Document ID: EPA-HQ-OPP-2004-0202-0196
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-11-13T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

	WASHINGTON, D.C.  20460

	

OFFICE OF PREVENTION,

 PESTICIDES AND

TOXIC SUBSTANCES

				May 26, 2005

MEMORANDUM

SUBJECT:	RESPONSE TO PUBLIC COMMENTS.  The Health Effects Division’s
Response to Comments on EPA’s 2nd Revised HED Chapter (DP Barcode
D312691) of the Reregistration Eligibility Decision Document (RED). 
February 3, 2005.  PC Code: 056502, DP Barcode D316525.

FROM:	Diana Locke, Ph.D.

Risk Assessor/Toxicologist

Reregistration Branch II

Health Effects Division (7509C)

THRU:	Alan Nielsen, Branch Senior Scientist					

Reregistration Branch II

Health Effects Division (7509C)

TO:		Jill Bloom

Reregistration Branch II

Special Review and Reregistration Division (7508W)

The attached document titled, “HED’s Response to Comments for
PCNB,” was generated in Phase 5 of the Proposed Public Participation
Process (FR Notice 03/15/00) to address comments submitted by the
Crompton Manufacturing Company and Amvac Chemical Corporation, Gustafson
LLC, Cleary Chemical Corporation and Arvesta Corp., the Golf Course
Superintendents Association of America (GCSAA), and other stakeholders,
to the Agency following the publication of the Agency’s Health Effects
Division’s (HED) chapter of the Reregistration Eligibility Document
(RED) in the Federal Register 02/03/05.  The attached document is the
HED’s response to those comments.  This response includes input from
Sherrie Kinard (Residue and Product Chemistry, and Dietary Assessment),
Laurence Chitlik (Toxicology), Sayed Tadayon (Occupational and
Residential Exposure), and Diana Locke (Risk Assessment).

cc:	Tina Levine

Debbie Edwards

Margaret Rice

William Hazel

	TABLE OF CONTENTS

 TOC \f 

I.  Introduction	Page 4 of 13

II.  Risk Assessment	Page 4 of 13

III.  Residue Chemistry	Page 4 of 13

IV.  Toxicity	Page 5 of 13

V.  Occupational and Residential Exposure	Page 7 of 13

Residential and Non-Occupational Postapplication Risk	Page 7 of 13

Occupational Handler Risk	Page 9 of 13

Seed-handler Risk	Page 13 of 13

 

May 26, 2005

	HED’S RESPONSE TO COMMENTS FOR PCNB

I.  Introduction tc \l1 "I.  Introduction 

The following is HED’s response to comments on the RED for PCNB,
generated to address comments submitted to the public docket by the
registrants (Gustafson, Crompton, Amvac), GCSAA, and other stakeholders
in Phase 5 of the Proposed Public Participation Process.  Some of the
responses serve as clarification or a restatement of HED policies and
guidance and it is hoped that this will provide a greater understanding
of HED’s position and procedures on these matters.  Many of the
comments were addressed during the previous phase and HED’s responses
can be found in RESPONSE TO PUBLIC COMMENTS.  The Health Effects
Division’s Response to Comments on EPA’s HED Chapter of the PCNB
Reregistration Eligibility Document (07/27/04).  PC Code: 056502, DP
Barcode D312692.  Diana Locke.  February 3, 2005.  Since there were a
number of comments submitted from very differing sources, HED’s
responses will be directed to the issues raised and not to each of the
commentors.  In many cases, the same subject matter was raised by more
than one of the commentors but with different view points.

Several issues related to the environmental fate of PCNB, the generation
of drinking water estimates, and alternative pesticides to PCNB use were
raised in the comments and will be addressed in separate documents by
the appropriate divisions; the Biological and Economics Assessment
Division (BEAD), Special Review and Reregistration Division (SRRD), and
the Ecological Fate and Effects Division (EFED).

