Cancer mortality in a population exposed to nephrite processing

Our plain-English summary of Cancer mortality in a population exposed to nephrite processing, by H.Y. Yang, S.H. Huang, R.H. Shie, et al (Occupational and Environmental Medicine, 2016).

The study

• Authors: H.Y. Yang, S.H. Huang, R.H. Shie, P.C. Chen
• Journal: Occupational and Environmental Medicine
• Published: 2016;73(8):528-36
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Although asbestos has been recognised as a strong carcinogen, many asbestos minerals exist in concrete masses, and the health risks of these materials remain inconclusive. Nephrite jade is a concrete mass of amphibole that consists of asbestiform and non-asbestiform particles. The objective of the study was to explore the carcinogenetic effect of nephrite.

Methods: We examined cancer mortality between 1979 and 2011 in Fengtian, where nephrite was mass produced from 1970 to 1980, and calculated standardised mortality ratios (SMRs).

Results: We observed significantly elevated mortality risks for cancer of the hypopharynx (SMR 2.31; 95% CI 1.37 to 3.65), larynx (SMR 2.51; 95% CI 1.55 to 3.83), oesophagus (SMR 2.04; 95% CI 1.62 to 2.54) and stomach (SMR 1.38; 95% CI 1.17 to 1.63). This study analysed the lengths, widths, structures, chemical compositions, aerodynamic diameters and distributions of elongated mineral particles (EMPs) in airways. The majority of the EMPs (68%) were short (<5 μm) and thin (<0.5 µm), and possessed asbestiform structures. The median aerodynamic diameter of the EMPs was 1.2 μm. The total deposition proportion in airways was 51.3%. The major deposition sites were the head airway (37.5%), followed by the alveolar region (10.6%) and the tracheobronchial region (3.2%).

Conclusions: The results have shown an association between EMPs and increased risk of respiratory and digestive cancers. Further research is needed that includes information on smoking habits and exposure to asbestos.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

In plain English

This population-based cohort study examined cancer deaths from 1979 to 2011 in Fengtian, Taiwan. Nephrite jade was mass produced there from 1970 to 1980, often in homes. Deaths were compared with expected numbers from national rates (standardised mortality ratios, SMRs). Among all residents, deaths exceeded expectations for cancer of the hypopharynx (SMR 2.31; 95% CI 1.37 to 3.65), larynx (2.51; 1.55 to 3.83), oesophagus (2.04; 1.62 to 2.54) and stomach (1.38; 1.17 to 1.63). All cancers combined (SMR 1.01; 95% CI 0.96 to 1.07) and trachea, bronchus and lung cancer (SMR 0.99; 95% CI 0.87 to 1.13) were not statistically significantly elevated. Women had raised trachea, bronchus and lung cancer deaths 21 to 30 years after mass production (SMR 1.52; 95% CI 1.10 to 2.03). No pleural cancer deaths were found. Air samples showed mostly short, thin tremolite particles, both asbestiform and non-asbestiform. The authors concluded there was an association between these particles and respiratory and digestive cancers, calling for research on smoking and asbestos exposure. They noted asbestos was also mined in Fengtian, and the registry lacks a mesothelioma category.

