Hot weather brought severe ozone episode

Last week’s record-breaking heatwave brought with it one of the worst episodes of air pollution in recent years.

Twelve sites reported a total of 57 hours above the ‘public information threshold’ of 180 micrograms per cubic metre of the respiratory irritant. This is normally exceeded by at least one monitoring station every year, but the length and distribution this time was unusually great.

The greatest hourly average figure was 233µg/m3 reported from St Osyth, near Colchester, at 7pm. But the ‘alert threshold’ of 240µg/m3, measured or predicted over three hours, does not appear to have been breached.

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