Analysis of excess lung cancer risk in short-term employees

Our plain-English summary of Analysis of excess lung cancer risk in short-term employees, by S.H. Lamm, M.S. Levine, J.A. Starr, et al (American Journal of Epidemiology, 1988).

The study

• Authors: S.H. Lamm, M.S. Levine, J.A. Starr, S.L. Tirey
• Journal: American Journal of Epidemiology
• Published: 1988;127(6):1202-9
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000240).

Abstract

An excess of lung cancer found in a cohort of 741 New York State tremolitic talc workers observed from 1947 through 1978 has been shown paradoxically to be concentrated in short-term workers. Review of past work histories suggests that the excess of lung cancer in these short-term workers may be accounted for by prior exposures rather than by exposures at the employment under investigation. This finding has significant implications in view of the developing practice of including short-term workers in occupational cohort studies in contrast to the more traditional practice of excluding short-term workers. The traditional practice was based on the assumption that the inclusion of short-term workers with little exposure, and thus little risk, might dilute an otherwise apparent association between mortality and exposure. This study suggests that in certain instances the inclusion of short-term workers may magnify rather than dilute the estimation of risk, reflecting the presence of confounding variables.

In plain English

The authors reanalyzed mortality for 741 white workers employed at an upstate New York tremolitic talc plant from 1947 to 1977, followed through 1978. Only the 705 men were analyzed statistically. Standardized mortality ratios (SMRs) compared deaths with US white male rates; 100 means as expected. Among all men, lung cancer deaths were raised (12 deaths; SMR 240, confidence interval 124 to 419). The excess was larger, and statistically significant, only in men employed under one year (SMR 317); men employed one year or more had a nonsignificant SMR of 193 (interval 71 to 420). It was also significant in men whose applications listed prior jobs judged risky for lung cancer, such as metal mining (SMR 316), but not in the no-prior-risk group (SMR 117). Deaths from noninfectious, nonneoplastic respiratory disease were raised only in men employed one year or more (SMR 370, interval 136 to 806). The authors concluded that the short-term excess was most likely due to risk acquired elsewhere, such as prior jobs, or to smoking or other behavioral differences. Their smoking information was only anecdotal.

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: Reanalysis of existing cohort mortality data (observed versus expected deaths, standardized mortality ratios), using data originally gathered by Stille and Tabershaw and by NIOSH
• Who was studied: 741 white workers (705 men, 36 women) who ever worked at an upstate New York talc plant from its opening in 1947 through December 31, 1977. They were followed to December 31, 1978. Women were followed but excluded from the statistical analysis. 425 men worked one year or more and 280 worked less than one year.
• Exposure: Employment at a tremolitic talc plant, analyzed by duration (less than one year versus one year or more). Prior jobs on the job application were classified as 'lung cancer risk' (metal mining, steel-making, foundry, roofing, welding, construction, paper mill), 'no prior risk', or unclassifiable.
• Main results:
  • Among all men, lung cancer mortality was significantly elevated (12 deaths, SMR 240; Table 1 confidence interval 124 to 419).
  • Lung cancer mortality was statistically significantly increased in men employed less than one year (SMR 317). Men employed one year or more had an elevated but not statistically significant SMR of 193 (Table 1 confidence interval 71 to 420).
  • Lung cancer mortality was significantly increased in men with prior risk employment (SMR 316) but not in those whose work history showed no such employment (SMR 117).
  • Among the six lung cancer deaths in short-term employees, five had worked three or fewer months at the plant. Two had worked only 8 and 19 days.
  • Nine of the 12 lung cancer deaths were among miners rather than millers, although measured exposures were greater for millers.
  • Deaths from noninfectious, nonneoplastic respiratory disease were raised only in men employed one year or more (6 observed versus 1.6 expected; SMR 370, Table 1 confidence interval 136 to 806).
  • One electrician at the plant died of mesothelioma 15 years after being hired, after 20 years of earlier work as a miner, a miller, or in construction.
• The authors' conclusion: The authors concluded that the increased lung cancer risk in short-term workers was most likely due to risk acquired elsewhere, such as prior employment, or to differences in smoking or other behavior. They also concluded that including short-term workers magnified rather than diluted the apparent exposure–outcome relation.
• Limitations the authors state:
  • Smoking information was limited and anecdotal. The authors said more data collection would be needed to compare smoking habits.
  • Little information was available on exposures after workers left the plant.
  • The 36 women were not included in the statistical analysis because of small numbers.
  • Ambiguous prior jobs (for example carpentry, electrical work, military) were classed as 'no prior risk'. The authors said this would bias against finding a difference between groups.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Talc, Confounding.

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• Long-term follow-up mortality study of petroleum refinery and chemical plant employees — S.P. Tsai, E.L. Gilstrap, et al. (1996)
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