Pesticides are chemicals used to control any type of pest, such as weeds (weed killers, or herbicides), insects (insecticides), and fungi (fungicides).
There are about 420 pesticides authorised in the UK that can be used in farming to grow crops; by local authorities in residential areas; or by the public to treat gardens and patios.
If you work directly with pesticides you can be exposed to high levels. This is known as occupational exposure and covers anything from producing pesticides in factories to using them in agricultural fields.
You can also be exposed to pesticides through your diet or when they are used in residential areas, such as when your local authority sprays them near your home. These exposures may involve low levels of pesticides but for prolonged periods.
In addition to authorised pesticides, you may also be exposed to some that are banned (for example, DDT) as these can remain in the environment for a long time and may accumulate in our bodies.
In 2023, about 48% of the food analysed in the UK contained at least one pesticide residue. Whilst only 1% of the samples had levels above the Maximum Residue Level (MRL), 33% of the food contained more than one pesticide.
The MRL is the highest level of a certain pesticide allowed in food that doesn’t cause a harmful effect. However, the MRL doesn’t consider the cocktail effect. When multiple pesticides are present, their effects may be added together and this cocktail may be harmful even if each pesticide is below the MRL. According to PAN UK’s “Dirty Dozen list,” citrus fruits, strawberries, and grapes are the most likely to contain more than one pesticide.
Pesticides may cause cancer to develop by damaging the DNA or acting as Endocrine Disrupting Chemicals (EDCs). Some pesticides have also been internationally classified as “probably carcinogenic” to humans, which means that there is some strong evidence that they can cause cancer.
Others are classified as “possible carcinogens”, as the available evidence is not as strong but still suggests a link to cancer. However, this classification has so far only looked at a fraction of all the pesticides authorised in the UK.
Glyphosate is the most used weed killer globally, representing 92% of all herbicides used. In the UK, glyphosate is used in all applications, from farming to residential areas. It is classified as a probable human carcinogen and may cause DNA damage, disrupt sex hormones and interfere with the development of the mammary gland in animals. These harmful effects suggest that glyphosate may play a role in breast cancer, but the evidence from human studies is limited.
Most studies found that working or being in close contact with pesticides may increase your breast cancer risk, particularly for banned pesticides. Whilst in these studies exposure was largely assessed by asking participants about their pesticide use, other studies have also found that having high levels of these chemicals in the body may also be linked to breast cancer.
Among the pesticides currently in use, limited evidence suggests that exposure to imazalil (used to treat citrus fruit) or glyphosate may increase risk. However, not all studies have found a link between pesticides and breast cancer and research on dietary exposure is very limited.
Studies on DDT, which is banned but still present in the environment, are largely inconclusive when considering exposure in adults. However, exposure during pregnancy can affect the unborn baby‘s development and increase the daughter’s breast cancer risk later in life.
An increased risk was also observed for women who were exposed to DDT during childhood. Therefore, exposure to pesticides during certain life stages may have different effects on breast cancer risk.
Yes, swapping conventionally grown food with organic products can reduce pesticide exposure by about 90%. This is because organic food is much less likely to contain pesticides and, when they are found, they are generally below their MRLs and rarely include multiple residues.
Some studies showed that a diet rich in organic food may reduce breast cancer risk, especially post-menopause. However, a large UK study found no link between organic food and reduced risk.
Overall, there is some evidence that organic food may have health benefits. However, this could also be because people with an organic diet also tend to be more physically active and have different eating habits.
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