Note to Reader

Endosulfan: Request for Additional Information on 

Usage and Availability of Alternatives 

November 16, 2007

Dear Reader:

The purpose of this document is two-fold:  1) to summarize the updated
human health and ecological effects risk assessments for endosulfan,
and: 2) to solicit public comment on EPA’s analysis of endosulfan
usage information since the 2002 Reregistration Eligibility Decision
(RED) and its preliminary determinations regarding endosulfan’s
importance to growers and availability of alternatives.  The updated
human health and ecological effects risk assessments and updated
usage/alternatives information is being released for a 60-day public
comment period, running from November 16, 2007 to January 16, 2008.

Background

Endosulfan is a broad spectrum contact insecticide and acaricide
registered for use on a wide variety of vegetables, fruits, cereal
grains, and cotton, as well as ornamental shrubs, trees, vines, and
ornamentals for use in commercial agricultural settings.  Endosulfan is
formulated as a liquid emulsifiable concentrate and a wettable powder. 
There are currently three endosulfan registrants: Makhteshim-Agan of
North America, Makheteshim Chemical Works, Ltd., and Drexel Chemical
Company.  Bayer CropScience recently cancelled all U.S. registrations of
endosulfan products, effective July 16, 2007. 

In its 2002 Reregistration Eligibility Decision, EPA identified use of
endosulfan to pose dietary, occupational, and ecological risks of
concern.  However, the Agency determined that these risks could likely
be mitigated to levels below concern through the deletion of use on five
crops (grapes, pecans, spinach, succulent peas, succulent beans) and
changes to pesticide labeling and formulation.  Accordingly, EPA
concluded that endosulfan was eligible for reregistration provided that:
(1) additional required data were submitted by the registrants
confirming this decision; and (2) the risk mitigation measures outlined
in the RED were adopted, and label amendments made to reflect these
measures.  

Human Health Assessment

EPA’s updated assessment of the potential human health effects of
endosulfan is based on the review of a recently submitted developmental
neurotoxicity (DNT) study, which was required in the 2002 Endosulfan
RED.  

Occupational Risks

Based on the toxicological effects observed in the DNT, the Agency
selected a different endpoint than the one used in the 2002 RED
assessment to evaluate short- and intermediate-term dermal exposure for
occupational handlers.  The updated occupational assessment for
endosulfan indicates short- and intermediate-term risks for mixers,
loaders, and applicators for the majority of uses, even with maximum
Personal Protective Equipment (PPE) and engineering controls.  In
addition, postapplication risks are such that the majority of reentry
intervals (REIs) would need to be extended by several to multiple days.

Dietary Risks

In the 2002 RED assessment, the Agency retained a 10x FQPA safety factor
for the dietary assessment due to database uncertainties.  As the
post-RED submission and review of a developmental neurotoxicity study
(DNT) and a subchronic neurotoxicity study address residual
uncertainties for pre- and /or post-natal toxicity, EPA reduced the FQPA
safety factor in its updated assessment from 10x to 1x.  Based on the
new assessment, the combined dietary (food and drinking water) does not
exceed the Agency’s level of concern for both acute and chronic
exposures.

One area of uncertainty, however, regarding the Agency’s assessment of
dietary risk is the potentially unique risk-exposure scenario for
indigenous, subsistence fishers/hunters because of the uncertainty in
the potential for endosulfan to bioaccumulate.  As specific residue data
in/on commodities consumed in subsistence diets (e.g., fish, polar bear,
walrus, caribou, moose) are not available for endosulfan, risk estimates
for these population subgroups have not been evaluated by the Agency. 
However, based upon the detection of endosulfan in areas distant from
use sites, such as the Arctic, and its potential to persist and
bioaccumulate, the Agency has concerns for dietary exposure of
indigenous populations to endosulfan.

Residential Risks

As there are no residential uses of endosulfan, the Agency did not
include residential risks in its aggregate assessment of this chemical.

