Ozone alert continues into second week

Continuing hot and dry weather has seen a third air quality alert issued in just under six days, warning of the potential for high levels of ozone air pollution across parts of the country.

Last week a warning was issued through the government’s UK-Air air quality monitoring and forecasting service, after high levels of Ozone were detected at three monitoring stations in the north west.

The latest air pollution alert, issued yesterday, came after the 180 µg/m3 warning threshold for ozone was exceeded at Chilbolton Observatory and Reading New Town at around 17.00 on Sunday evening.

A forecast put out this morning suggested that widespread Moderate air pollution could be expected across England and Wales, with light winds and very warm, sunny conditions adding that there would be: “Perhaps locally High air pollution in the central south.”

The outlook for the coming week indicates that conditions will be: “Remaining settled with light winds and sunny conditions, allowing for widespread Moderate levels of air pollution to continue across many areas, perhaps locally High at times in urban areas.”


Latest data recorded at several monitoring stations on the UK Urban and Rural network, taken at 13.00 today (2 July), show moderate levels of Ozone recorded at Chilbolton, Bournemouth, Charlton Mackrell and Yarner Wood across the south of the country, as well as at Aston Hill in North Wales.

World Health Organisation guideline values suggest that people breathing in air with an average concentration of more than 100 μg/m3 over an eight hour period may create a risk of harm to health.

Measurements taken at the sites recording ‘moderate’ levels of ozone throughout the course of the day, have largely registered concentrations of ozone approaching 150 μg/m3 so far today, although none of the sites have crept above the eight-hour 100 μg/m3 average threshold.

Across London, the London Air Quality Network, run by the Environmental Research Group at King’s College is forecasting moderate levels of ozone into Tuesday.

In a bulletin issued this morning, the LAQN stated: “Hot and sunny on Tuesday with a north-easterly or easterly breeze bringing in air from high altitude over the North Sea and northern Germany.

“The presence of some ozone precursor chemicals such as oxides of nitrogen, Volatile Organic Compounds (VOCs) and carbon monoxide alongside long hours of unbroken sunshine to power conversion of these chemicals into ozone, is likely to contribute to ground level ozone formation resulting in ‘moderate’ pollution.”

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.

In 2013, a study by the Stockholm Environment Institute’s York Centre estimated that ozone pollution cost the lives of 460 people in the UK during the 2006 heatwave.

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