The main contaminant that seems to be a problem in Canterbury towns is PM10.  All monitoring stations, except Riccarton, monitor this contaminant.  In 2009 carbon monoxide (CO) is monitored at all permanent stations, sulphur dioxide (SO2) is monitored in Christchurch, Timaru and Ashburton.  Nitrogen dioxide (N02) is only monitored in Christchurch (St Albans, Riccarton and Burnside)