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Occupational risk factors for selected cancers.

We read with interest and concern the article “Occupational Risk Factors for Selected Cancers Among African American and White Men in the United States” in the October 2003 issue of the Journal.1 The authors found that in a study with a small number of African American male cases, occupational exposure to chromium was associated with non-Hodgkin’s lymphoma and exposure to wood dust was associated with Hodgkin’s disease and soft-tissue sarcoma in African American men. However, in White men, the odds of these occupational exposures among men with non-Hodgkin’s lymphoma, Hodgkin’s disease, or soft-tissue sarcoma were almost identical to the odds among the control subjects.1 Since the sample size of White men was more than 10 times the size of the African American sample, the data for White men should generate a more reliable inference. 
 
Although there are different magnitudes of association between risk factors and diseases among racial groups,2,3 few biological risk factors cause a specific cancer in 1 race but not in another race. In addition, the incidences of non-Hodgkin’s lymphoma and Hodgkin’s disease are lower in African American men than in White men in the United States, though the overall cancer incidence for African American men is about 24% higher than that of White men.2,3 It is unlikely that racial predispositions play a major role in the occurrence of these cancers. 
 
The chemical natures of chromium and wood dust are harmful to human cells, but the results of their associations with lymphoma and soft-tissue sarcoma are inconsistent.4–7 For example, significantly increased risks for both non-Hodgkin’s lymphoma and Hodgkin’s disease among White firefighters but not among African American firefighters have been reported.5 
 
Because of the retrospective method used in this case–control study, a racial disparity in recall bias might exist. A comparison of the odds ratios of occupational exposures for these selected cancers in presumptive cases denied by pathological review with those in confirmed cases in both races may provide some clues. 
 
The authors suggested that the results may reflect racial disparities in levels of exposure to occupational carcinogens. But we could not find in the article any results to support the hypothesis that exposure levels were higher in African American men than in White men. Do the authors have such data? We hope that better-designed studies in the future can test this hypothesis.