There are several types of exposure limits, each serving different purposes:
Threshold Limit Values (TLVs): These are guidelines developed by the American Conference of Governmental Industrial Hygienists (ACGIH) to indicate levels under which most workers can be repeatedly exposed without adverse effects. Permissible Exposure Limits (PELs): Set by OSHA, PELs are legally enforceable limits on the amount or concentration of a substance in the air. Reference Doses (RfDs): These are estimates of daily exposure to the human population that are likely to be without risk of adverse effects during a lifetime, typically used by the EPA. Maximum Contaminant Levels (MCLs): Established under the Safe Drinking Water Act, MCLs are the highest level of a contaminant allowed in drinking water.
