Employment characteristics and cause-specific mortality at automotive electronics manufacturing plants in Huntsville, Alabama

Our plain-English summary of Employment characteristics and cause-specific mortality at automotive electronics manufacturing plants in Huntsville, Alabama, by N. DeBono, D. Richardson, A. Keil, et al (American Journal of Industrial Medicine, 2019).

The study

• Authors: N. DeBono, D. Richardson, A. Keil, K. Kelly-Reif, W. Robinson, M. Troester, S. Marshall
• Journal: American Journal of Industrial Medicine
• Published: 2019;62(4):296-308
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: This study was carried out in response to worker concerns over their exposure to lead solder and chlorinated solvents at automotive electronics manufacturing plants in Huntsville, Alabama.

Methods: A study of 4396 United Autoworkers members ever-employed at the plants between 1972 and 1993 was conducted with mortality follow-up through 2016. Poisson regression was used to estimate mortality rate ratios (RR) according to employment characteristics, including calendar period of employment.

Results: Pre-1977 hires exhibited elevated adjusted rates of all-cause (RR, 1.29; 95% confidence interval [CI], 1.09-1.52), cardiovascular (RR, 1.38; 95% CI, 1.03-1.86), and digestive system (RR, 2.31; 95% CI, 1.04-5.10) disease mortality relative to the most recent hire group (1984-1993). Never- versus ever-employment in a skilled trade job was associated with elevated adjusted rates of all-cause, all-cancer, and cardiovascular disease mortality. Nervous system disorder mortality was greatest among 1977-1983 hires.

Conclusions: Elevated mortality among pre-1977 hires is consistent with worker concerns over greater exposure to hazards at the original plant building.

© 2019 Wiley Periodicals, Inc.

In plain English

This cohort study followed 4396 United Autoworkers members employed between 1972 and 1993 at Chrysler automotive electronics plants in Huntsville, Alabama. Workers there reported exposure to lead solder, chlorinated solvents, fiberglass dust and asbestos. Deaths were tracked through December 5, 2016, by which time 1134 workers had died. No exposure measurements were available, so the authors compared death rates by hire period, skilled trade status, administrative plant code (Plants 1 and 2 combined) and length of work. Workers hired before 1977, when only the original Plant 1 building operated, were compared with those hired 1984 to 1993. The early hires had higher death rates from all causes (rate ratio 1.29, 95% CI 1.09 to 1.52), cardiovascular disease (1.38, 1.03 to 1.86) and digestive system disease (2.31, 1.04 to 5.10). Workers never in a skilled trade had higher all-cause, cancer and cardiovascular death rates. The authors noted this may be confounded by socioeconomic status. Lung cancer showed no consistent pattern of association with employment characteristics. There was one asbestosis death and no mesothelioma deaths. The authors concluded that the elevated mortality among early hires appears consistent with worker concerns about the original plant building.

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: Retrospective occupational cohort mortality study using internal comparisons (Poisson regression rate ratios adjusted for age, sex and year of birth; Kaplan-Meier survival analysis)
• Who was studied: 4396 hourly and salaried United Autoworkers (UAW) members employed for any duration at Chrysler electronics plants in Huntsville, Alabama, from 1972 to 1993. The cohort was 58% female and 80% White. Vital status was followed through December 5, 2016, and 1134 (26%) had died.
• Exposure: Exposures reported by workers in interviews were fiberglass dust, conformal coatings, lead-based solder, chlorinated solvents (trichloroethylene and 1,1,1-trichloroethane) and asbestos, which was present at Plant 1. No quantitative exposure data were available. Duration of work, calendar period of hire, administrative plant code (Plants 1 and 2 combined; building-specific work history was unavailable) and skilled trade status were used as possible exposure contrasts.
• Main results:
  • Pre-1977 hires were compared with 1984-1993 hires. The pre-1977 hires had elevated adjusted death rates from all causes (RR 1.29; 95% CI 1.09-1.52), cardiovascular disease (RR 1.38; 95% CI 1.03-1.86) and digestive system disease (RR 2.31; 95% CI 1.04-5.10).
  • Pre-1977 hires also had an elevated adjusted cerebrovascular disease death rate compared with 1984-1993 hires (RR 1.58; 95% CI 0.75, 3.29). This confidence interval includes 1.
  • Workers never employed in a skilled trade were compared with those ever employed in one. The never-skilled workers had elevated adjusted death rates from all causes (RR 1.26; 95% CI 1.06, 1.51), all cancers (RR 1.43; 95% CI 1.01, 2.03) and cardiovascular disease (RR 1.52; 95% CI 1.10, 2.09).
  • Estimated survival after 33 years of follow-up was 75% for 1972-1976 hires, 80% for 1977-1983 hires and 81% for 1984-1993 hires. The log-rank test showed a significant difference between the groups (P less than 0.01).
  • In the overall cohort there was no evidence of an association between employment characteristics and trachea, bronchus and lung cancer death. The one exception was a possible elevation among 1977-1983 hires (RR 1.21; 95% CI 0.73, 1.99).
  • The cohort had one death due to asbestosis and no deaths due to mesothelioma.
  • Death from nervous system disorders was highest among 1977-1983 hires (RR 1.16; 95% CI 0.56, 2.42 versus 1984-1993 hires). The estimates were imprecise.
  • There were only 12 deaths from brain and nervous system cancer, so results were imprecise. For pre-1977 hires the RR was 4.52 (95% CI 0.83, 24.5).
  • Longer employment was associated with a lower adjusted all-cause death rate (more than 15 years versus 5 years or less: RR 0.83; 95% CI 0.71, 0.97).
• The authors' conclusion: The authors concluded that the elevated mortality among workers hired before 1977 appears consistent with worker concerns over adverse working conditions at the original plant building. They also said further study of non-fatal diseases is warranted.
• Limitations the authors state:
  • There was no individual exposure information. Job, department and building-specific work history was not available.
  • The study relied on death certificate causes of death, which are subject to misclassification and are insensitive for chronic diseases that are less often fatal.
  • The higher mortality among workers never in a skilled trade may be confounded by socioeconomic status.
  • Because salaried members were included, and likely had lower exposure, estimates may have been biased toward the null.
  • The cohort was small, so statistical power was limited for several causes of death of interest.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Auto mechanics and brake work.

Medical terms in this study, explained in our Lexicon: rate ratio, confidence interval.

Related studies

• Mortality among autoworkers manufacturing electronics in Huntsville, Alabama — N. DeBono, K. Kelly-Reif, et al. (2019)
• Mortality rates among employees potentially exposed to chrysotile asbestos at two automotive parts factories — M.M. Finkelstein (1989)
• Update of the Texaco mortality study 1947-93: Part II. Analyses of specific causes of death for white men employed in refining, research, and petrochemicals — B.J. Divine, C.M. Hartman, et al. (1999)
• Cause-specific mortality in relation to chrysotile-asbestos exposure in a Chinese cohort — S. Lin, X. Wang, et al. (2012)
• Mortality among maintenance employees potentially exposed to asbestos in a refinery and petrochemical plant — S.P. Tsai, L.C. Waddell, et al. (1996)
• 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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