Mortality among a cohort of US man-made mineral fiber workers: 1985 follow-up

Our plain-English summary of Mortality among a cohort of US man-made mineral fiber workers: 1985 follow-up, by G.M. Marsh, P.E. Enterline, R.A. Stone, et al (Journal of Occupational Medicine., 1990).

The study

• Authors: G.M. Marsh, P.E. Enterline, R.A. Stone, V.L. Henderson
• Journal: Journal of Occupational Medicine.
• Published: 1990;32(7):594-604
• Cited by: 84 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002006).

Abstract

This 1983 to 1985 update of an earlier study examined the mortality experience of 16,661 man-made mineral fiber workers employed 1 year or more (6 months for two plants) during 1945 to 1963 (1940 to 1963 for one plant) at one or more of 17 US manufacturing plants. Using local death rates to estimate expected deaths there was a small statistically significant (P less than .05) excess in all malignant neoplasms (standardized mortality ratio [SMR] = 108.3) and in respiratory cancer (SMR = 112.1) for the total period 1946 to 1985. For respiratory cancer the excess was greatest for mineral wool workers. For glass wool workers and glass filament workers respiratory cancer SMR values were much lower. For workers exposed in the production of small-diameter fibers, the overall respiratory cancer SMR was slightly elevated but lower than in earlier reports. A total of four malignant mesotheliomas have now been noted on death certificates. Two of these were coded to the International Classification of Disease rubrics used to estimate 1.45 expected mesothelioma deaths for the total study. Overall, the evidence of a relationship between exposure to man-made mineral fibers and respiratory cancer appears to be somewhat weaker than in the previous update.

In plain English

This study updated, through 1985, the death records of 16,661 male production and maintenance workers. They were employed during 1945 to 1963 (1940 to 1963 at one plant) at 11 fibrous glass plants and six mineral wool plants in the United States. The study concerned man-made mineral fibers, not asbestos. Compared with local death rates for 1946 to 1985, the workers had a small, statistically significant excess of deaths from all cancers (SMR 108.3) and from respiratory cancer (SMR 112.1). The respiratory cancer excess was greatest among mineral wool workers. Fibrous glass workers as a group showed no significant excess (SMR 108.9). Respiratory cancer did not rise with longer employment. Statistical modeling found no significant link with individual workers' estimated cumulative or average fiber exposure. Four deaths were noted on death certificates as malignant mesothelioma. Two of these were coded under the categories for which 1.45 deaths were expected. The authors suggested that differences among mineral wool plants might relate to the use of slag. They concluded that the evidence linking these fibers to respiratory cancer appeared somewhat weaker than in their previous update.

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: Historical (retrospective) cohort mortality study; a 3-year update, through 1985, of an earlier study, comparing observed deaths with expected deaths (standardized mortality ratios, SMRs) based on local and national US rates, with Poisson regression modeling
• Who was studied: 16,661 male production or maintenance workers with 1 year or more of work during 1945 to 1963 (6 months for two plants; 1940 to 1963 for plant 9) at 11 fibrous glass and six mineral wool plants in the US, followed for deaths from 1946 through 1985. Vital status was found for all but 395 workers.
• Exposure: Man-made mineral fibers: fibrous glass wool, fibrous glass filament, plants producing both, and mineral wool (rock and slag wool). Some workers made small-diameter fibers (less than 1.5 µm). Individual exposure was estimated from plant dust-zone and time-period matrices, expressed only as airborne fibers less than 3 µm in diameter and more than 5 µm long counted by phase contrast optical microscopy.
• Main results:
  • Total cohort, 1946 to 1985, local rates: small statistically significant (P < .05) excesses in all malignant neoplasms (SMR 108.3) and in respiratory cancer (SMR 112.1).
  • The respiratory cancer excess was greatest for mineral wool workers. Among mineral wool plants, the estimated respiratory cancer SMR for plants 7, 12, 13 and 17 combined (180.9) was significantly higher (P < .01) than for plants 3 and 8 combined (85.8).
  • All fibrous glass workers: overall respiratory cancer SMR of 108.9 (local rates), not significantly elevated.
  • For none of the five plant groups was there a positive relationship between respiratory cancer and duration of employment.
  • There was no evidence of a direct relationship between respiratory cancer and either cumulative fiber exposure (lagged 5 years) or average intensity of exposure.
  • In the Poisson model for the total cohort, none of the factors considered (production process, year of hire, time since first employment, duration of employment) was statistically significant, although the overall respiratory cancer SMR of 112.1 was.
  • Fibrous glass workers ever exposed to small-diameter fibers (1015 workers at plants 1, 6, 9 and 10) had respiratory cancer SMRs of 102.8, 98.8, 127.9 and 72.0 by plant. Never-exposed workers had SMRs of 73.7, 111.2, 113.3 and 0.
  • Four deaths were noted as malignant mesothelioma. Two were coded as underlying cause under the ICD categories (pleura, mediastinum and unspecified sites) for which 1.45 deaths were expected. Slides were obtained for only one of the three earlier cases, and the US Mesothelioma Panel did not consider that case a mesothelioma.
  • Nonmalignant respiratory disease (excluding influenza and pneumonia), compared with US rates: statistically significant excesses of 35.4% and 29.7% in the two earlier follow-up periods fell to a statistically nonsignificant 11.5% excess in 1983 to 1985.
  • The authors suggested that the difference between mineral wool plants may be related to the use of slag rather than rock. They noted that slag contains possible carcinogens such as arsenic and various metals.
• The authors' conclusion: The authors concluded that, overall, the evidence of a relationship between exposure to man-made mineral fibers and respiratory cancer appeared somewhat weaker than in the previous update.
• Limitations the authors state:
  • A complete exposure-response evaluation was not possible because there were no data on workplace contaminants other than fibers.
  • Only white male death rates were used, because race was unknown for more than 30% of the cohort.
  • Cause-specific SMRs were slightly understated because death certificates could not be found for 121 deceased workers.
  • It was not clear whether respiratory cancer excesses among shorter-term workers were related to occupational or nonoccupational factors or both.
  • The history of rock and slag use at plants 3 and 8 was uncertain.

Topics

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Neoplasm, standardized mortality ratio (SMR), Mesothelioma, Death Certificate.

Related studies

• Preliminary results from a cohort of workers exposed to wollastonite in a Finish limestone quarry — M.S. Huuskonen, J. Järvisalo, et al. (1983)
• Assessments of lung digestion methods for recovery of fibers — D.B. Warheit, H.C. Hwang, 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)
• Cytotoxicity of respirable dusts from industrial minerals: comparison of two naturally occurring and two man-made silicates — D. Nadeau, L. Fouquette-Couture, et al. (1987)
• Historical cohort study of US man-made vitreous fiber production workers: II. Mortality from mesothelioma — G.M. Marsh, M.J. Gula, et al. (2001)
• Investigation on the durability of man-made vitreous fibers in rat lungs — B. Bellmann, H. Muhle, et al. (1994)

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