Document ID: EPA-HQ-OPP-2007-0350-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-05-02T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

	

OFFICE OF PREVENTION,

 PESTICIDES AND

TOXIC SUBSTANCES

				April 12, 2007

MEMORANDUM

SUBJECT:	RESPONSE TO PUBLIC COMMENTS.  The Health Effects Division’s
Response to Comments on EPA’s Phase 3 Reregistration Eligibility
Decision Document for Chloropicrin (OPP Docket# OPP-2006-0661).  DP
Barcode D305332, Chloropicrin PC Code: 081501.

FROM:	Elissa Reaves, Ph.D., Toxicologist/Risk Assessor

		Charles Smith, Environmental Scientist/Risk Assessor

Reregistration Branch II

Health Effects Division (7509P)

THRU:	Alan Nielsen, Branch Senior Scientist

		William J. Hazel, Ph.D., Branch Chief

Reregistration Branch II

Health Effects Division (7509P)

TO:		Nathan Mottl, Chemical Review Manager

		Special Review & Reregistration Division (7508P)

The attached document titled, “HED’s Response to Comments on EPA’s
Phase 3 Reregistration Eligibility Decision Document for Chloropicrin”
was generated in the post-Phase 4 period of the Proposed Public
Participation Process to address comments submitted by the Chloropicrin
Manufacturer’s Task force (CMTF), the California Department of
Pesticide Regulation (CDPR), the National Resource Defense Council
(NRDC), Beyond Pesticides, California Rural and Legal Assistance
Foundation (CRLA), and members of the general public to the Agency
following the publication of the Agency’s Phase 3 Reregistration
Eligibility Decision Document for Chloropicrin in the Federal Register
November 29, 2006.  The attached document is the Agency’s response to
those comments.TABLE OF CONTENTS

 TOC \f 

I.  Introduction	Page 3 of  11

II.  Toxicology	Page 3 of  11

III.  Occupational and Residential Exposures	Page 9 of  11

 

EPA’S RESPONSE TO COMMENTS FOR CHLOROPICRIN

I.  Introduction tc \l1 "I.  Introduction 

The following is EPA’s response to comments on the Phase 3
Reregistration Eligibility Document (RED) for chloropicrin, generated in
response to the comments submitted to the public docket by the
registrant, grower groups, consumer groups, and environmental advocacy
groups to the Agency following the publication of the Phase 3 RED on
chloropicrin in the Federal Register November 29, 2006.  Some of the
responses serve as clarification or a restatement of Agency policies and
guidance and it is hoped that this will provide a greater understanding
of the Agency’s position and procedures on these matters.  Comments
concerning the rationale behind Agency decisions, toxicology, exposure
assessment, and interpretation of available data, were submitted.

Issues related to the availability/efficacy of substitute pesticides or
the environmental fate and persistence of chloropicrin raised in the
comments and will be addressed in separate documents by the appropriate
divisions; the Biological and Economics Assessment Division (BEAD) and
the Ecological Fate and Effects Division (EFED).

II.  Toxicology tc \l1 "II.  Toxicology 

A. NRDC Comments on Chloropicrin Risk Assessment (Phase 3)

	

NRDC 1.  EPA failed to adequately adjust for scientific uncertainties
left by the human study on which the Agency relied 

Despite concerns raised both during and outside the HSRB process, the
EPA failed to make additional adjustments for adverse effects other than
eye irritation, failed to adjust for routine occupational exposures (8
hour or more per day), and failed to adjust for bystander populations
with additional uncertainty factors. Overall, EPA failed to respond
appropriately to many legitimate concerns raised by HSRB experts.

