A case-control study of malignant and non-malignant respiratory disease among employees of a fiberglass manufacturing facility. II. Exposure assessment

Our plain-English summary of A case-control study of malignant and non-malignant respiratory disease among employees of a fiberglass manufacturing facility. II. Exposure assessment, by L. Chiazze, D.K. Watkins, C. Fryar, et al (British Journal of Industrial Medicine, 1993).

The study

• Authors: L. Chiazze, D.K. Watkins, C. Fryar, J. Kozono
• Journal: British Journal of Industrial Medicine
• Published: 1993;50(8):717-25
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A case-control study of malignant and non-malignant respiratory disease among employees of the Owens-Corning Fiberglas Corporation's Newark, Ohio plant was undertaken. The aim was to determine the extent to which exposures to substances in the Newark plant environment, to non-workplace factors, or to a combination may play a part in the risk of mortality from respiratory disease among workers in this plant. A historical environmental reconstruction of the plant was undertaken to characterise the exposure profile for workers in this plant from its beginnings in 1934 to the end of 1987. The exposure profile provided estimates of cumulative exposure to respirable fibres, fine fibres, asbestos, talc, formaldehyde, silica, and asphalt fumes. Employment histories from Owens-Corning Fiberglas provided information on employment characteristics (duration of employment, year of hire, age at first hire) and an interview survey obtained information on demographic characteristics (birthdate, race, education, marital state, parent's ethnic background, and place of birth), lifetime residence, occupational and smoking histories, hobbies, and personal and family medical history. Matched, unadjusted odds ratios (ORs) were used to assess the association between lung cancer or non-malignant respiratory disease and the cumulative exposure history, demographic characteristics, and employment variables. Only the smoking variables and employment characteristics (year of hire and age at first hire) were statistically significant for lung cancer. For non-malignant respiratory disease, only the smoking variables were statistically significant in the univariate analysis. Of the variables entered into a conditional logistic regression model for lung cancer, only smoking (smoked for six months or more v never smoked: OR = 26.17, 95% confidence interval (95% CI) 3.316-206.5) and age at first hire (35 and over v less than 35: OR = 0.244, 95% CI 0.083-0.717) were statistically significant. There were, however, increased ORs for year of employment (first hired before 1945 v first hire after 1945: OR = 1.944, 95% CI 0.850-4.445), talc (cumulative exposure >1000 fibres/ml days v never exposed: OR = 1.355, 95% CI 0.407-5.515), and asphalt fumes (cumulative exposure >0.01 mg/m(3) days v never exposed: OR 1.131, 95% CI 0.468-2.730). For non-malignant respiratory disease, only the smoking variable was significant in the conditional logistic regression analysis (OR = 2.637, 95% CI 1.146-6.069). There were raised ORs for the higher cumulative exposure categories for respirable fibres, asbestos, silica, and asphalt fumes. For both silica and asphalt fumes, ORs were more than double the reference groups for all exposure categories. A limited number of subjects were exposed to fine fibres. The scarcity of cases and controls limits the extent to which analyses for fine fibre may be carried out. Within those limitations, among those who had worked with fine fibre, the unadjusted, unmatched OR for lung cancer was (1.0 (95% CI 0.229-4.373) and for non-malignant respiratory disease, the OR was 1.5 (95% CI 0.336-6.702). The unadjusted OR for lung cancer for exposure to fine fibre was consistent with that for all respirable fibre and does not suggest an association. For non-malignant respiratory disease, the unadjusted OR for fine fibre was opposite in direction from that for all respirable fibres. Within the limitations of the available data on fibre, there is o suggestion that exposure to fine fibre has resulted in an increase in risk of lung cancer. The increased OR for non-malignant respiratory disease is inconclusive. The results of this population, in this place and time, neither respirable fibres nor any of the substances investigated as part of the plant environment are statistically significant factors for lung cancer risk although there are increased ORs for exposure to talc and asphalt fumes. Smoking is the most important factors in risk for lung cancer in this population. The situation is less clear for non-malignant respiratory disease. Unlike lung cancer, non-malignant respiratory represents a constellation of outcomes and not a single well defined end point. Although smoking was the only statistically significant factor for non-malignant respiratory disease in this analysis, the ORs for respirable fibres, asbestos, silica, and asphalt fumes were greater than unity for the highest exposure categories. Although the raised ORs for these substances may represent the results of a random process, they may be suggestive of an increased risk and require further investigation.

In plain English

This case-control study examined lung cancer and non-malignant respiratory disease deaths among Owens-Corning Fiberglas workers in Newark, Ohio. Subjects came from a cohort employed at least one year in 1940 to 1962, followed to 1982. Matched interview-data analyses had up to 144 lung cancer cases (260 controls) and 101 non-malignant cases (183 controls). Cumulative exposures to respirable fibres, asbestos, talc, formaldehyde, silica and asphalt fumes were estimated from reconstructed plant history. For lung cancer, after adjustment, only smoking six months or more versus never (OR 26.17, 95% CI 3.316 to 206.5) and first hire at 35 or older versus younger (OR 0.244, 95% CI 0.083 to 0.717) were significant. No exposure was significant. For non-malignant respiratory disease, only smoking was significant (OR 2.637, 95% CI 1.146 to 6.069). Highest-category odds ratios for respirable fibres, asbestos, silica and asphalt fumes exceeded 1, non-significantly. Small numbers limited fine-fibre analyses. The authors concluded no studied plant substance was a statistically significant lung cancer factor here, though talc and asphalt fume odds ratios were increased. They said raised non-malignant odds ratios may reflect chance or suggest a relation.

