enter to. pinpoint a small difference in life expectancy the people in the country live a bit longer but that might be because they exercise a bit more drink less alcohol or smoke less so a range of other different factors attributing the difference to nitrogen dioxide or fine particulate matter it isn't scientific they take a statistical correlation and turn it into a causal connection without proof because on the contrary it's very easy to refute that connection. you would need to conduct tests with people exposed to high quantities of n o two and find particulate over many years to get more precise findings that's impossible for ethical reasons. points out millions of people are taking part in a kind of voluntary experiment of a similar nature. we have the example of smokers smokers inhale large quantities of nitrogen monoxide and dioxide who are talking about doses of five