Mortality from non-malignant respiratory disease in the fibreglass manufacturing industry

Our plain-English summary of Mortality from non-malignant respiratory disease in the fibreglass manufacturing industry, by L. Chiazze, D.K. Watkins, C. Fryar, et al (Occupational and Environmental Medicine, 2002).

The study

• Authors: L. Chiazze, D.K. Watkins, C. Fryar, W. Fayerweather, J. Kozono, V. Biggs
• Journal: Occupational and Environmental Medicine
• Published: 2002;59(6):369-71
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To investigate the question of whether there is an association between workplace exposures and sociodemographic factors and mortality from non-malignant respiratory disease excluding influenza and pneumonia (NMRDxIP) among workers in a fibreglass wool manufacturing facility.

Methods: A case-control study with cases and controls derived from deaths recorded from the Kansas City plant in the Owens Corning mortality surveillance system. The cases are defined as decedents with NMRDxIP as the underlying cause of death. Matched, unadjusted odds ratios (ORs) were used to assess any association between NMRDxIP and cumulative exposure history and sociodemographic factors individually. Matched, adjusted ORs were obtained by conditional logistic regression to estimate the effect of any one variable while controlling for the effect of all the others.

Results: Results of the unadjusted analysis, considering variables one at a time, yielded no significant associations between NMRDxIP and any of the exposure or sociodemographic variables. The smoking OR was substantially increased (OR 5.09; 95%CI 0.65 to undeterimed). Also, there were no significant variables in a conditional logistic regression analysis in which all variables were simultaneously adjusted. ORs for respirable glass fibres were below unity at all concentrations of exposure in the adjusted analysis. For respirable silica there was no consistent relation across all exposure levels. The ORs increased through the first three exposure concentrations but decreased for the highest exposure. However, ORs although not significant, are greater than unity for all respirable concentrations of silica exposure.

Conclusions: The findings for Kansas City show no association between respirable glass fibres and NMRDxIP. The adjusted ORs for all exposures to respirable fibres were less than unity. On the other hand, the ORs for silica exposures were all above unity although there was no clear dose-response relation and none of the ORs were significant. Exposures for all substances considered were very low. Further, given the number of cases and controls, the statistical power to detect relatively small increases in risk, if any increase truly exited, was relatively low. The ORs for exposures to silica were all above unity although there was no clear dose-response relation and none of the ORs were significant. These raised ORs for silica suggest that continued surveillance would be prudent.

In plain English

This case-control study looked at deaths from non-malignant respiratory disease excluding influenza and pneumonia (NMRDxIP) among workers at an Owens Corning fibreglass wool plant in Kansas City. The cases were 30 white men, all employed 10 or more years, whose underlying cause of death was NMRDxIP. They were compared with 133 matched controls drawn from other deaths at the plant. An expert committee estimated each worker's cumulative exposure to respirable glass fibres, asbestos, talc, respirable silica and formaldehyde.

In the unadjusted analysis, no exposure was significantly related to NMRDxIP. Compared with no asbestos exposure, the odds ratios were 0.97 (95% CI 0.13 to 5.13) for the lower and 1.10 (0.41 to 2.85) for the higher asbestos category. The odds ratio for smokers versus never-smokers was 5.09 (95% CI 0.65 to undetermined), which was also not significant. In the adjusted analysis no variable was significant. Odds ratios for respirable glass fibres were below 1, and those for silica were above 1 at every level without a dose-response pattern.

The authors concluded there was no association between respirable glass fibres and NMRDxIP. They noted that exposures were low and that statistical power was low.

