Criteria for qualitative assessment of carcinogenic risk and their application. Free

B200

The community is continually beset by the description of people who are suggested to be at increased risk of cancer because of their exposure to particular carcinogenic agent(s). We describe a basis for ranking such risks qualitatively by categorizing the relevant carcinogen and circumstances under which exposure occurs. This is distinct from hazard identification (which is confined to evidence of carcinogenicity) or quantitative risk assessment (which takes account of dose-response). The criteria for ranking carcinogens are those adopted by IARC and involve whether the agent is a (1) recognized carcinogen for humans; (2) probably; or (3) possibly carcinogenic for humans; (4) has inadequate evidence of carcinogenicity or (5) lack of carcinogenicity is evident. Circumstances of exposure is categorized by whether it (1) establishes the agent as a recognized carcinogen; (2) is one taken into account in establishing carcinogenicity status; (3) is distinct from those providing clearest evidence of carcinogenicity; (4) involve those in which absence of carcinogenic outcome is observed or (5) is not reasonably assigned to any of the above. Risk assessment may hence be characterized using four categories indicating the carcinogenic outcome anticipated: namely (in order of descending risk) Proven, Likely, Credible and Unlikely. Thus, for example, a Likely carcinogenic outcome occurs when exposure is (i) to a probable carcinogen in circumstances which contribute to establishing carcinogenicity status (ii) to a recognized carcinogen in circumstances distinct from those providing clearest evidence of carcinogenicity (iii) to a probable carcinogen in circumstances distinct from those providing clearest evidence of carcinogenicity. The risk assessment methodology has been applied to a range of situations including various types of pollution and usage of a range of consumer products. For recognized carcinogens, including asbestos, polycyclic aromatic hydrocarbons, arsenic and heavy metals, progressively decreasing levels of risk can correlated with occupational exposure, the impact of point source pollution, residence near contaminated sites and general environmental exposure. For organic solvents, pesticides, diesel exhausts and polychlorinated biphenyls, a carcinogenic impact on residents living near a production site, those living on or near the sites of earlier industrial activity or those living in a broad geographical location is less clear. Most of these risks can be distinguished from those associated with consumer products. Such qualitative risk assessment may find its greatest application in providing the broader community with assurance in respect of novel and highly-publicized situations.