Using QSARs requires expertise, firstly in order to judge which model to use for a particular substance and endpoint, and secondly in order to evaluate the level of reliability in the results.  

ECHA does not intend to produce a list of ‘approved’ models, because the value of a model depends on how it is used.  (See FAQ: ‘What makes a good QSAR model?’)  Every user of QSARs needs to be aware that QSAR models are only appropriate and reliable for specific sets of chemicals.  A highly reliable model will not produce reliable results for chemicals that lie outside the domain of applicability.  In addition, models may be suitable for different regulatory functions: risk assessment, classification and labelling or prioritisation, because each makes different demands on the model.  

QSARs have been used for decades in the development of pharmaceuticals, where a drug is to be developed to achieve a particular biological action.  Our interest here is in the reverse use, where the chemical is known, and the biological action is to be predicted.  That too has been the focus of research for decades.  But here we are concerned specifically with their use for evaluating toxicity within the regulatory framework of REACH, and it is early days.  

In practice, the use of in silico methods by European industry within REACH is still limited.  There are  three key practical issues that can delay their use.  They are highly inter-connected.