In recent years, western, central and eastern Thessaloniki have all had to face the same enemy – airborne particles, dangerous pollutants that do not discriminate between industrial and other areas. «The emission of airborne particles in Thessaloniki is the highest in the European Union, double the level set by the EU (50 gm/m3) and four times what will apply in 2010,» explains Constantinos Nikolaou, chemist and environmentalist at the Thessaloniki Town Planning and Environmental Protection Organization. «Wherever you measure, throughout the urban complex, particles exceed the limit,» he said. Small-diameter airborne particles (known as PM10 and PM2.5) are considered lethal because they penetrate deeply into the respiratory system. Thessaloniki has outdone Athens, Lieges and Manchester, other cities with high concentrations of airborne particles. More than 50 percent of the particles come from gasoline-powered vehicles, with factories the next most common source. Nikolaou explained that although factories produce large quantities of pollutants, the wind blows them away from the urban surroundings, whereas those that remain in the city and are inhaled by residents are particles emitted by automobiles. The dangerous pollutants found in Thessaloniki are carbon dioxide (photochemical pollution), which exceeds the limit in central Thessaloniki, followed by ozone (another photochemical pollutant), which shows high levels on the periphery of the urban complex (for instance in Panorama and Neohorouda). Ozone behaves the same way in Athens, where the highest levels are to be found in Maroussi and Liossia. This is why solving the traffic problem by promoting public transport and increasing the number of bus lanes throughout the city will help reduce dangerous pollutants, according to Nikolaou. Some pollutants show higher levels in downtown Thessaloniki (Dimokratias Square, Tsimiski, Egnatia and Vassilis Olgas streets) than in eastern and western Thessaloniki.