In an article published on July 31, 2017 in the peer-reviewed journal Environmental Science & Technology, Jiaying Liu and Jonathan Martin from the University of Alberta, Canada, compared the kinetics of absorption and elimination of bisphenol A (CAS 80-05-7) in human biofluids following dermal and dietary exposure events.
Both free and conjugated forms of isotopically-labeled BPA were monitored in urine and blood of healthy male volunteers after the dosed uptake either through dermal (handling a simulated BPA-containing thermal paper receipt) or oral (eating a BPA-dosed cookie) routes. Both exposure scenarios were assessed in the same individuals with experiments one week apart from each other.
The researchers found that internal exposure to BPA was generally more prolonged after the dermal contact compared to the oral intake route. On average, following dietary exposure, total BPA in urine “peaked within 5 h and quickly cleared within 24 h.” In contrast, following dermal exposure, total BPA in urine peaked between 15 and 34 h post-exposure, with cumulative excretion increasing linearly for two days. Overall, internal BPA concentrations after dermal exposure were characterized by both a slow increase and a slow decrease, with residual concentrations still detectable over one week after the dermal exposure. Furthermore, the proportion of free BPA in both blood and urine was much higher after dermal exposure compared to dietary intake.
The authors concluded that their results showed that “total BPA in urine [most commonly used technique] may not be a good estimate of total or free BPA in systemic circulation resulting from a mixture of oral and dermal exposure.” Furthermore, “the prolonged exposure from single dermal contact events […] means that in the real world […] exposures could be cumulative, and higher steady state exposure from repeated dermal contact events must also be considered.”
Quoted in an article published by Chemical Watch on September 7, 2017, Steve Hentges, senior director of the American Chemistry Council’s (ACC) polycarbonate/BPA global group, commented that “the differences [between pharmacokinetics of oral and dermal BPA exposure] are important for an in-depth understanding of risk, but the differences by themselves are not an indication of risk. This also depends on exposure […].”
Deirdre Lockwood (September 4, 2017). “Touching thermal-paper receipts could extend BPA retention in the body.” Chemical & Engineering News
Chemical Watch (September 7, 2017). “Dermal BPA exposure levels may have been underestimated.”
Fernando Gomollón-Bel (September 9, 2017). “Shop receipts may explain majority of BPA detected in people.” Chemistry World
Liu, J., and Martin, J. (2017). “Prolonged exposure to bisphenol A from single dermal contact events.” Environmental Science & Technology, 51:9940-9949.