Toxicity of Some Atmospheric Pollutants

Examples of the harmful effects produced in man by contaminated fogs are now well known. The general clinical picture is one of respiratory embarrassment with increased dyspnoea, cyanosis, progressive cardiovascular embarrassment, and possibly fever and toxaemia if secondary infection occurs. It was similar in the London fogs of 1948 and 1952, in the Meuse Valley fog of 1930, and in the Donora incident in 1948. The young, the old, and those with pre-existing respiratory or cardiac disease are the more seriously affected, and the postmortem findings are consistent with the inhalation of an irritant substance. The nature of the irritant substance is still unknown, although various contaminants have been arraigned by different workers. Sulphur dioxide, carbon monoxide, automobile exhaust fumes, and fluorine compounds have been suggested (Firket, 1931; Roholm, 1937; Regan, 1953). Unfortunately no lethal fog has been adequately sampled during the incident, nor have its chemical and physical properties been determined. It is therefore difficult to plan any experimental work on the toxic effects of polluted fog. The obvious contaminants must be studied first, but in the absence of precise knowledge of the possible concentration or the physical state of each substance in a smog the practical implications of the results obtained must be in doubt. Such a study will, however, indicate which contaminants are potentially dangerous and those which may be harmless, although synergistic effects may alter this simple classification. We at Porton have examined effects on animals and human beings of various substances and mixtures which might be important atmospheric pollutants. The results of these experiments have been or are being reported in detail elsewhere, but it did seem desirable to summarize our progress to date and to consider the toxicological picture as a whole. The use of animals must necessarily form part of such an investigation ; the relative toxicities of possible contaminants and any synergistic effects can only be accurately determined by using subjects drawn from a homogeneous population, which cannot be obtained with human beings. In general most species of animals are less sensitive to these toxic pollutants than is the susceptible proportion of the human population.