II.  Risk Assessment tc \l1 "II.  Risk Assessment 

As mentioned above, HED has addressed a number of the submitted comments
before (02/03/05).  Rather than reiterate previous responses, the reader
is directed to the February 2005 Response to Comments.  Where new issues
have been raised, or issues are in need of clarification, HED has
provided the appropriate responses within.

None of the comments submitted in this phase were not compelling enough
to make a substantial, if any, change in the quantitative risk
assessment of February 3, 2005, nor do they change the data needs, or
need for mitigation. 

III.  Residue Chemistry tc \l1 "III.  Residue Chemistry 

Comment:  The Agency’s risk assessment incorrectly states that
Crompton Corporation is not supporting the seed treatment use pattern
and has no labels.  Background – Crompton (then Uniroyal) responded on
May 1, 1987 to an earlier PCNB Registration Standard committing to
conduct radiotracer studies using 14C PCNB on corn, peas, sugar beets,
wheat and soybeans.  That data was submitted to EPA on January 20, 1989.
 The Agency was told at that time we would not support the rice or
safflower.  These studies were conducted to support the seed treatment
use patterns.  In addition, Crompton also conducted seed treatment
magnitude of the residue studies on barley, soybeans, sugar beets, peas,
corn, and wheat.  Those data were submitted on February 20, 1991.  At
the SMART meeting held on July 18, 2001, we again communicated our
continued support of the seed treatment uses.  A table of the current
Crompton and Gustafson seed treatment labels containing PCNB, which was
provided at the SMART meeting, is attached (Attachment B).  As you can
see, the “dormant” label, EPA Reg. No. 400-510, is registered for
most of the seed treatment uses.  Gustafson has historically been
Crompton’s seed treatment-marketing arm in the US.  The Agency should
initiate the establishment of permanent tolerances to cover the
registered PCNB seed treatment uses.  Data developed by Crompton
(Uniroyal) for the seed treatment use patterns is summarized in
Attachment C.  We propose that the agency establish tolerances at 0.02
to 0.05 ppm based on the summation of the levels of detection of PCNB,
PCA, PCB and MPCPS.

Response:  HED recommends the establishment of a tolerance of 0.02 ppm
for soybean seed (see Revised PCNB Residue Chemistry Chapter by S.
Kinard, D291280. December 14, 2004).  The additional seed treatment data
(MRID#s 41792601, 41792605, 41792604, 41792602, 41792603, and 41792606)
are currently under review.  Once the data have been reviewed and deemed
acceptable for tolerance setting purposes, seed tolerances for barley,
corn, oat, pea, sorghum, sugarbeet, and wheat will be recommended.

Comment:  Total Toxic Residues.  It seems overly conservative to assume
that all the 84 residues are as toxic or as bioavailable as PCNB when
some are conjugated (normally less toxic), they are all present at low
levels, and they require strong acids or bases before they are
‘biologically’ available.

Response:  HED maintains that due to insufficient toxicity data for the
metabolites of PCNB, and due to the polychlorinated nature of the PCNB
metabolites, these metabolites cannot be ruled out as being toxic unless
proven otherwise through suitable toxicity data which may be generated
by the registrants.  HED also maintains that the general non-toxicity of
polar metabolites cannot be extended to include each and every instance,
particularly when 1) data on the toxicity of those metabolites are
lacking, and 2) the uncertainty with such generalization puts the health
of the general public at risk.  As there is a likelihood of release of
conjugated and bound metabolites, such compounds cannot also be
dismissed unless proven to be of low toxicity through suitable toxicity
data.

IV.  Toxicity tc \l1 "IV.  Toxicity 

Comment: On  page 1 of their general comments (submission on 05/02/05),
AMVAC/Crompton  noted that the “Application of the 10X FQPA
uncertainty factor” was one of the overarching issues on which all
mitigation options are dependent.  On page 2 of their submission, they
indicated, relative to the  FQPA Uncertainty Factor, that “A complete
toxicological database exists for PCNB and there exists no evidence that
pups are more susceptible than adults.  Under these circumstances,
application of a 1X factor is appropriate.”   The submission also
raises this same issue in the second paragraph on page 17 of their
submission.  

