malathion molecule - health index
Malathion's Chemical Name is
Dimethoxy Phosphino Thioyl Thio Butanedioic Acid Diethyl Ester
Malathion Molecule
10 H19 O6 P S2

by Wayne Sinclair, M.D.
Allergy, Asthma & Immunology (Immunology Board Certified)
Richard W. Pressinger, M.Ed., Tampa, Florida
email: [email protected]

The medical research below was located from the University of Florida and University of South Florida medical libraries.  As can be seen from the research summarized below, contrary to what the public is often told by the Agriculture Industry and some governmental agencies, scientists are stating that malathion (even at low levels) is in fact, a harmful chemical.

Malathion Malathion Health IndexIndex

Click topic or scroll through below

Wildlife Photos - Photos of animals killed, organs damaged & mutations from malathion
Human Deaths from Malathion - 5 die and 2,800 poisoned after spraying in Pakistan

Intestinal Disorders in Children - significant health problems in children after aerial spraying

Intestinal Disorders in Test Animals - more evidence supporting intestinal defects in children from malathion
Leukemia - child leukemias develop after homes sprayed
Kidney Damage- physician finds kidney damage after patient sprays home
Human Birth Defect - suspected from exposure to malathion lice shampoo
Brain Damage - for unknown reasons malathion causes far more damage in older brains
Chromosome Defects - found in human blood cells
Gene Loss - malathion is able to literally "knock-off" genes from our DNA molecule
Review of Malathion Genetic Studies - technically oriented - recommended for health professionals
Health Disorders found in Second Generation Offspring - harmful effects appearing in future generations
Lung Damage - unusual effect from malathion ingredient - not found in other pesticides
Birth Defects - occurs in hens after malathion feeding
Impurities in Malathion - highly toxic compounds increase during storage due to time and heat
Immune System Weakening - thereby increasing risk of bacteria or viral infections (2 studies)
Sunlight Makes Toxic - malathion reacts with ultraviolet light to become more toxic
Impurities Weaken Detoxification - impurities found to weaken ability of liver to detoxify
Breakdown of Malathion - time periods for malathion breakdown in soil - forming of malaoxon
Fish Heart Defects - heart defects appear in exposed fish
Fish Gill Damage - low levels of malathion cause deterioration of Blue Fish gills
Turtle Birth Defects - turtles unusually sensitive to birth defects
Frog/Tadpole Mutations - evidence of genetic damage
Shrimp Effects - malathion at low levels affects a shrimp's ability to locate food
Lizard Organ Damage - small lizards suffer internal organ damage
Unknown Risks of Malathion - Surprising information about what we do not know
Alternatives to Malathion for Medfly Control - The best alternative to malathion to date (for Medfly control only) is called "SUREDYE."  This highly researched product is a food grade red dye which kills the medfly after ingestion and reacting with sunlight.   The advantages are it does its job without poisoning beneficial insects, wildlife, the environment or people! 

Health Effects Research Summaries

  • Malathion Not as Safe as Believed - 5 Die - 2,800 Poisoned 
    SOURCE: Archives in Toxicology, 42:95-106, 1979

The following information is from the report from the Bureau of Tropical Diseases, Center for Disease Control, Atlanta, Georgia entitled "The Toxicological Properties of Impurities in Malathion." Below is a direct quote from the introductory abstract to the article:

"During a malaria eradication program in Pakistan in 1976, out of 7,500 spray men, 2,800 became poisoned and 5 died. The major determinant of the poisoning has been identified as isomalathion present as an impurity in the malathion. It seems almost certain that the isomalathion was produced during storage of the formulated malathion. 

The quantitative correlation found between isomalathion content and toxicity of many field samples of malathion has been confirmed by an examination of mixtures of pure compounds. Addition of known amounts of isomalathion to technical malathion indicates that other active substances are present. These impurities have been identified (trimethyl phosphorothioates) and have been shown to behave like isomalathion in potentiating the toxicity of malathion. Some preliminary work on their toxicological properties is reported."

