Known occupational carcinogens and their significance

Our plain-English summary of Known occupational carcinogens and their significance, by P. Ernst, G. Thériault (Canadian Medical Association Journal, 1984).

The study

• Authors: P. Ernst, G. Thériault
• Journal: Canadian Medical Association Journal
• Published: 1984;130(7):863-7
• Type of article: Review
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

Although rates of occupational cancer can be excessive in certain industries, less than 5% of all cancers seem attributable to exposure to carcinogens in the workplace. For example, workers in hard-rock mining and the woodworking industries are at increased risk; cigarette smoking has a synergistic effect. There is conclusive evidence of carcinogenicity for fewer than 20 substances, including asbestos, arsenic, chromium, nickel, cadmium, radon, several aromatic hydrocarbons and certain herbicides. Most of the hundreds of organic compounds known to be mutagenic in in-vitro tests have not been shown to be carcinogenic in epidemiologic studies. Both laboratory and epidemiologic approaches, however, can identify probable causes of cancer and permit the application of effective preventive measures. In addition, it is still possible for the alert individual clinician to make the initial discovery of an occupational hazard.

In plain English

This 1984 article was a review, not a new study: the authors gave a brief overview of substances and occupations linked to cancer in workers. They wrote that fewer than 20 substances had been shown in epidemiologic studies to be clearly carcinogenic in humans. Summarizing earlier research on asbestos, they reported three things. Increased lung cancer in exposed people had been confirmed repeatedly since 1955, with a recognized synergism between asbestos and cigarette smoke. Asbestos, especially crocidolite, was linked to pleural and peritoneal mesotheliomas. Other studies suggested increases in esophageal, gastric and colorectal cancer. They noted experimental evidence that any fibre with dimensions resembling asbestos tends to become carcinogenic. Citing Doll and Peto, they reported that about 4% of all cancers in the United States were attributed to occupational causes. The authors concluded that although probably less than 5% of cancers can be attributed to occupation, the social impact of workplace-related cancers is disproportionately great.

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: Narrative review (overview of published evidence on occupational carcinogens); no new data collected
• Who was studied: No study population; the article reviewed published epidemiologic and experimental literature on substances and occupations associated with cancer
• Exposure: Occupational carcinogens generally, including asbestos (crocidolite named specifically), arsenic, chromium, nickel, cadmium, radon, aromatic amines, vinyl chloride, soots, tars and oils, certain herbicides, and jobs such as hard-rock mining and woodworking
• Main results:
  • Citing earlier studies, the authors wrote that increased lung cancer in people exposed to asbestos had been confirmed repeatedly since 1955
  • A synergism between the cancer-causing effects of cigarette smoke and asbestos was described as recognized (from cited literature)
  • Cited evidence linked asbestos, especially crocidolite, to pleural and peritoneal mesotheliomas
  • Other studies cited by the authors suggested asbestos exposure leads to increased incidence of esophageal, gastric and colorectal cancer
  • The authors noted experimental evidence suggesting that any kind of fibre tends to become carcinogenic when its dimensions resemble those of asbestos, a possible hazard of synthetic substitutes
  • Asbestos is not mutagenic in in-vitro assays, and the mechanism by which it causes cancer in humans was described as not explained
  • Asbestos, arsenic, chromium and nickel are often found as contaminants in mines, so radiation may not be the only carcinogenic hazard there
  • Citing Doll and Peto, about 4% of all cancers in the United States were attributed to occupational causes
  • A much higher estimate (23% to 38% of cancer mortality) from a report commissioned by the US Occupational Safety and Health Administration was described as severely criticized, partly for attributing an apparently excessive proportion of cancers to casual employment in the asbestos industry
  • At most 15% of lung cancer and 30% of bladder cancer could be attributed to occupation, according to cited work
• The authors' conclusion: The authors concluded that although probably less than 5% of cancers can be attributed to occupation, the social impact of workplace-related malignant diseases is disproportionately great. They also wrote that individual physicians have a major role in detecting occupational hazards, and that stopping cigarette smoking among workers in high-risk occupations is the most important preventive measure they could recommend.

Topics

Medical terms in this study, explained in our Lexicon: Synergistic Effect, Carcinogenic, Discovery.

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