The prioritisation of chemical compounds is important for the identification of those chemicals that represent the highest threat to the environment. As part of the CADASTER project (http: / /www.cadaster.eu), we developed an online web tool that allows the calculation of the environmental risk of chemical compounds from a web interface. The environmental fate of compounds in the aquatic compartment is assessed by using the SimpleBox model, while adverse effects on the aquatic compartment are assessed by the Species Sensitivity Distribution approach. The main purpose of this web tool is to exemplify the use of quantitative structure-activity relationships (QSARs) to support risk assessment. A case study of QSAR integrated risk assessment of 209 polybrominated diphenyl ethers (PBDEs) demonstrates the treatment and influence of uncertainty in the predicted physicochemical and toxicity parameters in probabilistic risk assessment.