3 years ago
One recent research project we have co-funded investigated whether UV filters (used in many sunscreens) were present in human breast tissue.
We asked Professor Philippa Darbre, who led the research, to explain why this research is so important.
PD – UV stands for ‘Ultraviolet’ – and UV filters are chemicals used as protection against harmful damage caused by UV light. There are around 50 different types of chemical UV filters. As you’d expect, they’re used widely in sunscreen creams, in order to protect skin from damage by UV light, which can lead to skin cancer. But they may also be added to other personal care products, such as moisturisers, to increase product stability, or incorporated into textiles, marketed as UV protective clothing. For those interested in the long chemical names for these things, the most commonly used UV filters include benzophenones (e.g. benzophenone-3 or BP-3), octylmethoxycinnamate (OMC), 4-methylbenzilidenecamphor (4-MBC), homosalate (HS) and octocrylene (OCT).
PD – Unfortunately not, these chemicals do not break down easily or disappear quickly once washed off. In fact, due to their widespread use in consumer products – notably sunscreens – they are increasingly found in the environment, for example in water, soil and tissues of aquatic organisms (1).
Also, studies have shown that these chemicals are rapidly absorbed by the skin and can be measured at increased levels in blood just one hour after applying to skin (2). These and other UV filters have been identified in a range of human body fluids and tissues including urine, placenta, breast milk and most recently, in human breast tissue (3). So they’re not easily removed from the body either.
PD – The problem is that UV filters are known to be endocrine disrupting chemicals or EDCs, which can mimic natural oestrogen found in our bodies. Lifetime exposure to oestrogen is an established risk factor for breast cancer.
The UV filters, BP-3, OMC, 4-MBC, HS and OCT are known EDCs and all possess oestrogenic properties. In separate studies, they have been shown to increase the growth of oestrogen-responsive human breast cancer cells, when cultured under laboratory conditions (4, 5).
Furthermore, at levels we recently detected in human breast tissue, BP-3, OMC and 4-MBC can increase proliferation, migration and invasive properties of human breast cancer cells grown in cell culture (6, 7). This implies a potential for these UV filters to increase tumour spread. This is especially relevant for breast cancer, where tumour spread is the main cause of mortality.
PD – Our recent work investigated whether 4 commonly used UV filters were present in breast tissue from 40 women who’d undergone mastectomies as a result of breast cancer diagnosis. We took measurements in 3 different locations across the breast to see if they were more heavily distributed at specific sites where breast cancer is most common. We found one or more UV filters were measurable in 84% of tissue samples and in at least one breast region for 95% of the women. Specifically, BP-3 was measured in 69% of the tissue samples and OMC was measured in 74% of them. 4-MBC was detected less often – in only 13% of samples. We did not detect HS in any of the tissue samples. All of these UV filters have been shown to be oestrogenic and their presence in human breast tissue suggests a potential for them to influence breast cancer development.
PD – People should take steps to avoid excessive exposure of skin to UV rays from sunlight or elsewhere but there are ways of doing this other than just covering our bodies with these chemicals. It’s best to avoid the sun when it’s at its hottest, cover up using a hat and cool long sleeves etc. However, if you are unable to cover up, you could consider using an old-fashioned zinc oxide based sunscreen which many organic cosmetics companies market.
It would seem unlikely that occasional holiday use of chemical UV filters in sunscreen would cause serious harm because studies of applying to skin show not only that the chemicals are absorbed within 1 hour but also that they are largely cleared after 24 hours. However, more and more products that are not primarily sunscreens now contain UV filters – to protect the product rather than the user. This means that we may all be exposed to these chemicals every day without realising it. The oestrogenic activity of UV filters and their identification in breast tissue suggest they may have the potential to influence breast cancer development, so their regular use –from application of a personal care product such as moisturiser or wearing impregnated clothing – should be avoided.
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