Integration in human eye irritation.

Today it is widely known and accepted that indoor air pollution can affect health. To ensure a healthy indoor climate through source control it is necessary to be able to predict how much of a source can be introduced into a building without unacceptable health and comfort effects. This paper describes a study of human eye irritation, which is part of a research program aimed at developing the use of sensory reference scaling in source characterization. In reference scaling the sensory eye irritation caused by exposure to polluted air is measured in terms of a concentration of a reference gas causing equivalent eye irritation intensity. The purpose of this study, therefore, was to estimate a possible difference in the magnitude of perceived sensory irritation between unilateral and bilateral exposure of human eyes. In each of four runs ten subjects were exposed to five progressive concentrations of CO2. In two of the runs the subjects were exposed unilaterally and in the other two runs the subjects were exposed bilaterally. In an analysis of variance no significant difference was found between unilateral and bilateral exposures. As expected, the intensity of the perceived irritation increased significantly with increasing exposure level. The sensitivity decreased slightly but significantly following previous exposures. These results enable us to develop a model for source characterization in which sensory eye irritation is measured by reference scaling. The use of reference scaling has the advantage that an otherwise subjective response (perceived irritation intensity) becomes less biased.