The New Zealand region of Canterbury has experienced over three years of frequent seismic activity, centred under or near the main city of Christchurch. Larger earthquakes and aftershocks have triggered liquefaction in certain parts of the city, depositing significant amounts of fine silt on the surface, which is a new source of dust emissions.
Historically, concerns about air quality in Christchurch have been dominated by emissions from wood burning in winter for domestic heating. High emissions, along with frequent temperature inversions lead to regular exceedances of the national standard for PM10 of 50 μg m-3 for a twenty-four hour average concentration. The health effects of PM10 are widely acknowledged, and regulatory drives to improve ambient air quality are succeeding in recent years.
During 2011, ratios of PM2.5 to PM10 suggested that some periods of elevated concentrations were due to the liquefaction from the earthquakes and that the silt may represent a novel air quality issue to be managed.
In addition, the earthquakes have damaged thousands of residences, causing changes in domestic heating practices as many chimneys are destroyed or currently in need of repair. This will affect emissions in upcoming winters and thus, the health burden may alter if a permanent step change in wood burning emissions is observed. However, the increased dust levels from liquefaction introduce a potentially compounding factor to any estimates of exposure.
Thus, as a result of the earthquakes, air quality in Christchurch is rapidly changing with unknown effects on exposure and ultimately, the health of the Christchurch population.
National smokefree law in New Zealand improves air quality inside bars, pubs and restaurants