Fiction. There are no dioxins in plastics, and even if there were, cold temperatures would be unlikely to release them.

This urban legend has been circulating as an e-mail warning citing research from Johns Hopkins University as proof that it’s true. But the school has issued no such warning nor conducted any research that supported the claim.

The e-mail message had become so pervasive that the university’s press office issued a pair of question-and-answer documents with its dioxin expert to set the record straight. Dr. Rolf Halden, an assistant professor in the Department of Environmental Health Sciences and the Center for Water and Health, says plastics don’t contain any dioxins and that freezing generally prevents rather than causes chemicals to be released.

Dioxins are a group of more than 200 organic environmental pollutants that have been called the most toxic compounds made by mankind.

Exposure to dioxins can cause cloracne, a severe form of skin disease, as well as reproductive problems, liver damage and cancer. Ukrainian President Viktor Yuschenko was poisoned with dioxins during his presidential campaign, leaving his face scarred and disfigured.

Exposure to dioxins can cause chloracne, a severe form of skin disease, as well as reproductive problems, liver damage and cancer. Ukrainian President Viktor Yuschenko was poisoned with dioxins during his presidential campaign, leaving his face scarred and disfigured.

Scientists now believe that dioxins are generally caused by various combustion processes, including natural events such as wildfires and volcanic eruptions. Environmental researchers have been focusing on the incineration of waste. One study found that burning household trash in the backyard can put out as much dioxin as a full-size incinerator burning hundreds of tons of refuse per day.

”The incinerators are equipped with state-of-the-art emission controls that limit dioxin formation and their release into the environment,” Halden says. ”But the backyard trash burning does not.”

Burning garbage sends dioxins into the atmosphere and they eventually end up stored in the fat of fish and animals. People are exposed to dioxins mainly from eating meat and fish. But not from their plastic water bottles, Halden says.

”People should be more concerned about the quality of the water they are drinking rather than the container it’s coming from,” he says. Halden says tap water is much more highly regulated and monitored for quality than bottled water. ”Bottled water can legally contain many things we would not tolerate in municipal drinking water,” he says.

But Halden warns that cooking with plastics might present some risk. Another group of chemicals, called phthalates, are sometimes added to plastics to make them flexible.

”If you heat up plastics, you could increase the leaching of phthalates from the containers into water and food,” he says. ”Chemicals can be released from plastic packaging materials like the kinds used in some microwave meals.”

Halden suggests using only plastics specifically meant for cooking. Heat-resistant glass, ceramics and stainless steel are better options for cooking. (Metal containers cannot be used in microwaves.)

– Markian Hawryluk