Chapters 1 - U.S. Fish and Wildlife Service

Chapter 5
The USEPA (2008b) describes the environmental fate and transport of phenothrin as follows:
Phenothrin’s moderate persistence in surface soils, its relatively high affinity for binding to
soils, and low solubility indicate a high potential for the chemical to enter surface waters
during runoff events that contribute to soil erosion during the weeks following an application
event. Phenothrin could also reach surface waters as the result of spray drift following an
application with ULV [ultra-low volume] equipment. Its low leaching potential, however, also
means that it is likely to remain immobile once it binds to soil sediments. Furthermore, it is
unlikely to seep into groundwater supplies and cause contamination. Even though
phenothrin is likely to undergo photolysis in water, its high affinity for binding to particulate
matter make photolysis less likely to happen, except during the brief period in which the
chemical is suspended in water without binding to sediment. The photolysis of phenothrin is
expected to occur in shallow waters or in the upper levels of the water column where sunlight
is able to penetrate. Phenothrin’s large binding affinity for sediment or suspended solids in
the water column also indicate a high potential for continued persistence in aquatic systems .
. . Leaching does not appear to be a significant route of dissipation for phenothrin . . .
Unbound phenothrin is unlikely to remain free in the water column for any significant
period of time. If multiple applications are made, however, phenothrin bound to sediment and
free in the water column could accumulate significantly in aquatic ecosystems. Acute and
chronic exposure risks from phenothrin exist to organisms living in the water column and in
the benthic sediments lining water bodies.
Piperonyl butoxide, the other active ingredient in Anvil products, is a synergist that is typically
combined with sumithrin. It enhances the effectiveness of sumithrin by inhibiting the metabolism
of the pyrethroid by mosquitoes. It is not expected to adsorb to sediment, therefore, it would be
expected to leach from soil and be released in water. It may photodegrade in surface waters, but
its degradation in the aquatic environment is currently unknown.
No other adulticides, including the organophosphates malathion and naled, are currently proposed
for use on the Refuge.
To minimize or avoid adverse effects to water quality related to all forms of mosquito control, the
following BMPs are required to be implemented in accordance with the Mosquito Management
Plan (Appendix D):
Where mosquito control is necessary, use the most effective means that pose the
lowest risk to abiotic and biotic resources;
Apply pesticides only in specific, discrete areas where monitoring data justify its use.
Use of drift retardants (thickeners designed to minimize the formation of droplets
smaller than 150 microns), which have also been evaluated through the PUP review
process, to reduce aerial drift of pesticides;
Employ wind speed restrictions on spraying;
Any application of adulticides should occur at an ultra-low volume (lowest possible
dilution rate that is still effective);
All adulticide applications should be conducted from the roads that extend along the
northern, eastern, and western perimeter of the Refuge and only when meteorological
conditions are stable and favorable with a consistent wind greater than three miles per
hour from the south or southwest; and
Any application of adulticide should be limited in terms of number of applications per
season and shall only occur when a public health emergency has been declared, and the
use of an adulticide shall be coupled with larvicide treatment to prevent a second adult
emergence.
5-20 Seal Beach National Wildlife Refuge