OP here. Found the article on line. The point is that this was a difficult diagnosis. The guy was suffering from daily headaches for months, he attributed it to a new job with a 4 hour commute. Several doctors over those months were puzzled. Finally they asked him to stop in just after that long drive, and tests at that time indicated the problem
Point is, its not obvious that it’s the CO from the car that is causing the problem. It took months and 3 doctors (and some luck) for this guy to find the problem.
There are millions of cars with exhaust leaks. But no way to tell if you are getting poisoned except luck and a very good doctor.
PS, I did some searching to find CO poisoning cases in autos, but did not find anything.
edit: quote from article: “What probably helped save my patient’s life was his habit of driving with his window open a bit, even in cold weather.”