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: Population-based historical cohort study of cancer mortality using standardised mortality ratios (indirect standardisation against national Taiwanese rates). It was combined with electron microscope analysis of archived air samples and modelling of particle deposition in the airways.
• Who was studied: All inhabitants of Fengtian township, Hualien County, Taiwan. Cancer deaths from 1979 to 2011 came from the Taiwan Cancer Registry. The mid-year population fell from 21 022 to 17 321 over the period. The general population of Taiwan was the reference.
• Exposure: Nephrite jade processing (cutting, grinding, polishing) during mass production from 1970 to 1980. Work was usually done in homes, and family members were exposed to tremolite through paraoccupational contamination. Airborne elongated mineral particles were 99% tremolite and 1% actinolite.
• Main results:
  • Among all Fengtian residents, mortality was elevated for four cancers. Hypopharynx: SMR 2.31 (95% CI 1.37 to 3.65). Larynx: SMR 2.51 (95% CI 1.55 to 3.83). Oesophagus: SMR 2.04 (95% CI 1.62 to 2.54). Stomach: SMR 1.38 (95% CI 1.17 to 1.63).
  • For all cancer types combined, all residents had 1216 observed deaths, SMR 1.01 (95% CI 0.96 to 1.07). This was not statistically significant.
  • For cancer of the trachea, bronchi and lungs over the whole period, all residents had 239 observed deaths, SMR 0.99 (95% CI 0.87 to 1.13). This was not statistically significant.
  • Females had significantly higher mortality 21 to 30 years after the mass nephrite production period for three groupings. Respiratory tract cancer: SMR 1.55 (95% CI 1.15 to 2.05). Hypopharynx cancer: SMR 20.38 (95% CI 4.10 to 59.54). Cancer of the trachea, bronchi and lungs: SMR 1.52 (95% CI 1.10 to 2.03).
  • Elevated mortality for oesophageal and stomach cancers was seen in the period 0 to 10 years after the mass nephrite production period.
  • Leukaemia mortality among all residents was elevated: 40 deaths, SMR 1.48. Table 1 gives the 95% CI as 1.05 to 2.01.
  • No deaths from cancer of the pleura were identified.
  • Of the airborne particles, 99% were tremolite and 1% actinolite. Most (68%) were short (under 5 micrometres long) and thin (under 0.5 micrometres wide). Median length was 2.4 micrometres and median width 0.3 micrometres.
  • Asbestiform and non-asbestiform particles were both present in the air samples. A regression analysis suggested a high proportion were non-asbestiform.
  • Estimated total deposition of inhaled particles in the airway was about 51.3%. Most was in the head airway (37.5%), followed by the alveolar region (10.6%) and the tracheobronchial region (3.2%).
• The authors' conclusion: The authors concluded that the results showed an association between the elongated mineral particles and increased risk of respiratory and digestive cancers. They called for further research including smoking habits and asbestos exposure. In the discussion they 'tentatively' proposed that the increased risks were primarily related to nephrite processing.
• Limitations the authors state:
  • No information on smoking habits or asbestos exposure was included. The authors called for further research that includes it.
  • Asbestos mining took place in Fengtian between 1938 and 1985. The study population may have included miners, which could raise the SMRs.
  • Taiwan's registry uses ICD-9, which has no category for mesothelioma. Mesothelioma may therefore have been misclassified as lung cancer.
  • The sample size may have been too small to detect deaths from pleural cancer.
  • All residents were treated as equally exposed, although exposures differed. This could cause misclassification of exposure.
  • Residents who moved away and died elsewhere were not counted. This may have led to underestimated mortality risk.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Stomach cancer, Throat and laryngeal cancer.

Medical terms in this study, explained in our Lexicon: Asbestos, Amphibole Group, Asbestiform, Non-Asbestiform, Deposition, Habit.

Related studies

• Carving of non-asbestiform tremolite and the risk of lung cancer: a follow-up mortality study in a historical nephrite processing cohort — H.Y. Yang, R.H. Shie, et al. (2013)
• Exposure to nitrosamines, carbon black, asbestos, and talc and mortality from stomach, lung, and laryngeal cancer in a cohort of rubber workers — K. Straif, U. Keil, et al. (2000)
• Occupation and larynx and hypopharynx cancer: a job-exposure matrix approach in an international case-control study in France, Italy, Spain and Switzerland — F. Berrino, L. Richiardi, et al. (2003)
• Laryngeal and hypopharyngeal cancer and occupational exposure to asbestos and man-made vitreous fibers: results of a case-control study — J.L. Marchand, D. Luce, et al. (2000)
• Occupational exposures and risk of esophageal and gastric cardia cancers among male Swedish construction workers — C. Jansson, A.L. Johansson, et al. (2005)
• Occupational exposure and laryngeal and hypopharyngeal cancer risk in central and eastern Europe — O. Shangina, P. Brennan, et al. (2006)

Browse more research in Occupational and Environmental Medicine, or return to medical research.