Document ID: EPA-HQ-OPP-2005-0266-0019
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-07-27T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

Office of Prevention

Pesticides and

Toxic Substances

								PC Code: 044301

DP Barcode: 310547

Date: February 10, 2006

MEMORANDUM

SUBJECT:	Review of the 60-day Public Comments on the Level 1 Screening
Ecological Risk Assessment for the Reregistration of Dodine

TO:	Cathryn O’Connell, Chemical Review Manager

	Tom Myers, Risk Manager

	Special Review and Reregistration Division

FROM:	Marietta Echeverria, Environmental Scientist

	Environmental Risk Branch IV

	Environmental Fate and Effects Division 

THROUGH:	Elizabeth Behl, Branch Chief

	Environmental Risk Branch IV

	Environmental Fate and Effects Division 

	The Environmental Fate and Effects Division (EFED) has completed review
of public comments received from the technical registrants,
Chimac-Agriphar S.A., on the ecological risk assessment in support of
the reregistration eligibility decision (RED) for dodine. 	The comments,
in full, can be found in the registrants letter (Chimac-Agriphar; dated
January 17, 2006).  

	In summary, the registrants reiterate their objection to the calculated
aerobic aquatic metabolism half-lives used in the risk assessment for
dodine (MRID 46438202).  Specifically, the registrants object to the
fact that nonextractable residues were considered non-degraded parent
dodine in the half-life calculations.  The extractions in the study were
performed with methanol, dichloromethane and hexane.   In addition, for
one sample of each sediment type, a Soxhlet extraction was also
performed.  The registrants believe “…that based on the results of
the given “harsh” extraction methods, only half or less of the bound
residues is non-degradable and could be available as parent Dodine under
a worst case scenario.”

	The registrants also point out a significant difference in their
calculated half-lives from those reported by the Agency.  The
registrants suggest that the difference is probably due to the fact that
the Agency used a log/linear model to calculate the half-lives versus
the approach they used with “Model Manager” (model not specified).  

 EFED Response:  

As reported in Appendix B of the risk assessment and in the response to
“error-only comments”, the sediment extraction method in the aerobic
aquatic metabolism study (MRID 46438202) consisted of organic solvents
(methanol/dichloromethane/ n-hexane) and resulted in a substantial
proportion of nonextractable residues.   In the two systems,
nonextractable [14C] residues were a maximum of 57.7% and 33.4% of the
applied at 1 day and were 33.4% and 13.8% at 84 days. The acid/base
extraction method (KOH in methanol/ HCl in methanol) used in the aerobic
soil metabolism study (MRID 4394520) and the aerobic aquatic metabolism
study for DGH (MRIDs 42327401, 42414601) was more efficient at
extracting residues.  In the aerobic soil metabolism study (MRID
4394520), nonextractable residues peaked at 10.8% and 11.4% at day 10 in
both soils and decreased to 2.7% and 2.9%  at the conclusion of the
study (day 100).  In the aerobic aquatic metabolism study for DGH,
nonextractable residues averaged 5.3% at the conclusion of the study
(day 30).  

Given the noted differences in the amount of nonextractable residues
reported from the two extraction techniques, EFED assumed that the
nonextractable residues in the aerobic aquatic metabolism were
non-degraded parent dodine.  This approach is consistent with the level
of assessment that was being conducted (i.e., Level I Screening Risk
Assessment).  EFED agrees that this is a conservative approach and is
likely to result in an overestimation of environmental exposure
concentrations of longer-term duration (chronic).  For peak
concentrations (acute) as modeled with PRZM/EXAMS, however, the
conservative input for aerobic aquatic metabolism is not expected to
have a large effect since peak concentrations are calculated from peak
loading events prior to degradation in the water body.  The
registrants’ assertion that only “half or less” of the bound
residues should be considered non-degraded parent dodine as a worse case
scenario is not supported by data.      

	EFED agrees that the differences in their calculated half-lives and
those reported by the Agency are probably due to the different models
used in the calculations.  

 PAGE   

 PAGE   1