BPA, short for bisphenol A, is a synthetic chemical used to make hard, clear plastics and the protective linings inside metal cans. It is produced in enormous quantities worldwide and shows up in a surprising range of everyday products, from water bottles to store receipts. The reason BPA gets so much attention is that it mimics estrogen in the body, potentially disrupting hormones even at very low levels of exposure.
Where BPA Is Found
BPA is a building block of polycarbonate plastic, the tough, transparent material used in reusable water bottles, food storage containers, shatterproof windows, and eyewear lenses. It is also a key ingredient in epoxy resins, which form the thin coating on the inside of metal food cans, bottle tops, and some water supply pipes. That coating keeps the metal from corroding and prevents food from picking up a metallic taste, but it also means BPA can leach into whatever the container holds.
Thermal paper is another major source most people overlook. The paper used for cash register receipts, airline boarding passes, and train tickets contains milligrams of unbound BPA per gram of paper, applied directly to the printing surface. Unlike BPA locked into hard plastic, the BPA on receipts sits on the surface and transfers easily to skin. Workers who handle receipts regularly, such as cashiers, show roughly triple the urinary BPA levels after a shift compared to before.
Polycarbonate plastics are typically marked with the recycling code #7. Not every #7 plastic contains BPA, but it is the most common code associated with it. Plastics labeled #1, #2, #4, and #5 generally do not contain BPA.
How BPA Affects Your Hormones
BPA is classified as an endocrine-disrupting chemical because its molecular shape closely resembles estradiol, the body’s primary form of estrogen. That resemblance lets BPA bind to estrogen receptors on cells, essentially tricking the body into responding as though real estrogen were present. The binding is weaker than actual estrogen, but because BPA exposure is so widespread, the cumulative effect concerns researchers.
Beyond the main estrogen receptors, BPA also activates other hormone-related pathways, including membrane receptors on cells and a receptor called ERR-gamma that binds BPA strongly. This means BPA can influence a broader range of hormone signaling than a simple estrogen mimic would. It can interfere with the binding of your natural hormones to their receptors and, at the same time, exaggerate estrogen-driven effects in cells throughout the body.
Health Risks Linked to BPA Exposure
Ongoing exposure to BPA has been associated with a range of health problems: obesity, type 2 diabetes, reproductive disorders, cardiovascular disease, chronic kidney disease, and certain cancers. Animal studies and human epidemiological data both point in the same direction. BPA can stimulate hormone-driven effects in cells, damage DNA, alter the chemical tags that control gene activity (epigenetic changes), and disrupt the energy-producing structures inside cells.
Prenatal exposure is especially concerning. A review of human epidemiological studies found that 80% of the papers examined showed a correlation between BPA exposure during pregnancy and behavioral issues in offspring. Male infants exposed during the third trimester appeared to face a heightened risk. The developing brain and reproductive system are particularly sensitive to hormone signals, so even small disruptions during critical windows can have outsized effects.
How Much Is Considered Safe
Safety thresholds have shifted dramatically in recent years. In 2015, the European Food Safety Authority set the tolerable daily intake at 50 micrograms per kilogram of body weight per day. By April 2023, after re-evaluating the evidence, EFSA slashed that limit to just 4 micrograms per kilogram of body weight per day. That 12-fold reduction reflects growing confidence that BPA causes harm at much lower doses than previously assumed. The U.S. FDA has been in ongoing discussions with EFSA about the updated assessment but has not yet matched the European threshold.
Why “BPA-Free” Labels Can Be Misleading
As concern over BPA grew, manufacturers began replacing it with structurally similar chemicals, most commonly bisphenol S (BPS) and bisphenol F (BPF). Products made with these substitutes carry “BPA-free” labels, which many consumers interpret as safer. The evidence tells a different story.
A systematic review that directly compared the hormonal activity of BPS and BPF to BPA found their potency to be in the same order of magnitude. BPF’s average estrogenic potency was essentially equal to BPA’s, and in some assays it was more potent. BPS was somewhat weaker on average but still showed meaningful estrogenic, antiestrogenic, androgenic, and antiandrogenic activity. Because these substitutes have similar structures, similar metabolism in the body, and similar mechanisms of action, researchers conclude they likely pose similar health hazards. A “BPA-free” label, in other words, does not necessarily mean “hormone-disruptor-free.”
Practical Ways to Reduce Exposure
Diet is the primary route of BPA exposure for most people, mainly through canned foods and beverages stored in polycarbonate containers. In one dietary intervention study, participants who ate only fresh foods and avoided canned or plastic-packaged items for just three days saw a 66% drop in urinary BPA levels. A less strict “real-world” approach, where participants simply reduced their use of canned and heavily processed foods without eliminating them entirely, produced a similar reduction of roughly 60%.
A few straightforward changes make the biggest difference:
- Choose fresh or frozen over canned. Canned soups, vegetables, and beverages are among the top dietary sources of BPA because of the epoxy lining.
- Use glass, stainless steel, or #5 plastic containers for food storage and drinks, especially for anything hot. Heat accelerates BPA leaching.
- Decline paper receipts when possible, or wash your hands after handling them. Avoid using hand sanitizer immediately before touching thermal paper, as alcohol-based sanitizers increase BPA absorption through the skin.
- Don’t assume “BPA-free” means safe. Look for products that specify they are free of all bisphenols, or stick with glass and stainless steel when you can.
Because BPA clears from the body relatively quickly, with a half-life of about six hours, even short-term changes in habits produce measurable drops in exposure. The challenge is that BPA is so ubiquitous that maintaining low levels requires consistent choices rather than a one-time switch.