Mosquito Control Pesticides
Harm to Environment & Public Health
Compilation of the Scientific Research

Mosquito control pesticides are typically applied over neighborhoods using trucks and airplanes. Spraying over wide areas using planes and trucks exposes residents to concentrated levels of pesticides when wind blows across treated areas and toward homes. The practice now, however, is showing that the consequences of this are far worse than the mosquitoes.

Research below has linked mosquito control pesticides to diabetes, autism, genetic damage, cancer, the autoimmune disorder Guillain Barre' and microcephaly (small head size). Pesticides used in mosquito control typically include permethrin, malathion and naled (also known as dibrom). The research studies below were acquired from searches through the bound Index Medicus at University of Florida Shands Medical Library and through online seaches through PubMed. The original study can be seen from the "View Journal Online" link below each journal source. Scroll below to view all research summaries.

It has been reported that microcephaly (small head size) and Guillain Barr Syndrome are suspected outcomes of Zika Virus infection. This conclusion is based on observations that people with ZIKA have been found to sometimes have Guillain Barr or have children with microcephaly. Interestingly, research below shows that microcephaly and Guillain Barr also occur more often in the presence of pesticides. It is also interesting to note that the small percentage of people in South America who develop severe ZIKA virus symptoms have also been found to have very low white blood cell counts in Emergency Room visits. Perhaps, not coincidentally, low white blood cell counts (especially lymphoctyes) are also a consequence of pesticide exposure. In fact, low white blood counts will result in faster growth of any viruses (including ZIKA). Therefore, condeming ZIKA for microcephaly and Guillain Barr may very well be a hasty and superficial conclusion. Research must be conducted to investigate the plausibility of living and working in high pesticide areas (such as impoverished agricultural areas of Brazil) and its likelihood of weakening and damaging the immune system and brain. Although this could be an inconvenient truth - it is something that must be investigated by non-biased sources. Both studies on pesticides causing microcephaly and Guillain Barr can be seen below.


Diabetes Dramatically Higher in Mosquito Control Workers -
Warnings to Society?

Source: Journal of Agromedicine, Vol. 19(4):417-26, 2014
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Type 1 diabetes is an autoimmune disorder in which the immune system malfunctions and mistakenly attacks insulin producing cells of the pancreas.

To determine if pesticides could be contributing to diabetes, researchers performed blood tests on 116 mosquito control pesticide workers - the rate of diabetes and pre-diabetes among this group was an astounding 61%. For comparison, rates of diabetes and pre-diabetes was less than 8% when compared to 92 people used as controls not exposed to mosquito control pesticides.

These rates were calculated from exposure to all types of pesticides. When rates were calculated for those exposed to only pyrethroid based pesticides (such as the common truck mosquito pesticide permethrin), diabetes and pre-diabetes rates increased further to more than 18x higher than rates observed in the control group not exposed to pesticides. Diabetes and pre-diabetes were defined as individuals whose blood samples showed an HbA1c level of 5.6% or higher. HbA1c is a form of hemoglobin that attaches to glucose and is an accurate measurement of average blood glucose (sugar) levels over the past several months.

Section for Environment
Occupation and Health
Department of Public Health
Aarhus University, Aarhus, Denmark


Microcephaly (small head size)
after Exposure to Mosquito Control Pesticide Naled (dichlorvos)

SOURCE: Neurochemical Research, 27:231-240, 2008
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Microcephaly is a medical condition in which the brain is considerably smaller than normal. Smaller head size has been linked to lower reading ability and lower academic performance in children. In this study, scientists found that animals receiving only one exposure to the mosquito control chemical dichlorvos resulted in smaller head size in offspring. Dichlorvos forms within hours after naled (dibrom) is sprayed from planes or trucks commonly used mosquito control pesticide applications.

The photograph above shows the brain of a normal guinea pig (left) and the brain of another guinea pig (right) that was exposed to the chemical dichlorvos. Dichlorvos was found to cause a - severe reduction - in brain weight and shape among test animals. The timing of exposure appeared to be the key factor in determining brain damage. Brain damage was observed when guinea pigs were exposed to a non-lethal dose of the pesticide between 42-46 days of gestation at levels of 15 mg/kg. Scientists say this time period correlates with the brain growth spurt period for the animal.

The powerful neurotoxic nature of this pesticide was further emphasized when scientists found the brain abnormalities did not occur when animals were exposed to the other pesticides tested - soman - TOCP and ethyl-trichlorfon.

Scientists concluded by stating they suspect the brain defect occurred due to direct damage to DNA at a time when the animals' repair systems are not developed.

CHEM-TOX COMMENT: The fact that this study shows neurological damage can easily occur in animals after just one exposure (who are often less sensitive than humans to harmful neurological effects) is enough to warrant serious re-evaluation regarding the use of this highly toxic chemical over both animal and human populated areas.

