PM particles may contain smoke, dust, soot, metals, nitrates, sulphates , water and rubber from tyres . Air pollution is causing around 467,000 premature deaths in Europe every year, the European Environment Agency (EEA) has warned. People in urban areas are especially at risk, with around 85% exposed to fine particulate matter (PM2.5) at levels deemed harmful by the World Health Organization (WHO). These particles are too small to see or smell, but have a devastating impact. PM2.5 can cause or aggravate heart disease, asthma and lung cancer. http://www.bbc.com/news/world-europe-38078488