UNITED STATES ENVIRONMENTAL PROTECT ION AGENCY 

WASH INGTON D.C., 20.t60 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

PC Code: 047802 

MEMORANDUM March 28,2016 

Subject: Addendum Memorandum Clarifying the Preliminary Environmental Fate 

and Ecological Risk Assessment Conclusions for the Registration Review 

of Propoxur 

To: 

From: 

T hrough: 

DP Barcode No.: 432548 

Brittany Pruitt, Chemi cal Rcviev,, Manager 

A viva Jakob, Team Leader 

Kelly Sherman, Branch Chief 

Risk Management and Implementation Branch HI 

Pesticide Re-Evaluation Division (750P) 

rvJ_t:!_..J..-<-4Lg' 3/3 o/ CJ..-0 I f:. Hannah Yingling, Biologist __:f)vtfl v {) 

Gabe Rothman, Environmental Scientist #~ ;{ / / 

Environmental Risk Branch V r~v-'-" -~ ..::::> .>D/ b 

Environmental Fate and Effects Division (7507P) 

Mah Shamim, Ph.D., Branch Chief 

Environmental Risk Branch V 

Environmental Fate and Effects Division (7508P) 

3/c36 jl6 

This memorandum serves as an addendum clarifying risk conclusions descri bed in the Preliminary 

Environmental Fate and Ecological Risk Assessment for the Registration Review of Propoxur 

from the Environmental Fate and Effects Division (EFED) (DP Barcode Nos. 414136, dated 

August 6, 20 14). The risk assessment identified a potential for adverse impacts to listed freshwater 

aquatic invertebrates, and therefore provided a corresponding, "May Effect" determination. These 

results were provided in both the Executive Summary (Section 1.2), Table 1.1 , the Risk 

Description Section (Section 3.2. 1), and Table 4.1 of the assessment. The risk assessment 

identi tied the highest potential for risk with current hand-held sprayer outdoor spot treatment 

insecticide uses of propoxur. Given limited information on the labels, a threshold analysis was 

conducted to identify the amount of product which would cause a concern to aquatic invertebrates, 

which was the most sensitive aquatic species informed by guideline studies submitted by the 

registrant. In the risk assessment, it was determined that 2. 75 gallons of propoxur per use site per 

year (Table 3.2) would cause potential adverse impacts to listed aq uatic invertebrates in water 
bodies occurring nearby propoxur treatments. This threshold amount of propoxur was determined 

evaluating standard pesticide runoff scenarios with pesticide treatments using the PRZM/EXAMS 

model, and reflected sparse use with one application to one property subject to runoff occurring 

within a 1 0-hectare watershed. Such use is understood to reflect actual spot treatments of propoxur 

which is not used in an organized manner within communities. Nonetheless, the risk assessment 

identified a potential for adverse effects for listed freshwater invertebrates on an acute basis with 

the threshold application amount of 2.75 gallons per year per property, and therefore provided a 

corresponding, "May Effect", determination, although acknowledging that is a very high 

application for a spot treatment (Section 3.2.1 ). It should be noted that EFED provided a, "No 

Effects" determination for all other listed aquatic and terrestrial organisms, and did not identify 

risks to non-listed freshwater invertebrates. Furthermore, no risks of concern were identified with 

other registered products of propoxur uses outdoors including bait stations, spray cans, and its 

impregnated insecticide tag and tape strip products. 

Since the risk assessment, additional information on propoxur spot treatments were provided by 

the Biological and Economic Analysis Division (BEAD). BEAD estimates that outdoor spot 

treatments ofpropoxur would not exceed one gallon per property per year (BEAD Product Review 

Panel Document, dated March 23, 20 16). The rationale on propoxur spot treatment use in the 

BEAD document provides strong evidence that propoxur is not commonly used at quantities even 

nearly approaching 2. 75 gallons. Therefore, EFED provides a definitive, "No Effects" 

determination for freshwater aquatic invertebrates in this risk assessment addendum 

clarification memorandum. This determination supersedes the, "May Effect" risk determination 

for listed freshwater aquatic invertebrates presented in the Executive Sununary (Section 1.2), 

Table 1.1 , the Risk Description Section (Section 3.2. 1 ), and Table 4.1 . 

Please address any questions to Gabe Rollm1an at (703) 347- 80 II or 1-fannah Yingling at (703) 

347 -0297. 

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