NIOSH Programs > Respiratory Diseases > Evidence Package > 4. Airways Diseases > 4.2 Obstructive Airways Disease
4.2b) Assess the Extent, Severity, and Burden of Work-Related COPD and Identify Industries, Occupations, and Occupational Exposures Associated with Potential High-Risk of COPD4.2a) Establishing the Work-relatedness of COPD | 4.2c) Prevention of COPD through Workplace Spirometric Monitoring and Intervention
There is uncertainty concerning the overall impact of occupational exposure on the burden of COPD morbidity and mortality in the U.S. because workplaces present a wide range of both known and covert respiratory exposure hazards. RDRP intends to provide estimates of the extent, severity, and burden of COPD associated with occupational exposure. Through this activity, RDRP not only strives to identify potential problem areas but also provides methods to monitor trends over time, thus enabling assessment of disease prevention measures.
Another issue has been the development of reliable, scientifically valid procedures for measuring ventilatory function in field survey settings and interpreting the results.
RDRP has pursued three paths towards problem identification and burden assessment. These have included:
Past research on the first component in this topic included COPD-focused segments of industry-specific studies associated with various work place exposures (including diesel exhaust, dusts, and fibers). More recently, this activity is being under taken by pertinent analysis of existing population-based datasets. These include national mortality data, various large-scale population-based surveys (e.g. the National Health and Nutrition
Examination Survey [NHANES]), and certain other databases of morbidity information working with external researchers (e.g. the Lung Health Study and Kaiser Permanente Medical Insurance data). Information from these surveys and databases has provided useful information on COPD extent and severity, its geographical pattern, its temporal trends, and its relationship with occupation and industry. In addition, RDRP is currently conducting a project involving the acute and chronic respiratory effects of smoke exposure in wildland firefighters.
To improve diagnosis of COPD, RDRP scientists are extensively researching spirometric measurement techniques and methodology, and also developed authoritative spirometric reference values applicable to the three major race/ethnic groups in the U.S. population. This was done using the third National Health and Nutrition Examination Survey (NHANES) data collected from 1988 to 1994, for which RDRP scientists were responsible for spirometry measurements.
In collaboration with researchers from the University of California (Los Angeles), RDRP scientists have used the large, population-based National Heart, Lung, and Blood Institute (NHLBI) Lung Health Study database to investigate the effect of occupational exposures to dust, gases, fumes, vapors, and sensitizers on lung function decline. Occupational exposure was assessed using a Job-Exposure Matrix (JEM) based on self-reported job. Results indicate that occupational exposure to fume is significantly associated with increased rate of lung function decline in individuals with early COPD and suggest opportunities for primary and secondary prevention in workers exposed to fumes.
In collaboration with researchers at the Tulane University, RDRP scientists have studied the effects of substances classified as particles not otherwise classified or particles not otherwise regulated on respiratory health. The project used longitudinal spirometry data from more than 12,000 workers employed in eleven industrial plants. Findings identified occupational categories associated with increased risk of COPD and provide further evidence for the need for the development and implementation of strategies to prevent work-related COPD in high-risk settings.
In collaboration with researchers at the University of Oregon, RDRP scientists evaluated the work-relatedness of COPD identified in a population of the membership of Kaiser Permanente Northwest Division. A case-control study design was used along with a new JEM approach for assessment of occupational exposure. Findings indicated elevated COPD odds ratios for a variety of exposures, including metal and mineral dust, diesel exhaust, and irritant gases and vapors.
Outputs and Transfer
In the 1970s and 1980s RDRP epidemiological activities relating to COPD and associated outcomes included an extensive program of field studies in a variety of settings. These investigations typically included the measurement of lung function and assessment of chest symptoms. Results were published on workers exposed to coal, cotton, attapulgite, wollastonite, salt, potash, trona, talc, oil shale, and other substances. In particular, RDRP orchestrated a major initiative on the respiratory effects of diesel exhaust, pursuing an extensive program of research in various mining settings. Concomitant laboratory investigations often complemented the field research. Outputs from this research, together with RDRP outputs from more recent research efforts, have included 53 publications in peer-review journals and conference proceedings (A4-58).
With respect to surveillance, statistics on COPD occurrence by industry and smoking status are periodically published in the “WoRLD Surveillance Report” and on the NIOSH Web site (“Occupational Respiratory Disease Surveillance [ORDS]” Topic page; A4-59). The most recent edition of the “WoRLD Surveillance Report,” published in 2002 (A4-60), has been cited in at least 140 other publications (chapter 8).
