Sierra Club of/du Canada

Pesticide Fact Sheet


Your Chances

The Canadian Cancer Society estimates that currently a Canadian woman has a one in nine lifetime risk of being diagnosed with breast cancer. Male breast cancer is very rare at one percent of all cancers in males (1).

Are more diagnoses being made mainly because of better detection methods? Possibly, but the steady rise in incidences of breast cancer since the 1940s pre-dates mammography, so this does not explain why it has become so common (2).

Causes and Risk Factors

Only about five percent of cases in females are passed on by the breast cancer gene (2). Other causes are more difficult to predict and to prove. Exposures to high doses of chest X-rays, alcohol and tobacco use are all recognized risk factors. Organochlorine pesticides and other environmental toxics are highly suspect as further possible causes or promoters. Organochlorines are found primarily in pesticides but can also be found in plastics and some pharmaceuticals.

Timing of events in one’s reproductive history is also tied to the likelihood of developing breast cancer, and so this too can be considered to be a risk factor. Timing of such events as births and age at menopause also gives an indication of lifetime exposure to estrogen, another possible cause of breast cancer (2).

Pesticides that Mimic Estrogen are Bad News

But isn’t estrogen a good thing for women? While it is essential for female reproductive functions, it can trigger and or feed some types of breast cancers.

Like cholesterol, ‘good’ and ‘bad’ estrogens are manufactured by the body. ‘Good –estrogen’ production can be stimulated by eating foods such as soya beans and broccoli, that break down quickly in the body and seem to protect against breast cancer.

‘Bad-estrogen’-production can be stimulated by synthetic estrogens in birth-control pills and estrogen replacement therapies, and also by the presence of some estrogen-mimicking organochlorine pesticides, plastics and bonding agents in detergents and paints (2).

Pesticides are commonly found in our food, indoor and outdoor air, drinking water, and of course in insect repellants applied to our skin (3)(4). Some do not break down easily in the environment and so accumulate up the food chain where they are stored in our fat.

Reducing the Chances of Breast Cancer

Sadly, an effective way to rid our breast fat of pesticides suspected of causing breast cancer is breast-feeding (5)(6), but now breast milk has become the most contaminated of all human foods (5).

So Should Women Still Breast-Feed?

Generally, yes! Women who have breast-fed tend to have less breast cancer, likely because of the downloading of toxins(5)(6). Overall, the research indicates that the enhanced immunity benefit to infants outweighs any of the risks of toxics in human milk. Unfortunately, though, the milk of some women, especially those in the high Arctic, has become quite seriously contaminated (7) and could be too contaminated to be sold as a food product..

How Can Women Minimize Exposure to Cancer Causing Substances?

  • Eat organically produced food, try to eat lower on the food chain and limit consumption of animal fat. (8)(9)

  • Don’t use pesticides on your skin, in your homes or on your gardens. There are alternatives that work, and don’t forget that chemical pesticides are a relatively recent invention.

  • Use pottery and ceramic dishes, Don’t microwave or put hot liquids in plastics that aren’t microwavable.(10)

  • Be leery of permanent hair dyes especially black and dark brown.(8)

  • Avoid breast implants. (8)

  • Avoid or minimize alcohol and tobacco use.(8)

  • Avoid a sedentary lifestyle – stay active by incorporating exercise into your daily life.(8)
  • Contact your municipal, provincial and federal government representatives and tell them you want immediate and effective protection from the dangers of pesticides, and that all need to be re-evaluated for their total bio-accumulative potential as toxics now, not properly protecting us from the risks of these chemicals.(8)

  • Support a ban on the nonessential use of pesticides in your municipality!


  1. Canadian Cancer Society Information Service statistics 1999. Call 1-888-939-3333

  2. Davis, DL and Bradow, HL: Can Environmental Estrogens Cause Breast Cancer? Scientific American, October 1995

  3. Pesticides and Human Health, Environmental Health Committee Newsletter, The Ontario College of Family Physician, 1998,

  4. Davies, K: Pesticides and Your Child: an overview of exposures and risks, CPR publication, Sierra Club of Canada, 1997

  5. Steingrabger, S, in Protecting Public Health and the Environment: Implementing the Precautionary Principal, Raffensperger, C and Tickner,J, editors, Island Press, 1999, (also recommended: Steingraber, S: Living Downstream, Addison Wesley Publishing, 1997)

  6. Land, P: Linkage of Breast Cancer and Pesticides through Lactation Studies; presented at the second World Breast Cancer Conference, July 1999 and available through CPR, Sierra Club of Canada

  7. Jensen, J et al,( eds): Canadian Arctic Contaminants Assessment Report, Northern Contaminants Program, Indian and Northern Affairs Canada, 1997

  8. Epstein, Samuel S. & Steinman, David: The Breast Cancer Prevention Program, Macmillan, 1997.

  9. Emmet, B, Commissioner of the Environment and Sustainable Development’s Annual Report, May 25,1999, cited in Globe and Mail, May 26,1999: Ottawa faulted on chemicals, pesticides: Canadians at risk, report charges.

  10. Colbourn, Theo, Dumanoski, Dianne & Peterson Myers, John: Our Stolen Future, Penguin Books, 1996.

Web Sites for Breast Cancer

The following information is provided for information purposes only and is not intended to replace medical advice. If you have any questions about your cancer treatment, please ask your doctor, nurse or radiation therapist. – Canadian Breast Cancer Network
A national network of groups and individuals which, amongst other activities, promotes education and awareness and advocates for people affected by breast cancer.
Questions and Answers on Breast Cancer: a guide for women and their physicians. Based on the clinical practice guidelines.
Clinical practice Guidelines for the Care and treatment of breast cancer. – Breast Cancer Action-Ottawa
Information and support for breast cancer patients and their families and related activities and events in the Ottawa are. – Canadian Breast Cancer Research
Encourages and supports research into the prevention, treatment and control of breast cancer. – Willow Breast Cancer Support and Resource Centre
Information and emotional support for breast cancer patients. – Inflammatory Breast Cancer Help page
Information, personal stories, mailing list and useful links for women with inflammatory breast cancer.

Sierra Club of Canada
412-1 Nicholas St.
Ottawa, ON
tel: (613) 241-4611
fax: (613) 241-2292