[NO2 exposure and hydroxyproline excretion].

The determination of hydroxyproline (HOP) and of the HOP-creatinine ratio in urine, respectively, is according to the literature probably a parameter of NO2-caused collagen damage of the respiratory organs and therefore a parameter which could be used for biological monitoring of indoor exposures. Own studies on children from gas or electrical house keeping presented no significant differences. Various interpretations are discussed, further investigations seem to be indicated.