Evidence is growing that there may be a connection between certain chemicals in the environment and the rising incidence of breast cancer in North America. Two recent Canadian conferences have been held to disseminate information and another is planned for 1996. "We have a situation that is similar to global warming, " Devra Lee Davis, founder of the US Breast Cancer Prevention Collaborative Research Group, warned people attending a conference in Niagara Falls, Ont. "Breast cancer continues to increase. The increase is greatest among older women who have fewer of the known risk factors. It makes sense to try to limit exposure to things that could be promoting the disease."