EPA Response:  The human study provides threshold eye irritation
information for the inhalation route of concern for the bystander risk
assessment. This eye irritation threshold information is not available
from the rodent toxicity database. The subjects participating in the
study are considered the most sensitive to the detection of sensory
irritants.  Protection of transient eye irritation in this sensitive
subpopulation also protects against adverse eye and respiratory
irritation.  The one hour inhalation endpoint is appropriate in the
modeling output data used for the exposure assessment.  Furthermore, the
HSRB concluded the human study was scientifically sound for the purpose
of estimating a safe level of inhalation exposure to chloropicrin. 
Therefore, phase 3 of the human study provides the appropriate point of
departure for the acute inhalation risk assessment.

NRDC 2.  EPA failed to protect bystanders from harmful exposures

EPA failed to adjust for the sensitivities of the worker and general
population, including asthmatics and others with existing pulmonary
conditions, as recommended by the HSRB. Chloropicrin, like the other
soil fumigants, has the potential to move off-site following field
applications, resulting in exposure to bystanders near treated areas and
to people far away from treated areas as it moves through the ambient
air (HED at 7, 29).  In fact, the Centers for Disease Control (CDC) and
California officials have documented chloropicrin drift problems and, in
some cases, illnesses in nearby residents. EPA states that the key
concern in this assessment was inhalation exposures to bystanders –
members of the general population who are in proximity to treated fields
and facilities.  The EPA reports that from 1993-2001, there were 36
exposure incidents reported among workers (adults and older children)
and 104 exposure incidents reported by the general population (Incidents
at 5, HED at 27-29). Although none were life-threatening, between 25%
(non-occupational) and 73% (occupational) were serious enough that the
victim was seen in a hospital health care facility (Incidents at 5). The
California Pesticide Illness Surveillance Program (1982-2002) reported a
total of 45 cases attributed to chloropicrin (Incident at 6). The EPA
incident report concludes that soil fumigation with chloropicrin in
California has resulted in widespread adverse effects to nearby
neighborhoods in 1984, 1995, and 2003 (Incident at 16, HED at 27).

EPA Response:  Information from the available incident reports indicate
that children and asthmatics respond in a similar fashion as that of
adults.  There is currently no information to suggest that asthmatics or
children would respond differently than adults.  There is, however, some
information to suggest that asthmatics may be capable of detecting
sensory irritants at lower concentrations than non-asthmatics. 
Individuals capable of detecting at lower concentrations are at less
risk of irritation since they have an earlier “warning” of chemical
exposure.  Furthermore, protection of eye irritation protects bystanders
and workers from respiratory irritation.

NRDC 3.  EPA failed to consider effects other than eye irritation

EPA failed to adjust for the sensitivities of the general population,
including asthmatics and others with existing pulmonary conditions.
Relying on the industry-sponsored human testing study, EPA
inappropriately concluded that “eye irritation is an appropriate
marker for protection of more serious respiratory outcomes” (HED at
8).  In addition, the failure by EPA to use more than a 10X factor to
adjust for differences between individuals (HED at 26) ignores sensitive
populations with pre-existing respiratory conditions such as asthma. In
fact, the HSRB, when discussing the eye irritant chemical MITC (methyl
isothiocyanate), raised the concern that the presumption that eye
irritation is more sensitive than inhalation risk is actually inaccurate
because sensitive individuals, such as asthmatics, often show a
pulmonary physiological response at significantly lower doses than
objective eye irritation (HRSB meeting, May 2-3, 2006). The adverse
effects of chloropicrin exposure are commonly known to include breathing
difficulties. Of 46 poisoning cases attributable to chloropicrin in the
California surveillance program, one included respiratory effects and
three reported a combination of eye, skin, and respiratory effects
(Incidents at 6, 7, 14). The EPA incident report concludes that symptoms
from exposure are principally lacrimation (eye tearing), throat
irritation, headache, coughing, and difficulty breathing (Incident at
16, HED at 7). The label for chloropicrin alerts treating physicians to
symptoms that include “respiratory distress.” This demonstrates the
recognized relevance of respiratory effects following exposure to
chloropicrin, particularly for sensitive populations.	

