The Environmental Protection Agency's raised concerns about air pollution levels here.
New EPA figures show emissions of three of the five main air pollutants increased in 2016.
One of the chemicals - Ammonia - went above EU safety limits for the first time.
Emissions of two of the other air pollutants, nitrogen oxides and non-methane volatile organic compounds, while in compliance with EU limits for now, are increasing.
Emissions of sulphur dioxide continue to decrease. These were well below the required EU emission limits, substantially due to the use of lower sulphur content fuels in electricity generation and transport.
Particulate matter emissions declined in 2016. Future emissions will depend largely on the quantity and quality of solid fuel used in the residential and commercial sectors.
Stephen Treacy, Senior Manager with the EPA, said,
Our figures show that emissions of three of the five main pollutants are going in the wrong direction. Higher emissions of these pollutants will cause damage to air quality and health and make future compliance with EU limits more challenging.