Personal Exposure and Health Effect Relationship for NO₂ with Urinary Hydroxyproline to Creatinine Ratio as Indicator

Abstract

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.