These filters “regenerate” automatically, approximately every 500 km, so as not to clog up. Peaks occur during this process, which can occur over a distance of 15 km.

Since the “dieselgate” and rigged engines scandal in 2015, we know that diesel vehicles are big emitters of nitrogen oxides, a very toxic gas that contributes to air pollution. They would also spit out fine particles, very dangerous for health, in large quantities, during the cleaning phase of the filter supposed to eliminate them. A study, published Monday January 13 by the European NGO Transport & Environment (T&E), shows that the most recent diesel models reject up to a thousand times more particles during this so-called regeneration phase than in normal use.

The particles emitted by diesel engines were classified as carcinogenic in 2012. For ten years, diesel vehicles must be equipped with particle filters. These are cleaned automatically, approximately every 500 kilometers, so as not to clog up. During this process, which can occur in the city and over a distance of 15 kilometers, there are peaks of particles exceeding the legal limits for particle emissions by more than 100%, notes the study.

However, the approval tests do not take into account the emissions linked to these regeneration phases. According to the NGO’s calculations, 45 million cars are fitted with filters in Europe, which corresponds to around 1.3 billion regenerations each year, or on average twenty-eight cleanings per year per vehicle.

To achieve these results, T&E called on the independent firm Ricardo, which works in particular for the European Commission. Its experts conducted laboratory tests on two particularly popular latest generation diesel vehicles: the Nissan Qashqai, the second best-selling car in Europe in 2018 in the SUV category, and the Opel Astra, the fourth most purchased vehicle among sedans.

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These two cars have been approved according to the most stringent Euro 6d-temp standard currently in force. The European limit is set at 600 billion particles per kilometer (p / km). According to tests conducted by the Ricardo firm, during the cleaning phase, the Nissan Qashqai emits 790 billion p / km and the Opel Astra 1,300 billion p / km, respectively 32% and 117% more than the norm.

“These tests show that the new diesel cars are still not clean”

Another discovery, these exceedances still increase respectively from 11% to 184% when ultra-fine particles (of the order of a nanometer) are taken into account, the most dangerous because they penetrate deep into the body, up to the brain. Ultrafine particles are not regulated and are therefore not checked during vehicle approval tests. Tests finally show that the number of particles emitted remains high thirty minutes after the end of the cleaning phase under urban driving conditions.