(19)Scientific evidence shows that sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM 10 and PM 2,5 ), benzene, carbon monoxide, arsenic, cadmium, lead, nickel, some polycyclic aromatic hydrocarbons and ozone are responsible for a number of significant negative effects on human health, and are linked to several non-communicable diseases, adverse health conditions and increased mortality. Impact on human health and the environment occurs via concentrations in ambient air and via deposition.