Bisphenol A (BPA) is an industrial chemical used primarily in the production of polycarbonate plastics and epoxy resins. It is a high-volume compound found in countless products, leading to its widespread presence in the environment and human population. This chemical is used to create hard, clear plastics and to line metal food and beverage cans to prevent corrosion. Understanding the extent of human exposure to BPA is a central concern for public health.
Measuring Widespread Exposure
The Centers for Disease Control and Prevention (CDC) uses the National Health and Nutrition Examination Survey (NHANES) to monitor environmental chemical exposure in the U.S. population. This survey utilizes urine samples to measure the presence of Bisphenol A, as the body quickly metabolizes and excretes the chemical. Based on NHANES data, an estimated 93% of Americans aged six years and older have detectable levels of BPA in their urine.
More recent NHANES data from 2013–2014 show a detection frequency of approximately 95.7% in urine samples, indicating continuous and near-universal exposure. The fact that BPA is detected so frequently, despite having a relatively short half-life of a few hours, suggests that exposure is regular and ongoing. The measurement of BPA in urine reflects recent exposure. However, some research suggests that BPA levels do not decline as quickly as once thought in fasting individuals, which may indicate non-food exposures or accumulation in fatty tissues.
Common Sources of BPA
For most people, the primary source of BPA exposure is through the diet. The chemical can leach into food and beverages from the epoxy resin coatings used to line the inside of metal food and drink cans. Additionally, polycarbonate plastics, often marked with the recycling code 7, are used in items like reusable water bottles, food storage containers, and certain tableware, providing another route of ingestion.
Beyond food packaging, a significant non-food source of exposure is thermal paper, commonly used for cash register receipts, airline tickets, and labels. Direct contact with these papers allows the chemical to be absorbed through the skin. The rate at which BPA leaches from plastics increases substantially when the material is subjected to heat, such as when food is microwaved in a plastic container or when hot liquids are placed in polycarbonate bottles.
Biological Significance of Traceable Levels
The widespread presence of traceable BPA levels is a concern because the chemical functions as an endocrine-disrupting chemical (EDC). BPA is classified as a xenoestrogen, meaning its structure is similar enough to the natural hormone estradiol to allow it to bind to and activate the body’s estrogen receptors. By mimicking estrogen, BPA can interfere with the body’s complex hormonal signaling pathways. The chemical can also act as an anti-androgen, blocking the normal actions of male hormones.
This hormonal interference can potentially affect various biological processes. Research indicates that early-life exposure to endocrine-disrupting chemicals may alter developmental trajectories, leading to health issues later in life. Low-dose BPA exposure has been associated with effects on reproductive health, brain development, and metabolic disorders like type 2 diabetes and heart disease in adults.
Practical Steps for Lowering Exposure
Given that food and consumer products are the main exposure routes, simple changes can help reduce the amount of BPA entering the body. Reduce the consumption of canned foods, opting instead for fresh, frozen, or dried alternatives. If canned items are necessary, choosing products specifically labeled as “BPA-free” may help.
Consumers should avoid heating food in plastic containers, especially in the microwave, since elevated temperatures increase the rate at which BPA leaches into the contents. Replacing plastic food storage with alternatives like glass, porcelain, or stainless steel is a practical step, particularly for hot foods and liquids. Minimizing contact with thermal paper receipts and washing hands after handling them can also decrease dermal absorption of the chemical.