Water bottles that contain Bisphenol A -- also known as BPA -- raise the risk of heart disease and diabetes in people, according to a new study.

Earlier studies in lab animals also found a risk, according to a report in JAMA. The new study tried to look at low-level exposure over many years.

David Melzer, an author of the study from Peninsula Medical School in England, said it was the first done on people living what he called ordinary lives. His team studied data from the U.S. Centers for Disease Control and Prevention that measure environmental toxins.

They studied 1,400 adults and found that those with the most BPA in their urine had a higher risk of developing certain diseases.

"The quarter of the population with the highest levels of BPA were more than twice as likely to have diabetes or heart disease," he said.

Another researcher, Tamara Galloway, said that indicates a long-term exposure to very low levels of the chemical.

The authors said it was not clear why BPA raises those risks, though it is believed that it acts like a hormone and can disrupt the body's endocrine system, especially estrogen. That could have an effect in insulin resistance, they said.

Some people have also worried that BPA, because of its effect on hormones, may cause problems with sexual development in children.

FactsOnPET.com notes that most water bottles intended for a single use are not made from compounds that contain BPA. They are made from a different kind of plastic, which leads to them being stamped with a 1 symbol. The site noted that long-term polycarbonate bottles with BPA would be part of the group that gets a 7 notation.