronic health effects that result from pesticide exposure are most prevalent in people with the highest exposures. Elevated risks of certain kinds of cancer, Parkinson’s disease, autism and other neurological effects, reproductive and developmental disorders, and increased respiratory disease have all been associated with exposure to pesticides. While there isn’t space to review all of these effects in detail in this article, the work of several research groups who focus on pesticides and health effects provides a good introduction to the health effects of pesticide exposure.

A number of excellent epidemiological studies have been done (or are in progress) focusing on the incidence of different cancers in farmers and farm workers. The Agricultural Health Study run by the National Cancer Institute is a large, prospective study of farmers and their spouses, involving over 89,000 participants from Iowa and North Carolina.[7] Findings demonstrate that overall cancer occurrence among members of the study group is significantly lower than comparable populations, a fact attributed to a lower use of tobacco products among farmers and a more active lifestyle. Nevertheless, there are several types of cancer that occur more frequently among farmers and their spouses, including prostate cancer, melanoma, and ovarian cancer. Links between lung, colon, and some blood-related cancers and use of specific pesticides have also been established by this work.

The California Cancer Registry[8] has published a number of studies on farm workers and cancer, with findings that workers have elevated risks of lymphomas and leukemias, as well as prostate, brain, cervix, and stomach cancers.[9]

The CHAMACOS project has been studying the farm worker population in the Salinas Valley since 1999 to examine the effects of pesticides, other chemicals, and other factors on children’s health.[10] A project of the UC Berkeley Center for Environmental Research and Children’s Health, CHAMACOS has focused on chemical exposure, health effects, and genetic factors affecting pesticide metabolism and excretion. A recent review article by the CHAMACOS researchers provides perspectives on pesticides and neurodevelopment, with the research showing a link between in utero exposure to organochlorine and organophosphorus pesticides and impaired neurodevelopment.[11] This finding is consistent with the work from the Columbia Center for Children’s Environmental Health in which an increased incidence of pervasive developmental disorders were observed for children exposed to insecticides in utero in an urban setting.[12]

Other research groups have used California’s Pesticide Use Reporting data to go beyond worker exposures and study the relationship between exposures and health effects for the larger rural community. These studies demonstrate links between locations of pesticide use and higher incidences of Parkinson’s disease, cancer, asthma, and autism, providing evidence for exposure through proximity.[13], [14]

Finally, the Pesticide Education Center has summarized a number of epidemiological studies on cancer in adults and children, neurological effects, and reproductive outcomes as related to pesticide exposure.[15] These summaries provide information on links between disease outcomes and exposures to certain classes of pesticides, specific occupational exposures, or locations of residence.

The Solution

Our nation’s reliance on pesticides to produce our food has come at a cost to those who work in farming and live in rural communities. But it doesn’t have to be this way. We should take a cue from Europe and begin by removing the most toxic pesticides from the market. In the US, the fumigant pesticides have the highest exposure potential and should be among the first to go. In California, where pesticide use tracking is implemented, we know that this would remove 30 million pounds of toxics from the environment each year. This would account for approximately 20% of the agricultural use pesticides, but represents a much larger fraction of the highly toxic pesticides applied in California.

The role of government in this process should be to provide assistance to farmers to transition to less toxic methods of farming. This could be done by restructuring crop insurance programs, providing advice through extension services, and funding research into new methods of pest management, expansion of existing methods to commercial scale, and development of crop varieties that don’t require heavy doses of toxic pesticides to survive. The net result will be a healthier food system from top to bottom. Food consumers, farmers and farm workers, and rural residents will all benefit.


Editor's note: if you'd like to take action on pesticide policy, click here.



[2] California Air Resources Board and California Department of Pesticide Regulation, Toxic Air Contaminant Program Monitoring Reports.

[4] Lee S-J, Mehler L, Beckman J, et al. Acute Pesticide Illnesses Associated with Off-Target Pesticide Drift from Agricultural Applications—11 States, 1998–2006. Envi. Health Persp. doi: 10.1289/ehp.1002843

[5] Pacific Northwest Agricultural Safety and Health Center, University of Washington. Chemical Exposure.

[6] The CHAMACOS Study. 2011. Center for Environmental Research and Children’s Health.

[7] National Cancer Institute, 2011. Agricultural Health Study.

[8] California Department of Public Health, 2011. California Cancer Registry. 

[9] Mills PK, Dodge J, Yang R 2009. Cancer in Migrant and Seasonal Hired Farm Workers. J. Agromedicine 14:185–191.

[11] Rosas LG, Eskenazi B. 2008. Pesticides and child neurodevelopment. Curr Opin Pediatrics 20(2): 191–197.

[14] Beate Ritz, UCLA.

[15] Marion Moses, 2011. Educational Materials. Pesticide Education Center.

Comments

Janet Evans said ..

I would like to know if there is a study of any disorders [attention span, learning disabilities, or birth defects] of children of agricultural workers, that are derived from the health of the parent, usually a male...sperm etc. and not from a child living near, or working in a field where pesticides are used.

October 16, 2014

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