One of the reasons for concern over air pollution is that it contains toxic dust particles that can affect people's health when inhaled.
Fine particles contain mostly man-made carbon, lead, sulphur and nitrogen compounds.
Some of the nuisance coarse particles are gypsum, limestone, marble, calcium carbonate, silicon and silicon carbide. People's noses filter out large dust particles naturally, but cannot do so with the fine man-made particles, which may be drawn into and deposited in the lungs. These deposits include particles containing sulfuric acid, arsenic, beryllium and nickel. One study reports that sulfates from sulphur-containing compounds given off by fossil fuels and automobiles cause 21,000 premature deaths per year in one region alone. They are believed to aggravate respiratory diseases including asthma, chronic bronchitis and emphysema and cause shortness of breath and irritated eyes.