Hydroxyproline excretion in urine of smokers and passive smokers

Urinary hydroxyproline excretion was investigated in 125 male cigarette smokers, 194 male pipe and/or cigar smokers, and 24 male nonsmokers. Hydroxyproline excretion was calculated either as hydroxyproline/creatinine ratio or as body surface-standardized amounts of hydroxyproline excreted in urine sampled during day, during night, or over 24 hr. The association of hydroxyproline excretion with smoke uptake variables such as daily cigarette consumption, carboxyhemoglobin, serum cotinine, and nicotine in urine and with self-reported passive smoking exposure in nonsmokers was analyzed. The hydroxyproline/creatinine ratio was found to be unsuitable as a measure of hydroxyproline excretion since creatinine urine concentrations correlate inversely with smoke uptake in cigarette and pipe/cigar smokers. The amount of hydroxyproline excreted in 24-hr urine and standardized for body surface was not significantly associated with smoke uptake in pipe/cigar smokers or exposure to passive smoking in nonsmokers. In cigarette smokers the situation appeared similar, although the results were less clear-cut. The data do not favor the premise that measuring urinary hydroxyproline excretion is an accurate method of investigating a lung-damaging effect of smoking, passive smoking, or air pollution.