To compare the relative exposure to and uptake of air pollutants between modes of commuter transport, measurements of personal exposure to PM_2.5 were obtained over an 18 month period (January 2005 to June 2006) in Dublin city centre, Ireland. In total, 468 samples were recorded comprising journeys equally divided between the four main modes of commuter transport in Dublin, in 2005/06. These were the private car (45%), the pedestrian (22%), the public bus (18%) and the cyclist (6%), accounting for over 90% of urban commuters in Dublin. Samples were also recorded along two fixed routes approaching/exiting the city centre at fixed times of the day (morning and evening peak traffic flows, 08:00-09:00 and 17:00-18:00). Route 1 approached from the north and was approximately 3 miles in length and ran from Trinity College Dublin in the city centre along the quays and north in the direction of the N3, a major commuter corridor. Route 2 was a slightly longer route, approximately 3.5 miles in length, which ran from Trinity College Dublin in the city centre, along Dame Street, and on westwards to St. James Hospital. Route 2 was less consistently congested than Route 1 with variable amounts of traffic congestion throughout its length.