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An Ecological Risk Assessment for Insecticides Used in Adult
Mosquito Management
Ryan S. Davis, Robert K.D. Peterson, and
Paula A. Macedo
ABSTRACT
West Nile virus (WNV) has been a concern for people across the United
States since the disease was initially observed in the summer of 1999. Since
1999, WNV has caused the largest arboviral encephalitis epidemic in US
history. Vector control management programs have been intensively implemented
to control mosquitoes that carry WNV. Our deterministic ecological risk
assessment focused on 6 common mosquito adulticides used in vector control,
including 3 pyrethroids (d-phenothrin, resmethrin, and permethrin), pyrethrins,
and 2 organophosphates (malathion and naled). Piperonyl butoxide, a synergist
for the pyrethroids, was also assessed. Both aquatic and terrestrial
nontarget organisms were considered for acute and chronic exposures to the
adulticides. Tier I exposure estimates were derived from ISCST3 and AERMOD
for deposition and air concentrations affecting terrestrial organisms and
PRZM-EXAMS for standard pond concentrations affecting aquatic organisms.
Nontargets exposed to adulticides included small mammals, birds, as well as
aquatic vertebrates and invertebrates in a pond subject to receiving the
chemical via drift and runoff. Risk quotients were obtained by comparing
exposures to toxic endpoints. All risk quotients were low indicating that
risks to ecological receptors most likely were small.
Davis, R.S., R.K.D. Peterson, and P.A. Macedo. 2007. An ecological risk
assessment for insecticides used in adult mosquito management. Integrated
Environmental Assessment and Management 3: 373-382. (PDF)
Equine Risk Assessment for Insecticides Used in
Adult Mosquito Management
Jerome J.
Schleier III, Ryan S. Davis, Leslie M. Shama, Paula A. Macedo, and
Robert K. D. Peterson
ABSTRACT
Since West Nile virus (WNV) was introduced to New York City in 1999, it has
subsequently spread through the Americas, creating human and animal health risks.
Our equine risk assessment focused on three pyrethroid insecticides
(phenothrin, resmethrin, and permethrin), pyrethrins, and two organophosphate
insecticides (malathion and naled). Piperonyl butoxide, a synergist commonly
used in pyrethroids, was also assessed. The objective was to use
deterministic and probabilistic risk assessment methodologies to evaluate
health risks to horses from vector management tactics used for control of
adult mosquitoes. Our exposure estimates were derived from the Kenaga nomogram
for food deposition, AgDRIFT® for deposition onto soil and hair,
AERMOD for ambient air concentrations, and PRZM-EXAMS for water
concentrations. We used the risk quotient (RQ) method for our assessment with
the RQ level of concern (LOC) set at 1.0. RQs were determined by comparing
the exposure to no-observable-effect-levels. Acute deterministic RQs ranged
from 0.0004 for phenothrin to 0.2 for naled. Subchronic deterministic RQs
ranged from 0.001 for phenothrin to 0.6 for naled. The probabilistic assessment
revealed estimates of deterministic acute and subchronic RQs were highly
conservative. Our assessment revealed that risks to horses from adult
mosquito insecticides are low and not likely to exceed the LOC.
Schleier III, J. J., R. S. Davis, L. M. Shama, P. A. Macedo, and R. K. D.
Peterson. 2008. Equine risk assessment for insecticides used in adult
mosquito management. Human and Ecological Risk Assessment
14:
392-407. (PDF)
Regional
ecological risk assessment for the introduction of Gambusia affinis
(western mosquitofish) into Montana watersheds
Jerome J.
Schleier III, Sharlene E. Sing, and Robert K. D. Peterson
ABSTRACT
Qualitative risk assessment methodologies were used to assess the risk of
establishment and consequent impacts on native minnows and species of concern
(SOC) associated with the intentional or unintentional introduction of the
mosquito biological control agent, Gambusia affinis, to various
Montana watersheds. Gambusia affinis introductions for mosquito
control have been made throughout the world; some introductions have resulted
in deleterious effects on native species. We used average January water
temperatures, the presence of dams, and the presence of native minnows and
SOC to define endpoints for our assessment. Our results suggest that a
section of the Missouri River running between Wolf Creek and Landusky had the
highest overall risk score, which corresponds to the highest likelihood of
establishment and effects on native minnows and SOC. We also
demonstrate how rivers with the highest temperatures are not necessarily at
the highest risk of having deleterious effects on minnows and SOC;
conversely, these rivers were found to be at highest risk of a population of G.
affinis establishing.
Schleier III, J. J., S. E. Sing, and R. K. D. Peterson. 2008. Regional
ecological risk assessment for the introduction of Gambusia affinis
(western mosquitofish) into Montana watersheds. Biological Invasions 10:
1277-1287. (PDF)
Environmental
concentrations, fate, and risk assessment of pyrethrins and piperonyl
butoxide after aerial ultralow-volume applications for adult mosquito
management
Jerome J.
