Mapping the risk of mesothelioma due to neighborhood asbestos exposure

Our plain-English summary of Mapping the risk of mesothelioma due to neighborhood asbestos exposure, by N. Kurumatani, S. Kumagai (American Journal of Respiratory and Critical Care Medicine, 2008).

The study

• Authors: N. Kurumatani, S. Kumagai
• Journal: American Journal of Respiratory and Critical Care Medicine
• Published: 2008;178(6):624-9
• Cited by: 82 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Rationale: Little is known about neighborhood exposure to asbestos and mesothelioma risk among residents around an industrial source of asbestos.

Objectives: To investigate the magnitude of the risk among residents by asbestos exposure levels and to determine the range of the area affected by asbestos.

Methods: We calculated standardized mortality ratios of mesothelioma from 1995 to 2006 among the estimated population at risk that lived around a former large asbestos cement pipe plant in Amagasaki City, Japan, between 1957 and 1975, the time when the plant had used crocidolite and chrysotile. The distance between the plant and homes and relative asbestos concentrations obtained by diffusion equations involving meteorological conditions were used to determine asbestos exposure levels among residents.

Measurements And Main Results: We identified 73 mesothelioma deaths of 35 men and 38 women who had no occupational exposure to asbestos. Among persons who had lived within a 300-m radius of the plant, the standardized mortality ratio of mesothelioma was 13.9 (95% confidence interval, 5.6-28.7) for men and 41.1 (95% confidence interval, 15.2-90.1) for women. When the study area was divided into five regions by relative asbestos concentration, standardized mortality ratios of mesothelioma declined, for both sexes, in a linear dose-dependent manner with concentration. The regions with a significantly elevated standardized mortality ratio reached 2,200 m from the plant in the same direction in which the wind predominantly blew.

Conclusions: Neighborhood exposure to asbestos can pose a serious risk to residents across a wide area.

In plain English

This study examined mesothelioma among people who had lived or worked near a former asbestos cement pipe plant in Amagasaki City, Japan, which used crocidolite and chrysotile from 1957 to 1975. Subjects were 162 people with mesothelioma who had contacted the company's compensation agent; relatives answered for the deceased. People judged to have had work exposure to asbestos were excluded. The authors compared mesothelioma deaths from 1995 to 2006 with deaths expected from national rates (standardized mortality ratios, SMRs), by distance and by modeled asbestos levels that accounted for wind. Within 1,500 m, 73 deaths gave an SMR of 4.3 (95% confidence interval 3.4 to 5.4). Within 300 m, the SMR was 41.4 (confidence interval 15.2 to 90.1; 6 deaths) for women and 13.9 (5.6 to 28.7; 7 deaths) for men. Risk rose in a straight line with modeled asbestos level for both sexes. Significantly raised risk reached about 2,200 m downwind but 900 m in the opposite direction. All deaths but one were pleural mesothelioma. The authors concluded the outbreak was causally associated with the plant's asbestos, particularly crocidolite. They noted selection bias from relying on compensation applicants.

