Broad host range type

The EMTD is determined on the basis of a subchronic toxicity study in which small groups of test animals are exposed to a fairly broad dose range of the test substance for a period of approximately 10% of the life span of the animals (90 days for rodents). In turn, the dose levels which are tested in the 90 day subchronic study are themselves based on information generated in acute toxicity studies of the type described in the preceeding chapter. In addition to providing the EMTD the acute and subchronic tests also are utilized to obtain information on the metabolism of the test substance, the extent to which the test substance and its metabolites are distributed and bioaccumulated in the host, and which host organ systems may be affected by exposure. This information may be of importance in choosing the species or strains to be used in the chronic study as well as the route of administration. 

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