Table 3.

A summary of animal studies conducted with perlite.

Pathway	Species	Results	Source
Inhalation	Guinea pig & rat	In an 18-month inhalation study, guinea pigs and rats (numbers, strain, or sex not given) were exposed to perlite dust at a concentration of 226 mg/m3. No significant pulmonary reaction, including fibrosis, was observed. No further details were given. The authors concluded that perlite acted as an inert or nuisance dust.	Vorwald, 1953, cited in Cooper, 1975 and Health Council of the Netherlands, 2003.
Inhalation	Guinea pig	Inhalation exposure of 284 mg/m3, 8 h/d, 5.5 d/wk. for six months “appeared to stimulate the progression of experimental tuberculosis”. When exposure ceased the tuberculosis infection progressed for about eight months and then began to heal and ultimately was arrested.	Schepers, 1955 as reported in Cooper, 1975.
Inhalation	Guinea pig	Guinea pigs were exposed to perlite dust at mean airborne concentrations of 0 or 6.6 mg/ml for 30 min/d, 5 d/wk, for 24 wk. Another group was exposed to fir bark dust. Perlite mass median aerodynamic diameters (MMADs) ranged from 1.7 to 1.9 µm. No pulmonary fibrosis or extensive destruction of parenchymal tissues was observed, but the authors con noted “moderate to severe” changes in the lungs for both dusts. The authors concluded that perlite particles were more than just a nuisance dust.	McMichael et al., 1978, 1983. The reported dose might be a misprint, but is extremely high. Health Council of the Netherlands converted this to 6,600 mg/m3 and noted it was unrealistically high.
Intratracheal injection	Guinea pig	Nine perlite products were tested in guinea pigs, by weekly intratracheal injection of 0.5 ml of a 5% perlite suspension in saline for 3 wk. At 4 to 12 months after the last injection, no evidence of pulmonary fibrosis was shown.	Vorwald, 1953, cited in Cooper 1975.
Intratracheal instillation	Rat	A single intratracheal instillation of a 75 mg/ml saline dose of perlite (18–30% quartz) produced a “foreign body reaction” in white male rats, but no pulmonary fibrosis was observed (post observation period not reported).	Timar et al., 1965 as cited in Health Council of the Netherlands, 2003.
Intratracheal instillation	Rat	A single 50 mg suspension of crude or expanded was administered intratracheally to albino rats. Nine months later, it was found that expanded perlite caused more lung fibrosis than crude perlite, but the degree of fibrosis was not reported.	Borshchevkii et al., 1967 as cited in Health Council of the Netherlands, 2003.
Intratracheal instillation	Rat	Rats given a single intratracheal instillation of 50 mg perlite dust showed pulmonary fibrosis at 12 to 18 months following administration. The perlite composition was not specified.	Liu et al., 1988, as cited in Health Council of the Netherlands, 2003.
Intratracheal instillation	Rat	Intratracheal infusing (instillation) of 5 mg perlite dust in 5% alcohol did not result in a strong pulmonary fibrogenic reaction in rats, at 12 wk after administration. No more details were provided.	Ueda et al., 1978 as cited in Health Council of the Netherlands, 2003.
Acute oral toxicity	Rat	Acute oral toxicity tests in rats ingesting perlite were performed by the Rosner-Hixon Laboratories in 1977. The results of the tests showed that the acute oral LD50 of perlites for rats is greater than the largest dose administered in the test (10 g/kg body weight).	Schundler Company, 2002, http://www.schundler.com/perlitehealth.htm.
Acute oral toxicity	Rat	In 1982, the WIL Research Laboratories conducted studies to examine the acute oral toxicity, if any, of agglomerated filter aid in albino rats. The study showed no signs of systemic toxicity, and concluded that the LD50 was greater than the highest dose level administered to the rats (10 g/kg body weight.)	Schundler Company, 2002, http://www.schundler.com/perlitehealth.htm.
Oral ingestion	Mouse	Ohkuma et al. (1972) and Itoh et al. (1981) performed acute toxicity studies using dd/y and C3H/He mice. The results showed no acute toxicity despite large doses. The estimated LD50 was 12 960 mg/kg or more in each case.	Cited in Sakai & Nagao, 1985.
Oral ingestion	Mouse	Groups of male and female mice were given diets containing 0%, 1%, 10%, 20% perlite for 28 wk. Appearance, behavior, and food consumption of mice of treated groups were not affected during the experimental period.	Sakai & Nagao, 1985.