Agricultural chemicals and human health

World pesticide use has reached nearly 6 billion pounds per year, with the United States alone accounting for over 20% of that use. The Environmental Protection Agency has registered and approved almost 1,400 pesticides with over 900 active ingredients for use in the U.S. The majority are used on conventional farms in the form of synthetic herbicides, insecticides, fungicides, and fumigants.

Organic can be a tool to drastically reduce the use of these pesticides. Unlike conventional farms, organic farms are required by law to implement cultural methods to control pests before any pest control substance may be applied.  Some of the most common cultural practices used by organic farmers to manage pests include crop rotations, intercropping, the use of buffers and hedgerows, and the promotion of soil health to balance the farm ecosystem.

In cases where these practices are ineffective in combatting a pest, organic farmers are allowed to use naturally occurring pest control products--restricted to about 25 synthetic materials approved by the National Organic Standards Board and deemed to pose little threat to humans and the environment. These substances undergo review every five years to assess any new knowledge of risk, and to ensure protection of the population most vulnerable to the adverse health effects of pesticide exposure.

Impacts on farmers and farmworkers

By definition, pesticides are toxic to living organisms, so it is not surprising they can also be toxic to the environment and humans. While pesticides’ adverse effects on biodiversity are well documented, their unintended effects on humans are perhaps the most concerning. Exposed to pesticides at higher doses and with greater frequency than the public, farmers and farmworkers are at the greatest risk to the serious consequences of exposure.

A large body of research documents the health risks associated with both short- and long-term exposure to pesticides: cancer, neurodegenerative disorders and poor reproductive health. Even with the best management practices while handling and applying pesticides, farmers and farmworkers are still at risk for exposure. The adoption of organic techniques that avoid the use of toxic, synthetic pesticides provides the surest safeguard against chemical-related occupational health problems.

Interested in learning more about how organic impacts farmworker health? The Organic Center put together a report that synthesizes 129 research studies from around the world that cover topics ranging from the impacts of toxic, synthetic pesticides on the health of farmworkers and farm communities, to the science supporting the efficacy of chemical-free pest control to demonstrate how organic certified production can substantially benefit those working in agricultural systems. The report is titled “Organic Agriculture: Reducing Occupational pesticide exposure in farmers and farmworkers.” Download at


Pesticide impacts on consumers

Not only does the ban on toxic, synthetic pesticides on organic farms help support farmer and farmworker health, it also reduces pesticide residue levels on food. A large body of research shows that organic crops have lower levels of pesticide residues, and that eating organic food decreases your exposure to pesticides. One study found that by eating “mostly” organic foods, study participants decreased urine pesticide levels by 90%.

The Organic Center has some interesting work in collaboration with Emory University on this front, looking at levels of pesticides, antibiotics, and growth hormones on in-store organic and conventional milk. The results are being considered for publication now, so keep an eye out for more information on our results soon!

Avoiding pesticides on your food is important, because new research suggests that decreasing dietary exposure to pesticide residues by choosing organic could help reduce the risk of several health issues. Even low levels of pesticide exposure can have a negative effect on health risk levels, especially when that exposure is chronic. While research on how pesticide residues on food affect the health of consumers is scant, new studies highlight reasons for concern.

One study that came out in October suggested that eating an organic diet may significantly lower cancer risk. Researchers compared French adults who frequently consumed organic foods to those who never consumed organic foods and found a 25% reduction in overall cancer risk. As stated by the authors, “A higher frequency of organic food consumption was associated with a reduced risk of cancer.” They also looked at specific cancer types and found that eating an organic diet significantly decreases the risk of developing three cancer types: Non-Hodgkin lymphoma (by 86%), all lymphomas (by 76%), and postmenopausal breast cancer (by 34%).

Although the study has some limitations, it offers great jumping-off points for future research. For example, organic food consumption was self-reported, so we can’t be sure that people accurately estimated how much of the food they ate was organic. Another issue that could be improved is examining the specific types of foods that consumers are choosing when they purchase organic, as different food categories have different levels and classes of pesticides. Examining the nuances of what foods are having the biggest impact on cancer risk reduction would enable us to better understand how organic diets impact our health.

In the past few years, we’ve started to see research come out linking organic diets with health benefits. For example, the authors mention the Million Women Study published in 2014. One finding is a reduction in non-Hodgkin lymphoma risk associated with eating organic food. A few other studies have found that eating organic decreasing the risk of certain birth defects, and that dietary exposure to pesticide residues can have an impact on reproductive health for both men and women.

When you think about how pesticides impact the health of our population it’s important to take all these factors into account. The Organic Center is working on a project in collaboration with Harvard University that synthesizes the multifaceted issue of pesticide impacts on human health and focuses on the primary benefits of organic in their NetPositives of Organic Farming Project. Learn more about the project progress.

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Dr. Jessica Shade is the Director of Science Programs for The Organic Center (