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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

PREVENTION, PESTICIDES, AND

TOXIC SUBSTANCES

**PC Code: 081501**

**DP Barcode: 314394**

**Decision #: 354829**

**April 5, 2007**

**[MEMORANDUM]{.underline}**

**SUBJECT:** Response to Phase III Public Comments on the Draft
Environmental Fate and Ecological Risk Assessment Chapter in Support of
the Re-registration Eligibility Decision on Chloropicrin

**TO:** Nathan Mottl, Risk Manager Reviewer

Susan Lewis, Branch Chief

> Special Review and Reregistration Division (7508P)

**FROM:** Faruque Khan, Environmental Scientist

James Felkel, Wildlife Biologist

Environmental Risk Branch V

> Environmental Fate and Effects Division (7507P)

**Approved** Mah Shamim, Branch Chief

**By:** Environmental Risk Branch V

Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed its
review of comments from the Chloropicrin Manufactures' Task Force (CMTF)
(Data Package: EPA-HQ-OPP-2006-0661) received during the public comment
period (Phase III) on the draft environmental fate and ecological risk
assessment for chloropicrin. EFED did not receive any other comments
during the public comment period of the re-registration process of
chloropicrin. 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 chloropicrin. This
review paraphrases issues and concerns in order to efficiently address
common concerns. After comments are summarized, EFED then provides a
response to the comments. The intent of EFED's review is to address
issues regarding the underlying science/data used to estimate potential
risk to the environment from the use of chloropicrin. Comments regarding
human health and worker exposure issues will be addressed separately by
the Health Effects Division. Overall, none of the comments seem to
warrant a refinement of EFED's Environmental Fate and Ecological Risk
Assessment chapter at this time. However, the ecological incidents data
were updated in the attached Phase IV Screening Level Environmental Fate
and Ecological Risk Assessment of Chloropicrin document.

**III. ECOLOGICAL RISK ASSESSMENT**

***Aquatic exposure and Model***

***Comment:** A fundamental issue in the preliminary Ecological Risk
Assessment is the potential for substantial error introduced by improper
physical parameters that define the model. In modeling, EPA used
chemical-specific input parameters for chloropicrin and appears to have
used site specific meteorological data for the application sites. For
other than chemical-specific input values, PRZM/EXAMS modeling uses
generic scenarios created by EPA for all agricultural use pesticides.
Use of these generic values represents an important source of error
because chloropicrin is used (applied) in a manner different from
non-soil fumigant pesticides. The differences between chloropicrin
application methods and crop-use pesticide application methods do not
appear to have been taken into account in the site-specific physical
input parameters used in chloropicrin modeling.*

**Response:** As with earlier comments made by the CMTF in the
error-only comment phases (DP Barcode D305331), a large percentage of
the comments focused on the underlying assumptions used by EFED in
modeling surface water vales for ecological risk assessments and on the
resulting conservatism associated with the estimated surface water
concentrations. EFED's methods for estimated surface water
concentrations use 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 chloropicrin 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]{.underline})
and has been subject to review by the Federal Insecticide, Fungicide and
Rodenticide Act Scientific Advisory Panel (FIFRA SAP).

***Comment:** The environmental fate values EPA used in its preliminary
freshwater aquatic risk modeling had some apparent deficiencies. EFED's
selection of the aerobic soil metabolism and aerobic aquatic metabolism
values and their use in modeling erroneously overestimates the
environmental persistence of chloropicrin and its subsequent,
"predicted" ability to be mobilized into surface water. Without
evaluation of both the chemical-specific input parameters for modeling
(supplied by EPA in the preliminary risk assessment) and the
non-chemical-specific physical site parameters used by EPA, it is not
possible to establish reliability of the modeling output. The effects of
rain events on treated fields, tarped and non-tarped, are not well
established by EPA in the Risk Assessment and are not appropriately
accommodated in PRZM/EXAMS modeling.*

**Response:** The ecological risk assessment process used by OPP is
clearly defined in the overview document cited previously and the
process used to evaluate the potential risks of chloropicrin is
consistent with the Overview Document. EFED performed the PRZM/EXAMS
model using input parameter according to PRZM/EXAMS input guidance
document. EFED has acknowledged in the chloropicrin document that there
are some limitations in the PRZM/EXAMS modeling of fumigants when tarps
are used. This is captured in the uncertainties and aquatic exposure
modeling sections of the document. There are a number of uncertainties
associated with any risk assessment and to the extent possible, the
Agency attempts to delineate those uncertainties. However, just as the
CMTF has indicated that actual exposure may be lower than estimated
exposure, assessments may also underestimate exposure; that is the
nature of uncertainty. It is the mandate of the EPA to preserve and
protect human health and the environment and when attempting to do so at
a national level, OPP's approach, as outlined in the Overview Document,
is to gauge risk based on the most vulnerable areas using upper-bound
exposure values. However, even using conservative assumptions for
environmental modeling and reliance on the most sensitive tested species
may not fully account for the range of environmental conditions or
species sensitivities that may exist in areas where a pesticide may
legally be applied.