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 study comparing observed mesothelioma deaths with deaths expected from national rates (standardized mortality ratios), analyzed by residential distance and by relative asbestos concentrations modeled with diffusion equations that included weather conditions
• Who was studied: 162 of 164 residents with mesothelioma who had contacted Kubota Corporation's compensation agent by the end of April 2007 and consented to interview. Relatives were interviewed for 138 deceased subjects, and 24 subjects under treatment were interviewed themselves. 121 were judged not occupationally exposed. After further exclusions, the analysis covered 79 deaths in 1995 to 2006 plus 17 patients under treatment. Within a 1,500 m radius there were 73 deaths, among an estimated 220,809 people at risk as of 1975.
• Exposure: Neighborhood (non-occupational) exposure to airborne asbestos from an asbestos cement pipe plant that used crocidolite and chrysotile between 1957 and 1975, on average 4,670 tons of crocidolite and 4,600 tons of chrysotile per year. Exposure was defined by having lived (for at least 1 year) or worked near the plant, measured by distance and by modeled relative asbestos concentration.
• Main results:
  • Among people who had lived within 1,500 m of the plant, the 73 mesothelioma deaths gave a significantly increased SMR of 4.3 (95% confidence interval 3.4 to 5.4).
  • Women who had lived within 300 m of the plant had the highest SMR, 41.4 (95% confidence interval 15.2 to 90.1), based on 6 deaths (Table 1).
  • For women, the SMR stayed significantly elevated in every distance band out to 1,200 to less than 1,500 m.
  • Men who had lived within 300 m of the plant had an SMR of 13.9 (95% confidence interval 5.6 to 28.7), based on 7 deaths (Table 1).
  • For men, the only other significantly elevated SMR was in the 300 to less than 600 m band, at 5.6 (95% confidence interval 2.9 to 9.8). Men's SMRs were one-half or less than women's.
  • All 79 deceased subjects had pleural mesothelioma except one, who had peritoneal mesothelioma.
  • Among the 73 deceased and 17 surviving subjects combined, residence near the plant while it used crocidolite averaged 145 months (12.1 years).
  • The time from first living near the plant to first symptoms ranged from 265 to 595 months, with an average of 520 months (about 43.3 years).
  • Analyzed by modeled relative asbestos concentration, the highest SMR was 47.7 (95% confidence interval 20.8 to 105.7), for women in the highest-concentration area.
  • Significantly increased SMRs were found in areas with relative concentrations above 5 units. These areas reached about 2,200 m south-southwest of the plant (the direction the wind mainly blew) but only 900 m north-northeast.
  • For both men and women, SMRs showed a linear dose-response relation with relative asbestos concentration. The men's line was significantly less steep than the women's.
  • Results did not change after excluding 11 subjects who had lived with household members who could have been exposed to asbestos at work.
• The authors' conclusion: The authors concluded that the mesothelioma outbreak among residents was causally associated with asbestos, in particular crocidolite, used by the plant. They also concluded that the affected area spread as far as 2,200 m from the plant's center in a dose-dependent way.
• Limitations the authors state:
  • The interviewees were individuals or their families who voluntarily contacted the compensation agent, and there was no mesothelioma registry, so not all deaths could be enrolled. The authors said selection bias must exist and that it would lead to underestimated SMRs.
  • Classifying whether subjects had work exposure to asbestos involved inevitable misclassification. The broad job list used tends to produce false positives, which the authors said would underestimate the SMRs.
  • Occupationally exposed cases were excluded from observed deaths but could not be excluded from expected deaths. The authors said this underestimates the SMRs, likely more for men than for women.
  • Underestimating the population at risk could overestimate the SMRs, though the authors considered large errors unlikely.
  • Actual airborne asbestos concentrations around the plant were unknown, so only modeled relative concentrations were used.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Asbestos Exposure, Environmental Exposure, standardized mortality ratio (SMR), Asbestos-Cement, Crocidolite, Chrysotile, Occupational Exposure.

Related studies

• Increased risk of lung cancer mortality among residents near an asbestos product manufacturing plant — S. Kumagai, N. Kurumatani, et al. (2010)
• Association of mesothelioma deaths with neighborhood asbestos exposure due to a large-scale asbestos-cement plant — Y. Kitamura, L. Zha, et al. (2023)
• Asbestos related diseases in Italy: an integrated approach to identify unexpected professional or environmental exposure risks at municipal level — A. Marinaccio, A. Scarselli, et al. (2008)
• Malignant mesothelioma from neighborhood exposure to anthophyllite asbestos — W.N. Rom, S.P. Hammar, et al. (2001)
• Relationships of Lower Lung Fibrosis, Pleural Disease, and Lung Mass with Occupational, Household, Neighborhood, and Slate Roof-Dense Area Residential Asbestos Exposure — D. Kang, Y.Y. Kim, et al. (2018)
• Re: Malignant mesothelioma from neighborhood exposure to anthophyllite asbestos — M. Kottek, D. Kilpatrick (2002)

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