UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460      

	OFFICE OF PREVENTION, PESTICIDE                                        
                              AND TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 MEMORANDUM

Date:		June 18, 2008

SUBJECT:	1,3-Dichloropropene, PC Code 029001, DP Barcode 347278; HED
Component of Response To Comments Document On 1,3-Dichloropropene Phase
5 Fumigant Risk Assessment

 

PC Code:  029001	DP Barcode:   D347278

Decision No.: 386928	Registration No.: Various

Petition No.: N/A	Regulatory Action: Reregistration

Risk Assessment Type: 

Response to Phase 5 Comments	Case No.: N/A

TXR No.:  N/A	CAS No.: 542-75-6

MRID No.:  N/A 	40 CFR: N/A

		              									Ver.Apr.08

FROM:		Jeffrey L. Dawson, Chemist/Risk Assessor

Reregistration Branch 1

Health Effects Division (7509P)

Whang Phang, PhD Toxicologist

Registration Action Branch 3

Health Effects Division (7509P)

THROUGH:		Michael Metzger, Chief 

Reregistration Branch 1

Health Effects Division (7509P)

TO:		Andrea Carone, Chemical Review Manager For 1,3-D

		Special Review & Reregistration Division (7508P)

This document serves as the response to those comments received on the
phase 5 risk assessments and initial risk management proposals related
to 1,3-D that are appropriate to be addressed by the Health Effects
Division.  This document will provide the basis for an overarching
Agency response to comments document which will be prepared by SRRD
staff that will be a compilation of the comments received pertaining to
the fumigant effort.  The summary of the comments that has been prepared
by SRRD has been used as the framework for this document (i.e., comment
numbers and SRRD numbers relate to that compilation document).



#	Docket Sent to, Docket #, & Submitter	SRRD

#	Fumigant Addressed	Public Comment	Div. to Review





Toxicology Comments

	7	  HYPERLINK
"http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetai
l&d=EPA-HQ-OPP-2005-0124-0164.1"  EPA-HQ-OPP-2005-0124-0164.1 

Cal DPR Nov. 2	108	1,3-D	PLEASE SEE THE REVISED DOCUMENT FOR THE
COMMENTS ON THE FOLLOWING:

Acute inhalation NOEL, short-ter  inhalation NOEL, California HEC’s,
Unit risk for cancer effects, and protective nature of the risk
assessment.	On page 17 of the 1,3-Dichloropropene: HED Human Health Risk
Assessment (Phase 5) (4/12/2007), HED presents a concise explanation for
why HED’s approach to inhalation exposure risk is different  from 
that of Cal DPR. The basic difference is that Cal DPR  selects the acute
and short-term toxicity endpoints based on the dominant lethal assay in
rats (MRID 44302801).  The selected toxicity endpoint is the  decrease
in body weight at 60 ppm. The NOAEL is 10 ppm.  From the US EPA point of
view, the results of the dominant lethal assay show that  the decrease
in body weight noted in the dominant lethal assay occurred after 7 days
of exposure; therefore, this effect is not the result of a single-dose
exposure. For acute risk assessment, EPA assesses the risk from single
dose exposure and over a single day. 

For short-term inhalation exposure, EPA considered all the results of
the subchronic and chronic toxicity studies, developmental toxicity
studies and the dominant lethal assay in rats in establishing the
short-term toxicity endpoint. It was determined that the decrease in
maternal body weight seen in the developmental toxicity study to be
appropriate as the toxicity endpoint with the supporting evidence from
the subchronic and chronic toxicity studies. The NOAEL of 20 ppm as the
point of departure for risk assessment is protective of the decrease in
body weight seen  at  60 ppm in the dominant lethal assay which has been
employed by Cal DPR for establishing the toxicity endpoint for risk
assessment.   

24	  HYPERLINK
"http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetai
l&d=EPA-HQ-OPP-2005-0123-0430.1"  EPA-HQ-OPP-2005-0123-0430.1 

PANNA	38	1,3-D	EPA used unrepresentative use data for 1,3-D to estimate
cancer risks. The data used were from a time period and a location in
California where 1,3-D had severe restrictions placed on its use.	The
Agency used all appropriate, available data at the time to develop the
risk assessment for 1,3-D.  The Agency also recognizes that the data
used in the 1,3-D risk assessment do not completely address all of the
possible situations related to airshed types of exposure related to
1,3-D.  The Agency would use an airshed based estimate of exposure in
any refined approach for evaluating cancer risks from 1,3-D.  For this
reason, the Agency asked for additional monitoring and modeling to
address airshed issues in the 2005 assessment.  Once available, any
resulting data will be used to conduct updated risk assessments.  

