The purpose of this paper is to determine what types of information may be important in determining the welfare benefits of preventing toxic water contamination when a given type of toxification occurs (or is likely to occur) in a given setting. It attempts to identify information and behavior issues that need to be considered when policy makers and others wish to obtain reasonable estimates of welfare benefits and weigh them against the economic costs of removing toxins. This paper also provides reasonable "scenarios" for three toxic pollutants that are found in water bodies (surface water or groundwater). We make use of two country alternatives--one in developing countries and the other in developed countries--to demonstrate, with specific examples of arsenic, mercury and atrazine, how welfare estimates may vary when a particular behavioral/informational scenario or a particular type of chemical contamination occurs.