A case-control study of renal cancer mortality at a Texas chemical plant

Our plain-English summary of A case-control study of renal cancer mortality at a Texas chemical plant, by G.G. Bond, R.J. Shellenberger, G.H. Flores, et al (American Journal of Industrial Medicine, 1985).

The study

• Authors: G.G. Bond, R.J. Shellenberger, G.H. Flores, R.R. Cook, W.A. Fishbeck
• Journal: American Journal of Industrial Medicine
• Published: 1985;7(2):123-39
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

An in-plant case-control study of 26 renal cancer deaths was conducted to determine whether an occupational exposure may be related to an apparent increase in mortality from this disease observed among a sample of employees at a multiple process chemical production facility. None was found that explained the excess. Elevated odds ratios were identified for employment in the cell maintenance area of chlorine production and with those presumptive exposures considered to occur in this job, asbestos and caustic, but not chlorine. While an association between renal cancer and asbestos has been previously reported, an association with caustic, per se, is not consistent with prior observations made by others. Diminished risk estimates were observed for employment in magnesium production and for exposures in this process to sulfur dioxide and heat. Both the increased and decreased risks, while statistically significant, are based on small numbers of exposed subjects and may be spurious owing to the problem of multiple comparisons.

In plain English

This was a case-control study at the Dow Chemical Texas Division chemical plant. It followed an earlier study of a 5% random sample of employees that suggested more deaths from kidney (renal) cancer than expected. The authors compared the work histories of 26 former employees, all white men, who died of renal cancer between 1958 and 1980 with two matched control groups from the sample: 92 deceased men without cancer and 98 men chosen regardless of whether they were alive. Industrial hygienists, who did not know who was a case, assigned each man's likely exposures from his job records. Work in chlorine production was linked to higher odds of renal cancer. All five cases who worked there had worked in cell maintenance. Presumed exposures in that job to asbestos and caustic were also linked to higher odds, but chlorine was not. Seven cases were judged possibly exposed to asbestos. Work in magnesium production was linked to lower odds. The authors concluded that these findings did not explain the excess and might be due to chance, because they rested on small numbers and many comparisons.

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: In-plant case-control study of deaths, with two matched control groups. The analysis used 90% confidence limits.
• Who was studied: 26 former employees of Dow Chemical, Texas Division, who died of primary renal cancer according to the death certificate. Deaths occurred over 1958-1980, and age at death ranged from 43 to 79 years. Cases were found from company death benefit records and by matching state and cancer-center death files for adult white males in five surrounding counties. Controls came from a 5% random sample of white male employees: 92 in group A (deceased, without cancer) and 98 in group B (living or deceased).
• Exposure: Work areas, job categories, and 64 chemical and physical agents, presumptively assigned by on-site industrial hygienists from each man's work history. Asbestos exposure was assigned mainly to chlorine cell maintenance, an entry-level job that involved preparing an asbestos slurry in a caustic or water solution into which chlorine cells were dipped. The fiber type is not stated.
• Main results:
  • Ever working in the chlorine production area: odds ratio 3.80 (90% confidence limits 1.32-10.93) compared with control group A, based on 5 cases and 5 controls. Compared with group B the odds ratio was 2.34 (0.89-6.12), which was not statistically significant.
  • Working in chlorine production for more than 1 year was linked to significantly higher odds compared with both control groups. Table VI gives an odds ratio of 5.21 (90% CI 1.77-15.68) against group A and 6.00 against group B.
  • All five cases who worked in chlorine production had worked in chlorine cell maintenance, for periods from 1 week to 23 years. The time from first work in that area to death ranged from 22 to 35 years.
  • Presumed asbestos exposure: 7 cases were judged potentially exposed. Five of them worked in chlorine cell maintenance, one in general maintenance and one in the carpenter shop. In the scanned Table VII, the odds ratio for asbestos was 2.98 (90% CI 1.24-7.13; 9 exposed controls) against group A and 2.46 (1.05-5.78; 12 exposed controls) against group B. For caustic (NaOH), also 7 exposed cases, it was 2.91 (1.21-7.00) against group A and 2.46 (1.05-5.78) against group B. The authors stated that these raised estimates reflect the same risk found for employment in cell maintenance.
  • Presumed exposure to chlorine gas was not linked to increased risk. In Table VII the odds ratio was 1.01 against group A and 0.99 against group B, based on 14 exposed cases.
  • Work in magnesium production was linked to significantly lower odds compared with both control groups. In Table V, 4 cases had worked there, against 40 controls in group A (odds ratio 0.29, 90% CI 0.12-0.68) and 42 in group B (odds ratio 0.25). Sulfur dioxide and heat, exposures linked to that work, also showed significantly lower odds.
  • The authors reported that asbestos exposure in the cell maintenance job had been minor compared with that of asbestos insulators at the Texas Division. No renal cancer deaths had yet been observed among those insulators.
• The authors' conclusion: The authors concluded that the study found associations with work in chlorine cell maintenance and with the presumed exposures in that job (asbestos and caustic, but not chlorine). They found a decreased risk for magnesium production. They stated that the apparent excess of renal cancer deaths in the employee sample cannot be readily explained by these findings, and that both the raised and lowered risks rest on small numbers and may be spurious because of multiple comparisons. They added that if the cell maintenance association is causal, the study cannot identify which material is responsible.
• Limitations the authors state:
  • There was no prior reason to expect these associations. Because many comparisons were made, some significant findings were expected by chance alone.
  • Possible selection bias. Cases and controls were found by different methods, and the cases do not include all renal cancer deaths among former employees; the search was more likely to find men with longer service.
  • Disease information came only from death certificates.
  • Exposures may have been misclassified. Employees moved within the plants without records, possible exposures were varied, and past industrial hygiene survey data were scarce.
  • Few men were exposed to most agents. This limited the statistical power, and dose-response analysis was not possible.
  • Information on cigarette smoking was scarce.

Topics

Medical terms in this study, explained in our Lexicon: Case-Control Study, Occupational Exposure, Odds Ratio.

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• Asbestos and renal adenocarcinoma: a case-control study — M. Maclure (1987)
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