Heatwave brings spike in Ozone air pollution

Soaring temperatures recorded across the UK, and in particular the South East of England, have brought high levels of air pollution, according to readings from the UK’s air monitoring network.

But, an expected change in weather conditions into the weekend is likely to bring about an improvement in air quality, forecasts suggest.

Temperatures of up to 34C were recorded in the capital on Thursday

An air pollution warning was issued on the government’s UK Air website yesterday, after the 180 µg/m3 warning threshold for ozone was exceeded at monitoring sites Wicken Fen and Canterbury over a five hour period late yesterday afternoon (26 July).

According to the website, these conditions have carried over into today, and in its Friday outlook UK Air noted: “Widespread Moderate and isolated High levels of pollution are likely for East Anglia and far southeast England today. Elsewhere mainly Low levels of air pollution are expected with isolated pockets of Moderate pollution.”


In the capital, the London Air forecasting and monitoring service — LAQN — which is run by King’s College London, issued a ‘High’ ozone warning for parts of the city and outer suburban areas on Thursday (see story).

According to data from the Network, highest recorded ozone levels were at a monitoring station at Sevenoaks Greatness Park, where a 195 µg/m3 concentration was seen. Other sites throughout the network recorded moderate levels of pollution.

High ozone levels are most common during summer months in Europe due to the warmer temperatures and higher levels of solar radiation.

Ozone is formed in the atmosphere from emissions of pollutants such as nitrogen oxides from vehicles, organic compounds and methane from agriculture, which react with sunlight. Once formed, ozone can remain in the atmosphere for many days.

Ground-level ozone pollution has been associated with risks including lung inflammation, decreased lung function and an increase in asthma attacks.


With weather conditions expected to shift into the weekend, both the UK Air and LAQN forecasts suggest that air pollution is likely to drop over the coming days.

In its outlook forecast, UK Air noted: “Mainly Low levels of air pollution are expected for many parts of the UK due to fresh Atlantic air replacing the hot and humid air we have recently had. Isolated pockets of Moderate pollution are still possible where winds fall light.”

Scientists at King’s College London also anticipate that the change in weather conditions will bring about an improvement in air quality across the capital.

The LAQN forecast for the weekend suggested: “The brisk winds arriving from the Atlantic will also give good dispersion of locally-emitted pollutants and carry very little by way of imported pollution.

“This will bring some respite from the ozone episodes which have affected London recently.”

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