v/EPA
United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508C)
EPA-738-F-98-014
December 1998
R.E.D. FACTS
1,3-Dichloropropene
Pesticide
Reregistration
Use Profile
All pesticides sold or distributed in the United States must be registered
by EPA, based on scientific studies showing that they can be used without
posing unreasonable risks to people or the environment. Because of advances
in scientific knowledge, the law requires that pesticides which were first
registered before November 1, 1984, be reregistered to ensure that they meet
today's more stringent standards.
In evaluating pesticides for reregistration, EPA obtains and reviews a
complete set of studies from pesticide producers and uses these data to
evaluate the human health and environmental effects of each pesticide,
including aggregate exposures from all sources of pesticide residues, whether
infants and children have heightened susceptibility to pesticide residues, and
whether there are cumulative effects of pesticides and other compounds with a
common mechanism of toxicity. The Agency develops any mitigation
measures or regulatory controls needed to effectively reduce each pesticide's
risks. EPA then reregisters those pesticides that can be used without posing
unreasonable risks to human health or the environment.
When a pesticide is eligible for reregistration, EPA explains the basis for
its decision in a Reregistration Eligibility Decision (RED) document. This fact
sheet summarizes the information in the RED document for reregistration case
0328, 1,3-Dichloropropene (1,3-D or trade name Telone).
1,3-D is a pre-plant soil fumigant used to control nematodes and is
registered for use on soils to be planted to all crops. Combining chloropicrin
with 1,3-D increases herbicidal and fungicidal properties. The registrant, Dow
AgroSciences, is also developing a formulation to be applied in drip irrigation
systems as a pre-plant soil fumigant. 1,3-D use is restricted to certified
applicators and is applied using specialized tractor-drawn rigs which inject 1,3-
D 12" to 18" beneath the soil surface. Soil sealing after application is required,
and is accomplished by compacting the top layer of soil, applying a water seal,
or using tarps. The 1,3-D labels require handlers to wear respirators (except
for a limited exception for applicators in enclosed cabs). The labels also
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Regulatory
History
Human Health
Assessment
stipulate a 300 foot no-treatment buffer from occupied buildings to reduce
risks to residents who live near treated fields and will require as of
August 1, 1999 a 100 foot no-treatment buffer from drinking water wells.
The registrant suggests a waiting period (a week for every 10 Ibs. 1,3-D
applied) before planting any crops due to phytotoxicity.
The Agency expects 1,3-D use to increase as it replaces certain methyl
bromide soil fumigant uses. Methyl bromide is being phased out under the
Clean Air Act and the Montreal Protocol because it has been identified as an
ozone depletor. Methyl bromide is a soil fumigant used primarily on
ornamentals and higher-value fruit and vegetable crops (e.g.,strawberries,
tomatoes). Currently, the highest methyl bromide soil fumigation use occurs in
Florida and California.
1,3-D was first registered as a pesticide in the U.S. in 1954. EPA issued
a Registration Standard for 1,3-D in October 1986, as well as an
October 8, 1986 Federal Register notice announcing a Special Review of
1,3-D based on cancer concerns for workers. An October 1986 Data Call-in
(DCI) required additional residue chemistry, inhalation exposure, and
environmental fate data.
1,3-D labels were modified in 1992 and again in 1996 to include
measures to minimize exposures to workers and for residents who live near
treated fields. The Worker Protection Standard (WPS) requirements for
1,3-D were included in those label changes. On September 30, 1998, Dow
AgroSciences requested additional modifications (see the section titled
"Product Labeling Changes Required"), which will take effect August 1, 1999.
Currently, there are ten 1,3-D products registered to three companies.
There are also three Special Local Needs (or FIFRA section 24(c) registrations
for products containing 1,3-D.
Toxicity
In studies using laboratory animals, 1,3-D generally has been shown to
be of moderate acute toxicity by the oral and dermal routes and has been
placed in Toxicity Category II (the second highest of four categories) for these
effects.
1,3-D is not considered to be a developmental toxicant, though it does
have some mutagenic properties. EPA has classified 1,3-D as a B2, possible
human, carcinogen by both the inhalation and oral routes of exposure. This
classification is based on adrenal, liver, forestomach, thyroid, mammary and
lung tumors in both rats and mice by both routes of exposure.
Dietary Exposure
Studies developed for reregi strati on show no residues in crops grown in
1,3-D-treated soils. The Agency has classified 1,3-D as a non-food use
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pesticide and thus no tolerances or exemptions from the requirement of a
tolerance are required. Because there are no tolerances, no tolerance
reassessment was included in this reregi strati on action, nor are there conflicts
with the CODEX international maximum residue levels.
Other studies conducted for reregi strati on show that 1,3-D can make its
way to ground water under use allowed by 1,3-D labels, where it may pose
risks for residents who obtain their drinking water from wells in the vicinity of
treated fields. Thus the dietary assessment is based on exposures to 1,3-D in
ground water.
