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Little improvement in air quality despite lockdown: Woodburners and bonfires contribute to pollution

Despite wide-ranging restrictions on travel during the coronavirus lockdown, monitoring stations have shown only small improvements in Sheffield's air quality.

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Photo by Mark Ramsay (Creative Commons).

Graham Turnbull of Clean Air For Sheffield has been tracking any changes through his Twitter account, using both his own network of sensors and official Defra stations.

But he warned against reading too much into the data, as it can be dramatically affected by a number of different factors including wind direction.

"Simply showing that air pollution levels are lower than before the coronavirus restrictions or lower than last year is not the whole story," Turnbull told Now Then.

"In order to understand what the real effects are of drastically reduced traffic we need to be able to correct for weather conditions, especially wind speed and direction which we know can make a big difference. This analysis will eventually be carried out."

"We also must remember that transport is only one factor," he continued. "In the case of [particulate matter] PM2.5, which causes most air quality related health impacts, transport is only 12%. Domestic burning can be three times that."

Barnsley Road, which includes the main entrance to Northern General Hospital, actually saw slightly worse air quality in March 2020 compared to March 2019, according to Defra data.

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Pollution on Barnsley Road compared to 2019. Picture by Clean Air For Sheffield.

A monitoring station on Devonshire Green has recorded a 16% drop in PM2.5, but 2019 saw a 33% reduction during the same period and a 36% increase in 2018.

Turnbull points out that the data for 2020 was already showing an improvement in air quality before the lockdown.

PM2.5 consists of ultra-fine dust particles that bypass our natural defences and enter every organ in the body. It's mostly created by agriculture and solid fuel burning rather than transport.

According to the Devonshire Green station levels of NO2 pollution, which is caused by diesel cars and trucks, rose in 2018 but fell by 11% over the same period in 2019 and 20% in 2020.

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Devonshire Green pollution in 2020 compared to previous years. Picture by Clean Air For Sheffield.

Anecdotally, air pollution activists have reported increases in wood burning as people have spent more time at home, although this will fall with warmer weather.

Residents of some cities are being urged not to light wood burners and bonfires, as the pollution caused could exacerbate respiratory problems caused by coronavirus. Some areas of Canada have banned woodburning complete during the lockdown.

The Guardian has reported big falls in PM2.5 pollution in London, Cardiff and Bristol during the lockdown, but its survey did not include Sheffield.

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