Toxicity Profile for Kieselguhr (1989)

Abstract

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.