Automobile Exhaust

AUTOMOBILE SMOKE ("exhaust" gases) is a mixture of substances emitted by automobiles from the exhaust pipe, resulting from the combustion of fuel materials during engine operation. Among the components of the smoke, carbon monoxide (CO) deserves especially serious attention; its content ranges, depending on the degree of fuel combustion, from 3% (when the automobile is moving) to 15% (if the automobile is idling in a cramped, closed garage). Analyses of street air in New York showed that CO content was: 0.1–0.27% on streets with heavy automobile traffic, 0.4‰ at intersections of such streets, and up to 0.5‰ or more directly near trucks and omnibuses. If one automobile follows another, persons in the rear automobile, located 10 m from the front one, are surrounded by air containing 0.1–0.2‰ CO and are therefore exposed to the danger of poisoning. The same can be noted for large cities located in deep basins, during prolonged stays on narrow streets on windless summer evenings, where long lines of automobiles are often stalled. Poorly ventilated long tunnels with heavy automobile traffic can also be dangerous regarding CO poisoning. In the air of garages with closed doors, and in the air of various departments of automobile repair shops, 0.5 to 3.0‰ CO was found, which is the cause of acute and chronic poisoning of chauffeurs, garage workers, and mechanics. According to J. Henderson, when using gasoline, CO is the only toxic substance in automobile smoke. The odorous substances resulting from the combustion of gasoline, although they do not possess toxic effects, can, in cases of increased individual sensitivity, unfavorably affect general well-being. Malodorous gases (acrolein), when present in high concentrations in the smoke, can irritate mucous membranes. If benzene, tetraethyl lead, or other toxic substances are added to the gasoline, the toxic effect of the smoke is complicated by these impurities. F. Schwarz calculated that in a large city, on a street 1 km long, no less than 100 g of lead must be emitted daily by passing automobiles. The Washington Commission for the Study of the Effects of Tetraethyl Lead concluded that there are no grounds for prohibiting the use of a mixture of 1 part tetraethyl lead and 1,300 parts gasoline. To prevent poisoning from automobile smoke, the following basic measures are recommended: designing engines with complete combustion of fuel materials, developing a method for chemically binding the toxic substances of the smoke before releasing it into the air, and rational ventilation of garages, automobile workshops, and tunnels.