ABSTRACT
This chapter reviews the crucial topic of understanding and modelling links which are subject to uncertainty and variation. Inevitably the relationship between the presence of a pollutant and the effect it has on a vulnerable subject or subject group is riddled with elements of uncertainty and variation. Pollutant–effect relationships in general comprise one area of environmental pollution where an extensive amount of work has been done. Probabilistic risk analysis is one name given to the process of assessing the effect resulting from a given level of pollution with full analysis of attendant uncertainties. An increasing amount of interest is apparent in approaches to environmental effect and impact based on use of defined subsets of a target population, termed critical groups. The notions of a critical level or a critical load are all-pervasive in the literature on the effect of pollution and on the maintenance of environmental pollution standards.
