Biological change resulting from an environmental alteration lasting about 10 % of the lifetime of the test organism . In practice with experimental animals, such an effect is usually identified as resulting from multiple or continuous exposures occurring over 3 months (90 days). Sometimes a subchronic effect is distinguished from a subacute effect on the basis of its lasting for a much longer time. See also: subacute effect. Related term: subchronic toxicity, subchronic toxicity test