Asbestos fiber concentration in the area surrounding a former asbestos cement plant and excess mesothelioma deaths in residents

Our plain-English summary of Asbestos fiber concentration in the area surrounding a former asbestos cement plant and excess mesothelioma deaths in residents, by S. Kumagai, N. Kurumatani (American Journal of Industrial Medicine, 2009).

The study

• Authors: S. Kumagai, N. Kurumatani
• Journal: American Journal of Industrial Medicine
• Published: 2009;52(10):790-8
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Many persons who had lived near a former asbestos cement plant (AC plant) died from mesothelioma in Amagasaki city, Japan.

Methods: Asbestos fiber concentration in the area surrounding the AC plant was estimated so that the female mesothelioma death number predicted by a mathematical model was the same as the observed excess death number. We used the estimated asbestos fiber concentration to predict the excess mesothelioma deaths from 1970 to 2049.

Results: In a grid just south of the AC plant, the fiber concentration was estimated to be more than 3 f/ml for K(M) (asbestos potency factor for mesothelioma) of 7.75 x 10(-9). An uncertainty factor of five yields a K(M) range 1.55 x 10(-9) to 38.8 x 10(-9); these in turn correspond to fiber concentrations of 15 and 0.6 f/ml. For K(M) = 7.75 x 10(-9), grid units with higher fiber concentrations than 0.01 f/ml were estimated to extend 4.1 km (95% CI: 3.8-4.4 km) south-southwest of the plant. Over the 80-year study period (1970 to 2049), we predicted that the exposure under study will cause 346 excess mesothelioma deaths with range of 296 to 382 deaths.

Conclusions: This prediction suggests that considerable medical resources will be needed through 2049 as a result of past asbestos exposure in this region.

Copyright 2009 Wiley-Liss, Inc.

In plain English

This modeling study estimated airborne asbestos around a former Kubota asbestos cement plant in Amagasaki, Japan, which used crocidolite and chrysotile from 1957 to 1975. They used a U.S. EPA risk model with a standard potency value and values five times lower and higher. They started from 39 women with no work exposure who had lived in one of five areas near the plant for at least a year in 1957 to 1975 and died of mesothelioma in 1995 to 2006. They fitted the model to excess deaths: observed minus expected, using national female rates cut to 60% to exclude assumed work-related deaths. With the standard value, area estimates ranged from 0.014 to 0.51 fibers per milliliter (f/ml). One grid just south of the plant exceeded 3 f/ml. Areas above 0.01 f/ml reached 4.1 km south-southwest (95% CI 3.8 to 4.4 km). The model predicted 346 excess mesothelioma deaths (range 296 to 382) from 1970 to 2049. The authors called the concentrations model-based equivalents, not actual values. They concluded this prediction suggests considerable medical resources will be needed through 2049.

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: Mathematical modeling (risk assessment) study. The authors estimated airborne fiber concentrations by fitting a U.S. EPA mesothelioma model to observed excess female mesothelioma deaths (observed minus adjusted expected deaths). They then used these concentrations to predict future excess deaths.
• Who was studied: Residents living near a former asbestos cement plant of Kubota Corp. in Amagasaki city, Hyogo prefecture, Japan.
• Fiber levels were estimated from 39 women who had lived in one of five areas around the plant for at least 1 year between 1957 and 1975, died from mesothelioma between 1995 and 2006, and lacked occupational exposure to asbestos.
• Future deaths were predicted for male and female residents.
• About 117,900 people (range 110,100 to 124,900) were estimated to have lived in 1957 where concentrations were 0.01 f/ml or more.
• Exposure: Neighborhood (residential) exposure to asbestos emitted from the plant while it used crocidolite and chrysotile, 1957 to 1975. The plant also made building material with chrysotile from 1971 to 1995. The model assumed exposure 24 hours a day and indoor levels equal to outdoor levels. Air at the plant site was not measured until 1982.
• Main results:
  • Fiber concentrations were fitted to the observed excess female deaths in each area, defined as observed deaths minus expected deaths. The expected value from national female mesothelioma mortality was multiplied by 60%, because the authors assumed 40% of female mesothelioma deaths in Japan were related to occupational exposure.
  • Estimated asbestos fiber concentrations in the five areas around the plant:
• 0.014 to 0.51 f/ml with the standard potency value (KM of 7.75 × 10^-9).
• 0.070 to 2.54 f/ml with the lower potency value.
• 0.003 to 0.10 f/ml with the higher potency value.
  • In a grid unit just south of the plant, estimated concentrations were more than 15 f/ml (lower potency value), more than 3 f/ml (standard value), and more than 0.6 f/ml (higher value).
  • Higher estimated concentrations lay south-southwest of the plant. The authors said this fit the area's predominant wind, which blew from north-northeast to south-southwest.
  • With the standard potency value, grid units above 0.01 f/ml were estimated to extend:
• 4.1 km south-southwest (95% CI 3.8 to 4.4 km)
• 1.5 km north-northeast
• 1.0 km northwest
• 1.6 km southeast
  • The authors used three values of the transformation constant. For these three values:
• Estimated residents exposed at 0.01 f/ml or more in 1957: 110,100, 117,900, and 124,900.
• Predicted excess mesothelioma deaths from 1970 to 2049: 296, 346, and 382.
  • For the central estimate, predicted excess deaths rose from one in the 1970s to 79 in the 2020s, then fell to 39 in the 2040s.
  • A diesel engine plant stood just south of the asbestos cement plant.
• Its estimated concentration averaged about 1.5 f/ml with the standard potency value.
• Eleven male workers and one female worker there had been diagnosed with mesothelioma.
• The authors said it is plausible that asbestos from the cement plant caused mesothelioma in these workers.
• The authors' conclusion: The authors concluded that their prediction suggests considerable medical resources will be needed through 2049 because of past asbestos exposure in this region. They also said that intervention to limit future asbestos exposure will be necessary in this and other communities. They added that total mesothelioma deaths among people who lived in the area are predicted to be higher still, because expected background deaths must be added to the excess deaths.
• Limitations the authors state:
  • The authors relied on a number of assumptions to estimate fiber concentrations.
  • The potency value came from occupational cohort studies, and its suitability for residential exposure is unclear. The estimated concentrations are therefore toxic-equivalent values, not actual concentrations.
  • The constant used to convert relative concentrations into fiber concentrations rested on only five data points and depended heavily on a single value.
  • Seven of the 39 women had lived with household members who could have been exposed to asbestos at work. For these women, domestic and residential exposure could not be separated.
  • Indoor asbestos concentration was assumed to equal outdoor concentration. Accumulation or re-entrainment of fibers in houses was not considered.
  • The population at risk may have been larger than estimated if in-migration between 1957 and 1974 is considered.
  • Airborne asbestos was not measured at the plant until 1982, so neighborhood exposure levels during the crocidolite period were unknown.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Mesothelioma, Asbestos Exposure.

Related studies

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• 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)
• Association of mesothelioma deaths with neighborhood asbestos exposure due to a large-scale asbestos-cement plant — Y. Kitamura, L. Zha, et al. (2023)
• Emission of airborne fibers from mechanically impacted asbestos-cement sheets and concentration of fibrous aerosol in the home environment in Upper Silesia, Poland — J.S. Pastuszka (2009)
• Mortality in a cohort of cement workers in a plant of Central Italy — F. Giordano, V. Dell'orco, et al. (2012)

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