Occupational Exposure to Talc Increases the Risk of Lung Cancer: A Meta-Analysis of Occupational Cohort Studies

Our plain-English summary of Occupational Exposure to Talc Increases the Risk of Lung Cancer: A Meta-Analysis of Occupational Cohort Studies, by C.J. Chang, Y.K. Tu, P.C. Chen, et al (Canadian Respiratory Journal, 2017).

The study

• Authors: C.J. Chang, Y.K. Tu, P.C. Chen, H.Y. Yang
• Journal: Canadian Respiratory Journal
• Published: 2017;2017:1270608
• Type of article: Meta-analysis, Review
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: Talc is widely used in industrial applications. Previous meta-analyses of carcinogenic effects associated with inhaled talc included publications before 2004, with a lack of data in China, the largest talc-producing country. The safety of workers exposed to talc was unclear due to limited evidence. The objective of this study was to reevaluate the association between inhaled talc and lung cancer.

Setting Participants And Outcome Measures: A meta-analysis was performed to calculate the meta-SMR of lung cancer. We searched the MEDLINE, EMBASE, CNKI, and Wanfang Data databases through March 2017. Data from observational studies were pooled using meta-analysis with random effects models.

Results: Fourteen observational cohort studies (13 publications) were located via literature search. The heterogeneity of the included data was high (I-squared = 72.9%). Pooling all the cohorts yielded a meta-SMR of 1.45 (95% CI: 1.22-1.72, p < 0.0001) for lung cancer among the study subjects exposed to talc. Subgroup analysis for asbestos contamination showed no significant difference in lung cancer death between subjects exposed to talc with and without asbestos (p = 0.8680), indicating that this confounding factor may have no significance.

Conclusions: This study provides evidence that nonasbestiform talc might still increase the risk of lung cancer. Further epidemiological studies are required to evaluate the safety of workers with occupational talc exposure.

In plain English

This meta-analysis pooled published worker studies to examine whether breathing talc at work is linked to lung cancer. The authors searched English and Chinese databases through March 2017 and combined 14 cohorts from 13 publications: 95,711 workers in talc mines and mills and in industries that use talc. These cohorts had 1,766 lung cancer deaths where 1,302 were expected. The pooled standardized mortality ratio was 1.45 (95% CI 1.22 to 1.72), with large differences between studies. The authors sorted cohorts by whether the talc was described as containing asbestiform fibers. The pooled ratio was 1.50 (95% CI 1.02 to 2.22) for talc without asbestiform fibers and 1.45 (95% CI 1.18 to 1.78) for contaminated talc, with no significant difference between them. Pooled ratios were lower for European cohorts than for North American or Asian ones. The authors concluded that talc exposure is associated with increased lung cancer risk regardless of asbestiform fibers. They noted incomplete smoking data, mostly male workers, and too little exposure measurement to show a dose-response relationship.

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: Meta-analysis (labeled a review article) pooling occupational cohort studies with random effects models. Case-control studies were excluded.
• Who was studied: 14 occupational cohorts from 13 publications, with a total of 95,711 workers. The cohorts came from Russia, Italy, China, the USA, Germany, Norway, Austria, France and one multinational pulp and paper study covering 11 countries. Seven cohorts were from talc-producing companies or mines and seven from talc-using industries (printing, rubber, pulp and paper, cement or plastering, pottery). The included publications date from 1979 to 2006.
• Exposure: Occupational inhaled talc. Using the original articles' descriptions, the authors grouped the cohorts into talc without asbestiform fibers (7 cohorts) and talc contaminated with asbestiform fibers or asbestos (7 cohorts). All cohorts also had other documented workplace exposures, such as quartz or silica, radon, nitrosamines and carbon black.
• Main results:
  • Across all 14 cohorts (95,711 workers), there were 1,766 observed lung cancer deaths against 1,302 expected.
  • The pooled (meta) SMR for lung cancer among talc-exposed workers was 1.45 (95% CI 1.22 to 1.72).
  • Heterogeneity between the included studies was high (I-squared 72.9%). Individual cohort SMRs ranged from 0.92 in a Norwegian cohort to 4.50 in a Chinese cohort.
  • For cohorts exposed to talc without asbestiform fibers, the meta-SMR was 1.50 (95% CI 1.02 to 2.22). Table 3 lists this as 1.51.
  • For cohorts exposed to talc contaminated with asbestiform fibers, the meta-SMR was 1.45 (95% CI 1.18 to 1.78).
  • There was no statistically significant difference in lung cancer meta-SMR between the talc-with and talc-without asbestiform fiber subgroups (p = 0.8680).
  • The talc-producing industry had a meta-SMR of 1.47 (95% CI 1.02 to 2.10) and talc-user industries had 1.42 (95% CI 1.14 to 1.76). The difference was not significant.
  • By region (excluding the multinational study), the meta-SMR was 1.98 (95% CI 1.11 to 3.50) in Asia, 1.16 (95% CI 1.02 to 1.31) in Europe and 2.01 (95% CI 1.34 to 3.00) in North America. The difference between regions was statistically significant (p = 0.0103).
  • The three Chinese-language studies, all from China, showed higher lung cancer SMRs than English-language studies: 2.45 (95% CI 1.44 to 4.16) versus 1.34 (95% CI 1.13 to 1.60). Study quality also made a significant difference.
  • The funnel plot and Egger's test showed no evidence of publication bias (p = 0.65).
• The authors' conclusion: The authors concluded that their findings suggest talc exposure is associated with increased lung cancer risk whether or not asbestiform fibers are present. They also concluded that the safety of workers with occupational talc exposure should be carefully reevaluated.
• Limitations the authors state:
  • Smoking data were not available for all cohorts, which prevented further stratification by smoking.
  • Effects by gender could not be analyzed because most talc-exposed workers were male.
  • The lack of quantitative talc exposure data meant no dose-response relationship could be shown.
  • Workers in the included studies were also exposed to other hazardous materials, which may confound the results.
  • The regional comparison might be biased by industry types and coexposures.

Topics

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

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Talc, Lung Cancer, Meta-Analysis, Carcinogenic, Confounding, Non-Asbestiform.

Related studies

• Talc exposure and risk of stomach cancer: Systematic review and meta-analysis of occupational cohort studies — C.J. Chang, Y.K. Tu, et al. (2020)
• Occupational exposures to cosmetic talc and risk of mesothelioma: an updated pooled cohort and statistical power analysis with consideration of latency period — G.M. Marsh, A.M. Ierardi, et al. (2019)
• Stomach Cancer and Exposure to Talc Powder without Asbestos via Chinese Herbal Medicine: A Population-Based Cohort Study — C.J. Chang, Y.H. Yang, et al. (2019)
• Absence of mesothelioma risk maintained in an expanded international cohort of cosmetic talc miners and millers — A.M. Ierardi, G.M. Marsh (2020)
• Letter concerning: Occupational exposures to cosmetic talc and risk of mesothelioma: an updated pooled cohort and statistical power analysis with consideration of latency period by Gary M. Marsh et al. (Inhal Toxicol. 2019 Aug 5:1-11. doi:10.1080/08958378.2019.1645768) — M.M. Finkelstein (2019)
• Confidence interval function analysis to evaluate the risk of mesothelioma among an expanded international cohort of cosmetic talc miners and millers — G.M. Marsh, A.M. Ierardi (2020)

Browse more research in Canadian Respiratory Journal, or return to medical research.