Can diesel engines CLEAN urban air?

The Emissions Analytics report opens the diesel discussion, saying “the truth is that they have emitted very few particles, at least in relative terms, since the broad introduction of diesel particulate filters a decade ago”. To test the theory, it worked with Auto Motor und Sport using four recent diesel models. Going to the extreme, they opened canisters of high intensity particles in front of the air intake on the cars as they idled for an hour. In contrast, the particle concentration measured at the rear, near the exhaust, remained flat, even dropping to around 10,000 cm3 towards the end. Exhaust particles were measured from cold, neutral warm idle, under heavy load, and during DPF regeneration. Emissions Analytics clarifies, that it would be a broad stroke to say that diesel engines clean the air. This is purely a measurement of particulates, and ignores nitrogen oxides and other gaseous emissions.  It’s also worth considering that many diesels still on the road are pre-DPF models.