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1. BACKGROUND Systematic epidemiological studies including environmental monitoring, whether directed toward the general population or workers exposed to carcinogens, provides mounting evidence that cancer may have its genesis in the environment (1,2). Based on this contention, some authorities have attempted to compute the percentage of (otal cancers that may be environmentally induced; some estimates being in the range of 80 to 90 percent (1,3). Others discount these numerical exercises, indicating that genetic factors and viral alterations of DNA may be basic to ultimate effects that become visible through chemical or physical agents (4). Consequently, it is perhaps more plausible to assume that a large component of total cancers environmentally induced is preventable. The potential for exposure to chemical, physical, and biological agents or to exogenous and endogenous chemicals, and/or metabolites, is most extensive. It is estimated that there are about four million chemicals in the universe, with an annual increase in the repository of several thousand new ones (2). Of course, with respect to specific chemicals, the human population may only potentially be confronted with a few thousand. The agents in the cancerinducing environment may involve contaminants in air, water, and diet, exposures to drugs and industrial chemicals, physical stress agents [radiation such as solar, nuclear, or gamma, and inhaled particulates (asbestos)], and natural toxins such as fungal and plant toxins (2). The International |
