Carving of non-asbestiform tremolite and the risk of lung cancer: a follow-up mortality study in a historical nephrite processing cohort

Our plain-English summary of Carving of non-asbestiform tremolite and the risk of lung cancer: a follow-up mortality study in a historical nephrite processing cohort, by H.Y. Yang, R.H. Shie, P.C. Chen (Occupational and Environmental Medicine, 2013).

The study

• Authors: H.Y. Yang, R.H. Shie, P.C. Chen
• Journal: Occupational and Environmental Medicine
• Published: 2013;70(12):852-7
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: The health risks associated with exposure to non-asbestiform asbestos minerals, including nephrite, are unclear. In 1965 nephrite processing began in the town of Fengtian in Taiwan, and the majority of inhabitants were involved in the industry from 1970 until 1980. The objectives of this study were to examine lung cancer deaths and assess the carcinogenic effects of nephrite carving.

Methods: We studied mortality due to lung cancer (ICD-9 code 162 for cancers of the trachea, bronchus and lung) from 1979 to 2011. We calculated the standardised mortality ratio (SMR) for lung cancer using the age- and sex-specific cancer mortality rates in eastern Taiwan as the standard rates. Air samples, bulk samples and a surface sample were analysed.

Results: Nephrite is a non-asbestiform asbestos mineral composed of microcrystalline tremolite. During nephrite processing, in personal air samples the average concentration of elongated mineral particles with the morphological characteristics of asbestos fibres was 1.4 f/cm(3), with rough grinding generating the highest concentrations (4.7 f/cm(3)). Transmission electron microscopy (TEM) confirmed that the air samples contained intact asbestiform tremolite fibres. The ambient air samples and the wipe sample indicated paraoccupational contamination. The crude mortality rates for lung cancer were higher in Fengtian than in Taiwan for all age groups and both genders. The SMR for lung cancer was 1.28 (95% CI 1.12 to 1.45).

Conclusions: Nephrite carving may increase the risk of lung cancer. Appropriate medical monitoring is warranted for workers who are exposed to similar materials.

In plain English

This study examined lung cancer deaths in Fengtian, Taiwan, where nephrite, a jade the authors describe as a non-asbestiform tremolite mineral, was carved in family workshops. The authors treated the town's inhabitants (21 022 at the start of follow-up) as a group sharing this exposure. They used national death records from 1979 to 2011; the authors described this as, in theory, an ecological study. Against eastern Taiwan rates, the lung cancer standardised mortality ratio was 1.28 (95% CI 1.12 to 1.45). Air was sampled at one traditional workshop in 2010. A worker's 8-hour light-microscopy average was 1.4 fibres per cubic centimetre; rough grinding reached 4.7 fibres per cubic centimetre. A sample near the door measured 0.11 fibres per cubic centimetre. Electron microscopy showed both asbestiform tremolite fibres and cleavage fragments. No pleural cancer deaths were recorded, against 0.96 mesothelioma deaths expected. The authors concluded that nephrite carving may increase lung cancer risk. They cautioned that the association may not be causal and that their counting methods could not determine the proportion of asbestiform fibres versus cleavage fragments.

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: Mortality follow-up of a town population used as a historical cohort (the authors call it, in theory, an ecological study), with standardised mortality ratios plus air, bulk and surface sampling at one workshop
• Who was studied: Inhabitants of Fengtian, Hualien County, Taiwan: 21 022 at the start of follow-up and 17 321 at the end. Lung cancer deaths were followed from 1979 to the end of 2011. Expected deaths were based on age- and sex-specific rates for eastern Taiwan.
• Exposure: Carving of nephrite, described as a non-asbestiform tremolite mineral, by cutting, rough grinding, fine grinding and polishing. Exposure was reconstructed by sampling at one traditional workshop in Hualien in 2010.
• Main results:
  • Standardised mortality ratio for lung cancer in Fengtian: 1.28 (95% CI 1.12 to 1.45)
  • Crude lung cancer mortality rates were higher in Fengtian than in Taiwan for all age groups and both sexes
  • Worker personal air sample, 8-hour time-weighted average by light microscopy (NIOSH 7400): 1.4 fibres per cubic centimetre, above the OSHA permissible exposure limit of 0.1
  • Rough grinding gave the highest concentration (4.7 fibres per cubic centimetre). The area air sample, taken by a fixed pump near the workshop door, measured 0.11 fibres per cubic centimetre.
  • Wipe sample from a lampshade on a worktable: fibre density of 48.4 fibres per square millimetre
  • Transmission electron microscopy of air samples showed both intact asbestiform tremolite fibres and cleavage fragments
  • No deaths from cancer of the pleura were found in the mortality registry. The expected number of mesothelioma deaths in Fengtian was 0.96.
  • In a 2008 national survey, current smoking prevalence was 21.8% in Hualien County and 21.9% in Taiwan. The authors judged the increased risk likely independent of smoking.
• The authors' conclusion: The authors concluded that workers carving nephrite inhale asbestos fibres, which may increase their risk of lung cancer
• Limitations the authors state:
  • The association may not reflect a causal relationship, and there may be ecological bias
  • No past exposure measurements were available. Sampling was done at a single present-day traditional workshop.
  • Neither NIOSH method 7400 nor 7402 can distinguish the proportion of asbestiform fibres from that of non-asbestiform cleavage fragments
  • The population may be too small to detect mesothelioma
  • Mesothelioma may be misclassified under the ICD-9 system used in Taiwan's registry, and may have been misdiagnosed as lung cancer
  • The samples mainly involved wet procedures. Concentrations might be higher with dry techniques.

Topics

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

Medical terms in this study, explained in our Lexicon: Non-Asbestiform, Tremolite, Lung Cancer, Asbestos, Carcinogenic, Bronchus, Transmission Electron Microscopy (TEM), Asbestiform Tremolite.

Related studies

• Pulmonary fibrosis in workers exposed to non-asbestiform tremolite asbestos minerals — H.Y. Yang, R.H. Shie, et al. (2013)
• Cancer mortality in a population exposed to nephrite processing — H.Y. Yang, S.H. Huang, et al. (2016)
• Cohort study of mortality of vermiculite miners exposed to tremolite — J.C. McDonald, A.D. McDonald, et al. (1986)
• French cohort of the uranium processing workers: mortality pattern after 30-year follow-up — I. Guseva Canu, E. Cardis, et al. (2010)
• Asbestos-related disease associated with exposure to asbestiform tremolite — S.H. Srebro, V.L. Roggli (1994)
• Analysis of autoantibody profiles in two asbestiform fiber exposure cohorts — J.C. Pfau, C. Barbour, et al. (2018)

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