Development of Nationwide Excess Lifetime Cancer Risk Evaluation Methods with Comprehensive Past Asbestos Exposure Reconstruction

Our plain-English summary of Development of Nationwide Excess Lifetime Cancer Risk Evaluation Methods with Comprehensive Past Asbestos Exposure Reconstruction, by D. Kang, S.H. Lee, Y.J. Kim, et al (International Journal of Environmental Research and Public Health, 2021).

The study

• Authors: D. Kang, S.H. Lee, Y.J. Kim, T.K. Kim, J.Y. Kim, Y. Kim
• Journal: International Journal of Environmental Research and Public Health
• Published: 2021;18(6)
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Although exposure to asbestos via various routes has been acknowledged, comprehensive exposure and risk assessment methods have not been developed at the national level. We conducted a study to reconstruct comprehensive past asbestos exposure estimations and to suggest a method to calculate the Excess Lifetime Cancer Risk (ELCR) of Koreans. The past occupational exposure reconstruction was conducted by rebuilding the previous general population job-exposure matrix (JEM). The para-occupational and household exposure estimation was based on the pooled analysis of data from other countries as well as Korea. The neighborhood exposure from occupational sources by distance was estimated by the exponential decay model. As a result, 141 JEM exposure groups across four periods including ~79, the 80s, 90s, 2000s with a ratio of 2.0:1.0:0.5:0.05 were reconstructed. The para-occupational and household exposures were 11% and 1% of the JEM respectively. The environmental exposure source concentration from outside occupational exposure was 2.5% of the inside concentration. The ratio of the concentration of environmental exposure source (C0) to distance d (Cd) was exp-kd  with a decay constant k of 6.834. The mean concentrations (f/cc) were 2.28 × 10-3 for outdoor, 4.65 × 10-5 for indoor, 1.95 × 10-2 for transportation activity, 4.44 × 10-2 for agricultural activity, and 4.68 × 10-2 for daily life activity in naturally occurring asbestos areas. Indoor and outdoor asbestos concentrations from living in a slate roof house were 1.73 × 10-6 and 2.70 × 10-8, respectively. For improved generalizability, validity, and applicability of the proposed method, further studies on each route with real assessments and experiments are required.

In plain English

In this methods-development study, the authors built a way to estimate Koreans' past asbestos exposure through several routes and convert it into an Excess Lifetime Cancer Risk (ELCR). They filled gaps in an existing Korean job-exposure matrix of 141 industry-and-occupation groups. For jobs directly producing asbestos-containing materials, they assumed levels before 1979, in the 1980s, 1990s and 2000s in the ratio 2.0:1.0:0.5:0.05. Other jobs reused values from adjacent decades. Pooled studies put co-workers' indirect exposure at 11% of direct occupational exposure, and household exposure from an exposed family member at 1%. From one factory study, outside air was estimated at 2.5% of inside levels, falling with distance in kilometres at a decay constant of 6.834 (95% confidence interval 3.466 to 10.222). Korean studies gave mean concentrations in naturally occurring asbestos areas from 4.65 × 10−5 f/cc indoors to 4.68 × 10−2 f/cc during daily life activity. The authors stated that the method could not be validated and that results cannot be generalized, a problem they called specific to the distance-based neighborhood estimate. They called for further studies using real assessments and experiments.

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: Methods-development study: reconstruction of a job-exposure matrix plus pooled analyses of published literature, combined into a lifetime cancer risk calculation method
• Who was studied: No new people were studied. The work used an existing Korean asbestos job-exposure matrix of 141 industry-occupation exposure groups for the 1980s to 2000s, extended to before 1979. It also pooled published studies: 17 on para-occupational exposure and 11 on household exposure, from Korea and other countries; and 16 on naturally occurring asbestos areas and 8 on slate roofs, from Korea only.
• Exposure: Airborne asbestos in fibers per cubic centimeter (f/cc), with no fiber type specified, from six routes: occupational, para-occupational, neighborhood exposure from occupational sources by distance, naturally occurring asbestos areas, living under a slate roof house, and household exposure from an occupationally exposed family member
• Main results:
  • In the 10 exposure groups with data in all three decades, mean concentrations were 1.41 f/cc in the 1980s, 0.57 f/cc in the 1990s and 0.06 f/cc in the 2000s.
  • The authors used ratios of 2.0 (up to 1979), 1.0 (1980s), 0.5 (1990s) and 0.05 (2000s), with the 2.0 for the period before 1979 an assumption they called conservative. These ratios filled gaps for jobs directly involved in producing asbestos-containing materials. Other jobs were filled with the same data as adjacent values.
  • Pooled analysis put para-occupational (indirect, same workplace) exposure at 11% of direct occupational exposure.
  • Pooled analysis put household exposure from an occupationally exposed family member at 1% of that member's occupational exposure.
  • From one earlier factory study, mean concentration was 2.4003 f/cc inside and 0.0601 f/cc outside. The outside level was 2.5% (SD 1.1%) of the inside level.
  • In the model of how concentration falls with distance (in km) from a source, the decay constant k was 6.834 (95% confidence interval 3.466 to 10.222; R squared 0.81).
  • In naturally occurring asbestos areas in Korea, mean concentrations were 2.28 × 10−3 f/cc outdoors, 4.65 × 10−5 f/cc indoors, 1.95 × 10−2 f/cc during transportation activity, 4.44 × 10−2 f/cc during agricultural activity and 4.68 × 10−2 f/cc during daily life activity.
  • For living in a slate roof house, indoor and outdoor asbestos concentrations were 1.73 × 10−6 and 2.70 × 10−8 respectively. No unit is printed with these values.
  • The proposed method adds up the risk from all six routes using an inhalation unit risk of 0.23 per f/mL. It then sorts the final risk into four grades: very high (1.0 × 10−4 or more), high, moderate and low (below 1.0 × 10−6).
• The authors' conclusion: The authors concluded that they had developed a nationwide method for assessing past asbestos exposure in Korea. They added that further studies on each route with real assessments and experiments are required to improve its generalizability, validity and applicability.
• Limitations the authors state:
  • Generalizability: data were sparse, so the analysis rested on the few available studies and the results cannot be generalized. The authors said this problem is specific to the estimate of neighborhood exposure by distance from occupational sources.
  • The authors said applying the results to countries other than Korea is difficult.
  • Validity: the method could not be validated.
  • Applicability: the method needs comprehensive databases, including the job-exposure matrix and national exposure sources, which few countries would build.
  • Pooled analysis of dispersion from occupational sources was not possible because few studies existed. Only one study had measured inside and outside a factory at the same time.
  • No occupational exposure data from Korea were found from before 1984, so levels before 1979 were estimated rather than measured.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Occupational Exposure, Meta-Analysis, Environmental Exposure, naturally occurring asbestos (NOA).

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