	

EPA Response:  The Agency has take into account the sensitivity of
individuals participating in the human study.  Information from the
human study suggests that protection of eye irritation protects against
respiratory irritation. The subjects participating in the human study
were of the sensitive subpopulation capable of detecting chloropicrin at
lower concentrations.  Furthermore, the physiological parameters
evaluated in phase 3 of the human study support the lack of respiratory
irritation from a one hour exposure.  Consideration has also been given
to individuals with pre-existing conditions such as asthma.  The
incidents reports do no suggest that asthmatics are responding
differently than other individuals.  As for the comparison of MITC with
chloropicrin, this comparison can not be made.  First, the mode of
action for chloropicrin is sensory irritation.  The mode of action for
MITC has not been identified and therefore should not be compared with
chloropicrin.  The human study has defined a level at which chloropicrin
may be detected in the eyes but without producing severe irritation in
the eyes, nose or tracheobronchial region of the respiratory tract. 
Finally, detecting chloropicrin at lower concentrations results in less
risk of chemical exposure. 

NRDC 4.  EPA failed to retain the FQPA factor 

EPA failed to adjust for exposure to bystander populations that include
children, pregnant women, asthmatics, and others with existing pulmonary
conditions. EPA also expected no dietary exposure to chloropicrin based
on the rapid dissipation and complete metabolism in soil and plants (HED
at 27).  Therefore, EPA determined no acute and chronic dietary
reference doses and thus found that the 10X factor provided by the Food
Quality Protection Act of 1996 does not apply (HED at 27). However, this
determination ignores the children and early life stage fetuses of
pregnant women that may be exposed as bystanders from spray drift and
other agricultural uses of chloropicrin. EPA did not require food
tolerances for chloropicrin, stating that metabolism studies in soil and
plants indicated no reasonable expectation of finite residues in raw
agriculture commodities when the chemical is applied according to label
directions (HED at 7). Because there are no food tolerances, EPA also
required no aggregate assessment be performed (HED at 7). 

EPA Response:  Although chloropicrin does not require food tolerances
and is not subject to the amendments to the Federal Food, Drug, and
Cosmetic Act (FFDCA) and the Federal Insecticide, Fungicide and
Rodenticide Act (FIFRA) promulgated under the Food Quality Protection
Act (FQPA) of 1996, consideration was given to children, pregnant women,
and others with pre-existing respiratory conditions. The rodent
inhalation database, specifically, the reproductive and developmental
inhalation studies for chloropicrin, do not suggest qualitative or
quantitative susceptibility.  The chloropicrin incidents reports do no
suggest that asthmatics or children are responding differently than
other individuals. Therefore, an additional uncertainty factor is not
warranted.

B.  California Rural Legal Assistance Foundation Comments on
Chloropicrin Risk Assessment Docket PEA-HQ-OPP-2006-0661

CRLA 1.  The proposed HECs are not Health Protective

The Benchmark approach used in the HED assessment is not transparent or
health protective.  It is troubling that the margin of exposure between
the LOAEL of 100 ppb and the acute HEC of 73 ppb is less than 1.4
especially since this LOAEL is not relevant to sensitive populations
because it is derived from a study of young adults with no history of
eye or respiratory problems.  The CRLA supports the comments of the NRDC
which detail the need for more health protective HECs that incorporate
additional uncertainty factors to compensate for the poor quality of the
toxicology data and the need to protect children and other sensitive
populations.

