The summer heat increases the levels of tropospheric ozone.
-Analysis-
MADRID — In summer, days are longer and people are more eager to be outside, but does that also increase environmental pollution? In truth, it's not a matter of perception: the summer heat increases the levels of tropospheric ozone, one of the polluting gases with the highest impact in Spain and across the planet.
Ozone (O3) is a colorless, odorless gas that, depending on which layer of the atmosphere it is in, can have either positive or negative effects. Stratospheric ozone is the "good" ozone, found 10 to 50 kilometers above the earth's surface. There, it forms the so-called ozone layer, which protects living beings from the sun's ultraviolet radiation. When this layer degenerates, it creates ozone holes that can contribute to global warming, as well as increase the risk of skin cancer, eye cataracts and affect people's immune system.
However, when ozone is in the troposphere — the layer of the atmosphere closest to Earth — it becomes a byproduct pollutant produced by primary pollutants such as nitrogen oxides (NO and NO2) and volatile organic compounds.
Tropospheric ozone is hazardous to our health: it affects the respiratory system, causes throat, eye and mucous membrane irritation, can trigger coughing and can reduce lung function. It makes breathing more difficult, increases cases of asthma attacks, and can worsen other chronic lung diseases such as emphysema and bronchitis. In addition, it is associated with increased deaths due to cardiovascular failure.
The people most vulnerable to high ozone exposure are children under six years old, people with pre-existing conditions such as chronic respiratory or cardiovascular problems, and the elderly. However, it is also recommended that pregnant women, oncology or polymedicated patients and immuno-compromised persons take extreme precautions when temperatures rise and, therefore, ozone levels increase.
Consequences of "bad" ozone
In addition, it also has a toxic effect on ecosystems. This type of ozone can damage forests and vegetation, impacting the photosynthesis process, thus reducing the plants' absorption of carbon dioxide and, as a result, leading to a reduction in biodiversity. It also affects agricultural yields.
There's also an increase in flights and traffic due to vacations, as well as a spike in electricity production.
Three years ago, 59% of forested areas and 6% of agricultural land was exposed to harmful levels of tropospheric ozone on mainland Europe and, in 2019, economic losses due to O3 effects on the wheat crop were estimated at €1.4 billion in 35 countries, according to European Environment Agency (EEA) data.
According to the EEA, air pollution is the biggest environmental health risk in Europe. In 2020, 96% of the EU's urban population was exposed to ambient concentrations of fine particulate matter above the WHO guideline standard of 5 micrograms per cubic meter of air. The agency estimates that poor air quality causes at least 238,000 premature deaths in the EU.
The only effective way to reduce surface ozone levels could be to eliminate or reduce its sources, i.e., reducing traffic and industrial activity.
In search of a solution
So what can be done to help? Catalonia's Climate Action Secretariat states that the only effective way to reduce surface ozone levels is to eliminate or reduce its sources, i.e., reducing traffic and industrial activity. Together with carbon dioxide and methane, ozone is one of the major greenhouse gases.
Not only does heat act as an activator of O3, but in the summer there is also an increase in flights and intercity traffic due to vacations, as well as a spike in electricity production in thermal power plants because of more air conditioning being used.
This is especially worrying considering that the world is getting hotter and heat waves will become more extreme and recurrent, as the Intergovernmental Panel on Climate Change has warned. Since the late 1970s, Earth has recorded average temperatures above the 20th-century average every year.
And just last month, the record for the hottest day ever recorded around the world was broken — three times in one week.
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