The dietary assessment also includes exposures to two degradates of
toxicological concern: 3-chloroallyl alcohol and 3-chloroacrylic acid. EPA
does not have data for a full assessment of the toxicity of these degradates and
thus assumed toxicological and carcinogenic equivalency to the parent.
Occupational and Residential Exposure
1,3-D is injected into the soil as a liquid which then quickly volatilizes
through the soil profile, some of which moves up into the atmosphere. Based
on current use patterns, handlers (loaders and applicators) may be exposed to
1,3-D during and after normal use. Since 1992, the 1,3-D labels have been
modified to include engineering controls (closed loading, equipment to shut off
1,3-D flow at row turns, and soil sealing), personal protective equipment
(respirators and chemical-resistant protective clothing) and other controls (5-
day REI).
Residents who live near treated fields may also be exposed to volatilized
1,3-D which enters the atmosphere during the two week period following
application. Some of the label measures mentioned above were also designed
to minimize 1,3-D levels that volatilize after application, and thus serve to also
reduce residential exposures as well. In addition, lowered application rates and
a 300 foot no-treatment buffer on 1,3-D labels reduce residential exposures.
Residents who live near treated fields can also be exposed through
drinking water. A prospective ground water study conducted in Florida has
shown 1,3-D and degradate levels of concern in ground water, due mainly to
permeable soils and shallow water tables. A ground water study conducted in
Wisconsin showed even higher concentrations of 1,3-D where soils are
permeable and water tables shallow, suggesting cold areas are even more
vulnerable to ground water contamination since 1,3-D degradation is slower
under colder conditions.
Human Risk Assessment
1,3-D generally is of moderate acute toxicity. For chronic non-cancer
effects, anticipated residues (from drinking water) for the overall U.S.
population represents less than one percent of the Reference Dose (RfD), or
amount believed not to cause adverse effects if consumed daily over a 70-year
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lifetime. Based on results from the Florida study, the most highly exposed
subgroup of non-nursing infants less than one year old has an anticipated
residue contribution which represents less than one percent of the RfD. This
fraction of the allowable RfD below 100 is considered to be an acceptable
dietary exposure risk.
The Agency also assessed the risk resulting from chronic 1,3-D
exposures to occupational handlers. The NOEL for inhalation exposure is
0.091 mg/L (from the 2-year chronic rat study). EPA assessed risks to
handlers using Margins of Exposure (MOE's). The MOE is a ratio of the
NOEL to the estimated daily exposure. EPA generally is not concerned with
MOE's greater than or equal to 100. The MOE's for 1,3-D, which were in the
560 to 1960 range, are acceptable.
EPA classifies 1,3-D as a Group B2, probable human, carcinogen by
both the inhalation and oral routes of exposure. In January of 1998, Dow
AgroSciences submitted new information to support regulating 1,3-D as a non-
linear carcinogen (i.e. that below a certain level of exposure, there is no cancer
risk). EPA is scheduling a review of this information for 1999, however, will
not reassess 1,3-D cancer risks until all EPA policies on regulating non-linear
carcinogens are in place.
Dietary Risk - Because exposure through foods grown on treated soils is
not expected, dietary risk is assumed to be solely from drinking 1,3-D residues
in ground water. The Agency assessed the results from prospective ground
water monitoring studies, which were conducted in Florida and Wisconsin and
thought to represent vulnerable sites for ground water contamination. EPA
based the 1,3-D risk assessment on levels found in on-site wells, although all
1,3-D labels as of August 1, 1999 will require a 100' no-treatment setback from
drinking water wells.
From the Wisconsin site, levels (1,3-D plus degradates) found in on-site
wells were associated with risk estimates at 10"3. For the general population,
EPA generally is not concerned with lifetime cancer risks at or below 1 x 10"6.
Based on risks in the 10"3 range, 1,3-D labels are being modified to prohibit use
in areas similar to the Wisconsin site.
From the Florida site, which was used to estimate risks for the general
population, cancer risk estimates (1,3-D plus degradates) from wells located
within the field were approximately 4 x 10"6. The prospective studies were not
designed to assess risks from wells located away from treated fields and thus
EPA cannot quantify risks with the 100' setback, though the levels found 100
feet off-site were about 15 times lower than those found in on-site wells.
Therefore, the risk estimates for exposure to 1,3-D through drinking water are
considered to overestimate risk.
Worker Risk - Inhalation — For workers, cancer risk estimates are in the
10"5 to 10"6 range, taking into account certain personal protective equipment
and engineering controls. Under EPA's Worker Risk Policy, the Agency
considers risks of 10"6 or lower not to be of concern and carefully examines
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risks in the range of 10"4 to 10"6 to seek ways of reducing risks prior to
reregistration. The 1,3-D labels have been modified to include label measures,
such as soil sealing, lowered rates, soil moisture and deeper injection, which
are expected to reduce worker risks, although the mitigation value could not be
quantified. EPA considers worker risk to have been adequately mitigated.
