Increased risk of lung cancer mortality among residents near an asbestos product manufacturing plant

Our plain-English summary of Increased risk of lung cancer mortality among residents near an asbestos product manufacturing plant, by S. Kumagai, N. Kurumatani, T. Tsuda, et al (International Journal of Occupational and Environmental Health, 2010).

The study

• Authors: S. Kumagai, N. Kurumatani, T. Tsuda, T. Yorifuji, E. Suzuki
• Journal: International Journal of Occupational and Environmental Health
• Published: 2010;16(3):268-78
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We investigated whether individuals exposed to asbestos by living near an asbestos-manufacturing facility experienced increased lung cancer mortality. We studied a neighborhood around such a plant in the central Japanese city of Hashima. From 1943 to 1991 this plant produced insulation and packing material using amosite- and chrysotile-type asbestos fibers. The study group was comprised of 577 households. We obtained demographic information by a questionnaire and determined the underlying cause of death for deceased household members from death certificates. Using hourly meteorological data from local observatories, we estimated relative asbestos concentrations in the plant's vicinity, determined the quartile boundaries, and designated each study subject's quartile of ambient exposure. Finally, we calculated standardized mortality ratios to evaluate the association of residential asbestos with lung cancer risk. Our findings strongly suggest that neighborhood asbestos exposure can increase the risk of lung cancer mortality in men and probably in women.

In plain English

The authors studied deaths among residents of eight districts near an asbestos products plant in Hashima, Japan, that operated from 1943 to 1991. Under its later owner the plant used mainly amosite and chrysotile plus a small amount of crocidolite. Members of 502 households (951 men, 956 women) were followed from January 1992 to June 30, 2007. Observed deaths were compared with deaths expected from Japanese national rates, as standardized mortality ratios (SMRs). Homes were grouped into quartiles of relative asbestos concentration estimated from wind data. Men had 22 lung cancer deaths (SMR 2.15, 95% CI 1.35–3.25). Women had 5 (SMR 1.47, 95% CI 0.48–3.42, not statistically significant). After excluding eight lung cancer deaths with occupational asbestos exposure, the SMR in the highest-exposure quartile was 2.94 (95% CI 1.27–5.79) for men and 3.52 (95% CI 0.73–10.3, not significant) for women. No study subject died of mesothelioma during follow-up. The authors concluded that lung cancer mortality without occupational exposure was highest in the most exposed neighborhoods, significantly so for men.

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: Residential cohort mortality study. Deaths from January 1, 1992 to June 30, 2007 were compared with deaths expected from Japanese national rates (standardized mortality ratios), with residents grouped by modeled relative asbestos concentration.
• Who was studied: Members of households in eight districts around the plant in Hashima, Gifu prefecture, Japan. 577 households were eligible and complete follow-up was obtained for 502 (87.0%): 951 men and 956 women, with 13,935 person-years in men and 14,128 person-years in women.
• Exposure: Neighborhood (non-occupational) exposure to emissions from a plant making insulation, calcium silicate board and packing material, mainly from amosite and chrysotile plus a small amount of crocidolite (1943 to 1991). Exposure was estimated as a relative airborne concentration at each home, using a dispersion model based on 2002 to 2006 weather data, and divided into quartiles (exposure groups 1 to 4). Actual concentrations were not known.
• Main results:
  • Neither men nor women in the whole cohort had significantly higher overall (all-cause) mortality.
  • Lung cancer in the whole cohort: men had 22 observed vs 10.2 expected deaths (SMR 2.15, 95% CI 1.35–3.25). Women had 5 observed vs 3.4 expected deaths (SMR 1.47, 95% CI 0.48–3.42).
  • Of the 22 men and 5 women who died of lung cancer, 7 men and 1 woman had occupational asbestos exposure. Three men and one woman had worked at the asbestos plant, three men in construction, and one man as a car mechanic.
  • After excluding lung cancer deaths with occupational asbestos exposure, whole-cohort lung cancer SMRs were 1.46 (95% CI 0.82–2.41) in men and 1.17 (95% CI 0.32–3.00) in women, neither statistically significant. The authors state these SMRs were underestimated because the excluded cases were not removed from the expected numbers.
  • After excluding cases with occupational asbestos exposure, lung cancer SMRs were highest in exposure group 4 (highest estimated concentration): 2.94 (95% CI 1.27–5.79) in men, which was statistically significant, and 3.52 (95% CI 0.73–10.3) in women, which was not.
  • The excess for men in exposure group 4 remained significant after also excluding two men with possible occupational silica exposure from foundry work.
  • Comparison of deaths without occupational asbestos exposure: a higher share of lung cancer deaths than other deaths lived in exposure group 4. In men this was 8 of 15 (53.3%) vs 21 of 95 (22.1%), p = 0.011. In women it was 3 of 4 (75.0%) vs 27 of 108 (25.0%), p = 0.027.
  • Among men, a history of smoking was more common in lung cancer deaths (14 of 15, 93.3%) than in deaths from other causes (53 of 95, 55.8%), p = 0.006. Their Brinkman (smoking amount) indices were not higher.
  • No study subject died from malignant mesothelioma during follow-up. The authors separately describe pleural mesothelioma cases in nearby people who were not in the cohort, including a woman in the highest-exposure area who died in 1989, before follow-up began.
• The authors' conclusion: The authors concluded that, near the Nichias plant, lung cancer mortality among people without occupational asbestos exposure was highest in the most highly exposed neighborhoods for both men and women. For men it was significantly higher than in the national reference population. They described their findings as suggesting that neighborhood asbestos exposure caused the lung cancer deaths.
• Limitations the authors state:
  • Actual past airborne asbestos concentrations could not be determined. Only relative concentrations were estimated, using an assumed emission rate and weather data from 2002 to 2006.
  • Smoking amount and duration were obtained for only 63% of smokers, so the Brinkman index was only a rough estimate.
  • It is difficult to confirm that a person never had workplace asbestos exposure over a whole lifetime.
  • 75 of the 577 study households (13%) did not respond. Separately, 162 households whose members had all moved away or died were excluded.
  • The female result for exposure group 4 was probably not significant because there were too few person-years of observation. The authors also attribute the absence of mesothelioma deaths to the small person-years.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Amosite, Chrysotile, Death Certificate, standardized mortality ratio (SMR), Asbestos Exposure.

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