Dust exposure and mortality in an American chrysotile textile plant

Our plain-English summary of Dust exposure and mortality in an American chrysotile textile plant, by A.D. McDonald, J.S. Fry, A.J. Woolley, et al (British Journal of Industrial Medicine, 1983).

The study

• Authors: A.D. McDonald, J.S. Fry, A.J. Woolley, J. McDonald
• Journal: British Journal of Industrial Medicine
• Published: 1983;40(4):361-7
• Cited by: 121 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000625).

Abstract

Three parallel cohort studies of asbestos factory workers were undertaken to investigate the effects of mineral fibre type and industrial process on malignant mesothelioma, respiratory cancer, and asbestosis. This report describes the mortality of a cohort of 2543 men, defined as all those employed for at least a month from 1938 to 1958 in a textile plant in South Carolina in which chrysotile was the only type of asbestos used. Of these, 863 men (34%) had died before 31 December 1977, one from malignant mesothelioma. Twenty one deaths were ascribed to asbestosis and 66 to cancer of the lung. Compared with the number expected from South Carolina, there was an excess of 30 deaths from respiratory cancer (ICD 160-164) in men 20 or more years after first employment (SMR 199.5). In men employed five years or more, no SMRs for this category rose above 300. Individual exposures were estimated (in mpcf X years) from recorded environmental measurements. Life table analyses and "log-rank" (case-control) analyses both showed a steep linear exposure-response that was some 50-fold greater at similar accumulated dust exposures than in Canadian chrysotile mining and milling. These findings agree closely with those from another study in this plant and confirm that mesothelioma is rarely associated with chrysotile exposure. Cigarette smoking habits did not greatly differ between the textile workers and the Canadian miners and millers. The far greater risk of lung cancer in the textile industry, if not attributable to other identified cocarcinogens, may be related to major differences in the size distribution of fibres in the submicroscopic range which are not detected by the usual fibre or particle counting procedures.

In plain English

The authors followed 2543 men employed for at least a month before 1959 at a South Carolina asbestos textile plant; by the end of 1977, 863 had died. The plant used mainly chrysotile, with small amounts of crocidolite yarn and experimental amosite. Exposures were estimated from over 5000 past dust samples, in millions of particles per cubic foot (mpcf) times years. Of deaths of known age, 66 were certified as lung cancer and 21 as pneumoconiosis. Among men 20 or more years after first employment, respiratory cancer deaths (59) were about twice those expected from South Carolina rates. Within the plant, lung cancer risk rose in a straight line with accumulated dust: men with 80 or more mpcf-years had a relative risk of 15.00 (6 deaths) versus men under 10. One death was ascribed to mesothelioma, stated as peritoneal, with no autopsy. The authors concluded that the lung cancer slope was 50 times steeper than in Quebec chrysotile miners and millers. They judged that errors could hardly reduce this below about 10-fold, and speculated that very fine fibres might explain it.

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: Retrospective cohort mortality study, analysed two ways: standardized mortality ratios (SMRs) against South Carolina death rates, and an internal case-control (Mantel-Haenszel) comparison within the cohort. It was one of three parallel factory studies.
• Who was studied: 2543 men employed for at least one calendar month before 1 January 1959 at an asbestos textile plant in South Carolina, with vital status traced to 31 December 1977. Of these, 863 (34%) had died, and death certificates were found for 827 (95%). The paper analysed the 857 male deaths of known age. Women (1175) were in the cohort but were not analysed in this paper.
• Exposure: Chrysotile, mainly from Canada but also Rhodesia, used in textile processes (preparation, carding, spinning, winding, twisting, weaving). A small amount of imported crocidolite yarn (less than 2000 pounds a year) was used from the early 1950s until 1972, and a very small amount of amosite was tried experimentally in carding in the late 1950s. Individual exposures were estimated in millions of particles per cubic foot (mpcf) and mpcf-years, from over 5000 environmental samples taken since 1930, mainly by the impinger method.
• Main results:
  • Of 857 male deaths of known age, 66 were certified as lung cancer (ICD 162-164) and 21 as pneumoconiosis (ICD 523-4).
  • In men 20 or more years after first employment (complete cohort), there were 59 respiratory cancer deaths (ICD 160-164), SMR 199.5. For all causes there were 570 deaths, SMR 127.4. For respiratory cancer, the SMR was 304.1 in men with 5 to under 20 years of service and 317.3 in men with 20 or more years.
  • Respiratory cancer SMRs rose with dust exposure accumulated to 10 years before death: from 143.1 (31 deaths, under 10 mpcf-years) to 1031.9 (8 deaths, 80 or more mpcf-years).
  • In the internal Mantel-Haenszel analysis, lung cancer relative risks, compared with men under 10 mpcf-years, were 0.98 for 10-19, 2.95 for 20-39, 4.32 for 40-79 and 15.00 for 80 or more mpcf-years. These were based on 25, 3, 8, 7 and 6 deaths. The authors reported a statistically significant linear trend for lung cancer, pneumoconiosis and all causes, but no convincing association for abdominal cancers.
  • Only one death was ascribed to mesothelioma: a man who was a mule spinner from 1933 to 1955. The tumour was stated to be peritoneal, but there was no necropsy.
  • The slope of the lung cancer exposure-response line in these textile workers was 50 times steeper than that observed in chrysotile miners and millers. The findings agreed closely with those of Dement et al. in a smaller cohort from the same plant.
  • In a 1982 survey, 44 (18%) of 246 men born before 1930 were non-smokers. The authors found no major difference in smoking compared with the Quebec mining cohort.
• The authors' conclusion: The authors concluded that there are two well established linear relationships between chrysotile dust exposure and lung cancer risk, one 50 times steeper than the other. In their view, possible sources of error could hardly reduce this below about 10-fold. If cocarcinogens can be discounted, they speculated that the distribution of very fine fibres, seen only by electron microscope, may differ between textile manufacture and mining and milling.
• Limitations the authors state:
  • Very high exposures from beating dust filter bags in the baghouse and moving asbestos with pitch forks on the mezzanine could not be assessed or linked to individual workers, and were not included in any analysis.
  • South Carolina mortality rates were probably an imperfect basis for comparison, so the SMRs are probably somewhat inflated.
  • The exposure data were not independent of those used by Dement et al., although the mortality data were.
  • Dust was measured as impinger particle counts, and converting these to fibre counts is uncertain.
  • Information on smoking was fragmentary.
  • The Mantel-Haenszel analysis included fewer deaths than the SMR analysis (for example 490 versus 570 from all causes) because no matching control could be found for some.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestos textiles, Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Malignant Mesothelioma, Mesothelioma, Habit, Lung Cancer.

Related studies

• Dust exposure and mortality in an American factory using chrysotile, amosite, and crocidolite in mainly textile manufacture — A.D. McDonald, J.S. Fry, et al. (1983)
• Dust exposure and mortality in an American chrysotile asbestos friction products plant — A.D. McDonald, J.S. Fry, et al. (1984)
• Increased lung cancer mortality among chrysotile asbestos textile workers is more strongly associated with exposure to long thin fibres — D. Loomis, J.M. Dement, et al. (2012)
• Follow-up study of chrysotile asbestos textile workers: cohort mortality and case-control analyses — J.M. Dement, D.P. Brown, et al. (1994)
• Lung cancer mortality in North Carolina and South Carolina chrysotile asbestos textile workers — L. Elliott, D. Loomis, et al. (2012)
• Cause-specific mortality in a Chinese chrysotile textile worker cohort — X. Wang, S. Lin, et al. (2013)

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