The REACH registrant needs to demonstrate safe production and use of his substance. To assess whether the substance is “safe”, the risk characterisation needs to be conducted, in which exposure estimates will be compared to DNEL (human exposure patterns) and PNECs (environmental exposure). If the quotient between exposure estimate and the DNEL/PNEC (the so called risk characterisation ratio, RCR) is below 1, a safe situation is demonstrated.
If the initial RCR is >1, further work is necessary: In most cases, e.g. when exposure modelling tools have initially been used, the exposure estimate can be reduced by using less conservative model parameters or by using higher tier (=more realistic and less conservative) models or by using actually measured data.
If, after this iterative process, even the most realistic risk characterisation of the current situation cannot demonstrate safeness, new operational or risk reduction measures, such as better localised controls or even further personal protective equipment need to be implemented and considered in the risk characterisation.