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[Effects of low concentrations of and long-term exposures to nitrogen dioxide on rat arterial blood pHa, PaCO2 and PaO2].

To determine the effects of chronic exposure to nitrogen dioxide (NO2) on arterial blood pHa, PaCO2 and PaO2, rats were exposed continuously to concentrations of 0.04, 0.12 and 0.4ppm for 6, 9 and 18 months. Heart rate (HR), respiratory rate (RR), blood hemoglobin (Hb), arterial blood pHa, PaCO2 and PaO2 were examined. The respiratory rates of rats exposed to 0.4ppm were at levels 104-106%, of those controls but this difference was not significant. Rats exposed to 0.12ppm for 6 months had significantly lower HR's, but in rats exposed to 0.4ppm NO2 for 18 months, the HR's were significantly higher than those of controls. Hemoglobin levels were identical. Arterial blood PaO2's in rats exposed to 0.4ppm NO2 for 9 or for 18 months were significantly lower than those of the controls, but the PaO2's in rats exposed to 0.12ppm NO2 for 9 or for 18 months and those of the control group were identical. From the results, it is clear that in rats hypoxemic conditions can be caused by long-term low level exposure to NO2. The relationship between NO2 concentration and exposure period can be calculated from the hypoxemic condition as well.