Pesticide Exposure Increases Breast Cancer Risk

One in eight women will be diagnosed with breast cancer at some point in her life. That’s about 12.9 percent of American women. 

Most of us are familiar with the breast cancer risk factors often discussed such as genetics including the BRCA1 and BRCA2 genes. Age is another risk factor as most women are diagnosed after age 50 as they enter into the menopausal years.

More exposure to estrogens increase risk as well, affecting those who begin menstruation early or have more menstrual cycles during reproductive years. 

We know that exercise, maintaining a healthy weight and eating well are protective for cancer, which is good news because these are modifiable risk factors.

But beyond this, most women are not often given much guidance about prevention. Today we are going to talk about another risk factor: exposure to pesticides. 

We’ve known for decades about the negative consequences of spraying chemicals in the environment in terms of reproduction and health for animals and humans.

Now, even more evidence is mounting that exposure to chemicals, such as pesticides, may be driving rates of breast cancer even higher. 

This article addresses:

  • New research linking four commonly used pesticides to breast cancer
  • Evidence for other environmental chemicals and breast cancer
  • What you can do, starting now, to reduce your risk

New Research Linking Pesticide Exposure And Postmenopausal Breast Cancer

A 2021 French study published in the International Journal of Epidemiology takes a close look at dietary pesticides and breast cancer risk. Over 13,000 women participated in the study through surveys of dietary patterns. Researchers correlated the data with pesticide residues found in food. 

While this type of study shows correlation, and not causation, the results are quite staggering. Eating conventional food containing higher levels of pesticides was associated with a 73 percent increase in breast cancer risk!

Women carrying extra weight through menopause saw higher levels of risk. Conversely, those eating a primarily organic diet, lower in pesticide exposure, saw a 43 percent reduction in risk of developing post-menopausal breast cancer! 

What explains these results? Many pesticides have carcinogenic properties and are endocrine disruptors in the body, affecting hormonal balance. Hormones, and specifically estrogen, often play a role in breast cancer and we are exposed to more estrogen-like compounds through chemicals in our food. 

In addition, the body may have a hard time detoxifying pesticides and other chemicals and store them in fat cells, explaining why being overweight or obese increases risk for cancer and other chronic disease. 

The study points to four specific chemicals that correlate with cancer risk: 

 1. Imazalil – A fungicide commonly used on bananas, citrus, wheat and in chicken hatcheries. Since 1999, EPA classified Imazalil as “likely to be carcinogenic.” In California, Imazalil is listed as “known to the State to cause cancer” under the Safe Drinking Water and Toxic Enforcement Act of 1986. 

 2. Thiabendazole – A fungicide commonly used when planting potatoes, sweet potatoes, soy and wheat. It is also used as a post-harvest application to citrus, apples, pears, bananas, mangos, papaya, plantain, carrots, avocados, peas and potatoes. The EPA classifies thiabendazole as “likely to be carcinogenic at doses high enough to cause disturbance of thyroid hormone balance.”

 3. Chlorpyrifos – A widely used organophosphate insecticide used in food crops and animal feed including corn, soy, fruit, nut trees, brussels sprouts, cranberries, broccoli cauliflower and others. It is also used on golf courses, turf, fences and to kill mosquitos, ants and roaches. Chlorpyrifos have been found, even in small doses, to damage the brains of children. 

 In a 2019 study of post-menopausal breast cancer in Californian women, those women exposed to chlorpyrifos had breast cancer occurrences three times higher than women who were not exposed. Those living in agricultural regions may be exposed through the air they breathe. 

 4. Malathion – Another organophosphate insecticide used in food crops to kill insects such as aphids and Japanese beetles. It is used on a wide variety of fruit, vegetable and grain crops, including berries, cruciferous vegetables, lettuce, citrus fruits and wheat. It’s also used on cotton crops, to kill mosquitos and even by home gardeners. Exposure may cause acute and life-long health effects and is listed as having “suggestive evidence of carcinogenicity” by the EPA. 