Response:  The Agency does not concur with the registrants’ position
that the database is complete for PCNB.  In HED’s Response to Comments
(February 3, 2005. D312692) the incomplete nature of the database was
previously addressed on  pages 11-13.

The Agency also notes that available developmental toxicity studies are
incapable of assessing functional effects (including thyroid hormone
effects) on the developing fetus.  Since the thyroid is a target organ
of PCNB toxicity, this constitutes a trigger for additional testing to
determine if there are  functional/endocrine effects upon the developing
offspring.  Other uncertainties relate to the potential for
bioaccumulation of PCNB and/or metabolites and, deficiencies in
available kinetic and metabolism studies and how these data gaps might
impact upon risks to the developing fetus.  Collectively, the types of
data required to complete a more refined and informed risk assessment of
PCNB might dramatically affect the level of concern relative to the
developing fetus and significantly alter the quantitative risk
assessment.  Due to the nature of  the uncertainties apparent in the
PCNB database and the potential impact upon the developing fetus, the
application of the 10X FQPA safety factor is necessary.  The
determination of “increased susceptibility” of the fetus is only one
factor considered in the retention of an FQPA uncertainty factor.  A
weight-of-evidence analysis that includes both hazard and exposure
considerations is used to determine the retention of the 10X FQPA Safety
Factor. 

Comment:  On page 16 of the AMVAC/Crompton comments, the registrants
reference an earlier 1993 Agency review of the 90-day mechanism study
(MRID# 42630801) in male rats and indicated that the toxicology of PCNB
has been adequately characterized. 

Response:  The Agency identified numerous limitations in the design of
this study and included discussion of the limitations in its review.  In
addition, as part of the current review process,  HED has re-evaluated
the cited study and the new HED evaluation underwent a peer review
process.  Relevant data from the new data evaluation record (DER) are
included in the PCNB Revised Toxicology Chapter (L. Chitlik, January 7,
2005).  This more recent review further highlighted deficiencies in the
study including the fact that a NOAEL was not determined and that
effects were apparent at the lowest dose level.  In addition, it was
noted that serious study design deficiencies precluded use of the study
to fulfill any data gaps but that the report contained some useful
information about PCNB toxicity on thyroid function in male rats.  The
findings in this study also support the retention of the 10X FQPA safety
factor.  

Comment:  On page 17 of the AMVAC/Crompton comments, the registrant
states that “In addition, to serum thyroid protein carriers, there are
differences between humans and animals in size, lifespan, and
pharmacokinetics and pharmacodynamics of endogenous and exogenous
chemicals.   Any comparison of thyroid carcinogenic responses across
species must take these factors into consideration (adapted from
Assessment of Thyroid Follicular Cell Tumors EPA/630/R-97/002 March
1998).”  

Response:  HED welcomes the citation of an Agency publication. 
Differences in size, lifespan, kinetics and dynamics, and many other
factors are recognized and are apparent in rat studies versus humans. 
However, small populations of  rats used in toxicology test groups are
also considered extremely useful in the hazard identification/risk
assessment process as predictive indicators for humans.  As policy,
Agency risk assessments are based upon the most sensitive species as the
relevant basis for human risk assessment.   

Comment:  The registrants note on page 17 of their submission that the
Agency changed the 10Xufdb to a 10X FQPA Safety Factor in the February
3, 2005 document.  

Response:  HED made this change because it determined that the change in
assignment of the safety factor better reflects HED’s concerns
relative to potential PCNB effects upon  the developing offspring.  

Comment:   On page 17 of the AMVAC/Crompton submission, the registrants
state that “Decreases in ALT, and to a much lesser extent AST, noted
in these studies are not clinically significant or relevant. 
Furthermore, in the absence of any related adverse effects, this effect
is of no toxicological significance.”  

