Appendix D:  Risk Quotient Method and LOCs

The Risk Quotient Method is the means used by EFED to integrate the
results of 

exposure and ecotoxicity data. For this method, risk quotients (RQs) are
calculated by dividing exposure estimates by ecotoxicity values (i.e.,
RQ = EXPOSURE/TOXICITY), for both acute and chronic endpoints. Acute RQs
use the LD50 or LC50 as the toxicity value, and chronic RQs use the
NOAEC or NOAEL as the toxicity value.  The RQs are then compared to
OPP's levels of concern (LOCs). These LOCs are criteria used by OPP to
indicate potential risk to non-target organisms and the need to consider
regulatory action. EFED has defined LOCs for acute risk, potential
restricted use classification, and for endangered species.

An exceedence of the criteria indicate that a pesticide used as directed
has the potential to cause adverse effects on non-target organisms. LOCs
currently address the following risk presumption categories: 

		(1) acute - there is a potential for acute risk; regulatory action may
be warranted in addition to restricted use classification; 

		(2) acute restricted use - the potential for acute risk is high, but
this may be mitigated through restricted use classification 

		(3) acute endangered species - the potential for acute risk to
endangered species is high, regulatory action may be warranted, and 

		(4) chronic risk - the potential for chronic risk is high, regulatory
action may be warranted. 

Currently, EFED does not perform assessments for chronic risk to plants,
acute or chronic risks to non-target insects, or chronic risk from
granular/bait formulations to mammalian or avian species.

The ecotoxicity test values (i.e., measurement endpoints) used in the
acute and chronic risk quotients are derived from required studies
submitted by the registrant. Test values may also be derived from open
literature data included in the ECOTOX database.  Examples of
ecotoxicity values derived from short-term laboratory studies that
assess acute effects are: (1) LC50 (fish and birds), (2) LD50 (birds and
mammals), (3) EC50 (aquatic plants and aquatic invertebrates), and (4)
EC25 (terrestrial plants). Examples of toxicity test effect levels
derived from the results of long-term laboratory studies that assess
chronic effects are: (1) LOAEL (birds, fish, and aquatic invertebrates),
and (2) NOAEL (birds, fish and aquatic invertebrates). The NOAEL is
generally used as the ecotoxicity test value in assessing chronic
effects.

Risk presumptions, along with the corresponding RQs and LOCs are
summarized in Table D-1.



Table D-1: Risk Presumptions and LOCs

Risk Presumption	RQ	LOC

Birds1

	Acute Risk	EEC/LC50 or LD50/sqft or LD50/day	0.5

	Acute Restricted Use	EEC/LC50 or LD50/sqft or LD50/day (or LD50 < 50
mg/kg)	0.2

	Acute Endangered Species	EEC/LC50 or LD50/sqft or LD50/day 	0.1

	Chronic Risk	EEC/NOAEC	1

Wild Mammals1

	Acute Risk	EEC/LC50 or LD50/sqft or LD50/day	0.5

	Acute Restricted Use	EEC/LC50 or LD50/sqft or LD50/day (or LD50 < 50
mg/kg)	0.2

	Acute Endangered Species	EEC/LC50 or LD50/sqft or LD50/day 	0.1

	Chronic Risk 	EEC/NOAEC	1

Terrestrial Invertebrates (Interim)



	Acute Endangered Species	EEC/LC50	0.05

Aquatic Animals2



	Acute Risk	EEC/LC50 or EC50	0.5

	Acute Restricted Use	EEC/LC50 or EC50	0.1

	Acute Endangered Species	EEC/LC50 or EC50	0.05

	Chronic Risk	EEC/NOAEC	1

Terrestrial and Semi-Aquatic Plants 

	Acute Risk	EEC/EC25	1

	Acute Endangered Species	EEC/EC05 or NOAEC	1

Aquatic Plants2

	Acute Risk	EEC/EC50	1

	Acute Endangered Species	EEC/EC05 or NOAEC 	1

1  LD50/sqft = (mg/sqft) / (LD50 * wt. of animal)  

   LD50/day = (mg of toxicant consumed/day) / (LD50 * wt. of animal)

2  EEC = (ppm or ppb) in water

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