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Why was there a spike in pollution during the European heatwave?

Ozone levels in late June
Ozone levels in late June Copyright Copernicus Atmosphere Monitoring Service
Copyright Copernicus Atmosphere Monitoring Service
By Sinead BarryRafael Cereceda
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Increasingly, Peuch said, we are becoming aware that even low levels of pollutants pose health risks.


Ozone is a pollutant, the concentration levels of which spiked drastically during Europe's heatwave last week. In an exclusive interview with the Head of the Copernicus Atmosphere Monitoring Service, Vincent-Henri Peuch told Euronews about air pollution, the heatwave and what cities have been doing to combat levels of the pollutant ozone across the world.

Why is heat affecting ozone levels?

One of the conditions necessary to produce ozone, the pollutant which spiked dramatically in Europe last week, is sunshine. "In periods where there's lots of sunshine and high temperatures, it's a very good condition for ozone to develop," said Peuch.

When temperatures are extremely high there are more pollutants are emitted, he continued. For example, petrol can evaporate from cars, vegetation emits more volatile organic compounds.

"All this, combined with sunshine, means that there is a high level of ozone when there are high temperatures," according to Peuch.

During European heatwaves in the past, a direct correlation was shown between the rising temperatures and respiratory problems experienced by the public. According to experts, this is due to the fact that ozone increases when temperatures rise. Although it is too early for hospitals to have released figures for the June heatwave, Peuch said he expected that it would show a similar trend.

We are increasingly becoming aware that even low levels of pollutants pose health risks, he said.

Normal levels of ozone lie approximately between 100-120 µg/m³. Last week, some European cities saw concentrations above the "hazardous" level of 180 µg/m³.

What can individuals do to protect themselves during these episodes?

There are two kinds of actions to take, said Peuch. "The first thing is to reduce exposure. So, when there is an episode of ozone forecast, avoid doing sports that will mean you need to breathe more and intake more pollutants."

He also recommended individuals stay indoors to minimise their intake of pollutants.

"The other thing is to reduce the cause of pollution," he continued. Despite admitting that only so much could be done at an individual level, he insisted it was possible to reduce emissions.

On days when the temperature is high, "taking public transport instead of private cars is a good thing. If everybody does this and respects the reductions in speed which are imposed, they will contribute to reducing the emission precursor and reduce the severity of the episode."

"It's something which is very important to mention that there's nothing to do about a heatwave because, well, it's the weather but for air pollution it is possible. It is possible to reduce emissions and reduce the severity of an episode."

What's the relationship between climate change and air pollution?

"First of all, air pollution and climate change share the same root cause, which is emissions from human activities."

The relationship between the two phenomena is complex, yet clearly connected.

Many emissions, such as nitrogen dioxide (NO2) or aerosol are short-lived and contribute more to air pollution than climate change. The processes that create these emissions, however, also emit, gases like carbon dioxide (CO2).


"CO2 is not necessarily a problem for air quality but it is a big problem for the accumulation of greenhouse gases in the atmosphere," and thus directly affects climate change, Peuch explained.

"So, taking measures to cut down on CO2 emissions can also bring short-term benefits because it will cut down on air pollutant emissions."

"If we look at the changing climate, the clearest signal that can be seen is that the frequency of drought periods and heatwaves is very likely to increase. In such cases, unless the emissions of pollutants like NO2 or the volatile compounds have been reduced drastically we will still see some episodes with ozone."

Peuch stressed that these kinds of predictions were not totally reliable.


"The climate will not change uniformly so it is pretty hard to have a one-off solution" that will happen in every part in the world.

Which industries most affect ozone concentrations?

Largely, the cause of ozone concentrations varies depending on region, meaning that there is no one answer. However, one industry that the expert is sure emits ozone is the transport industry, and often in surprising ways.

"Actually, the pollution from cities which are near the sea is bigger from ships than car traffic." Meteorologists are becoming increasingly aware of the pollution caused by ships, explained Peuch. "We can see ship tracks and the effect of ships from satellite observations that we have in some countries."

Nonetheless, cars remain a key source of pollutants like ozone, the overall cause "is a mix of things", he added.


What about air traffic?

Pollution from aeroplanes operates differently to other kinds of transport, making an evaluation of its impact complicated. In contrast to cars or ships, an aircraft injects pollutants into the atmosphere at approximately 10,000 metres above the ground — not at the level we breathe.

The impact, therefore, is of less concern in terms of short-term heatwaves and ozone levels but may indeed be affecting climate. That being said, sooner or later "all the emissions will get back to the ground."

To put the impact into perspective, Peuch said that "as a rule of thumb, the emissions from an aircraft at an airport are similar to the emissions from the cars and traffic travelling to the airport."

Which countries are most successful in combatting air pollution?

According to Peuch, the country that is making the most progress in combatting air pollution is China. As recent as five years ago "the situation with pollution in China was really terrible" he explained.


Despite the renowned sunny summers in the country, air pollution meant that many cities were not even able to see a blue sky.

"Now China is taking very, very aggressive measures to reduce emissions. They have a very nice programme which they called Blue Sky because the aim was, of course, to see the blue sky, which they couldn't in many cities."

China is not alone in its efforts. "If we look across Europe and the developed world, the situation has improved a lot since the sixties or seventies," said Peuch.

In a number of cities across Europe, traffic restrictions have been implemented to reduce pollutants. According to Peuch, this kind of action is "exactly what needs to be done."


"If you cut down on the emissions of the precursor of ozone you will alleviate the problem."

Instigators of pollution spikes like sunshine and other kinds of weather are outside the realm of our control — what we can control is the source of emission.

What does the future hold for heatwaves and ozone concentrations?

"In the most likely climate projection, we expect that the frequency of heatwaves will increase and thus the potential for ozone episodes should increase," predicted Peuch.

The expert is not pessimistic about our power to redirect this projection: "If measures are efficient in reducing NO2, in reducing certain organic compounds, we can hope that the main feature of these heatwaves will be temperature."


Indeed, temperatures like those Europe experienced in June are difficult enough to cope with on their own "without having a very strong ozone component, which is what we see today."

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Video editor • Christophe Pitiot

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