Response:  In HED’s Response to Comments (February 3, 2005) D312692,
these comments were addressed on page 13.  

V.  Occupational and Residential Exposure tc \l1 "V.  Occupational and
Residential Exposure 

Residential and Non-Occupational Postapplication Risk tc \l2
"Residential and Non-Occupational Postapplication Risk 

Comment:  The residential handler risk assessment reveals MOEs that are
mainly >100 with only a few below 100.  Exposure mitigation of various
types will be required for at least these uses, and some of the relevant
applications may demand Restricted Use labeling.  The assessment also
shows higher than acceptable post-application risk for residential use
(some of the MOEs are well below 100, particularly for toddler
hand-to-mouth and object-to-mouth assessments).  It is clear that
mitigation will be required for some of these uses as well.  However, as
the Agency begins to apply the ORETF data, generated as a result of the
Agency’s DCI, the risks associated with the use of PCNB in residential
areas will be shown to be well within acceptable levels. Potential
mitigation options will be the subject of a more detailed document.

Response:  The margin of exposure selected by HED included a 10X FQPA
Safety Factor for residential handlers and postapplication activities
associated with residential uses of PCNB.   Therefore, the level of
concern (LOC) for residential assessment is1000 and not 100.  The
residential handler risk assessment indicates that 5 out of 8 dermal
margins of exposure (MOEs) are less than 1000 and also, 4 out of 8
inhalation MOEs are less than 1000.  For residential postapplication
hand to mouth activities all the MOEs are less than 1000 (the majority
being less than one).  For residential high contact activities
(i.e.,jazzersize), mowing turf, and golfers, all the MOEs are less than
the LOC of 1000 (except mowing turf at the lower application rate).   

Comment:  Golf Courses - For golf course handlers, potential exposure
concerns appear to be adequately mitigated through common PPE, and a
potential restriction of use to greens, tees, and fairways should also
decrease mean areas treated to well below those assumed in the risk
assessment.  However, concern is expressed over post-application
exposure to golfers, with calculated MOEs falling short of 1000 by a
factor of approximately two on day zero.  Yet EPA’s assessment of this
scenario was not supported by full consideration of the relevant data,
but only by conservative assumptions that have greatly overestimated the
potential risk.

First, PCNB is most typically used on golf course turf to control snow
mold, which occurs in northern latitudes and requires one application
just prior to snowfall.  In this case, golfers would be exposed to PCNB
during the short application window in late fall, when the few golfers
who play so do less frequently, which would generally result in one or
two exposures per year. However, EPA has used a toxicology study
involving 21 days of continuous exposure to assess risk in these
scenarios, a much higher frequency of exposure.  Since the NOAEL from
the 21-day study is far higher than the chronic study NOAEL (or dermal
equivalent), and since PCNB acute toxicity is extremely low, the NOAEL
from a study of a more appropriate duration would likely be much higher,
suggesting that MOEs would, in fact, be far higher than acceptable.

Response:  The short- and intermediate-term dermal endpoint selected by
the HIARC was based on a 21 day dermal rat study.  A NOAEL of 300
mg/kg/day was selected based on heptocellular hypertrophy,
hepatocellular hyperplasia, and thyroid hypertropy.  No long-term
endpoint was deemed necessary.  Short -term duration is from 1-30 days. 
The risk presented in HED’s assessment is representative of exposure
for golfers entering on day one.  According to the registrants, PCNB is
typically used in northern latitudes and requires one application just
prior to snowfall.  But even in northern latitudes snow fall occurs at
different times of the winter and occasionally, milder winters will let
the golfers use the golf courses, even past the first snow fall.  The
frequency of use is not relevant in this assessment since HED assessed
exposure for golfers entering the golf course on day one and the short
and intermediate -term endpoints are the same.  Therefore, the risk
presented in this assessment is the same from day1-180.

