Trends in mesothelioma mortality rates in South Africa: 1995-2007

Our plain-English summary of Trends in mesothelioma mortality rates in South Africa: 1995-2007, by D. Kielkowski, G. Nelson, B. Bello, et al (Occupational and Environmental Medicine, 2011).

The study

• Authors: D. Kielkowski, G. Nelson, B. Bello, S. Kgalamono, J.I. Phillips
• Journal: Occupational and Environmental Medicine
• Published: 2011;68(7):547-9
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: In 1984, South Africa had one of the highest mesothelioma rates in the world. The objective of this analysis was to calculate mesothelioma mortality rates in the South African population from 1995 to 2007.

Methods: Annual mortality data and midyear population estimates were used to compute mortality rates by age group and gender for each year. The WHO World Standard Population was used as the reference population to calculate age-adjusted rates. Poisson regression models were used to test for trends.

Results: In total, 2509 deaths due to mesothelioma were identified in the study period: 1920 in men and 588 in women. There were no significant trends in mesothelioma mortality rates: age-adjusted mortality rates fluctuated from 11 to 16 and from 3 to 5 per million per year for men and women, respectively.

Conclusion: These mortality rates are much lower than expected, given the historical production and use of, and high exposure to, asbestos in South Africa. Possible reasons for this are discussed, including the effect of HIV which has been instrumental in reducing the life expectancy of South Africans in the last two decades. Asbestos-exposed individuals may not live long enough to develop mesothelioma. Competing causes of death need to be taken into account when constructing models to predict mesothelioma mortality rates.

In plain English

This short report used death certificate data from Statistics South Africa to calculate mesothelioma death rates among South Africans aged 20 and older from 1995 to 2007. The authors counted 2509 deaths from mesothelioma in that period, reported as 1920 in men and 588 in women. After adjusting for age, yearly rates ranged from 11 to 16 per million for men and from 3 to 5 per million for women. A statistical test found no significant trend for either sex. The authors noted that these rates were much lower than the incidence rates an earlier study reported for 1984. They were also lower than rates reported for Australia, the UK and the Netherlands for 1996 to 2005, despite South Africa's history of mining crocidolite, amosite and chrysotile. The authors suggested possible reasons: incomplete death registration, misdiagnosis as tuberculosis, and deaths of former migrant mine workers outside South Africa. They considered shortened life expectancy from the HIV epidemic the most plausible explanation. The authors concluded that competing causes of death should be considered when predicting mesothelioma rates. The death records did not separate pleural from peritoneal mesothelioma.

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: Short report analysing national death certificate data to calculate age-adjusted mesothelioma mortality rates and test for trends over time
• Who was studied: Mesothelioma deaths recorded on death certificates in South Africa, 1995 to 2007, with the South African general population aged 20 and older as the denominator
• Exposure: No individual exposure data were analysed. The background was South Africa's mining and use of asbestos, including crocidolite, amosite and chrysotile. The authors state that sources of exposure were not available for analysis.
• Main results:
  • 2509 mesothelioma deaths were recorded over the study period, reported as 1920 in men and 588 in women
  • The ratio of men to women among the deaths was 3:1
  • Yearly age-adjusted mortality rates ranged from 11 to 16 per million for men and from 3 to 5 per million for women
  • There was no statistically significant trend in age-adjusted mortality rates for either men or women
  • Over the whole period, the age-adjusted rate was 13 per million per year (95% CI 10 to 15) for men and 4 per million per year (95% CI 2 to 5) for women
  • Crude mortality rates rose with age: for men from 2.7 per million at ages 20 to 29 to 1395.6 per million at 80 or older; for women from 1.9 to 322.3 per million in the same age groups
• The authors' conclusion: The authors concluded that mesothelioma mortality in South Africa was much lower than expected given past asbestos exposure. They wrote that asbestos-exposed people may not live long enough to develop mesothelioma because of reduced life expectancy, mainly from HIV. They said this and other competing causes of death should be taken into account in models predicting mesothelioma mortality.
• Limitations the authors state:
  • Death coding did not distinguish pleural from peritoneal mesothelioma; the authors assumed all cases were pleural
  • Data could not be analysed by race because Stats SA had not released this information since the early 1990s
  • Population estimates by age group were available only for some years; the 2001 population structure was used to estimate the other years
  • Data on sources of exposure were not available, so occupationally and non-occupationally exposed groups could not be compared
  • Problems with the quality and completeness of death registration persist
  • Mesothelioma symptoms may be attributed to tuberculosis in South Africa
  • Deaths of former migrant mine workers that occurred outside South Africa would not be recorded

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Life Expectancy.

Related studies

• The mortality of amphibole miners in South Africa, 1946-80 — G.K. Sluis-Cremer, F.D. Liddell, et al. (1992)
• Excess mortality from stomach cancer, lung cancer, and asbestosis and/or mesothelioma in crocidolite mining districts in South Africa — J.L. Botha, L.M. Irwig, et al. (1986)
• Re: "Excess mortality from stomach cancer, lung cancer, and asbestosis and/or mesothelioma in crocidolite mining districts in South Africa" — H.P. Hart (1987)
• Compensation for environmental asbestos-related diseases in South Africa: a neglected issue — N. Ndlovu, J.T. Naude, et al. (2013)
• Health effects of amosite mining and milling in South Africa — J. Murray, G. Nelson (2008)
• Asbestosis in South Africa--certain geographical and environmental considerations — G.K. Sluis-Cremer (1965)

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