The importance of tar and nicotine in determining cigarette smoking habits.

Cigarette consumption and inhaling, assessed using carboxyhaemoglobin levels, were studied in 1786 men to investigate the importance of tar and nicotine as determinants of smoking habits. No prior warning was given that smoking habits would be studied. Neither nicotine nor tar yields materially influenced the number of cigarettes smoked a day. Both nicotine and tar yields were negatively associated with inhaling (p less than 0.001) but after allowing for either of the two yields the effect of the other on inhaling was no longer statistically significant. There was, therefore, no indication as to whether nicotine or tar was the more important determinant of smoking habit.