Drs. W.N. Aldridge, J.W. Miles, D.L. Mount and R.D. Verschoyle
Toxicology Unit, Medical Research Council Laboratories
Pesticides Branch, Vector Biology and Control Division
Center for Disease Control, Atlanta GA


  • Intestinal Disorders in Children Born After California Spraying
    SOURCE: Epidemiology, 3(1):32-39, January, 1992

This is the first study to show evidence of harm to human health after aerial sprayings of malathion over human populations. Investigators surveyed 933 pregnancies identified through hospitals in the San Francisco Bay Area, in relation to exposure to the pesticide malathion, applied aerially to control the Mediterranean fruit fly. The good news is that after adjustment for confounding factors, there was no association found between malathion exposure and spontaneous abortion, intrauterine growth retardation, stillbirth, or most categories of congenital abnormalities.

However, it was found that children who had been exposed to malathion during the second trimester of pregnancy were showing over two and one-half times more gastrointestinal disorders (affecting the stomach and small intestines) in comparison to children not exposed to malathion during pregnancy.

Chem-Tox Comments: When the Florida Dept of Agriculture says there is no research showing harm to public health after malathion spraying - this is a complete and total lie as here is the research in black and white. This one study certainly raises enough of a red flag to immediately suspend all aerial applications of malathion and supports the animal research showing genetic defects and abnormal growth of cells after exposure to malathion. Unfortunately, this study did not investigate for increases in subtle neurological disorders such as language delays, attention deficits, learning disabilities, hyperactivity or conduct disorders, which the research has shown occurs with other chemicals at exposure levels far under that which causes physical health effects. To look at our website which summarizes the research showing modern chemicals at very low doses can cause subtle child behavior and learning disorders, please visit

Department of Preventive Medicine
University of Southern California, Los Angeles


  • Intestinal Problems in Test Animals Exposed to Malathion
    SOURCE: Bulletin of Environmental Contamination Toxicology, 33:289-294, 1984

    In support of the above findings of intestinal disorders observed in children born several months following the aerial spraying of malathion in California, this study also found malfunctions of the gastrointestinal system in test animals exposed to sub-lethal levels of malathion. Previous work by the same researchers at the Postgraduate Institute of Medical Education and Research, India, had found a single dose of malathion "severely impairs the digestive absorptive functions of intestine" (Chowdhury, 1980). In this present study, the investigators looked at how subchronic malathion exposure would affect digestion in rat intestine. After 45 days of exposure, the animals were killed and tests conducted on the intestines. Results showed a "significant decrease in sodium and potassium ATPase activity which suggests the disruption of ion transport processes in intestine after pesticide exposure." There were also significant increases in glucose and other enzymes. In conclusion the researchers stated,

    "It may be surmised that subchronic malathion treatment may produce aerations in microvillus membrane composition leading to observed changes in intestinal functions.... The results presented in this communication indicate that exposure to this pesticide may produce alterations in intestinal functions; however, the mechanism of pesticide interaction with intestinal epithelium remains to be elucidated."

Drs. R.K. Wali, R. Singh, P.K. Dudeja, A.K. Sarkar and A. Mahmood
Department of Biochemistry
Postgraduate Institute of Medical Education & Research, India
Gastroenterology Division
Michael Reese Hospital and Medical Center, Chicago, Illinois


  • Child Leukemia & Aplastic Anemia after Malathion Exposure
    SOURCE: The Lancet, pg.300, August 8, 1981

    Seven children with bone marrow disorders have been observed over the past 8 years by physicians at Travis Air Force Base Medical Center in California. The physicians believe the blood disorders, in all cases, were caused by organophosphate pesticides.. All blood disorders occurred shortly after exposure to the pesticides DDVP/propoxur and malathion. The duration of inhaling insecticides ranged from 2 minutes in a patient enveloped in a thick insecticide fog in a small shed to 2 days in other patients whose homes were fumigated with th chemical. Six patients had aplastic anemia and one had acute lymphoblastic leukemia. The physicians also cited research showing leukemia in farmers has significantly increased during the period of 1964 to 1976 (Mayo Clinic Proc, 53:714-18, 1978). Apple growers exposed to organophosphates had a higher incidence of leukopenia (very low white blood count) than a control population (Canadian Medical Association Journal, 92:597-602, 1965).

Drs. Jerry D. Reeves, David A. Driggers, Vincent A Kiley
Department of Pediatrics, David Grant Medical Center
Travis Air Force Base, California


  • Kidney Failure After Malathion Sprayed in Home
    SOURCE: Journal of the American Medical Association (JAMA), Vol.250, No.18, Nov. 11, 1983

Whereas kidney damage has been observed in wildlife exposed to low levels of malathion (listed in other research on this page), the following is documentation of suspected kidney damage in a human patient reported by physicians at the St Luke's Hospital Kidney Center in Bethlehem, PA.. The following includes some technical observations for the benefit of our health practitioners.

