Urinary hydroxyproline excretion in smokers, non-smokers and passive smokers

The hydroxyproline/creatinine ratio in urine was investigated in 200 cigarette smokers, 199 pipe and/or cigar smokers and 24 non-smokers. For cigarette smokers a statistically significant positive correlation is found between this ratio and daily cigarette consumption, COHb, serum cotinine and nicotine excretion in urine. This smoking-related increase in the hydroxyproline/creatinine ratio is, for the most part or completely, due to the fact that creatinine urine concentrations inversely correlate with the smoke uptake variables. Neither pipe and/or cigar smoking nor passive smoke exposure of non-smokers seem to affect the hydroxyproline/creatinine ratio. A seasonal influence is found in these studies as well as in two experiments with limited numbers of subjects: the hydroxyproline/creatinine ratio is higher in winter than in summer for both smokers and non-smokers. Our data do not favour the idea that measuring hydroxyproline/creatinine ratios in urine is an accurate method of investigating early effects of smoking, passive smoking and air pollution in man.