While DPR has limits (township caps) on 1,3-D use, few townships reached
the limits in 200 and 2001. This indicates that use was not reduced due
to regulatory limits. However, 1,3-D use has increased in recent years
with the continuing phaseout of methyl bromide. CARB conducted
additional air monitoring for 1,3-D in 2005 and 2006. This monitoring is
representative of one of the highest use areas in California, and EPA
has updated its exposure estimates to include the recent data. 



33	  HYPERLINK
"http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetai
l&d=EPA-HQ-OPP-2005-0123-0430.1"  EPA-HQ-OPP-2005-0123-0430.1 

PANNA	38	1,3-D	We are still concerned that the acute and short-term
NOAELs selected by EPA are too high and that EPA is re-defining what
“acute” means, without adequate peer review. The details about the
dominant lethal assay for inhalation in rat are still missing from the
report.	Based on the currently available data,  the acute and short-term
toxicity endpoints established for risk assessment are appropriate, and
the NOAEL’s employed for risk assessment are protective of the 
effects seen  with the acute and short-term exposures.(Please also see
HED Response to #7).    

The  toxicity endpoint for  “acute” exposure has always been an
adverse effect which can be attributed to a single dose.

The executive summary of the dominant lethal assay  in rats (MRID
44302801) is appended to the end of the Appendix A: Executive summary
for critical studies and Toxicological Profile.

410



Sealing Methods – Water & Soil Seal

	413	 HYPERLINK
"http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetai
l&d=EPA-HQ-OPP-2005-0124-0158" \o "EPA-HQ-OPP-2005-0124-0158"
EPA-HQ-OPP-2005-0124-0158 

Calvin Oda, Maui Pineapple Company, Ltd. U. of Hawaii	111

	1,3-D	Sealing methods at anthurium farms involve watering-in, then
installing a tarp immediately after application.  The tarp remains in
place for one week.

All pineapple fields treated with 1,3-D are mulched with HDPE mulch
films.  Agricultural mulch films not only help to retain soil fumigants
in treated soil but also conserve soil moisture, elevate soil
temperatures, control weeds under the mulched surface, and provide
planting marks for manual planting operations. 

Previous studies indicated the post fumigation irrigation to seal the
soils was not as effective as application at the proper soil depth,
sealing of the chisel trace(s), and use of agricultural mulches.  	The
Agency has used all available emissions data in the development of its
risk assessments.  The Agency has also been very actively pursuing
plausible approaches for using first principles factors and other
approachs for developing a broader understanding of how changing
conditions can influence emissions (D306857).  Additionally, the Agency
has actively pursued information on this issue in a variety of
stakeholder meetings and through the Methyl Bromide Alternative Outreach
conference.  Please refer to the programs for 2006/2007 for more
information (  HYPERLINK "http://www.mbao.org/"  http://www.mbao.org/ 
).  

Modifications to the risk assessment for 1,3-D will be made as
appropriate pending further interpretation of the factors analysis and
as appropriate.

426	  HYPERLINK
"http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetai
l&d=EPA-HQ-OPP-2005-0124-0157.1"  EPA-HQ-OPP-2005-0124-0157.1 

Schramm Williams & Associates, Inc., California Fresh Carrot (1,3-D)
93.1	1,3-D	Shank injection methods for 1,3-D help reduce offsite
emissions

All fumigants can benefit from compaction sealing.  	As described in the
responses to several comments above, the Agency has used all available
emissions data in the development of its risk assessments.  The Agency
has also been very actively pursuing plausible approaches for using
first principles factors and other approachs for developing a broader
understanding of how changing conditions can influence emissions
(D306857).  Additionally, the Agency has actively pursued information on
this issue in a variety of stakeholder meetings and through the Methyl
Bromide Alternative Outreach conference.  Please refer to the programs
for 2006/2007 for more information (  HYPERLINK "http://www.mbao.org/" 
http://www.mbao.org/  ).  The Agency would agree that the design of
certain application implements can reduce emissions.  Also, the Agency
believes that compaction and/or other sealing methods are critical
elements in an overall strategy to reduce emissions.



489



Application Block Limits

	523	  HYPERLINK
"http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetai
l&d=EPA-HQ-OPP-2007-0350-0107.2"  EPA-HQ-OPP-2007-0350-0107.2 

Kees Weyns, Weyns Farms	69.1	Metam, Pic, Telone	Washington State does
not have the regulatory bodies in place to limit how many acres can be
fumigated in one area at a certain time.  If such limits were forced
onto the region it would be a logistics nightmare between growers,
applicators, and dealers.  

