Experimental Studies on Human Health Effects of Air Pollutants

Abstract

Adult male volunteers were exposed to ozone (O₃) at 0.25, 0.37, or 0.50 ppm, and to O₃ in combination with nitrogen dioxide (NO₂) and carbon monoxide (CO), with secondary stresses of heat, intermittent light exercise, and repeated exposure.

Few important physiological changes, and only mild symptoms, were found with 0.25 ppm O₃, with 0.25 ppm O₃ plus 0.30 ppm NO₂, or when 30 ppm CO was added to the latter mixture. With 0.37 ppm O₃, more symptoms were present and some subjects developed definite decreases in pulmonary function. With 0.50 ppm O₃, most subjects had symptoms and about half showed substantial pulmonary function decrement.

In reactive subjects exposed on two successive days, changes were usually greater the second day, indicating that effects of successive exposures were cumulative.