Richard A. Lemen

If we are to approach developing a safe and healthful workplace in a more timely fashion, a more generic approach must be considered and applied instead of developing recommendations and standards simply on a substance-by-substance basis, an approach that has been the most prominent. Some examples in which developing generic standards may be appropriate are: cholinesterase-inhibiting substances, neurotoxic agents, reproductive hazards, cold environments, and vibration syndrome, to name but a few. It is important to recognize that developing standards based on individual substances often does not allow for the role of synergism, a reaction that has had little study, but it is important in controlling occupational disease and injury. These concerns can be addressed in several ways. One is to look at processes or conditions found in the workplace; for example, coke oven emissions that OSHA has promulgated into a standard and, as NIOSH has done in their recommendations to OSHA for foundries, coal tar products, the manufacture of paint and allied coatings, field sanitation, hazardous waste management, hot environments, and confined spaces. Another is to address groups of similar substances such as NIOSH has done with alkanes, benzidine-based dyes, diisocyanates, dinitrotoluenes, and glycol ethers. A third comprehensive approach is to look at general categories of hazards, such as the generic carcinogen policy, and the hazard communication rule. Finally, risk must be considered in the development of any standard. Nelson Rockefeller once said in relation to an incidence involving a radiation hazard that, "you can't have a riskless society." I would amend this to say that you cannot have a reckless society either. Safety and health regulations are essential and must be designed, promulgated, and then enforced so that a reckless society is avoided or controlled, with a riskless society being the ultimate aim.

BACKGROUND: Asbestos-related diseases are still a major public health problem. The World Health Organization (WHO) has estimated that 107,000 people worldwide die each year from mesothelioma, lung cancer, and asbestosis. We review what is known about asbestos use, production, and exposure and asbestos-related diseases in the world today, and we offer predictions for the future. Although worldwide consumption of asbestos has decreased, consumption is increasing in many developing countries. The limited data available suggest that exposures may also be high in developing countries. Mesothelioma is still increasing in most European countries and in Japan but has peaked in the United States and Sweden. Although the epidemic of asbestos-related disease has plateaued or is expected to plateau in most of the developed world, little is known about the epidemic in developing countries. It is obvious that increased asbestos use by these countries will result in an increase in asbestos-related diseases in the future.

OBJECTIVES: This article examines the credibility and policy implications of the "amphibole hypothesis," which postulates that (1) the mesotheliomas observed among workers exposed to chrysotile asbestos may be explained by confounding exposures to amphiboles, and (2) chrysotile may have lower carcinogenic potency than amphiboles. METHODS: A critical review was conducted of the lung burden, epidemiologic, toxicologic, and mechanistic studies that provide the basis for the amphibole hypothesis. RESULTS: Mechanistic and lung burden studies do not provide convincing evidence for the amphibole hypothesis. Toxicologic and epidemiologic studies provide strong evidence that chrysotile is associated with an increased risk of lung cancer and mesothelioma. Chrysotile may be less potent than some amphiboles for inducing mesotheliomas, but there is little evidence to indicate lower lung cancer risk. CONCLUSIONS: Given the evidence of a significant lung cancer risk, the lack of conclusive evidence for the amphibole hypothesis, and the fact that workers are generally exposed to a mixture of fibers, we conclude that it is prudent to treat chrysotile with virtually the same level of concern as the amphibole forms of asbestos.

A previous retrospective mortality study of 292 U.S. cadmium production workers employed for a minimum of 2 years showed increased mortality from respiratory and prostate cancer and from nonmalignant lung disease. To examine further the mortality experience of these workers, investigators from the National Institute for Occupational Safety and Health extended the study to include 602 white males with at least 6 months of production work in the same plant between 1940 and 1969. Vital status was determined through 1978, which included the addition of 5 years to the original follow-up. Cause-specific mortality rates for seven causes of death potentially related to cadmium exposure were compared between the overall cohort and U.S. white males and between subgroups. Mortality from respiratory cancer and from nonmalignant gastrointestinal disease was significantly greater among the cadmium workers than would have been expected from U.S. rates. All deaths from lung cancer occurred among workers employed for 2 or more years. A statistically significant dose-response relationship was observed between lung cancer mortality and cumulative exposure to cadmium. A 50% increase in lung cancer mortality, which was not statistically significant, was observed even among workers whose cumulative exposure to cadmium was between 41 and 200 µg/m3 over 40 years. Since the previous investigation, no new deaths from prostate cancer and no excess of deaths from nonmalignant respiratory disease have been observed.