Popular head lice treatment contains chemical scientists say could increase breast cancer risk
Hundreds of chemicals used in cosmetics and food packaging could increase the risk of breast cancer, a wide-ranging study has found.
Among them is malathion, the active ingredient in the popular head lice treatment Derbac M, which can be used on children as young as six months.
Researchers warned that exposure to potentially harmful chemicals may begin years or even decades before breast cancer develops.
‘People are exposed to hundreds of chemicals from multiple sources throughout their lives, and these exposures add up,’ Dr Jennifer Kay, the study’s lead author said.
‘Breast cancer can take years to develop, so reducing exposure to potentially harmful chemicals early in life is an essential part of cancer prevention.’
Other potentially harmful chemicals highlighted in the study included Bisphenol A (BPA), which is used in drinks cans and till receipts, and methylparaben, a preservative found in moisturisers, shampoos and deodorants.
Researchers also flagged benzene, which people are commonly exposed to through exhaust fumes and cigarette smoke, and styrene, used in some takeaway coffee cups and food containers.
The findings – published in Environmental Health Perspectives – come amid a rise in breast cancer among younger women, with cases among 20 to 49-year-olds increasing by almost 10 per cent over the past decade.
To identify the biggest sources of exposure, researchers analysed more than a dozen US government databases covering chemical use, pollution levels and human exposure.
They focused on more than 900 chemicals previously identified as potentially linked to breast cancer, including substances that can disrupt hormones or have been shown to cause mammary tumours in animals.
Derbac M, a popular head lice treatment, contains malathion – a toxic chemical that has now been linked to breast cancer
The researchers found hundreds are still used in everyday products, from cosmetics and food packaging to building materials and medical equipment.
Among them was BPA, a chemical used in some reusable plastic food containers, the lining of drinks cans and till receipts.
It was banned from baby bottles in Britain in 2011 amid concerns it could leach into their contents.
The European Commission went further in December 2024, banning BPA from materials that come into contact with food. The UK has yet to follow suit.
Researchers also highlighted DEHP, a chemical used to soften plastics that can still be found in some medical equipment, as well as methylparaben, a preservative used to extend the shelf life of moisturisers, shampoos and deodorants.
Parabens can mimic the effects of oestrogen in the body – significant because the hormone can fuel the growth of some breast cancers.
However, several of the pesticides highlighted in the study are no longer approved for agricultural use in Britain.
Scientists said the findings expose a potential regulatory ‘blind spot’, because safety assessments often consider individual chemicals rather than the mixture of substances people may be exposed to in everyday life.
‘Breast cancer can take years to develop, so tracking and reducing people’s exposure to pesticides from multiple sources is an essential part of cancer prevention,’ said lead author Dr Jenifer Kay.
Around 59,000 women and 420 men are diagnosed with breast cancer in the UK each year.
There is no single cause of the disease, and the study does not prove that exposure to any one of the chemicals identified will lead to breast cancer.
However, a number of factors are already known to increase the risk, including getting older and having a family history of the disease
Drinking alcohol, smoking, being overweight, having dense breasts and exposure to certain hormones, including through HRT, are also linked to breast cancer.
