A review of the toxicology and epidemiology of wollastonite

Our plain-English summary of A review of the toxicology and epidemiology of wollastonite, by L.D. Maxim, E.E. McConnell (Inhalation Toxicology, 2005).

The study

• Authors: L.D. Maxim, E.E. McConnell
• Journal: Inhalation Toxicology
• Published: 2005;17(9):451-66
• Type of article: Review
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Wollastonite is a naturally occurring calcium silicate (CaSiO(3)) that is produced in both powder and fibrous forms. It is a valuable industrial mineral used in plastics, ceramics, metallurgical applications, paint, and friction products. For some applications wollastonite serves as an asbestos replacement. To varying degrees, wollastonite grades contain respirable particles/fibers, some of which have lengths and diameters that might be biologically active if deposited and retained in the lung. In this review we provide background information on wollastonite properties, markets, production and use, regulatory classification, and occupational exposure limits. We also summarize the available studies on the toxicology and epidemiology of wollastonite. We conclude that there is inadequate evidence for the carcinogenicity of wollastonite in animals and, based on strong evidence that wollastonite is not biopersistent, believe that a well-designed animal inhalation bioassay would have a negative result. The epidemiological evidence for wollastonite is limited, but does not suggest that workers are at significant risk of an increased incidence of pulmonary fibrosis, lung cancer, or mesothelioma. Morbidity studies have demonstrated a nonspecific increase in bronchitis and reduced lung function. It is prudent, however, to continue product stewardship efforts by wollastonite producers to control workplace exposures and to monitor scientific developments.

In plain English

This article was a review, not a new study. The authors summarized published research on wollastonite, a natural calcium silicate mineral sold in powder and needle-like forms. It is used in some products as an asbestos replacement. They reviewed studies of workers at a Finnish limestone–wollastonite mine and mill and at a New York State mine, plus animal studies. In the Finnish mortality study, 79 deaths occurred among 238 workers versus 96 expected. Four men died of lung cancer (SMR 0.8, 95% CI 0.22–2.05). One woman died of a rare tumor that a panel said had features similar to a diffuse mesothelioma. In the Finnish morbidity study, 9 workers (18%) had pleural plaques. In New York, 3% of workers had pneumoconiosis. An early rat study placing wollastonite on the pleura found pleural sarcomas. A rat inhalation study found lung tumors in 0/57 and 1/60 wollastonite-exposed rats, compared with 1/56 controls and 20/52 chrysotile-exposed rats. Rat studies showed wollastonite cleared quickly from the lung. The authors concluded the human evidence was limited but did not suggest a significant risk of pulmonary fibrosis, lung cancer or mesothelioma. They noted the studies had limited statistical power.

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 of published toxicology and epidemiology studies of natural wollastonite
• Who was studied: Published studies, including morbidity studies of worker cohorts in Finland and the United States (New York State), a mortality study of Finnish workers, and animal and laboratory studies
• Exposure: Natural wollastonite (calcium silicate), produced in powder and acicular (needle-like) forms; some grades are used as an asbestos replacement
• Main results:
  • In the reviewed Finnish mortality study of 238 workers, 79 deaths had occurred by the end of 1980, versus 96 expected
  • In the Finnish mortality study, deaths from cancer of the lung and bronchus included four men (SMR 0.8, 95% CI 0.22–2.05); these SMRs were calculated by the IARC working group
  • In the Finnish cohort, a 73-year-old nonsmoking woman died of a rare malignant mesenchymal tumor that a panel, on reexamination, noted showed features similar to a diffuse mesothelioma
  • In the reviewed Finnish morbidity study of 49 workers, nine workers (18%) had pleural plaques; five of them had possible or probable asbestos exposure
  • In the reviewed 1982 morbidity study of the New York State wollastonite mine cohort, pneumoconiosis was found in 3% of workers
  • In the reviewed early intrapleural rat studies (Stanton and colleagues), pleural sarcoma incidence for four wollastonite grades was 5/20, 2/25, 3/21 and 0/24, compared with 14/29 for UICC crocidolite asbestos
  • In the reviewed rat inhalation study (McConnell et al., 1991), bronchoalveolar adenoma or carcinoma occurred in 1/56 chamber controls, in 0/57 and 1/60 rats exposed to wollastonite for 12 and 24 months, and in 20/52 chrysotile-exposed rats
  • The reviewed in vivo biopersistence studies found wollastonite half-times in rat lungs of less than 1 week (inhalation) to 10–21 days (intratracheal instillation)
• The authors' conclusion: The authors concluded that the epidemiological evidence for wollastonite is limited, but does not suggest workers are at significant risk of an increased incidence of pulmonary fibrosis, lung cancer, or mesothelioma. They also concluded there is inadequate evidence for carcinogenicity in animals.
• Limitations the authors state:
  • The authors noted the limited statistical power of the epidemiological studies, as shown by wide confidence intervals
  • The authors noted that the Finnish mortality cohort was relatively small
  • The authors noted that coexposure of worker cohorts to other substances (e.g., calcite, crystalline silica and tremolite) confounds interpretation of the human studies
  • The authors noted that surface-treated wollastonites have not been studied extensively

Topics

Medical terms in this study, explained in our Lexicon: Epidemiology, Wollastonite, Silicate, Friction Products, Occupational Exposure, Pulmonary Fibrosis, Lung Cancer, Mesothelioma.

Related studies

• Product stewardship in wollastonite production — L.D. Maxim, R. Niebo, et al. (2008)
• Fibrogenic effect of wollastonite compared with asbestos dust and dusts containing quartz — E.E. McConnell (1995)
• Preliminary results from a cohort of workers exposed to wollastonite in a Finish limestone quarry — M.S. Huuskonen, J. Järvisalo, et al. (1983)
• 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)

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