Asbestos Exposure Level and the Carcinogenic Risk Due to Corrugated Asbestos-Cement Slate Roofs in Korea

Our plain-English summary of Asbestos Exposure Level and the Carcinogenic Risk Due to Corrugated Asbestos-Cement Slate Roofs in Korea, by E.S. Lee, Y.K. Kim (International Journal of Environmental Research and Public Health, 2021).

The study

• Authors: E.S. Lee, Y.K. Kim
• Journal: International Journal of Environmental Research and Public Health
• Published: 2021;18(13)
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos-cement slate roofs are one of the most common environmental causes of asbestos exposure. However, few studies have examined residential asbestos-cement slate-related exposure and its effects on human health. This study was performed to evaluate cumulative asbestos exposure levels and to calculate the Excess Lifetime Cancer Risk (ELCR) of residents of asbestos-cement slate-roofed houses. We reviewed previous Korean literature to estimate the concentration of airborne asbestos from asbestos-cement slate roofed buildings. Finally, eight studies were selected, and a pooled analysis was performed. The results derived from the pooled analysis were combined with the data from a health impact survey conducted from 2009 to 2016 at the Environmental Health Center for Asbestos (EHCA) of the Yangsan Pusan National University Hospital, and a carcinogenic risk assessment was performed. As a result, the representative value of the indoor exposure concentration related to asbestos-cement slate was found to be 0.0032 f/cc on average, and the representative value of the exposure related to occupational asbestos-cement slate dismantling and demolition was found to be 0.0034 f/cc. In addition, the ELCR of asbestos-cement slate related indoor exposure and occupational dismantling and demolition was found to be of medium risk, and the ELCR of residential dismantling and demolition of asbestos-cement slate was less than 10-6, indicating that the risk was low. Since there is no threshold for carcinogenicity related to asbestos, this should not be ignored even if the risk appears low, and it would be reasonable to calculate the carcinogenic risk based on total lifetime exposure. More studies on asbestos exposure scenarios and the scope of similar exposure groups through additional data collection and further analysis of risk are needed.

In plain English

This Korean study estimated asbestos exposure from asbestos-cement slate roofs, described as containing 10–20% chrysotile. It calculated Excess Lifetime Cancer Risk (ELCR) using a US Environmental Protection Agency formula. The authors pooled measurements from eight Korean studies and applied them to 2009–2016 survey data on 575 people whose only reported asbestos exposure was slate. Representative concentrations were 0.0032 f/cc indoors and 0.0034 f/cc for occupational roof dismantling. Finding no research on residents' own repairs, the authors estimated that scenario from occupational data. Average ELCR was 4.81 × 10⁻⁵ (95% CI 4.52 to 5.10 × 10⁻⁵), or 4.81 per 100,000 people, for indoor exposure; 5.11 × 10⁻⁵ (4.80 to 5.41 × 10⁻⁵) using the occupational dismantling value; and 2.75 × 10⁻⁷ (2.58 to 2.92 × 10⁻⁷) for residents' own repairs. The authors called the first two medium and the last low risk, though the article states its cut-offs inconsistently. The authors concluded that because asbestos has no cancer threshold, even low risk should not be ignored. They noted limited data, fiber counts not specific to asbestos, and categorical survey answers.

