Mesothelioma risk and environmental exposure to asbestos: past and future trends in Japan

Our plain-English summary of Mesothelioma risk and environmental exposure to asbestos: past and future trends in Japan, by K. Azuma, I. Uchiyama, Y. Chiba, et al (International Journal of Occupational and Environmental Health, 2009).

The study

• Authors: K. Azuma, I. Uchiyama, Y. Chiba, J. Okumura
• Journal: International Journal of Occupational and Environmental Health
• Published: 2009;15(2):166-72
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Although asbestos has been widely distributed in the environment, health risks due to general environmental exposure to asbestos have not been estimated. Future mesothelioma risk from environmental exposure to asbestos in Japan was estimated by comparing historical exposure data and mortality attributed to environmental exposure. We developed an equation to estimate environmentally-attributable mesothelioma based on the US Environmental Protection Agency's model for occupational mesothelioma mortality. Based on our calculations, mesothelioma risks per year of exposure will reach peak levels in 2033 and range from 4.8 x 10(-6) to 1.1 x 10(-5). The number of deaths is estimated to range from 542-1276 in 2033. The cumulative number of deaths will reach around 17,000-37,000 in the years 1970-2070. Our estimation of risk approximately corresponded to observed risks. Past and predicted future disease suggest the need for social and medical support in these areas.

In plain English

This was a modelling study from Japan. It estimated past and future mesothelioma deaths caused by general environmental exposure to airborne asbestos, as distinct from work, household or indoor exposure. The authors reconstructed airborne asbestos levels from field measurements and sprayed-asbestos use in Tokyo. They estimated that levels rose from 1950 and peaked around 1970 at 3 to 8 fibers per litre. They adapted a 1986 US Environmental Protection Agency model built from occupational studies. They checked it against government surveys of mesothelioma deaths in Osaka, Hyogo and Saga prefectures, where 22 of 130, 25 of 143 and 3 of 20 cases were assumed to be environmental. The model's maximum estimates corresponded to the observed yearly risks, though they were slightly lower. The model projected that yearly risk would peak in 2033, at 4.8 to 11 in a million. It projected 542 to 1276 deaths that year and 17,000 to 37,000 cumulative deaths from 1970 to 2070. The authors noted that the exposure data were limited and that misclassified cases could overstate risk. They concluded that the results might suggest a need for social and medical support.

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: Risk-modelling study. A mesothelioma risk equation adapted from the 1986 US EPA occupational model was applied to estimated historical airborne asbestos concentrations, and its results were compared with observed mesothelioma deaths from government field surveys.
• Who was studied: Projections were made for the total Japanese population. Observed comparison data came from Ministry of the Environment surveys of mesothelioma deaths: 130 participants in Osaka Prefecture (2003–2005), 143 in Hyogo Prefecture (2002–2004) and 20 in Saga Prefecture (2003–2005).
• Exposure: General environmental airborne asbestos; no fiber type was specified. Concentrations were estimated from Tokyo measurements and sprayed-asbestos use, with an estimated peak of 3 to 8 fibers/L around 1970. National surveys gave geometric means of about 1.16 and 1.15 fibers/L in 1985 and 0.23 fibers/L in 2005. Cases with no reported occupational, domestic or indoor exposure were assumed to be environmental.
• Main results:
  • Among surveyed mesothelioma deaths, the share assumed to be from environmental exposure was 16.9% in Osaka (22 of 130), 17.5% in Hyogo (25 of 143) and 15.0% in Saga (3 of 20).
  • Observed yearly mesothelioma death risks from environmental exposure were 1.68 x 10^-6 in Osaka, 2.31 x 10^-6 in Hyogo and 1.56 x 10^-6 in Saga. The model's maximum estimates were 1.46 x 10^-6, 1.27 x 10^-6 and 1.40 x 10^-6 respectively. These maximum estimates corresponded to the observed risks but were slightly lower.
  • For Japan as a whole, the estimated annual risk of mesothelioma death from environmental exposure was projected to peak in 2033, at between 4.8 x 10^-6 and 1.1 x 10^-5.
  • Estimated deaths in Japan from environmental exposure were 542 to 1276 in 2033, and 17,000 to 37,000 cumulatively over 1970 to 2070.
• The authors' conclusion: The authors concluded that limited available estimates reveal past and future trends in mesothelioma risk from general environmental asbestos exposure in Japan. They added that the results might suggest a need for social and medical support for general populations.
• Limitations the authors state:
  • Past exposure trends rested on limited data, in particular two data points around 1970.
  • The surveys treated all mesotheliomas as asbestos-related, which may have overestimated the asbestos risk.
  • The high ratio of males to females among the assumed environmental cases suggests that some cases were misclassified, in which case the risk estimates would be too high.

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, Environmental Exposure.

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• Assessment of cancer risks due to environmental exposure to asbestos — H.A. Driece, S. Siesling, et al. (2010)
• Past and current asbestos exposure and future mesothelioma risks in Britain: The Inhaled Particles Study (TIPS) — C. Gilham, C. Rake, et al. (2018)
• Risk assessment due to environmental exposures to fibrous particulates associated with taconite ore — R. Wilson, E.E. McConnell, et al. (2008)
• Airborne fiber concentration and size distribution of mineral fibers in area with serpentinite outcrops in Aichi prefecture, Japan — K. Sakai, N. Hisanaga, et al. (2001)

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