Waikato Regional Council scientists believe breaches of national standards for air quality at a busy northern Hamilton intersection may be linked to roadworks in the area.
Since March this year, the regional council has been measuring the amount of nitrogen dioxide (NO2) in the air at the intersection of Te Rapa Road and Avalon Drive.
The national environmental standard is breached when in one hour average NO2 levels exceed 200 micrograms per cubic metre (μg/m3) of air 10 or more times in a 12 month period.
Between 1 March and 23 May NO2 levels exceeded 200 μg/m3 more than 50 times. At its highest, levels reached 556 μg/m3 between 7am and 8am on Wednesday, 30 March.
There have been no further breaches since Friday, 20 May.
Council air quality scientist Dr Nick Kim said analysis of the results has found a possible link with road works in the vicinity over summer and autumn.
“Until late May, there were more heavy trucks than usual travelling through the Te Rapa Road and Avalon Drive intersection, and these would have added to the already high base-load.
“The last exceedances coincide with the winding down of roading works for the winter, and there have been no further breaches in more than five weeks of ongoing monitoring,” Dr Kim said.
“The majority of exceedances occurred on weekdays during the morning peak and when there was little wind to disperse emissions.
“Almost all nitrogen dioxide near busy intersections like this one comes from motor vehicles, and especially from diesel vehicles. The greatest amounts of NO2 are produced when engines are under load, such as pulling away from traffic lights, so NO2 levels tend to be higher on busy roads that have a lot of heavy vehicles.
“A large heavy vehicle such as a truck can emit around 10 times more NO2 than a petrol car. Even a small diesel car can emit four times more NO2 than a petrol-run car.”
Dr Kim said people are exposed to NO2 by breathing in air. Previous research by the former Auckland Regional Council showed that NO2 contributions from a motorway can remain elevated up to at least 300 metres away from the roadside.
It can irritate eyes, nose, throat, and lungs, possibly causing coughing, shortness of breath, tiredness, and nausea.
The national environmental standard requires regional councils to monitor the air in cases where national standards are likely to be breached, and undertake this monitoring in the part of an airshed where exceedances are greatest or most frequent. Waikato Regional Council believes that in the Hamilton airshed, exceedances of the national environmental standard for NO2 are the greatest and most frequent at the Te Rapa Road and Avalon Drive intersection. Monitoring will continue until the exceedances no longer occur.
Policy and transport group manager Vaughan Payne said the Te Rapa and Ngaruawahia sections of the Waikato Expressway, due for completion in 2013/14, are expected to ease congestion in northern Hamilton.
“The council’s Regional Land Transport Strategy supports construction of nationally and regionally significant traffic corridors, such as these two sections of the Expressway, which will channel long distance vehicles off local roads and onto major arterial roads.
“Although this will continue to be a busy intersection, the completion of the Expressway sections are likely to result in a reduction in NO2 emissions,” Mr Payne said.
In the meantime, the public can help to relieve congestion and reduce pollution through their choice of vehicles, or by car-pooling or catching a bus. You can plan your bus trip by visiting www.busit.co.nz or calling 0800 4 BUSLINE (0800 4287 5463).
The council will continue to notify the public of any further breaches of NO2 at this site on a monthly basis.