University of Oslo, Institute of Biology
Department of Molecular Cell Biology, Oslo, Norway
Norwegian Defense Research Establishment
Division for Environmental Toxicology, Kjeller, Norway


Autism Higher in Neighborhoods Using Mosquito Control Planes

SOURCE: Science News, April 30, 2016
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Research presented at the 2016 Pediatric Academic Societies Meeting in Baltimore MD, suggests that using airplanes to spray mosquito killing pesticides increases the risk of autism spectrum disorder and developmental delays in children.

Researchers identified a swampy region in central New York where health officials use airplanes to spray pryrethroid pesticides each summer. The pesticides were used to target mosquitoes that carry eastern equine encephalitis virus. They found that children living in ZIP codes where aeirial pesticide spraying has been taking place since 2003 were 25% more likely to have a diagnois of autism or developmental delays (learning problems).

In a comment by the lead investigator, Dr. Steven Hicks,

Other studies have already shown that pesticide exposure might increase a child's risk for autism spectrum disorder or developmental delay," said lead investigator Steven Hicks, MD PhD. "Our findings show that the way pesticides are distributed may change that risk. 

Guillain-Barre Higher after Aerial Pesticides
Source: Archives of Environmental Toxicology, Vol. 59(11): 575-80, Nov 2004
Background on Guillain-Barre syndrome.
Although this study was not done specifically with mosquito control pesticides, it is included here because of it was conducted in a community receiving high levels of airplane applied organophosphate pesticides. Guillain-Barre is a rapid-onset autoimmune disease characterized by muscle weakness. Symptoms can appear over hours or weeks and is caused by the immune system attacking and damaging the peripheral nervous system. It can be life threatening if affecting breathing muscles.

Abstract from Journal:

Although organophosphate (OP) insecticides have been recognized as having neuropathic potential, a relationship with Guillain-Barre syndrome (GBS) has not been previously confirmed. A cluster of 7 cases of GBS was noted over an 11-yr period in an isolated farming region in the Northern Cape Province of South Africa, an area subject to intensive aerial application of OP insecticides. Observed cases were more than 4 times higher than expected based on a Poisson probability distribution. Four cases were clustered in an area where the topography showed a marked hollow, and where spray drift of aerial OP insecticides was anticipated. The rate of GBS in this subcluster was more than 14 times higher than expected. The authors explored the hypothesis that aerial OP insecticide application was related to the raised incidence of GBS in this area and made suggestions for future research.

MCAN COMMENT: Naled is also an organophosphate pesticide

Chromosome Damage from Common Mosquito Pesticide Permethrin

SOURCE: Teratogenesis, Carcinogenesis, and Mutagenesis, 14:31-38, 1994
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Researchers at the National Center of Sanidid Ambiental in Madrid Spain found that the pesticide permethrin (the type typically used in mosquito truck spray programs) was able to induce "structural chromosome aberrations" in human immune system cells as well as in the reproductive cells in laboratory animals. The chromosome damage became apparent after 2 hours of exposure at levels of 150-200 ug/ml (micrograms per milliliter). Chromosome damage was also detected at lower levels.

As stated by the researchers:

"The effect of permethrin seemed to be dose-dependent. Permethrin induced chromosome and chromatid-type aberrations. The highest frequency of chromosome aberrations, mainly chromosome-type, was induced by 100 ug/ml of permethrin in both cultures... Thus, we can say that permethrin is a clear clastogenic (genotoxic) agent in two different cell systems."

J. Muro, A. Martinez, A. Lopez, M. Diaz and R. Fernandez


Cancer Occurs from Mosquito Pesticide Naled

SOURCE: Japanese Journal of Cancer Research, Volume 82:157-164, February, 1991
View Journal Online - View Full Text PDF

The pesticide Naled (Dibrom) is said to "break-down" quickly after application. This is true, however, it breaks-down into an evern more toxic compound known as dichlorvos in the presence of oxygen immediately after application.

Researchers at the National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina studied the effects of the pesticide Dichlorvos on several types of laboratory animals.  Dichlorvos was administered beginning at levels far below that needed to kill 50% of the animals (called LD-50).
Levels administered ranged from 4 to 40 mg/kg (milligrams per kilogram) body weight. The study itself was carried out for 103 weeks.

While there were no changes seen in test animals exposed to the pesticide when compared to animals not exposed to the pesticide (controls) regarding body weights and survival rates, howeverf, there were other serious health effects observed. The researchers did find significantly higher rates of cancer affecting the pancreas - forestomach - as well as mononuclear cell leukemia in male rats.

