measurements of the concentration of particulate lead in the atmosphere have been made on and near the m4 motorway at harlington. the motorway here is very heavily trafficked, with approximately 70000 petrol-engine vehicles per day. measurements of the concentration of atmospheric lead have also been made inside a vehicle using this stretch of road and of the concentration of lead in surface soils near the motorway. the average lead levels found in the centre of the motorway in dry weather in the autumn of 1972 were 20.6u g/m3 for the period 0700 to 1900 hours and 15.1u g/m3 for the 24 hour period on weekdays. the driver of a vehicle was found to be exposed to three-quarters of the lead levels found in the motorway atmosphere. lead in the atmosphere and in the surface soil fall off rapidly with distance from the motorway. the medical effects of these pollutant levels are not discussed in this report. (a)

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