The official legal body that develops and enforces occupational exposure limits (OEL) in order to ensure workplace safety and health regulations is the Occupational Health and Safety Administration (OSHA) that works under the U.S. Department of Labor. OSHA's permissible exposure limits (PELs), a guideline for occupational exposures, were adopted from the 1968 threshold limit values (TLVs) of the American Conference of Governmental Industrial Hygienists (ACGIH). Each year, the ACGIH publish their "TLV and BEI booklet" that provides updated information on "occupational exposure guidelines for more than 700 chemical substances and physical agents." The scientific literature on certain chemical and physical exposures has evolved since 1968, therefore OSHA recognizes that their PELs may not guarantee worker health and safety. The National Institute for Occupational Health and Safety (NIOSH) under the U.S. Department of Health and Human Services compensates for the rigidity of the PEL by researching "all medical, biological, engineering, chemical, and trade information relevant to the hazard" and publishing recommended exposure limits (RELs) based on their research. Therefore, as a way to ensure worker safety and health, the following sections on safety guidelines and hazard control will consider the most recent occupational exposure limits from ACGIH's "2018 TLV and BEI booklet" and NIOSH's REL.