**Terrestrial exposure and model**

***Comment:** In terms of terrestrial animal exposure modeling, EFED not
only relied on modeling of off-site monitoring data (when on-site data
are available), EFED also used the model least able to incorporate
realistic meteorological conditions (ISCST3). , EFED stated that it
relied on off-site monitoring data to generate estimates of ground-level
concentrations of chloropicrin using the ISCST3 model. All of these
factors have led EPA to unrealistic results and conclusions. For a more
accurate and refined risk assessment, EFED needs to (1) use readily
available, direct measurement data taken on-site at various monitoring
heights across a broad array of application methods and/or locations (as
used by EPA's Health Effects Division in the Human Health Risk
Assessment on Chloropicrin); and/or (2) use a modeling approach more
able to realistically incorporate the effects of fluctuating
meteorological conditions; and/or (3) develop a Level of Concern
interpretive context in which to evaluate inhalation exposure risks.
EFED's current approach to modeling terrestrial animal exposure has
several compounding technical and conceptual flaws, and as such, a more
refined risk assessment is needed to properly characterize the potential
for terrestrial animal risk to chloropicrin.*

**Response:** The revised risk assessment used both deterministic and
ambient monitoring data to estimate exposures to terrestrial organisms
at the edge of treated fields which are the key concern. EFED did not
rely on off-site monitoring data to generate ground-level concentrations
of chloropicrin using the Industrial Source Complex: Short-Term Model
(ISCST3) model. The deterministic approach is based on Registrant's
field monitoring data and the use of the EPA's ISCST3 model. The basic
approaches to estimate air concentrations using ISCST3 model are
outlined in the Health Effects Division's Draft Standard Operating
Procedures (SOPs) for Estimating Bystander Risk from Inhalation Exposure
to Soil Fumigant (USEPA,2004)*.* Detailed input assumptions and model
results were described in the HED's Draft Chapter on Non-Occupational
Risks Associated with Chloropicrin (USEPA, 2005). Since defining the
ISCST3 method, EFED is working with Health Effects Division (HED) and is
considering using additional modeling (e.g. PERFUM model) that allows
for the incorporation of actual meteorological data for future
assessment.

***Comment:** Based on air monitoring data from seven studies with seven
different application methods and/or locations at a sufficiently low
sampling heights of 15, 33 and 55 cm to evaluate terrestrial animal
exposure risk, no LOCs are exceeded. The highest air concentrations of
chloropicrin were 1.470 ppm at the 15-cm height, 0.988 ppm at the 33-cm
height, and 0.565 ppm at the 55-cm height. When the highest air
concentration measured (1.470 ppm) is used along with an LC50 value of
17 ppm (as used by EFED), an RQ of 0.0865 (1.470/17) is derived, which
is below the acute risk LOC for endangered species (0.1).*

**Response:** The CMTF's calculated RQ was based on monitoring data at
60 feet away from the edge of the field. Reported RQ in the chloropicrin
chapter was based on the estimated air concentration at the edge of the
field. If RQs are calculated based on ISCTS3 estimated air concentration
values at 25 meters from the edge of the field (Table 5), they will be
comparable with CMTF's RQs, and below the acute risk LOC for endangered
species. However, EFED is concerned with ground-level residues at the
edge of fields.

**Risk Characterization**

***Comment:** Three new freshwater animal (cold-water fish, warm-water
fish, and aquatic invertebrate) acute toxicity studies have been
procured to replace the three older studies deemed supplemental by EFED.
These new studies provide different toxicity reference values with which
to evaluate freshwater animal exposure risks.*

**Response:** Once EFED receives and review these toxicity data for the
aquatic organisms, EFED will consider refining the aquatic exposure and
risk assessment.

***Comment:** The CMTF claims that birds "will flee or avoid the
treatment area when the irritation effects are first experienced"
resulting in an acute exposure that is "self-limiting with no injurious
health effects" (p. 19).*

**Response:** CMTF clearly admits that chloropicrin would be highly
irritating to wildlife. Nesting birds could experience substantial
disruption. Adults fleeing their nests could leave nestlings exposed to
heat, cold, and predators, as well as to the toxic effects of
chloropicrin.

***Comment:** The CMTF claims that because of their above avoidance
prediction, chronic exposure of wildlife will also not occur, and that
animals unable to flee will have their exposure limited by the amount of
chloropicrin treatments that could occur in their vicinity.*

**Response:** The potential for repeat and/or continuous exposure of
wildlife may be similar to that identified by HED for humans. The
exposure may not be negligible for wildlife.

**Data Requirements**

*Comment: The CMTF requests a waiver for chronic freshwater organism
studies, aquatic plant studies, terrestrial plant studies, marine
estuarine studies, and a honeybee study.*

Response: Since available information indicates that nontarget
terrestrial and aquatic animals (vertebrate and invertebrate) and
nontarget terrestrial and aquatic plants could be exposed to
chloropicrin, the previously requested studies are still needed for risk
assessment.

**Responses on deficiencies related to Submitted Fate Studies**

CMTF provided additional explanation on the deficiencies related to the
following fate studies. EFED will review the response on the
deficiencies and upgrade the following fate studies accordingly.

161-2 Aqueous photolysis (MRID# 429002-01)

162-1 Aerobic Soil Metabolism (MRID# 436139-01)

162-3 Anaerobic Soil Metabolism (MRID# 437593-01)

163-2 Laboratory Volatility (MRID# 437986-01)

164-1 Terrestrial Field Dissipation (MRID# 430851-01)

**References:**

U.S. EPA (United States Environmental Protection Agency). 2002. Guidance
for selecting input parameters in modeling the fate and transport of
pesticides. Version II. February 28, 2002.

U.S. EPA (United States Environmental Protection Agency). 2004. Health
Effects Division's Draft Standard Operating Procedures (SOPs) for
Estimating Bystander Risk from Inhalation Exposure to Soil Fumigant.

U.S. EPA (United States Environmental Protection Agency). 2005c. Human
Health Risk Assessment: Chloropicrin. U.S. Environmental Protection
Agency, Office of Pesticide Programs, Draft Report.