Asbestos-Cement Pipe Should Not Be Used For Drinking Water Supplies

Our plain-English summary of Asbestos-Cement Pipe Should Not Be Used For Drinking Water Supplies, by B. Castleman, D. Blum (1975).

The study

• Authors: B. Castleman, D. Blum
• Published: Maryland Public Interest Research Group. April 1975.
• Type of article: Report
• 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 1975 Maryland Public Interest Research Group report was an advocacy paper that drew on other sources rather than reporting a new study. It cited Johns-Manville tests in which electron microscopy found asbestos fibers added to water after it passed through only thirty feet of asbestos-cement (A-C) pipe. It also cited a Cast Iron Pipe Research Association analysis of two municipal systems showing average fiber increases of 0.28 micrograms per gallon at Malvern and 0.015 at Glendale, close to a 20-fold difference linked to more aggressive water. It described an unpublished rat experiment by Dr. Pontrefact in which six of seven rats fed 1% chrysotile in corn oil developed malignant tumors, while one of eight control rats developed a tumor; the letter said none of the test animals' tumors were gastrointestinal. It cited a Johns-Manville study finding lung cancer over six times the expected rate among retired pipe-division workers. The authors acknowledged that proving harm from drinking water is probably impossible, partly because colon cancer is common. They concluded that A-C pipe should not be used for drinking water supplies.

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: Advocacy report / position paper by a student public interest group, reviewing evidence from industry tests, animal studies, conference proceedings and correspondence; no new study was carried out
• Who was studied: No study population; the report concerns the U.S. public drinking water carried in asbestos-cement pipe, and workers who make, drill and tap the pipe
• Exposure: Asbestos fibers released into drinking water from asbestos-cement pipe, which the report says is made with chrysotile and crocidolite; also airborne asbestos for workers who drill, tap or manufacture the pipe
• Main results:
  • Cited Johns-Manville tests: an electron microscope study showed asbestos fibers were added to water that had passed through only thirty feet of asbestos-cement pipe
  • Cited Cast Iron Pipe Research Association analysis (Appendix B): at Malvern, water with a Ryznar index of 9.0 showed an average fiber level increase of 0.28 micrograms per gallon. At Glendale, water with an index of 8.1 showed an average increase of 0.015 micrograms per gallon, described as close to a 20-fold increase in fiber pickup.
  • Cited unpublished rat feeding experiment by Dr. Pontrefact, in which rats were fed one per cent chrysotile asbestos in corn oil: six of seven test rats developed malignant tumors, while one of eight control rats developed a tumor
  • In the same rat experiment, according to Dr. Pontrefact's letter, none of the tumors in the test animals were in the gastrointestinal tract
  • Cited Johns-Manville study of retired pipe-division workers: lung cancer incidence was over six times that expected from United States mortality statistics
• The authors' conclusion: The authors concluded that asbestos-cement pipe should not be used for drinking water supplies. They argued that it may present a health hazard to the public and exposes installation, repair and manufacturing workers to asbestos, and that substitutes are available.
• Limitations the authors state:
  • The authors stated it is probably impossible to prove whether asbestos fibers are safe or deadly in the amounts and forms found in drinking water
  • The authors stated that differences between regions other than pipe type tend to confound comparisons of water systems
  • The authors stated that because colon cancer is relatively common, an association with asbestos-cement pipe is difficult or impossible to infer

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement Pipe, Johns-Manville, Asbestos-Cement, Chrysotile, Lung Cancer, Colorectal Cancer.

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