Even minimal exposure to bisphenol A (BPA), a chemical found in many plastics, can permanently alter gene expression, masculinizing females and feminizing males—a finding that raises fresh concerns about the widespread use of this common compound.
BPA is a synthetic organic chemical used in the production of plastics found in everyday items like food trays, cutlery, and plastic bottles, as well as certain medical equipment. While it’s been banned in many products, significant amounts of BPA still appear in people’s urine, according to measures.
The bans followed research demonstrating BPA’s role as an endocrine disruptor, interfering with the body’s hormones—estrogens, thyroid hormones, and androgens—and correlating with health issues like obesity, allergies, and kidney disease.
These health effects can begin before birth, as BPA crosses the placental barrier and is found in umbilical cord blood and amniotic fluid. Studies suggest early exposure can influence the development of diseases like diabetes, cardiovascular disease, and cancer later in life.
Because of its impact on estrogen production, researchers also suspect BPA may affect bone metabolism and, consequently, immune health, as bone marrow is a key site for immune cell production.
However, the precise gene expression changes underlying these effects remained unclear—until recently. A new study published in the journal Communications Medicine sheds light on how BPA alters gene expression even before birth.
“Our results show that prenatal exposure to low doses of BPA has long-term, sex-specific effects on rat metabolism. We also show that these effects are similar to those observed in people with metabolic syndrome,” the study authors write.
Sex-Specific Metabolic Changes
Researchers evaluated BPA’s impact during pregnancy by giving pregnant rats drinking water containing two levels of BPA: one mirroring typical daily human exposure (0.5 micrograms per kilogram of body weight per day) and another representing a safe exposure level considered in 2015 (50 micrograms per kilogram of body weight per day). They then measured gene expression in the bone marrow and blood markers of the offspring as adults.
“We observed lasting effects in adult rats,” explains Thomas Lind, of Uppsala University, author of the study, in a communiqué. “Even very low doses changed gene expression. Females have undergone masculinization and males have undergone feminization.”
Adult rats exhibited significant sex-specific metabolic changes. Females developed metabolic signatures linked to cancerous processes, while males showed profiles associated with metabolic syndrome, increasing their risk of diabetes and heart disease.
The researchers also found increased T cell activity in males and decreased activity in females, consistent with previous studies linking these immune cells to BPA exposure.
Blood marker analysis revealed a disturbed lipid profile, accelerated metabolism, and thyroid hyperactivity in males. In contrast, females showed decreased blood sugar, reduced insulin, and increased testosterone activity—a pattern similar to polycystic ovary syndrome (PCOS).
“These results also support previous studies in humans showing that women with polycystic ovarian syndrome (PCOS) had higher levels of bisphenol A in their blood, which correlates with an increased influence of male sex hormones. This reinforces the findings of other studies linking bisphenol A exposure to reduced fertility in women.” Lind explains.
The researchers emphasize the need for stricter regulation of BPA in consumer products, particularly those in contact with food. “Although the results are based on experimental data, they support the decision of the European Food Safety Authority (EFSA) to significantly reduce the acceptable daily intake of this substance, setting it at 0.2 nanograms per kilogram of body weight per day, which is 20,000 times less than the previously accepted value of 4 micrograms per kilogram of body weight per day,” Lind concludes.
