Risk assessments serve as the foundation of regulatory decision-making on whether to take actions to reduce (or otherwise manage) a
toxicological or ecotoxicological risk or not. To understand the complex process that leads from the generation of scientiWc data, via risk
assessment to risk management decision-making, close studies of the scientiWc basis and risk assessment methods must be undertaken.
This paper consists of two main parts. In the Wrst part the principles of the European Union process for risk assessments, as deWned by
legislations and oYcial guidelines, are brieXy outlined. In the second part the actual workings of this system are exempliWed by the results
from case studies of the risk assessment processes for trichloroethylene and for acrylamide. The analysis and comparison of these two
cases illustrates: (1) that generation of a large amount of data does not ensure consensus among risk assessors, (2) that controversy can
regard diVerent levels of detail, (3) that controversy can arise at diVerent organizational and theoretical levels, (4) that risk assessments
may be subject to (public) criticism even if the experts agree, and (5) that “scientiWc” controversies have a signiWcant policy component.