Re: "Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry"

Our plain-English summary of Re: "Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry", by M.J. Mirliss (American Journal of Epidemiology, 1998).

The study

• Author: M.J. Mirliss
• Journal: American Journal of Epidemiology
• Published: 1998;148(3):307-9
• Type of article: Comment, Letter
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This is a letter to the editor, not a new study. The author commented on a 1997 study by Checkoway and colleagues of deaths among diatomaceous earth workers at a California plant. That study had reported a dose-response link between crystalline silica and lung cancer deaths. The author noted that silica exposures before 1944 were estimated from later measurements with a scaling factor of 2.5 (log scale), which the author called somewhat arbitrary. According to the author, this placed most workers hired before 1930 in the highest exposure category. Citing historical sources, the author argued that early dust likely held little crystalline silica. The author also cited evidence that pre-1930 workers were exposed to asbestos. In a table adapted from the original study, the highest cumulative exposure category had 20 lung cancer deaths and a rate ratio of 2.15 (95% confidence interval 1.08-4.28), compared with the lowest category (under 0.5 mg/m3-years). Citing a separate additional analysis by the original authors, the author noted that 8 of these workers were hired before 1930. The author concluded that the effect of exposure misclassification should be examined more fully.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Letter to the editor commenting on a published retrospective mortality study; no new data collected
• Who was studied: No population studied by the author; the letter discusses the cohort of diatomaceous earth workers at a California plant studied by Checkoway et al. (1997)
• Exposure: Crystalline silica (as estimated in the original study), with comments on asbestos exposure among workers hired before 1930
• Main results:
  • The author stated that job exposures before 1944 in the original study were estimated with a somewhat arbitrary scaling factor of 2.5 (log scale)
  • According to the author, this multiplier placed most early workers in higher exposure categories and most workers hired before 1930 in the highest category
  • The author stated that through 1929, natural (uncalcined) products made up more than 60 percent of production at the plant
  • The author argued that the earliest dust exposures likely contained little crystalline silica
  • The author stated there is evidence that pre-1930 workers were exposed to asbestos, although the original study reported little asbestos exposure in that period
  • The author cited a comparison showing large overlap between earlier subjective exposure ratings and the newer semiquantitative estimates for the same cohort, suggesting possible misclassification
  • In a table adapted from table 6 of the original study (lung cancer mortality, lagged 15 years), the highest cumulative exposure category had 20 deaths and a rate ratio of 2.15 (95% CI 1.08-4.28), compared with the reference category of under 0.5 mg/m3-years (rate ratio 1.00)
  • Citing a separate additional analysis by the original study's authors (reference 9), not the published table, the author noted that 8 of the 20 deaths in the highest category were among workers hired before 1930
  • The author stated that the original study's findings are driven by the increased risk in the highest exposure group
• The authors' conclusion: The author concluded that the effect of exposure misclassification on the original study's findings should be examined more fully by the scientific community

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Dose-response relationship, Lung Cancer.

Related studies

• Re: "Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry" — G.W. Gibbs (1998)
• Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry — H. Checkoway, N.J. Heyer, et al. (1997)
• Extended follow-up of lung cancer and non-malignant respiratory disease mortality among California diatomaceous earth workers — L.G. Gallagher, R.M. Park, et al. (2015)
• Mortality from non-malignant respiratory disease in the fibreglass manufacturing industry — L. Chiazze, D.K. Watkins, et al. (2002)
• Reanalysis of mortality from lung cancer among diatomaceous earth industry workers, with consideration of potential confounding by asbestos exposure — H. Checkoway, N.J. Heyer, et al. (1996)
• Radiographic evidence of silicosis risk in the diatomaceous earth industry — J.M. Hughes, H. Weill, et al. (1998)

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