Corrosion, material soiling, vegetation damage and visibility reduction are additional effects of suspended particles. They also come from natural sources, such as sulphur springs. Very high concentrations may cause nausea or headaches. A colourless gas with a strong smell that is produced by the sun's photochemical action on hydrocarbons and nitrogen oxides. It is the biggest part of photochemical smog.
Ozone irritates the lungs and can make breathing difficult.
Exposure to high concentrations of ozone results in chest tightness, coughing and wheezing. It is responsible reach year for agricultural crop loss in Ontario and causes noticeable leaf damage. More than 50 per cent of Ontario's ozone comes form sources in the United States.