Risk Analysis, Part 2. How We Evaluate The Health Risks of Toxic Substances in the Environment

Almost every aspect of modem living exposes us to health risks. The air we breathe, the food we eat, the water we drink, the drugs we take, and the places where we work may be contaminated by toxic substances or additives. This is in addition to natural carcinogens, such as sunshine, and habits such as smoking, or the way our food is cooked. Their effects on our health may not be noticed until 20 or 30 years after exposure. These effects may include cancer and organ damage of one kind or another. Other unfortunate effects are suffered by future generations—genetic mutations, birth defects, inherited diseases, and so on. This tragic loss and impairment of life could be prevented or signtilcantly reduced by identifying and regulating substances in the environment that pose risks to human health. In the first part of this essay, I introduced the topic of risk analysis, 1 Risk analysis is a relatively new research specialty. Its objective is the estimation of potential consequences from exposure to various hazards, such as nuclear reactor accidents. This part is devoted to risk analyses of exposure to toxic substances—carcinogens, mutagens, teratogens, and so on. These include a large variety of natural and synthetic chemicals and pharmaceuticals, as well as various pollutants in the environment. It should be noted here that many researchers feel there is a bias toward identifying cancer risks while other health risks are given a lower priority.zg T. Colin Campbell, Cornell University, Ithaca, New York, says there is a “disproportionate effort given to the evaluation of chemical carcinogens” even though “a vast diversity of chemical toxicities is possible.”q Other important health risks include black lung, brown lung, asbestosis, cardiac disease, congenital abnormalities, infertility, and so on. Ralph E. Yodaiken, National Institute for Occupational Safety and Health, Rockville, Maryland, says, “These diseases and many others should command as much attention as cancer.”3 However, cancer risks now occupy center stageJ’t because of “the rapid rate at which we are detecting carcinogens in our environment, coupled wit h increased consumer awareness, indeed a fear of cancer, ” according to I.C. Munro and D.R. Krewski, Health and Welfare Canada, On tario.2 Thii essay will reflect the risk assessment community’s focus on cancer, but you should keep in mind that other signtilcant health risks are involved in our exposure to toxic substances. Bruce Ames, University of California, Berkeley, says there is a critical need today for quantitative risk analyses of the large number of man-made and natural toxic substances in order to set priorities. Each year about 1,000 new chemicals are released for commercial use. 5 This is in addition to more than 70,000 man-made chemicals already being used.b Also, most people do not realize there is a tremendous amount and variety of toxic chemicals in our foods. These include natural defense chemicals from plants and carcinogens and mutagens made when cooking food,sT.g Only a small fraction of these