Il Guardian riporta e commenta i risultati di una ricerca di Emissions Analytics, leader nella pubbicazione di dati sulle emissioni dei veicoli, che sembra dimostrare che l’inquinamento dovuto all’usura degli pneumatici è 1.850 volte peggiore delle emissioni di scarico dei veicoli a combustione interna. Questa ricerca tratta di emissioni di particolato, non di CO2 o altri inquinanti.
The fundamental trends that drive this ratio are: tailpipe particulate emissions are much lower on new cars, and tire wear emissions increase with vehicle mass and aggressiveness of driving style. Tailpipe emissions are falling over time, as exhaust filters become more efficient and with the prospect of extending the measurement of particulates under the potential future Euro 7 regulation, while tire wear emissions are rising as vehicles become heavier and added power and torque is placed at the driver’s disposal. On current trends, the ratio may well continue to increase.
La newsletter di Emissions Analytics si sofferma su alcuni punti importanti, quali la distribuzione delle dimensioni e la conseguente diversa permanenza nell’atmosfera di vari tipi di particolato, il diverso contenuto, che varia anche all’interno della stessa classe di particolato da usura di pneumatici, in base ai materiali che compongono il pneumatico.
An important difference between tire and tailpipe particle emissions is that most of the former is understood to go straight to soil and water, whereas most of the latter is suspended in air for a period, and therefore negatively affects air quality. This is supported by Emissions Analytics’ results, which suggest around 11% of the mass of tire emissions is smaller than 2.5 microns in diameter (defining the common metric for fine particle dust, PM2.5, which can be airborne). Therefore, the airborne tire emissions are more likely to be around 8 mg/km as shown in the table above – this is still more than 400 times higher than tailpipe emissions.
The next stage is then to take that chemical profile and study the toxicity of each. Our research so far shows that the least toxic tires are one-third as toxic as the worst – this will be the subject of a future newsletter. Therefore, tires not only vary significantly in wear rates, but also in chemical composition and toxicity. This potentially points to an effective way to drive reductions in wear and toxicity through economic incentives and regulation.