Cold weather causes high air pollution in London

Particulate matter monitored at ‘very high’ and ‘moderate’ levels at several sites in London on Wednesday and Thursday (January 16-17) due to low wind and cold weather

Particulate matter was monitored at ‘high’ and ‘very high’ levels at various sites in London this week due to low wind and cold air, according to King’s College’s Environmental Research Group (ERG).

Levels of particulate matter PM10 peaked at ‘very high’ levels at some sites in London this week

The highest level of PM 10 was monitored at a station in the City of London on Upper Thames Street near Monument station, which peaked at 10 — the top of the scale — according to the ERG’s London Air website.

Also in the City of London, a station on Beech Street recorded peak levels of PM 10 at nine on the scale, as did a monitoring station in Brent, North West London, near the north circular road.

Several sites also monitored pollution levels in the ‘moderate’ banding (from four to six), such as stations in Knightsbridge, Euston Road in Camden and on Old Kent Road in Southwark.

According to the London Air site: “Low wind speeds and cold settled air led to poor pollution dispersion on 16th and 17th January 2013. This caused PM10 to reach ‘very high’, the top level of the Daily Air Quality Index, at two locations in London along with widespread ‘moderate’ PM10, PM2.5 and nitrogen dioxide.”

It added that the Upper Thames Street station measured “significantly higher PM10 levels than most other busy roadside sites.

“We suspect that there could have been an additional local contribution from the resuspension of road salt in this busy enclosed location.”

However, commenting on nitrogen dioxide levels, the site said: “A change to snowy conditions has brought about an improvement in air pollution concentrations, though two sites (Westminster – Oxford Street and City of London – Upper Thames Street) have continued to measure ‘moderate’ nitrogen dioxide.”

Air pollution levels in the UK, including particulate matter, are monitored using the index approved by the Committee on Medical Effects of Air Pollution Episodes (COMEAP). This system uses a 1-10 index, with monitored levels of air pollution from 1-3 considered ‘low’, 4-6 ‘moderate’, 7-9 ‘high’ and pollution levels reaching 10 considered ‘very high’.

More information is available on the King’s College’s London Air website.