Mosquito Repellents & Bug Sprays
Bug repellents are pesticides. They were previously considered "safe" as concentrations of the pesticide were kept low in bug repellent products. The research below, however, provides evidence that bug repellents can in fact cause serious harm to children and even adults.
Information below is not the personal view of the author but are results of scientific studies conducted at a number research facilities including DUKE University in Durham, NC. These studies were published in peer-reviewed medical journals and acquired from searches through the bound Index Medicus at University of Florida Shands Medical Library and through online seaches through PubMed. Scroll below to view all studies - Links are provided to the original journal article as well.
JOURNAL PESTICIDE TOXICOLOGY SUMMARIES
SOURCE: International Journal of Developmental Neuroscience
Scientists in Lucknow, India have found that the blood-brain barrier is damaged by ingredients typically used in mosquito repellents. A quick science lesson - The blood brain barrier is basically a "wall" that protects the brain from damage that would otherwise occur from the many toxic compounds in our blood. Without a properly working blood brain barrier, the brain malfunctions - resulting in a variety of neurological conditions.
Scientists tested for blood brain barrier damage using a common over-the-counter mosquito repellent containing a 3.6% solution of the pyrethroid pesticide - allethrin. Their previous work had shown that bug sprays caused significant blood brain barrier damage to newborn rat pups (Link). The current study was designed to find out what types of blood brain barrier damage would occur if exposure occurred at different times during development.
Since humans could not be directly tested using this procedure - scientists exposed "rat pups" to the mosquito/bug spray early in pregnancy and also just before and after birth. They used what is called a micromolecular tracer to determine if it "leaked" into the brain after pesticide exposure. Results showed exposure during any of the three time periods resulted in significant break-down of the animals' blood brain barrier. Also of concern, it was found that damage persisted when tested one week after exposure. The scientists concluded by stating,
The results suggest that Mosquito Repellent inhalation during early prenatal - postnatal - perinatal life may have adverse effects on infants leading to central nervous system (CNS) abnormalities, if a mechanism operates in humans similar to that in rat pups.
Chem-Tox Comment: This study is of particular concern for the following reasons:
Developmental Toxicology Division
SOURCE: Environmental News Service, May 10, 2002
DURHAM, North Carolina, May 10, 2002 (ENS) - A common ingredient in mosquito and tick repellents may be linked to some neurological problems, a new study suggests.
A Duke University Medical Center pharmacologist is recommending caution when using the insecticide DEET, after his animal studies last year found the chemical causes diffuse brain cell death and behavioral changes in rats after frequent and prolonged use
Mohamed Abou-Donia, PhD has called for further government testing of the chemical's safety in short term and occasional use, particularly in view of Health Canada's recent decision to ban products with more than 30 percent of the chemical.
Every year, about one-third of the U.S. population uses insect repellents containing DEET, available in more than 230 products with concentrations up to 100 percent. While the chemical's risks to humans are still being intensely debated, Abou-Donia says his 30 years of research on pesticides' brain effects indicate the need for caution among the general public.
His numerous studies in rats, two of them published last year, demonstrate that frequent and prolonged applications of DEET cause neurons to die in regions of the brain that control muscle movement, learning, memory and concentration. Rats treated with an average human dose of DEET - 40 milligrams per kilogram body weight - performed far worse than control rats when challenged with physical tasks requiring muscle control, strength and coordination.
Such effects are consistent with physical symptoms in humans reported in the medical literature, such as those experienced by some Gulf War veterans, said Abou-Donia.
"If used sparingly, infrequently and by itself, DEET may not have negative effects - the literature here isn't clear," Abou-Donia said. "But frequent and heavy use of DEET, especially in combination with other chemicals or medications, could cause brain deficits in vulnerable populations."
Children are at particular risk for subtle brain changes caused by chemicals in the environment, because their skin more readily absorbs them, and chemicals may affect their developing nervous systems, said Abou-Donia.
Preparations like insecticide based lice killing shampoos and insect repellents are assumed to be safe because severe consequences are rare in the medical literature. Yet subtle symptoms, such as muscle weakness, fatigue or memory lapses, might be attributed to other causes in error, Abou-Donia said.
"The take home message is to be safe and cautious when using insecticides," said Abou-Donia. "Never use insect repellents on infants, and be wary of using them on children in general. Never combine insecticides with each other or use them with other medications. Even so simple a drug as an antihistamine could interact with DEET to cause toxic side effects. Don't spray your yard for bugs and then take medications. Until we have more data on potential interactions in humans, safe is better than sorry."
DEET and other Skin Applied Pesticides Reduce Brain Cell Numbers
SOURCE: Journal of Toxicology and Environmental Health, Volume 67(4):331-356, Feb 2004
Depending on the country, different pesticides are used in bug and mosquito repellents. To determine how different pesticides can react to the nervous system, researchers studied 3 pesticides alone and in combinations on adult male rats.
Before being exposed to pesticides, animals were first tested for their ability to complete neurological tasks including beam-walking - beam walk time - inclined plane and grip response assessments. They were then exposed to normal "human doses" of different pesticide combinations and observed for 30 days. Pesticides used included malathion (at 44.4 mg/kg) - DEET (40 mg/kg) - and PERMETHRIN (at 0.13 mg/kg). 24 hours after the last application they were tested again on the neurological tasks.
RESULTS: Results showed that each chemical alone or in combination resulted in impairment of all behavioral measures while combinations of pesticides resulted in greater impairment. For example, the combination of DEET and permethrin, malathion and permethrin, or the three chemicals together resulted in greater impairments in inclined performance than permethrin alone.
Damage to the brain was also seen under microscope inspection. Scientists counted the number of brain cells in different areas of the brain inluding the dentate gyrus, hippocampus, midbrain, brainstem, and cerebellum. Results shown significant reductions in the density of surviving neurons with various treatments.
In conlusion the scientists stated:
These results suggest that exposure to real-life doses of malathion, DEET, and permethrin, alone or in combination, produce no overt signs of neurotoxicity but induce significant neurobehavioral deficits and neuronal degeneration in brain.
Department of Pharmacology and Cancer Biology,
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