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: Pooled analysis of airborne asbestos measurements from eight published Korean studies, combined with survey data in a cancer risk assessment (ELCR = exposure concentration × time weighting factor × inhalation unit risk, following US EPA guidance)
• Who was studied: Health impact survey conducted 2009–2016 at the Environmental Health Center for Asbestos, Pusan National University Yangsan Hospital, Korea. Of 11,191 subjects, 1228 were classed as asbestos-cement slate exposed because they lived in slate-roofed houses or slate-dense areas. Risk was calculated for the 575 of these with no other asbestos exposure (the 'only slate-exposed group'). Measurement data came from eight Korean studies published up to December 2019.
• Exposure: Asbestos-cement slate roofing (described as 10–20% chrysotile in cement). Scenarios were indoor and outdoor air at slate-roofed buildings, occupational slate roof dismantling and demolition, and residents repairing or dismantling their own roofs (estimated). The pooled studies counted fibers by phase-contrast microscopy.
• Main results:
  • Representative airborne concentrations from the pooled analysis: 0.0032 f/cc on average for indoor exposure in slate-roofed houses, and 0.0034 f/cc for asbestos-cement slate dismantling and demolition (occupational data)
  • The authors' review found no related research on residents repairing or dismantling their own slate roofs. They estimated that scenario from occupational dismantling results, assuming one repair every 5 years.
  • Of the 1228 slate-exposed survey subjects, 575 had no occupational, family or other environmental asbestos exposure
  • Of the 1228 slate-exposed survey subjects, 362 (29.48%) said they had carried out asbestos-cement slate roof repairs
  • Average cumulative exposure in the only slate-exposed group: 0.044 fiber-years/cc for indoor exposure and 0.047 fiber-years/cc using the occupational dismantling and demolition value
  • Estimated average cumulative exposure from residents dismantling and demolishing their own slate roofs: 0.000251 fiber-years/cc
  • Average ELCR in the only slate-exposed group: 4.81 × 10⁻⁵ for indoor exposure (expressed by the authors as 4.81 per 100,000 people), and 5.11 × 10⁻⁵ using the dismantling and demolition value
  • 95% confidence interval for the average indoor-exposure ELCR in the 575 only slate-exposed subjects (Table 5): 4.52 × 10⁻⁵ to 5.10 × 10⁻⁵
  • 95% confidence interval for the average ELCR using the occupational dismantling value in the 575 subjects (Table 5): 4.80 × 10⁻⁵ to 5.41 × 10⁻⁵
  • Average ELCR for residents involved in dismantling and demolishing slate: 2.75 × 10⁻⁷ (expressed by the authors as 2.75 per 10,000,000 people)
  • 95% confidence interval for the average residential repair or dismantling ELCR in the 575 subjects (Table 5): 2.58 × 10⁻⁷ to 2.92 × 10⁻⁷
  • For indoor exposure, 89.22% of the 575 people (513 in Table 6) fell in the intermediate (moderate) risk category. Table 6 lists 27 (4.70%) as low and 35 (6.09%) as high.
  • Cumulative exposure tended to increase with age in all scenarios and did not vary by sex
• The authors' conclusion: The authors concluded that ELCR from indoor slate exposure and occupational dismantling was of medium risk, and that ELCR from residents' own dismantling was low. Because there is no threshold for asbestos-related cancer, they said even low risk should not be ignored and that it would be reasonable to calculate risk from total lifetime exposure. They called for further study.
• Limitations the authors state:
  • There was too little published measurement data to classify exposure scenarios comprehensively
  • Each scenario had too few samples to be representative
  • Most source studies used phase-contrast microscopy rather than transmission electron microscopy, so the counts may not be specific to asbestos
  • Converting geometric means to arithmetic means produced outliers that could cause inaccuracies
  • The survey data were only categorical, which made exposure hard to evaluate accurately
  • When slate roofs were in use depended on subjects' memories
  • The time weighting factor may have been underestimated because residents were generally older and the time of first residence was not accurately determined. The authors suggested this as a possible reason their risk estimates were lower than two earlier Korean studies.
  • Indoor time was estimated for Korean adults without distinguishing men and women, and the survey did not identify which family members did repairs
  • Approximate inhalation unit risk values were used where exact values could not be found

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Carcinogenic, Asbestos-Cement, Meta-Analysis.

Related studies

• Mobilization of asbestos fibers by weathering of a corrugated asbestos cement roof — T. Ervik, S. Eriksen Hammer, et al. (2021)
• 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)
• Changes in concentrations and characteristics of asbestos fibers dispersed from corrugated asbestos cement sheets due to stabilizer treatment — H.S. Jung, J. Jang, et al. (2021)
• Predicting the mortality from asbestos-related diseases based on the amount of asbestos used and the effects of slate buildings in Korea — S.Y. Kim, Y.C. Kim, et al. (2016)
• Risk assessment of the decay of asbestos cement roofs — A. Campopiano, D. Ramires, et al. (2009)
• Activity-Based Exposure Levels and Cancer Risk Assessment Due to Naturally Occurring Asbestos for the Residents Near Abandoned Asbestos Mines in South Korea — S. Lee, D. Kang, et al. (2021)

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