EPA Response:  The young adults participating in the human study are
considered to be more sensitive to the detection of sensory irritants
than older adults.  The public literature suggests that the ability of
an individual to detect sensory irritation likely decreases with age. 
Therefore, the human study provides threshold eye irritation information
in the more sensitive population.  In addition, concentrations up to 150
ppb only produced transient physiological changes in the nasal region. 
No respiratory changes (e.g., tracheobronchial) occurred at the 150 ppb
level.  Therefore, protection of transient eye irritation at 73 ppb also
protects for transient nasal irritation at 150 ppb.  The chloropicrin
incident reports do no suggest that asthmatics are responding
differently than other individuals.  Furthermore, the physiological
response of asthmatics is typically the result of inflammation of the
tracheobronchial region. Physiological parameters evaluated in the human
study suggest this region was not affected.  Therefore, the eye
irritation endpoint defined from the chloropicrin human study is health
protective of both bystanders and workers. 

CRLA 2.  Comments on Review of Chloropicrin Incident Reports

The incident review appears to be quite thorough for California
incidents between 1982 and 2002.  This review needs to be updated to
incorporate data on chloropicrin use and poisoning incidents since 2002.
 Starting in 2003, California has experienced an upsurge in poisoning
incidents which track with increased usage of chloropicrin. 

EPA Response:  The Agency acknowledges that the occurrence of the
incidents serves to demonstrate, as the HED modeling predicts, that
chloropicrin exposures to bystanders may occur following soil
treatments.  The Agency has included an updated review of chloropicrin
incidents in the Phase 5 revised risk assessment.  Please refer to
section 5.0 of the risk assessment for this updated incident review.  In
some instances, recent chloropicrin incidents occurred as a result of
doing something wrong or not at all (for example, from improper sealing
of the soil after application or failure to flush irrigation pipes).  In
other instances, it is unclear due to the lack of information available,
what the cause was of the incidents.  The incident indicate that there
have been fewer chloropicrin incidents in CA in recent years (2002 = 191
reported incidents, 2003 = 61 reported incidents, and 2004 = 1 reported
incident) not an upsurge as the CRLA claims.  This reduction in
incidents could be due to a combination of changing use patterns, state
or local regulatory changes, and/or better worker education and
outreach.  Tthe Agency does acknowledge that few states have as
stringent controls in place as California.  The fact that even in
California, incidents continue to occur confirms the need for additional
measures to reduce exposures to the public (i.e., bystanders).

C.  Beyond Pesticides Comments, Re: Chloropicrin Risk Assessments

1.  Beyond Pesticides requests EPA reject data obtained through human
testing.

The study does not meet the ethical standards prevailing at the time it
was conducted…. EPA has accepted data from a human study that caused
intentional harm to its subjects by a chemical described as “the major
toxic gas used in WWI.”  The study intentionally exposed human
subjects, using a “walk-in chamber” for two of three research
phases, to a toxic chemical, for data that offers no societal benefit,
was indeed procurable by other methods and was unnecessary.  This is
fundamentally unethical.  Beyond Pesticides continues to be extremely
alarmed that EPA has not evidenced a procedure or protocol for
evaluating the societal benefits of pesticides that are tested on humans
with results utilized in risk assessments for pesticide registration or
reregistration. In this context, chloropicrin human data violates
national and international standards.

EPA Response:  The human study with chloropicrin provides eye irritation
threshold information that is not available from rodent studies.  This
threshold information does serve to protect both bystanders and workers.
 The human study also provides irritation information in sensitive
subjects such that protecting sensitive subjects to the feel of
chloropicrin will also protect others from respiratory irritation. 
Therefore, the human study provides the most appropriate irritation
threshold information for the acute inhalation risk assessment. 
Furthermore, the HSRB reviewed the ethical considerations of the human
study and determined that the human study was both ethically conducted
and scientifically robust for estimating a safe level of inhalation
exposure. 

2.  Beyond Pesticides also requests, at a minimum, EPA restore
uncertainty factors to uncompromised levels for all scenarios.

Clearly, the rejection of the human testing data dictates that the
interspecies uncertainty factor must be reestablished to at least 10X.
We also request EPA reestablish the FQPA factor of 10X due to potential
bystander exposure. EPA did not deem the FQPA factor necessary. However,
spray drift and other agricultural uses of chloropicrin may result in
exposure of sensitive populations, such as pregnant women and children. 
In conclusion, Beyond Pesticides requests EPA reject human testing data
for chloropicrin on the grounds that the study is fundamentally
unethical, and requests EPA restore uncertainty factors to protective
levels.