Residential Risk - Inhalation — For residents who live at the 300 foot
buffer, risk estimates are 6 x 10"6, however, this estimate does not include the
full value of mitigation measures listed above and is conservative in the
assumption that a person would spend 16 hours a day at 300 feet from the
treated field during the two-week period following fumigation when 1,3-D
volatilization occurs for 30 years.
Uncertainties in the Risk Assessment - In addition to the uncertainties
discussed above, there were numerous uncertainties in the studies used to
assess exposures. The largest source of uncertainty was trying to conduct
monitoring studies for a highly volatile chemical. Under normal use conditions,
there are a variety of uncontrollable environmental factors that ultimately affect
an individual's exposure. The limited number of monitoring sites also
contributed to the uncertainty related to EPA's risk estimates. Nonetheless,
EPA believes that these studies provide the best information for conducting the
1,3-D risk assessment.
Aggregate Risk for the General Population - EPA has determined that it
is appropriate to aggregate risks from the inhalation and dietary routes of
exposure. For residents who live 300 feet from a treated field, the aggregated
lifetime cancer risk estimates are 1 x 10"5. This estimate, however, is
associated with numerous uncertainties. Taking into account the
unquantifiable mitigation measures and more realistic assumptions on
exposure, EPA believes risks will be adequately mitigated under approved
labeling presented in the RED.
Environmental
Assessment
The Agency has adequate data to assess the toxicity of 1,3-D to non-
target organisms and on 1,3-D's environmental fate. The registrant is also
developing confirmatory data on the degradates, as well as data on estuarine
and marine environments since 1,3-D use is expected to expand in Florida with
the methyl bromide phase-out.
Environmental Fate
The data submitted for reregistration show that 1,3-D is mobile and
persistent (particularly in colder areas). High quality data show that 1,3-D can
contaminate ground water under normal use conditions. EPA believes the
potential for ground water contamination is highest where soils are permeable
and water tables are shallow. Where these characteristics occur in colder
areas, 1,3-D not only enters ground water, but persists under colder conditions.
While EPA does not expect significant levels of 1,3-D in surface water, one
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study suggests that airborne levels of 1,3-D can be transported to adjacent
surface water resources. The registrant is conducting a run-off study and other
monitoring as confirmatory data.
Ecological Effects
1,3-D is highly toxic to invertebrate species, moderately toxic to birds
and mammals and moderately toxic to fish. These toxicity patterns are also
expected for estuarine and marine organisms; the registrant is generating
additional studies since 1,3-D use is expected to expand to estuarine and
marine environments.
Ecological Effects Risk Assessment
Assessment of submitted studies demonstrates that 1,3-D can
contaminate ground water under normal use conditions. EPA also reviewed
other sources of ground water sampling and found few detects, even in
counties where high rates of 1,3-D are applied every year. Thus, EPA believes
that 1,3-D use poses the potential for localized ground water contamination,
rather than widespread aquifer contamination. The registrant is amending 1,3-
D labels to prohibit use under the most vulnerable conditions (permeable soils,
shallow ground water, and cold temperatures).
The two degradates of toxicological concern, 3-chloroacrylic acid and 3-
chloroallyl alcohol, were also detected in ground water studies. For the current
assessment, EPA assumed equivalent ecotoxicological parameters; the
registrant is conducting confirmatory data for the environmental fate and
ecotoxicity of the degradates.
Risk Mitigation Since 1992, 1,3-D labels have been modified twice to include measures
to mitigate risks to workers and residents who live near treated fields. On
September 30, 1998, Dow AgroSciences again requested label modifications,
which are scheduled to appear on all 1,3-D labels no later than August 1, 1999.
The measures added since 1992, together with the new modifications, are
summarized below:
N Measures to mitigate worker risks - Lowered maximum rates (lowered by
30% to 65% depending on the crop); Deletion of selected use sites; Closed
loading requirements; Technology to minimize 1,3-D spillage during
application, Improved product stewardship materials, Coveralls over short-
sleeved shirt and short pants; Chemical-resistant gloves and footwear;
Chemical-resistant apron (for direct handlers), A respirator requirement for all
1,3-D handlers (except those in certain closed cabs); Restricted entry increased
to 5 days; Soil moisture and soil sealing requirements; Modified application
techniques.
N Measures to mitigate residential inhalation risks - 300' no-treatment buffer;
Lowered application rates (by 30% to 65% depending on the crop); Loading
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requirements; Technology to minimize 1,3-D spillage during application; Soil
moisture and soil sealing requirements; Modified application techniques.
