4.2 Scientific risk analysis
In the context of national and international legislation on the safety of food and animal feed, much of the thinking about assessing risk has come from the experience of developing legislation to cover potentially toxic chemicals. In this regard, the terms 'risk' and 'hazard' are particularly important. ENTRANSFOOD (European network safety assessment of genetically modified food crops) has defined the terms as follows:
Risk is defined as the likelihood that, under particular conditions of exposure, an intrinsic hazard will represent a threat to human health. Risk is thus a function of hazard and exposure. Hazard is defined as the intrinsic potential of a material to cause adverse health effects; implicit in the definition is the concept of severity and adversity of the effect.
We might think of these terms with regard to a substance like the common painkiller, paracetamol. Paracetamol has the potential to cause irreversible liver damage, and hence represents a grave hazard. However, this only occurs when the drug is taken in relatively large quantities, so we have to balance this hazard against the risk, i.e. the likelihood that an individual might accidentally or deliberately take an overdose.
Risk analysis therefore has to take into account both the relative hazard of a substance and the likely level of exposure. Determining the relative hazard of a novel substance has generally involved animal testing, i.e. giving laboratory animals a range of doses of the substance and determining the highest dose at which no adverse effects are observed - the No Observable Adverse Effect Level (NOAEL). Acceptable Daily Intakes (ADIs) are then set, often at one-hundredth of the NOAEL. Once the degree of hazard has been determined, this can be combined with information about likely exposure levels to form the overall risk assessment.