In the assessment and evaluation of the toxicological characteristics of a chemical, all available
information on the test substance should be considered by the testing laboratory prior to conducting
the study, in order to focus the design of the study to more efficiently test for chronic toxicity
potential and to minimize animal usage. Information that will assist in the study design includes the
identity, chemical structure, and physico-chemical properties of the test substance; any information on
the mode of action; results of any in vitro or in vivo toxicity tests; anticipated use(s) and potential for
human exposure; available (Q)SAR data and toxicological data on structurally-related substances;
available toxicokinetic data (single dose and also repeat dose kinetics where available) and data
derived from other repeated exposure studies. The determination of chronic toxicity may be carried
out after initial information on toxicity has been obtained from repeated dose 28-day and/or 90-day
toxicity tests. A phased testing approach to chronic toxicity testing should be considered as part of
the overall assessment of the potential adverse health effects of a particular chemical