Risk assessment: Describing the protection provided by ambient air quality standards

Abstract

In discussing an approach to assessing the health risks that would obtain if various possible primary national ambient air quality standards were met, it is important to distinguish appropriate principles for probabilistic risk assessments from principles for the scientific research and scientific assessments on which they are based. Appropriate principles for probabilistic assessment are derived from the ultimate objective of maximizing the amount of control societal decision-making agents have in making environmental trade-offs under uncertainty about the effect of their decisions. A general methodology is presented which implements these first principles. Two general risk models are presented; a relatively simple benchmark risk model and a more complex head count risk model. These general risk models serve as a guide for the development of specific operational risk models applicable to particular ambient pollutants. Examples are given of different specific models needed for different types of pollutants. Since the scale on which a specific methodology is implemented is not determined by the methodology, the various choices involved in deciding the scale of a specific application are addressed.