Document ID: EPA-HQ-OPP-2005-0163-0169
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-11-15T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

PREVENTION, PESTICIDES, AND

TOXIC SUBSTANCES

			PC Code:	 098301

			DB barcode: D331536

MEMORANDUM						

August 25th, 2006

Subject:	EFED Response to Public Comments for Aldicarb RED: 

	Docket ID# Opp-2005-0163-0048 

To:	Bob McNally, Branch Chief

	Ann Overstreet, Team Leader

	Sherrie Kinard, Chemical Review Manager

Special Review Branch

Reregistration Division

From:		Jonathan Angier

		Jeannette Martinez

		Donna Randall	

Environmental Risk Branch II 

Environmental Fate and Effects Division 

Through:	Dana Spatz, RAPL

Tom Bailey, Ph.D, Branch Chief, ERB II, 

Environmental Fate and Effects Division 

Attached is the completed EFED response to public comments to the most
recent Aldicarb RED (May 2005).

1) Public comments regarding lack of terrestrial incidents reported

National Cotton Council and California Cotton Growers Association
comments: “While the preliminary risk assessment predicts nearly 100%
mortality of birds and mammals for nearly all application scenarios,
there have been few documented incidences of field kills of birds and
mammals in the U.S. associated with label uses of Temik. This enormous
database based upon 35 years of actual use experience with Temik
obviously has not been seriously taken into consideration.”

EPA comments to both parties:   SEQ CHAPTER \h \r 1 Despite the lack of
great numbers of incident reports for aldicarb, avian field studies
using this pesticide definitively demonstrate potential ecological risk
following labeled application (See Section IV.A.2 of the ecological risk
assessment).  Based on the results of these field studies, it cannot be
concluded that low numbers of ecological incident reports indicate low
ecological risk.  It should be noted that there are no mammalian field
studies for aldicarb.  Additionally, there are numerous factors that may
contribute to the lack of reported incidents in the Agency’s database
and include among other the lack of a systematic or reliable reporting
mechanism (incident reporting is not required) and problems with carcass
detection.  

  SEQ CHAPTER \h \r 1 Currently, no systematic or reliable mechanism
exists for the accurate monitoring and reporting of wildlife kill
incidents to the Agency.  Moreover, before a pesticide incident can be
reported or investigated, the dead animals must first be found.  In the
absence of monitoring following pesticide applications, kills are not
likely to be noticed in agro-environments which are generally away from
human activity. Even if onlookers are present, dead wildlife species,
particularly small song birds and mammals, are easily overlooked, even
by experienced and highly motivated observers. Even in sparse vegetative
cover, wildlife carcass detection is difficult and as vegetative cover
increases the difficulty in detection is exacerbated.  Under some
circumstances intoxicated animals may seek heavy cover before dying
which decreases the probability of detection further. Poisoned birds may
fly from the sites, succumbing outside of the area or scavengers may
remove carcasses before they can be observed, significantly reducing the
chance of detection.

2) Public comment regarding granular applicators

Florida Fruit & Vegetable Association and Florida Citrus Mutual
comments: 

“All applications are made only with granular applicators that use
positive displacement metering units. The same piece of machinery that
administers the Temik also buries the granules simultaneously to a depth
of at least two inches below the soil surface to prevent offsite
movement or non-target contamination. The application is uniformly made
by spreading the granules throughout an area that is about three to four
feet wide within the dripline on both sides of the tree, and then
immediately working the granules down and into the soil. Placing the
Temik within the tree dripline reduces exposure to potential
rainfall.”

EPA comments to both parties: Placing the product within the tree
dripline does not limit exposure to rainfall, as much of the rain that
is intercepted by the tree canopy is funneled and directed toward the
tree trunk.  Thus, considerable amounts of precipitation will flow down
the tree trunk and around the base of the tree (within the dripline) as
stemflow.  

At a depth of 2 inches below the surface, there is a high probability
that some of the product will be brought back up to the surface as a
result of bioturbation, where it may then be subject to offsite
movement.  Product buried 2 inches or so below the surface cannot
realistically be considered to be entirely segregated from the surface
or completely restricted from offsite movement/non-target contamination.

EPA believes that even an initial 99% incorporation efficiency is
over-optimistic.  Although 99% efficiency may be achievable under ideal
circumstances with optimally calibrated equipment, under most field
conditions there is likely to be less efficiency due to non-ideal field
settings (e.g., soil too wet or too dry, uneven topography, natural
small-scale spatial variations in soil surface texture, crusting,
shallow hardpans, etc.), handling error, and other unforeseen
circumstances.

3) Public comment regarding Agency’s Avian Reproduction Guideline
Requirement request

Bayer Crop Science comment: With respect to the identification of avian
reproduction studies as a data gap, BCS continues to believe that
chronic studies are unnecessary for aldicarb based on the mode of action
of the chemical and the wealth of knowledge about the rapid
reversibility and recovery of animals that are sublethally exposed. The
Agency’s responses to this matter amount to saying ‘even if we
don’t know how to use the results of these studies in a risk
assessment, we still need the data because our policy is to require them
based on use pattern and persistence’. BCS believes that animal
testing should not be requested unless the data are going to be used in
a risk assessment.

