These 5 images show how air pollution changed over Australia’s major cities before and after lockdown



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Elena Sánchez-García, Universitat Politècnica de València and Javier Leon, University of the Sunshine Coast

Have you recently come across photos of cities around the world with clear skies and more visibility?

In an unexpected silver lining to this tragic crisis, urban centres, such as around Wuhan in China, northern Italy and Spain, have recorded a vastly lower concentration of air pollution since confinement measures began to fight the spread of COVID-19.

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Likewise, the Himalayas have been visible from northern India for the first time in 30 years.

But what about Australia?

Researchers from the Land and Atmosphere Remote Sensing group at the Physical Technology Center in the Polytechnic University of Valencia – Elena Sánchez García, Itziar Irakulis Loitxate and Luis Guanter – have analysed satellite data from the new Sentinel-5P satellite mission of the Copernicus program of the European Space Agency.

The data shows a big improvement to pollution levels over some of our major cities – but in others, pollution has, perhaps surprisingly, increased.

These images measure level of nitrogen dioxide in the atmosphere, an important indicator of air quality. They show changes in nitrogen dioxide concentrations between March 11 to March 25 (before lockdown effectively began) and March 26 to April 11 (after lockdown).

Why nitrogen dioxide?

Nitrogen dioxide in urban air originates from combustion reactions at high temperatures. It’s mainly produced from coal in power plants and from vehicles.

High concentrations of this gas can affect the respiratory system and aggravate certain medical conditions, such as asthma. At extreme levels, this gas helps form acid rain.

Coronavirus: nitrogen dioxide emissions drop over Italy.

Declining nitrogen dioxide concentrations across Europe in the northern hemisphere are normally expected around this time – between the end of winter and beginning of spring – due to increased air motion.

But the observed decreases in many metropolises across Europe, India and China since partial and full lockdowns began seem to be unprecedented.

Nitrogen dioxide levels across Australia

Preliminary results of the satellite data analysis are a mixed bag. Some urban centres such as Brisbane and Sydney are indeed showing an expected decrease in nitrogen dioxide concentrations that correlates with the containment measures to fight COVID-19.

On average, pollution in both cities fell by 30% after the containment measures.

Like a heat map, the red in the images shows a higher concentration of nitrogen dioxide, while the green and yellow show less.



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CC BY-ND

On the other hand, nitrogen dioxide concentrations have actually increased by 20% for Newcastle, the country’s largest concentration of coal-burning heavy industry, and by 40% for Melbourne, a sprawling city with a high level of car dependency. Perth does not show a significant change.



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CC BY-ND

CC BY-ND

We don’t know why pollution has increased in these cities across this time period, as 75% of Melbourne’s pollution normally comes from vehicle emissions and most people are travelling less.

It could be because the autumn hazard reduction burns have begun in Melbourne. Or it may be due to other human activities, such as more people using electricity and gas while they stay home.

Pollution changes with the weather

Understanding how air pollution changes is challenging, and requires thorough research because of its variable nature.

We know atmospheric conditions, especially strong winds and rain, are a big influence to pollution patterns – wind and rain can scatter pollution, so it’s less concentrated.

Blue skies over Chinese cities as COVID-19 lockdown temporarily cuts air pollution.

Other factors, such as the presence of additional gases and particles lingering in the atmosphere – like those resulting from the recent bushfires – also can change air pollution levels, but their persistence and extent aren’t clear.




Read more:
Even for an air pollution historian like me, these past weeks have been a shock


Changes should be permanent

If the decrease in nitrogen dioxide concentration across cities such as Brisbane and Sydney is from containment measures to fight COVID-19, it’s important we try to keep pollution from increasing again.

We know air pollution kills. The Australian Institute of Health and Welfare estimates around 3,000 deaths per year in Australia can be attributed to urban air pollution.

Yet, Australia lags on policies to reduce air pollution.




Read more:
Australia needs stricter rules to curb air pollution, but there’s a lot we could all do now


COVID-19 has given us the rare opportunity to empirically observe the positive effects of changing our behaviours and slowing down industry and transport.

But to make it last, we need permanent changes. We can do this by improving public transport to reduce the number of cars on the road; electrifying mass transit; and, most importantly, replacing fossil fuel generation with renewable energy and other low-carbon sources. These changes would bring us immediate health benefits.The Conversation

Elena Sánchez-García, Postdoctoral researcher at LARS group, Universitat Politècnica de València and Javier Leon, Senior lecturer, University of the Sunshine Coast

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The smoke from autumn burn-offs could make coronavirus symptoms worse. It’s not worth the risk



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Don Driscoll, Deakin University; Brian Oliver, University of Technology Sydney; Courtney Alice Waugh, Nord University; Marcel Klaassen, Deakin University, and Veerle L. B. Jaspers, Norwegian University of Science and Technology

It’s hard to forget the thick smoke plumes blanketing Australia’s cities and towns during the black summer. But consecutive days of smoke haze can also come from planned burns to reduce fuel loads, and fires set after logging.

Expanding planned burning is often touted as a way to mitigate the risk of bushfires rising with climate change. But the autumn burn-off season is bad news for the COVID-19 pandemic, as smoke exposure can make us more vulnerable to respiratory illnesses.




