New research suggests that people should avoid drinking water from plastic bottles if they have been sitting in a warm environment for a long time.

Researchers from the University of Florida found that when heated, plastic water bottles, which are made from polyethylene terephthalate, release the chemicals antimony and bisphenol A, commonly called BPA.

While the U.S. Food and Drug Administration has said BPA is not a major concern at low levels found in beverage containers, it continues to study the chemical's impacts. Some health officials, including those at the Mayo Clinic, say the chemical can cause negative effects on children's health.

And antimony is considered a carcinogen by the International Agency for Research on Cancer, part of the World Health Organization.

"If you store the water long enough, there may be a concern," researcher Lena Ma said in a statement.

For the study, Ma and colleagues looked at chemicals released in 16 brands of bottled water kept at 158 degrees Fahrenheit for four weeks, what researchers deemed a "worst-case scenario" for human consumption.

The study found that as bottles warmed over the four-week period, antimony and BPA levels increased.

Of the 16 brands, only one exceeded the EPA standard for antimony and BPA. Based on the study, storage at warm temperatures would seem to not be a big problem, Ma said. But she said more research is needed to know if other brands are safe.

"More attention should be given to other drinks packaged with polyethylene terephthalate plastic, such as milk, coffee and acidic juice," she said. "We only tested the pure water. If it is acidic juice, the story may be different."

The findings were published in the journal Environmental Pollution.