Occupational asbestos exposure and mesothelioma risk in Los Angeles County: application of an occupational hazard survey job-exposure matrix

Our plain-English summary of Occupational asbestos exposure and mesothelioma risk in Los Angeles County: application of an occupational hazard survey job-exposure matrix, by C. Cicioni, S.J. London, D.H. Garabrant, et al (American Journal of Industrial Medicine, 1991).

The study

• Authors: C. Cicioni, S.J. London, D.H. Garabrant, L. Bernstein, K. Phillips, J.M. Peters
• Journal: American Journal of Industrial Medicine
• Published: 1991;20(3):371-9
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We evaluated the newly available National Institute for Occupational Safety and Health (NIOSH) National Occupational Hazard Survey (NOHS) job exposure matrix (JEM) by considering mesothelioma risk from asbestos exposure. We applied this system (NOHS-JEM) to the Los Angeles County Cancer Surveillance Program (CSP) to see how many cancer cases could be assigned asbestos exposure and how asbestos exposure affected mesothelioma risk. Using the same CSP data, our "experts" classified asbestos exposure simply by occupation and industry. Both exposure classifications were divided into low and high; the NOHS-JEM by the number of exposed people per couplet, and ours by judgements of intensity. Odds ratios (OR) for mesothelioma risk for low and high asbestos exposure for the NOHS-JEM were 2.0 (95% C.I. 1.2-3.4) and 2.5 (95% C.I. 1.2-4.8). For ours, corresponding risks were 1.6 (95% C.I. 1.1-2.4) and 6.3 (95% C.I. 2.5-15.1). Our system was able to assign more cases to couplets then the NOHS-JEM (35,895 to 22,369). Three limitations of the NOHS-JEM were that many occupation-industry couplets were not classified at all, many couplets associated with past asbestos exposure (before the 1972-1974 NOHS survey) were not classified as asbestos exposure, and no assessment of intensity was made. These limitations may apply to other exposures and should be carefully considered before the NOHS-JEM is applied to other case-control studies.

In plain English

This study used a Los Angeles County cancer registry to compare two ways of estimating occupational asbestos exposure from a person's job and industry. Among men aged 18 to 64 diagnosed with cancer in 1972-1988, it compared 143 men with mesothelioma to 35,752 men with other cancers, leaving out lung cancer. One method used a job-exposure matrix built from a 1972-1974 national survey (the NOHS-JEM). The other used the authors' own ratings of each job and industry as no, low or high exposure. With the NOHS-JEM, crude odds ratios for mesothelioma were 2.0 (95% CI 1.2-3.4) for lower and 2.5 (1.2-4.8) for higher exposure probability. With the authors' ratings they were 1.6 (1.1-2.4) for low and 6.3 (2.5-15.1) for high exposure. The two methods agreed only weakly. The NOHS-JEM could not classify more than a third of cases, and it gave a zero exposure probability to many shipyard jobs that the authors rated high. The authors concluded that job-exposure matrices, including the NOHS-JEM, should be used thoughtfully. The article does not name fiber types or where in the body the mesotheliomas occurred.

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: Case-control analysis of population-based cancer registry data, with patients who had other cancers (lung cancer excluded) as controls. It compared two job-exposure matrices for assigning asbestos exposure.
• Who was studied: Men aged 18-64 in Los Angeles County diagnosed with cancer in 1972-1988 who had occupation and industry recorded, 46,644 cancers in all. The analysis included 143 mesothelioma patients and 35,752 patients with cancers other than lung cancer.
• Exposure: Occupational asbestos exposure inferred from occupation and industry at the time of diagnosis, assigned in two ways. (1) NOHS-JEM: the proportion of surveyed workers in each occupation-industry pair who were exposed to asbestos, grouped as none, above 0 to 0.10, and above 0.10. (2) The authors' own grading of each census occupation and industry code as none, low or high, based on likelihood and intensity of exposure. No fiber types are named.
• Main results:
  • Using the NOHS-JEM, the crude odds ratio for mesothelioma was 2.0 (95% CL 1.2-3.4) for the lower exposure probability and 2.5 (95% CL 1.2-4.8) for the higher exposure probability (above 0.10).
  • Under the NOHS-JEM, 33 of 101 mesothelioma cases had jobs with an asbestos exposure probability above 0. Exposure probability was missing for 42 mesotheliomas and 13,484 cancer controls.
  • Using the authors' classification, the crude odds ratio for mesothelioma was 1.6 (95% CL 1.1-2.4) for low exposure (45 mesotheliomas, 8,189 controls) and 6.3 (95% CL 2.5-15.1) for high exposure (6 mesotheliomas, 282 controls).
  • Under the authors' classification, 51 mesotheliomas (36% of all mesothelioma cases) had jobs classified as asbestos exposed.
  • The two methods were weakly correlated (Spearman correlation coefficient 0.28).
  • Of 288 cancer cases in occupation-industry pairs the authors rated highly exposed, 180 (62.5%) had a NOHS-JEM exposure probability of 0, and 59 (20.5%) were in pairs not included in the NOHS-JEM. Most of these were in the shipyard industry.
  • The cancer cases worked in 7,426 occupation-industry pairs, and 4,116 (55%) of these pairs were not included in the NOHS-JEM.
• The authors' conclusion: The authors concluded that investigators should use all job-exposure matrices, including the NOHS-JEM, thoughtfully. They said such matrices should be one tool for exposure assessment rather than the principal means.
• Limitations the authors state:
  • The NOHS-JEM exposure data were collected in 1972-1974, which may not be the relevant period for causing disease. The authors said this is probably why shipyard workers were not classified as asbestos exposed.
  • Many occupation-industry pairs were not sampled in the NOHS-JEM, so more than one-third of cases could not be assigned an exposure category.
  • The NOHS-JEM is based on a national sample, and exposures in a given industry may vary by locale.
  • The NOHS-JEM gives no estimate of exposure level, only the percentage of workers exposed.
  • The authors' own matrix covers only men under 65, uses information from the time of diagnosis, and is crude, relying on two of the authors' judgements.
  • The authors acknowledged that their knowledge of cancer risks in the registry could have biased their exposure assignments, although they believed their choices were objective.
  • Relying on occupation and industry at the time of diagnosis causes misclassification with either method. Mesothelioma diagnosis also varies between pathologists and regions. The authors said these weaknesses would tend to bias results toward the null.
  • Some occupation-industry pairs treated as unexposed may have involved significant asbestos exposure.

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 Exposure, Mesothelioma, NIOSH, Odds Ratio.

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