Where BPA is used
BPA is the foundational monomer for polycarbonate plastic (formerly common in baby bottles, hard reusable water bottles, sports equipment) and epoxy resin (the lining of nearly all metal food + beverage cans). It also appears in thermal receipt paper, dental sealants, and some medical devices. Heat, abrasion, and acidic foods accelerate BPA leaching from container into contents.
The endocrine disruptor mechanism
BPA binds to estrogen receptors (both nuclear ERα/ERβ and membrane GPR30) with ~10,000x lower affinity than 17β-estradiol — but at biologically relevant doses it acts as a partial agonist. Vandenberg et al. 2012 (Endocrine Reviews) reviewed over 1,000 studies and concluded BPA exhibits non-monotonic dose-response — meaning low doses can produce effects that high doses don't, a pattern that challenges the traditional toxicology assumption that "the dose makes the poison."
BPA-free is not the same as safe
After 2010-2012 regulatory pressure, many manufacturers replaced BPA with structural analogs — primarily BPS (bisphenol S) and BPF (bisphenol F). Rochester & Bolden 2015 (Environmental Health Perspectives) systematically reviewed the BPA-substitute literature and concluded the substitutes show estrogenic activity equivalent to or sometimes greater than BPA itself. The "BPA-free" label tells you BPA is absent; it does NOT tell you the product is endocrine-safe. For practical implications, see our complete BPA-free safety review.
How to reduce exposure
Avoid polycarbonate plastic (recycle code #7, often marked "PC"), don't microwave or dishwasher-heat plastic containers (heat accelerates leaching), choose glass/stainless/ceramic for food storage, and minimize canned food consumption when fresh/frozen alternatives are available. Receipt paper is a meaningful dermal exposure source — wash hands after handling.
Primary sources: Vandenberg et al. 2012 (Endocr Rev), Rochester & Bolden 2015 (Env Health Perspect), FDA Bisphenol A in food packaging communications, EU Regulation 2011/8/EU baby-bottle BPA ban.