UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D. C.  20460

		

	OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES



Dec. 19, 2006

PC Code: 109901

 DP Barcode: 333607

MEMORANDUM

SUBJECT: 	EFED Revisions to the Drinking Water Exposure Assessment
(dated Aug. 31, 2005) in Support of the Triadimefon Reregistration
Eligibility Decision Document.

FROM: 	Jonathan Angier, Ph.D.

		Environmental Risk Branch 2

		Environmental Fate and Effects Division (7507C)	

		

TO:		John Pates, CRM

		Special Review and Reregistration Division

THRU:	Tom A. Bailey, Ph.D.		

		Chief, Environmental Risk Branch 2

This memo documents corrections/changes made to the triadimefon drinking
water exposure assessment, developed in support of the Reregistration
Eligibility Decision document.  It addresses registrant-proposed changes
in application rates, number of applications, and uses resulting from
risk mitigation negotiations with Bayer CropScience, and responds to
comments provided by Bayer CropScience.  For additional information,
refer to the EFED Revisions to the Ecological Risk Assessment (dated
Aug. 30, 2005) and the Drinking Water Exposure Assessment (dated Aug.
31, 2005) in Support of the Triadimefon Reregistration Eligibility
Document, dated Aug. 3, 2006.

RED/TRED Document, Page 19, Section III.A.4.b. Dietary Exposure from
Drinking Water, Surface Water Exposure: “A summary of the surface
water concentration scenarios is presented below in Table 7. For
additional information, refer to the Tier 2 Drinking Water Assessment
for Triadimefon and its Major Degradate Triadimenol, dated August 31,
2005.” 

Bayer Comment: The reference for additional information should refer to
the EFED Revisions to the Ecological Risk Assessment (dated Aug. 30,
2005) and the Drinking Water Exposure Assessment (dated Aug. 31, 2005)
in Support of the Triadimefon Reregistration Eligibility Document”,
dated Aug. 3, 2006. However, the values provided in this memorandum are
incorrect, and still represent a 3 application scenario, instead of the
correct 2 application scenario. Therefore, the memorandum, and Table 7
of the RED document must be revised to show the correct values as
provided in the following table. These values were calculated with
PRZM/EXAMS simulations, using the input parameters provided in the Tier
2 Drinking Water Assessment for Triadimefon and its Major Degradate
Triadimenol, dated August 31, 2005, but using 2 applications of 2.7 lbs
ai/A at a 14-day interval. The PE4 input and output files are enclosed. 

OLD Table 1/Table 7. Estimated Concentrations of Triadimefon and its
Degradate Triadimenol in Surface Drinking Water Using PRZM/EXAMS
Scenarios (Turf)

Use Scenario	

Portion of Golf Course- (Treated)	Acute Concentration [ppb]	

Chronic Concentration [ppb]



	

1 in 10 year annual mean (non-cancer)	30-year overall mean (cancer)



2 applications

14 day interval

2.7 lbs ai/A

(1 oz/1000 ft2)	

Entire Course	100.8	

24.94	

4.071



The chronic value of 19.633 is referenced on page 7 (Section III) of the
“Triadimefon & 

Triadimenol: Aggregate Acute, Chronic, and Short-Term Risk Assessments
Reflecting July, 2006 Risk Mitigation in Response to the Phase 4
Triadimefon RED, dated August 1, 2006, indicating that the appropriate
values were available for the risk assessments, but were not shown
correctly in the supporting documentation. Therefore, it should be
confirmed that the appropriate values were used in the dietary risk
assessment results provided in the RED document. 

NEW Table 1/Table 7. Estimated Concentrations of Triadimefon and its
Degradate Triadimenol in Surface Drinking Water Using PRZM/EXAMS
Scenarios (Turf)

Use Scenario	

Portion of Golf Course- (Treated)	Acute Concentration [ppb]	

Chronic Concentration [ppb]



	

1 in 10 year annual mean (non-cancer)	30-year overall mean (cancer)



2 applications

14 day interval

2.7 lbs ai/A

(1 oz/1000 ft2)	

Entire Course	93.5	

19.6	

9.1



EFED Response:

EFED agrees that the wrong values were included in the Memorandum of
August 3, 2006 and Table 7 of the 2006 RED/TRED.  The correct values,
representing 2 applications of 2.7 lbs ai/A with a 14-day interval, are
as cited by Bayer CropScience.  Documents (and assessments) changed to
reflect this.  HED has used all the correct values (see ‘NEW Table
1/Table 7’, above) in their assessments.

RED/TRED Document, Page 19, Section III.A.4.b. Dietary Exposure from
Drinking Water, Groundwater Exposure: “Although SciGrow should
typically over-estimate expected ground water concentrations, in this
case the model actually underestimated the monitored value in at least
one instance. A ground water monitoring study in New Jersey, which
reflected suggested turf uses, showed a peak groundwater concentration
of 25 ppb, while the SciGrow estimate for similar usage yielded an
estimate of only 5 ppb. Therefore, the potential for ground water
triadimefon contamination may be greater than supposed.” 

Bayer Comment: The representation of the 25 ppb concentration as
triadimefon and triadimenol is inappropriate. The maximum concentration
of triadimefon plus triadimenol in the New Jersey ground water
monitoring study was 6.6 ppb (0.2 ppb triadimefon, 6.4 ppb triadimenol),
and it should also be noted that these residues dissipated quickly in
the groundwater, and therefore greatly overestimate chronic
concentrations.  Also, the referenced SciGrow value should be 3.36 ppb,
not 5 ppb.

EFED Response:

EFED concurs that the correct SciGrow value for predicted groundwater
concentrations, using 2 applications of 2.7 lbs ai/A with a 14-day
interval (for turf usage), is 3.36 ppb, as referenced by Bayer
CropScience.  This correct value is listed in Table 6 of the Aug. 3,
2006 Memorandum (‘EFED Revisions to the Ecological Risk Assessment
(dated Aug. 30, 2005) and the Drinking Water Exposure Assessment (dated
Aug. 31, 2005) in Support of the Triadimefon Reregistration Eligibility
Decision Document.’).  The incorrect value of 5 ppb was only cited in
the text of the RED/TRED document.  Nevertheless, these predicted values
are less than concentrations that have been observed in some monitoring
studies.  The 25 ppb concentration cited in the 2006 RED/TRED is
considered valid; also note that the maximum value cited by Bayer
CropScience (6.6 ppb) is still higher than the SciGrow value used by
EFED.  In any event, the drinking water concentrations are predicted to
be significantly higher and thus are used to drive the EFED evaluation.

