As industrial hygienist Dan Markiewicz writes in his “Managing Best Practices” column this month, “You can’t rely on old information. Most of OSHA’s PELs (Permissible Exposure Limits) are based on 1968 TLVs (Threshold Limit Values), with some of the TLVs developed decades earlier. You’re naïve if you only rely on PELs and TLVs for health protection and risk assessment.”