Correlation of ZPP values and blood lead values in lead workers

Our plain-English summary of Correlation of ZPP values and blood lead values in lead workers, by Theodore W. Thoburn (1977).

The study

• Author: Theodore W. Thoburn
• Published: Letter to the Editor (journal name not shown on these pages); page 236; National Institute for Occupational Safety and Health (1977)
• Type of article: Letter
• 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

The citation's title belongs to a separate letter on zinc protoporphyrin and blood lead in lead workers, which reported its own data and is not about asbestos. This summary covers a second letter on the same pages, signed by P. Gross and a co-author at the Industrial Health Foundation in Pittsburgh. That letter was a commentary and reported no new data. The authors questioned whether rat experiments, in which asbestos, glass and other mineral fibers were implanted into the pleural or peritoneal cavity, could properly be applied to people. They argued that human experience disagreed with those experiments. They wrote that the rat studies gave similar mesothelioma rates for chrysotile and crocidolite, while crocidolite is recognized as the most dangerous type in people. They also wrote that no mesothelioma had been documented in Finland despite extensive anthophyllite exposure. They added that rats develop cancers when many insoluble solids are introduced under the skin or into body cavities, and that non-fibrous particles also cause cancers there, at a lower rate. The authors concluded that no reliance can be placed on extrapolating these rat results to humans.

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: Letter to the editor (opinion and commentary on other researchers' animal experiments); no new data
• Who was studied: No study population. The letter discussed published experiments by others in rats.
• Exposure: Mineral fibers implanted into the pleural or peritoneal cavity of rats in other researchers' experiments, including asbestos (chrysotile, crocidolite, amosite, anthophyllite) and fibrous glass. Non-fibrous insoluble particles such as glass powder and aluminum oxide were also discussed.
• Main results:
  • The authors cited rat experiments in which crocidolite injected intrapleurally gave a 61% incidence. They said chrysotile gave a similar rate at the same size dose. They argued that clinical experience strongly disagrees, because crocidolite is recognized as the most dangerous type of asbestos in people.
  • The authors wrote that, according to a cited report, only three chrysotile mine and mill workers among those who had died of various causes were found to have died of mesothelioma. The total number of deaths is unreadable in the scan.
  • The authors noted that rats develop cancers when many different kinds of insoluble solids are introduced under the skin or within their body cavities.
  • The authors wrote that non-fibrous insoluble particles, such as glass powder and aluminum oxide, placed in rats' body cavities also caused cancers, though at a lower rate. They argued that this method assigns cancer-causing potential to materials known not to cause cancer in people.
  • The authors argued that the rat fiber experiments fit both exceptions to extrapolation set out by a National Cancer Institute committee: the effect was physical rather than chemical, and the route of administration was grossly inappropriate to human exposure.
• The authors' conclusion: The authors concluded that the method used in the rat fiber experiments should be viewed with skepticism and that no reliance can be placed on extrapolating these results to humans.

Topics

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Peritoneal Cavity, Mesothelioma, Chrysotile, Crocidolite, Anthophyllite.

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