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 chronic LOCs for terrestrial and aquatic organisms are given in 

recent Agency guidance (EPA, 2004) and summarized in 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 Restricted Usee 

Acute Listed speciesf 

Chronic Risk 

EEC~/LC,O or LD5dsqfiC or ~~~dda~~ 

EECILCSQ or LD5dsqft or LDsdday (or LDSQ 150 mglkg) 

EEC/LC50 or LDsdsqft or LD~dday 

EEC/NOEC 

0.5 

0.2 

0.1 

1 

Aquatic Animals 

Acute Risk 

Acute Restricted Use 

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 

aPotential for acute toxicity for receptor species if RQ > LOC (EPA, 2004). 

b~stimated environmental concentration (ppm) on avian/mammalian food items 

"mg/ft2 

hg of toxicant consumed per day 

ePotential for acute toxicity for receptor 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/ECos or NOEC 

1 

1 

TEXT SEARCHABLE DOCUMENT
EECs 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 chronic risk 

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 adverse impacts on endangered and threatened species, and to implement mitigation measures 

that will eliminate the 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 voluntary basis. 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-specific mechanisms as specified by state partners. 

A final program, which may be altered from the interim program, 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 future under the Endangered Species Protection Program. 

Limitations in the use of spirotetramat may be required to protect endangered and threatened species, but 

these limitations have 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 of the 

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 of the Ecological Risk Assessment 

Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency: Endangered and 

Threatened Species Effects Determinations. Office of Prevention, Pesticide, and Toxic Substances. 

January 23.