Schleier III, Robert K. D. Peterson, Paula A. Macedo, and David A. Brown
ABSTRACT
One of the most
effective ways of managing adult mosquitoes that vector human and animals
diseases is the use of ultralow-volume insecticides. Because of concerns
about the safety of the insecticides used for the management of adult
mosquitoes, we conducted an environmental fate and efficacy study in
Princeton and Colusa (both CA, USA) after aerial applications of pyrethrins
and piperonyl butoxide (PBO). One hour before application, PBO concentrations
in water were 0.008 and 0.2175 mg/L for Princeton and Colusa, respectively. One hour after
the spray event in Princeton, the average PBO concentrations were 0.0125 mg/cm2 on ground-deposition
pads and 0.1723 mg/L
in water samples, with concentrations decreasing significantly over time. One
hour after the spray event in Colusa, the average PBO concentrations were
0.0199 mg/cm2 on deposition pads
and 1.274 mg/L
in water samples, with concentrations decreasing significantly over time. A
significant time and location effect for both deposition pads and water
samples in Princeton and Colusa was observed (P < 0.001 and P =
0.014, respectively). Pyrethrins were not detected in nearly all ground and
water samples. One hour after application, mortality of Culex tarsalis and
Culex pipiens in sentinel cages was significantly higher than at the
control site for both locations (P < 0.001). Risk quotients for
aquatic surrogate species in Princeton and Colusa were 0.002 or less at 1 h
after application, which did not exceed the U.S. Environmental Protection
Agency risk quotient level of concern for endangered aquatic organisms of
0.05. Our results suggest that the amounts of pyrethrins and PBO deposited on
the ground and in water after aerial ULV insecticide applications are lower
than those estimated by previous exposure and risk assessments.
Schleier III, J.J., R.K.D.
Peterson, P.A. Macedo, and D.A. Brown. 2008. Environmental concentrations,
fate, and risk assessment of pyrethrins and piperonyl butoxide after aerial
ultralow-volume applications for adult mosquito management. Environmental
Toxicology and Chemistry 27: 1063-1068. (PDF)
Effects of single and multiple applications of mosquito
insecticides on non-target arthropods
Ryan S. Davis and Robert K. D. Peterson
ABSTRACT
Mosquito management plans have been implemented in the U.S. and globally to
manage mosquito vectors of West Nile Virus (WNV) and many other
diseases. However, there is public concern about ecological risks from
using insecticides to manage mosquitoes. Two studies were conducted during
the late summers of 2004 through 2006 at Benton Lake National Wildlife Refuge
near Great Falls, Montana. The first experiment was conducted in 2004
and 2005 to assess acute impacts of mosquito adulticides (permethrin and d-phenothrin)
and larvicides (Bacillus thuringiensis
israelensis and methoprene) on non-target aquatic and terrestrial arthropods
after a single application. The second experiment was conducted in 2005
and 2006 to assess longer term impacts of permethrin on non-target
terrestrial arthropods after multiple repeated applications. For aquatic
samples, in the first study, no overall treatment effects were observed
despite a potentially deleterious effect on amphipods on sample date 1 in
2004. During the same study, 1 of 54 responses had a significant
overall treatment effect for sticky card samples. Many of the responses
for sticky card samples suggested significant time effects and
time-by-treatment effects. Three response variables were associated with fewer
individuals present in the insecticide treated plots in a multivariate
analysis. For the multiple spray study conducted in 2005 and 2006, 6 of
the response variables collected via sticky cards exhibited significant
overall treatment effects, but none was associated with fewer individuals in
the insecticide treated plots. None of the responses collected using
sweep net sampling suggested overall treatment effects. Time and
time-by-treatment effects were prevalent in 2005, but no discernable pattern
was evident. In general, nearly all of the responses evaluated for either
study indicated few, if any, deleterious effects from insecticide
application.
Davis, R.S., and R.K.D. Peterson. 2008. Effects of single and multiple
applications of mosquito insecticides on non-target arthropods. Journal of
the American Mosquito Control Association 24: 270-280. (PDF)
Toxicity to non-target
insects after exposure to δ-phenothrin and resmethrin
Frank B. Antwi and Robert K. D. Peterson
ABSTRACT
BACKGROUND: The susceptibility of adult
house cricket, Acheta domesticus (L.), adult convergent lady beetle, Hippodamia
convergens (Guérin-Méneville), and larval fall armyworm, Spodoptera
frugiperda (J. E. Smith), to resmethrin and δ-phenothrin (synergized
with piperonyl butoxide (PBO)) was evaluated in a laboratory
bioassayprocedure.
RESULTS: The 1-d LC50 values for
resmethrin+PBO were 23.2, 32.08, and 307.18 ng/cm2 for house
cricket, convergent lady beetle, and fall armyworm, respectively. The 1-d
LC50 values for δ-phenothrin+PBO were 26.9,
74.91, and 228.57 ng/cm2 9 for house cricket, convergent lady
beetle, and fall armyworm, respectively. The regression relationship between
species mortality and concentration explained 51 to 81% of the variation for
resmethrin+PBO and 72 to 97% of the variation for δ-phenothrin+PBO. The LC50 values decreased with time for
these insecticides for all surrogate species. In terms of sensitivities among
the insects to resmethrin+PBO and δ-phenothrin+PBO,
house cricket was most sensitive, followed by convergent lady beetle, then fall
armyworm.
CONCLUSION: Our results indicate that
resmethrin+PBO was generally more toxic than δ-phenothrin+PBO.
Based on our results, the house cricket seems to be a good surrogate species
for estimating potential non-target terrestrial insect impacts from exposure
to pyrethroids used in public health applications.
Antwi, F.B., and R.K.D. Peterson. 2009. Toxicity to non-target insects after exposure to δ-phenothrin and resmethrin. Pest Management Science 65: 300-305.
(PDF)
Other Ecological Risk Assessments:
Maine Board of Pesticides Control - http://www.state.me.us/agriculture/pesticides/wnv/results3.htm
New York City Department of Health Adult Mosquito Control Programs - http://www.nyc.gov/html/doh/html/wnv/feis.shtml
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