Ozone season

Ground level ozone is an air pollutant formed when nitrogen dioxide and other chemicals react with sunlight. The ozone season is the term used for the time of year when there are elevated concentrations of ozone in the atmosphere: namely in spring and summer when conditions are still and sunny.

Unfortunately, once formed, ozone can remain in the atmosphere for many days and pollutants that can generate ozone are often transported over long distances, affecting rural areas. This can damage crops as well as impact human health.

Ozone pollution tends to be highest in the countryside and in suburbs away from central London. This is because certain pollutants that are more prevalent in urban areas are able to "mop up" ground level ozone thus reducing its concentration.

Raised concentrations of ozone may cause breathing problems for sensitive individuals, such children, asthmatics and the elderly. Ozone often causes a large number of moderate pollution days during spring and summer, but these days can appear the same as lower pollution days; you can use our website to see current pollution levels.

Ozone levels are much lower indoors, especially if windows are closed.

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