Samenvatting
The concentration of particulate lead in the atmosphere in the central reserve of the M4 motorway was measured in order to determine the long-term trends and any seasonal fluctuations in the levels. The lead content of the air was shown to have decreased by 7% per annum and a seasonal cycle existed which could be attributed almost entirely to variations in the wind speed. The legislation reducing speed limits in the winter of '73- '74 led to a marked reduction.