Asbestiform amphibole minerals: detection and measurement of high concentrations in municipal water supplies

Our plain-English summary of Asbestiform amphibole minerals: detection and measurement of high concentrations in municipal water supplies, by P.M. Cook, G.E. Glass, J.H. Tucker (Science, 1974).

The study

• Authors: P.M. Cook, G.E. Glass, J.H. Tucker
• Journal: Science
• Published: 1974;185(4154):853-5
• Cited by: 61 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Ashestiform amphibole minerals, which have been demonstrated to be associated with human health problems, have been detected in substantial quantities in municipal water supplies taken from western Lake Superior Water. The total concentrationl of amphibole minerals in the Duluth, Minnesota, water supply, as measured by x-ray diffraction for daily samples of suspended solids averages 0.19 milligram per liter with large fluctuations due to seasonal and climatological effects on lake circulation. Electron microscopic examination of these water samples confirms the presence of asbestiform amphibole fibers. A conservatiue estimate of the fiber count for 1973 Duluth water supply samples is (1 to 30) x 10(6) amphibole fibers identifiable by electron diffraction per liter of water with a mass concentration of 1 to 30 micrograms per liter.

In plain English

This report measured amphibole minerals in municipal water supplies drawn from western Lake Superior. The authors tested Duluth, Minnesota, drinking water, mostly in daily 10-liter samples, from January 1973 to January 1974, using x-ray diffraction and electron microscopy. The main amphibole was cummingtonite-grunerite (whose commercial asbestiform type is amosite), with smaller amounts of tremolite-actinolite and hornblende. Some chrysotile fibers were also noted. During 1973, amphibole in Duluth water ranged from 0.03 to 0.80 milligrams per liter, with a mean of 0.19, and the level shifted with season, wind and rainfall. The authors estimated 1 to 30 million identified amphibole fibers per liter, with occasional peaks of up to about one billion. They said not all fibers present could be counted. Most fibers were shorter than 5 micrometers. Suspended-sediment samples collected by the Duluth water utility in 1939-1940 and 1949-1950 held only trace amounts of amphibole, while those from 1964-1965 held large amounts. The authors concluded that the source of this increase was taconite tailings discharged into the lake at Silver Bay since 1956. The study measured water, not illness.

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: Environmental measurement study of water and sediment samples, using x-ray diffraction and electron microscopy (no human health outcomes studied)
• Who was studied: Drinking water samples (10-liter) from the Duluth, Minnesota, water supply, January 1973 through January 1974, with daily sampling from 19 March 1973. Also water from other Lake Superior communities (Thunder Bay, Grand Marais, Silver Bay, Beaver Bay, Two Harbors, Cloquet), and historical suspended-sediment samples collected by the City of Duluth water utility
• Exposure: Asbestiform amphibole minerals in drinking water, mainly cummingtonite-grunerite (the asbestiform commercial type of which is amosite), plus smaller amounts of tremolite-actinolite and hornblende. Some chrysotile fibers were also noted. The authors traced the source to taconite tailings discharged at Silver Bay, Minnesota
• Main results:
  • Duluth water supply, 1973: amphibole concentrations ranged from 0.03 to 0.80 mg/liter, with a mean of 0.19 mg/liter
  • Duluth water supply: on average, 23 percent by weight of the suspended solids was identified as amphibole
  • Duluth water supply: estimated range of 1 to 30 million (10 to the 6th power) amphibole fibers per liter identified by selected-area electron diffraction, with a mass concentration of 1 to 30 micrograms per liter
  • Duluth water supply: occasional peak concentrations of up to 10 to the 9th power fibers per liter could result from resuspension of settled sediment in the water lines
  • Other locations: amphibole, particularly cummingtonite-grunerite, was below detection limits (less than 0.02 mg/liter) at Thunder Bay, Ontario, and Grand Marais, Minnesota. It was detectable at Silver Bay and in Cloquet water (also used by Superior, Wisconsin), and high (more than 0.1 mg/liter) at Beaver Bay, Two Harbors and Duluth
  • Fiber size in Duluth water: amphibole fibers as long as 20 micrometers were seen, but most were less than 5 micrometers long, with many less than 1 micrometer
  • Historical suspended-sediment samples collected by the City of Duluth water utility: those from 1939-1940 and 1949-1950 contained only trace amounts of amphibole with no detectable cummingtonite-grunerite. All samples studied from 1964-1965 contained large amounts of amphibole (average 31 percent of total inorganic solids), mostly cummingtonite-grunerite
  • The authors stated that the Duluth amphibole fiber counts, and particularly the mass concentrations, were much higher than values reported for chrysotile in 22 Ontario municipal water supplies by an earlier study. That earlier work found 0.8 million chrysotile fibers per liter (0.0002 micrograms per liter) at Thunder Bay
  • Some chrysotile fibers were also observed in the Duluth water samples
• The authors' conclusion: The authors concluded that geological and limnological data indicate the source of the large increase in amphibole material in western Lake Superior water was the taconite tailings discharged at Silver Bay since 1956
• Limitations the authors state:
  • Many amphibole fibers did not give diagnostic electron diffraction patterns, so not all fibers present were counted
  • Fiber counts for most samples were estimated from x-ray diffraction mass measurements, which assumes that the mass of amphibole is related to the number of fibers and that particle size distribution is constant
  • The x-ray diffraction amphibole concentrations were semiquantitative estimates
  • Comparison of fiber counts with published values is normally not possible because different preparation and counting methods are used

Topics

Medical terms in this study, explained in our Lexicon: Asbestiform, Amphibole Group, X-Ray Diffraction (XRD), Duluth Water Supply.

Related studies

• Analysis of amphibole asbestiform fibers in municipal water supplies — W.J. Nicholson (1974)
• Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota — B.S. Levy, E. Sigurdson, et al. (1976)
• Concentration and size of asbestos in water supplies — J.R. Millette, P.J. Clark, et al. (1980)
• Drinking water and cancer — K.P. Cantor (1997)
• Chemical contamination of California drinking water — H.H. Russell, R.J. Jackson, et al. (1987)
• Asbestos in water supplies of the United States — J.R. Millette, P.J. Clark, et al. (1983)

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