Bisphenol A (BPA) is a high-volume industrial chemical used primarily in the production of polycarbonate plastics and epoxy resins. This synthetic compound has become ubiquitous, and human exposure is widespread. Testosterone is a steroid hormone that plays a multifaceted role in human health, regulating male reproductive development, muscle mass, bone density, and mood. The presence of a common chemical like BPA, which is structurally similar to certain hormones, raises questions about its potential to interfere with the body’s natural testosterone balance. This article examines the scientific findings regarding the relationship between BPA exposure and changes in testosterone levels.
Scientific Evidence Linking BPA to Testosterone Decline
Epidemiological studies involving human populations have provided various findings regarding the association between BPA exposure and circulating testosterone levels. One key study on male chemical plant workers with chronic, high-level occupational exposure found a statistically significant link to reduced levels of free testosterone in their blood compared to control groups. Free testosterone is the biologically active form of the hormone.
Other large-scale human studies, however, have yielded mixed or contrasting results, with some finding an association between higher BPA exposure and a small increase in testosterone levels in men from the general population. These inconsistencies likely reflect differences in the study population’s age, sex, overall health, and the varying levels and duration of chemical exposure. Studies focused on the general population with lower, environmental-level exposure have shown associations between BPA and decreased total testosterone in specific groups, such as overweight men.
Animal models have provided more direct evidence of a negative impact on male hormones. Studies on adult male rats have shown that exposure to BPA can lead to a decrease in circulating testosterone, often accompanied by reduced sperm quality and count. This effect on testosterone has been observed across various animal species, and the strongest evidence points to a disruption of the male reproductive system, particularly in high-exposure or developmental-stage scenarios.
How BPA Acts as an Endocrine Disruptor
BPA is classified as an Endocrine-Disrupting Chemical (EDC) because its molecular structure allows it to interfere with the body’s endocrine (hormone) system. The chemical can mimic natural hormones, specifically estrogens, due to its similar shape, allowing it to bind to estrogen receptors (ERs) in various tissues. This estrogenic activity is a primary way BPA can disrupt the delicate hormonal balance in both sexes.
In males, BPA directly targets the Leydig cells in the testes, which are responsible for producing testosterone. BPA can interfere with the Hypothalamic-Pituitary-Gonadal (HPG) axis, the complex signaling pathway that regulates testosterone synthesis. Specifically, BPA has been shown to block or antagonize the androgen receptor, which is the receptor that testosterone uses to signal its effects, effectively reducing the body’s response to the hormone.
BPA also affects the production process of testosterone, known as steroidogenesis, within the Leydig cells. It can interfere with steroidogenic enzymes like CYP11A1, which is necessary for the initial conversion of cholesterol into precursors for testosterone. Furthermore, BPA has been linked to the activation of the aromatase enzyme (CYP19), which converts testosterone directly into estradiol (a form of estrogen). This dual action—reducing production precursors and accelerating conversion to estrogen—can lead to a net decrease in functional testosterone and an altered sex hormone ratio.
Primary Sources of Public Exposure
The primary way the general population is exposed to Bisphenol A is through the diet, as the chemical leaches into food and beverages from packaging materials. BPA is an ingredient in the epoxy resins used to line the inside of nearly all metal food and beverage cans. This internal coating prevents corrosion and spoilage, but the chemical can migrate from the lining into the contents, especially when the food is acidic, fatty, or heated during the canning process.
Another significant source is polycarbonate plastic, a hard, clear plastic used to make reusable water bottles, food storage containers, and some tableware. When exposed to high temperatures, this plastic can break down and release BPA into the liquid or food it contains. The degree of leaching increases notably when these containers are microwaved or cleaned with harsh detergents.
BPA exposure also occurs through non-dietary routes, most notably via thermal paper receipts. This type of paper, commonly used for cash registers and ATM slips, is coated with a layer that includes BPA, which can be absorbed through the skin when handled. While food and drink are the main contributors to overall intake, these other sources contribute to the chronic, low-dose exposure characteristic of modern life.
Practical Steps to Minimize BPA Contact
Reducing daily contact with Bisphenol A begins with making intentional choices about food storage and consumption. One of the most effective steps is to limit the consumption of canned foods and beverages, as the epoxy lining is a major source of exposure. Prioritizing fresh or frozen alternatives over canned goods can significantly reduce this dietary intake.
Another important action is to avoid heating food or liquids in plastic containers. Microwaving polycarbonate plastics, or even washing them in a hot dishwasher, accelerates the rate at which BPA leaches out into the contents. Instead, transfer food to glass, ceramic, or stainless steel containers before heating.
For drinking, switch from polycarbonate plastic bottles to those made of glass or stainless steel. When purchasing plastic items, look for products specifically labeled “BPA-free,” although some replacement chemicals, such as Bisphenol S (BPS), may have similar endocrine-disrupting properties. Lastly, minimize handling thermal paper receipts, and wash your hands immediately after touching them.