Toxic Chemicals in Cigarette Mainstream Smoke - Hazard and Hoopla

Abstract

These are curious times. The Canadian government has passed legislation that requires cigarette manufacturers to routinely test and publish the amounts of 44 toxic substances in cigarette mainstream smoke (MSS). Followingin the footsteps of their northern neighbor, various US legislators and regulators are considering modifications to their cigarette testing and reporting programs that will also list toxicants in MSS. Across the Atlantic Ocean, the European Commission has passed a directive that may also follow the North American lead for public disclosure of MSS toxic chemicals for each brand of cigarette sold in the marketplace. United Kingdom authorities have also expressed their intention to follow this mandate. It is difficult to understand the motivation and value of these existing or potentially forthcoming legislative actions. Although there is nearly total agreement among the world's scientists that cigarette smoking is a health hazard, few are bold enough to say with credibility which smoke chemicals or classes of chemicals are responsible for the adverse effects. Therefore, if the specialists are unable to interpret the smoke toxicant data, how is the general public to use their newfound knowledge? The posting of smoke chemical toxicant data is also problematic for the Tobacco Industry for several reasons. First, no standard analytical methods exist for most suspected toxicants. Second, the listing of smoke toxicant yields may ignite a 21 s t Century version of the "tar" wars in the USA during the 1960s; we have already seen evidence of such competition beginning in the US. Third, and most important of all, no one knows whether or not reducing the yield of one or more publicized MSS toxicant will result in a "less hazardous" cigarette. Assuming that the current situation is approximately as described above, the authors of this paper critically examined the existing lists of MSS toxicants. They discarded chemicals that are no longer relevant, e. g., DDT, N-nitrosodiethanolamine, added known smoke constituents that are glaringly absent, e.g., dioxins, and replaced the existing 1950-60s era nonfiltered cigarette MSS yields with those more representative of the present-day marketplace. Data for the Kentucky reference 1R4F cigarette smoked under standardized smoking conditions, i.e., those established by the International Organization for Standardization (ISO) and the Federal Trade Commission (FTC), are used as a surrogate for the modern-day cigarette whenever possible. A list of smoke toxicants and their approximate concentrations in today's cigarettes is nearly useless without an appropriate ranking of their relative toxicity. Unfortunately, the toxicological data for ranking importance are available for fewer than 5% of the approximately 4800 reported smoke constituents. Although neither of this paper's authors presumes to be a toxicologist, we cite in our discussion several published attempts at ranking smoke toxicants. Specifically, ranking by US Occupational Safety and Health Administration (OSHA) permissible workplace exposure levels, use of US Environmental Protection Agency (EPA) toxicity criteria supplemented with California EPA criteria, and use of the Human Exposure -Rodent Potential methodology and database developed by AMES et al. when data are available. There appears to be a wide divergence in the permissible exposures allowable in the workplace and those advocated by environmental regulators.