Bisphenol A (BPA) is a chemical used in the manufacture of certain plastics and epoxy resins, including some food and beverage containers. In an early population study published in JAMA using NHANES data, higher urinary BPA levels were associated with increased prevalence of cardiovascular disease, diabetes, and elevated liver enzymes. While this study could not establish causation, it helped raise early concerns about BPA as a potential endocrine disruptor. Subsequent research has expanded this discussion to include BPA substitutes (such as BPS and BPF) and broader effects on metabolic and hormonal regulation.