Londonderry’s Marlborough Street had the highest exceedence of the EU annual mean limit value for Nitrogen Dioxide last year, it’s emerged.
The annual mean of the pollutant per cubic metre of ambient air (µgm-3) at the site was 71 µgm-3 last year.
The EU says it should be 40 at the highest.
The only other monioring sites to exceed the annual limit were Stockman’s Lane in Belfast (56) and Downpatrick Roadside (41).
Marlborough Street has exceeded the limit in each of the last three years.
Monitors at the site recorded values of 63 µgm-3 in 2012, 60 µgm-3 in 2013 and 71 µgm-3 in 2014.
Elsewhere in the city, the only other sites being monitored last year, which were at Dale’s Corner and Brooke Park respectively, recorded values of 23 µgm-3 and 14 µgm-3.
Dale’s Corner has only ever exceeded the recommended EU limit once during the period it was being monitored when it registered a value of 44 µgm-3 in 2010.
Brooke Park has never had an exceedence, whilst Dungiven, which was last monitored in 2012, registered an exceedance then with a value of 49 µgm-3.
Environment Minister Mark H. Durkan, releasing the figures, said: “In 2014, there were 13 sites still monitoring nitrogen dioxide, and three of these (Belfast Stockman’s Lane, Derry Marlborough Street, and Downpatrick Roadside) showed exceedences of either the EU annual mean limit value or UK Air Quality Strategy Objective.”
According to the World Health Organisation (WHO) the current guideline was set to protect the public from the health effects of gaseous pollution.
“At short-term concentrations exceeding 200 μg/m3, it is a toxic gas which causes significant inflammation of the airways,” it said.
“NO2 is the main source of nitrate aerosols, which form an important fraction of PM2.5 and, in the presence of ultraviolet light, of ozone.
“The major sources of anthropogenic emissions of NO2 are combustion processes (heating, power generation, and engines in vehicles and ships).
“Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase in association with long-term exposure to NO2. Reduced lung function growth is also linked to NO2 at concentrations currently measured (or observed) in cities of Europe and North America,” it said.