Document ID: EPA-HQ-OPP-2004-0385-0122
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-02-27T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

                                                                     
OFFICE OF 

                                                                 
PREVENTION, PESTICIDES AND

                                                                   
TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 								PC Code 	109701

								DP Barcode	D333756 

MEMORANDUM

DATE:	November 30, 2006

SUBJECT:	Response to Permethrin RED Public Comments, EFED Ecological
Risk Assessment and Mitigation 

TO:		Jacqueline Guerry, Chemical Review Manager

		Michael Goodis, Branch Chief

		Reregistration Branch

		Special Review and Reregistration Division (7508P)

FROM:	José Luis Meléndez, Chemist

		Michael Hoffmann, Biologist

		Faruque Khan, Ph.D., Environmental Scientist

		Environmental Risk Branch V

		Environmental Fate and Effects Division

THROUGH:	Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

The registrants of permethrin, and several interested parties, provided
comments on the Draft of the Reregistration Eligibility Decision
document (RED) for the chemical.  The purpose of this memorandum is to
address those comments related to environmental fate and effects, as
they relate to the Environmental Fate and Effects Division (EFED).

EFED used an outline format, with the comments generally summarized by
topic, and followed by the EFED’s response in bolded letters.  The
comments were sometimes written verbatim, and other times they were
summarized, as needed.



The RED fails to consider the synergistic effects of permethrin used in
conjunction with other chemicals (e.g., DEET) or formulated with PBO.

It is the Agency’s approach to perform risk assessments on a
case-by-case basis for individual active ingredients. However, EFED is
aware of the potential for increased toxicity of permethrin when
formulated with synergists such as PBO.  When substantive data on
formulated products containing synergists were available for pyrethrins
and resmethrin, the potential for synergistic effects was evaluated and
often showed increased toxicity; however, this issue could not be
addressed in the permethrin RED due to the limited toxicity data
available for the formulated products containing PBO.  Therefore,
toxicity data for formulated products will now be requested as a RED
follow up, and will be evaluated and incorporated in the Registration
Review process for permethrin.

Public health-

AMCA recommends a standard of Dv0.5 =60 microns and Dv0.9=100 microns
for aerial applications made at less than 200’ above ground elevation.
 Several of the new efficient spray systems placed in use to
specifically eliminate the production of large drops produce a Dv0.9
greater than 80 microns and as high as 95 microns.  The environmental
risk assessment does not provide any justification for the extremely low
Dv0.9 that is proposed.  The EFED final Risk Assessment used a Dv0.5 ~
50 microns and Dv0.9 ~ 115 microns; and supplemental runs with Dv0.5 ~
60 microns and Dv0.9 ~ 95 microns

≤60 microns and Dv0.9≤100 microns).  The percentage drift
corresponding to this case was 7.1%.  PRZM/EXAMS runs were performed and
the RQs were calculated in the risk assessment for this case.  The EFED
believes that the AMCA’s suggested droplet will be similar to the
droplets modeled in the risk assessment.

An alternative droplet size should be made for higher elevations. 
Dv0.5=70 microns and Dv0.9=145 microns.  In AMCA’s survey, 17% of
applicators cannot meet the 100 micron Dv0.9 standard.

The EFED conducted modeling of the above mentioned conditions (droplet
size of Dv0.5=70.89 microns and Dv0.9=145.96 microns, and a relative
span of 1.73), and found that the exposure (the value of spray drift
towards the standard pond), for a droplet size of Dv0.5~70 microns and
Dv0.9~145 microns and a boom height of 200 ft, is smaller than the
exposure obtained in the EFED risk assessment for mosquito adulticide,
with Dv0.5~60 microns, Dv0.9~95 microns and a boom height of 100 ft
(7.1% vs. 2.9%).  Based on the results of these models, the EFED
believes that qualitatively, despite the fact that EECs and RQs were not
calculated, they would be smaller for the larger droplets at the higher
altitudes or compared to those modeled in the environmental risk
assessment. 

The commentator recommends 50 ground based applications (Florida only)
at a maximum application rate of 0.007 lb a.i./day (or 0.35 lb
a.i./year).

This comment is related to label changes.  It is deferred to SRRD.  For
information only, for SRRD, to allow 50 applications per year at up to
0.007 lb a.i./A means to increase the proposed application rate of 0.18
lb a.i./A/year to 0.35 lb a.i./A/year.  Such high yearly rates would be
needed in emergency situations, and the Agency provides for such
situations, with Special Section 18 Emergency Exemptions.

Remove the 300 ft maximum boom height requirement.  Currently
applications are also made at night, and the safety becomes an issue
with antennas, canopy, buildings, etc.

