Air pollution levels in Dublin have breached healthy standards as set out by the World Health Organisation (WHO).

Researchers from NUI Galway's School of Physics conducted the air pollution study, along with Ryan Institute's Centre for Climate and Air Pollution Studies.

It found Dublin's PM2.5 air pollution (Particulate Matter airborne smog, smoke and haze particles smaller in size than 2.5 microns) can surpass the recommended 24-hour air quality guideline.

Over a two-month winter period from late November 2016 to late January 2017, the daily Average Quality Guideline (AQG) was breached every one in five days.

While during late evening hours, hourly levels were frequently 10-times higher than the 24-hour threshold.

The research has been published in the international journal, Nature Sustainability.

Researchers deployed a pilot air pollution network- made up of highly-sophisticated, next-generation air pollution fingerprinting technology.

It was able to identify specific sources of even the smallest amounts of air pollution.

It attributed 70% of the extraordinarily-high pollution levels to peat and wood burning, despite only a small percentage of residential homes using peat or wood as a primary fuel type.

It found all of the exceedance levels were driven by peat and wood rather than coal or oil, or even non-residential sources such as traffic.

The contribution from coal use was seen as 'strikingly low' and, researchers say, highlights the success of the Smoky Coal Ban first introduced in Dublin in 1990.

Stock image of peat burning | Image: NUI Galway

The study found the exceedance levels were driven by solid fuels - some of which are marketed as more 'climate-friendly' than fossil-fuels.

Professor Colin O'Dowd, director of NUI Galway's Centre for Climate and Air Pollution Studies, said: "The disproportionate sensitivity of air pollution levels to solid fuel, including climate-friendly 'low-carbon' solid biomass fuel is quite concerning since fuels like wood are one of the most popular choices of 'low carbon' biomass fuel and consumption of this fuel type is set to double across Europe by 2020 (from 2016), and to triple globally by 2030.

"The results from this study suggest that along with promoting low-carbon or carbon-neutral solid fuels, it is especially important to fully consider the health impact from any associated air pollution emission."

"The EU is currently conducting a major review of its Clean Air for Europe directive with a view to delivering on the aim of its 7th Environment Action Program to adopt World Health Organisation air quality values by 2020.

"It is important that this innovative research, which highlights the disproportionate impact of solid fuels on air quality, is fully considered in developing future EU legislative and regulatory frameworks to protect public health and the environment."

He said while the smoky coal ban did its job where it was applied, "we need to remain vigilant and consolidate those victories by developing policies that continue to reduce air pollution and improve public health."

The Average Quality Guideline is more-strict than current regulatory levels - but is not to be regarded as a safe level since adverse health impacts can still occur well below the threshold.