Bisphenols are Endocrine Disrupting Chemicals (EDCs) that may interfere with our hormones. Bisphenol A (BPA) is the most well-known bisphenol, but there are at least 148 different types, such as bisphenol S (BPS), bisphenol F (BPF) and bisphenol AF (BPAF). These bisphenols are similar to BPA and can be used as substitutes. For this reason, they are also known as “regrettable replacements”, because they may have similar toxicity to BPA.
BPA and other bisphenols are used primarily to produce some types of plastic (polycarbonate, recycling code 7), which are used in packaging for food, drinks, cosmetics and beauty products. “BPA-free” plastic may not contain BPA but could contain any other bisphenol, such as BPS and BPF.
BPA is also used to produce epoxy resins, which can be used as internal linings in tins and cans. Bisphenols may also be used in thermal paper for till receipts.
Bisphenols can be transferred from plastic items into food, water, cosmetics and the environment. For instance, microwaving food in a plastic container may release bisphenols into the food.
Once in our bodies, these EDCs can be found in many body fluids and tissues, including blood, urine, amniotic fluid, breast milk, fat and breast tissues.
Studies in cells have shown that BPA can copy the actions of the female hormone oestrogen and interfere with the endocrine (hormone) system. High levels of oestrogen are known to increase breast cancer risk. Therefore, bisphenols that act in a similar way to oestrogen may play a role in breast cancer.
Studies in cells and animals have shown that BPA may contribute to breast cancer development and progression. In animals, exposure to BPA in the womb can also affect the development of the mammary gland and increase the risk of breast tumours later in life.
While there are many laboratory studies on BPA, very few studies have been done in humans and no direct link has been observed between exposure to BPA and breast cancer. However, these studies were conducted in adults without considering exposure during other life stages when we may be more susceptible to EDCs. Long-term human studies are needed to see if exposure to BPA during the development of the unborn baby in the womb may affect breast cancer risk later in life, as observed in animals.
BPA exposure may be harmful during pregnancy and may increase the risk of miscarriage, preterm birth and low birth weight. Exposure in the womb may also be linked to behavioural issues and obesity in children. BPA may also be associated with obesity in adults and being overweight post-menopause is a known breast cancer risk factor.
At least 34 bisphenols may interfere with hormones in a similar way to BPA, including copying the actions of oestrogen. Some “regrettable replacements” have also been shown to affect breast cancer progression in laboratory studies.
In humans, bisphenols, such as BPS and BPF, may have similar effects to BPA and may be linked to low birth weight and preterm birth.
BPA is officially recognised to be an EDC and to negatively affect human health. Therefore, BPA has been banned from baby feeding bottles, till receipts and restricted from children’s toys. Other bisphenols used as substitutes are currently not regulated, with the only proposal under current consideration in the UK looking at restricting bisphenols in till receipts.
As part of regulating chemicals, it is important to estimate safe levels of exposure. Recently, the EU has re-assessed the safe levels of BPA to which we can be exposed daily. After evaluating the most recent evidence available, including a study funded by Breast Cancer UK, a new safe limit has been proposed, which is 20,000 times lower than the previous one. If accepted, this new limit may in the future lead to more regulations on BPA.
Please see our Bisphenols and breast cancer science review for more details and references.
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