Low levels of common environmental chemicals can act together to disrupt human tissues in ways that eventually lead to cancer – even at concentrations believed to be safe, new research suggests.

The findings – by an international environmental-health task force of nearly 200 scientists from 28 countries – are based on a three-year investigation of the health effects of low-dose levels of 85 common chemicals not considered to be carcinogenic to humans.

Among the chemicals studied: bisphenol A (BPA), used in plastic food and beverage containers; rotenone, a broad-spectrum insecticide; paraquat, an agricultural herbicide; and triclosan, an antibacterial agent used in soaps and cosmetics.

Drawing on hundreds of laboratory studies, the researchers found that 50 of the 85 chemicals had been shown to disrupt functioning of cells in ways that correlated with patterns of cancer, even at the low, presumably benign levels at which most people are exposed.

"Our findings also suggest these molecules may be acting in synergy to increase cancer activity," said William Bisson, an assistant professor and cancer researcher at Oregon State University and a team leader on the study. "For example, EDTA, a metal-ion-binding compound used in manufacturing and medicine, interferes with the body's repair of damaged genes.

"EDTA doesn't cause genetic mutations itself, but if you're exposed to it along with some substance that is mutagenic, it enhances the effect because it disrupts DNA repair, a key layer of cancer defense."

The study is part of the Halifax Project, sponsored by the Canadian nonprofit organization Getting to Know Cancer. The team's findings are published in a series of papers in a special issue of the journal Carcinogenesis.