California may have banned the use of the chemical bisphenol A, or BPA, in baby bottles, but the threat of contamination remains in what we hold in our hands at any given moment.

A new study published in “Environmental Science & Technology,” an American Chemical Society publication, finds that thermal paper products are among the most pervasive carriers of BPA — and cash register receipts are the dirtiest of the lot.

BPA is an endocrine-disrupting chemical under increased scrutiny for a range of adverse health impacts. In the case of paper contamination, BPA can enter the bloodstream through the skin, and it can enter the skin to such a depth that it can’t be washed off.

State University of New York researchers and authors of the article Kurunthachalam Kannan and Chunyang Liao found BPA in 94 percent of the cash register receipts tested in the U.S., Japan, Korea and Vietnam, with one exception: The only receipts that were BPA-free were those from Japan, which phased out BPA use in 2001.

“Our results indicate that exposure of humans to BPA via paper products is ubiquitous because these papers are frequently used on a daily basis,” the authors write. They note that people handling receipts as part of their jobs are at greater risk of contamination.

“Handling of paper products can contribute up to 2 percent of the total daily BPA exposures in the general population, and that fraction can be much higher in occupationally exposed individuals,” the researchers report.

The Food and Drug Administration, which is studying new research on BPA, has said that low-level exposure appears to be safe.

Contaminating the Recycling Stream

Forget the idea that recycled paper might be safer: It’s not. BPA levels were found to be higher in recycled paper products, including paper towels and toilet paper, since BPA easily transfers from product to product. The study reports that approximately 30 percent of thermal papers are recycled.

“Recycling of thermal papers along with other papers can increase the risk of human exposure to BPA via cross-contamination of foods stored in recycled paper products,” according to the study. “BPA has been found in recycled paper towels and other food-contact papers at higher levels than is found in virgin papers.” Recycled paper is also used to make food containers.

The ease with which BPA transfers from one product to another is underscored by the researchers, who write, “Usually, people place tickets [beside] thermal receipts in their wallets and tickets can be contaminated by BPA via contacting with thermal receipts.”

BPA on receipts is responsible “for more than 98 percent of consumer exposure to BPA from paper,” according to the study, and the researcher estimate that receipts contribute about 33.5 tons of BPA to the environment every year in the U.S. and Canada.

Besides receipts, the study found BPA in flyers, including brochures and store coupons; magazines; mailing envelopes; newspapers; food containers, such as fast-food wrappers, paper cups, paper plates, pizza cartons and food buckets; printing paper; business cards; facial tissue; paper towels, and toilet paper. Most of these paper products were made from recycled paper, the authors add.

BPA is used as a coating in the thermal printing process. One of the most common chemicals worldwide, BPA is used primarily in plastics, including plastic liners in canned food and drinks.