stomach. The patient recovered after surgery to remove the damaged tissue (Haj et al., 1980).

Labeled FC-11 administered to four healthy males by inhalation of a single breath held for 5 s was eliminated from the body rapidly. Results in humans appeared to parallel those in rats in more detailed studies (Williams et al., 1974). The investigators found rapid transfer of FC-11 to blood followed by distribution to fat, from which release was slow. Mergner et al. (1975) exposed a male and a female volunteer to radiolabeled FC-11 at 1,000 ppm for 7–17 min. Recovery of administered radioactivity in exhaled air was essentially complete (99% and 79%). Errors in collection of rapidly eliminated gases account for the differences from 100%. Only a very small fraction of the administered radioactivity (less than 0.2%) was exhaled as ¹⁴CO₂ or excreted as nonvolatile urinary activity. The impurities in FC-11—namely, chloroform and carbon tetrachloride—known to be metabolized could account for all the radioactivity found in urine and exhaled CO₂ after exposure to FC-11.

Cardiac effects have been studied in healthy subjects and patients with bronchopulmonary disease. None of the subjects exhibited cardiotoxic effects (Fabel et al., 1972).

Human volunteers were exposed to FC-113 (similar to FC-11) at 500 or 1,000 ppm for 6 h/d, 5 d/wk during a 2-wk period. No adverse changes were seen in performance of complex mental tasks, clinical status, or results of biochemical tests. Breath analysis did not reveal a significant buildup of FC-113 (Reinhardt et al., 1971).

FC-11 has not shown appreciable oral toxicity in rats and dogs in either acute or chronic studies (Haskell Laboratory, 1970; NCI, 1978). The chronic investigations include 1-mo, 90-d, and 2-yr studies. FC-11 was tested on the intact skin of mice. It was well tolerated by the skin, but retarded the recovery of wounds and burns and regrowth of hair (Quevauviller, 1960; Quevauviller et al., 1963). Dermal application of FC-11 to rabbit skin did not produce any lesions (Scholz, 1962). Transient conjunctival irritation was observed after application of FC-11 solution to the rabbit eye. No irreversible eye damage was seen (Haskell Laboratory, 1970; Kudo et al., 1971).

The LC₅₀ of FC-11 for rats in a 4-h exposure is 26,200 ppm (Haskell Laboratory, 1970). A 30-min exposure of rats at 50,000 ppm caused no signs of intoxication. Similar exposure at higher concentrations caused clinical signs of central nervous system depression. Concentrations of 100,000 ppm or more were fatal after less than 30 min (Lester and Greenberg, 1950). Acute exposure of other species of laboratory animals produced similar effects (Caujolle, 1964; Haskell Laboratory, 1970; Nuckolls, 1933; Scholz, 1962).

Rats, guinea pigs, monkeys, and dogs were continuously (24 h/d) exposed to FC-11 at approximately 1,000 ppm for 90 d. One monkey died on day 78, but its death was not definitely linked to exposure to FC-11. No other animals were affected. No compound-related pathologic changes were observed. Another group of animals was