N Measures to mitigate residential drinking water risks - Ground water
advisory; Prohibition of use in certain northern tier states (N.D., S.D., WI,
MN, N.Y., ME, N.H., VT, MA, UT, MT) with shallow ground water and
vulnerable soils (effective 8/1/99); 100' buffer between drinking water wells
and treated fields (effective 8/1/99); Prohibition of use in areas overlying karst
geology (effective 8/1/99).
Additional Data
Required
Product Labeling
Changes Required
The following additional generic studies for 1,3-D are being conducted
for EPA to confirm its regulatory assessments and conclusions. Because Dow
AgroSciences has already agreed to conduct these studies, there is no generic
DCI associated with this RED. For 1.3-D. Dow AgroSciences is conducting
the following studies: Freshwater fish early life stage; Freshwater aquatic
invertebrate life cycle; Estuarine/marine fish LC 50; Estuarine/marine
invertebrate LC50; Estuarine/marine invertebrate LC50; Tier I and Tier II
aquatic plant; Seed germination and seedling emergence; Vegetative vigor; Tier
I and Tier II terrestrial plants; Aerobic aquatic metabolism. For the degradates
(3-chloroacrylic acid and 3-chloroallyl alcohol). Dow AgroSciences is
conducting the following studies:
Acute oral-rat; Acute dermal toxicity (rabbit/rat); Primary eye irritation
(rabbit); Primary dermal irritation; dermal sensitization;a battery of
mutagenicity data; developmental toxicology; subchronic 90-day feeding study;
aquatic aerobic metabolism; adsorption/desorption; hydrolysis; vapor pressure;
Henry's Law Constant; acute fish toxicity; acute aquatic invertebrate toxicity;
Tier I and Tier II aquatic plant studies.
Dow AgroSciences is also conducting a tap water monitoring program
to assess whether levels of 1,3-D and/or its degradates of concern appear in
drinking water in areas with high 1,3-D use. The monitoring program is
designed so that risk reduction measures are initiated if 1,3-D and/or its
degradates are detected above the Office of Water's Health Advisory of 0.2
ppb.
The Agency also is requiring product-specific data including product
chemistry and acute toxicity studies, revised Confidential Statements of
Formula (CSFs), and revised labeling for reregi strati on.
Per the September 30, 1998 agreement with Dow AgroSciences, EPA
has contacted all end-use registrants of products containing 1,3-D to inform
them of the required label changes, which are to take effect August 1, 1999.
The new labels are to contain the additional label measures as follows:
Prohibitions in certain northern tier states (N.D., S.D., WI, MN, N.Y.,
ME, N.H., VT, MA, UT, MT) with vulnerable soils, prohibition of use in areas
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overlying karst geology and 100 foot no-treatment set-backs from drinking
water wells.
Regulatory
Conclusion
For More
Information
The use of 1,3-D, in accordance with pending label changes, will not
pose unreasonable risks or adverse effects to humans or the environment.
Therefore, all uses of these products are eligible for reregistration.
1,3-D products will be reregistered once the required confirmatory data,
required product-specific data, revised Confidential Statements of Formula,
and revised labeling are received and accepted by EPA. 1,3-D products which
also contain chloropicrin will not be reregistered until the active ingredient
chloropicrin is determined to be eligible for reregistration.
EPA is requesting public comments on the Reregistration Eligibility
Decision (RED) document for 1,3-D during a 60-day time period, as
announced in a Notice of Availability published in the Federal Register. To
obtain a copy of the RED document or to submit written comments, please
contact the Pesticide Docket, Public Response and Program Resources Branch,
Field Operations Division (7506C), Office of Pesticide Programs (OPP), US
EPA, Washington, DC 20460, telephone (703)305-5805.
Electronic copies of the RED and this fact sheet are available on the
Internet. See http://www.epa.gov/REDs.
Printed copies of the RED and fact sheet can be obtained from EPA's
National Center for Environmental Publications and Information
(EPA/NCEPI), PO Box 42419, Cincinnati, OH 45242-0419, telephone
(513)489-8190, fax (513)489-8695.
Following the comment period, the 1,3-D RED document will also be
available from the National Technical Information Service (NTIS), 5285 Port
Royal Road, Springfield, VA 22161, telephone (703) 605-6000 or (800)
553-6847.
For more information about EPA's pesticide reregistration program, the
1,3-D RED, or reregistration of individual products containing 1,3-D please
contact the Special Review and Reregistration Division (7508W), OPP, US
EPA, Washington, DC 20460, telephone (703)308-8000.
For information about the health effects of pesticides, or for assistance in
recognizing and managing pesticide poisoning symptoms, please contact the
National Pesticides Telecommunications Network (NPTN). Call toll-free
1-800-858-7378, between 9:30 am and 7:30 pm Eastern Standard Time,
Monday through Friday.
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