It’s been sobering to see the smoke from the Australian bushfires travel so far and have such an impact in New Zealand. To date the real time air quality monitoring data suggests there have been two exceedances of the national environmental standard for PM10 that can be attributed to the Australian bushfires more than 2,000 km away. These occurred on 6 December 2019 in the North Island and 7 December 2020 at the top of the South Island.
More recently the Australian bushfire smoke has caused dramatic orange haze (South Island 1 January 2020) and a darkening of the skies (Auckland 5 January 2020). Surprisingly, these events were not associated by significant increases in daily PM10, with maximum concentrations typically less than 30 µg/m3 as a 24-hour average. We hypothesise that the smoke from the Australian bushfires that has been transported this far is primarily ultrafine particulate matter (i.e. < 0.1 micrometres in diameter), which is why despite being so highly visual, it is not registering as significant on a mass basis.
With respect to the health effects of ultrafine particulate, the World Health Organisation notes (WHO, 2013):
There is increasing, though as yet limited, epidemiological evidence on the association between short-term exposures to ultrafine (smaller than 0.1 µm) particles and cardiorespiratory health, as well as the health of the central nervous system. Clinical and toxicological studies have shown that ultrafine particles (in part) act through mechanisms not shared with larger particles that dominate mass-based metrics, such as PM2.5 or PM10.
Social media is currently lighting up with people reporting exacerbated asthma and respiratory issues which may, or may not, be caused by the Australian bushfire smoke. However, any breathing difficulties should be taken seriously. If in doubt – refer to your GP.
The Ministry of Health has just posted a public health update on their website. Real-time particulate monitoring data (thanks to the superb work undertaken by regional councils throughout New Zealand) is available here.
And spare a thought for our Australian kin.
[Photo credit: Himawari satellite]
 WHO, (2013). Review of evidence on health aspects of air pollution – REVIHAAP Project. Technical Report. Regional Office for Europe. Copenhagen. Denmark.