The War on Cars"In fact, wear and tear on tires and brakes have been shown to produce increasingly more particle pollution, by mass, than car exhaust systems did in several real-world and test scenarios. Some of the particles are large enough to see with our eyes. Others are fine particles (known as PM 2.5, with diameters up to 2.5 microns) and ultrafine particles (known as PM 0.1, with diameters of 100 nanometers), which can enter through our bloodstream and harm our organs."
KenBallweg@TheWarOnCars @seachanger this is why any large metro area I visit for long triggers my asthma. Portland OR was always a trial to visit because of this.