EPA comment: For clarification, EPA will quote its own writing to
reiterate why BCS needs to submit bird reproduction studies.

“Although the current LD50 per square foot method does not
quantitatively calculate an RQ value, this does not preclude the need
for an avian reproduction study.  Due to the systemic nature of aldicarb
and the persistence of the equally toxic aldicarb sulfoxide in plant
tissue, ingestion of plant food items in fields treated with aldicarb is
a major chronic exposure pathway.  Therefore, registrant-submitted plant
residue studies can be utilized to estimate the potential chronic
exposure levels to birds and mammals that feed on such items in
aldicarb-treated fields (see attachment). It is understood that the
plants used in the residue studies (sugar beets, lettuce, mint) are
representative of other plants which may grow in aldicarb-treated fields
and serve as food sources for terrestrial wildlife.   Using available
residue studies, it is possible to quantitatively calculate a chronic
terrestrial organism RQ value.  

However, avian studies are still required by the Agency, whether a
quantitative RQ is calculated or not.  Knowledge of the potential for
aldicarb to cause chronic reproductive effects in birds is necessary in
order to perform a complete ecological risk assessment.  Although the
chronic mammalian data was not used to calculate an RQ value, the
results from these studies suggest the potential for deleterious chronic
effects, and this fact was discussed in the risk characterization.  The
purpose of the RQ calculation is to allow for a numerical estimation of
potential risk; inability to perform an RQ calculation does not preclude
risk, and therefore does not provide adequate grounds for waiving data
requirements.”

In conclusion, bird reproduction guideline requirements need to be
fulfilled so that the Agency can assess chronic effects to birds from a
descriptive characterization perspective. 

4) Public comment regarding Agency’s Photodegradation in Water and
Terrestrial Field Dissipation Guideline Requirement requests

Bayer Crop Science comment: “In the November 30, 2005 response to
submitted comments on the EFED RED chapter, EPA agrees that 161-2
(photodegradation in water) is unnecessary and 164-1 (terrestrial field
dissipation) has been fulfilled. Therefore these two studies should be
eliminated from the list of data requirements on page 2 of the revised
RED.”

EPA comment: These two studies have been removed from the list of data
requirements.

5) Public comment regarding incorporation efficiency used in PRZM-EXAMS
modeling

Bayer Crop Science comment: “Inspite (sic) of the Agency’s comment
that 99% incorporation efficiency was assumed in its assessment, the
PRZM-EXAMs modeling they peformed (sic) still appears to have been
conducted assuming 85% incorporation for all scenarios evaluated.”

EPA comment: Agency erred in stating that ‘All model runs were
conducted with an assigned incorporation efficiency of 99%.’  The
statement should have been application efficiency instead of
incorporation efficiency.  For these model runs, 15% of the application
rate was used; however, this 15% was distributed within the top 4 cm of
soil.  Therefore, the amount available directly on the surface was less
than 15%, but more than 1%.  The revised modeling that has been
conducted (and will be included in the updated assessment) only accounts
for 1% of the application, but all of that 1% is directly on the soil
surface (none incorporated within the top 4 cm).  Numerous other revised
model results have already been conducted, including the use of typical
rather than maximum rates.

6) Public comment regarding degradation rate used in PRZM-EXAMS modeling

Bayer Crop Science comment: “As demonstrated by the data in Jones and
Estes (1995), the degradation rate of aldicarb appears to be a strong
function of temperature and therefore, this dependence should be taken
into consideration in a refined risk assessment. While usually this
would be accomplished by normalizing the degradation rate obtained in
field studies to a common temperature and soil moisture, the large data
base for aldicarb allows the direct estimation of the degradation rate.
An examination of this data base indicates that for applications in
Mississippi, Georgia, and Florida a degradation rate corresponding to a
half-life of 15-20 days would be more appropriate than a degradation
rate corresponding to a half-life of 55 days and so a degradation rate
corresponding to a half-life of 18.25 days was used in the refined
modeling performed by BCS.”

EPA comment: Agency reiterates the statement that interregional soil
surface temperatures deviate less during the growing season than mean
annual soil temperatures would suggest (e.g., there is far less
difference in shallow soil temperatures between Minnesota and
Mississippi in July – part of the growing (and application) season –
than in January), so there should also be little deviation in
temperature-mediated aerobic degradation rates.  The agency would have
to thoroughly evaluate the “large data base for aldicarb (that) allows
the direct estimation of the degradation rate” in order to justify
using local degradation rates.  Degradation rates will also be affected
by other soil characteristics, which would have to be accounted for so
that only the effect of temperature on aerobic soil degradation could be
isolated.  Results from field studies are not adequate for this task, as
there are multiple dissipation routes at every site that will vary from
locale to locale.  The agency at present does not have sufficient cause
to apply specific local degradation rates for the purpose of modeling
the fate of aldicarb.