DOI: 10.1097/01.jom.0000079089.95532.0d
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PMID: 12915780
Issn Print: 1076-2752
Publication Date: 2003/08/01
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Excerpt
The current national project of mortality analysis in the motor vehicle industry was launched in 1982, spurred by media reports of possible work-related cancer among model and patternmakers on the design staffs of the auto companies. 2 Later study observed excess mortality from colon cancer among this group. 3–5 Another initial media release regarding lung cancer mortality among die-cast and plating workers manufacturing automotive hard trim was confirmed by subsequent study. 6 The International Union, United Automobile, Aerospace and Agricultural Implement Workers, UAW, announced a “cancer policy,” including research. 7 Starting in 1984, research funds, jointly administered with external peer review, were instituted at GM, Ford, and Chrysler. Many of the studies cited by Delzell et al were products of that arrangement, and the Delzell study was an outgrowth of the evolving body of knowledge. This study updates previous reports, which did not contain the process-specific results revealed here. 8,9 Although presented as a descriptive cohort mortality study, the work also tests hypotheses generated by previous and contemporary work. The slate of data regarding work-related mortality in the motor vehicle industry is not clean but rather is marked up and constantly in revision.
The massive cohort is the most impressive feature of this report. The investigators understate the painstaking work necessary to “clean up” the corporate personnel record database supporting this study. This required extensive support from management’s epidemiology personnel. They solved numerous puzzling features of a personnel and timekeeping system designed to support manufacturing, not epidemiology. Despite this, job categories within the personnel system and manufacturing process groupings provide ambiguous information for characterization of chemical exposure.
For outcomes other than lung cancer, cohort-wide findings more likely reflect methods issues and work-related stressors, such as noise, work schedule, and work organization, common across manufacturing industry. Chemical exposure factors would be much diluted given the diversity of processes and exposures across plants. However, the five major production groups were vehicle assembly, stamping and fabrication, transmission and chassis, engine, and casting. These together contributed about 81% of the persons in the cohort, with assembly alone contributing 35%. It would not be surprising if workers in casting operations (who are exposure to silica, formaldehyde, and combustion products, which are identified lung cancer risks), combined with the considerable literature showing excess mortality, were to suffer increased lung cancer. Vehicle assembly and stamping encompass extensive welding operations also are identified as a possible lung cancer risk. The investigators presented relative risks between processes as a measure of process specific hazards. This analysis likely compared high with higher risks. More appropriate would be identifying groups thought to be without notable occupational chemical exposures, such as parts depots (lung cancer standardized mortality ratio [SMR] 80 [CI = 63–99]) as the reference population within the cohort.
Our first concern with the report is the interpretation of the SMR for all causes combined. The investigators correctly note that this is 8% below the general population and significantly so. Our question is whether this deficit should be considered an elevation, given knowledge of the “Healthy Worker Effect.
