Mosquito
Aerial Spray Programs Endanger Human Health, Don’t Work
Aerial
mosquito spraying over populated areas this year by the local
mosquito control district used a more hazardous pesticide than
in previous years. While
there is no
scientific evidence that the spray is effective in
stopping the spread of West Nile virus (WNv), there is
evidence that the spraying
endangers health.
The more
dangerous pesticide used this year is an organophosphate. Similar to
chemical warfare agents produced during World War II, this
chemical adversely affects the human nervous system even at
low exposure levels, and ingredients
are on California’s Proposition
65 list of chemicals known
to
cause cancer.
The district justifies its spray protocol by such factors as the number of WNv-infected mosquitoes and birds, but this is a rare human disease. According to the Centers for Disease Control (CDC) only a tiny fraction of the human population becomes infected, and only 1 in 150 of those infected develop serious symptoms. The total serious human case count for Sacramento and Yolo counties for 2011 and 2012 is 1.
It is well
established that it is safer and much more effective to target
mosquito larvae before they become biting adults. Although the
district uses mosquito fish to some extent, there are other
effective larvae predators, such as nematodes
(small roundworms) that establish populations for ongoing
control and are effective from the very beginning of the
mosquito season.
These nematodes
infect only mosquito larvae so they pose no risk to human
health or the environment. Even more effective
against the supposed vectors of WNv is a mosquito fungus that
has exhibited 95% mosquito mortality and has been shown
effective in areas where mosquito fish cannot be used.
Both
peer-reviewed scientific research and mathematical modeling
demonstrate that aerial spraying is ineffective for WNv
control. Cornell
University entomologist David
Pimentel writes: “Widespread ULV [ultra-low volume]
spraying from ground equipment or aircraft for control of
mosquitoes and West Nile virus is relatively ineffective,
costly, and has been associated with environmental and
public health risks.”
Also, a Harvard
School of Public Health study concludes: “We find that
ULV applications of resmethrin had little or no impact on the
Culex vectors of WNv, even at maximum permitted rates of
application.”
A
model widely used for infectious diseases produced two
important conclusions when applied
to WNv transmission: 1) early, sufficient, treatment
for mosquito larvae is the key to control; 2) treatment
aimed at adults later in the season cannot possibly
eradicate the virus, particularly with the protocol the
district uses.
Justifications
the district has used to support its aggressive aerial spray
program have been very weak at best. In 2005 the district
cited a slide show about treatments in Fort Collins, Colorado
and a report from a Louisiana parish, but they revealed
nothing about the efficacy of spraying. In fact, the Fort
Collins spraying, when viewed in context, demonstrates the ineffectiveness of
spraying: nearby Boulder did not spray and had better results
than surrounding communities that sprayed.
The district
cites a purportedly
peer-reviewed paper from the CDC website on the efficacy
of its 2005 Sacramento spraying; however, the authors did
not provide a single review in response to a Public
Records Act request. Furthermore, that spray event
was not set up as a study and parameters were adjusted after
the fact. Additional
flaws include: human infection locations were based on a false
assumption and
the spray was halted for 8 consecutive days by wind, which inhibits mosquito flight and
biting behavior. The wind is not even
mentioned in the report. No
valid conclusions can be drawn, yet officials continue to
cite this report as evidence of efficacy.
The price tag for this ineffective
program is staggering. For example, the district reports
that the cost
of the 2005 aerial spraying was $701,790.
The
district must base its policies on sound science and recognize
that its current treatments pose a greater risk to public
health than the virus against which the spraying allegedly
protects.
For references for these points and
further discussion, see
http://www.stopwestnilesprayingnow.org/.
Kim Glazzard, Organic
Sacramento
Samantha McCarthy,
Better Urban Green Strategies
Jack Milton, Stop West
Nile Spraying Now
Asael Sala, Pesticide
Watch