On December 5, 2019 the peer-reviewed scientific journal The Lancet Diabetes & Endocrinology published the study “BPA: have flawed analytical techniques compromised risk assessments?” by Roy Gerona, Frederick vom Saal and Patricia Hunt. Urinary levels of bisphenol A (BPA; CAS 80-05-7) were measured using a newly developed method and compared to levels measured with the standard method. Specifically, the human metabolism converts BPA into conjugates which are more water soluble and excreted with urine. Using the standard method, urine samples are first treated with enzyme to deconjugate BPA. After the deconjugation treatment, free (or ‘unconjugated’) BPA is then measured.

However, deconjugation by enzymatic treatment is not always complete, and this leads to conjugated BPA remaining in the sample but not being detected in urine using the standard method. This means that actual human BPA exposure is underestimated, since urinary BPA levels are a proxy for estimating the amount of BPA people ingest, inhale, or take up via skin contact.

Gerona, vom Saal, and Hunt have developed a new method which measures free, unconjugated BPA as well as the conjugated forms of BPA, leading to a complete assessment of all BPA forms in urine samples and thus a more complete estimate of what humans are actually exposed to. This novel method was able to be developed because analytical standards of conjugated BPA are now commercially available. Using the new method, Gerona and colleagues showed that especially higher levels of human BPA exposure are systematically underestimated using the standard approach where only free BPA is measured.

This finding is significant for the assessment of health risks associated with human exposure to BPA. Previous epidemiological studies linking BPA exposure to adverse human health outcomes most likely underestimate actual human exposure levels, thus leading to actual associations with disease being missed.

Read more

Holden, E. “BPA chemical levels in humans drastically underestimated, study finds.” The Guardian. 5 December 2019.

EurekAlert (December 5, 2019). “Study finds BPA levels in humans dramatically underestimated.

Brian Bienkowski (December 6, 2019). “Federal tests ‘dramatically’ undercount BPA and other chemical exposures.Environmental Health News

Emma Davies (December 12, 2019). “Human BPA exposure underestimated, researchers warn.Chemical Watch


Gerona, R. et al. “BPA: have flawed analytical techniques compromised risk assessments?The Lancet Diabetes & Endocrinology (published December 5, 2019)