Different frames, different fears: communicating about chlorinated drinking water and cancer in the Canadian media.

Risk issues become complicated when scientific evidence concerning a potential environmental exposure is equivocal; particularly when many argue that the public health benefits of a policy action outweigh any potential negative health effects. Chlorinated drinking water, and chlorinated disinfection byproducts (CDBPs) that are formed during the disinfection process, represent a useful case-study for examining these complications. We conduct a media analysis of chlorinated drinking water stories in the Canadian print media from 1977 to 2000. We examine media presentations of science compared to framings by scientists, regulators, the chlorine industry, water utility representatives, and non-governmental organizations of the CDBP issue based on key informant interviews. We argue that there are two main framings of the debate, each of which are powerful in constructing risk perceptions. On the one hand, many frame the debate as a 'voluntary' risk: we choose chlorine disinfection to protect against microbial risks with a possible adverse consequence of that protection. On the other hand, others frame the issue as an 'involuntary' risk: chlorine disinfection was a 'choice' imposed by public health and water utility officials; a choice that carries a potential cancer risk, and alternative disinfection technologies are advocated. We demonstrate these different frames by examining metaphorical constructs of water, chlorine and cancer contained within them.