Air pollution linked to road traffic in Ireland breached the specified EU emission ceiling in 2011, the Environmental Protection Agency (EPA) said today.
The latest EPA emissions data showed levels of nitrogen oxide (NOx) in the air exceeded the target level of 65 kilotonnes by 2.6 kilotonnes in 2011.
High nitrogen oxide emissions can pose a threat to human health as a respiratory irritant, particularly in people with asthma.
The road transport sector represents the largest source of NOx emissions, accounting for 55 per cent of total NOx emissions in 2011.
Emissions of NOx fell by 47 per cent between 1990 and 2011 as a result of stricter EU standards for emissions from cars and heavy duty vehicles in combination with the economic downturn in more recent years.
However, the EPA said advances in emission controls have been "largely off-set" by increases in vehicle numbers and fuel use during the economic boom.
"Reducing NOx emissions requires travelling less by car as well as the uptake of new vehicles with improved emission control technologies," it said.
In the power generation sector, the agency said a substantial reduction in NOx emissions had been achieved as a result of emission control technology and fuel-switching from oil to gas and renewable energy.
EPA senior manager Dr Eimear Cotter said: "The key to decreasing nitrogen oxide emissions lies in reducing travel and incentivising the purchase of cleaner vehicles with improved emission controls."
“Changing behavioural patterns in these two areas will reduce emissions so contributing to a cleaner, healthier environment and a better quality of life”.
The EPA figures show that levels of sulphur dioxide (SO2), volatile organic compounds (VOC) and ammonia (NH3), the other three main air pollutants, were below the EU emission ceilings.
The main sources of these emissions are power generation, residential and commercial sectors for SO2; solvent use and transport for VOCs; and agriculture for NH3.
Dr Cotter said: "The switch to low sulphur fuels and low solvent products such as paints is welcome, and has kept Ireland below EU emission ceilings for sulphur dioxide and volatile organic compounds.
"Ammonia emissions have stayed reasonably constant since 1990, however, ambitious targets under Food Harvest 2020 could put pressure on ammonia emissions into the future."