Metal content ratio as a sensitive indicator of pulmonary edema

The sensitivity to detect edema fluid in the lungs of rats exposed to 4, 2, 0.8, and 0.4 ppm O3 was estimated using the metal content ratio (Ca/Mg) and wet/dry weight ratio methods. Metal content ratios were determined by inductively coupled plasma-atomic emission spectrometer (ICP-AES). The detection limits were 0.8 and 2.0 ppm for the former and latter methods, respectively. A transitory increase of edema fluid was observed at day 1 in 0.8 and 0.4 ppm experiments by the Ca/Mg ratio method.