Evaluation of environmental carcinogens for cancer in man

Our plain-English summary of Evaluation of environmental carcinogens for cancer in man, by A.L. Brown (Oncology, 1976).

The study

• Author: A.L. Brown
• Journal: Oncology
• Published: 1976;33(2):58-60
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004824).

Abstract

The problem of the presence of carcinogens in the environment has become of considerable concern to the public, as it has been to the biomedical community for some time. The burden of identifying carcinogenic agents and determining threshold levels, if they exist, falls upon the scientific community. Particular care must be exercised in the design, conduct and analysis of experiments directed toward the identification of carcinogens. The data generated from such tests provides the basis for regulatory decisions by governmental authorities. The advice provided by scientists must be based on sound data. There have been instances, however, and there will be others, in which biological variability and the limits of sensitivity of our tests will give equivocal results. It is the duty of scientists to bring such uncertainties to the attention of the public while working towards the development of more sensitive and precise techniques.

In plain English

This 1976 article is a commentary, not a research study. It reports no new data. The author, from the Mayo Clinic, used recent U.S. experiences with cyclamate and asbestos as examples of how hard it is to judge environmental carcinogens. The author limited "environment" to air, drinking water and food. For cyclamate, the author's committee concluded that the evidence did not establish that it caused cancer. The author noted that an experiment designed to settle the question required nearly 52,000 animals and very likely would still have left an unreasonable degree of uncertainty. For asbestos, the author described asbestiform fibers found in the drinking water of Duluth, Minnesota. It was asserted that the fibers came from an iron ore processing mill dumping 67,000 tons of rocky wastes into Lake Superior each day. The author wrote that only minimal data existed on swallowing asbestos. The mining company had been required to halt the dumping because asbestos is a known human carcinogen, not because of direct evidence of a gastrointestinal effect. The author concluded that the advice scientists give must rest on sound science.

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: Commentary/lecture (opinion article) with no original data; uses cyclamate and asbestos as examples
• Who was studied: No study population. As an example, the author discussed the inhabitants of Duluth, Minnesota, a city of 100,000 people on Lake Superior, whose drinking water contained asbestiform fibers.
• Exposure: Environmental exposures, defined as air, drinking water and food. The asbestos example concerned asbestiform fibers in Duluth drinking water, which were asserted to come from 67,000 tons a day of rocky wastes dumped by an iron ore processing mill. No specific fiber type is named. Cyclamate is the other example.
• Main results:
  • The author stated that, at the time, only a minimal amount of data was available on the effect of ingesting asbestos.
  • According to the author, the mining company had been required to halt its dumping of wastes into the Lake. This requirement was based on asbestos being a known human carcinogen, not on direct evidence of a gastrointestinal effect.
  • The author's committee concluded that the evidence did not establish that cyclamate causes cancer.
  • A National Cancer Institute protocol designed to settle the cyclamate question required nearly 52,000 animals. In the author's view, it very likely would still have left an unreasonable degree of uncertainty.
  • The author noted that distinguished scientists had drawn opposite conclusions from the same information on both cyclamate and asbestos.
• The authors' conclusion: The author concluded that the inputs to regulatory decisions are only as good as the science behind them. The author added that scientists must be willing to tell the public when they are uncertain.

Topics

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

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