BPA, or bisphenol A, is a synthetic chemical used to make hard, clear polycarbonate plastic and the epoxy resin linings inside metal cans. It has been produced in large quantities since the 1960s and shows up in products ranging from water bottles and food containers to eyewear and shatterproof windows. The reason BPA draws so much attention is that it mimics estrogen in the body, potentially interfering with hormones even at low levels of exposure.
Where BPA Shows Up
Polycarbonate plastic is the most recognized source of BPA. This is the rigid, transparent plastic used in reusable water bottles, food storage containers, and some baby bottles (though many countries have banned BPA in infant products). You can sometimes identify it by the recycling code stamped on the bottom: plastics marked with code 3 or 7 may contain BPA, though not all of them do.
The other major source is epoxy resin, a coating applied to the inside of metal food and beverage cans. That thin lining prevents the metal from corroding or reacting with food. A Canadian Food Inspection Agency survey of 402 canned food samples found BPA in 41% of them, including canned fish, fruit, meat, and vegetables. The chemical migrates from the lining into the food, especially during high-heat processing like canning.
BPA also turns up in places most people don’t expect. Thermal paper, the shiny paper used for store receipts, ATM slips, and parking tickets, contains high concentrations of free BPA that transfers directly to your skin on contact. One estimate found that rubbing a receipt five times between your fingers and thumb can transfer roughly 30 micrograms of BPA onto the skin. About 0.17 micrograms can penetrate into the skin within two hours of contact and can’t be washed off with water. Cashiers who handle receipts all day show measurably higher BPA levels: one U.S. study found pregnant cashiers had urinary BPA concentrations of 2.8 micrograms per gram, compared to 1.8 for teachers and 1.2 for industrial workers.
How BPA Gets Into Your Body
The primary route is ingestion. Small amounts of BPA leach from plastic containers and can linings into food and drinks. Two factors accelerate this process more than anything else: heat and time. A study measuring BPA release from plastic bottles found that storage at room temperature (25°C) produced BPA levels up to 22.6 nanograms per liter, while heating to 70°C pushed levels as high as 38.9 nanograms per liter. Longer storage also increases leaching, though the rate slows after about four weeks as the most accessible BPA migrates out first.
This is why common advice includes not microwaving plastic containers, not leaving water bottles in a hot car, and not putting polycarbonate items in the dishwasher. Acidic foods may also accelerate leaching, though temperature and duration are the dominant factors.
Skin absorption is the other pathway, primarily from handling thermal paper. BPA on receipt paper exists in free form, meaning it isn’t locked into a polymer the way it is in hard plastic. It transfers on contact and penetrates the skin, entering the bloodstream directly.
Why BPA Concerns Scientists
BPA is classified as an endocrine disruptor because its chemical shape closely resembles estradiol, the body’s primary form of estrogen. It binds to the same receptors that estrogen uses, fitting into the receptor’s binding pocket in a similar orientation. The key difference is that BPA binds more weakly. It makes fewer stabilizing contacts with the receptor (42 versus 51 for natural estrogen) and fails to lock the receptor into its fully active shape. The result is that BPA acts as a weak, partial activator of estrogen signaling, enough to interfere with the system but not strong enough to replicate what natural estrogen does.
This partial activation is what makes BPA disruptive rather than simply adding to normal estrogen activity. It can trigger some estrogen-driven processes at the wrong time or in the wrong tissue, while simultaneously blocking the receptor from responding properly to the body’s own hormones.
Health Effects Linked to BPA Exposure
The strongest evidence for BPA’s health effects comes from animal studies and, increasingly, from human epidemiological data. The concerns span several body systems.
In female reproductive health, animal studies have documented ovarian cysts, problems with egg cell maturation, altered menstrual cycle length, earlier onset of puberty markers, reduced litter sizes, and changes to uterine lining cell growth. Mammary gland development is also affected, with earlier onset of breast tissue growth and altered ratios of cell proliferation to cell death.
In males, BPA exposure has been linked to effects on testicular and prostate tissue. Studies using advanced protein analysis consistently found that BPA affected both organs regardless of when during development the exposure occurred. Reductions in live offspring per litter may stem in part from male reproductive effects.
On the metabolic side, low-level prenatal BPA exposure has been associated with greater weight gain in young offspring, a finding that has fueled research into whether early chemical exposures contribute to the rising rates of obesity and diabetes. BPA influences how fat cells develop and differentiate, providing a plausible biological mechanism for these observations.
What Regulators Say
Regulatory agencies disagree sharply on BPA’s safety, which can be confusing if you’re trying to figure out how worried to be.
The U.S. FDA maintains that BPA is safe at current exposure levels from food packaging, citing its own research showing no effects from low-dose exposure. The agency has not revised its safety assessment, though its most recent public statement on this dates to 2018.
The European Food Safety Authority took a dramatically different position in 2023. After a comprehensive reassessment, EFSA lowered its tolerable daily intake for BPA to 0.2 nanograms per kilogram of body weight per day. That is 20,000 times lower than its previous temporary limit of 4 micrograms per kilogram per day. EFSA concluded that BPA in food is a health risk at current exposure levels, putting it in direct tension with the FDA’s position.
The Problem With “BPA-Free”
When manufacturers removed BPA from products in response to consumer pressure, they typically replaced it with chemically similar compounds: bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF) are the most common substitutes. A product labeled “BPA-free” almost certainly still contains one of these alternatives.
The trouble is that these substitutes share BPA’s basic chemical structure and, increasingly, appear to share its problems. Research has found that BPA analogues exhibit comparable toxicological profiles, including estrogenic activity, the ability to damage DNA, and developmental toxicity. BPS is now detected in nearly 100% of thermal paper receipt samples tested. These compounds are showing up across environmental samples at rising levels, raising the concern that the switch from BPA to its cousins may not have reduced actual risk, just changed which specific bisphenol people are exposed to.
Reducing Your Exposure
You can meaningfully lower your BPA intake with a few practical changes. Use glass, stainless steel, or ceramic containers for food storage, especially for hot foods and liquids. If you use plastic containers, avoid heating them in the microwave or dishwasher. Choose fresh or frozen foods over canned when possible, since can linings remain a significant source. Decline paper receipts or handle them briefly and wash your hands afterward, particularly before eating. When buying plastic products, look for recycling codes 1, 2, 4, or 5, which are made from plastics that don’t use bisphenols in their production.