Read more:
Logging burns conceal industrial pollution in the name of ‘community safety’


In fact, doctors in the Yarra Valley, Victoria, are campaigning for better air quality monitors. They argue burn-offs are a serious health risk during this pandemic, particularly with asthma inhaler stocks in limited supply.

Yes, planned burns can be useful, but they offer limited protection from bushfires and, right now, they pose an immediate health risk. It’s a reasonable bet that planned burning will do us more harm than good in 2020.

The same can be said of other sources of smoke, including from logging regeneration burns, wood heaters, backyard burn-offs and burning fossil fuels.

How does smoke from bushfires hurt our lungs?

Smoke pollution from the black summer may have killed more than 400 people, and sent 4,000 people to the hospital.

Bushfire smoke includes fine particles – less than 2.5 micrometers in size (one micrometre is a ten-thousanth of a centimetre) – that can reach to the ends of our lungs and enter the bloodstream. They compromise our immune system, weakening our antiviral defences.

Smoke also has a toxic mix of metals and organic chemicals that include known carcinogens. Even short term exposure increases hospital admissions and ambulance call-outs in Australia for chronic obstructive pulmonary disease, asthma, cardiovascular attacks and other health effects.

It’s not just humans – health impacts from smoke extends to wildlife, with smoke reducing their ability to mount an immune response and increasing their stress.

The ecological effects of smoke can also compromise animal survival, including making it harder for them to forage.

Exacerbating COVID-19

Smoke exposure causes inflammation in the lungs, as does coronavirus infection. But it’s a not a simple equation; they likely act in a synergistic way with complex interactions.

Recent studies have linked worse outcomes of COVID-19 infections with long-term cigarette smoking and air pollution, both of which have similar chemical components to wood smoke.

New research from the USA shows average air pollution with one extra microgram of fine particles per cubic metre is associated with a 15% higher death rate from COVID-19.

In other words, if COVID-19 has a base death rate of about 1 in 100, and fine particles in air pollution span from near one microgram/litre to higher than 12 in major urban centres, then the death rate could more than double to 2.65 per 100 infections.




Read more:
Bushfire smoke is everywhere in our cities. Here’s exactly what you are inhaling


Research into other viral infections shows just two hours of exposure to smoke can make people more susceptible to respiratory infections. But what we’re uncertain about is if short term exposure to smoke would illicit the same dire consequences – dramatically higher death rates – as there appears to be with long-term exposure to air pollutants.

What’s more, men could be more at risk than women. Men find it harder to fight off the flu than women, and prior exposure to wood smoke can make flu symptoms worse in men.

Planned burning is under pressure

The amount and pattern of planned burning is under pressure to change. Some commentators are campaigning for increased planned burning, but others are asking for less, and the Victorian firefighter chief has said it’s no silver bullet.

While planned burns aim to reduce wildfire, it’s not yet clear whether this will ultimately alter the amount of smoke over communities.

On the one hand, planned burns could pump more smoke into the atmosphere than wildfires because
larger areas need to be burned, smoke can build up and hang around for longer, and planned burns could produce more toxic smoke by burning wetter fuels.

On the other hand, planned burns have lower severity and are more patchy than wildfires, so burn less of the vegetation in a given area, potentially producing less smoke.




Read more:
The burn legacy: why the science on hazard reduction is contested


What about protection? Planned burns can make firefighting easier for a few years after fire. But current rates of planned burning give little protection for houses when wildfires are driven by extreme weather.

Planned burns within a few hundred metres of houses can give protection but must occur frequently, such as less than every five years. We shouldn’t expect towns to endure local smoke pollution this often.

A matter of timing

In the context of COVID-19, the seasonal timing of fires is also important.

Flu risk is lowest in the summer months, and COVID-19 might peak in late winter. This means smoke from wildfires in summer may have less impact than smoke from planned burns in autumn and spring.




Read more:
How does bushfire smoke affect our health? 6 things you need to know


The coming summer is unlikely to bring a repeat of last summer’s fires because so much forest is already burnt.

So, even if COVID-19 spills over into 2021, the compounding smoke risk from wildfires is likely to be lower than smoke from planned burns in autumn and spring.

Not worth it

All things considered, it’s not worth the health risk to conduct planned burns, logging regeneration burns or other burning this year while the pandemic continues to sweep through the country, particularly in areas close to towns such as the Yarra Valley.

Still, whether or not planned burns will change our total exposure to smoke from bushfires, the effects of climate change are definitely bringing more fire and with it more smoke.

This means we can expect to have to deal with interactions between virus risks and smoke risks more often in the future.The Conversation

Don Driscoll, Professor in Terrestrial Ecology, Deakin University; Brian Oliver, Research Leader in Respiratory cellular and molecular biology at the Woolcock Institute of Medical Research and Professor, Faculty of Science, University of Technology Sydney; Courtney Alice Waugh, Associate Professor in Immunology and Disease, Nord University; Marcel Klaassen, Alfred Deakin Professor and Chair in Ecology, Deakin University, and Veerle L. B. Jaspers, Professor, Norwegian University of Science and Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.