Lead Concentrations in Detroit,New York,and Los Angeles Air

Lead concentrations in air were measured at 12 sites in Detroit, New York and Los Angeles as part of a program to relate automobile emissions and polynuclear aromatic hydrocarbons in air. The information on lead is reported separately because of the current interest in lead as an air pollutant. Sampling was conducted by means of a large “absolute” filter and equipment contained in a step-van truck. A portion of the filter was macerated in nitric acid and the lead determined spectrographically. The combined annual average lead concentration for four sites in metropolitan Los Angeles was approximately 40% higher than the combined averages of either the five sites in metropolitan New York or the three sites in metropolitan Detroit. Concentrations ranged from 0.4 ug/M³ at Santa Monica, to 18.4 ug/M³ at a Los Angeles Freeway Interchange. Concentrations were generally highest in freeway areas, intermediate in commercial areas, and lowest in residential areas. They were about 40% higher in daytime than at night. Average lead concentrations were highest during autumn in New York and winter in Los Angeles reflecting an inverse relationship with wind speed. Correlation coefficients between lead and carbon monoxide, at all sites, were statistically non-zero with 99% confidence and varied from 0.75 to 0.96. Lead concentrations in this study were higher than concentrations reported by others for Detroit, New York, and Los Angeles, presumably because sampling in this study was closer to traffic. However, concentrations in this study were lower than in-traffic concentrations given in the literature.