The so-called "safety" of dichlorvos may have been based on articles appearing in the journal Mutation Research in which scientists were reported to "down-play" the cancer risk. However, as stated by the scientists in this more recent research paper (pg.158):

"Different views on the carcinogenicity data have been published; most indicate that the earlier studies were inadequate (2 references pg.158), flawed (1 reference pg.158) or showed unequivocal carcinogenicity (2 references pg.158). According to the EPA (using all the available data) "dichlorvos has been classified as a carcinogen based on oncogenic effects in mice and rats
(1 reference pg.158)..... Increased incidences of mononuclear cell leukemia was observed in dosed male and female rats. In the male rats the increase in incidence was dose-related and statistically significant. Incidences of multiple fibroademonmas were seen in 9 exposed female rats whereas none were observed in the controls.

In conclusion the researchers stated,

"Dichlorvos caused or was associated with neoplastic responses in rats (pancreas, hematopoietic system, and possibly the mammary gland) and in mice (forestomach)."

Although Naled is banned in the European Union, thousands of gallons of this chemical are still sprayed over populated areas in the U.S. and other countries around the world - the potential for irreversible damage to public health, wildlife and marine life must be considered in light of the above research.

Po C. Chan, James Huff, Joseph K. Haseman, Roger Alison and J. D. Prejean
National Institute of Environmental Health Sciences, Research Triangle Park, NC
Southern Research Institute, Birmingham, AL


Hyperactivity Higher in Children
Exposed to Common Pyrethroid Pesticides

SOURCE:  Environmental Health, Vol. 14:44, May, 2015
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Pyrethroid pesticides are typically used in truck and airplane mosquito control applications, food, and also for home and school pest control (including integrated management pest control - IPM). 687 children were tested for urinary levels of the pyrethroid pestides. Children with detectable urinary levels of the pyrethroid metabolite called "3-BPA" were more than twice as likely to have hyperactive-impulsive symptoms. After that, every 10-fold increase in 3-PBA resulted in an additional 50% increase in hyperactive-impulsive behavior.

This study is of concern as pyrethroid pesticides are now commonly used as a replacement for the previously banned organophosphate pesticides. They are commonly used in school pest control - home pest control and community mosquito control applications from trucks and planes. The pesticide is also found in commercially grown foods (but not in organically grown foods).

Cincinatti Children's Hospital Medical Center, Cincinatti, Ohio
Rutgers Robert Wood Johnson Medical School and
Environmental & Occupational Health Sciences Institute.
Brown University of Public Health, Providence, RI


ZIKA Virus Symptoms Worse in People with Low White Blood Count
Evidence for a Pesticide Connection?
Source: Emerging Infectious Disease, Volume 21(10):1885-, October 2015
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On March 26, 2015, 24 patients with suspected viral illnesses were admitted to the Santa Helena Hospital in Camaçari, Brazil. Blood samples were taken to determine what is called a Complete Blood Count (CBC).
(A complete blood count includes several tests including the total number of white blood cells. White blood cells are the backbone of the immune system). Blood samples were also analyzed for the viruses - Dengue, Chik, West Nile, Mayara or Zika (ZIKV) using a method known at RT-PCR at the Federal University of Bahia.

Results showed all patients were negative for Dengue, Mayaro and West Nile viruses. Samples from 3 patients (12.5%) were positive for Chik virus and 7 patients (29.2%) were positive for ZIKV. There was no simultaneous detection of Chik and ZIKV. Most patients positive for ZIKV were women (85.7%) with no history of international travel.

Complete Blood Count results for these 7 patients with acute ZIKV (Zika Virus) infection showed an average white blood count of 3,750 cells per cubic millimeter of blood. For comparison, the median and average white blood count in the normal population is approximately 7,000. This shows that ZIKV infected patients had immune system counts that were severely depressed with only a little more than half the numbers found in normal individuals.  In other words, ZIKV patients had far less numbers of critical white blood cells needed to remove the virus from their body. Since low white blood counts do not occur in the majority of people bitten by a ZIKV mosquito, we can rule out that the virus is itself responsible for causing low blood counts.

Looking further into the test results, the white blood counts for all seven ZIKV patients ranged from 2,790 to 6,150. For comparison, 95% of the "normal" population has a range of approximately 4,000 to 10,000. As several patients were below 3,700, this immediately puts them into a category of severely low white blood counts and at a high risk for severe consequences from any viral infection. Of great concern, the main white blood cells that remove viruses from the body are called lymphocytes. Normally, lymphocytes are 20-40% of total white blood cells which means this patients could be expected to have from 900 to 2000 total lymphocytes,

