Evaluation of respiratory effects in miners and millers exposed to talc free of asbestos and silica

Our plain-English summary of Evaluation of respiratory effects in miners and millers exposed to talc free of asbestos and silica, by D.H. Wegman, J.M. Peters, M.G. Boundy, et al (British Journal of Industrial Medicine, 1982).

The study

• Authors: D.H. Wegman, J.M. Peters, M.G. Boundy, T.J. Smith
• Journal: British Journal of Industrial Medicine
• Published: 1982;39(3):233-8
• Cited by: 27 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. 000713).

Abstract

Miners and millers of talc ore, free from asbestos and silica, were examined for respiratory effects. A study of 116 subjects included the modified British Medical Research Council respiratory symptom questionnaire, simple spirometry, chest radiography, and limited examination of the chest. A one-year follow-up evaluation was performed on 103 subjects. Of the 12 subjects whose chest radiographs showed small round or irregular opacities (perfusion 1/0 or greater), five had never smoked cigarettes. Pulmonary function values at the time of the initial study were less than predicted and the rates of loss of FEV1 and FVC greater than expected. These differences were in part attributed to cigarette smoking but were greater than predicted from that source alone. There was evidence of an exposure effect after adjusting for cigarette smoking and we conclude that these workers have been affected by their exposures. No clear interaction between smoking and exposure could be identified. Populations such as this will need to be studied for longer periods to determine what current dust levels are safe.

In plain English

The authors studied talc miners and millers at three Vermont companies, where the talc was described as essentially free of silica and asbestos. Of 174 workers, 142 were examined. Results covered the 116 aged 25 or older, and 103 of them were retested about a year later. Workers had breathing tests, and 100 had chest X-rays. There was no control group, so lung function was compared with predicted values. After adjusting for smoking, the higher talc-exposure group had lower values than the lower group on all four lung-function measures. The differences were statistically significant only for two airflow measures: 3.6% for FEV1/FVC and 8.9% for MMEF. Lifetime talc exposure, but not smoking, was associated with small opacities on X-rays. Five of the 12 workers with small rounded opacities had never smoked. Average yearly loss of FEV1 was 62 ml. This was not significantly different from published values, and it did not correlate with current exposure. The authors suggested the exposure limit, then above 5 mg/m3, be re-evaluated if the lung-function effects seen in cigarette smokers in this study were to be prevented. They said longer follow-up was desirable before concluding talc had no effect on non-smokers.

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: Cross-sectional study of currently employed workers, with a one-year follow-up of lung function
• Who was studied: Talc miners and millers employed by three talc companies in Vermont, USA, studied in 1975-6. Of 174 workers, 142 (82%) were examined. Data were presented for the 116 aged 25 or older. 103 of these were restudied a year later, and 100 had chest radiographs.
• Exposure: Industrial talc dust described as essentially free from silica and asbestos. Respirable dust levels were below 3.0 mg/m3. Lifetime exposure was estimated as 'talc years' from work histories and current and historical dust estimates.
• Main results:
  • Among the 116 workers, mean observed/predicted FVC (98.0%) was not significantly different from 100. Observed/predicted FEV1 (92.6%) and MMEF (66.2%) were significantly reduced.
  • After adjustment for cigarette smoking, the differences between the high and low talc-year groups were: FVC% 0.5% (p = 0.84), FEV1% 4.5% (p = 0.18), FEV1/FVC 3.6% (p = 0.03) and MMEF% 8.9% (p = 0.04).
  • The difference favoured the low-exposure group in every instance, but was significant only for FEV1/FVC and MMEF%.
  • There was a suggestion of an interaction between smoking and exposure for FEV1/FVC and MMEF%, but it was not statistically significant.
  • Among those X-rayed, talc years was associated with both small rounded and small irregular opacities, while smoking was not.
  • Five of the 12 subjects with small rounded opacities had never smoked cigarettes.
  • Ten subjects had pleural abnormalities on chest radiographs.
  • Four of the subjects with pleural abnormalities had pleural plaques and diffuse pleural thickening.
  • None of the radiographic changes correlated with the lung-function results.
  • Among the 103 workers followed for a year, average annual FEV1 loss was 62 ml. The authors described this as raised but not significantly different from expected annual decrements of 19 to 47 ml/y reported in other studies.
  • The one-year loss in lung function did not correlate with current levels of talc dust exposure.
  • Lung-function effects in non-smokers were not associated with lifetime or current talc exposure.
  • Pack-years of smoking and years exposed to talc each showed a weak correlation with cough and phlegm.
• The authors' conclusion: The authors concluded that the then-current threshold limit value, which was greater than 5 mg/m3, should be re-evaluated if the lung-function effects seen in cigarette smokers in this study are to be prevented. They said the cross-sectional results were consistent with talc causing obstructive effects in smokers, but that clear confirmation was lacking.
• Limitations the authors state:
  • No appropriate control group was available, so results were compared with predicted values from a standard population.
  • Gaps in historical exposure data were filled with anecdotal information, and its accuracy could not be assessed.
  • The follow-up interval was short, and the range of exposures may have been too narrow to detect exposure-related effects in such a small population.
  • Average employment was relatively short (8.5 years). The authors said longer follow-up is desirable before concluding that talc has no effect on non-smokers at this level of exposure.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: Talc, Spirometry, Chest X-Ray, FEV1.

Related studies

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• An update of a mortality study of talc miners and millers in Italy — M. Coggiola, D. Bosio, et al. (2003)
• Mortality of Talc Miners and Millers From Val Chisone, Northern Italy: An Updated Cohort Study — E. Pira, M. Coggiola, et al. (2017)
• Malignant mesothelioma incidence among talc miners and millers in New York State — M.M. Finkelstein (2012)
• Letter to the editor on commentary: malignant mesothelioma incidence among talc miners and millers in New York state by M M Finkelstein — R.P. Nolan, J.F. Gamble, et al. (2013)
• Absence of mesothelioma risk maintained in an expanded international cohort of cosmetic talc miners and millers — A.M. Ierardi, G.M. Marsh (2020)

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