Air pollution levels doubled in some parts of Dublin city centre on a car-free day earlier this year.
College Green and Dame Street were closed to traffic on Sunday September 22nd as part of European Mobility Week.
It saw the area pedestrianised from 7am until 7pm, while more than 20 bus routes were diverted to allow for family friendly events.
However according to a council debriefing, the ban on cars and buses actually increased pollution in some areas.
Pollution levels on Lord Edward Street doubled.
While levels at Trinity College were 50 percent higher than the following Sunday.
The minutes of the meeting were released to the Irish Times under the Freedom of Information Act.
The event in September followed a number of trial days during July and August, which saw College Green pedestrianised.
