What are the links between pesticides and breast cancer?

As spring approaches, many of us will be pulling on our gardening gloves to prepare for the growing season ahead.  However, along with our blossoming flowers and plants, there will inevitably be weeds that will need to be removed.

Many people will reach for a weedkiller (pesticide) to help eradicate them. But what are the health impacts of our widespread use of pesticides, and what are the links to breast cancer?

How are pesticides used and what is the impact on our health?

Pesticides are widely used to control pests (insects (insecticides), rodents (rodenticides), fungi (fungicides) and weeds (herbicides). Many are toxic and potentially harmful to animals, plants and humans (1).

Pesticides can have short-term, acute effects such as respiratory, eye and skin irritation or nausea.  High concentrations may even cause death. They also have chronic, long-term effects, such as neurological or reproductive effects (2).

Some have the potential to disrupt our hormone systems, known as endocrine disrupting chemicals (EDCs) (3), and can play a role in the development of cancers, such as non-Hodgkin lymphoma, colorectal and breast cancers (4).

We get exposed to a cocktail of pesticides primarily through the food we eat and the water we drink. Pesticide residues are often found in or on food after pesticides are used on food crops; these may be particularly harmful to our health. Many can build up in our bodies and are routinely found in fat tissue, blood and urine (5).

Why are we concerned about pesticide exposure?

Pesticides could increase breast cancer risk by acting as carcinogens (cancer-causing agents). Causing gene mutations that lead to or promote cancer.  They may act as EDCs and disrupt sex hormones, including oestrogen (6). High levels of natural oestrogen increase breast cancer risk (7).

Similarly, EDCs that affect oestrogen by mimicking its actions or effectively increasing its concentration in the body may also increase risk. Exposure to such pesticides in the womb may affect breast development and make us more vulnerable to developing breast cancer as adults (8).

Many pesticides used today are EDCs that affect oestrogen (9) and/or cause mammary cancer in animals (10).  They may also increase breast cancer risk. Most studies examining direct pesticide exposure with breast cancer incidence show an elevated risk (11, 12, 13).

Although there is currently insufficient evidence to show eating organic food reduces breast cancer risk (14), there is evidence that organic food contains less pesticide residue (15). We know that certain pesticides are linked to breast cancer risk, so we would recommend eating organic food whenever possible.

What can you do to lower your exposure?

• Buy organic fruit and vegetables as often as you can: they are largely pesticide-free and widely available. To identify fruit and vegetables grown organically, look for organic logos.
• Know which fruits and vegetables are exposed to the highest levels of pesticide. Check out the Dirty Dozen – lists of fruit and vegetables with the most pesticide residues.
• Grow your own produce: if you have a garden, try growing your own vegetables and fruit. Herbs can be grown on a window sill in small pots too.
• Wash and/or brush fruit and vegetables well to help remove pesticide residue.
• To reduce your use of pesticides, keep your plants healthy so they don’t attract bugs.
• Homemade pesticides are a safe choice and can be made from inexpensive ingredients that most people have in their homes.
• Make your garden welcoming for small animals, birds and insects. Let them do the work for you. Hedgehogs and toads eat slugs and snails.  Ladybirds love to eat greenflies. Find places for bug boxes and habitats where creatures can hibernate.

For more information on the links between pesticides and breast cancer, see our pesticide factsheets, and for tips on how to reduce your exposure, visit our prevention hub.

References:

1. World Health Organization. Pesticides. World Health Organization. https://www.who.int/topics/pesticides/en/ (Accessed 25 Feb 2022).
2. Pesticide Action Network UK. Impacts of pesticides on our health. https://www.pan-uk.org/health-effects-of-pesticides/ (Accessed 24 Feb 2022).
3. Mnif, W. et al. (2011). Effect of endocrine disruptor pesticides: a review. International journal of environmental research and public health, 8(6), 2265–2303. https://doi.org/10.3390/ijerph8062265
4. Nicolopoulou-Stamati, P. et al. (2016). Chemical Pesticides and Human Health: The Urgent Need for a New Concept in Agriculture. Frontiers in public health 4: 148. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4947579/
5. Genuis, S. J. et al. (2016). Human Elimination of Organochlorine Pesticides: Blood, Urine, and Sweat Study. BioMed research international, 2016, 1624643. https://doi.org/10.1155/2016/1624643
6. Kaur, K. et al. (2018). Occupational Pesticide Exposure, Impaired DNA Repair, and Diseases. Indian Journal of Occupational and Environmental Medicine 22: 2: 74–81. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6176703/
7. Travis, R. C. et al. (2003). Oestrogen exposure and breast cancer risk. Breast cancer research : BCR 5: 5: 239–247. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC314432/
8. Kass, L. et al. (2020). Relationship between agrochemical compounds and mammary gland development and breast cancer. Molecular and cellular endocrinology 508: 110789. https://www.sciencedirect.com/science/article/abs/pii/S0303720720300897
9. Mesnage, R. et al. 2017. Evaluation of estrogen receptor alpha activation by glyphosate-based herbicide constituents. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association 108: Pt A: 30–42. https://pubmed.ncbi.nlm.nih.gov/28711546/
10. Cabello, G. et al. (2001). A rat mammary tumor model induced by the organophosphorous pesticides parathion and malathion, possibly through acetylcholinesterase inhibition. Environmental health perspectives 109: 5: 471–479. https://pubmed.ncbi.nlm.nih.gov/11401758/
11. Mekonen, S. et al. (2021). Exposure to organochlorine pesticides as a predictor to breast cancer: A case-control study among Ethiopian women. PloS one, 16(9), e0257704. https://doi.org/10.1371/journal.pone.0257704
12. Yang, K. J. et al. (2020). Organophosphate Pesticide Exposure and Breast Cancer Risk: A Rapid Review of Human, Animal, and Cell-Based Studies. International journal of environmental research and public health, 17(14), 5030. https://doi.org/10.3390/ijerph17145030
13. Band, P. R. et al. (2000). Identification of occupational cancer risks in British Columbia. A population-based case-control study of 995 incident breast cancer cases by menopausal status, controlling for confounding factors. Journal of Occupational and Environmental Medicine 42: 3: 284–310. https://pubmed.ncbi.nlm.nih.gov/10738708
14. Park, Y. M. et al. (2019). Association Between Organic Food Consumption and Breast Cancer Risk: Findings from the Sister Study (P18-038-19). Current Developments in Nutrition 3: Supplement_1. https://academic.oup.com/cdn/article/3/Supplement_1/nzz039.P18-038-19/5517295
15. Andersen, M. A. et al. (2017). Human health implications of organic food and organic agriculture: a comprehensive review. Environ Health 16, 111. https://doi.org/10.1186/s12940-017-0315-4