Gastrointestinal cancer mortality of workers in occupations with high asbestos exposures

Our plain-English summary of Gastrointestinal cancer mortality of workers in occupations with high asbestos exposures, by S.K. Kang, C.A. Burnett, E. Freund, et al (American Journal of Industrial Medicine, 1997).

The study

• Authors: S.K. Kang, C.A. Burnett, E. Freund, J. Walker, N. Lalich, J. Sestito
• Journal: American Journal of Industrial Medicine
• Published: 1997;31(6):713-8
• Cited by: 51 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos, which is a well-known risk factor for lung cancer and malignant mesothelioma, has also been suggested as a gastrointestinal (GI) carcinogen. This study was conducted to assess the relationship between high asbestos exposure occupations and the occurrence of G1 cancer. Death certificate data were analyzed from 4,943,566 decedents with information on occupation and industry from 28 states from 1979 through 1990. Elevated proportionate mortality ratios (PMRs) for mesothelioma were used to identify occupations potentially having many workers exposed to asbestos. All PMRs were age-adjusted and sex- and race-specific. The PMRs for GI cancers in white males were then calculated for these occupations after excluding mesothelioma, lung cancer, and non-malignant respiratory disease from all deaths. We identified 15,524 cases of GI cancer in the 12 occupations with elevated PMRs for mesothelioma. When these occupations were combined, the PMRs for esophageal, gastric, and colorectal cancer were significantly elevated at 108 (95% confidence interval = 107-110), 110 (106-113), and 109 (107-110), respectively. Esophageal cancer was elevated in sheet metal workers and mechanical workers. Gastric cancer was elevated in supervisors in production and managers. Colorectal cancer was elevated in mechanical and electrical and electronic engineers. However, high exposure occupations like insulation, construction painter supervisors, plumbers, furnace operators, and construction electricians showed no elevations of GI cancers. In conclusion, this death certificate study supports an association between asbestos exposure and some GI cancer, however the magnitude of this effect is very small.

In plain English

This death certificate study used 4,943,566 death certificates from 28 U.S. states, 1979 to 1990, to examine gastrointestinal (GI) cancer in jobs with heavy asbestos exposure. Rather than measuring exposure, the authors selected 12 occupations where white men had significantly raised proportions of deaths from malignant mesothelioma, including insulation workers, plumbers and managers. Deaths from mesothelioma, lung cancer, unidentified cancer and non-malignant respiratory disease were set aside. The 12 occupations combined had a proportionate mortality ratio (PMR) for GI cancer of 109 (95% confidence interval 107 to 110), from 15,524 GI cancer deaths. The PMRs were 108 (104 to 112) for esophageal, 110 (106 to 113) for gastric and 109 (107 to 110) for colorectal cancer. Insulation workers, the group with the highest mesothelioma ratio, did not show raised GI cancer: PMR 99 (68 to 140), from only 32 GI cancer deaths. The authors concluded the study supports an association between asbestos exposure and some GI cancer, but that the effect was very small. They noted possible errors in recorded occupations and no information on smoking, drinking, diet or socioeconomic status.

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: Death certificate study using proportionate mortality ratios (PMRs). Occupations were first chosen by their mesothelioma PMR, and their GI cancer PMRs were then calculated.
• Who was studied: 4,943,566 death certificates from 28 U.S. states, 1979 to 1990, from the National Occupational Mortality Surveillance (NOMS) system. The analysis was limited to white males. The 12 selected occupations together had 346,548 deaths.
• Exposure: Asbestos exposure was not measured. The usual occupation recorded on the death certificate was used, and occupations with significantly raised mesothelioma PMRs (pleural and peritoneal mesothelioma codes) were treated as likely to have many asbestos-exposed workers. No fiber types are specified.
• Main results:
  • Among white males there were 1,033 cases of malignant mesothelioma. Twelve occupations had statistically significant raised mesothelioma PMRs. Together they had 321 mesothelioma cases among 346,548 deaths, plus 170 asbestosis deaths.
  • Mesothelioma PMRs in the 12 occupations ranged from 3,667 (95% CI 2,174 to 5,796) for insulation workers to 140 (95% CI 112 to 172) for managers.
  • All 12 occupations combined (the Group, 15,524 GI cancer deaths) had an overall GI cancer PMR of 109 (95% CI 107 to 110). The nine occupations with mesothelioma PMRs over 200 (the Subgroup, 4,274 GI cancer deaths) had a GI cancer PMR of 108 (95% CI 105 to 111), as shown in Table II.
  • In the Group, Table III gives PMRs of 108 (95% CI 104 to 112) for esophageal cancer, 110 (95% CI 106 to 113) for gastric cancer and 109 (95% CI 107 to 110) for colorectal cancer. The results text prints the colorectal interval as 107 to 111.
  • In the Subgroup, PMRs were raised for esophageal cancer at 116 (95% CI 107 to 125) and colorectal cancer at 107 (95% CI 104 to 111). The gastric cancer PMR of 106 (95% CI 99 to 114) was not significantly raised.
  • Among individual occupations, GI cancer PMRs were significantly raised for mechanical engineers (128), electrical and electronic engineers (124), supervisors in production occupations (116), managers (112) and plant stationary engineers (112). The authors noted these occupations had relatively low mesothelioma PMRs.
  • Insulation workers had the highest mesothelioma PMR but did not show a raised GI cancer PMR: 99 (95% CI 68 to 140), based on 32 GI cancer deaths among 1,079 deaths (Table II). GI cancer was also not raised in construction painter supervisors, plumbers, sheet metal workers, furnace, kiln and oven operators, construction electricians and construction carpenters.
  • The esophageal cancer PMR was significantly raised in sheet metal workers, mechanical engineers and construction carpenters.
  • The gastric cancer PMR was significantly raised in supervisors in production occupations and in managers.
  • The colorectal cancer PMR was significantly raised in mechanical engineers, electrical and electronic engineers, supervisors in production occupations and managers. It was decreased in construction carpenters.
• The authors' conclusion: The authors concluded that this death certificate study supports an association between asbestos exposure and some GI cancer, but that the size of the effect is very small. They also said the lack of elevation in insulation workers makes a causal relationship questionable.
• Limitations the authors state:
  • Usual industry and occupation may be misclassified, because funeral directors collect this information from next of kin.
  • The PMR method may be biased. GI cancer PMRs in these occupations could be overestimated if these workers were less affected by diseases common in less healthy people.
  • Causes of death on death certificates may be misclassified, and ICD-9 has no specific code for malignant mesothelioma.
  • Death certificates give no information on diet, exercise, drinking, smoking or socioeconomic status, so these possible confounders could not be controlled.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Lung Cancer, Malignant Mesothelioma, Death Certificate, Mesothelioma, Colorectal Cancer, confidence interval, Esophageal Cancer.

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