STOP SPRAYING COMMENT: This is the first report we have encountered that provides insight into immune system parameters for ZIKV patients. It is important to know that a type of white blood cell called lymphocytes is the primary white blood cell for removing viruses from any person or animal. Lymphocytes normally comprise about 30% of all white blood cells). Research over the past decades has also shown that approximately 10% of lymphocytes are in a category known as "natural killer cells." Natural killer cells are one of the very first lines of defense in preventing a virus from taking hold and multiplying (failure of this process then requires other immune system cells to then come into play). Since any defect in the number or function of lymphoctyes (and natural killer cells) would greatly predispose the individual to an abnormally faster growth of virus cells in the body - it is imperative to further investigate if those with severe ZIKV symptoms have increased contact with circumstances known to weaken the human immune system (ie. pesticides in agriculture - mosquito control - home use - etc.. This information could easily be attained through a background questionarre looking at employment history - proximity to agriculture fields - and even other documented immuno-toxic sources such as dioxin from diesel trucks and burning of plastic based trash. Failure to conduct this next logical phase of research leaves open this critical question.

Federal University of Bahia
Salvador, Bahia, Brazil (G.S. Campos, S.I. Sardi)
Hospital Aliança, Salvador (A.C. Bandeira)
Critical Immune System Cells Damaged
by Mosquito Control Pesticide Naled (Dichlorvos)
Source: Toxicology, Vol. 239(1-2):) 294-30, Sep 24, 2007
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The pesticide dichlorvos (a breakdown product of the mosquito control pesticide Naled) and the common agricultural pesticide lorsban (chlorpyrifos) were both found to kill natural killer cells through a process known as apoptosis in a time and dose-dependent manner. Chlorpyrifox showed a faster response than dichlorvos at higher doses; whereas, dichlorvos showed a slower, but stronger apoptosis-inducing ability than chlorpyrifox at lower doses.

STOP SPRAY COMMENT: As natural killer cells are critical for preventing viruses from causing infection, the potential for accelerated viral growth resulting from pesticide exposure must be considered and investigated in geographic areas suspected of high viral prevalence.

Department of Hygiene and Public Health
Nippon Medical School, 
1-1-5 Sendagi, Tokyo, Japan


Immune System Weakening and Frog Mutations
from Pesticides used in Mosquito Control

SOURCE: Article below appeared in the San Francisco Chronicle
by Carl T. Hall, Chronicle Science Writer
Original journal article appeared in
Proceedings of the National Academy of Sciences: 99(15):9900-9904, July 23, 2002

Raising new questions about the environmental risks of some widely used farm chemicals, scientists are reporting today the first evidence linking agricultural runoff to grotesque hind-limb deformities in frogs. Researchers said frogs appear to be made more vulnerable to a common parasite when exposed to the pesticides atrazine and malathion. The parasite, a burrowing trematode worm, tends to infect the hindquarters of developing tadpoles. Atrazine is part of a family of chemicals that rank among the world's most widely used weed killers. Malathion is commonly applied to control mosquitoes and other insects, and pharmaceutical grades are approved for killing head lice. Both products are controversial but considered safe for commercial use in the United States.

At last count, wild frogs with missing or extra hind limbs have been observed in at least 43 states and five Canadian provinces. Earlier studies clearly implicated the trematode parasite but left open the question of what might be causing the apparent increase in the problem.

The latest study, by ecologist Joseph Kiesecker at Pennsylvania State University and edited by UC Berkeley amphibian specialist David Wake, tries to fit in the key remaining puzzle piece. The study appears in the early edition of this week's Proceedings of the National Academy of Sciences.

Kiesecker said his observations of the common wood frog Rana sylvatica in the wild, followed by controlled studies in his laboratory, produced "compelling" evidence that pesticides can weaken the immune system of exposed amphibians -- even at very low concentrations -- making the frogs more vulnerable to parasites.

The field studies showed "considerably higher rates of limb deformities where there was pesticide exposure," Kiesecker said in an interview, "then the lab experiments helped support the mechanism for what we saw in the field."

He also looked at another pesticide, a synthetic chemical called esfenvalerate, but did not find the same links to growth anomalies as seen with malathion and atrazine.

For the latter two chemicals, significant effects were seen even at concentrations considered safe for drinking water by the Environmental Protection Agency.

Even these very low levels of exposure could produce "dramatic effects on the immune response" of the animals. And that, in turn, led to significantly more growth defects.

Kiesecker stopped short of endorsing any effort to further restrict use of atrazine and malathion. But he said his results underscored the importance of studying toxic chemical effects in a context approaching the complexity found in natural ecosystems.

In this case, he explained, the two farm chemicals "disturbed host-pathogen interactions" with sometimes devastating effects. But all that would be missed in traditional studies examining only the chemicals and the frogs in isolation.

Some other scientists, backed by the farm-chemical industry, challenged Kiesecker's results. Although they said the new study was intriguing, they suggested the details couldn't be trusted until corroborated independently.

Original Journal Article Author Information:
Joseph M. Kiesecker
Department of Biology, Pennsylvania State University
208 Laboratory, University Park, PA