When people handle receipts printed on thermal paper containing the endocrine disruptor bisphenol A (BPA), the chemical could linger in the body for a week or more, according to a new study (Environ. Sci. Technol. 2017, DOI: 10.1021/acs.est.7b03093). BPA ingested from food, however, is excreted within a day.
Jonathan W. Martin of Stockholm University and Jiaying Liu of the University of Alberta used isotopically labeled BPA to follow what happens when people are exposed to typical levels of the compound in everyday situations: handling receipts, consuming food stored in BPA-lined aluminum cans, or drinking beverages from BPA-hardened plastic bottles, for example. They tested six male volunteers, who handled simulated thermal receipts containing labeled BPA for five minutes. The subjects then wore a nitrile glove for two hours and washed their hands with soap. Afterwards, the researchers measured the labeled BPA in the volunteers’ urine regularly for two days. A week later, the researchers fed each of these volunteers a cookie containing labeled BPA, again monitoring its concentrations in urine. The doses of BPA were lower than the tolerable daily intake set by the European Food Safety Authority.
After the volunteers handled the receipts, total BPA—including free and metabolized forms of the compound—in their urine increased linearly over two days. Surprisingly, after a week, three of the volunteers still had BPA in their urine. However, after volunteers ate the cookies, total BPA in urine spiked within five hours and was fully cleared within a day. Notably, the free, unmetabolized form of BPA—which is more toxic than its metabolites—made up a higher percentage of the compounds in urine after dermal exposure than after dietary exposure.
Ingested BPA is rapidly metabolized in the liver and quickly excreted, Martin says. But when the compound is absorbed through the skin, it is probably metabolized much less efficiently, which could lead to a more toxic exposure. “The use of BPA in thermal receipts needs to be reconsidered,” he says. Some manufacturers are replacing it with similarly concerning chemicals, he says, such as bisphenol S, but “more thought needs to be put into safer alternatives.” Along those lines, some stores have switched to vitamin C-based thermal receipts.