Bisphenol compounds are found in many everyday products such as plastic bottles, food packaging and till receipts.
Exposure to bisphenol A (BPA) has been linked to increased breast cancer risk.
Due to restrictions on the use of BPA in certain products, other bisphenols, such as, BPS and BPF are being used as replacements. Many have structures like BPA and are likely to produce similar adverse effects.
Bisphenols may increase breast cancer risk by copying the actions of the natural hormone oestrogen, which helps tumours to grow and develop.
Several bisphenol compounds have been found in human bodily fluids such as urine, blood and breast milk; and in human tissues including breast, fat and liver tissues.
What are bisphenols?
Bisphenols are Endocrine Disrupting Chemicals (EDCs) which are compounds that can affect any aspect of hormone action.
The most common bisphenol compounds include bisphenol A, S, F and AF (BPA, BPS, BPF and BPAF). These bisphenols all have similar structures, meaning they may affect hormone action in the same or similar ways.
Bisphenol A (BPA) is the most commonly known EDC. This compound is used worldwide with demand continuing to rise.
Where are they found and how are we exposed?
Bisphenols are used primarily to form polycarbonate plastics which are used in the packaging of food, drink and various toiletries; and to form epoxy resins, which are used as can linings as well as in various coatings and adhesives.
Bisphenols are also present in thermal paper which is used for producing till receipts.
Bisphenols can leak from these items into food, consumer products and the environment in general. This can lead to unintentional exposure to humans. The most common way we are exposed to bisphenols is through the food we eat.
Bisphenol A and breast cancer
Bisphenols can copy the actions of the natural hormone oestrogen, which is part of the endocrine system. Lifetime exposure to high levels of oestrogen increases breast cancer risk and exposure to compounds that copy oestrogen can also increase risk.
Evidence suggests that a long-term, low-level exposure to environmental chemicals, including bisphenols, could increase breast cancer risk.
Numerous studies have shown BPA can make already established breast cancers progress more quickly, likely by copying the actions of oestrogen. This not only increases breast tumour size but also the possibility of metastasis (the development of secondary cancers away from where the cancer started).
BPA may contribute to breast cancer development. Studies have shown that exposure to BPA can promote characteristics of ductal carcinoma in situ (DCIS); an early form of breast cancer often seen before breast cancer becomes invasive.
Many of these results were seen in response to low concentrations of BPA. Importantly, these concentrations are similar to levels previously detected in the human body.
Bisphenol substitutes and breast cancer
Bisphenol substitutes such as BPS, BPF and BPAF have structures like BPA and are increasingly being used to replace BPA in many everyday products. The similarities in structure between some bisphenol substitutes would suggest they may have the same or similar harmful effects to BPA, including copying the actions of oestrogen.
Laboratory studies have shown that like BPA, bisphenol alternatives can increase the progression of established breast cancers.
Both BPS and BPF may also contribute to breast cancer development and have been shown to disrupt normal breast structures. Additionally, like BPA, BPS can also promote characteristics of DCIS.
Bisphenol mixtures and timing of exposures may influence breast cancer
Many previous studies have focused on the effects of single chemicals on breast cancer. However, numerous bisphenols and other EDCs are present in low concentrations in the environment.
Exposure to other EDCs in combination with bisphenols will likely promote greater harmful effects and potentially result in a further increased risk of breast cancer.
Of concern is the timing of bisphenol exposures. Studies suggest that critical exposure windows for these compounds include in utero (in the womb), which may promote breast cancer development during adulthood.
Bisphenols have been detected in the placenta, amniotic fluid and breast milk of pregnant women and nursing mothers which suggests infants are exposed to a variety of chemical pollutants both before and immediately after birth.
The effects of bisphenol exposures on breast cancer development are not fully understood
Despite the increase in research related to bisphenols, exactly how they may contribute to breast cancer development is still not well understood.
This is due in part to the focus of research on already established breast cancers and not how these compounds affect non-cancerous breast tissue and whether these changes can promote breast cancer development.
Long-term studies are required to determine the lifelong risk of exposure to bisphenols and other EDCs; particularly the effects they have in the womb and whether this may influence breast cancer risk during adulthood.
Bisphenol regulation
Reports that BPA could potentially negatively affect human health led to restrictions on BPA’s use in some products. These include infant feeding bottles, children’s toys and more recently, paper till receipts.
All other bisphenol compounds are currently unregulated in the UK despite their increased use. The EU’s European Chemical Agency has classified BPA, BPB and another bisphenol (2,2-bis (4’-hydroxyphenyl)-4-methylpentane) as Substances of Very High Concern and is currently considering restricting the use of 30 bisphenols as a group, due to their potential hormonal or toxic effects on the reproductive system.
The UK government has chosen to evaluate bisphenol use in thermal paper as one of their top five priorities for 2022-2023 UK REACH (registration, evaluation, authorisation and restriction of chemicals) programme.
See our science brief on bisphenols for more information
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