EPA Response:  Although chloropicrin does not require food tolerances
and is not subject to the amendments to the Federal Food, Drug, and
Cosmetic Act (FFDCA) and the Federal Insecticide, Fungicide and
Rodenticide Act (FIFRA) promulgated under the Food Quality Protection
Act (FQPA) of 1996, consideration was given to children, pregnant women,
and others with pre-existing respiratory conditions. The rodent
inhalation database, specifically, the reproductive and developmental
inhalation studies for chloropicrin, do not suggest qualitative or
quantitative susceptibility.  The chloropicrin incidents reports do no
suggest that asthmatics or children are responding differently than
other individuals. Therefore, additional uncertainty factors are not
warranted.

D.  Comments from the Chloropicrin Manufacturers’ Task Force (CMTF)

CMTF 1. A 10X Uncertainty Factor  For Intraspecies Variability Is Not
Appropriate For The Agency’s Level Of Concern For Acute Inhalation
Exposure To Chloropicrin.

EPA Response:  The Agency has addressed the intraspecies variability
factor for chloropicrin in the Phase 5 risk assessment.  Please refer to
the uncertainty factor section of the risk assessment for further
details (Section 4.2).

CMTF 2. EPA Should Not Use Animal Toxicology Data to Establish
Short-Term

and Intermediate-Term (ST-IT) Level of Concern for Inhalation Exposure
to Chloropicrin

Human ocular sensory irritation is the most sensitive endpoint of
exposure to chloropicrin. The threshold for this effect, a mild,
transient effect, is below the NOAEL for respiratory effects seen in
rodents exposed at higher concentrations. Measures to protect
individuals from sensory irritation will also protect against
respiratory effects, which were examined for but not observed in the
human study.  Lifetime whole-body inhalation exposure of rodents to
chloropicrin vapor produced no evidence of an adverse effect at 100
ppb…. Dr. Ross has included an analysis of interspecies uncertainty in
his report. He has generated a BMCL10 for the mouse RD50 study (130 ppb)
and compared the variability associated with that data set and sensory
responses to the human subject study. Dr. Ross observes that the BMCL10
for the mouse RD50 study compares favorably with the aximum exposure
(150 ppb) employed in the human subject study. In presenting his
analysis of these data Dr. Ross points out that concordance in the
toxicocokinetics of chloropicrin in laboratory animals and humans is
strong. An interspecies UF of less than 10 therefore is inappropriate
and if an interspecies UF if used it should not be greater than 2.5.

EPA Response:  The Agency notes the rationale provided by the CMTF for
the short- and intermediate- inhalation durations for chloropicrin. 
However, the Human Studies Review Board concluded the human study was
appropriate for use in the acute inhalation assessment.  Furthermore,
the human study does not provide physiological parameters of the nasal
and upper respiratory tract beyond a one hour exposure.  The animal
database, therefore, provides the most appropriate inhalation
information for the short- and intermediate-term durations.  Therefore,
the short- and intermediate-term inhalation assessments for chloropicrin
will rely on the RfC methodology as with the other fumigants being
assessed.

III. Occupational and Residential Exposures

 tc \l1 "IV.  Occupational and Residential Exposures 

A.  Occupational Comments from the Chloropicrin Manufacturers’ Task
Force (CMTF)

CMTF 1.  The CMTF stated that the importance of soil moisture in
controlling chloropicrin emissions has been confirmed in recent studies
conducted by researchers at the USDA-ARS San Joaquin Valley Agricultural
Sciences Center, Water Management Research Unit in Parlier.  These
studies indicate that soil moisture can be effective in reducing
emissions of chloropicrin.  The CMTF believes that the mass loss values
for all flux studies in the Agency’s risk assessment should be
adjusted to reflect fields that have proper soil moisture.

