An oral hearing into the proposed N15 bypass of Bundoran and Ballyshannon in Donegal heard testimony on the potential interaction between overhead power lines and particles emitted by traffic.
Part of the proposed route passes near Cathaleen's Fall hydroelectric station and its power lines. It is also close to a number of residents objecting to the proposed route.
Ms Kathleen Dolan, on behalf of the objectors, said the route would be located near the town's schools.
An environmental scientist, Mr Michael Meeneary, suggested those schoolchildren living near the bypass would be prone to poorer air quality and greater susceptibility to respiratory disorders such as asthma.
Dr Duncan Laxen, an air quality expert, on behalf of Donegal County Council, rejected assertions regarding the health effects of traffic emission particles interacting with corona ions from powerlines.
"The evidence I have presented shows no grounds related to the interaction between particles and the corona ions discharged from the high voltage power line to not proceed with the development of the road," he said.
Earlier he accepted that high voltage power lines could release corona ions - normally associated with bad weather - but only with high lines of 132kV and above. However, he admitted there were limited circumstances when there might be an interaction between particles from the road and the power lines.
The hearing continues.