Occupational and environmental lung diseases: an overview.

Chronic respiratory diseases other than lung cancer that are of occupational or environmental origin, along with cigarette smoking, account for over 100,000 deaths per year and are among the leading causes of respiratory disability in the United States and throughout the world. Lung cancer from these same exposures may account for 40,000 additional deaths per year. In spite of cigarette smoking's being recognized as the leading cause of both chronic obstructive pulmonary disease (COPD) and lung cancer, many other environmental and occupational exposures have been implicated as directly or indirectly associated with smoking in producing these diseases. In addition, the burden of disease is not uniformly distributed across the U.S. population. Furthermore, recognition of these associations with environmental and occupational exposures has done little in the last 20 years to reduce the burden of these respiratory conditions at the population level. COPD is the fourth leading cause of death in this country and, with asthma, accounts for one of the major categories of health care expenditure by whatever criteria are used. While the role of cigarette smoking is well characterized in these diseases as is the overwhelming role of smoking as the major cause of lung cancer, the identification of research objectives that could lead to strategies for lessening the burden of occupational and environmental causes of these chronic respiratory diseases is well worthwhile. For many years efforts to establish the number of people at risk in occupational settings have used estimates of employed and retired work forces in industries with known putative respiratory exposures. Often for legitimate reasons, developing these numbers has been extremely difficult, and thus the estimates are crude. Nevertheless, the National Institute for Occupational Safety and Health data suggest that over 20 million Americans are exposed to potential respiratory hazards in the workplace. Table 1 summarizes crude estimates of some of the major agents and industries in which exposures are known to occur. None of these exposures would be surprises to either the scientific community or the lay public, yet they continue to occur. Added to these numbers is the potential for over 100 million citizens to be exposed to environmental irritants from primary air pollutants that exceed the National Air Quality Standards first established by the U.S. Environmental Protection Agency in 1971 in many parts of the country at least several times per year. We approached this important topic by taking the view that it is critical to first understand the pathophysiologic, biologic, and general epidemiologic approaches that might be invoked in studying these diseases. Second, we explored the major environmental and occupational exposure patterns within the U.S. population. Finally, we selected the disease outcomes known to be associated with these exposures and asked experts to provide a selected review of the state of knowledge, to identify the important gaps in our knowledge, and to suggest avenues of research for the next 5-7 years. This effort brought together a wide variety of knowledgeable scientists with diverse expertise from basic science to clinical applications and population sciences. Although each manuscript in this monograph was produced independently, all authors had a common objective.