This comment is related to label changes.  It is deferred to SRRD.  For
information only, for SRRD, modeling shows that, using droplets with
Dv0.5~70 microns, and Dv0.9~145 microns, at 300 ft boom height, the
airborne drift could reach levels near 95%.  The American Mosquito
Control Association indicated in its comments, that a recent survey of
40 mosquito control public agencies across the country, support the boom
height (maximum and minimum) used in the risk assessment.  Furthermore,
this is a voluntary maximum height put in place by the registrants.  A
wide range of up to 300 ft appears to be appropriate.

Recent survey of mosquito control districts supports the boom height
(maximum and minimum) and the application rates used in the risk
assessment.

The EFED risk assessment was performed taking into consideration
comments from the American Mosquito Control Association.  The assessment
included low end boom heights recommended for helicopter and for
aircraft, that is, the most conservative practical boom heights.

EFEDs AGDISP model does not consider various canopy parameters, and
therefore, over estimates the deposition both within and downwind of the
spray area.  Emphasis should be given to situations where the spray zone
and/or the downwind area consist largely or exclusively of vegetated
wetlands, where pesticide deposition would be significantly mitigated by
foliar interception.

EFED considered the most conservative scenario in this screening level
risk assessment.  However, preliminary runs performed by the EFED with
various canopy heights “for information only,” show that for small
canopies, the level of drift decreases somewhat, while with higher
canopies, the levels of drift towards an adjacent pond, increases. 
These results suggest that foliar interception by high canopy did not
reflect lower pesticide deposition as the AMCA suggests.  While it is
true that in swamps and marshes, the (emergent) vegetation is typically
short, this chemical is also applied on moderately to highly vegetated
areas.  In future assessments, the EFED may take this parameter into
consideration too.

Down-the-Drain Assessment- 

The model relied on multiple assumptions and input parameters.  More
information is needed regarding assumptions, input parameters, and
validation of this model. 

The only input parameters in the “down-the-drain” module of E-FAST
are two: (a)ProdVol = Production Volume of the chemical (permethrin) in
Kg/year, and (b)WWT = fraction of the chemical removed during wastewater
treatment.  For both input parameters, real data was used (as opposed to
modeling or estimations); that is, real production volume data and three
levels of removal from real treatment plants were used.  Plain
assumptions and limitations were described in the EFED risk assessment
for this screening model; however, for additional information on the
model, it has a manual [“Exposure and Fate Assessment Screening Tool
(E-FAST) Beta Version Documentation Manual,” Prepared for the USEPA,
Office of Pollution Prevention and Toxics, Exposure Assessment Branch;
Prepared by Versar Inc., Springfield, VA; 12/31/1999] 

Improve methodology to recognize that many sewage treatment plants are
not afforded significant dilution credit for their discharges.  OW can
assist OPP with development of an improved wastewater discharge modeling
methodology.  OW can also provide OPP information on how sewage sludge
are managed to be included in the assessment for potential hazard from
sewage discharge of pesticides. 

The “down-the-drain” model was developed and maintained by the
OPPTS, the EFED will forward this comment to them for their
consideration, for further research, and future development of the
model.

The down-the-drain assessment did not consider high-end mass discharge
rate, such as a concentrated discharge of permethrin into sewer water
after the outbreak of head lice in school.

The “down-the-drain” model was developed and maintained by the
OPPTS, the EFED will forward this comment to them for their
consideration, for further research, and future development of the
model.

The total production number of permethrin used on products in the
down-the-drain assessment was drastically reduced from the prelimary
risk assessment and the final risk assessment. 

Why did the number decrease?

The Agency received updated information on the kilograms of active
ingredient used over the counter, and as prescription drugs, from the
FDA on 02/22/06, which was incorporated in the revised risk assessment. 

Request to share the CBI product information with POTWs and state
environmental agencies, which by law, are CBI and unpublished marketing
data confidential.  

FIFRA CBI data (or FIFRA Confidential Business Information) cannot be
shared with POTWs and state environmental agencies. State, county and
local governments are not authorized access to FIFRA CBI.  The EPA
Administrator may release certain FIFRA CBI if it is determined that
disclosure is needed to prevent injury or “imminent harm” to the
public or the environment.  The Agency cannot disclose detailed
information, other than what was provided in the review; however, the
EFED utilized all sources of permethrin of which information was
available. 

There is concern because, according to the assessment, “aquatic
organisms appear to be at acute risk from exposure in surface waters
containing permethrin from wastewaters” (citation from the EFED RED
Chapter).  Why did the Agency propose to reregister indoor uses without
mitigation action?

The EFED defers the response to this comment to the SRRD.

