[oil pan 4]

The DPF system stops up to 85% of particulate matter.
What gets through is too small to be seen at that quantity and too small to be smelled.
All the particulate made by emissions controlled diesels is covertly trying to get inside you.

From what I have been able to find non emissions controlled diesels do make particles of all sizes. But most of the particles are big. They are big enough to be captured by a standard paper air filter installed on the exhaust such as found on underground diesel powered mining equipment. If most of the diesel particulate was DPF sized, a lot of them would go right through a standard paper air filter.
If you have to breath the exhaust, in an underground mining environment diesels are preferred, they create very little CO compared to gas and their exhaust soot is easy to trap.

If you cant see or smell the particulate how are you going to avoid it?
When you choke on diesel smoke that is your body's way of telling you "this is bad for you".
With the 1 to 2 micron particles I guess ignorance truly is bliss, until it catches up with you a few decades later.