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: Case-control study with cases and controls drawn from a historical cohort mortality study, combined with a historical environmental reconstruction of exposures; matched odds ratios and conditional logistic regression
• Who was studied: Production and maintenance workers of the Owens-Corning Fiberglas plant in Newark, Ohio, employed at least one year between 1940 and 1962 and followed to the end of 1982. For matched analyses of interview data, up to 144 lung cancer cases (260 controls) and 101 non-malignant respiratory disease cases (183 controls) were available. Controls were matched on year of birth and survival.
• Exposure: Estimated cumulative exposure (days in each process times the midpoint of an estimated exposure range, summed over processes) to respirable fibres, fine fibres, asbestos, talc, formaldehyde, respirable silica, asphalt fumes and total particulate. An exposure assessment committee assigned these estimates from the plant's engineering history. Asbestos fibre type was not specified.
• Main results:
  • Lung cancer, conditional logistic regression: only two variables were statistically significant. These were smoking (smoked six months or more vs never smoked, OR 26.17, 95% CI 3.316 to 206.5) and age at first hire (35 and over vs under 35, OR 0.244, 95% CI 0.083 to 0.717).
  • Lung cancer: none of the exposure variables showed a statistically significant increase in odds ratio
  • Lung cancer: higher exposures to talc (OR 1.355, 95% CI 0.407 to 4.515) and asphalt fumes (OR 1.131, 95% CI 0.468 to 2.730) had higher odds ratios, which were not statistically significant
  • Lung cancer: those hired before 1945 had a raised but not significant adjusted OR of 1.944 (95% CI 0.851 to 4.445)
  • Asbestos, highest cumulative exposure category (matched, unadjusted): lung cancer OR 0.553 (95% CI 0.152 to 2.007) and non-malignant respiratory disease OR 1.585 (95% CI 0.479 to 5.245). Neither was statistically significant.
  • Non-malignant respiratory disease, conditional logistic regression: only smoking (smoked six months or more vs never smoked) was statistically significant, with OR 2.637 (95% CI 1.146 to 6.069)
  • Non-malignant respiratory disease: odds ratios were raised but not statistically significant for the highest silica category (OR 3.247, 95% CI 0.544 to 19.40) and for asphalt fumes above 0.01 mg/m3 days (OR 2.071, 95% CI 0.743 to 5.776)
  • 44 subjects had worked in fine fibre processes: 10 lung cancer cases, 10 non-malignant respiratory disease cases and 24 controls
  • Among those who had worked in fine fibre (unadjusted, unmatched): lung cancer OR 1 (95% CI 0.229 to 4.373) and non-malignant respiratory disease OR 1.5 (95% CI 0.336 to 6.702)
  • Two silicosis deaths had no silica exposure at Newark. Removing them and their controls gave results similar to the main non-malignant analysis.
• The authors' conclusion: The authors concluded that, for this population in this place and time, neither respirable fibres nor any other plant substance studied was a statistically significant factor for lung cancer risk, although odds ratios were increased for talc and asphalt fumes. They concluded that smoking was the most important lung cancer factor.
• Limitations the authors state:
  • The raised odds ratios for non-malignant respiratory disease may be due to chance, though they could suggest a relation
  • Non-malignant respiratory disease is a group of outcomes, not a single well-defined end point
  • There were few records for quantitative exposure assessment of early processes
  • Few cases and controls limited the fine fibre analyses
  • Smoking information was missing for some fine-fibre subjects, making adjustment unreliable
  • Eight non-malignant respiratory disease deaths had silicosis coded as the underlying cause, which complicated the analysis

Topics

Medical terms in this study, explained in our Lexicon: Case-Control Study, Owens-Corning Fiberglas, Cumulative Exposure, Talc, Odds Ratio, Lung Cancer, confidence interval.

Related studies

• Mortality from non-malignant respiratory disease in the fibreglass manufacturing industry — L. Chiazze, D.K. Watkins, et al. (2002)
• Asbestos-related disease in employees of a steel mill and a glass bottle-manufacturing plant — R.S. Kronenberg, J.L. Levin, et al. (1991)
• Asbestos-related disease in employees of a steel mill and a glass bottle manufacturing plant — R.S. Kronenberg, J.L. Levin, et al. (1991)
• Historical cohort study of US man-made vitreous fiber production workers: I. 1992 fiberglass cohort follow-up: initial findings — G.M. Marsh, A.O. Youk, et al. (2001)
• Man-made vitreous fibers and risk of respiratory system cancer: a review of the epidemiologic evidence — I.M. Lee, C.H. Hennekens, et al. (1995)
• Constrictive pericarditis in a patient with fiberglass lung disease: a case report — C.Y. Hsu, H.Y. Chen, et al. (2024)

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