Endangered species and other concerns-

Permethrin is highly toxic to fish and other aquatic organisms,
including endangered species. In late June, an estimated 100,000 to
300,000 black crappie fish dies in Clear lake in Waseca County,
Minnesota and water samples showed the presence of permethrin. A very
recent study of pesticides in bodies of water in agriculture-dominated
Central Valley in California found high levels of synthetic pyrethroids
in stream sediments-levels high enough that they were toxic to
freshwater bottom dwellers in almost 50% of the sampled locations.  In
addition, permethrin is likely to adhere to the walls of test vials, and
EPA should consider the effects this will have on the perceived
toxicity.

The EFED recognizes and has acknowledged in the RED that permethrin is
highly toxic to fish and aquatic organisms, including endangered
species.  Although there was an initial screening in the RED of the
potential effects and risk to endangered species and groundwork was
laid, a more comprehensive assessment for endangered species will be
performed in Registration Review as additional data become available and
technical approaches are developed. 

The Agency is also aware of the mentioned incident in Minnesota, the
study in Central Valley, and the hydrophobic nature of permethrin and
other pyrethroids.  However, at the time the RED was written, the case
was not closed on the fish kill incident and the Central Valley Study
was not available to EFED; therefore, neither could be discussed
thoroughly in the assessment. In addition, since the RED was written,
the fish kill incident case has been resolved and the active ingredient
involved was pyrethrins, not permethrin.  Regarding the hydrophobic
nature of permethrin and other pyrethroids, it should be noted that the
Agency typically relies on toxicity endpoints that are based on
time-weighted averages of measured test concentrations when available
due to the compounds’ affinity for binding to organic matter.  

EPA failed to fully consider the impacts on agriculture because
permethrin is highly toxic to bees and other beneficial insects.

See Response to General Comment 1a.  

General Comments:

Mosquito adulticides:

Being sprayed on crops, it is impacted because it kills pollinators,
without them, crops would not produce harvests and wild plant
communities would decline.

The EPA recognizes and has acknowledged in the RED that permethrin is
highly toxic to bees and beneficial insects.  Although currently the
Agency does not assess quantitative risk to non-target beneficial
insects, the EPA has qualitatively identified in its assessment the
potential for risk to bees and beneficial insects if exposure to
permethrin occurs (please refer to the Risk Characterization Section of
the Environmental Fate and Effects Division’s (EFED) Screening-level
Environmental Risk Assessment for Permethrin).  EFED also concurs that
if pollinators of crops and wild plants are exposed to permethrin, there
is the potential for indirect effects to the populations/communities of
plants dependent upon these organisms.  However, the Agency does not
currently have an established approach for quantitatively evaluating the
potential impacts of decreased pollinators on agriculture, and the risk
conclusions of the RED remain unchanged.

Impacts mosquitoes natural predators such as Dragonflies

EFED acknowledges that there is the potential for direct negative
effects to beneficial non-target organisms that feed on mosquitoes
resulting from permethrin use. Although, the risk of direct effects to
various taxonomic groups that may feed on mosquitoes was assessed (e.g.,
birds, fish, aquatic invertebrates), the Agency does not currently have
any established approach for quantitatively evaluating the indirect
effects to mosquito populations and the overall risk conclusions remain
unchanged.

Increased risk of West Nile Encephalitis from sprays due to immune
systems suppression: According to the commentator “Adulticide
chemicals may be putting mosquitoes that are sprayed, but not killed,
into an immuno-compromised state, thereby allowing them to accumulate
and spread more West Nile virus than healthy mosquitoes.  Pesticide
researcher Richard Pressinger has theorized that the chemicals cause
subtle genetic damage in the mosquito population, increasing the number
of mosquitoes with genetic flaws which could, in theory, allow the
encephalitis virus to take hold and grow more rapidly.”

The EFED defers the response to this comment to the SRRD/CDC.

Spraying is ineffective:  The commentator indicates that “The U.S.
Center for Disease Control and other experts say that spraying or
fogging is the least-effective means for slowing the spread of
WNV-carrying mosquitoes.”  They also indicated that mosquitocides are
only 10% effective, and that the mosquito lifecycle is two weeks, with
the need of constant applications.

The EFED defers the response to this comment to the SRRD.  The efficacy
of a product is a matter dealt by the SRRD.

Aerial spray contributes to the development of “super mosquitoes”
resistant to pesticides and other alternatives.  According to the
commentator, mosquitoes that survive an application are likely to
develop resistance to it; later on, higher amounts of insecticides are
required.  Furthermore, over several years of applications, now
mosquitoes have a larger capacity to transmit the West Nile Virus (WNV).

The EFED defers the response to this comment to the SRRD/CDC.

Health effects to vulnerable groups in the population (children,
pregnant women, elderly, chemical sensitive and inmuno-suppressed
individuals, and people suffering from asthma.)

The EFED defers the response to this comment to the HED.

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 Since some species of fish feed on mosquito larvae, this is doubly
counterproductive.”

The EFED has acknowledged in its risk assessment that the use of
permethrin poses potential direct and indirect risks to fish and
non-target insects. 

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