Comment:  Second, EPA has exaggerated PCNB turf transferable residues
(TTRs) by a factor of more than five by discounting a recent
high-quality study on the subject (MRID# 44687101), apparently because
the study showed relatively low TTR results: Less than 1% of rate was
transferred versus the 1 to 5% that EPA apparently requires for its
default transfer coefficient (TC) policy to apply.  However, since there
is no justification for study rejection based on guideline compliance or
data quality, and since the techniques used are the most standard
techniques available, there is no justification for non-use of this
data.  The issues relating to the quality of the studies from which
EPA’s default TCs were developed may be significant, but they are not
relevant to the acceptability of the TTR study.

There are also significant issues surrounding EPA’s default TC for
golfers.  The study cited in EPA ExpoSAC Policy 003.1 was conducted on
mowing treated turf, which involves significant hand exposure from
handling and cleaning contaminated equipment and clippings.  Golfing is
a far different activity, with far less hand exposure, or exposure to
clippings, and generally drier conditions.  Thus, data more relevant
than mower exposure is needed.  In fact, data is now being generated by
ARTF as well as the University of Massachusetts (Amherst) on exposure
monitoring of actual golfers, and certain maintenance workers, both of
which are far more relevant to this assessment.  These data are expected
to confirm that, regardless of the TTR data used, golfers experience
less exposure than mowers, and, consequently, golfer exposures to PCNB
have been significantly overestimated.  In the meantime, with only a 2X
difference between target and calculated MOEs, even with the
considerable conservatisms and uncertainty/safety factors mentioned at
the beginning of this note, mitigation of golfer exposure should not be
necessary, as there is no excess risk to mitigate.

Results from the new ARTF study report should be available in 3Q05 (with
study completion shortly thereafter) and will confirm that, on the basis
of the currently available data, risk mitigation is not required.  While
there are various risk mitigation alternatives that might be discussed
with EPA at the anticipated follow-up technical meeting, the registrants
need to better understand the basis for the Agency’s conclusion that
mitigation is actually necessary.

Response:  TTR data generated by ORETF members rely on a modified
version of the California roller (ORETF roller) that appears to have a
much lower transfer efficiency (percent of application rate) than the
original version.  Many TTR data submitted by ORETF members show a
percent of transfer of less than 1% of the application rate for sprayed
formulations and less than  0.5% of the application rate for granular
formulations.  ORD has conducted a round robin test of TTR methods that
included the ORETF roller (Fortune 1997).  While ORD concluded that the
ORETF roller performed the best of all methods, transfer efficiency for
three liquid herbicide formulations indicated a transfer efficiency of
~0.5%.  The ORETF data should not be used with the revised TCs shown
below since these revised TCs are based on TTR transfer efficiencies of
~1-5% (transfer efficiency = % of the application rate).  Therefore HED
did not consider data with discrepancies in measurement techniques.  HED
used the submitted data for postapplication activities of sod farm and
golf maintenance activities.  In the submitted studies HED used ARTF TCs
in which the measurements were conducted with the California roller
(ORETF roller).  For golfers’ postapplication assessments, until HED
receives the actual data, it is HED’s policy to use the data from a
turf study with a TC of 500 and a TTR value of 5% of application rate.

Occupational Handler Risk tc \l2 "Occupational Handler Risk 

Comment:  Cole crops (refer to scenario 42 in the occupational risk
assessment) -  The EPA assessment concluded that exposure to workers
mixing/loading the WP formulation for chemigation applications in cole
crops may be excessive even with water soluble packaging, and requires
mitigation for other WP use scenarios in cole crops.  For chemigation,
the assessment did not consider the use of a dust mask or respirator as
mitigation in addition to a closed-system engineering control, which
together may present an acceptable solution.  Furthermore, it is likely
that exposure in other WP use scenarios in cole crops could be
acceptably mitigated with commonly available PPE.  Alternative
formulations do not appear to have the risks associated with the WP and
so are possibilities for mitigation.

