Narcotic effect of Carbon Monoxide (CO)

Developing of a society usually is in parity of developing more stress for the people. We have to work harder and harder, and also we affect our environment in different ways. A more developed society usually means also more thermal load, more traffic jams, more noise, more CO2, and more discomfort. People are used to say "it was better before".

There was a recent study on these factors and how they affect the human stress. One interesting point is the level of carbon monoxide (1-15 ppm), which act as narcotic for people living in the heart of the cities and reduces their stress. So, we shouldn't surprise if we see CO addicted people in the cities in line of other drugs :)