CRA

What Is Level of Concern (LOC) and How It Is Used in Environmental Risk Assessment

Little Pro on 2019-05-13 Views:  Update:2019-05-13

An Level of Concern (LOC) is a pre-set number (0~1) that the US EPA uses to compare with calculated risk quotient (RQ) in ecological risk assessment and to determine the level of potential risk to non-target organisms and the need for further regulatory action. Several ecological LOCs are set for different non-target organims (i.e, aquatic animals, aquatic plants). 

  • Risk Quotient (RQ) = Estimated Environmental Concentration (EEC)/Effect Endpoint (i.e, LC50, EC50, NOAEC, etc)

Level of Concerns (LOCs) for Aquatic Animals

Risk Presumption Risk Quotient (RQ) LOC
Acute High Risk Acute RQ-fish and invertebrates=Peak water concentration / Most sensitive organism LC50 or EC50 0.5
Acute Restricted Use Acute RQ-fish and invertebrates=Peak water concentration / Most sensitive organism LC50 or EC50 0.1
Acute Endangered Species Acute RQ-fish and invertebrates=Peak water concentration / Most sensitive organism LC50 or EC50 0.05
Chronic Risk

Chronic RQ-invertebrates = 21-day average water concentration / Aquatic invertebrate chronic toxicity NOAEC

Chronic RQ-fish = 56-day or 60-day average water concentration / Fish early life-stage or full life-cycle toxicity NOAEC

1.0
 

Level of Concerns (LOCs) for Aquatic Plants

Risk Presumption RQ LOC
Acute High Risk EEC/EC50 1.0
Acute Endangered Species EEC/EC05 or NOEC 1.0
 

Level of Concerns (LOCs) for Birds

Risk Presumption RQ LOC
Acute Risk EEC/LC50 or LD50/ft2 or LD50/day 0.5
Acute Restricted Use EEC/LC50 or LD50/ft2 or LD50/day or LD50 < 50 mg/kg 0.2
Acute Endangered Species EEC/LC50 or LD50/ft2 or LD50/day 0.1
Chronic Risk EEC/NOEC 1.0

Level of Concerns (LOCs) for Wild Animals

Risk Presumption RQ LOC
Acute High Risk EEC/LC50 or LD50/ft2 or LD50/day 0.5
Acute Restricted Use EEC/LC50 or LD50/ft2 or LD50/day or LD50 < 50 mg/kg 0.2
Acute Endangered Species EEC/LC50 or LD50/ft2 or LD50/day 0.1
Chronic Risk EEC/NOEC 1.0
 

More reading

How to Calculate Hazard Quotient (HQ) and Risk Quotient (RQ)

Reference

Overview of ecological risk assessment - US EPA

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