In the case of carbon nanotubes (CNTs), risk assessment may be rather difficult. On the one hand, CNT are supposed to have various positive properties: High stability both for lightweight components and stronger materials (e.g. for vehicle construction to save gasoline and kerosene), electrically conductive surfaces (e.g. antistatic surfaces for workplace safety, electrical switches in materials), properties modified by means of functionalisation for medical uses, and many others. On the other hand, there are indications that an increased, uncontrolled uptake into the body can have detrimental effects. Having this in view, the biological effects of CNT must be studied carefully.
Risk identification and assessment are integral parts of the so-called risk management process. A risk cannot really be handled before it has been identified and before countermeasures are available to cope with it. Hence, assessment is the most important part of that process.
The risk is evaluated as soon as it has been recognized, i.e. upon its identification by means of biological tests and after its assessment. All these steps are part of the process of risk management that is shown in the figure. In the final analysis, evaluation is required to clarify whether the risk identified is acceptable or can be accepted by society because the advantages of using the respective product weigh more heavily than the disadvantages resulting from the risk.