Concentration and size of asbestos in water supplies

Our plain-English summary of Concentration and size of asbestos in water supplies, by J.R. Millette, P.J. Clark, M.F. Pansing, et al (Environmental Health Perspectives, 1980).

The study

• Authors: J.R. Millette, P.J. Clark, M.F. Pansing, J.D. Twyman
• Journal: Environmental Health Perspectives
• Published: 1980;34:13-25
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A review of the results of over 1500 asbestos analyses from U.S. water supplies suggests that the majority of water consumers are not exposed to asbestos concentrations in their drinking water over 1 x 10(6) fibers per liter. There are, however, some populations that are exposed to waterborne asbestos concentrations over 10 x 10(6) fibers per liter caused by natural erosion, mine processing wastes, waste pile erosion, corrosion of asbestos cement pipe, or disintegration of asbestos tile roofs running into cisterns. The distribution of fiber sizes in the water is dependent on the source of the fibers. The average length of chrysotile fibers found in an asbestos cement distribution system was 4 micrometers, while the average fiber length of chrysotile fibers contributed to a water supply by natural erosion was 1 micrometer.

In plain English

This article reviewed results of over 1500 water samples from U.S. water supplies that had been analyzed for asbestos by electron microscopy, with data reported by 15 laboratories. It measured fiber concentrations and sizes, not health effects. Across 406 cities in 47 states, Puerto Rico and the District of Columbia, the highest reported concentration was below detectable limits in 117 cities (28.8%), between 1 and 10 million fibers per liter in 33 (8.1%), and above 10 million in 40 (9.9%). Chrysotile was the most common fiber found, and amphibole fibers were found in Lake Superior. The article linked higher levels to natural erosion, mine processing wastes, waste pile erosion, corroded asbestos cement pipe, and asbestos tile roofs draining into cisterns. Average chrysotile fiber length was 4.3 micrometers in five asbestos cement pipe systems, compared with 0.8 and 1.3 micrometers in two reservoirs with natural erosion. The authors concluded that most U.S. water consumers were not exposed to constant concentrations above 1 million fibers per liter, but some areas had 1 to 100 million. They noted that differing laboratory methods led to disagreements over values.

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: Review and compilation of existing electron-microscopy analyses of asbestos in U.S. drinking water, plus fiber-size measurements; no health outcomes studied
• Who was studied: Drinking water supplies of 406 cities in 47 U.S. states, Puerto Rico and the District of Columbia (over 1500 samples, data from 15 laboratories)
• Exposure: Asbestos fibers in drinking water, mainly chrysotile. Amphiboles were also identified: cummingtonite-grunerite series fibers in Lake Superior, crocidolite alongside chrysotile in some water carried through asbestos cement pipe, and tremolite-actinolite in some Pacific Northwest supplies.
• Main results:
  • Highest reported asbestos concentration in each of 406 cities: below detectable limits in 117 (28.8%); not significant (under 0.5 million fibers per liter) in 103 (25.4%); under 1 million in 113 (27.8%); 1 to 10 million in 33 (8.1%); over 10 million in 40 (9.9%)
  • Some populations were exposed to waterborne asbestos concentrations over 10 million fibers per liter. The article attributed these to natural erosion, mine processing wastes, waste pile erosion, corrosion of asbestos cement pipe, or asbestos tile roofs draining into cisterns.
  • Chrysotile in five asbestos cement pipe systems (SC, PA, FL): 1440 fibers measured, average length 4.3 micrometers, average width 0.044 micrometers, longest fiber found 80 micrometers
  • Chrysotile in reservoirs with natural erosion: in Washington, 289 fibers measured, average length 0.8 micrometers, longest 3 micrometers; in California, 644 fibers measured, average length 1.3 micrometers, longest 10 micrometers
  • In a cistern with an asbestos tile roof (Virgin Islands), 342 chrysotile fibers were measured, with an average length of 2.3 micrometers. In Lake Superior (Minnesota), 468 amphibole fibers were measured, with an average length of 1.5 micrometers.
• The authors' conclusion: The authors concluded that most U.S. water consumers were not exposed to constant concentrations above 1 million fibers per liter, though people in some areas were exposed to 1 to 100 million. They also concluded that fibers from natural erosion were generally shorter than fibers from asbestos cement pipe.
• Limitations the authors state:
  • The data came from 15 laboratories, some using different sample preparation methods, so there were disagreements over actual values
  • Methods for sizing asbestos fibers in environmental samples were not standardized
  • Different sample preparation methods can give different size results for the same sample
  • Apart from Lake Superior, it had not been shown conclusively that industrially discharged asbestos fibers reach public drinking water

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Chrysotile, Fiber Length.

Related studies

• Asbestiform amphibole minerals: detection and measurement of high concentrations in municipal water supplies — P.M. Cook, G.E. Glass, et al. (1974)
• Asbestos in water supplies of the United States — J.R. Millette, P.J. Clark, et al. (1983)
• Asbestos in public water supplies: discussion of future problems — J.P. Hills (1979)
• Analysis of amphibole asbestiform fibers in municipal water supplies — W.J. Nicholson (1974)
• Effect of population density on the results of the study of water supplies in five California counties — P.M. Conforti (1983)
• Asbestos in drinking water and cancer — K.D. MacRae (1988)

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