Road tunnels can contain ultrafine (<100 nm) particles in concentration levels so high they have the potential to harm drivers and passengers, according to a recently-published study by researchers in Australia.
The study, which appeared in the July issue of the journal Atmospheric Environment, measured ultrafine particle concentration levels outside a vehicle travelling through the 4-km, twinbore (eastbound and westbound) M5 East tunnel in Sydney.
Sampling was undertaken using a condensation particle counter (CPC) mounted in a vehicle traversing both tunnel bores at various times of day from May through July, 2006. Supplementary measurements were conducted in February, 2008. The study involved more than 300 trips through the four kilometers of the M5 East tunnel, with journeys lasting up to 26 minutes, depending on traffic congestion.
What this study aimed to do was identify the concentration levels found in the tunnel. It generated a huge body of data on the concentrations and the results show that, at times, the levels are up to 1000 times higher than in urban ambient conditions.—Professor Lidia Morawska, Queensland University of Technology
Morawska said drivers and occupants of new vehicles which had their windows closed were safer than people travelling in older vehicles.
People who are driving older vehicles which are inferior in terms of tightness and also those riding motorcycles or driving convertibles, these people are exposed to incredibly high concentrations. When compared with similar studies reported previously, the measurements here were among the highest recorded concentrations.—Lidia Morawska
Morawska said tunnels were becoming an increasingly necessary infrastructure component in many cities across the world.
When governments are building tunnels for urban design reasons, they should also consider the impact these tunnels are having on the environment and to people’s health. The study highlights why governments need to consider how they are going to deal with the air pollution levels inside the tunnel and removal of ultrafine particles in the outside environment.—Lidia Morawska
The study was conducted jointly by Professor Richard de Dear and his doctoral candidate, Mr Luke Knibbs from Macquarie University, in collaboration with Professor Morawska and Dr Kerrie Mengersen from QUT.
Luke D. Knibbs, Richard J. de Dear, Lidia Morawska and Kerrie L. Mengersen (2009) On-road ultrafine particle concentration in the M5 East road tunnel, Sydney, Australia. Atmospheric Environment Volume 43, Issues 22-23, Pages 3510-3519 doi: 10.1016/j.atmosenv.2009.04.029