Skin, throat and eye irritation have been reported in workers exposed to high atmospheric levels of kieselguhr. Its predominant effect on prolonged inhalation of high concentrations is pneumoconiosis, a lung condition which is at first potentially reversible but which may progress to fibrosis. Flux-calcined (heated) kieselguhr containing high levels of cristobalite (crystalline silica) has generally exhibited a greater potency than the unheated material, but even unheated kieselguhr containing no detectable crystalline silica has caused fibrosis in laboratory animals. Short-term rat feeding studies have revealed adverse effects (stomach damage) only when kieselguhr has been given in a deficient diet. In limited studies, there was no definite evidence of carcinogenicity in rats fed kieselguhr, and no tumours were reported in rats, guinea-pigs or mice inhaling either natural or calcined kieselguhr for up to 3 yr. Malignant tumours of the lymphoid tissue developed after a single injection of natural kieselguhr into the lining of the abdominal cavity in mice, and of cristobalite into the lining of the thoracic cavity of rats.

Date of Publication: 1989

Number of Pages: 9

CAS Number*: 61790-53-2


Format: PDF available for immediate download

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