Margin of Safety

{
  "id": "MLC-T-ENV-016522",
  "term": "Margin of Safety",
  "field": "Environment",
  "definition": "1. A required component of the TMDL that accounts for the uncertainty about the relationship between the pollutant loads and the quality of the receiving waterbody (CWA section 303(d)(1)(C)). The MOS is normally incorporated into the conservative assumptions used to develop TMDLs (generally within the calculations or models) and approved by EPA either individually or in state/EPA agreements. If the MOS needs to be larger than that which is allowed through the conservative assumptions, additional MOS can be added as a separate component of the TMDL (in this case, quantitatively, a TMDL = LC = WLA + LA + MOS).\n\n2. Maximum amount of exposure producing no measurable effect in animals (or studied humans) divided by the actual amount of human exposure in a population.\n\n3. A required component of the TMDL that accounts for the uncertainty in the response of the waterbody to loading reductions.\n\n4. An accounting of uncertainty about the relationship between pollutant loads and receiving water quality. The margin of safety can be provided implicitly through analytical assumptions or explicitly by reserving a portion of loading capacity.\n\n5. For some experts, margin of safety has the same meaning as margin of exposure, while for others, margin of safety means the margin between the reference dose and the actual exposure.\n\n6. Required component of the TMDL that accounts for the uncertainty about the relationship between the pollutant loads and the quality of the receiving waterbody (CWA section 303(d)(1)(C)). The MOS is normally incorporated into the conservative assumptions used to develop TMDLs (generally within the calculations or models)and approved by EPA either individually or in state/EPA agreements. If the MOS needs to be larger than that which is allowed through the conservative assumptions, additional MOS can be added as a separate component of the TMDL (in this case, quantitatively, a TMDL = LC = WLA + LA + MOS).",
  "abbreviation": "MOS",
  "subject": "Water",
  "references": [
    "Sediment Total Maximum Daily Loads (TMDLs) Glossary; Urban Watershed Management Research Terminology",
    "Drinking Water Technical & Legal Terms; Terms of Environment; EPA 2005b",
    "Total Maximum Daily Loads (303d) Glossary; Impaired Waters and Total Maximum Daily Loads Glossary",
    "Chesapeake Bay TMDL Glossary",
    "Exposure Factors Handbook: Glossary",
    "Urban Watershed Glossary"
  ],
  "url": "https://mlchart.com/terminology/environment/margin-of-safety/"
}