Lung function and radiographic change in chrysotile workers in Swaziland

Our plain-English summary of Lung function and radiographic change in chrysotile workers in Swaziland, by M. McDermott, M.M. Bevan, P.C. Elmes, et al (British Journal of Industrial Medicine, 1982).

The study

• Authors: M. McDermott, M.M. Bevan, P.C. Elmes, J.T. Allardice, A.C. Bradley
• Journal: British Journal of Industrial Medicine
• Published: 1982;39(4):338-43
• Cited by: 9 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. 000690).

Abstract

The effect on lung function and radiographic indices of exposure to chrysotile asbestos was investigated by cross-sectional studies in two groups of men at Havelock Mine, Swaziland. The first group consisted of 214 employees and ex-employees, mean age 52, who had been employed for at least 10 years, and whose dust exposure ranged from minimal for surface workers to very heavy for those in the grading and bagging sections of the mill. In this group 29% had category 1 or more simple pneumoconiosis and 4.5% category 2 or more. For surface and mine workers, the estimated annual deterioration in FEV1 and FVC and the increase in category of pneumoconiosis was similar to that due to age alone, while the heaviest exposure almost doubled the decline in lung function and trebled the rate of progression of pneumoconiosis. The second group consisted of 224 men, mean age 33, all currently working in the mill and having been employed there for at least a year. In this group 30% had category 1 or more simple pneumoconiosis, and 2.7% category 2. Exposure in the dustiest sections of the mill more than doubled the estimated annual decline in lung function and doubled the rate of progression of pneumoconiosis.

In plain English

This article reported two cross-sectional studies of Swazi men at the Havelock chrysotile asbestos mine, Swaziland. The first included 214 current and former employees with at least 10 years' employment (mean age 52); the second, 224 current mill workers (mean age 33). Dust was unmeasured before 1976, so jobs were placed in six rough exposure categories, J1 (lowest) to J6 (highest). In the first study, 29% had category 1 or more pneumoconiosis on chest X-ray and 4.5% category 2 or more. In the second, 30% had category 1 or more and 2.7% category 2. In the first study, categories J1 to J4 showed no significant effect. Its regression estimates, from single measurements, linked work in the dustiest categories, J5 and J6, to greater estimated yearly declines in lung function (FEV1 and FVC) and more X-ray change than age alone; the J5 effect on FEV1 was significant only with J1 to J4 excluded. Of the high-exposure group, 43% had category 1 or more, versus 22% of the low-exposure group. The authors concluded past mill dust levels had been unacceptably high.

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: Two cross-sectional studies, about five months apart, analysed separately. Annual changes in lung function and X-ray findings were estimated by multiple regression on age and years in each exposure category, not measured by following workers over time.
• Who was studied: Swazi men at Havelock Mine, Swaziland. First study: 214 employees and ex-employees employed 10 years or more before 1970, mean age 52, mean employment 25 years. Europeans and men exposed to coal or silica were excluded. Second study: 224 current mill employees employed at least a year, mean age 33, mean employment eight years.
• Exposure: Chrysotile asbestos dust. Jobs were assigned to six categories, J1 to J6, in rising order of dust exposure. The dustiest were mill jobs. J5 covered the treatment, conditioning and sample plants, and the waste dump before 1970. J6 covered the grading and recovery plants, fibre storage and bagging. No dust measurements were available before 1976. Past mill levels were judged from workers' recollections, compared against a present section with about 50 fibres/ml.
• Main results:
  • First study (214 men): 29% had category 1 or more pneumoconiosis, 4.5% category 2 or more, and 1.5% category 3.
  • First study: exposure in categories J1 to J4 produced no significant deterioration in any lung function or X-ray index, while all indices deteriorated significantly with age.
  • First study, analysis with all six categories: exposure in J5 and J6 significantly reduced FVC and increased the profusion of small opacities. FEV1 was significantly reduced in J6 only.
  • First study: when J1 to J4 were excluded from the analysis, some significance levels increased and the effect of J5 on FEV1 became significant.
  • First study, analysis limited to the two dustiest categories: the estimated annual decline in FEV1 was 40% greater than from age alone in J5 and 80% greater in J6. For FVC the figures were 60% and 90%. The increase in profusion of small opacities was over three times that due to age alone in both categories.
  • First study: 22% of the 137 men who worked only in the lower categories J1 to J4 had category 1 or more pneumoconiosis, compared with 43% of the 77 men exposed in J5 and J6.
  • First study: the FEV1/FVC% appeared unaffected by exposure, even at the highest level. It was also unaffected in the second study.
  • Second study (224 mill workers): 30% had category 1 or more pneumoconiosis and 2.7% category 2; none had category 3.
  • Second study, excluding J4: exposure in J5 almost doubled the estimated annual decline in FEV1 and more than doubled that in FVC. In J6 the FEV1 decline was more than doubled and the FVC decline trebled. The increase in small opacities was doubled in J6, and in J5 it was not significantly different from age alone.
  • Second study: in the rock crushing plant (J4), which had the lowest proportion of fibrous dust, the effect of exposure was not significantly different from that of age for any index.
• The authors' conclusion: The authors concluded that exposure in any part of the mill except the rock crushing plant caused considerable deterioration in lung function and an increase in small opacities. They also concluded that past mill dust concentrations appeared unacceptably high, probably at least 50 fibres/ml.
• Limitations the authors state:
  • Dust exposure categories were based on crude estimates, and absolute dust concentrations could not be calculated.
  • No part of the workforce could be described as unexposed, because dust from the mill and waste tips blew over the whole area.
  • In the first study, numbers in every exposure category except J2 were too small for separate analyses.
  • Only imprecise estimates of the amount smoked could be obtained.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Havelock mine, about 12 miles south-southeast of Barberton, Eswatini

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Pneumoconiosis, FEV1.

Related studies

• Decline in annual lung function in workers exposed to asbestos with and without pre-existing fibrotic changes on chest radiography — T. Nakadate (1995)
• Late progression of radiographic changes in Canari chrysotile mine and mill exworkers — J.R. Viallat, C. Boutin, et al. (1983)
• Radiographic changes in a group of chrysotile miners and millers exposed to low asbestos dust concentrations — S. Cordier, G. Theriault, et al. (1984)
• Development of radiographic abnormality in chrysotile miners and millers — G.M. Eyssen (1980)
• Lung function in relation to radiographic changes in asbestos workers — S. Zedda, G. Aresini, et al. (1973)
• Radiographic changes and lung function in relation to activity of the glutathione transferases theta and mu among asbestos cement workers — K. Jakobsson, A. Rannug, et al. (1995)

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