Impact of chemical exposure on cancer mortality in a French cohort of uranium processing workers

Our plain-English summary of Impact of chemical exposure on cancer mortality in a French cohort of uranium processing workers, by S. Zhivin, D. Laurier, S. Caër-Lorho, et al (American Journal of Industrial Medicine, 2013).

The study

• Authors: S. Zhivin, D. Laurier, S. Caër-Lorho, A. Acker, I. Guseva Canu
• Journal: American Journal of Industrial Medicine
• Published: 2013;56(11):1262-71
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Nuclear workers may be exposed to a variety of chemical hazards, in addition to radiation. We examined the effect of chemical exposures on cancer mortality among French uranium processing workers at the AREVA NC Pierrelatte facility.

Methods: A cohort of 2,897 uranium processing workers employed for at least 6 months was followed from 1968 through 2006. Exposure to uranium and potentially carcinogenic chemicals was assessed with a plant-specific job-exposure matrix. Mortality hazard ratios (HRs) for cancers of the lung, lymphohematopoietic system, kidney and bladder, brain and central nervous system (BCNS), and prostate were estimated for each specific chemical exposure, with Cox regression models stratified for sex and calendar period and adjusted for socioeconomic status. Additional adjustments enabled us to examine the effect of co-exposure to uranium and other chemicals.

Results: Exposure to aromatic solvents was associated with increased risk of BCNS malignancies after adjustment for other chemicals (HR=6.53, 95% CI=1.14-37.41; n=6) and for other chemicals and uranium (HR=7.26, 95% CI=0.90-58.19) in the annual exposure status model. Selected groups of lymphohematopoietic cancers were found associated with solvent exposure. Inconclusive results were found regarding chromium (VI) exposure, since only 2 workers died from lung cancer among 109 exposed.

Conclusion: Based on our pilot study, it seemed important to take into account chemical exposures in the analyses of cancer mortality among French uranium processing workers.

© 2013 Wiley Periodicals, Inc.

In plain English

This pilot cohort study followed 2,897 workers employed for at least 6 months at the AREVA NC Pierrelatte uranium processing plant in France, from 1968 through 2006. A plant-specific job-exposure matrix estimated each worker's exposure to uranium and chemicals. Asbestos was the most common chemical exposure (67% of workers); the type of asbestos fiber was not named. Of 460 deaths, 214 were from cancer. Lung cancer risk among asbestos-exposed workers did not differ from that of unexposed workers. Measured per step of a log-transformed cumulative asbestos exposure score lagged 10 years, the lung cancer hazard ratio was 1.04 (95% CI 0.94–1.16). A separate analysis of pleural cancer (malignant mesothelioma) found no significant association. Aromatic solvent exposure was associated with brain and central nervous system cancer deaths (HR 6.53, 95% CI 1.14–37.41), based on six deaths. After adjustment for uranium the estimate was no longer statistically significant. Chromium (VI) results rested on only two lung cancer deaths among 109 exposed workers. The authors called their findings preliminary because few cancer deaths had occurred so far. They said further follow-up for mesothelioma will be necessary.

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: Pilot retrospective cohort study with internal comparisons (Cox regression), using a plant-specific job-exposure matrix
• Who was studied: 2,897 workers (93.5% men) employed for at least 6 months at the AREVA NC Pierrelatte uranium processing facility, France, followed from January 1968 to December 2006 (mean 27.6 years); 460 deaths, 214 from cancer
• Exposure: Uranium compounds plus chemicals assessed by job-exposure matrix. The analysis focused on asbestos, trichloroethylene (TCE), aromatic solvents, hydrazine and other fuels, ceramic refractive fibers, welding fumes and chromium (VI) compounds. Asbestos exposure affected 67% of the cohort; asbestos fiber type is not specified.
• Main results:
  • Lung cancer risk among workers exposed to asbestos did not differ from that of unexposed workers (ever vs. never exposed, basic model: HR 0.77, 95% CI 0.38–1.56; 53 lung cancer deaths in the cohort)
  • Per step of the log-transformed cumulative asbestos exposure score, with a 10-year lag, the lung cancer HR was 1.04 (95% CI 0.94–1.16)
  • A separate analysis of pleural cancer mortality, using exposure scores lagged by 30 and 40 years, showed no significant association (data not shown)
  • Aromatic solvent exposure (ever vs. never) was associated with brain and central nervous system cancer mortality after adjustment for TCE (HR 6.53, 95% CI 1.14–37.41). After further adjustment for soluble uranium the HR was 7.26 (95% CI 0.90–58.19), not statistically significant. The finding was based on six deaths.
  • Chromium (VI) exposure was associated with lung cancer mortality (annual exposure status, fully adjusted HR 31, 95% CI 3.64–257.1), but this was based on only two lung cancer deaths among 109 exposed workers
  • Solvent exposure was associated with all leukemia except chronic lymphocytic leukemia (HR 14.39, 95% CI 2.04–101.40) and with non-Hodgkin's lymphoma among highly exposed workers (HR 4.38, 95% CI 1.01–18.97). For all lymphohematopoietic cancers combined, the 5-year lagged HR was 1.11 (95% CI 0.97–1.28), not significant.
  • No association was observed between TCE exposure and prostate cancer mortality. Risks of lung and of kidney and bladder cancer were elevated but not significantly so with hydrazine and other fuels.
• The authors' conclusion: The authors concluded that both chemical hazards and uranium compounds may have an impact on cancer mortality among French uranium processing workers, but that the results should be considered cautiously and confirmed by further follow-up.
• Limitations the authors state:
  • Only 14% of the cohort had died, and the number of cancer deaths (214) was small
  • Using several exposure definitions and models for each cancer may create a multiple-comparisons problem
  • Because of small numbers, all lymphatic and hematopoietic cancers were grouped in one category, although they may have different causes
  • Asbestos-related mesothelioma may have a latency of 40 years or more, so further follow-up for this disease is needed
  • The study used only mortality data, which may be less appropriate for prostate cancer, which is generally not fatal
  • The chromium (VI) dose-response data are too limited for any conclusion

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Hazard Ratio, Lung Cancer.

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