Product stewardship in wollastonite production

Our plain-English summary of Product stewardship in wollastonite production, by L.D. Maxim, R. Niebo, S. Larosa, et al (Inhalation Toxicology, 2008).

The study

• Authors: L.D. Maxim, R. Niebo, S. Larosa, B. Johnston, K. Allison, E.E. McConnell
• Journal: Inhalation Toxicology
• Published: 2008;20(14):1199-214
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In July 2002, NYCO Minerals, Inc., discovered a heretofore unknown contaminant in its wollastonite ore. The contaminant was first believed to be tremolite asbestos. Immediate efforts were made to eliminate this material. Additional studies were initiated to fully characterize the contaminant and its distribution in the ore body. Subsequent study by NYCO and their consultants led to the identification of the contaminant as a transition material (TM) intermediate between tremolite and talc. In vitro dissolution rate measurements indicated that the TM dissolved much more rapidly than tremolite asbestos. This article provides background information on wollastonite mineralogy and NYCO's product stewardship program (PSP). At present, NYCO Minerals uses selective mining to control the trace levels of TM in the ore and finished product verified by periodic monitoring of workplace air and finished product.

In plain English

This case history described a product stewardship program at NYCO Minerals' wollastonite mine in Willsboro, New York. In July 2002, outside tests reported less than 0.3% of what was first identified as tremolite asbestos in bulk wollastonite. Several early air samples taken by federal mine safety (MSHA) staff reportedly exceeded the MSHA limit. The contaminant occurred in inclusions of 2 to 10 cm or more, which mining avoided. Ore levels fell during 2003 and 2004. Personal air samples measured for "tremolite asbestos" fibers were all non-detects from 2004 to 2006; in 2002, 28 of 34 (82.4%) were at or below the detection limit. A consulting laboratory's electron microscopy found the material's crystal structure more consistent with fibrous talc. The laboratory concluded it was a transitional material, not asbestiform tremolite. In dissolution tests, it was more durable than wollastonite but less durable than tremolite by more than two orders of magnitude. The authors concluded that, to the extent durability determines toxicity, the data suggest it presents less of a health hazard than asbestiform tremolite. They called their results a snapshot in time.

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: Case history (descriptive report) of a company product stewardship program. It included bulk and air monitoring data, mineral characterization by electron microscopy, and in vitro dissolution (durability) tests
• Who was studied: NYCO Minerals' Willsboro, New York wollastonite deposit. Samples were ore, finished product, and personal air samples from workers in the mine, mill and processing facilities, 2002 to 2006
• Exposure: A contaminant in wollastonite ore first identified as tremolite asbestos (asbestiform tremolite). The consulting laboratory later identified it as a non-asbestiform transitional material intermediate between tremolite and talc
• Main results:
  • In July 2002, external laboratory tests reported low concentrations (less than 0.3%) of "tremolite asbestos" in bulk wollastonite shipped from the Willsboro mine
  • Several of the initial personal monitoring samples taken by MSHA reportedly exceeded the MSHA exposure limit
  • The contaminant was not evenly mixed through the ore. It was found in relatively large inclusions (2 to 10 cm or more), which could be avoided during mining
  • The apparent "tremolite asbestos" concentration in weekly (later biweekly) ore composite samples decreased during 2003 and 2004
  • Personal air samples measured for "tremolite asbestos" fiber concentrations, 2002: 28 of 34 (82.4%) were at or below the detection limit, and one sample was in the 0.5 to 1.0 f/cm3 range. 2003: 167 of 173 (96.5%) were at or below the detection limit
  • All personal air samples measured for "tremolite asbestos" fibers were non-detects from 2004 to 2006 (104, 88 and 29 samples). Detection limits ranged from 0.003 to 0.011 f/cm3
  • Electron diffraction showed that the crystal structure of the NYCO contaminant was more consistent with fibrous talc than with tremolite asbestos
  • The RJ Lee Group concluded that the contaminant was not asbestiform tremolite but a non-asbestiform transitional material (TM)
  • In dissolution tests, wollastonite half-times were 3.29 and 3.31 weeks, and the transitional material samples had half-times of 16.57 to 33.91 weeks. The transitional material was more durable than wollastonite but less durable than tremolite by more than two orders of magnitude
  • The estimated half-time for the tremolite control sample (commercial tremolite from South Korea) was 908.4 weeks, approximately 17.5 years
  • The NYCO Health Committee recommended an internal exposure guideline of 0.2 f/cm3 for the transitional material pending ongoing studies
• The authors' conclusion: The authors concluded that, to the extent durability determines toxicity for crystalline materials, the data suggest the transitional material presents less of a health hazard than asbestiform tremolite. They also stated that the elements of the stewardship program had proven successful
• Limitations the authors state:
  • The authors said the results should be viewed as a "snapshot in time" of an ongoing program
  • There was substantial sample-to-sample variability in the ore composite data
  • The test materials differed in dimensions, so half-times had to be corrected for differences in surface area
  • Research on characterizing the transitional material was still ongoing

Topics

Medical terms in this study, explained in our Lexicon: Wollastonite, Tremolite, Talc, Mineralogy.

Related studies

• A review of the toxicology and epidemiology of wollastonite — L.D. Maxim, E.E. McConnell (2005)
• Fibrogenic effect of wollastonite compared with asbestos dust and dusts containing quartz — E.E. McConnell (1995)
• Mesothelial cell proliferation and biopersistence of wollastonite and crocidolite asbestos fibers — J.L. Macdonald, A.B. Kane (1997)
• Wollastonite exposure and lung fibrosis — M.S. Huuskonen, A. Tossavainen, et al. (1983)
• Wollastonite fibers in vitro generate reactive oxygen species able to lyse erythrocytes and activate the complement alternate pathway — M. Governa, L. Camilucci, et al. (1998)
• Investigation of the biodurability of wollastonite and xonotlite — B. Bellmann, H. Muhle (1994)

Browse more research in Inhalation Toxicology, or return to medical research.