We have such a brief time period transitioning the fields from
harvesting previous crops to preparing a field for fumigation.  Here’s
one example: field corn planted in the Columbia Basin on the 15th of
April can be dry enough to harvest by the 15th of October.  A 125-acre
circle will take two days to combine with one machine.  Then over the
course of three more days, two tractors will shred and disc the stalks
thoroughly into the soil.  Then soil samples can effectively be pulled
to determine the nematode threat for that particular field.  It can take
up to ten days before the sample results are received from the lab
during the busy fumigation season, since we only have one dependable
nematology lab for the some 170,000 acres of potatoes and onions grown
in the basin.  After the grower sees the nematode levels, he consults
with varies crop advisors to see what they recommend and how much its
going to cost.  Then they call me to see if I can start on their field
“first thing in the morning.”  Since I work with about 15 growers,
10 crop advisors, and 7 dealers, the answer to his question is usually
“no, but maybe the day after, if it doesn’t freeze up first.”  I
don’t think having to get clearance from a governing body on whether
or not I can fumigate a field, that I might get started on in a couple
of days, is going to streamline this process any.  Let alone if we can
only run our $350,000 applicators during the 8-10 daylight hours of
October and November.  

I do not believe the data concerning higher emissions from night time
applications is correct.  If the data showed increased emissions from
night applications, then one could conclude that less chemical is fuming
the soil during that same period.  Of all the fields I have fumigated, I
have never seen a pattern that would correlate to decreased efficacy
from night applications.  My family has invested over $750,000, and
countless hours of work and stress into our fumigation operation.  The
only way we can make positive returns to our investment is to run these
tractors 18 to 24 hours a day during the short time period ideal for
fumigation. By limiting the amount and times we can fumigate, the agency
will place undue economic stress on the growers, dealers, consultants,
and especially the applicators.	Most of this comment has been addressed
separately in responses developed by risk managers.

With regard to the nighttime emissions.  All data were used in the risk
assessments.  At one point there was consideration of placing
limitations on the time of day during which applications could be made. 
The point of this was to possibly eliminate the co-occurrence of peak
emissions with calmer atmospheric conditions that would lead to
potentially higher exposure concentrations.  The Agency is not going to
implement this approach because so many factors influence peak emissions
and it places very difficult logistical restrictions on users.

937



Risk Management Comments

	1045	  HYPERLINK
"http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetai
l&d=EPA-HQ-OPP-2005-0123-0430.1"  EPA-HQ-OPP-2005-0123-0430.1 

PANNA	38	1,3-D	(page 10) EPA is still underestimating the cancer risks
from use of 1,3-dichloropropene, because the data from which exposure
was estimated was collected when California’s township caps and other
use restrictions for 1,3-D were in effect. Under these conditions,
EPA’s exposure estimates are not accurate for other states where there
are no such restrictions, nor will they be accurate if township caps are
lifted in California and use continues to increase. In response to this
concern, EPA indicates they “used the best available data.” However,
additional information is available to modify the assessment to provide
a more accurate picture of exposure. EPA failed to use this information.
Thus, EPA’s conclusion that their assessment is representative of
high-end exposure is not correct. The upper end cancer risks are likely
to be higher than predicted by EPA, and the number of people exposed to
levels above the unit risk are higher than estimated by EPA. The
appearance of increased rates of pancreatic cancer in human populations
living in areas of high 1,3-D use for 20 years  should not be dismissed
by EPA.	The Agency calculated risks from ambient sources of 1,3-D using
all available data and the best available data.  In Section 5.2 of the
comment PANNA indicates that “additional information is available to
modify the assessement to provide a more accurate picture of
exposure.”  However, these data, to the best knowledge of the Agency
were not submitted or cited in conjunction with the comment.

Additionally, the Agency concurs with PANNA  that in areas where 1,3-D
township caps are not in place that it is possible ambient levels could
exceed those defined in the available monitoring data.  In fact, the
Agency acknowledged this uncertainty in its characterization of the
ambient risk estimates for 1,3-D on page 56 of the risk assessment
available at   HYPERLINK "http://www.regulations.gov" 
www.regulations.gov  (EPA-HQ-OPP-2005-0124-0052).  In this document it
was indicated “It is clear from the characterization of the data
provided by CARB that some data represent highly targeted monitoring in
a region during the season of use and others represent urban background
levels.  Because of these criteria, the results should be considered
representative for the state of California in the context that
California has a number of restrictions and systems in place where the
overall goal is to reduce environmental emissions from fumigant use.  As
such, it is difficult to quantify how the results above may apply to
other regions of the country that do not have these types of
programs.”

It is also clear that 1,3-D is used extensively in other states as
illustrated by the fumigant use summary document (page 16 for 1,3-D of
“Overview of the Use and Usage of Soil Fumigants, Becker et al,
6/15/2005). For this reason, the Agency is asking that additional data
be required of 1,3-D registrants to provide information on ambient air
concentrations in areas of high use other than California in order to
better address this issue.



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