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

CRA

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

Little Pro on 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

Reference

Overview of ecological risk assessment - US EPA

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