An important RDRP-authored paper that further described the extent of the problem of COPD in the U.S. used the population-based NHANES III data to derive the fraction of COPD associated with occupational exposure. This was estimated as 19 percent overall and 31 percent among never smokers. It also showed that industries and occupations associated with increased prevalence of COPD included rubber, plastic and leather manufacturing; textile mill products; the armed forces; food product manufacturing; repair services and gas stations; agriculture; and construction (8, A4-61). A related paper showed that race/ethnic specific estimates of occupationally attributable fractions for COPD were highest among Mexican-Americans, indicating an important segment of the population at risk of disease (9, A4-62).
RDRP scientists developed important reference equations for spirometry (10, A4-63). These reference equations have become adopted as the “gold standard” for the field. They are widely used and have been adopted by the American Thoracic Society and spirometer manufacturers for use in clinical and research settings for Caucasian, African-American and Mexican-American populations.
An RDRP scientist collaborated with other experts to estimate the burden associated with occupationally-caused COPD. The overall cost of COPD associated with occupational exposure was estimated as five billion ranging from $3.3 to $6.6 billion. Of this cost, 56 percent was estimated as direct and 44 percent as indirect costs. The estimates obtained were based on an assumed fraction of COPD associated with occupational exposure of 15 percent. The conclusion is that the large cost of work-related COPD warrants preventive interventions (11, A4-64).
The RDRP project studying the acute and chronic respiratory effects of smoke exposure in wildland firefighters held a symposium in 2005 to disseminate findings and to discuss with the DOI the best ways to incorporate the findings into DOI policy (A4-65).
Since smoking is not only a major confounder for occupational exposures but also a source of workplace exposure in itself, RDRP organized a workshop to address the impact of tobacco smoking on the health of American workers. Findings were published in “Work, Smoking, and Health, A NIOSH Scientific Workshop Proceedings” (A4-66).
Together with the findings on coal miners (chapter 4.2a), which demonstrated that the effect of dust exposure on the lung was non-trivial, the results from the studies undertaken under this component of the COPD research program show that the problem of occupational COPD is widespread and has important ramifications in terms of social and fiscal costs; that is, RDRP has not only shown that COPD causes impairment and mortality, but that it is a problem that extends well beyond workers in the traditional heavy industries. These findings, then, provide both the motivation and the direction for action.
The American Thoracic Society Statement on “Occupational Contribution to the Burden of Airway Disease noted for COPD” states that, “an increasingly impressive body of scientific literature is available demonstrating that specific occupational exposures contribute to the development of COPD.” Among the 21 citations given pertinent to this statement are four involving papers by RDRP scientists, demonstrating the important RDRP contribution to this authoritative pronouncement by a major professional medical association.
As noted previously, the so-called “Hankinson prediction equation” (10, A4-63) for categorizing spirometric values as normal or abnormal have been widely adopted not only in occupational, but also in clinical settings. This is reflected in the large number of times the research has been cited since it was published in 1999 (234 citations).
As noted in the previous section, RDRP surveillance data for COPD is widely cited and used by others.
Progress Towards End Outcomes
RDRP research in this area has provided evidence, justification, and guidance on the need, occupations, and exposures to which COPD prevention activities should be targeted. In the case of coal mining, dust exposures known to cause COPD have been markedly reduced through the efforts of RDRP and many others. However, documentation of prevention and reduction of COPD as a result of reductions in causative exposures will be problematic for several reasons. COPD is a chronic disease taking years to develop and for adverse effects to be demonstrated. Thus, there can be no rapid assessment of the benefits of reductions in occupational exposures. In addition, since workplace exposures account for only a minority of COPD cases compared to smoking, assessment of the benefits of prevention programs is greatly hampered by the concurrent temporal trends in smoking habits that have been taking place. However, efforts to understand the occupational contribution to COPD and how to prevent it have the potential to be of great benefit.
RDRP will continue to further evaluate the status and changes in the occupational exposure profile and in the burden of COPD due to occupational risk factors in the U.S. This is being done through periodic updates to RDRP’s “ORDS” Web site and updates to the “WoRLD Surveillance Report.”
RDRP is collaborating with NCHS and the NHLBI to provide support for spirometry testing in the U.S. based-population NHANES 2007-2008 study. The study will include a questionnaire designed by RDRP investigators for the assessment of occupational exposure, which is intended to result in data suitable for analysis of the effect of various occupational exposures on lung function.
Findings from several RDRP collaborative research efforts (with researchers from the University of California Los Angeles, Tulane University, and the University of Oregon will be published in the peer-reviewed literature.
In addition, RDRP scientists will continue to seek and analyze datasets that could supply information that could help quantify work-related COPD, identify worker populations at risk for work-related COPD, and elucidate relationships of COPD with occupational exposures.