Response:  One type of engineering control available for pesticide
mixing and loading is the use of water soluble packets.  The goal for
using water soluble packets is to reduce the personal protective
equipment (PPE) that would normally be required when handling
pesticides.  The exemption from certain PPE is considered an incentive
to use water soluble packets.  Inasmuch as PPE can be uncomfortable to
wear (respiratory protection) and also cause thermal discomfort
(chemical resistant coveralls), use of engineering controls also avoids
the constellation of problems associated with PPE (heat stress,
decreased mobility, physical stress, lack of fine motor skill, false
sense of security).  Therefore additional PPE defeats the whole purpose
of putting the  product in a water soluble packets. 

Comment:  Commercial/industrial lawns (scenarios 65, 87, and 96) - For
high-pressure hand-wand application to commercial/industrial turf EPA
calculated MOEs ranging from 18 to 59, depending on use rate.  However,
this application technique is rarely employed on turf of any kind, and
is used only for the smallest sites of this type.  In addition, the EPA
assessment assumed that 1000 gallons of treatment would be applied in a
day by this technique, but such an application would be impractical, as
continuous spraying for more than one typical workday would be needed to
apply that much through a common hand wand.  Furthermore, since the
highest rates for PCNB on turf apply to uses involving small areas of
turf and spot-treatments and generally are not used on larger areas, no
additional mitigation measures for application to commercial or
industrial lawns should be considered necessary.

Response:  HED addressed this issue in a phone conversation between the
Agency and the registrants (participants were Betsy Katzman and Kevin
Donovan 4/21/05).  The equipment assessed for scenarios 65, 87 and 96 is
a high pressure hand wand.  This type of equipment is commonly used by
Lawn Care Operators (LCOs) and LCOs can treat a large amount of turf in
an 8-10 hour shift.  It is HED policy to use 1000 gals a day for this
type of equipment.  Please refer to the labels for the recommended usage
of  between 1 to 15 gallons of water per 1000 sq feet.  This in effect
recommends that to spray one acre it would take a maximum of 650
gallons.

Comment:  Concern was also expressed over handling of granular
formulations (inhalation MOE of 44) but no protection factor was
applied.  In this case, the registrants urge EPA to consider the very
well-established protection afforded by a dust mask or respirator, which
is very commonly applied by EPA in many other instances, and is clearly
supported by other U.S. government agencies.  EPA erroneously claims
that information is lacking to quantify such a mitigation in this
scenario, when, in fact, mitigation afforded by a respirator is not
scenario-specific.  A respirator designated as “PF10” is designed to
provide a 10X mitigation factor to the ambient air concentration
independent of work scenario and without additional conditions.  Since
ambient air was measured in exposure studies used for this assessment
and an additional safety factor of only 2-5X is required for this
scenario, use of a respirator is sufficient mitigation.  A dust mask is
also a well established form of risk mitigation that is adequate for
this scenario.

Response:  HED concurs with the registrants, that using a dust /mist
respirator reduces the risk by 80% (5 fold pf).  Therefore, the MOE for
scenario 96 is 220. 

Comment:  Ornamentals (scenarios 58, 98, 100, and 101) - EPA’s
assessment shows handler risk concerns for applicators spraying
ornamentals by high-pressure hand wand, low-pressure hand wand, and hand
gun, as well as concerns for mixer/loader/applicators of the wettable
powder.  However, of the three application techniques included in the
assessment PCNB is generally applied to ornamentals only by drench using
a low-pressure hand wand.  As the PHED Surrogate Exposure Guide
suggests, through the scenarios it has included, low-pressure hand-wand
exposure is best assessed as a mixer/loader/applicator (M/L/A) scenario
because applicators typically mix and load their own equipment for such
small-scale applications.  Yet although the surrogate exposure guide
includes both WP and liquid scenarios for low-pressure hand wand M/L/A,
the PCNB assessment only included low-pressure M/L/A scenarios only for
wettable powder (100 and 101) and failed to include the liquid
low-pressure M/L/A scenarios.