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: Matched case-control study using deaths recorded in a company mortality surveillance system, analysed with exact conditional logistic regression (unadjusted and adjusted odds ratios)
• Who was studied: 30 white men who had worked at the Owens Corning Kansas City fibreglass wool insulation plant and whose underlying cause of death was NMRDxIP, all employed 10 or more years (22 of the 30 coded as chronic airways obstruction). They were compared with 133 controls who died of other causes (not NMRDxIP or respiratory cancer), matched on year of birth and survival time, drawn from a death register covering deaths from 1970 onward.
• Exposure: Cumulative exposure-days (estimated concentration multiplied by days of exposure) to respirable glass fibres, asbestos (fibre type not specified), talc, respirable silica and formaldehyde, estimated by an expert committee for each plant process. Smoking, drinking, education, marital status and income came from interviews.
• Main results:
  • In the unadjusted analysis, no exposure variable was significantly related to NMRDxIP.
  • Unadjusted, respirable glass fibres at 100 to 299.99 fibres/ml exposure-days, compared with under 100: OR 2.24 (95% CI 0.54 to 10.97), not significant.
  • Unadjusted, respirable glass fibres at the highest exposure (over 300), compared with under 100: OR 0.79 (95% CI 0.20 to 3.52).
  • Unadjusted, the ORs for asbestos (and for formaldehyde) were not significant and close to 1.
  • Unadjusted asbestos ORs compared with no asbestos exposure: 0.97 (95% CI 0.13 to 5.13) at 0.03 to 0.99 fibres/ml exposure-days, and 1.10 (95% CI 0.41 to 2.85) at more than 1 (maximum 66.7).
  • Unadjusted, respirable silica ORs were above 1 at all exposure levels compared with no exposure (1.17, 1.58, 2.27, 1.33), rising through the first three levels and falling at the highest. None were significant.
  • Unadjusted OR for any talc exposure: 0.66 (95% CI 0.24 to 1.64), not significant.
  • Unadjusted, smokers (6 months or more) compared with never-smokers: OR 5.09 (95% CI 0.65 to undetermined), not significant. This was based on 22 observations and 6 informative strata.
  • Six variables were entered into the adjusted model: education, marital status, smoking, respirable fibres, talc and respirable silica. Asbestos was not among them, and income was excluded for scarcity of data.
  • In the adjusted analysis (68 observations, 19 informative strata), no variable was significant. The adjusted smoking OR was 1.88 (95% CI 0.24 to infinity).
  • Adjusted ORs for respirable glass fibres were below 1 compared with the under-100 group: 0.63 (95% CI 0.01 to 19.37) at 100 to 299.99 and 0.49 (95% CI 0.01 to 14.19) above 300.
  • Adjusted ORs for respirable silica were above 1 at all levels compared with no exposure (1.01, 1.71, 3.96, 1.77), with no evidence of a dose-response relation. None were significant.
• The authors' conclusion: The authors concluded that the findings for Kansas City showed no association between respirable glass fibres and NMRDxIP.
• Limitations the authors state:
  • Exposure concentrations for all substances studied were low.
  • Given the number of cases and controls, statistical power to detect small increases in risk was low. The authors state that three times as many cases would have been needed to have an 80% chance of detecting a doubling of risk in the lowest exposure category.
  • The adjusted analysis rested on only 68 observations and 19 informative strata, and the authors said its results should be interpreted with caution.
  • The authors stated that a small study such as this cannot give definitive answers about any relation between respirable glass fibres and NMRDxIP.

Topics

Medical terms in this study, explained in our Lexicon: Case-Control Study, Odds Ratio, Cumulative Exposure, Dose-response relationship.

Related studies

• A case-control study of malignant and non-malignant respiratory disease among employees of a fiberglass manufacturing facility. II. Exposure assessment — L. Chiazze, D.K. Watkins, et al. (1993)
• Re: "Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry" — G.W. Gibbs (1998)
• Re: "Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry" — M.J. Mirliss (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)
• Relationships (I) of International Classification of High-resolution Computed Tomography for Occupational and Environmental Respiratory Diseases with the ILO International Classification of Radiographs of Pneumoconioses for parenchymal abnormalities — T. Tamura, N. Suganuma, et al. (2015)
• Nonmalignant respiratory disease mortality among woodworkers participating in the American Cancer Society Cancer Prevention Study-II (CPS-II) — P.A. Demers, S.D. Stellman, et al. (1998)

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