On the Use of Human Judgment and Physical/Chemical Measurements in Visual Air Quality Management

Abstract

Application of existing human judgment and physical/chemical measurement techniques in developing visual air quality management programs is discussed. The measurement techniques are reviewed in terms of their abilities to provide information on several important management concerns: 1) public recognition of the problem, 2) public acceptability of different levels of visual air quality, 3) the relationship between emissions and visual air quality, and 4) trends in visual air quality. Major characteristics of measures affecting these abilities include: 1) how directly each measures visual impact, 2) the cost of achieving a desired level of reliability, and 3) the availability of a historical data base.

From this review it is concluded that different measurement techniques are needed to address different management concerns. Ratings of visual air quality made by observers in the field provide the most direct measurement of human responses to the visual environment. Surveys and tradeoff analyses are useful for assessing public recognition of the problem, quantifying public acceptability of different levels of visual air quality as measured by human judgments, and monitoring the public response to management programs. Once their relation to the human response to the visual environment has been established, measurements of emissions, pollutant concentrations, light extinction, and meteorological conditions can be used to help identify sources of visibility degradation and to provide data for determining past trends and monitoring future changes in visual air quality.