A 65 year old man was admitted to the hospital because of swelling of his legs. Four weeks before admission, he began spraying intensively with malathion and noted intermittent inhalation and skin exposure. Three weeks before admission, he noted an increase in weight and, subsequently, peripheral edema. He had a five-year history of diabetes mellitus treated with insulin. He intermittently took cimetidine for dyspepsia. He denied use of nonsteroidal anti-inflammatory agents. The doctors summarized by stating:

"This patient experienced acute renal insufficiency with massive proteinuria that rapidly resolved without any specific treatment. The presence of membranous glomerulopathy and a marginally reduced C3 level suggests antigenic exposure with subsequent immune complex deposition in the kidney. He had no known exposure to drugs or toxins associated with the pephrotic syndrome and renal insufficiency. Cimetidine toxicity was successfully ruled out by rechallenge with this agent. There was no evidence of systemic collagen-vascular disease, and the biopsy specimen was not consistent with poststreptococcal glomerulonephritis or diabetes mellitus.

The development of overt renal insufficiency with massive proteinuria within three weeks of exposure to malathion suggests a causal relationship. although our patient has no symptoms attributable to organophosphate poisoning, he may have had a latent exposure without clinical manifestations, although cholinesterase activity may be inhibited. Organophosphate exposure might cause immune complex formation by one of two mechanisms. Antibodies might react with the organophosphate directly or to native antigens that have been unmasked by a direct toxic effect of t he organophosphate. We postulate that malathion provoked an immune complex nephropathy in this patient resulting in renal insufficiency and massive proteinuria, and we stress that this toxic agent must be handled accordingly."

Ronald K. Albright, MD; Barry W. Kram, DO; Robert P. White, MD;
St. Luke's Hospital Kidney Center, Bethlehem, PA


  • Human Birth Defect Suspected from Malathion
    SOURCE: Teratology, 36:7-9 (1987)

    Malathion has been shown to cause birth defects in a variety of wildlife and at levels lower than some other pesticides (see research below). An article printed in the journal TERATOLOGY, (Vol.36) has researchers suspecting malathion may have caused the birth defect known as "Amyoplasia," which is a disorder characterized by almost total absence of skeletal muscle. The birth defect occurred in an infant girl who died soon after birth. The main researcher, Dr. D. Lindhout, was concerned because the mother used a malathion head lice shampoo on several occasions during the 11th and 12th week of pregnancy. Dr. Lindhout also stated that malathion was a suspect in this type of birth defect because -

"When administered to adult animals, malathion and related thiophosphonates stimulate, and subsequently inhibit, the nicotinic sites in skeletal muscle, resulting in muscle weakness and paralysis. Neonates (newborn babies) are far more sensitive to these agents than adults, mainly because of a slower rate of detoxification of the metabolite (the metabolite in this case would be the liver breakdown product of malathion which has been shown to be far more toxic than malathion itself.)"

The doctors felt malathion was also suspect because there was no genetic history of this problem in the mother's or father's family and there was no evidence of drug use by the mother, except for the use of malathion head-lice shampoo during the early pregnancy.
Department of Clinical Genetics, Erasmus University, Rotterdam
Department of Child Neurology, University Hospital, Utrecht



  • Brain Injury from Malathion chemical (Malaoxon) in Older Animals
    SOURCE: Toxicology, 79:157-167, 1993

    The chemical malaoxon, formed from malathion, was found to cause neuronal (brain cell) injury in older adult male rats at doses of only one-fifth that required to cause similar injury in young adult rats. In this experiment, older rats (18 months) were given a single dose of malaoxon at levels of 8.7 mg/kg. Within 10 minutes there were signs of salivation, fasciculations and tremors. Convulsions were observed within 15 minutes in 69% of the rats. The malaoxon also caused an increase of over twice the normal levels of calcium in the frontal cortex of the animals' brains. Researchers believe this fact alone could be directly toxic to brain cells. Significant reductions in the brain neurochemical innositol was also observed in rat's experiencing convulsions. Areas affected included the frontal cortex, hippocampus, thalamus and cerebellum.

