Document ID: EPA-HQ-OPP-2007-0637-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-02-13T05:00Z

SEQ CHAPTER \h \r 1  

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

					

		                                                                      
                 Office of Prevention, Pesticides 

                                                                        
                      and Toxic Substances

December 14, 2007 

SUBJECT: 	1,3-Dichloropropene: Follow-up on Proposed New Use for Drip
Irrigation in Vineyards: Drinking Water and Residential Assessments; DP
Barcode: D346778, PC Code: 029001

FROM:	Christine Olinger, Chemist/Risk Assessor 

		Jeff Dawson, Risk Assessor

		Reregistration Branch 1 

		Health Effects Division (7509P)

THRU: 	Michael S. Metzger, Chief

Reregistration Branch 1					

Health Effects Division (7509P)

TO:		Cynthia Giles-Parker, Chief

		Fungicide Branch

		Registration Division (7505P)

Dow Agrosciences has proposed new uses of 1,3-dichloropropene (1,3-D)
for use in established vineyards using drip irrigation.  Registration
Division (RD) has requested further comment on the drinking water and
residential assessments included in the human health risk assessment for
the proposed new uses previously prepared by HED (C. Olinger, 6/6/07,
D340059).  Specifically, RD has raised concerns on the drinking water
assessment for the formulation contaminant 1,2-dichloropropane, as well
as the buffer zone proposed in the prior assessment.  

CONCLUSIONS AND RECOMMENDATIONS

1.	HED now recommends that the proposed buffer zone be changed from 300
ft. to 100 ft., as described in the 6/6/07 assessment.  This change
would be consistent with other 1,3-Dichloropropene labeling that is
currently used in the production of other agricultural crops with higher
application rates using similar application methods (i.e., when the
other crops are treated higher total emissions occur and the 100 ft.
buffer is sufficient for them).  No additional data are required;  the
field volatility study requested in the 6/6/07 assessment is no longer
required.

2.	1,3-Dichloropropene registrants have modified the manufacturing
process to decrease the amount of the contaminant 1,2-dichloropropane. 
It is no longer necessary to assess the drinking water exposure to
1,2-dichloropropane, as was done in the 6/6/07 assessment.  Therefore,
there are no risk concerns for 1,2-dichloropropane in drinking water.

DETAILED CONSIDERATIONS

Residential Exposure

In the proposed Section 3 label for the Cordon formulation of
1,3-dichloropropene (EPA Reg. 62719-GAG/File Cordon GAG 10Dec07d.doc) a
maximum single application rate of 2 gallons Cordon per acre is
specified (i.e., 18.8 lb ai/acre).  Additionally, a seasonal maximum
application rate per acre of 4 gallons Cordon is specified (i.e., 37.6
lb ai/acre).  One application is allowed during the growth phase of the
season and the other is required during dormancy.  As such, for
evaluation of acute bystander risks, a single application event served
as the basis.

A risk assessment was completed for the proposed use of Cordon for
vineyard treatments (i.e., D340059, 6/6/07, authors: C. Olinger & D.
Vogel) which recommended that a buffer distance of 300 feet be
established based on the sampling regimen used in a post-plant drip
application volatility study conducted in grapes (MRID 452961-01,
2/26/98, Authors:  Beard, Mueller, et al).  Particularly, the buffer
value was established because of an application scaling step required
for air modeling and because of the location of the air samplers in the
study.  In this study a total of 2.6 acres of vineyard were treated via
drip irrigation with a total of 1.56 gallons of Telone II or
approximately 15 pounds 1,3-dichloropropene.  This equates to an
approximate application rate of 5.7 pounds 1,3-dichloropropene per acre
which is markedly lower than the maximum application rate specified in
the Cordon label.  Regardless, the data from 452961-01 were used to
define emissions which were then scaled by increasing the amount of
chemical applied by 300 percent to the Cordon application rate to
develop modeling estimates for buffer zones but the uncertainty was
acknowledged in the assessment.  [Note:  Because of the scaling
involved, a confirmatory emissions study was requested in the risk
assessment to ensure the validity of the approach used for the modeling
evaluation.]  The results of this PERFUM air model analysis indicate
predicted distances of (0) meters for all situations considered (see
Table 6.1, page 34 in D340059).  In the study (MRID 452961-01) air
samplers were located 300 feet from the perimeter of the treated field. 
The empirical data were also used to calculate risk estimates, only at
the study application rate, and the resulting risks were not of concern
because the MOE was 54000 or several orders of magnitude greater than
the Agency target of 30 (see Table E-1, page 77 of D340059).

In the proposed Cordon label a buffer distance of 100 feet instead of
300 has been requested.  The Agency believes that this modification from
an initial proposal of 300 feet is appropriate and will still be
protective because of several findings.  In the assessment completed to
specifically address potential risks, even with the scaling completed
for the modeling analysis, risks were not of concern even at the edge of
the treated field and the risks calculated using the direct monitoring
data were much below (i.e., orders of magnitude) the Agency level of
concern.  To further support this label modification risks from other
drip irrigation analysis using the PERFUM air model were reviewed from
the Phase 5 Human Health Risk Assessment for 1,3-dichloropropene (i.e.,
D337328, 4/12/07, Authors Mendez & Vogel).  Table 5 of D337328 describes
3 additional drip irrigation volatility studies which were conducted at
application rates ranging from approximately 90 pounds up to 160 pounds
1,3-dichloropropene per acre.  Air samplers in these studies were
positioned approximately 100 and 300 feet from the field perimeter. 
Risks calculated based on these monitoring data, even at much higher
rates than the proposed Cordon label and approximately 100 feet from the
field edge – the proposed buffer distance, were not of concern (see
Table E-1, page 144).  Additionally, PERFUM model analyses also indicate
predicted buffer distances on (0) feet at the higher rates.  

In conclusion, a volatility study based on drip irrigation in vineyards,
which is the use pattern in the proposed Cordon label, was used to
directly evaluate risks and a PERFUM analysis was also completed based
on this study.  Both of these analyses indicated that risks were not of
concern but there is uncertainty because of the application rate in the
study and the scaling process used in the assessment.  Additionally,
risks were considered that were based on other drip irrigation
volatility studies conducted at much higher application rates that were
also not concern and predicted PERFUM buffer distances were also at (0)
feet.  When these risk estimates are considered in conjunction with each
other, the Agency believes that a buffer zone of 100 feet for the
proposed Cordon label is sufficient and that no further volatility data
are needed because the predicted risks were so far below the Agency’s
level of concern.

Drinking Water Exposure to 1,2-Dichloropropane

In the 6/6/07 human health assessment, HED assessed drinking water
exposure to the contaminant 1,2-dichloropropane from the existing
pre-plant fumigation uses, as these would lead to higher exposures than
the proposed new use of 1,3-dichloropropene.  Estimated drinking water
concentrations were obtained from the environmental fate assessment
dated 6/26/00 (S. Abel, 6/26/00; D260209 and D260210.

The Registration Division has recently provided the most recent
Confidential Statements of Formula (CSFs) for all 1,3-dichloropropene
technical products, which reflect revisions to the manufacturing
processes made several years ago.  Based on these CSFs, there is no
longer a concern for the manufacturing impurity 1,2-dichloropropene in
drinking water.

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