Review of occupational lung carcinogens

Our plain-English summary of Review of occupational lung carcinogens, by K. Steenland, D. Loomis, C. Shy, et al (American Journal of Industrial Medicine, 1996).

The study

• Authors: K. Steenland, D. Loomis, C. Shy, N. Simonsen
• Journal: American Journal of Industrial Medicine
• Published: 1996;29(5):474-90
• Type of article: Review
• Cited by: 126 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Lung cancer is the most common malignancy in the United States and is ranked second only to bladder cancer in the proportion of cases thought to be due to occupational exposures. We review the epidemiology of occupational lung cancer, focusing on agents identified as pulmonary carcinogens by the International Agency for Research on Cancer. We derive estimates of overall relative risks from the major studies of these lung carcinogens, and we also provide estimates of the number of exposed workers. Using our data as well as estimates from other authors, we estimate that approximately 9,000-10,000 men and 900-1,900 women develop lung cancer annually in the United States due to past exposure to occupational carcinogens. More than half of these lung cancers are due to asbestos. This estimate is likely conservative, in that we have restricted our analysis to confirmed lung carcinogens and have ignored occupations with documented excess risk but for which the specific agents are unknown. Also, our estimate of the proportion of workers exposed in the past is probably too low. Our estimate should be viewed only as broad approximation. Nevertheless, it is in line with other estimates by authors using different methods. The current number of cases estimated to be due to occupational exposure reflects past high exposures and is likely to drop in the future, unless other occupational lung carcinogens are confirmed or new carcinogens are introduced into the workplace.

In plain English

This article was a review. The authors reviewed studies of agents that the International Agency for Research on Cancer classed as definite or probable lung carcinogens, including asbestos, silica, diesel exhaust, radon and several metals. They combined results across studies into summary relative risks and, with counts of exposed U.S. workers, estimated how many lung cancers work exposures cause. For cohort studies of people with asbestosis or x-ray abnormalities, the combined relative risk for lung cancer was 5.91 (95% CI 4.98-7.00). For larger cohort studies of asbestos workers it was 2.00 (95% CI 1.90-2.11). Using an earlier estimate by Nicholson and colleagues, the authors put asbestos-related lung cancers at about 6,000 a year among U.S. men and perhaps 600 among women. Overall they estimated about 9,000 work-related lung cancers a year among U.S. men and 900 among women, or 10,000 and 1,900 if radon at work was counted. Asbestos accounted for the majority. The authors called this a broad approximation, attributed most current cases to heavy past exposures, and expected cases to fall unless new occupational lung carcinogens are introduced or discovered.

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: Review of epidemiologic studies, with summary relative risks combined across studies using inverse-variance weighting and a random effects model, and estimates of attributable lung cancer cases
• Who was studied: Published cohort and case-control studies of workers exposed to agents IARC classed as definite (Group 1) or probable (Group 2A) lung carcinogens. For asbestos, these were cohort studies of people with asbestosis or radiographic abnormalities and larger cohort studies of asbestos workers. The estimates applied to the U.S. population.
• Exposure: Occupational lung carcinogens including asbestos, silica, diesel exhaust, radon, arsenic, chromium, nickel, cadmium and beryllium. For asbestos, the reviewed studies covered chrysotile, amosite and crocidolite workers in mines, textile, friction product, cement and insulation work. About 700,000 U.S. workers were estimated to be exposed to asbestos in the 1980s.
• Main results:
  • Cohort studies of people with asbestosis or radiographic abnormalities: combined lung cancer relative risk 5.91 (95% CI 4.98-7.00). Individual rate ratios ranged from 3.5 to 9.1.
  • Larger cohort studies of asbestos workers: combined lung cancer relative risk 2.00 (95% CI 1.90-2.11)
  • Asbestos: the authors accepted Nicholson et al.'s estimate of 5,400 excess lung cancer deaths a year among U.S. males in the mid-1990s, which they said corresponds to about 6,000 annual cases. Assuming a 10 to 1 male to female ratio, about 600 more cases might occur among women.
  • Seven other agents (diesel exhaust, silica, arsenic, chromium, nickel, cadmium, beryllium): about 3% of male lung cancers, or 3,000 cases a year, plus 300 cases among females
  • Excluding radon at work: about 9,000 annual lung cancer cases among U.S. males (about 9% of cases) and perhaps 900 among females (2%). Including radon at work: 10,000 among males and 1,900 among females. Asbestos accounted for the majority of attributable cases.
  • Other agents: combined relative risk 2.80 (95% CI 2.50-3.15) for 15 studies of people with silicosis, and 1.33 (95% CI 1.21-1.45) for silica-exposed workers
• The authors' conclusion: The authors concluded that their estimate was imprecise and only a broad approximation, but in line with prior estimates. They stated that most work-related lung cancers today result from heavy past exposures. They said attributable cases are likely to diminish unless new occupational carcinogens are introduced into the workplace or other unknown occupational lung carcinogens are discovered.
• Limitations the authors state:
  • Reliance on historical relative risks, which may lead to overestimation
  • Restriction to confirmed carcinogens, which may lead to underestimation
  • Inaccurate estimates of the proportion of workers exposed in the relevant period, which may lead to underestimation. The authors assumed this proportion stayed constant over time, which they noted is clearly untrue for asbestos.
  • Lack of data to properly account for interaction between smoking and the agents studied
  • For asbestos, good estimation of exposure-response is difficult because most studies have few historical measurements, and converting old dust-count units to current units is problematic

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, Occupational Exposure, Epidemiology, Relative Risk.

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