    To achieve the same symptoms and same level of brain injury in young adult rats, it required malaoxon exposure at levels of 39.2 mg/kg which is nearly 5 times more than the 8 mg/kg dose causing brain injury in the older rats. In conclusion the scientists stated:

    "In parafin sections, the insult in the old rats characterized by the appearance of shrunken eosinophilic neurons often surrounded by edematous vacuoles. Vulnerable areas included hippocampal pyramidal cells, cerebral cortex and caudoputamen, while e.g. cerebellum and brain stem were spared."

    Chem-Tox Comments:
    Studies such as this should generate serious questions as governmental safety exposure guidelines are based upon using young healthy test animals. We may therefore, be subjecting our elderly population to heightened neurological risk not observed in younger populations.
    National Public Health Institute, Division of Environ. Health, Finland



  • Chromosome Damage Occurs to Human Blood Cells
    SOURCE: Mutation Research, 301:13-17, 1993

    Malathion was found to cause DNA abnormalities at all doses tested in human blood cells. Blood samples were drawn from three healthy non-smoking men, aged 23, 24 and 25. Four different concentrations of malathion (0.02, 0.2, 2 and 20 ug/ml) were added to the blood samples. Slides were then made of the blood samples and examined. Although all doses showed an increase in chromosome abnormalities, a significant increase was noted for doses of 2 ug/ml and 20 ug/ml. In conclusion, the researchers stated:

    "The results show that malathion causes a dose-dependent increase in chromosomal aberrations as well as Sister Chromatid Exchanges in human leukocyte cultures....A dose dependent decrease in mitotic index was observed at all concentrations. Hence, our results suggest that malathion is a mild mutagen and at higher concentrations it might cause genotoxicity in humans."
    Drs. M. Balaji, K. Sasikala
    Division of Human Genetics, Department of Zoology
    Bharathiar University, India



  • Human Genes "Broken-Off" DNA Molecule by Malathion
    SOURCE: Cancer Research, 56, 2393-2399, May 15, 1996
    DNA molecule damaged by malathion
    This 1996 study found that in experiments of human white blood cells (white blood cells are the back-bone of our immune system) that malathion was causing "deletions" in one section of the chromosome. In conclusion the scientists stated,

    "This work provides the first evidence of an association between malathion exposure and specific mutations in human T lymphocytes."

    A quick biology lesson - Genes are not just involved in passing hereditary traits. You have genes active in you at this moment that control what is happening inside every cell in your body every second of the day. There are 200 genes believed to control liver function and 200 genes believed to control immune system function. Your lymphocytes are a type of immune system cell which are extremely important in removing viruses and cancer cells from the body. The human aging process is simply a result of us losing about one-half to 1% of our genes yearly (dogs lose over 4% which explains why they age more rapidly). When we lose too many genes in the cells controlling one part of our health, we become sick - since the cells can't operate at high enough efficiency to do their job. It's a matter of balance - once our cells become so inefficient because of gene loss - then we too can die - the cycle of life. The lesson to be learned from this is we do not want to expose ourselves to chemicals (such as malathion) that can accelerate gene loss in important cells which are protecting us from bacteria, viruses, etc.
    Genetics Laboratory, University of Vermont, Burlington, Vermont



  • Health Problems Appear from Malathion in Second Generation
    SOURCE: Nature, November 4, 1961

    Pregnant test animals exposed to malathion in this study did not show any physical health effects. When their offspring were born there were also no obvious health effects observed. However, when these offspring matured and had their own babies - the researchers found this newest litter had significantly lower body weight, grew slower and had approximately twice the number of infections..

    ChemTox Comments: This research provides strong evidence for the potential for health problems to appear long after the malathion spraying has stopped..
    Department of Pharmacology, University of Toronto



  • Lung Damage Occurs from Single Oral Dose of Malathion
    SOURCE: Toxicology, 26:73-79, 1983

    An unusual effect has been observed from exposure to malathion that has not been observed with other pesticides. A single oral dose of the chemical trimethyl-phosphorothioate (a toxic contaminant present in all malathion), at levels of 20 milligrams per kilogram body weight, was found to cause a reduction in lung cells in the bronchiolar epithelium of rat lungs. While the number of lung cells in a given area of lung tissue in normal rats was over 50, there were only approximately 20 cells found in the same area of lung tissue for rats exposed to the one dose of the malathion impurity. No lung damage was seen when purified malathion was administered. In conclusion, the researchers stated:

