Changing approaches to assessment of environmental inhalation risk: a case study

Approaches to assessing environmental inhalation risk from asbestos have undergone profound change. In addition to social and political changes, a number of factors have come into play: 1. new technologies 2. new measuring instruments 3. new biological data 4. increased utilization of asbestos 5. regulatory imperatives 6. a redefinition of health risks associated with asbestos. This has occurred over a period of little more than 60 years. Early air-sampling instruments were developed to measure particles and fibers in air. Because asbestosis was a fibrotic disease, all measurements quantitated fibrotic disease risk in the environment by focusing on fibers and particles. Subsequently, the understanding that asbestos forms only fibers in air refocused measurement on fibers, not fibers and particles. As research clarified which fibers reached the lungs, new ways to sample and evaluate air were required. At the same time, changes in understanding of the disease process created the need for a better way to measure risk. In the 1960s, acceptance of the knowledge that asbestos causes both cancer (based on the no threshold assumption for carcinogens) and fibrosis raised the question of which fiber sizes should be measured and what the standard should be. The scientific assumption, prevailing both in 1985-86 and today, of a linear nonthreshold dose-response curve for carcinogens was applied to estimates of risk for asbestos exposure in the workplace, which led OSHA to lower the U.S. standard. In summary, we have attempted to illustrate the close link between state-of-the-art scientific and technical knowledge and policy decisions to control a toxic substance in industrial society. In the best of all possible worlds the science should permit valid estimates of risk and construct measurement techniques that lead to the desired control. If awareness comes early, then the process of policy making should be an iterative one, with incrementally more restrictive control as knowledge of the toxicant improves. The imperative for control of asbestos, as with many other toxic materials, was regulation, not science. That, however, is another story. Regulation of the workplace environment activated use of the science that permits valid estimates of risk and the techniques for measurement and control. The evolving science became part of the debates on control and constantly refocused them. Setting acceptable workplace exposure levels to control inhalation risk from asbestos did not occur on a wide scale until after 1970.(ABSTRACT TRUNCATED AT 400 WORDS)