To celebrate Pesticide Action Week, Dr Robin Mesnage, a Research Associate at Kings College and member of Breast Cancer UK’s Scientific Review Panel investigates the links between pesticides and breast cancer risk.

What do we know about pesticides and breast cancer risk?

Whether pesticides have toxic effects and cause breast cancer is a burning question, both for the scientific community and for consumers who want to lead a healthy lifestyle.

What are pesticides and where they are used?

A pesticide can be a weedkiller used to clear invasive weeds in agriculture fields. It can also be a fungicide or an insecticide. Pesticides are not only sprayed in agricultural fields, but also in private or public gardens, on rail tracks, industrial sites, golf courses, or even on verges of most cities.

In a recent scientific study 1, grass samples from playgrounds and schoolyards in Italy were found to be contaminated by dozens of pesticides. Some of them are known endocrine disrupting chemicals, with harmful properties that raise questions about their potential role in breast cancer development.

Pesticides are generally linked to modern agriculture. Farmers who apply pesticides in their fields are often criticised by individuals or environmental organisations, causing growing resentment. This is sometimes known as ‘agribashing’. We should not neglect the challenges farmers are facing. The toxic effects of pesticides in farming communities are well known. The largest agricultural study conducted in the US has identified a link between the use of some insecticides and breast cancer risk among farmers’ wives 2.

Investigating the role of pesticide exposures in breast cancer development for women working on farms should be a priority. Women represent a large proportion of the agricultural workforce. Women may have greater risk of pesticide exposure than men, as suggested in a study of Latina farmworkers in the US 3. It was found that women are often less protected than men when they handle pesticides, because they have difficulty accessing properly fitting personal protective equipment which is typically designed for men.

What about consumers?

Consuming fruits and vegetables grown on organic farms will certainty reduce an individual’s pesticide exposure. This is not very surprising. However, some major sources of pesticide exposure are closer to home. An inconvenient truth is that large quantities of insecticides are bought to kill mosquitoes, clothes moths, or other inconvenient bugs.When blood or urine tests reveal an exposure to a dangerous dose of pesticide, the source is often domestic.

Let’s adopt a precautionary approach and avoid unnecessary toxic exposures.

Ask yourself, is this mosquito on the wall worth a pesticide exposure? Some flea and tick collars for dogs contain doses of insecticides sufficient to kill approximately 1 billion honey bees or a thousand partridges. The use of these collars is a major source of insecticide exposure 4. Ask yourself if your dog really needs it?

New clothes are also frequently contaminated by pesticides sprayed on cotton, or because they are included in protective treatments during manufacturing. Always wash new clothes before wearing them.

The issue of screening for pesticides

Another problem is that pesticide screening in blood or urine is almost never done. Even after decades of controversies surrounding the toxic effects of pesticides 5, it is still not clear whether exposures at low doses present in the environment can cause diseases.

The sources of exposures to pesticides are multiple and difficult to evaluate. We are exposed to different doses of pesticides at different moments of our lives. It is difficult to predict when toxic effects of pesticides can manifest. We studied the effects of glyphosate on breast cancer cells with the support of BCUK. This was an important study because of the debates surrounding glyphosate carcinogenicity, but we only scratched the surface as dozens of pesticides are used in the UK6.

The development of breast cancer can be initiated in the womb by toxic exposures, but these are only detected after a few decades.

This is an incredibly complex topic.

The most reliable strategy to evaluate the adverse effects of pesticides in human populations is not to conduct animal studies, or survey food for pesticide residues, but to directly measure pesticide exposure by blood or urine screening. One of the few surveys performed in the US showed that high blood levels of the banned insecticide DDT predicted a 5-fold increased risk of breast cancer 7. Despite the worrying signs from this study, the presence of pesticides in the UK population has never been evaluated. There is an urgent need for human monitoring of pesticides.

Pesticide exposures are difficult to avoid. However, there is a lot we can do to reduce risks. Small actions, such as seeking information, or reconsidering the use of toxic chemicals in your house, may have significant consequences!

Written by Dr Robin Mesnage, who is a Research Associate in the Department of Medical and Molecular Genetics at King’s College London. He is a computational toxicologist whose main research interest focuses on understanding the effects of pollution on human health. He is also a consultant, providing expert advice on the risk assessment of pesticides. He is also a member of Breast Cancer UK’s Independent Scientific Review Panel.