EPA Response: The Agency acknowledges that soil moisture is important in
controlling chloropicrin emissions.  However, there are other
application factors (e.g., tarped vs. untarped) and environmental
factors (e.g., soil temperature) that could have an effect on
chloropicrin emissions coming off of treated fields.  The Agency
believes that the chloropicrin assessment represents a range of possible
real world application conditions and does not believe that the mass
loss values for all flux studies in the Agency’s risk assessment
should be adjusted to reflect fields that have proper soil moisture.

CMTF 2.  The CMTF stated that mass loss from drip irrigation
applications has been well studied and an emission factor of 15% of
applied from the Salinas (PRS02004) site is a conservative mass loss
value.  Instead, EPA used much higher values in it draft risk
assessment.  For the greenhouse drip irrigation method, the appropriate
“released amount” should be 15% of the applied chloropicrin.

EPA Response: The Agency has used a range of mass loss values in its
assessment of greenhouse drip irrigation applications.  This assessment
shows that generally, if less than 25% mass loss occurs then risks are
below the Agency’s level of concern at 0 meters.

CMTF 3.  The CMTF commented that there are inherent limitations to any
field air dispersion model used to predict the potential for bystander
exposure.  The relatively short exposure intervals that may be
appropriate for chloropicrin have raised concerns among modelers
regarding the limitations of the model currently being used by EPA. 
Both PERFUM, as used by EPA, and FEMS originally incorporated the ISCST3
engine; however since the Science Advisory Panel hearing on soil
fumigant modeling, the CALPUFF 6 model has been developed and both
PERFUM and FEMS have the ability to incorporate CALPUFF 6 into their
respective models.  The design of

CALPUFF 6 allows it to use less than one hour meteorological data.  It
is likely that the

incorporation of CALPUFF 6 will result in more accurate off-site
dispersion modeling.

EPA Response: The Agency agrees that there are limitations to any field
air dispersion model used to predict the potential for bystander
exposure.  The limitations associated with the Agency’s use of the
PERFUM model have been described in detail in the Phase 5 chloropicrin
risk assessment.  Also, the Agency has stated that submissions based on
FEMS, CALPUFF, or any other applicable and valid publicly available
model, would be considered by the Agency in the course of developing its
risk management decisions in context with the results of this assessment
provided sufficient supporting information were also provided in order
to document such analyses.

B.  Occupational Comments from the California Rural Legal Assistance
(CRLA) Foundation 

CRLA 1.  The CRLA Foundation commented that the length of the workday is
underestimated in the Agency’s risk assessments.

EPA Response:  The Agency acknowledges that worker exposures may exceed
the typical workday (8 hours/day) in some instances.  However, the
Agency uses an 8 hour day which is found to be a typical full day for
most agricultural worker surveys.  The use of an 8 hour workday should
be taking into context with acute results generated using high end
inputs.

CRLA 2.  The CRLA stated that respiratory protection factors are
overestimated in the Agency’s risk assessments.  The pesticide
applicator respiratory protection regulations incorporated in the Worker
Protection Standard (WPS) and California pesticide use regulations are
much less protective than OSHA respirator regulations, particularly in
the area of fit-testing of respirators to prevent leakage.

EPA Response: The Agency assumes respirator protection factors based on
the OSHA fit factors but acknowledges that there are uncertainties
because of lack of fit testing, medical monitoring, etc.

CRLA 3.  The CRLA commented that the chloropicrin risk assessment states
that dermal exposure to chloropicrin is not anticipated because handlers
are required to wear personal protective equipment.

