Cause-specific mortality among workers in asbestos mining and enrichment factories (Asbest Chrysotile Cohort Study) compared with the general population of Sverdlovsk Oblast, Russian Federation

Our plain-English summary of Cause-specific mortality among workers in asbestos mining and enrichment factories (Asbest Chrysotile Cohort Study) compared with the general population of Sverdlovsk Oblast, Russian Federation, by A. Olsson, J. Schüz, I. Bukhtiyarov, et al (Journal of Occupational Medicine and Toxicology, 2025).

The study

• Authors: A. Olsson, J. Schüz, I. Bukhtiyarov, M. Moissonnier, E. Ostroumova, G. Ferro, E. Feletto, G. Byrnes, I. Tskhomariia, K. Straif, T. Morozova, H. Kromhout, E. Kovalevskiy
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2025;20(1):37
• Read it: PubMed · Publisher · Free full text

Abstract

OBJECTIVES: Complementing the previously published cohort-internal comparison we hereby compare the cause-specific mortality in workers of the Asbest Chrysotile Cohort study (ACC) with the general population of Sverdlovsk Oblast where the mine and factories are located. METHODS: The ACC cohort database and the regional Federal State Statistic Service for the Sverdlovsk Oblast population were used. We calculated sex-specific standardized mortality ratios (SMRs) and 95% confidence intervals (CI) for the main ICD-10 disease groups and for selected cancer sites for the populations ≥ 15 years from 1980 to 2015. In relation to exposure, we applied the Sverdlovsk rates to the person-years in each exposure category to obtain expected numbers of lung cancer deaths. For comparing types of ACC workers (mine, enrichment factories, both), we calculated lung cancer SMRs in men by duration of employment (< 5 years, 5–14 years, and ≥ 15 years) and start of employment (before or after 1975) with miners as reference in each stratum. RESULTS: Overall mortality of men in the ACC was reduced by 14%, mainly because of the most common cause of death, circulatory disease; this effect was much weaker in women. Elevated mortality was observed for both sexes from diseases of the digestive system (10–30%) and blood and blood forming organs (121–181%). Lung cancer mortality in men was increased from the 3rd quartile of chrysotile containing dust and in the highest quartile with SMR 1.30, 95% CI 1.07–1.57, while the increase in high exposed women was not reaching statistical significance (SMR 1.69, 95% CI 0.87–2.96). No increased SMRs were seen for laryngeal, stomach or ovarian cancers. Male factory workers first employed before 1975 had higher lung cancer mortality compared to miners, but not when employed after 1974. CONCLUSIONS: The observed excess in lung cancer confirms previous observations in the ACC. Risk management measures in the enrichment factories may have reduced the lung cancer risk to the level of the miners in recent decades.

In plain English

This cohort study compared causes of death among 30,445 mine, factory, transport, laboratory and explosives-unit employees (20,662 men, 9,783 women) of a chrysotile asbestos company in Asbest, Russian Federation, with the population of Sverdlovsk Oblast from 1980 to 2015. Overall mortality in men was 14% lower than in the region (SMR 0.86), which the authors linked to a healthy worker effect. This pattern was much weaker in women. Men's lung cancer mortality was 20% higher (SMR 1.20, 95% CI 1.10–1.30), with increases in the two highest cumulative dust categories (above 65 mg/m3-years). Above 150 mg/m3-years the SMR was 1.30 (95% CI 1.07–1.57). Women's lung cancer mortality was elevated but not statistically significant. Both sexes had raised mortality from digestive diseases and from non-cancer blood diseases (9 deaths in men, 6 in women). No increased SMRs were seen for laryngeal, stomach or ovarian cancers. Among men hired before 1975, factory workers employed 5 or more years had significantly higher lung cancer mortality than miners. After 1974, differences by type of work were not significant. The authors concluded that factory risk management may have reduced lung cancer risk to the miners' level.

