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[ft-l] Mosquito repellent effectiveness study

FYI - below is a Mosquito repellent effectiveness study


Kent L. Wimmer, AICP
Florida National Scenic Trail Liaison
Florida Trail Association, Inc.
(850) 523-8576 (w)
(850) 523-8578 (fax)
(850) 386-8442 (h)
Mailing address:
USDA Forest Service
National Forests in Florida
325 John Knox Rd, F-100
Tallahassee, FL 32303-4160

----- Forwarded by Kent Wimmer/NONFS/USDAFS on 07/25/2002 01:38 PM -----
                    Beatty Gwen                                                                                    
                    <gfbeatty@yah        To:     gwen.beatty@dep.state.fl.us                                       
                    oo.com>              cc:                                                                       
                                         Subject:     Mosquito repellent effectiveness study                       
                    07:31 AM                                                                                       

By Susan Okie
Washington Post Staff Writer
Thursday, July 4, 2002; Page A01

Most insect repellents containing herbal oils are far
less effective than those containing DEET, a synthetic
chemical marketed since the 1950s, according to the
first study to scientifically compare a wide range of

Although the botanical repellents have attracted
chemical-wary consumers, the findings suggest that
DEET-containing repellents would be the best choice
for anyone seeking reliable protection from
mosquito-borne or tick-borne infections such as West
Nile virus or Lyme disease, said researcher Mark S.
Fradin, co-author of the study in today's issue of the
New England Journal of Medicine.

"If I was traveling to Africa and had to worry about
getting malaria or . . . yellow fever, I would want a
DEET-based product on my skin," said Fradin, a
dermatologist at the University of North Carolina.

Dozens of insect repellent creams, sprays and lotions
contain various concentrations of DEET, or
N,N-diethyl-3-methylbenzamide, which was developed in
1946 by the Department of Agriculture for use by the
military. Other products have active ingredients such
as citronella, oil of eucalyptus, peppermint oil,
soybean oil and IR3535, or
Ethyl-Butylacetylamino-propionate, a biopesticide
popular in Europe, but new to the United States, that
is chemically similar to the naturally occurring amino
acid alanine.

Scientists are not certain how insect repellents work
but theorize that they block the sensory receptors
that mosquitoes and other biting insects use to detect
carbon dioxide, lactic acid and other chemicals given
off by their human or animal targets.

Because no one had compared various repellents'
effectiveness, Fradin and entomologist Jonathan F. Day
of the University of Florida decided to test 17
nationally marketed products under laboratory
conditions. They asked 15 volunteers at the Florida
Medical Entomology Laboratory in Vero Beach to stick a
forearm coated with repellent into a cage containing
10 hungry female mosquitoes and see how much time
elapsed before the first bite.

Each repellent was tested three times on each subject,
to ensure that results were consistent and reliable.
The researchers used Aedes aegypti, a species of
mosquito that is the carrier of dengue fever and
yellow fever and that bites readily at any time of
day. Laboratory mosquitoes were disease-free.

Volunteers left their arms in the cages for a minute
at a time, then removed them and repeated the
procedure at regular intervals, said research
technician Nazar Hussain, who participated in the
study. "With some products, you would just put your
hand in there and they would start coming within five
seconds," he said.

Four skin lotions containing DEET in concentrations
ranging from 5 percent to 24 percent were among the
top six tested. Off! Deep Woods, a repellent
containing 23.8 percent DEET, provided the
longest-lasting protection: 302 minutes, on average.
The other DEET lotions worked for at least 89 minutes.
But wristbands, containing DEET or citronella, were
completely ineffective.

Two botanical repellents performed as well as some
DEET-based products. One, containing oil of eucalyptus
-- Repel Lemon Eucalyptus Lotion Insect Repellent,
which is also marketed as Fite Bite Plant-Based Insect
Repellent -- protected participants for an average of
120 minutes. Another, containing 2 percent soybean
oil, Bite Blocker for Kids, worked for an average of
95 minutes.

None of the other repellents tested -- containing
IR3535, citronella, or oils of peppermint, lemongrass,
geranium or cedar -- worked for longer than 22
minutes. Avon Skin-So-Soft Bath Oil, which Fradin said
he chose to test because of its "mythical status"
among some consumers, failed after 9.6 minutes, on

"The thing that surprised me was the gigantic
difference between the DEET-based repellents and, for
the most part, the non-DEET-based repellents," Fradin

Consumers have applied DEET more than 8 billion times
in the past 45 years, and its overall safety record is
excellent, researchers said. Fradin said there have
been about 50 cases of significant toxicity, generally
involving high doses or deliberate ingestion.

There have been seven reports of seizures in small
children who were exposed to excessive doses of DEET,
said Andrew Spielman, a professor of tropical medicine
at the Harvard School of Public Health who co-wrote a
commentary on the study. He said repellents containing
about 35 percent DEET provide mosquito protection
lasting overnight, and products with higher
concentrations offered no additional benefit. He
recommended that less-concentrated DEET products
should be used for children.

Spielman noted that Aedes aegypti is somewhat more
easily repelled than the deer ticks that carry Lyme
disease or the mosquito species that carry malaria and
West Nile virus. He added that the many gadgets
marketed to repel mosquitoes -- including lights,
coils and devices that produce sound or carbon dioxide
-- have not been scientifically evaluated.

Insect repellents are regulated by the Environmental
Protection Agency. Spielman said product labeling
typically provides little guidance for users. "It's
terribly important that there be some way for the
consumer to understand how much of the material should
be applied" and how often, he said.

EPA spokesman Dave Deegan said the agency is revising
its guidelines for the labeling of repellents, as well
as requirements on how much proof of effectiveness
manufacturers must provide.

"We were really happy to see this study," said Susan
E. Little of the Consumer Specialty Products
Association, which represents companies that
manufacture many of the repellents tested. She
acknowledged that labeling is frequently vague. She
said the industry "would be more than happy if the EPA
came up with a consistent, across-the-board labeling
procedure for all products, including the botanicals
and the naturals."

 2002 The Washington Post Company

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