UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE  OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES

PC Code: 056502

DP Barcode: D316526

Date:  May 24, 2005     

MEMORANDUM					

SUBJECT:	Review of Public Comments on the Pentachloronitrobenzene
Revised Risk Assessments and Preliminary Risk Reduction Options (Phase 5
of Six-Phase Process)

TO:		Jill Bloom, Chemical Review Manager					

Special Review and Reregistration Division

FROM:	Cheryl A. Sutton, Ph.D., Environmental Scientist

Thomas M. Steeger, Ph.D., Senior Biologist

R. David Jones, Ph.D., Senior Agronomist	

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507c)

APPROVED	

   BY:	Elizabeth Behl, Branch Chief

ERB IV, EFED 

The Environmental Fate and Effects Division (EFED) has completed its
review of the technical registrants’ joint comments received from
Amvac Chemical Corporation and Crompton Corporation on the
Pentachloronitobenzene (PCNB) Revised Risk Assessments and Preliminary
Risk Reduction Options Phase 5.  Specifically, EFED has reviewed the
comments relevant to the environmental fate and ecological risk
assessment chapter in support of the re-registration eligibility
decision (RED) for pentachloronitrobenzene (PCNB; DP Barcode D291276). 
These comments were received as part of the Phase 5 public comment phase
of the RED process.  Additional comments received by OPP from Gustafson
LLC and the Golf Course Superintendents Association of America were
reviewed by EFED, but are not addressed in this memo as they were not
specifically applicable to the EFED chapter.

As with earlier comments made by the registrants in the error-only and
public comment phases (DP Barcode D291276), a large percentage of the
comments focused on the underlying assumptions used by EFED in modeling
surface water numbers for drinking water and ecological risk
assessments, and on the resulting conservatism associated with the
estimated surface water concentrations.  EFED estimated surface water
concentrations using standard modeling procedures and input parameter
guidance that have been subject to rigorous internal and external
quality assurance review.  These procedures and guidance are used in all
modeling done by EFED.  The screening-level process and underlying
assumptions used by EFED to estimate aquatic risks associated with the
current uses of PCNB is fully described in the Overview of the
Ecological Risk Assessment Process in Office of Pesticide Programs (OPP)
document
(http://www.epa.gov/oppfead1/endanger/consultation/ecorisk-overview.pdf)
and has been subject to review by the Federal Insecticide, Fungicide and
Rodenticide Act Scientific Advisory Panel (FIFRA SAP). 

Most of the Phase 5 comments on the environmental fate and ecological
risk assessment chapter have been addressed by EFED during previous
responses to comments phases (DP Barcode D291276; dated 7/26/2004 and
12/22/2004).  For example, the registrants continue to insist that the
submitted water monitoring data compiled by Cohen et al. (MRID
463270-01) indicate that the water modeling results are overly
conservative.  EFED has reviewed these data and determined the
monitoring to have significant deficiencies.  In general, the main
shortcomings were that the summary document did not report the search
strategy or criteria by which monitoring data were identified for
inclusion (or, conversely, were excluded from the document); date and
rate information were not clear for all studies; and insufficient
ancillary information was reported.

With regard to the registrants’ statement that the risk assessment did
not utilize a golf course adjustment factor when modeling turf, EFED
notes that the chapter did, in fact, utilize such and incorporated the
resulting drinking water concentration as a refinement for a golf course
“turf-use” scenario.  A similar refinement was conducted for the
estimated environmental concentration used in calculating aquatic risk
quotients (RQs) for PCNB use on golf courses.  These refinements were
based on the registrants’ formally stated intent to drop the use on
golf course roughs from the labels.  However, although the refinements
were included in the chapter, the RQ’s utilized to characterize risks
associated with PCNB use on turf were based on unadjusted (i.e.,
non-refined) water concentrations.  This was necessary, as the labels
allow for PCNB use on other types of turf (e.g., commercial sod farms,
residential, right-of-way, recreational) to which the golf course
adjustment factor (GCAF) is not applicable.  In such a case, the RQ’s
used in the risk estimation/characterization must be applicable to any
turf use to fully account for the risks associated with the use of the
pesticide on turf.

With regard to the registrants’ statement that the risk assessment did
not utilize a more appropriate percentage crop area (PCA) for sod farms,
EFED notes that PCA’s are currently used only for agricultural crops. 
A PCA factor is used to adjust the estimated drinking water
concentrations (EDWC’s) to take into account that a portion of a 
watershed contains fields planted with a specific crop.  However,
PCA’s have been developed for only a few agricultural crops to date,
largely limited by availability of data at the required scale;
therefore, a default PCA of 0.87 is used for the majority of
agricultural crops.  As turf uses may include golf courses, recreational
fields, parks, residential lawns, ornamental turf, some rights-of-ways,
cemeteries, etc., a PCA was not used in estimating water concentrations
associated with PCNB use on turf.  At this time, acceptable data are not
available to the Office of Pesticide Programs at the scale needed to
develop the non-agricultural equivalent of a PCA for golf course, or
other turf uses.

The registrants pointed out that in the avian seed exposure calculations
the amount of PCNB reported as the exposure of a small bird is
equivalent to a treatment of 11.3% of the seed and that this is 100
times the average treatment rate of the seeds shown in Table 10.  The
seed treatment rates reported in Table 10 of the environmental fate and
ecological effects risk assessment are based on seeding rates reported
in past assessments by OPP and which were obtained from crop profiles or
through discussions with various pesticide registrants. Maximum seeding
rates were used from various crop profiles (these profiles can be found
at http://pestdata.ncsu.edu/cropprofiles/cplist.cfm?org=crop).  When the
registrant-submitted value was higher than those found in the crop
profiles, they were used preferentially.  The maximum application rate
to seed  used in the calculations is the maximum application rate (lbs
ai/Acre) divided by the maximum seeding rate (lbs seed/Acre) reported in
Table 10.  Thus, for cotton, 0.0408 lbs a.i./A divided by 18 lbs seed/A
is equivalent to the 2265 mg a.i./Kg seed value reported in the text and
used in subsequent exposure calculations.  EFED concurs with the
registrant that the exposure value is conservative; however, it is
derived from the values reported in Table 10 and is not an error.

With regard to the comments on the potential for the atmospheric
transport of PCNB, the registrants noted that the number of detections
were limited and/or could be explained by potential PCNB use in areas
adjacent to sampling stations.  They also correctly noted that the
statement concerning “PCA” detected in the Canadian Arctic study
should have identified the compound as pentachloroanisole (PCAN), not
pentachloroaniline (PCA).  Pentachloroanisole has also, however, been
observed in several studies in the literature to form from
pentachlorophenol (PCP) that ostensibly formed from PCNB (see risk
assessment for more detail).  Regardless, EFED maintains that PCNB has
properties consistent with chemicals that have a potential for
long-range atmospheric transport.  EFED concurs with the registrant that
the data are limited; however, targeted monitoring data are not
available to substantiate the registrants’ claim, contrary to what
PCNB chemical properties suggest, that PCNB is not likely to undergo
atmospheric transport.  EFED, in reporting peak concentrations detected
rather than quantifying the number of detections relative to the number
of samples taken, was attempting to demonstrate that this mechanism of
transport will constitute a potential route of exposure for nontarget
animals distant from use sites.   

( PAGE  3 (

