{OSHA definition of "working life" number of years for chronic exposure limits} "The OSH Act requires OSHA to set the standard that most adequately protects employees against harmful workplace exposures for the period of their ‘‘working life’’ (29 U.S.C. 655(b)(5)). OSHA’s longstanding policy is to define ‘‘working life’’ as constituting 45 years; thus, it assumes 45 years of exposure when evaluating the risk of material impairment to health caused by a toxic or hazardous substance."