It's pretty well established that diesel motors produce PM2.5 particles that are damaging to humans, if it's a 30 year old unit it's probably pumping it out in good quantities with little restriction. PM2.5 particulate from a diesel motor starts to irritate the lungs and eyes pretty quickly.

We've always given a pass to cars for the unpleasantness they bring into a city because we figure there's no alternative, that's just how the city runs. But there are alternatives now, and people are getting fed up with the noise, smells and pollution.

Even without the very well document health affects, cars are just shitty to be around when you're not inside one yourself, I think it's fair that we'd rather not deal with them when on foot or in your own home when possible.

If it's sufficiently old it probably doesn't produce as much PM2.5. Very old engines tend to produce larger particles. There was an unfortunate period in the development of diesel engines where the engine burnt the fuel well enough to produce very small particles and high amounts of NOx but before filters were mandatory. Of course the old engines will in put out a lot more hydrocarbon pollution which is not particularly healthy either.

That's true, and if I'm not mistaken the increase in PM2.5 particles produced is due to the emissions requirement to reduce NOx output. Balancing two negatives in a way.

That is my understanding also. There is a tradeoff between very complete combustion in a lean mixture under high pressure that produces few particulates but lots of NOx and running a rich mixture at lower temperature that produces less NOx and more particulates. Fortunately modern engines have filters both for NOx and particulates, so that neither is really a problem. At least once the car has warmed up, which in cold climates and city driving can be roughly never...

Let's all try to be a little less ignorant, starting with how diesel exhaust can affect everyone's health, dose-dependent: https://oehha.ca.gov/air/health-effects-diesel-exhaust https://www.cancer.org/cancer/cancer-causes/diesel-exhaust-a...