Continuous measurements of the atmospheric concentration of carbon monoxide, total hydrocarbons, methane, acetylene, ethylene, total oxides of nitrogen and lead were made 5m from the kerbside of the North Circular Road, near the Finchley Road junction, London, during May 1979. This road carried an average of 3500 vehicles/hour. The concentrations of pollutants were of the same order of magnitude and similar in range to those found in other busy urban roadside environments. Pollution from this site arose mainly from the traffic although there was some evidence of other sources contributing to the non-methane hydrocarbon, acetylene, ethylene and total oxides of nitrogen concentrations. The carbon monoxide levels exceeded the World Health Organization guidelines for the 2- and 3-hour average concentration, the latter by a small amount. The maximum 8-hour average concentration measured exceeded the United States Air Quality Standard by about 1 ppm. The estimated nitrogen dioxide concentrations exceeded the 1-hour level recommended by WHO and the annual value spefified in the United States Standards. The level of lead measured did not exceed that recommended by the Department of Health and Social Security Working Party. It is probable that the levels monitored in this survey are of the same order of magnitude as those experienced in the most exposed properties in this area. (A)

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