Soot, car exhaust, cigar smoke, coal smoke, fly ash drift, all might cause or contribute to Crohn's disease, ulcerative colitis, irritable bowel syndrome.
When we breath that crap in, those itzy tintzy teeny little hairs in your nose tubes and lungs covered in mucus slime catch some of the diesel and coal smoke. Some of that is transported, coughed and wheezed to the throat, and yum, we swallow it. So some of the pollution we breath gets sent through the guts. We knew the heart and lung suffered, it appears they have company.
In Canada hospitals a study has been done that found more people with these three gut diseases/conditions show up on days of high pollution. It also shows people living in areas of heavy auto exhaust have these conditions at a higher rate. Either this crap is causing these issues, or is setting up a condition where the bacteria in the gut is out of kilter. This either causes, or allows the auto immune system and/or bacteria to attack the gut. Not sure yet whats going on, but the pointer is starting to drift toward air pollution as the villain in one more of the many diseases we endure because we haven't kicked the fossil fuel habit. (Yes, I know there are other reasons for these diseases besides pollution, some have a hereditary predisposition, some have a vengeful god.)
Air up your damn tires, turn off your damn lights, my wife needs your help after several years of ulcerative colitis, there's no cure for it.