The "TWAp" in the lead standard

This paper analyzes current OSHA practice for adjusting the permissible exposure limit (PEL) for inorganic lead to accommodate unusual work schedules. Depending on the work schedule, the PEL adjustment procedure can allow substantially higher exposure or require substantially lower exposure, as compared to the exposure permitted by the lead standard for a normal work schedule. In addition, the procedure allows compliance with the standard by manipulation of the work schedule alone, without reduction in lead exposure. The paper describes how calculating exposure on a weekly basis using the procedure outlined in the OSHA Field Operations Manual would eliminate the seven-fold range of allowed exposure.