Does a chemical found in weedkiller cause lymphoma?

In summary: There’s been lots of controversy in the media about whether using RoundUp and other weedkillers containing glyphosate increase lymphoma risk.

There has been a lot of disagreement about the scientific evidence, with different organisations taking views on whether it increases risk. But the leading authority, the International Agency for Research on Cancer (IARC), has decided it probably does increase risk and so people who want to take a precautionary approach should avoid using it. Those who choose to continue using it should make sure they follow the safety instructions.

For a number of years there has been concern about a potential link between glyphosate (the active ingredient in many weed killers, including RoundUp) and cancer. This received widespread media coverage in 2018 when a US court found in favour of a man who claimed Roundup had caused his non-Hodgkin lymphoma. Thousands of other legal claims followed, and in June 2020 glyphosate’s manufacturer, which continues to argue that glyphosate does not cause cancer, announced it would make payments of over $10bn to settle current and future legal cases.

In 2015, IARC published a detailed report[i] on glyphosate and other chemicals, based on a review of about 1,000 studies. Some of the studies looked at people exposed through their jobs, such as farmers, while others were laboratory studies.

The report found that glyphosate is “probably carcinogenic to humans”. This was based on “limited” evidence in humans (from real-world exposures) and “sufficient” evidence of cancer in laboratory experiments with animals (from studies of “pure” glyphosate).

Also in 2015, the European Union’s European Food Safety Authority (EFSA) examined many of the same published studies and came to the opposite conclusion, finding that ‘glyphosate is unlikely to pose a carcinogenic risk to humans’[ii]. The EFSA judged that existing studies did not show a link between glyphosate and cancer, and decided that a study showing a link was invalid.

The IARC report led to legal action from people with lymphoma who had used large amounts of glyphosate in their work. This included a high-profile legal case in California that found in favour or the claimant and against RoundUp’s manufacturer.

Governments have reacted to the evidence in different ways. In the UK there are currently no plans for a national ban, but some local authorities have stopped or restricted use, and there have been calls for a ban from some trades unions and other organisations. In 2017, the European Union said glyphosate weed killers could be sold for the next five years (the evidence will then be assessed again)[iii], but a number of EU countries plan to introduce bans or have already done so.

Our view is that IARC is the leading authority on what affects our risk of cancer, and so we should take seriously its view that glyphosate increases lymphoma risk . So while there is a lack of consensus, people who want to take a precautionary approach should avoid using it, and those who decide to continue using it should take careful safety precautions.

In the UK employers are legally obliged to protect their employees from exposure to hazardous substances in the workplace. If you are worried about using glyphosate as part of your work then you should talk to your employer. The Health and Safety Executive provides information on the Control of Substances Hazardous to Health (COSHH)[iv], and the Trades Union Congress (TUC) has produced a statement on glyphosate and the legal obligations of employers[v].

Home gardeners who use weed killers will normally use much smaller amounts than professionals, but are less used to handling hazardous chemicals and may be less aware of the importance of preventing exposure. All weed killers sold for use by home gardeners, list their ingredients and come with warning labels about how they should be used. If you choose to use weed killers it is really important that you follow these carefully.

If you have used these weedkillers occasionally in the past, any increase to your risk of getting cancer is likely to be small.

If you are concerned about any aspect of your health, we’d recommend speaking to your GP in the first instance. If you'd like to talk through any of the contents of this information, please do contact our Support Services Team on 0808 2080 888 or email [email protected].

[i] IARC monograph on glyphosphate, “featured new”, accessed 27 September 2019: https://www.iarc.fr/featured-news/media-centre-iarc-news-glyphosate/

[ii] European Food Safety Agency, Glyphosphate, accessed 27 September 2019: https://www.efsa.europa.eu/en/topics/topic/glyphosate

[iii] European Union, “current status of glyphosphate in the EU”, accessed 27 September 2019: https://ec.europa.eu/food/plant/pesticides/glyphosate_en

[iv] Health and Safety Executive, COSHH Basics, accessed 27 September 2019: http://www.hse.gov.uk/coshh/basics.htm

[v] TUC statement on Glyphosphate, accessed 27 September 2019: https://www.tuc.org.uk/research-analysis/reports/glyphosate