[Polluting agents and sources of urban air pollution]

This paper is an up-to-date review of the scientific evidence on mechanisms of pollutant generation and health effects for a number of urban air pollutants. The review focuses on main sources and health effect of ozone and photochemical smog, benzene, polycyclic aromatic hydrocarbons, and particulate matter. These agents are "priority pollutants", generated by vehicle traffic, and their regulation is currently being examined by the European Council and the European Commission. The aim is to reach, by the year 2010, values lower than 180 micrograms/m3 for ozone as maximum hourly concentration, 2.5 micrograms/m3 for benzene as an annual average, 93 micrograms/m3 for nitrogen dioxide as 98 degrees percentile of hourly concentrations, 50 micrograms/m3 for particulate as a daily average. The goal can be achieved only by means of immediate interventions on emissions.