EU Industrial Chemicals

The definition of risk characterization in terms of the TGD differs somewhat from that of the OECD/IPCS given in Section 8.1. According to the TGD (EC 2003)  

Risk characterization is Estimation of the incidence and severity of the adverse effects likely to occur in a human population or environmental compartment due to actual or predicted exposure to a substance, and may include risk estimation , i.e., the quantification of that likelihood.  

The risk characterization is carried out by quantitatively comparing the outcome of the hazard (effects assessment) to the outcome of the exposure assessment, i.e., a comparison of the NOAEL, or LOAEL, and the exposure estimate. The ratio resulting from this comparison is called the Margin of Safety (MOS) (MOS = N(L)OAEL/Exposure). This is done separately for each potentially exposed population, i.e., workers, consumers, and man exposed via the environment, and for each toxicological endpoint, i.e., acute toxicity, irritation and corrosion, sensitization, repeated dose toxicity, mutagenicity, carcinogenicity, and toxicity to reproduction. 

Unless a N/LOAEL is available from human data, the N/LOAEL are those derived from the animal studies without any modifications. When a human N/LOAEL is available, the approaches described below can stiU be used in principle but some of the factors which need to be considered when using data from animal studies will obviously not be applied. 

Where a N/LOAEL has been identified for any of the toxicological endpoints mentioned above, it will be compared with the exposure estimate for the exposed human population. Where more than one N/LOAEL has been identified for a specific endpoint, then the most relevant N/LOAEL will be used. 

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