We can argue about the extent of this contribution, and whether it was negligible, but not about if it actually happened. (Unfortunately emissions are not the

We can argue about the extent of this contribution, and whether it was negligible, but not about if it actually happened. (Unfortunately emissions are not the only culprit and a lot of particulate matter that has negative impact on overall population health in cities comes from brakes and tires but nobody figured a feasible way to deal with that yet.)