Analysis of amphibole asbestiform fibers in municipal water supplies

Our plain-English summary of Analysis of amphibole asbestiform fibers in municipal water supplies, by W.J. Nicholson (Environmental Health Perspectives, 1974).

The study

• Author: W.J. Nicholson
• Journal: Environmental Health Perspectives
• Published: 1974;9:165-72
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Details are given of the techniques used in the analysis of asbestiform fibers in the water systems of Duluth, Minnesota and other cities. Photographic electron diffraction and electron microprobe analyses indicated that the concentration of verified amphibole mineral fibers ranged from 20 x 10(6) to 75 x 10(6) fibers/l. Approximately 50-60% of the fibers were in the cummingtonite-grunerite series and 20% were in the actinolite-tremolite series. About 5% were chemically identical with amosite. A wide variety of analytical techniques must be employed for unique identification of the mineral species present in water systems.

In plain English

This laboratory study described methods for identifying amphibole mineral fibers in drinking water and reported fiber measurements, mainly from Duluth, Minnesota. The article stated that an iron ore company at Silver Bay discharged taconite tailings into Lake Superior and that bottom currents carried much of this material to Duluth. Using electron microscopy, electron diffraction and electron microprobe analysis, the author reported 20 x 10^6 to 75 x 10^6 verified amphibole fibers per liter of Duluth water, about 5 to 30 micrograms per liter. Levels were similar across the city's three main reservoirs. The author stated that these counts were probably too low by at least a factor of two. About 98% of the fibers were under 5 micrometers long. Roughly 50-60% were in the cummingtonite-grunerite series, about 5% matched the chemistry of amosite, and about 20% were in the actinolite-tremolite series. Water from Superior, Wisconsin had 4 x 10^6 fibers per liter. None were detected in New York City or Grand Marais, Minnesota water. The author concluded that fiber shape alone cannot identify the minerals and that several techniques are needed. The article did not report on health effects.

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: Laboratory analysis of water and tailings samples by transmission electron microscopy, electron diffraction and electron microprobe (x-ray) analysis
• Who was studied: Municipal water from Duluth, Minnesota (three main reservoirs), which draws water from Lake Superior, compared with water from Superior, Wisconsin, New York City and Grand Marais, Minnesota, plus samples of taconite tailings discharged at Silver Bay, Minnesota. Sampling dates were not given.
• Exposure: Amphibole fibers (cummingtonite-grunerite series, including fibers chemically identical to amosite; actinolite-tremolite series; hornblende) in taconite tailings, which the article states were discharged at about 70,000 tons daily into Lake Superior
• Main results:
  • Duluth water contained approximately 20 x 10^6 to 75 x 10^6 verified amphibole fibers per liter
  • In Duluth water these counts corresponded to approximately 5 to 30 micrograms of amphibole fibers per liter
  • Fiber concentrations were similar throughout the Duluth water system
  • In Duluth water, about 98% of the fibers were under 5 micrometers long, and the most probable length was about 0.7 micrometers
  • For Duluth fibers verified as amphibole by electron diffraction, the most probable width was 0.15 micrometers
  • Of the fibers in the Duluth water system and in the tailings, approximately 50-60% were in the cummingtonite-grunerite series, with approximately 5% having the same chemical composition as amosite asbestos
  • Of the fibers in the Duluth water system and in the tailings, approximately 20% were in the actinolite-tremolite series and 2-4% were hornblende
  • About 20% of the amphibole fibers had compositions that could not be assigned to any of the listed minerals
  • Table 3 analyzed 192 fibers from the Duluth water system and 91 from the tailings. Duluth water: cummingtonite-grunerite 90 (47%), actinolite-tremolite 43 (22%), hornblende 8 (4%), other 51 (27%). Tailings: 56 (62%), 18 (20%), 2 (2%) and 15 (16%) in the same categories.
  • Water from Superior, Wisconsin, which draws only part of its water from Lake Superior, contained 4 x 10^6 amphibole fibers per liter
  • No amphibole fibers were detected in water from New York City or from Grand Marais, Minnesota, which is up-current from Silver Bay
  • Some tailings fibers appeared as bundles resembling chrysotile, so identification based on fiber shape alone can be misleading
• The authors' conclusion: The author concluded that a wide variety of analytical techniques is needed to identify uniquely the mineral species of fibers in water systems
• Limitations the authors state:
  • The author stated that supplementary data suggest the reported concentrations are underestimated by at least a factor of two
  • Amphibole fibers too thin or too thick to give unambiguous visual diffraction patterns were left out of the tabulated counts
  • Mass concentrations were estimated from assumed fiber depths, and the two estimation methods usually differed by a factor of two or three

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Group, Asbestiform, Electron Microprobe Analysis, Mineral Fiber, Cummingtonite-Grunerite, Actinolite, Tremolite, Amosite.

Related studies

• Asbestiform amphibole minerals: detection and measurement of high concentrations in municipal water supplies — P.M. Cook, G.E. Glass, et al. (1974)
• Concentration and size of asbestos in water supplies — J.R. Millette, P.J. Clark, et al. (1980)
• 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)
• Effect of population density on the results of the study of water supplies in five California counties — P.M. Conforti (1983)
• Three potential sources of microfungi in a treated municipal water supply system in sub-tropical Australia — N.B. Sammon, K.M. Harrower, et al. (2011)

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