Response:  There is no specification on the type of hand held equipment
on the label, the HED assessment is conducted to cover a broad range of
hand held equipment.  With regard to adding the liquid formulation to
the assessment, if the registrants provide HED with the REG number for
the liquid used on ornamentals, the scenario will be considered. 

Comment:  The PHED Surrogate Exposure Guide lists the dermal
unit-exposure for liquid low pressure M/L/A (Scenario 32) as only 5%
that for the WP (Scenario 33), without correction for an additional
layer of dermal protection.  (With this correction, liquid exposure may
be even less relative to the WP.)  Applying Scenario 32 to the PCNB risk
assessment would show dermal MOEs above 100 for these scenarios, or high
enough to be adequately mitigated by optimizing the P.E. requirements. 
For inhalation exposure, the PHED value for liquid low-pressure M/L/A is
only ~2.7% of that for the WP, and, as with dermal exposure, MOEs would
approach or exceed 100 employing Scenario 32.  Similarly, should
additional mitigation of inhalation exposure prove necessary, a
respirator requirement that is more specific than those generically
associated with PF10 would provide the necessary protection to increase
MOEs to acceptable levels.  In addition to the above, the Agency has
calculated low dermal MOEs for granular application to ornamentals by
belly grinder, while inhalation exposure was found to be adequately
mitigated by respiratory protection.  However, dermal P.E. in addition
to gloves was not considered here, and would significantly increase the
MOE if it were.  In addition, the extremely high rate assumed (217.8 lb
AI/ac) likely overestimates typical use.  It may be possible to prohibit
this application scenario on product labeling for ornamentals, but if
this scenario were found to be critical for a particular crop or site,
exposure could be acceptably mitigated through the above measures.

It is clear that in most cases various common mitigation options are
available and adequate. Alternative formulations do not appear to have
the risks associated with the WP and so are possibilities for
mitigation.  It should also be noted that data generated by ARTF and
AHETF will support the fact that risks from these uses are not
excessive.

Response:  Scenarios 32 and 33 are loading granulars for tractor drawn
spreader application for cole crops and bean.  The registrants’
comment refers to a mixing/loading/applying scenario for the wettable
powder.  Clarification from the registrants is needed.

Comment:  Sod Farms (scenarios 6, 16, 50 & 51) -  EPA’s assessment
concluded that MOEs are not acceptable for mixing/loading in chemigation
uses on sod farms, and also that the MOE for mixing/loading the WP
formulation for ground boom application to sod falls just short of
acceptable with closed mixing systems.  To maintain the WP use on sod in
the near term, the registrants believe that use of a combination of P.E.
and engineering controls, as EPA describes, would provide adequate and
practical exposure mitigation.  Moreover, the aforementioned strongly
conservative aspects of the modeling provide more than adequate latitude
to retain these uses.  This is an area that the registrants look forward
to discussing with EPA at the anticipated follow up technical meeting.

Response:  Scenario 6 -  Mixing/loading dry flowable for chemigation on
sod farms.  For this scenario HED used the maximum amount of PPE ,which
are gloves, coveralls, and an OV respirator.  The dry flowable
formulation is not marketed in any closed system packaging and even if
it was, HED has no exposure data to be able to assess this scenario.

Scenario 16 -  Mixing/loading liquid for chemigation on sod farms.  HED
has considered mitigation by including the risk from baseline through
maximum PPE to engineering controls.

The inhalation MOE is below 100, even with using closed systems.  The
exemption from certain PPE is considered an incentive to use closed
systems (i.e., closed system), inasmuch as PPE can be uncomfortable to
wear (respiratory protection) and also cause thermal discomfort
(chemical resistant coveralls).  Use of engineering controls also avoids
the constellation of problems associated with PPE (heat stress,
decreased mobility, physical stress, lack of fine motor skill, false
sense of security).  It is HED’s policy not to impose additional PPE
with the use of engineering controls.

