Petition Facts/References

Santa Clara County Board of Supervisors:
STOP unnecessary, ineffective and toxic mosquito pesticide fogging!

Santa Clara County claims pesticide fogging is necessary to control mosquitoes that carry West Nile Virus and that the pesticides used are “generally harmless in Ultra Low Volume applications”. However, research shows pesticide fogging is unnecessary, proven to be ineffective, toxic to people, bees, and the environment, and costly.
There are safer and more effective ways to control mosquitoes without poisoning us and the environment.
For details, more information, maps and references:

(photo credit: Eddie Ledesma/ Mercury Staff Archives)

The Facts and Resources to back up the petition statements: 

1. There are only 3 human cases of West Nile Virus in Santa Clara County as of August 19, 2014.  There is NO emergency so fogging is NOT necessary.  (Latest West Nile Virus Activity in California, 2014)  Pesticide fogging is supposed to be a “last resort” in a human epidemic of WNV, however it has now become an often twice weekly poisoning. Vector claims high rates of infected dead birds indicate WNV infection is rising, however they are not testing the birds for cause of death, leaving no indication of what is actually killing them. The 4th highest cause of bird deaths is due to pesticide poisoning, not WNV.  (Causes of Bird Mortality, 2010)  Also, only 1% of mosquitoes caught are infected with WNV, so the chances of infection spreading to humans is VERY LOW compared with the toxicity of fogging for people and the environment.

2. Mosquito fogging is shown INEFFECTIVE against the spread of West Nile Virus.  (Reddy, 2006). The pesticide kills only a small percentage of adult mosquitoes who actually fly into the fog. The others who are hiding in the bushes will survive and lay more eggs. The larvae in standing water around homes will then hatch the next day and the cycle starts all over again. Culex mosquitoes (the type that often carry WNV), are active at dawn and dusk. However, Vector’s fogging takes place 11PM-2AM, not when mosquitoes are actually active and likely to fly into the fog. The continued use of Pyrethroids, the synthetic nerve toxin in fogging pesticides, creates pesticide resistance in surviving mosquitoes (Marcombe, 2011).  The end result of frequent fogging will be the need for an even stronger, more toxic pesticide if a mosquito-born disease emergency should occur.  Also, the mosquito population actually continues to increase all summer.  So fogging is NOT effective at controlling mosquitoes.

3. The County’s only source for safety testing is the EPA and the manufacturer, per the manager of at the County Dept. of Environmental Health during a conversation.  When it comes to the concern for our public health, relying on one biased source for our safety is irresponsible and could potentially be very harmful. The MSDS (Material Safety Data Sheet), shows toxicity from only rat and mouse experiments.  It also states that the pesticide is known to be toxic to bees and aquatic life. The county assumes this pesticide is safe for humans based on a false belief that mammals will easily detoxify the chemical (Etofenprox). This is not true in all cases.  It is known that babies do not have fully functioning livers and when exposed to pyrethroids, during gestation or after birth, they do not have the ability to detoxify the toxin properly potentially causing serious health problems.

4. The pesticide used for fogging is Zenivex E4.  The active ingredient is Etofenprox, a pyrethroid, which is a synthetic nerve toxin. Pyrethroids are designed to be a more potent and longer lasting version of pyrethrin, a natural toxin derived from specific types of chrysanthemums. Most mammals might detoxify Etofenprox when in isolation, however, we live in a pool of chemicals and many people’s livers do not function as well as they should. This causes the chemical to remain in their bodies. Studies show that the pyrethroid DOES accumulate in the body, will pass from mother to child via placenta and milk, and disrupts hormones.  (Alonso MB, et. al., 2012)

5. Zenivex E4 is TOXIC to bees and other beneficial insects. The toxin has a half-life (the time it takes for half of it to degrade) of 4.5 days when on the ground. It takes three half-lives to clear ⅞ of it. This means the pyrethroid (nerve toxin) will still be toxic for over two weeks or more after the fogging takes place.  This is enough to be a sub-lethal dose for bees. Not only are we killing off bees, the primary means for pollinating our food supply, but fogging also kills a variety of beneficial insects that are natural predators of mosquitoes, disturbing the balance of our ecosystem.

6. Vector Control gets over $6.8 million from OUR parcel taxes EVERY YEAR.  Instead of toxic pesticide fogging, Vector should spend our taxes on educating residents about safe and ecologically sound ways to control mosquito populations.

7. Safe Alternatives DO exist! Clearing standing water from our yards every week has been proven to decrease mosquito numbers. Offering free mosquito fish for contained ponds and unused pools is another option. Our county’s first response has been with poison, however, there ARE more healthy, non toxic, options out there if we take the time to investigate them. Cities who have already elected to use safer methods of mosquito abatement have controlled mosquitoes and West Nile Virus with the same level of success as toxic fogging. These cities include Lyndhurst, OH, Washington, DC, York County, VA, Dallas, TX, Ft. Worth, TX, Nassau County, NY, Marblehead, MA, Lane County, OR, Seattle, WA, and Boulder, CO.

“Latest West Nile Virus Activity in California,” last modified July 30, 2014,  California Department of Public Health West Nile Virus Website,

“Causes of Bird Mortality,” last modified November 18th, 2010,

Michael R. Reddy, Andrew Spielman, Timothy J. Lepore, David Henley, Anthony E. Kiszewski, and Dr. Paul Reiter. Vector-Borne and Zoonotic Diseases. Summer 2006, 6(2): 117-127. doi:10.1089/vbz.2006.6.117.

Marcombe S, Darriet F, Tolosa M, Agnew P, Duchon S, et al. (2011) Pyrethroid Resistance Reduces the Efficacy of Space Sprays for Dengue Control on the Island of Martinique (Caribbean). PLoS Negl Trop Dis 5(6): e1202. doi:10.1371/journal.pntd.0001202

"Material Safety Data Sheet,"  July 2010,

Pyrethroids: a new threat to marine mammals?