Personal exposure and health effect relationship for NO2 with urinary hydroxyproline to creatinine ratio as indicator

Establishment of an exposure-effect relationship was attempted between personal nitrogen dioxide (NO2) exposure and urinary hydroxyproline to creatinine ratio of approximately 800 adult women, who were mothers of primary schoolchildren living in two communities around Tokyo. Daily average of the personal NO2 exposure (ENO2) was measured during wintertime by a newly developed personal monitor exposed for 24 hours. The hydroxyproline to creatinine ratio (HOP:C) in the urine sample collected early in the morning of the day for ENO2 measurement was used as a biochemical indicator of the health effect of NO2 exposure. The HOP:C was found to have significant correlation with ENO2 and number of cigarettes smoked actively and passively. ENO2, however, had no correlation with the intensity of the smoking levels; they might affect HOP:C independently. Stepwise multiple regression analysis revealed that HOP:C could be predicted by ENO2 and smoking habits at a high confidence level. The regression analysis of the active smokers' group indicated that a few cigarettes was enough to increase the HOP:C, while in the case of passive smoking, HOP:C increased proportionally to the number of cigarettes.