Bisphenol A (BPA) is a synthetic organic compound primarily used in the production of polycarbonate plastics and epoxy resins, forming clear, rigid plastics found in countless consumer products. However, BPA is classified as an Endocrine Disrupting Chemical (EDC) because it interferes with the body’s natural hormone system. This chemical acts as a xenoestrogen, mimicking the action of the natural female hormone, estrogen, and disrupting normal biological signaling pathways.
How BPA Acts as an Estrogen Mimic
The issue with BPA stems from its structural similarity to 17β-estradiol (E2), the body’s most potent natural estrogen. This molecular mimicry allows BPA to bind to estrogen receptors (ERs), specifically Estrogen Receptor-alpha (ER-α) and Estrogen Receptor-beta (ER-β), which mediate estrogen signaling throughout the body. When BPA binds to these nuclear receptors, it can either activate them (agonist activity) or block the natural hormone from binding (antagonist activity).
Although BPA’s binding affinity is thousands of times weaker than E2, its widespread presence and chronic low-dose exposure allow it to exert biological effects. BPA can also engage in non-genomic signaling by activating membrane-bound receptors, such as the G Protein-coupled Estrogen Receptor (GPER). This activation of both classical and non-classical estrogen pathways results in altered gene expression and cell function in hormone-sensitive tissues. Studies suggest BPA acts as an agonist on ER-α but may function as an antagonist on ER-β, leading to an unbalanced disruption of hormonal regulation.
Major Sources of Human Exposure
The primary route of human exposure to BPA is through the diet, as the chemical is incorporated into materials contacting food and beverages. Polycarbonate plastics (recycling code 7) are used for items like reusable water bottles, food storage containers, and tableware. Another major source is the epoxy resin used to line the inside of most metal food and beverage cans to prevent corrosion.
BPA leaches from these materials into the contents, a process accelerated by heat, such as microwaving, or by contact with fatty or acidic foods. Even under normal conditions, the chemical can migrate from the packaging into the food over time. A significant non-dietary source is thermal paper, used for cash register receipts and tickets. Direct skin contact with these receipts can lead to absorption, and other sources include dental sealants and contaminated house dust.
Health Implications of Endocrine Disruption
The hormone-mimicking activity of BPA is concerning because the endocrine system regulates nearly every bodily process, with the greatest vulnerability occurring during developmental periods. Exposure to BPA is linked to adverse reproductive and developmental outcomes in both sexes. In women, this includes impacts on ovarian function, fertility, and an association with polycystic ovary syndrome (PCOS).
In males, BPA exposure is associated with decreased sperm production and quality. For children, prenatal and early life exposure is linked to altered fetal growth and the timing of puberty. BPA’s interference also extends to metabolic health, where it is associated with insulin resistance, Type 2 diabetes, and obesity.
The chemical can also affect the nervous system, as natural hormones play a foundational role in brain development. Studies suggest that BPA exposure is linked to adverse neurodevelopmental and behavioral outcomes, especially during critical windows of gestation. This includes impacts on brain structure, memory function, and the regulation of behavior. Because BPA’s mechanism involves epigenetic changes, the effects of early exposure may be long-term and potentially transgenerational.
Practical Steps to Reduce Exposure
Reducing daily exposure to BPA involves simple changes in how food is stored and prepared. Minimize the use of polycarbonate plastic containers for food, opting instead for alternatives made of glass, stainless steel, or porcelain. Avoid heating food or beverages in plastic containers, including microwaving, as warmth significantly increases the rate at which BPA leaches into the contents.
Limiting the consumption of canned foods also reduces exposure, as the epoxy lining is a major dietary source. Choose fresh, frozen, or food packaged in glass jars or cartons whenever possible. Since thermal receipts are a non-dietary source, decline receipts when possible and wash hands after handling them, especially before preparing food. These steps help lower the body burden of BPA for vulnerable populations.