The Variation in the Toxicity of Phosgene for Small Animals With the Duration of Exposure

Abstract

In so far as the toxic effects of a lethal inhalant depend upon the amount of material absorbed these effects must depend upon the dosage (Ct) to which animals are exposed, where C=the concentration of the gas in mg. per cubic metre and t =the time of exposure in minutes. It must also depend upon the rate of inhalation and the efficiency of absorption of the gas in the respiratory tract. The present experiments show quantitatively how the median lethal dose of phosgene expressed as the L(Ct)50 varies with the exposure time (t). From the data it is possible to deduce the probable extent to which different species reduce their breathing rate in an irritant gas.The expression for toxicity or lethal index (L) advanced by Haber (cf. Prentiss, 1937) was L=CtvG .(1) where C=concentration of toxic substance, t=time of exposure, v=volume of air breathed in per minute, and G =body weight in Kg. In general, for any one species under the same conditions vIG is constant, so that for any one species Ct would be constant. Thus the lethal index, or the median lethal dose, L(Ct)50, should be constant for any one species if the breathing rate is unchanged. American work on the toxicity of phosgene for dogs (Geiling, 1944;Prentiss, 1937) showed that the "lethal index " rose from 4,500 mg. min./m.3 when t was 2 min. to 12,000 mg. min./m.3 when the exposure time was 75 min. This increase in the lethal dose with increase in exposure time can be corrected for on the assumption that the organism can eliminate a constant amount of the toxic agent. By introducing an elimination factor C0 which may be assumed to be equal to the just harmless concentration, the formula becomes

Air Pollution Toxicology--A Brief Review of the Role of the Science in Shaping the Current Understanding of Air Pollution Health Risks

“…Prior to the London smog incident, animal toxicological studies of air pollution had distinctively military or workplace themes. Studies focused on gases like phosgene with endpoints of lethality or lung pathology (Boyland et al, 1946) or analogous studies with particulate inhalants found in industrial settings, like mining (Ray et al, 1951). However, the 1950's post-London Smog saw the emergence of toxicological studies focusing on the industrial air pollution as encountered by the public.…”