Twitter: @Robin_Mesnage

Breast Cancer UK does not endorse any products or any opinions expressed by our guest bloggers.  The blogs are the personal opinions and endorsements of the blogger and not necessarily reflective of Breast Cancer UK views.  If you have questions about the blog, please contact


  1. Linhart C et al. (2021) Year-round pesticide contamination of public sites near intensively managed agricultural areas in South Tyrol. Environ Sci Eur 33, 1.
  2. Engel LS et al. (2017) Insecticide Use and Breast Cancer Risk among Farmers’ Wives in the Agricultural Health Study. Environ Health Perspect. 2017;125(9):097002.
  3. Curl CL et al. (2021) Measurement of urinary pesticide biomarkers among Latina farmworkers in southwestern Idaho. J Expo Sci Environ Epidemiol. doi:10.1038/s41370-020-00285-2.
  4. Perkins R et al. (2021) Potential role of veterinary flea products in widespread pesticide contamination of English rivers. Sci Total Environ. 755(Pt 1):143560.
  5. Mesnage R and Zaller JG, eds. Herbicides: Chemistry, Efficacy, Toxicology, and Environmental Impacts. Elsevier in cooperation with RTI Press. ISBN: 9780128236741.
  6. Mesnage , et al. (2017). Evaluation of estrogen receptor alpha activation by glyphosate-based herbicide constituents. Food Chem Toxicol. 2017 Oct;108(Pt A):30-42.
  7. Cohn BA et al. (2015). DDT Exposure in Utero and Breast Cancer. J Clin Endocrinol Metab. 100(8):2865-72.

For information about pesticides and breast cancer risk see our EDC brief here and for Breast Cancer UK’s position on organic food see here

Related Articles

14 June 2021

Animal tests are poor models for human diseases

It’s not only their track record in Breast Cancer research which puts Breast Cancer UK on the map, but also how they carry out their research, which has made it...

Read full story

13 June 2021

Our research: what do we fund and why we fund it

Breast Cancer UK funds animal-free research that explores the link between breast cancer and potentially harmful chemicals found in everyday products and the environment. This science blog explains why we...

Read full story

25 May 2021

UK Chemicals Strategy: a golden opportunity to strengthen public protections from harmful chemicals!

This month,  Breast Cancer UK joined with 26 Public Health and Environmental NGO's to call for actions that ensure the future UK Chemicals strategy delivers strong and effective public protections from harmful chemicals.  Strong chemical regulations are vital for our...

Read full story

10 March 2021

2020 – A challenging yet productive year for our research

While 2020 brought us many unexpected challenges, it also brought exciting developments! Initial results from the research you helped fund have identified new techniques that will improve investigations of bisphenols...

Read full story

A donation of just £10 can help us reach women with educational information and guidance on how they can reduce their chances of getting breast cancer.

Donate £10

A donation of £25 can help provide a Breast Cancer Prevention kit to help our Ambassadors deliver talks, providing healthy lifestyle advice and practical tips that can help people reduce their risk of breast cancer.

Donate £25

Your donation of £100 can help train one of our PhD students, who work on vital research which aims to understand the causes of breast cancer and identify risk factors.

Donate £100

Just want to help in some way? donate an amount that feels right for you

Start Your Donation

Donate Now

Make a Donation


My One Time Donation

I want to make a one time donation of

Thank you. You’re just a few steps away from completing your donation.

+25% with Gift Aid

If you are a UK taxpayer, the value of your gift can be increased by 25% under the Gift Aid scheme at no extra cost to you.

This means that your donation of £100.00 could be worth an extra £25.00 to us, and it doesn't cost you a penny!

My Monthly Donation

I want to make a monthly donation

You’re just a few steps away from completing your donation.

+25% with Gift Aid

If you are a UK taxpayer, the value of your gift can be increased by 25% under the Gift Aid scheme at no extra cost to you.

This means that your donation of £100.00 could be worth an extra £25.00 to us, and it doesn't cost you a penny!

One Time Donation Monthly Donation
Make a donation with Gift Aid

Gift Aid is reclaimed by the Breast Cancer UK from the tax that I pay for the current tax year. If I pay less Income Tax and/or Capital Gains Tax than the amount of Gift Aid claimed on all my donations, it is my responsibility to pay any difference. Breast Cancer UK will reclaim 25p in tax back for every £1 I donate.

Your payment details

Your donation amount

Donation Allocation (Optional)

Additional Comments (Optional)

Stay in Touch

We’d love to keep you posted on how your support can make a difference to Breast Cancer UK and the exciting ways you can support us in the future.

Please tick if you’re happy to receive information from us by:

By completing an online donation, your data will be handled in accordance with the Breast Cancer UK’s privacy policy, and the privacy policy of our payment processing supplier BBMS (a Blackbaud company).

Thank You Wall

If you donate over £50, as a way of saying thank you for your donation, we would like to feature your donation on our virtual thank you wall on our website.

Donations will only feature on the wall for up to two months depending on the level of donations we receive.

You must fill out all required fields before paying.


Need help making your donation?

If you need help to make a donation or have any questions about making one, please contact us…

Call 08456801322