The Environmental Working Group has a theory to explain why bisphenol-A, the controversial chemical that’s sometimes found in plastic bottles and can linings, shows up in the urine of over 90% of the population: it’s on paper receipts. The group found BPA on 40% of receipts collected from the sorts of businesses you visit every week, with the concentration topping 1000 times that of a can lining in some cases.

The American Chemistry Council told the Washington Post that BPA absorption level through the skin is fairly low. The group behind the study points out that receipts are often carried next to food items or in a wallet or purse and handled frequently, but the Washington Post point out that nobody knows “how much of the chemical that may rub off onto the hands is absorbed through the skin or whether people then ingest BPA by handling food or touching their mouths.”

If you’re trying to limit exposure to BPA, the study said Safeway’s receipts contained the most. The grocery chain told the Washington Post that it’s investigating the issue.

“Disputed chemical bisphenol-A found in paper receipts” [Washington Post]

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