Australian dust storm September 23, 2009. Image from NASA (CC)
As a kid growing up in the North Island of New Zealand, I don’t recall ever seeing dust storms of the type seen in the Australian outback. In recent weeks, we’ve seen clouds of ochre dust blowing in from South Australia. The worst dust storms converge on the eastern seaboard, shrouding cities in an eerie, fog-like miasma.
You may recall the really bad one (September 2009) when motorists in Sydney and Brisbane drove with their lights on in the middle of the day.
Fortunately, the red dust (which gets into everything), lasts only a few days, although the customary early spring westerlies tend to blow them east in sequence.
While he was writing about the Dust of Uruzgan (Afghanistan) at the time, songwriter Fred Smith could have been describing dust storm conditions in the outback.
“It’s as fine as talcum powder on the ground and in the air
And it gets in to your eyes and it gets in to your hair…
…It gets in the machinery and foils every plan…”
Yes, and it gets in rainwater tanks when the next rains wash the dust off iron roofs. Residents of Auckland, some 1,500 kms away, have previously reported how dust storm drift from Australia turned their roofs a curious pink colour.
While New Zealand can fairly claim that it does not have dust storms in-country, it certainly sees the worst of them drifting across the Tasman. Reports of red ochre dust settling on the New Zealand Alps date back more than a century. You may have seen reports like these in recent years:
A series of dust storms in 2019, intermingling with smoke from bushfires, reached New Zealand\s Southern Alps, some 2,000 kms away. The ABC published photos, taken by adventurer Liz Carlsson, of the Mount Aspiring glacier sporting a red/pink discolouration.
University of Queensland geographer Hamish McGowan told the ABC it was not uncommon for this to occur during periods of severe drought in eastern Australia.
“In the right conditions, dust particles can be blown across the Tasman Sea by north-westerly winds, coming down on the Southern Alps in rain or snow and leaving behind an orange discolouration,” Professor McGowan said.
The same phenomenon can be seen in the Australian Alps. Black or grey discolouration is more likely to be ash falling from bushfire smoke clouds. The population in general is more aware, now that we have the technology to show images taken on mobile devices, or from satellites or drones.
Dust storms quickly remind me that I should take my asthma preventer medication as directed. Like so many asthmatics, I’m guilty of forgetting/ignoring the inhalant medication if I’m feeling free of symptoms. Australia’s 2.7 million asthmatics ought to know that asthma attacks can be random. They are also triggered by air quality factors including industrial air pollution, a high pollen count, smoke, dust and indoor environmental hazards (house dust, pet dander).
I do remember that 2009 dust storm, as we were in Brisbane for Queensland Ballet’s season launch at QPAC. People with any kind of respiratory condition should be on red alert when a dust storm comes calling. Luckily, I had my asthma inhaler with me (and needed it).
The numbers of people presenting at hospital emergency departments with respiratory symptoms were well above average on that day. Analysis of the air pollution found the 2009 dust storm to be far worse than any bushfire or dust storm event of the previous 15 years.
The Environmental Health Journal said extremely high levels of particulate matter were recorded on September 23, 2009.
Daily average levels of coarse matter (<10 microns (μm) peaked over 11,000 μg/m3 and fine (<2.5 μm) particles over 1,600 μg/m3.
The World Heath Organisation guideline is that any level of fine particulate matter over 35 μg/m is considered unhealthy.
(We should also remember that major cities known for air pollution routinely record <2.5 μm levels of 50 and higher).
The EHJ authors reported that the dust storm returned on September 26, with elevated PM (particulate matter) levels of an “unprecedented order of magnitude higher than those experienced during previous years.”
The fine particles are the main problem for people with respiratory complaints, as they deeply penetrate the airways.
The 2009 dust storm originated in drought-stricken western New South Wales. Last week’s storms reportedly started in outback South Australia.
Reports of giant dust storms in Australia pre-date the technology which can now spot them from above. Dust storms were common during the series of droughts that afflicted Australia in the last decade of the 19th century. Still, scientists are predicting that climate change will make dust storms larger and more frequent.
A Science Daily report predicts that climate change will amplify dust activity in parts of the US in the latter half of the 21st century.
A statistical model developed by researchers at Princeton University and the National Oceanic and Atmospheric Administration (NOAA) predicts that climate change may lead to the increased frequency of spectacular dust storms that will have far-reaching impacts on public health and infrastructure.
Despite their dramatic visual impact, Australia’s dust storms are a blip on the the global chart. The World Meteorological Organisation says most sand and dust storms occur in the arid and semi-arid regions of Northern Africa, the Arabian Peninsula, Central Asia and China. Australia, America and South Africa make minor, but still important, contributions.
The WMO estimates that 40% of aerosols in the troposphere (the lowest layer of Earth’s atmosphere) are dust particles from wind erosion. Global estimates of dust emissions vary between one and three gigatons per year.
Spectacular though they are when they appear on the horizon, dust storms are infrequent and often blow over in a day or two. Bushfire smoke, however, as the 2019/2020 Black Summer bushfires demonstrated, have far more serious ongoing health effects.
An Asthma Australia report details the effects of the bushfire smoke between July 2019 and March 2020. The air pollution caused a public health emergency, adding to the direct bushfire impacts already felt by communities. Bushfire smoke contains high concentrations of fine particulate matter.
“At its worst, the smoke resulted in the Air Quality Index reaching more than 25 times the hazardous level (in Canberra, January 1 2020),” the report states.
The Air Quality Index reached greater than 10 times the hazardous rating on multiple occasions in certain areas of Sydney between November and January.
“It is estimated the bushfire smoke was responsible for more than 400 deaths, 2,000 respiratory hospitalisations and 1,300 presentations to the Emergency Department for asthma.”
The most recent study by the Australian Bureau of Statistics found that 2.7 million Australians (one in nine or 11.2% of the total population) had asthma in 2017-18.
“Over the last 10 years, the prevalence of asthma increased in the Australian population from 9.9% in 2007-08 to 11.2% in 2017-18″.
This is as good a time as any to remind you that September 1-7 is National Asthma Awareness Week.
Don’t leave home without your puffer.