Skin contact with dermal paper may be a much more important source of endocrine disruptor than previously thought
Bisphenol A (BPA) is an endocrine disruptor that almost every person on the planet is invariably exposed to in the course of their everyday lives. Scientists had assumed dietary exposure was the main source, as BPA is used in the production of plastics and resins used to package food. However, new work suggests dermal exposure could explain the majority of human exposure.1 ‘If diet [were] the dominant source, we should find lower BPA in individuals who have been fasting,’ explains Jonathan Martin, an analytical chemist at Stockholm University and lead author on the new work. ‘But a large study in the US2 has shown this is not the case,’ he adds.
BPA is often used as a developing agent in thermal paper – it triggers the colour change of several dyes when exposed to heat. Socio-economic studies show that completely removing it would be financially unviable, but these new results may lead experts to reconsider. ‘There are reports of free BPA being detected in human blood, which should not happen after a dietary exposure,’ comments Martin. ‘We wondered if dermal exposure might therefore be an important piece of the puzzle.’
In this study, volunteers ate a cookie containing a few micrograms of BPA labelled with deuterium (BPA-d16). Analyses showed that their urine was free of the ingested BPA after 24 hours. But surprisingly, when subjects were exposed to BPA-d16 in thermal paper, the amount of BPA excreted increased linearly over the first two days. Moreover, half of the participants still had detectable amounts of BPA in their urine after a week. ‘Our study was initially designed to monitor the complete uptake and clearance of BPA over two days after the dermal contact,’ says Martin. ‘We were surprised to detect labelled BPA in urine of our returning participants after a whole week.’
Kurunthachalam Kannan, an expert in biomonitoring working at New York State University in the US, says ‘the results are interesting and significant from a human exposure point of view’. He adds that ‘this study is the first of its kind with human subjects. [Labelling BPA] is a good methodology and could be applied to other pollutants that are present in consumer products’.
Some scientists approached were sceptical of how labelled BPA was loaded onto the receipts because its distribution may alter the results. Nevertheless, Kannan says this method ‘should reflect what is present in thermal receipt papers’. The authors also defend their technique: ‘We agree that the simulated receipts were not exactly the same as the native thermal paper, but […] we do not believe [they] are a source of any bias,’ says Martin.
Martin also clarifies that studying the health effects of dermally absorbed BPA goes beyond the goals of this paper. They just want to raise concern about the dangers that ‘repeated dermal exposures could have […] for individuals handling many receipt papers daily’, he concludes.
This article was amended on 11 September 2017 to correct an error. Deuterium was used to label the BPA used in the experiments, and not radiolabelling as orignially written.
1 J Liu and J W Martin, Environ. Sci. Technol., 2017, DOI: 10.1021/acs.est.7b03093.
2 R W Stahlhut, W V Welshons and S H Swan, Environ. Health Perspect., 2009, 117, 784 (DOI: 10.1289/ehp.0800376).