Crossing the river stone by stone: approaches for residential risk assessment for consumers.

Consumer products may contain constituents that warrant a risk analysis if they raise toxicological concern. Risk assessments are performed a priori, e.g. for pesticides and biocides, and a posteriori, to diagnose risks of contaminants. An overview is presented of residential exposure assessment and risk characterization. For exposure assessment, predictive models are used to estimate exposure concentrations. The available data on product use are used to quantify the intensity of exposure. Often, both exposure concentration and product use show high variability. Worst case assessments cope with variability and uncertainty in data poor situations by selecting 'worst case' values for exposures and exposure factors. Probabilistic models may be used to quantify and model variability and uncertainty when appropriate data is available. The Margin Of Safety approach to characterize risk is discussed. Many biocides handled by consumers are used now and then and (sub)acute exposure and toxicology will be most relevant. Users and children are generally seen as critical groups during the application and post-application phases of exposure, respectively. Still, the diversity of consumer products requires consideration of the merits of each case. We conclude that residential risk assessment is still searching for methods, data and models. Probabilistic methods appear to be useful tools, but a major challenge is to integrate them in regulatory frameworks.