In the study, each standard deviation increase in urinary BPA levels, a proxy for BPA exposure, increased the risks of cardiovascular disease and diabetes by 39% each.
Findings from animal studies have raised concerns that low-level exposure to BPA may have a harmful in humans, senior author Dr. David Melzer, from Peninsula Medical School in Exeter, UK, and colleagues explain.
Most research has focused on the estrogenic activity of the chemical, but there is evidence that BPA may cause damage through other mechanisms, including disruption of pancreatic beta-cell function and obesity-promoting effects. Initially, it was believed that there was a safe threshold for exposure, but recent reports have questioned this.
The present study involved a cross-sectional analysis of data from the National Health and Nutrition Examination Survey 2003-2005. Included were 1455 subjects, between 18 and 74 years of age, who had urinary BPA levels measured.
As noted, higher urinary levels of BPA were associated with elevated risks of both cardiovascular disease (p = 0.001) and diabetes (p < 0.001). By contrast, BPA exposure did not appear to have an effect on the occurrence of other common diseases, including arthritis, cancer, liver disease, respiratory disease, stroke, or thyroid disease.
An increase in urinary BPA was also associated with abnormal levels of two liver enzymes. For each standard deviation increase in BPA levels, the likelihood of an abnormal level for gamma-glutamyltransferase and alkaline phosphatase rose by 29% (p < 0.001) and 48% (p = 0.002), respectively.
The current research supports animal data, but "independent replication and follow-up studies are needed to confirm these findings and to provide evidence on whether the associations are causal," the research team notes.
In an accompanying editorial, Dr. Frederick S. vom Saal, from the University of Missouri, Columbia, and Dr. John Peterson Myers, from Environmental Health Science in Charlottesville, Virginia comment that this research "should stimulate further studies and reevaluation of the basic assumptions in chemical risk assessments that led to US Food and Drug Administration assurances that BPA is safe."
The editorialists add that the results "also heighten incentives for green chemistry (a new field based on collaboration between biologists and chemists to develop biologically inert chemicals for use in products) to find cost-effective replacements for BPA applications contributing to widespread human exposures."