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 cohort study comparing the cohort's death rates with those of the regional population, using standardized mortality ratios (SMRs). It also includes an internal comparison of lung cancer among male miners, factory workers and those who worked in both.
• Who was studied: 30,445 current and former employees (20,662 men, 9,783 women) of PJSC Uralasbest in Asbest town, Sverdlovsk Oblast, Russian Federation. They worked in the mine, all factories, the auto-transport and external rail transportation departments, the central laboratory and the explosives unit. Each had at least one cumulative year of employment between 1975 and 2010. They were followed from 1976 to 2015, with SMRs calculated for 1980 to 2015. The comparison population was the Sverdlovsk Oblast population aged 15 years and over, with cohort deaths and person-years removed.
• Exposure: Chrysotile-containing dust in the mine and enrichment factories. Each worker's cumulative dust exposure (mg/m3-years) was estimated from a company-specific job-exposure matrix built from more than 90,000 stationary airborne dust measurements.
• Main results:
  • Overall mortality in men was 14% lower than in Sverdlovsk Oblast (SMR 0.86, 95% CI 0.84–0.88), mainly because of lower deaths from circulatory disease. The reduction was much weaker in women (SMR 0.98, 95% CI 0.94–1.02).
  • In men, relative SMRs (rSMRs) were 17–19 units higher than the SMRs, which the authors took to indicate a healthy worker survival effect.
  • Lung cancer mortality in men was 20% higher than in Sverdlovsk Oblast (556 deaths; SMR 1.20, 95% CI 1.10–1.30).
  • In men, lung cancer mortality in the lowest cumulative dust category (more than 0 to 20 mg/m3-years) was almost identical to the region's (SMR 1.02, 95% CI 0.82–1.25).
  • In men, lung cancer mortality was increased in the two highest cumulative dust categories. For more than 65 to 150 mg/m3-years the SMR was 1.26 (95% CI 1.09–1.44, 209 deaths).
  • For men in the highest cumulative dust category (more than 150 mg/m3-years) the SMR was 1.30 (95% CI 1.07–1.57, 108 deaths).
  • In women, lung cancer mortality was elevated but not statistically significant (41 deaths; SMR 1.35, 95% CI 0.97–1.83). Across dust categories it varied in a U-shape, and all confidence intervals included 1. In the highest category the SMR was 1.69 (95% CI 0.87–2.96).
  • Both sexes had higher mortality from diseases of the digestive system: men SMR 1.10 (95% CI 1.00–1.21, 429 deaths), women SMR 1.30 (95% CI 1.10–1.51, 159 deaths).
  • Both sexes had higher mortality from non-cancer diseases of blood and blood-forming organs: men SMR 2.21 (95% CI 1.01–4.20, 9 deaths), women SMR 2.81 (95% CI 1.03–6.12, 6 deaths).
  • Women had higher mortality from genitourinary diseases (SMR 1.50, 95% CI 1.07–2.05).
  • Women had lower mortality from cervical cancer (SMR 0.57, 95% CI 0.29–0.99).
  • No increased SMRs were seen for laryngeal cancer (men SMR 0.98, 95% CI 0.72–1.31), stomach cancer (men SMR 0.94, 95% CI 0.81–1.09; women SMR 1.08, 95% CI 0.83–1.37) or ovarian cancer (SMR 0.96, 95% CI 0.67–1.34).
  • Among men first employed before 1975, factory workers with 5 or more years of employment had significantly higher lung cancer mortality than miners, who were the reference group (SMR 1.00). The SMR was 1.73 (95% CI 1.12–2.55) for 5–14 years of employment and 1.39 (95% CI 1.09–1.75) for 15 years or more. For factory workers employed less than 5 years the SMR was 1.66 (95% CI 0.34–4.86, 3 deaths).
  • Among men first employed after 1974, lung cancer mortality did not differ significantly by type of work. For factory workers employed 15 years or more, the SMR relative to miners was 1.43 (95% CI 0.39–3.66, 4 deaths).
• The authors' conclusion: The authors concluded that the excess lung cancer confirms previous observations in this cohort. They also concluded that risk management measures in the enrichment factories may have reduced factory workers' lung cancer risk to the level of the miners in recent decades. In their view, the increased mortality from digestive diseases and from non-cancer blood diseases remains without a credible explanation.
• Limitations the authors state:
  • Possible heterogeneity and lack of detailed regional data over the follow-up period could affect the comparison with Sverdlovsk Oblast.
  • The relatively low average age at death in both populations may have masked increased mortality from cancers and other diseases that mostly occur at older ages.
  • The excess of non-cancer blood diseases rests on small numbers and should be interpreted with caution.
  • Some specific cancer types, such as mesothelioma, could not be isolated in the older regional cause-of-death coding, so mesothelioma was not compared with the region.
  • Regional ovarian cancer death rates were missing for 1980–1998, so rates from 1999–2015 were extrapolated to that period.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Cohort Study, standardized mortality ratio (SMR), confidence interval, Lung Cancer, Statistical Significance, Ovarian Cancer.

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• Cancer mortality in chrysotile miners and millers, Russian Federation: main results (Asbest Chrysotile Cohort-Study) — J. Schüz, E. Kovalevskiy, et al. (2024)
• Occupational cohort study of current and former workers exposed to chrysotile in mine and processing facilities in Asbest, the Russian Federation: Cohort profile of the Asbest Chrysotile Cohort study — J. Schüz, I. Bukhtiyarov, et al. (2020)
• Comparison of Two Information Sources for Cause-of-Death Follow-up in the Russian Federation: The Asbest Chrysotile Cohort Study — J. Schüz, E. Kovalevskiy, et al. (2020)
• Tobacco smoking among chrysotile asbestos workers in Asbest in the Russian Federation — A. Olsson, E.V. Kovalevskiy, et al. (2020)
• A comparison of parallel dust and fibre measurements of airborne chrysotile asbestos in a large mine and processing factories in the Russian Federation — E. Feletto, S.J. Schonfeld, et al. (2017)
• Developing a company-specific job exposure matrix for the Asbest Chrysotile Cohort Study — E. Feletto, E.V. Kovalevskiy, et al. (2022)

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