Unlike the particles or nitrogen dioxide, ozone is the only pollutant of the air whose concentrations do not diminish. The trend is global and worsens with global warming.
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Even with a mask, the French have a little better breathed in 2020. The annual report of air quality in France, published Thursday, October 14 by the Ministry of the Ecological Transition on the occasion of the National Day It is devoted to it, confirms what regional analyzes had already highlighted at the local level: the confinement has at least had a positive impact on public health. The forced stopping of the country, and in particular road traffic, led to an unprecedented decrease in nitrogen dioxide concentrations (no 2 ) and to a lesser extent of the particles (PM10 , less than 10 micrometers), one of which was planned Thursday, October 14 in Ile-de-France.
Thus, the number of agglomerations involved in exceeding regulatory thresholds for No 2 (only two, Paris and Lyon, against nine in 2019) and PM10 (none against two in 2019 ) is “the lowest ever measured”, raises the department. A fall, historical, which does not concern another pollutant, just as harmful to health: ozone. Fifty-four agglomerations were affected by ozone standards exceeding, five more than the previous year.
This “tropospheric” or “low altitude” ozone should not be confused with stratospheric ozone (the famous ozone layer) that protects us from ultraviolet rays. This “bad” ozone, which is also a greenhouse gas, is considered “the pollutant of the summer”. It is formed when the sun shines and mercury climbs. As in 2019 and 2018, the summer 2020 was marked by several peaks of ozone pollution. An episode of national magnitude occurred mainly between 6 and 12 August. It was particularly virulent in the Hauts-de-France and Ile-de-France.
One of the effects of climate change
It is one of the already perceptible effects of climate change: ozone pollution is no longer a phenomenon circumscribed to the southeastern cities of France (nor large agglomerations). It now concerns a vast front is that goes back to Lille via Lyon, Mulhouse, Strasbourg or the Paris region. Another consequence of warming, ozone peaks are becoming earlier than before April or May. To the point of soon to lose his qualifier of “pollutant of the summer”.
Unlike other pollutants (particles, no 2 but also sulfur dioxide) whose average concentrations are declining steadily – and sometimes significantly – since the beginning of the century, those in Ozone stagnate and are even up again since 2016. In Ile-de-France, they jumped by 25% in the last decade. A trend that should not improve with the overall rise in temperatures and the multiplication of heat wave episodes.
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