    "Trimethyl-phosphorothioate and other impurities of malathion are formed as side products during the manufacturing process (of malathion). Most organophosphorus insecticides are high boiling liquids which cannot be readily purified by inexpensive, conventional methods. Therefore, it is not possible to eliminate impurities completely without prohibitive increase in costs. In short, organophosphate insecticides such as malathion will continue to contain impurities such as trimethyl-phosphorothioate. Further, impurities may be formed during storage at high temperature or by photochemical reaction. Because of potential human hazards arising from exposure to these compounds, their toxicology and mode of action should be completely understood."
    Division of Toxicology & Physiology, University of California, Riverside



  • Feeding of Malathion to Hens Causes Birth Defects
    SOURCE: Agricultural Research Laboratory, Utah State University

    Three hundred twelve white hens and 65 adult white males were divided into groups and fed a diet of a laying mash to which malathion and the pesticide carbaryl were added singly and in combination at levels of 0, 75, 150, 300 and 600 ppm for 3 weeks. Quoting the scientists regarding the observed effects,

    "Eggs were collected daily and incubated to determine hatchability and teratogenic effects (birth defects). As the levels of pesticide in the diet increased, the hatchability decreased significantly. The percentage of deformities increased significantly as the concentration of pesticide in the diet increased. Marked deformities were observed in the chicks that developed. Other findings were the liver and kidney stored more malathion than other tissues."



  • Malathion Becomes More Toxic When Stored for 3 months
    or When Temperature Increases

    SOURCE: Journal of Agricultural Food Chemistry, 25(4):946-953, 1977

    The technical grade malathion (the type we are exposed to) contains approximately 11 impurities. It is these impurities which scientists state are the main poisoning ingredients in malathion. One impurity has been shown to be approximately 500 times more toxic than purified malathion (based on the amount needed to kill test animals - LD-50 is 20 mg/kg compared to 10,000 mg/kg for purified malathion).  It is called - O,S,S-trimethyl phosphorodithioate (OSS-TMP for short). Researchers state this, and other malathion impurities, actually increase in amounts during simple storage (especially 3-6 months after manufacture), making malathion far more toxic than when it was first manufactured. OSS-TMP and other impurities have also been shown to increase even more rapidly when exposed to temperatures around 100 degrees. How high do the temperatures become for the drums sitting in direct sunlight or at the Tampa Airport in the non-air conditioned rooms?
    Effect of Impurities on the Mammalian Toxicity of Technical Malathion and Acephate.



  • Immune System Weakens after Malathion Exposure
    SOURCE: The Journal of Immunology, 140(2):564-570

    immune cells attack cancerTechnical grade malathion contains chemical impurities which have been found to weaken immune system function, including a weakening of a type of white blood cell called "cytotoxic lymphocytes" (which attack cancer cells and virus infected cells). The picture at right shows six of these white cytotoxic lymphocytes (let's call them CTL's for short) successfully attacking a cancer cell (National Geographic). These lymphocytes can also attack viruses in the body. Malathion has now been shown to significantly weaken the CTL's ability to perform their job effectively.

    Chem-Tox Comments: This research addresses the paradox regarding the New York City malathion spraying.
    As encephalitis has been shown to only affect people with a weakened immune system who are unable to efficiently combat the disease (i.e. elderly and immune compromised individuals) it must be considered that malathion has the potential in itself to increase encephalitis cases as the spraying of the pesticide can weaken a person's immune system, thereby, making them more vulnerable to the disease.

    University of Virginia
    Inhibition of Cytotoxic T Lymphocyte and Natural Killer Cell Mediated Lysis by OSS-Trimethyl Phosphorodithioate is at an Early Postrecognition Step.



  • Report Links Pesticides with Immune System Problems
    SOURCE: SCIENCE NEWS, March 9, 1996

    According to a report by the Washington, D.C. based group, World Resources Institute (WRI), many pesticides appear to be increasing the incidence of infections, pneumonia, ear infections, and tuberculosis. The three pesticides listed as causing this problem were DDT, malathion, and the pesticide aldicarb. A summary of the report, appearing in the March 9, 1996 issue of Science News, outlined many of the studies linking pesticides with weakening of the immune system. One of the groups commissioned researchers, Dr. Lyudmila Kovtyukh, of the Academy of Sciences in Kishinev, Moldova (a republic between Romania and Ukraine), found that children living in areas where pesticides had been most heavily applied experienced elevated rates of acute respiratory diseases (including pneumonia), as well as many other signs of immune system weakness. If you would like to read the entire March 9, 1996, SCIENCE NEWS article, it has been placed on the internet by SCIENCE NEWS and can be seen by clicking
    Science News Immune System Toxicology.