EPA Response:  The Agency disagrees with the CRLA’s statement.  The
Agency has stated that dermal exposure resulting from typical use is not
expected.  As a result, the Agency is not conducting a quantitative
dermal risk assessment at the present time.  However, it is noted that
handlers are required by the current labels to wear personal protective
equipment (PPE) due to the corrosivity of chloropicrin to skin.

CRLA 4.  The CRLA referenced previous comments made by the Pesticide
Action Network North America (PANNA)  that stated that ISCST3 is not
capable of modeling fumigant emissions during calm atmospheric
conditions.  PANNA believes that AERMOD should be used in place of
ISCST3 as it is the only model that has undergone extensive validation
by the EPA.  PANNA states that the following new and improved algorithms
are included in AERMOD but not in ISCST3:

1) dispersion in both the convective and stable boundary layers,

2) plume rise and buoyancy,

3) plume penetration into elevated inversions,

4) treatment of elevated, near-surface, and surface level sources,

5) computation of vertical profiles of wind, turbulence, and
temperature, and

6) the treatment of receptors on all types of terrain (from the surface
up to and above the plume height.

EPA Response: The treatment of calm periods (wind speeds below 1 m/s) in
PERFUM/ISCST3 is an uncertainty in the Agency’s fumigant assessments. 
PERFUM runs the ISCST3 model in the “regulatory default option” (the
default setting for ISCST3), which includes the use of the calms
processing routine as is described in Agency guidance.  The calms
processing routine for wind speeds below 1 m/s essentially ignores any
hourly sequence in the calculations that meets this criteria.  The
Agency agrees that this approach can possibly skew results, particularly
for shorter averaging times (like metam sodium) because an analysis
period that contained several calm hours would be dominated by any
period where there was a windspeed above 1m/s.  This is a common
approach in Gaussian plume modeling.  See the U.S. Environmental
Protection Agency’s Guideline on Air Quality Models, which is
published as Appendix W to 40 CFR Part 51 1-4
(http://www.epa.gov/scram001/guidance/guide/appw_05.pdf).   

AERMOD is also a Gaussian plume model and it too has issues in dealing
with wind speeds below 1 m/s.  The new and improved algorithms included
in AERMOD have little to no effect on the Agency’s approach to
modeling fumigant applications as area sources.  In fact, preliminary
work has shown that AERMOD produces neligible differences when compared
to ISCST3 for modeling fumigant applications as area sources.

The Agency has begun to examine PUFF-based models such as CALPUFF that
have meander algorithms that can account for calm conditions by
accounting for static or near static plume conditions and representing
such events in the results.  Whether or not buffer estimates are
enhanced or under-reported as a result of this phenomenon depends upon
the nature of the weather data used for the calculations.  Preliminary
analysis in a general sense related to this issue does not indicate
significant differences when hourly calculation steps are used.  If less
than hourly steps (e.g., minute by minute calculations such as in
CALPUFF v6) are used, the effect is attenuated because the relative
percentage of calm periods in the available weather data seems to be
diminished.

C.  Occupational Comments from the California Department of Pesticide
Regulation (CDPR) 

CDPR 1.  CDPR stated that water solubility is reported inconsistently in
the Phase 3 document. 

EPA Response: The Agency has corrected the inconsistency in the Phase 5
chloropicrin risk assessment.

 See, e.g., CDC, “Brief Report: Illness Associated with Drift of
Chloropicrin Soil Fumigant into a Residential Area—Kern County,
California, 2003,” Mortality & Morbidity Weekly Report, August 20,
2004,   HYPERLINK
"http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5332a4.htm" 
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5332a4.htm ; California
Department of Pesticide Regulation, “Chloropicrin,” at   HYPERLINK
"http://www.cdpr.ca.gov/docs/dprdocs/methbrom/rafnl/attach_e.pdf" 
http://www.cdpr.ca.gov/docs/dprdocs/methbrom/rafnl/attach_e.pdf .

 Chloropicrin labels and MSDS.
http://www.arystalifescience.com/default.asp?V_DOC_ID=866

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