Workers exposed to vinyl chloride

Our plain-English summary of Workers exposed to vinyl chloride, by R J Waxweiler, W Stringer, J K Wagoner, et al (1975).

The study

• Authors: R J Waxweiler, W Stringer, J K Wagoner, J Jones, H Falk, C Carter
• Published: Annals of the New York Academy of Sciences, pp. 40-48 (pages 41-43 shown) (1975)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This article reported a study of vinyl chloride, not asbestos. Researchers from the National Institute for Occupational Safety and Health studied deaths among workers with at least five years in vinyl chloride jobs at four U.S. vinyl chloride polymerization plants. They counted deaths from ten years after first exposure through 1973, comparing them with U.S. white male death rates. There were 136 deaths against 126.3 expected. Cancer deaths numbered 35 against 23.5 expected, an excess described as statistically significant. Excesses were reported for cancers of the brain and central nervous system, respiratory system, biliary system and liver combined (7 observed against 0.6 expected), and lymphatic and blood-forming system. The excesses grew among workers followed 15 or more years after first exposure. Pathologists confirmed 14 liver and biliary cancers among workers from the four plants. Eleven were liver angiosarcoma, and all eleven people had worked as reactor cleaners. Of ten brain cancers, nine were glioblastoma multiforme, and no tissue diagnosis was available for the tenth. The authors concluded that the evidence pointed to vinyl chloride as the cause.

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 of mortality, with industrial hygiene surveys and a separate histopathology (tumor tissue review) study
• Who was studied: Workers at four U.S. vinyl chloride polymerization plants. The plants employed 250, 75, 250 and 250 polymerization workers in 1974 and had been polymerizing vinyl chloride for 28, 20, 24 and 32 years. The cohort was limited to people with at least five years of employment in vinyl chloride-exposed departments or jobs and at least ten years since first such employment. They were followed to December 31, 1973. The exact cohort size is unreadable in the scanned text.
• Exposure: Vinyl chloride (VC), through work in VC monomer production, VC polymerization, polyvinyl chloride (PVC) compounding, and maintenance
• Main results:
  • Whole cohort: 136 deaths observed against 126.3 expected from U.S. white male rates
  • Whole cohort: deaths from all malignant neoplasms numbered 35 observed against 23.5 expected
  • The excess of all malignant neoplasms was described as statistically significant. The printed p-value is damaged by scanning.
  • By site, excess cancer deaths were found for four organ systems: brain and central nervous system, respiratory system, hepatic system, and lymphatic and hematopoietic system
  • Hepatic system cancer, which the tables label as the combined biliary and liver cancer category: 7 observed against 0.6 expected
  • Moving from workers with 10 or more years since first exposure to those with 15 or more years, the standardized mortality ratio rose from 329 to 498 for brain and central nervous system cancer. It rose from 156 to 193 for respiratory system cancer and from 159 to 176 for lymphatic and hematopoietic system cancer.
  • Among workers with 15 or more years since first exposure, the authors found no evidence that cancer risk in the three other plants differed from that in Plant 4
  • Of 14 histologically confirmed biliary and liver cancer cases among workers from the four plants, eleven were angiosarcoma of the liver
  • All eleven liver angiosarcoma cases had at some time worked as reactor cleaners
  • One worker (Case 4) had a known vinyl chloride exposure only sometime during 1950-1954. That worker died of hepatic angiosarcoma at age 41, seventeen years after first exposure.
  • Of ten brain cancer cases, nine were classified histologically as glioblastoma multiforme, and no histologic diagnosis was available for the tenth. Of the nine, six had worked in vinyl chloride polymerization areas and three in lower-exposure areas.
  • Of 14 primary lung cancers among cohort members, tumor specimens were available for eight. Five were large-cell undifferentiated and three were adenocarcinoma, with no squamous-cell or small-cell carcinoma.
• The authors' conclusion: The authors concluded that the epidemiological and histopathological evidence pointed to vinyl chloride as the causal agent of the excess cancer risk. They also stated that the findings support conducting animal bioassays before new chemicals are introduced into industrial or community environments.
• Limitations the authors state:
  • The number of deaths in the three plants other than Plant 4 was small
  • Workers whose vital status could not be determined were assumed to be alive, so as not to overestimate the risk

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