### Appendix E. The Risk Quotient Method and Levels of Concern

The risks to terrestrial and aquatic organisms are determined based on a method by which risk quotients (RQs) are compared with levels of concern (LOCs). This method provides an indication of a chemical's potential to cause an effect in the field from effects observed in laboratory studies, when used as directed. Risk quotients are expressed as the ratio of the estimated environmental concentration(EEC) to the species-specific toxicity reference value (TRV): 

# EEC RQ

# ==

Units for EEC and 

### TRV should be the same (e.g., pg/L or ppb). The RQ is compared to the LOC as part of a risk characterization. Acute and chronicLOCs for terrestrial and aquatic organisms are given in recent Agency guidance (EPA, 2004) and summarizedin 

### Table F-1 below.

For the Tier I1 aquatic assessment of spirotetramat,acute exposure is represented by the upper-bound peak EEC value and chronic exposure is represented by the 21-day and 60-day time weighted average EEC value for invertebrates and fish, respectively,calculated using PRZMEXAMS. Mammals and Birds Acute Risk" Acute RestrictedUsee Acute Listed speciesf Chronic Risk EEC~/LC,O or LD5dsqfiC or ~~~dda~~ EECILCSQ or LD5dsqft or LDsdday (or LDSQ 150mglkg) EEC/LC50 or LDsdsqft or LD~dday EEC/NOEC 0.5 0.2 0.1

1 Aquatic Animals Acute Risk Acute RestrictedUse Acute Listed Species Chronic Risk EECg/LCSo or ECso EEC/LCW or x50 EEC/LC50 or EC50 EECNOEC 0.5 0.1 0.05

1 Terrestrial Plants and Terrestrial Plants in Semi-Aquatic Areas Plants Acute Risk Acute Listed Species EECIECz5 EECECo5 or NOEC 1 1 Aquatic Plants Acute Risk Acute Listed Species aPotentialfor acutetoxicity for receptor species if RQ > LOC (EPA, 2004). b~stimated environmental concentration(ppm) on avian/mammalian food items "mg/ft2 hg oftoxicant consumed per day ePotentialfor acutetoxicity forreceptor species, even considering restricted use classification,if RQ >LOC (EPA, 2004). f~otential for acute toxicity for listed species of receptor species if RQ > LOC (EPA, 2004). gEEC=ppb or ppm in water 'EEC = lbs a.i./A EEC~WC~~ EECg/ECosorNOEC 1 1EECs used to assess acute and chronic risk to avian and mammalian species to spirotetramat were calculated using the model T-REX. Currently the Agency does not perform assessments for chronicrisk to plants or acutelchronic risks to non-target terrestrial invertebrates in screening-level risk assessments for non-endangered species. The Agency has developed an Endangered Species Protection Program to identify pesticides whose use may cause adverseimpacts on endangered and threatened species, and to implement mitigation measures that will eliminatethe adverse impacts. At present, the program is being implemented on an interim basis as described in a Federal Register notice (54 FR 27984-28008, July 3, 1989), and is providing information to pesticide users to help them protect these species on a voluntarybasis. As currently planned, the final program will call for label modifications referring to required limitations on pesticide uses, typically as depicted in county-specific bulletins or by other site-specificmechanisms as specifiedby statepartners. A final program, which may be altered from the interimprogram, will be described in a future Federal Register notice. The Agency is not imposing label modifications at this time. Rather, any requirements for product use modifications will occur in the futureunder the Endangered Species Protection Program. Limitationsin the use of spirotetramatmay be required to protect endangered and threatened species, but these limitationshave not been defined and may be formulation specific. The Agency will notify the registrants if any label modifications are necessary. Such modifications would most likely consist ofthe generic label statement referring pesticide users to use limitations contained in county Bulletins. Literature Cited U.S. EPA. 1989.U.S. Environmental Protection Agency. Endangered Species Program. Washington, DC. Federal Register: 27984-28008, July 3. U.S. EPA. 2004. U.S. Environmental Protection Agency. Overview ofthe Ecological Risk Assessment Process in the Office of PesticidePrograms,U.S. Environmental Protection Agency: Endangered and Threatened Species Effects Determinations. Office ofPrevention, Pesticide, and Toxic Substances. January 23.