1. A major challenge in environmental risk assessment of pollutants is establishing a causal relationship between field exposure and community effects that integrates both structural and functional complexity within ecosystems.
2. Pollution-induced community tolerance (PICT) is a concept that evaluates whether pollutants have exerted a selection pressure on natural communities. PICT detects whether a pollutant has eliminated sensitive species from a community and thereby increased its tolerance. PICT has the potential to link assessments of the ecological and chemical status of ecosystems by providing causal analysis for effect-based monitoring of impacted field sites.
3. Using PICT measurements and microbial community endpoints in environmental assessment schemes could give more ecological relevance to the tools that are now used in environmental risk assessment. Here, we propose practical guidance and a list of research issues that should be further considered to apply the PICT concept in the field.