Silicic acid, calcium salt

Endpoint summary

Description of key information

Weight of Evidence:
Epidemiological study (Hanke et al. 1984): lung function changes at exposures >30 mg/m3 (total (inhalable) concentration)
Subchronic repeated dose inhalation study (1-yr, rat): LOAEL 10 mg/m3 based on minor pulmonary effects for one calcium silicate (respirable concentration)
Health surveillance data: no cases of lung fibrosis or work-related obstructive or restrictive lung effects observed during 26 years of health surveillance

Additional information

A Weight of Evidence approach was followed to determine the repeated dose toxicity of Silicic acid, calcium salt.

 

Two epidemiological studies are available. In the study by Hanke et al. (1984), which is summarized under 7.10.2 (Epidemiological data). In this study medical and environmental surveys of employees in a wollastonite mine and mill were reported in 1976 and 1982. Investigations included chest x-rays, pulmonary function tests and symptom surveys. In 1982, employees from a nearby electronics manufacturer were included in the survey. Results showed changes in the FEV1/FVC ratio and in the peak flow rate in Wollastonite workers with a long-term cumulative exposure of >30 mg-years/m3 total dust.

In the study by Koskinen et al. (1997), which is also summarized under 7.10.2 (Epidemiological data), a cohort of 49 workers in a Finnish limestone-wollastonite mine and mill was followed from 1981 to 1990. There was no relationship between years of wollastonite exposure and risk of pleural plaques or changes in pulmonary function. There was no relationship between years of exposure to wollastonite and increased risk of chronic bronchitis. High resolution computerized tomography scans did not identify evidence of fibrosis in two workers with ILO 1/0 classification for lung opacities on chest x-ray. No wollastonite fibers were found in the bronchiolar lavage fluid of 4 workers, 2 with pleural plaques. Both of these workers with pleural plaques had asbestos bodies in their bronchiolar lavage fluid, wherea one had a history of prior asbestos exposure but the other did not. In conclusion, no evidence was found that long-term exposure to wollastonite causes parenchymal fibrosis of the lung and pleura. Furthermore, the absence of wollastonite fibers in the bronchoalveolar lavage (BAL) fluid indicates that wollastonite fibers are poorly retained in human lungs

 

Furthermore, the results of a repeated dose inhalation study with rats, published by Davis et al. (1983) were included in the dossier. In this study, three groups of laboratory rats were exposed to dust from three different calcium silicate insulation materials at a respirable concentration of 10 mg/m3. The animals were approximately three months old at the start of the experiment and were exposed for 12 months (seven hours per day, during 224 days/year). After the exposure period, the rats were allowed to live out their normal life span. No major pulmonary damage was detected. It was concluded that this study produced no evidence that the exposure affects the survival or health of laboratory rats.

 

Additionally, 26 years health surveillance data in a production plant did not show cases of lung fibrosis or work-related obstructive or restrictive lung effects (included in 7.10.1, Health surveillance data).

Justification for classification or non-classification

Based on the available data, the test substance does not have to be classified for repeated dose toxicity, in accordance with the criteria outlined in Annex I of 1272/2008/EC.