Ecological Risks

EPA has updated the ecological effects assessment for endosulfan based
on studies required in the 2002 RED and on additional information drawn
from the published literature on endosulfan bioaccumulation,
persistence, monitoring and transport, and ecological incidents.  In
general, the new information suggests that parent endosulfan and its
sulfate degradate may pose greater risks than the 2002 RED outlined. 
Additional studies on the sulfate degradate of endosulfan demonstrate
its equal toxicity and increased persistence as compared to endosulfan
parent.  While the parent may readily undergo degradation under some
environmental conditions, the sulfate degradate is persistent and
represents an additional source for total endosulfan residues to enter
aquatic and terrestrial food chains.  While endosulfan is not expected
to biomagnify appreciably in aquatic food webs, the compound does
bioconcentrate in aquatic organisms to a significant extent.  Also,
there is direct evidence (measured residues) that endosulfan
bioaccumulates in terrestrial systems and indirect evidence (modeling)
that endosulfan has a significant potential to biomagnify in certain
terrestrial food webs. 

EPA also continues to be concerned about endosulfan’s volatility and
its ability to migrate to sites distant from use areas.  Endosulfan has
been found to migrate over long distances through various environmental
media such as air, water, and sediment. The occurrence of endosulfan in
regions such as the Great Lakes, the Arctic, and mountainous areas is
well documented.  Once endosulfan is applied to crops, it can either
persist in soil or dissipate from the site of application through
several physical, chemical, and biological processes.   Recent studies
suggest that residues of endosulfan volatilize and continue to recycle
in the global system through a process of migration and dry/wet
deposition in the northern Hemisphere. 

In addition to EPA updating its work on endosulfan, Canada, California,
and international bodies are reviewing issues associated with
endosulfan.  EPA and its regulatory partners, Canada Pest Management
Regulatory Agency (PMRA) and California Department of Pesticide
Regulation (DPR), have been keeping each other informed on recent
developments in their assessments of endosulfan.  On October 16, 2007,
Canada’s PMRA released a Preliminary Risk and Value Assessment of
Endosulfan for a 60-day comment period.  In this Re-evaluation Note,
PMRA has proposed that endosulfan meets the four criteria for a Track 1
substance under the Toxic Substances Management Policy, which calls for
virtual elimination of these substances.  California’s DPR released a
draft risk assessment in July 2007 for public comment.  The European
Commission (EC) has proposed that endosulfan be evaluated in a more
detailed risk assessment to determine whether it should be listed as a
Persistent Organic Pollutant (POP) under the Stockholm Convention on
POPs, which prohibits most production and use of listed substances on a
global basis.  In addition, all uses of endosulfan are to be cancelled
in the European Union for environmental risk concerns by the end of
2007.  

The Agency anticipates working with national and international
authorities to further characterize endosulfan in terms of persistence,
bioaccumulation potential, toxicity, and the potential for long range
transport.

Usage and Alternatives

EPA has updated its endosulfan usage information since the 2002 RED and
has made preliminary determinations regarding endosulfan’s importance
to growers and the availability of alternatives.  In general, endosulfan
appears to provide low benefits for producers of many crops and moderate
to high benefits for some crops in certain regions of the country.  

Questions

The Agency is providing the following questions to help the public in
preparing comments.  Please provide as much detail and documentation in
your comments as possible.

(1) Do you agree with the Agency’s selection of a new endpoint to
evaluate short- and intermediate-term dermal exposure for occupational
handlers in the updated human health assessment?  If not, why not? 
Please explain.

(2) Do you agree with the Agency’s reduction of the FQPA safety factor
from 10x to 1x in the updated human health assessment?  If not, why not?
 Please explain.

(3) What information is the public aware of regarding endosulfan
residues in/on commodities consumed by subsistence fishers/hunters? 
Please provide data and/or sources.

(4) What additional information on endosulfan is the public aware of
regarding bioaccumulation, persistence, toxicity, monitoring and
transport, and ecological incidents?

(5) What additional endosulfan usage information is the public aware of
since the 2002 RED?

(6) What additional alternatives are available for the pests targeted by
endosulfan? 

(7)  For registered uses not addressed in the Agency’s usage and
alternatives document, what are the pests targeted by endosulfan and
what alternatives are available for their control?

(8) What effect would the extended REIs have on the ability of growers
to perform the necessary postapplication activities for registered uses?

(9) For which crops, against which pests, and in which regions is use of
endosulfan critical and why?

 

