Maximum allowable limit for industrial, public, or occupied spaces in England, Japan, France, the Netherlands and Germany. 0.15 to 0.51 ppm Typical peak concentrations in American cities. 0.200 ppm Prolonged exposure of humans under occupational and experimental conditions produced no apparent ill effects. The threshold level at which nasal and throat irritation will result appears to be about 0.300 ppm. The ozone level at which some species of plant life began to show signs of ozone effects.
Foliage injury appears as dark stipples, light flecks, dead patches and general discoloration.
The ozone level at which Los Angeles, California, declares its Smog Alert No. 1. Can cause nausea and headaches in some individuals. Enhances the susceptibility to respiratory infections. 1.00 to 2.00 ppm Los Angeles, California, declares its Smog Alert No. 2 at 1.00 ppm ozone concentration and Smog Alert No. 3 at 1.500 ppm. When this range of ozone concentration was inhaled by human volunteers for 2 hours, it caused symptoms which could be tolerated without incapacitation with the symptoms subsiding after a few days.