Henderson and Haggard, 1 in 1923, reported the presence of carbon monoxide in recognizable concentrations in the air of New York and New Haven streets. Their discussion made physicians aware of the possibility of the existence of chronic or repeated carbon monoxide poisoning, to be looked for not only in the usual places, such as dwellings with leaky gas pipes, but also in streets where motor traffic was very dense. We decided to examine the blood of a number of subjects exposed in the most evident manner to the danger.
It appeared advisable to investigate traffic patrolmen. It was recalled that during the past few years many of these men, on duty in the most congested mercantile districts of Philadelphia, have complained at the end of the day's work of symptoms that might be due to slight carbon monoxide anoxemia: headache, slight nausea and muscular weakness. These symptoms were noted