Retrospective cohort study of a microelectronics and business machine facility

Our plain-English summary of Retrospective cohort study of a microelectronics and business machine facility, by S.R. Silver, L.E. Pinkerton, D.A. Fleming, et al (American Journal of Industrial Medicine, 2014).

The study

• Authors: S.R. Silver, L.E. Pinkerton, D.A. Fleming, J.H. Jones, S. Allee, L. Luo, S.J. Bertke
• Journal: American Journal of Industrial Medicine
• Published: 2014;57(4):412-24
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: We examined health outcomes among 34,494 workers employed at a microelectronics and business machine facility 1969-2001.

Methods: Standardized mortality ratio (SMR) and standardized incidence ratios were used to evaluate health outcomes in the cohort and Cox regression modeling to evaluate relations between scores for occupational exposures and outcomes of a priori interest.

Results: Just over 17% of the cohort (5,966 people) had died through 2009. All cause, all cancer, and many cause-specific SMRs showed statistically significant deficits. In hourly males, SMRs were significantly elevated for non-Hodgkin's lymphoma and rectal cancer. Salaried males had excess testicular cancer incidence. Pleural cancer and mesothelioma excesses were observed in workers hired before 1969, but no available records substantiate use of asbestos in manufacturing processes. A positive, statistically significant relation was observed between exposure scores for tetrachloroethylene and nervous system diseases.

Conclusions: Few significant exposure-outcome relations were observed, but risks from occupational exposures cannot be ruled out due to data limitations and the relative youth of the cohort.

© 2013 Wiley Periodicals, Inc.

In plain English

This retrospective cohort study followed 34,494 people who worked at least 91 days between 1969 and 2001 at a microelectronics and business machine facility in upstate New York. By the end of 2009, 5,966 (17.3%) had died. Overall death rates were below US rates. Hourly men had significantly more deaths than expected from non-Hodgkin's lymphoma and rectal cancer. Salaried men had more testicular cancer diagnoses than expected. This was of borderline significance counting workers employed at least 91 days, and significant counting those employed at least 3 years. Hourly men had 7 mesothelioma deaths, about twice the expected number but not statistically significant. Salaried men had 3 pleural cancer deaths, about five times expected and statistically significant. The authors thought these likely reflected the same disease. All these cases were in workers hired before 1969. The authors found no site records suggesting asbestos use in manufacturing and listed other possible sources. No asbestosis deaths were seen. Tetrachloroethylene exposure scores were associated with deaths from nervous system disease. The authors concluded that occupational risks could not be ruled out because of data limitations and the cohort's youth.

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 cohort study. It compared deaths and testicular cancer cases with US and New York State rates (standardized mortality and incidence ratios). It also used internal regression (Cox) analyses of estimated chemical exposure scores and of time worked in manufacturing buildings.
• Who was studied: 34,494 direct employees who worked at least 91 days between January 1, 1969 and December 31, 2001 at a microelectronics and business machine facility in a town in upstate New York. Vital status was followed through December 31, 2009, and 5,966 (17.3%) had died. Testicular cancer cases were identified through the New York and Pennsylvania cancer registries.
• Exposure: Estimated cumulative potential exposure scores were built for lead, methylene chloride, tetrachloroethylene (PCE) and trichloroethylene (TCE). Scores were also built for chemical classes: acids and bases, chlorinated hydrocarbons, and other hydrocarbons. The study also looked at time worked in seven major manufacturing buildings. Asbestos was not one of the exposures assessed, and the authors found no site information that asbestos was used in manufacturing.
• Main results:
  • For the entire workforce, deaths from all causes (SMR 0.67, 95% CI 0.65 to 0.69) and from all cancers (SMR 0.74, 95% CI 0.71 to 0.77) were significantly below expected.
  • Among hourly males, deaths were significantly elevated for non-Hodgkin's lymphoma (65 deaths, SMR 1.49, 95% CI 1.15 to 1.89) and rectal cancer (36 deaths, SMR 1.71, 95% CI 1.20 to 2.36).
  • Among hourly males there were 7 mesothelioma deaths (SMR 2.18, 95% CI 0.88 to 4.50; not statistically significant). Among salaried males there were 3 deaths from malignant neoplasm of the pleura (SMR 5.42, 95% CI 1.12 to 15.8). The authors stated these likely reflect the same disease, coded differently over time.
  • Among hourly males, deaths from malignant neoplasms of the peritoneum and other and unspecified digestive organs were elevated but not significantly (6 deaths, SMR 1.57, 95% CI 0.58 to 3.43). The authors said this category might include some asbestos-related deaths.
  • The work histories of the 12 workers who died from these causes showed nothing in common except that all were hired by the company before 1969 (nine before 1960).
  • No deaths from silicosis, asbestosis, or other pneumoconioses were seen among hourly or salaried males.
  • Among salaried males, testicular cancer incidence (using New York State rates) was elevated with borderline significance under a 91-day employment minimum (SIR 1.82, 95% CI 1.00 to 3.06, 14 cases). It was significantly elevated under a 3-year minimum (SIR 2.08, 95% CI 1.08 to 3.64). Among hourly males it was near expectation (SIR 0.97, 95% CI 0.59 to 1.52, 19 cases).
  • In internal analyses, the cumulative PCE exposure score was positively and significantly related to deaths from non-malignant diseases of the nervous system (171 cases). The hazard ratio at 5 modified exposure years was 1.31 (95% CI 1.01 to 1.69).
• The authors' conclusion: The authors concluded that, taken together, the results do not suggest a strong role for occupational exposures. They added that occupational risks cannot be ruled out because of substantial data limitations and the relative youth of the cohort. On mesothelioma and pleural cancer, they stated that no site industrial hygiene or process information suggests asbestos was part of manufacturing at the site.
• Limitations the authors state:
  • Other possible sources of asbestos exposure could not be evaluated from the available data. These include non-occupational exposures, exposures at the facility before the study period, nearby repair or renovation work, and exposures at other worksites.
  • Exposures from work before 1969 or at the company's other facilities were not accounted for.
  • Industrial hygiene data were very sparse before 1974, when exposures were likely highest. Work history records contained much incomplete and contradictory information.
  • The department-based exposure method could cause exposure misclassification and a failure to detect exposure-related health effects.
  • The large number of associations evaluated could lead to statistically significant findings by chance.
  • For less common outcomes, numbers were too small for statistically precise estimates.
  • The study lacked data to directly control for lifestyle or environmental factors. Paycode was used only as a partial adjustment.
  • Testicular cancer cases outside New York and Pennsylvania were likely missed, particularly among salaried workers, who were more likely to move away.

Topics

Medical terms in this study, explained in our Lexicon: Cohort Study, standardized mortality ratio (SMR), Standardized Incidence Ratio (SIR), Occupational Exposure, Mesothelioma.

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