Acceptable Exposure Limits - Indiana University of Pennsylvania可接受的暴露极限-宾州印第安那大学.ppt

Acceptable Exposure Limits …extrapolation of toxicological data to recommendations for limits for occupational exposures Development of Exposure Standards ACGIH ANSI NIOSH OSHA Threshold Limit Values (TLV’s) Published by ACGIH A time-weighted average (TWA) concentration under which most people can work consistently for 8 hours a day, day after day, with no harmful effects. 3 Categories of TLV’s TLV-TWA TLV-STEL TLV-C Biological Exposure Indices (BEI) Adopted by ACGHI Based on urine, blood, or expired air samples TWA vs. Ceiling Excursions above the TLV-TWA are permitted provided they are compensated by excursions below the TLV-TWA Amount permitted to be exceeded depends upon: Nature of contaminants Whether acute poisonings are produced from high concentrations, even for short periods Whether the effects are cumulative The frequency with which high concentrations occur The duration of the high concentration Let’s examine some TLV’s… Some TLV notations… SEN Skin PNOS Simple asphyxiant BEI A1, A2, A3, A4, A5 Notice of Intent Notice of intended changes Proposed actions of TLV’s for forthcoming year Provides opportunity for comment and solicits suggestions TLV’s- What are they? ACGIH copyrighted For occupational exposures Refer to airborne concentration Apply to NEARLY all workers Reviewed/revised regularly Guidelines for the pros TLV’s -What they are not Common denominator for safety Proof of injury Air pollution values Permanent Legal standards To be used by persons unfamiliar with them Permissible Exposure Limits (PELs) Published by OSHA Enforceable 8 hour average airborne concentration to which workers can be exposed to without suffering any adverse health effects Immediately Dangerous to Life or Health (IDLH) Action Level Calculating TWA TWA= CaTa + CbTb + … CnTn 8 Where: Ta – time of 1st exposure period during the shift Ca – concentration of contaminant in period “a” Tb – another time period during the shift Cb - the concentration during period “b” Tn –