Scenario 50 -  Mixing/loading wettable powders for chemigation on sod
farms.  HED has mitigated the risk from baseline through maximum PPE to
engineering controls.  The inhalation MOE is below 100, even with using
closed systems.  One type of engineering control available for pesticide
mixing and loading is the use of water soluble packets.  The use of a
water soluble packets allows for a reduction in the PPE ensemble that
would normally be required when handling pesticides.  The exemption from
certain PPE is considered an incentive to use closed systems (i.e., 
water soluble packets), inasmuch as PPE can be uncomfortable to wear
(respiratory protection) and also cause thermal discomfort (chemical
resistant coveralls).  Use of engineering controls also avoids the
constellation of problems associated with PPE (heat stress, decreased
mobility, physical stress, lack of fine motor skill, false sense of
security).  Therefore it defeats the whole purpose of engineering
controls with additional PPE.

Scenario 51 -  Mixing/loading wettable powders for ground boom
application on sod farms.  HED has mitigated the risk from baseline
through maximum PPE to engineering controls.

The inhalation MOE is below 100 even with using closed systems.  It is
HED’s policy not to impose additional PPE with the use of engineering
controls.

Seed-handler Risk tc \l2 "Seed-handler Risk 

Comment:  EPA’s letter on risk management indicates that none of the
individual seed treatment tasks are associated with unacceptable MOEs
for PCNB exposure.  Yet despite that determination, it also noted that
inhalation MOEs can fall below 100 for workers performing multiple tasks
at certain seed treatment plants, specifically for rice, soybean,
barley, and peas.  Nevertheless, the Agency did state that workers are
more likely to perform multiple activities at smaller facilities, which
is true primarily because the capacity of the larger facilities requires
at least one full person-day for each type of work task in order to meet
production targets.  In EPA’s assessment, seed treatment MOEs have
been calculated by crop, and not by facility size.  It is the
registrants’ view that if the seed treatment rates for workers
performing multiple activities were adjusted to reflect the smaller
production capacities of facilities in which multiple-activities workers
could be found, MOEs would far exceed target.  Workers performing
multiple activities would be particularly scarce in rice and soybean,
for which seed treatment facilities generally have dedicated
larger-scale equipment that requires at least one person to
mix/load/apply and two or more additional people just to run the seed
packaging line.  Capacities of the smaller facilities that employ
multiple-activities workers fall far short of the worst-case estimates
EPA has employed based on the higher-production facilities dominant in
some crops, by factors of five or more for larger-scale crops such as
rice and soybean.  Therefore, exposures calculated for these workers
have been exaggerated to a similar degree.  As both EPA and AHETF are
aware, and as the minutes of their joint meetings reflect, practical
definition of work activities and equipment parameters in seed treatment
exposure requires additional research, including investigation of other
potential determinants such as seed type and formulation
characteristics.  The registrants urge EPA to continue to work with
AHETF on the development of data that will answer many

questions on seed treatment exposure that have not yet been answered. 
Meanwhile, exposure mitigation to address small discrepancies in MOEs,
such as the above, should be approached cautiously.  In the case of
PCNB, the large differences in capacities between the larger facilities
with labor specialization and the smaller facilities in which workers
actually perform multiple activities, provides assurance that workers
are not being overexposed within this scenario.

Response:  The registrants may have a valid point, however, without any
data on smaller facilities, HED must rely upon the data that are
available.  The major small facility study (Fipronil study) uses a type
of seed treater (S800) which is capable of treating 500-1,000 bushels
per hour, which is not representative of the capacity of most smaller
facilities.  It should be noted that the available data in this area
have been limited but have grown in the past few years.  Because of the
lack of data, HED is not able to refine the assessment to differentiate
between larger and smaller facilities.

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