Still the levels of carbon monoxide in polluted urban atmospheres is not really that high and the levels of carboxyhemoglobin in urban non smokers is not statistically significantly different than rural non smokers. Yet if you smoke or use wood to heat your home, the levels of carbon monoxide rise quickly.
I have smoked cigars for decades and use a wood stove in my rural home—and I am still here and healthy as an ox at age 70.
Go figure....