In a growing debate, researchers have suggested a chemical additive used to make hard plastics —including toys, baby bottles and food storage containers — might promote breast cancer.

Theodore Widlanski, a chemistry professor at Indiana University, said his research team has found a potential mechanism linking bisphenol-A to the promotion of breast cancer. His study was published in the Aug. 28 issue of Chemistry & Biology.

While Widlanski said a possible link between the chemical and breast cancer existed, he noted more research was necessary to provide conclusive answers.

"We have only demonstrated a possible mechanism that explains what people have been speculating about for years," Widlanski said. "It doesn't mean that your bottled water is any less safe today than it was yesterday. It just means that if it isn't safe, we might be able to explain why."

No risk to consumers: Health Canada

Health Canada maintains that the chemical does not pose any risk to consumers. In recent studies, researchers have found that exposure to bisphenol-A does not pose a health threat.

"We've examined a risk for the toxicity of bisphenol-A and it does not pose a risk for the consumer," said Paul Duchesne, a media relations officer for Health Canada.

The agency said its research was backed up by other regulatory agencies in the U.S., European Union and Japan.

The U.S. Food and Drug Administration and the plastics industry also vigorously defend the safety of bisphenol-A, dismissing suggestions that its materials can leach dangerous toxins over time. The American Plastics Council maintains that exposure to bisphenol-A poses no known risk to human health.

But the City of San Francisco in June passed an ordinance banning toys and products with any levels of bisphenol-A for children under three years old based on studies that suggest the chemical can cause damage in young children. The ban, which will come into effect on Dec. 1, will prohibit the manufacture, distribution and sale of these goods.

San Francisco is the first U.S. city to implement such a ban. Another similar measure was proposed in the California legislature earlier this year, but it was not passed.