While research and data continues to lack about the safety of pesticides and other environmental chemicals, we have even less data about the cumulative effects when we are exposed to multiple, or even hundreds, of toxins on a daily basis via water, air and food. 

In an independent study, the Environmental Working Group found these four chemicals in nearly 90 percent of citrus samples tested. While we think it may be safer to eat conventional foods with a thicker skin, we may need to think again. 

The same French researchers who conducted this breast cancer study found in a previous study that a diet high in organic foods reduces the risk of cancer. Published in 2018 in JAMA Internal Medicine, this previous study didn’t look at specific pesticides, but found those people who choose organic food regularly had lower rates of cancer in general. 

More Evidence

The study discussed here adds to a long list of evidence warning about the cancer connection with other chemicals commonly used on food crops. Let’s take a look:

  •  Glyphosate – This herbicide, found in Monsanto’s RoundUp products persists in the environment and is linked to cancer. California is working to have products labeled under Prop65 as possible carcinogens, similar to how cigarettes are labeled.


  • DDT – an organochloride pesticide used to kill mosquitos, has been banned globally since 2004, but continues to persist in the environment. DDT exposure in infancy through puberty has been linked to breast cancer during early post-menopause.  In addition, for those born after 1931, higher levels of DDT in the blood predicted a five-fold increase in breast cancer. 


  • Organochlorines – DDT is a famous example of organochlorines, but there are others including DDE. A 2019 study showed that organochlorine concentrations in the blood are associated with increased breast cancer risk in Iranian women. This is a global problem. 

How To Reduce Breast Cancer Risk

While there are certain things we can’t control such as genetics or age, there are a lot of cancer risks that are modifiable based on our diet and lifestyle. How we live informs all aspects of health and it’s never too late to begin to put these pieces in place.  

  • Choose organic. While organic food is sometimes brushed off or deemed unnecessary, it is likely one of the most important things that you can do to decrease your breast cancer risk over your lifetime. Choosing organic food, day in and day out, dramatically decreases the amounts of pesticides you are exposed to, many of which are directly linked to breast cancer. 

To learn more about eating organic, read: Benefits of Organic Food – How to Eat Organic on a Budget

  • Optimize estrogen levels and detoxification. Optimizing estrogen metabolism is a Functional Medicine approach to reducing cancer risk. Hormone testing, including the Every Life Well DUTCH Hormone panel, is the perfect place to start. Estrogen is detoxified through Phase 1 and Phase 2 detoxification in the liver, where certain dietary compounds such as DIM and sulforaphane as well as methylation support are helpful. This test helps to identify hormone levels, metabolites and functioning of methylation and detoxification pathways. 

Estrogen leaves the body via Phase 3 through the colon. The GI MAP is another helpful test that looks at this piece and helps to inform strategies to allow excess estrogen to clear from the body and optimize digestive and microbiome health.

Please seek support from a Functional Medicine practitioner for personalized guidance. 


  • Decrease exposure to endocrine disruptors. Diet isn’t the only place we are exposed to chemicals that have hormone-disrupting and cancer-causing properties. We are also exposed through the air we breathe, the water we drink, the materials in our home and the products that we use. You may not think that your makeup or sunscreen makes much of a difference, but it all adds up when you consider how much we are exposed to on a daily basis. Minimizing our exposures can make a measurable difference. It’s relatively easy to swap out products and filter drinking water. 


To learn more about how to decrease endocrine disruptors in your daily life, read this article

In addition, be sure to exercise, stop smoking, reduce or eliminate alcohol and work to maintain a healthy weight for your body. Please seek out support where needed. 

One of the perceived barriers to organic food and Functional Medicine is cost. Our current medical system doesn’t support or prioritize prevention, which is really the best way to address breast cancer and other health concerns.

While these interventions may have more costs up front, saving you from a cancer diagnosis (or recurrence) is priceless. We may never know the diseases we prevent, but do we really want to take that risk? 

With the mounting evidence linking pesticides to an increased risk of breast cancer, and a dramatic one at that, it is prudent to be aware of this issue in order to make the best decisions about our bodies and our communities.