    Malathion undergoes a chemical reaction in sunlight called "photolysis" which results in increasing the formation of the highly toxic trimethyl impurities. -
    Journal of Agricultural Food & Chemistry, 27(6):1423



    SOURCE: Toxicology and Applied Pharmacology, 49, 107-112 (1979)

    Once malathion enters the body, it needs to be removed so harm is minimized. This is the job performed in part by enzymes in the liver of all organisms. However, this research showed that the malathion impurities - to quote the scientists - "diminish the activities of the enzymes involved in the malathion detoxification." In other words, the impurities damage the body's natural way of detoxifying the poison with the end result being the chemical stays in the body for longer periods of time when exposure is to the technical grade malathion and especially if subjected to heat and long duration storage.
    Division of Toxicology and Physiology, University of California, Riverside



  • Malathion Breaks Down into even More Toxic - Malaoxon
    SOURCE: Bulletin of Environmental Contamination Toxicology, 57:705-712, 1996

    In trying to calm the fears of Tampa residents, representatives for the Florida Department of Agriculture have made public statements that after application, malathion "breaks-down" in a matter of hours. What they don't tell you is that malathion can actually break-down into compounds which are more poisonous than the malathion itself. This is, in fact, the conclusion of research from a graduate project by researcher N. E. Barlas at the Department of Biology, Hacetepe University, Turkey. Barlas went on to say, "The disappearance of pesticide residues at a given location does not mean the end of the problem. Pesticides can be translocated, bioconcentrated or converted into more dangerous chemicals." The breakdown fate of malathion was studied by adding malathion to soil samples containing 6 species of soil bacteria known to breakdown the pesticide. After 10 days the samples were analyzed. Malathion content had reduced from 100 down to 25 micrograms, so therefore, the Florida Department of Agriculture spokes people are correct when they say it "breaks down" relatively quickly (although in this case not in a matter of hours). However, even more important, Barlas found that new chemicals were formed in this breakdown process including 14 micrograms of monocarboxylic acid and about 8 micrograms of the highly toxic malaoxon. Barlas then exposed mice to the technical grade malathion and another group to the breakdown products just mentioned. Results showed even the mice exposed to the break-down products of malathion showed significant decreases in spleen weights and significant changes in liver blood tests which were suggestive of liver damage. Barlas summarized by stating, "It may be concluded that commercial malathion and it's degradation products together have detrimental effects on mice over a period of 15 weeks of treatment."
    Department of Biology, Faculty of Science, Hacettepe University, Turkey



  • Heart Defects in Fish from Low Levels of Malathion
    SOURCE: Teratology, 19:51-62, 1979

    Levels of malathion in water as low as 5 parts per million were shown to cause heart defects in some types of fish. The fish were studied at Rutgers University in New Jersey. Researchers stated that malathion, if exposed to newly fertilized eggs, caused circulatory defects including - irregular heartbeat, blood clots, oscillating blood in the heart, pericardial edema and physical defects in the heart formation itself.

    The researchers were concerned not only about the malathion but by the toxic metabolic breakdown products a fish makes once malathion enters the fishes circulation (this happens in humans as well).. To quote the main researcher, Dr. Solomon,

    "Another possible problem arising from the use of insecticides is the effect of their different metabolites. A primary metabolite of carbaryl is 1-napthol, while parathion and malathion become paroxon and malaoxon. The latter two metabolites have been shown to decrease cell numbers, DNA synthesis and protein synthesis in cell cultures of chick pectoral muscle (Wilson '73). Thus, the metabolite may be more detrimental than the parent compound."

    Another large concern of Dr. Solomon was the finding that combining other pesticides with malathion greatly increased the fish heart defect rate. For example, at 10 ppm of malathion there was a 38% heart defect rate in fish. The pesticide carbaryl caused a 12% heart defect rate at 1.1 ppm. However, when these two pesticides were combined at these same levels - there was a 50% heart defect rate in the fish.

    Chem-Tox Comments: Between the malathion air assault and additional citrus grove and residential lawn pesticide runoff - this study provides an excellent biological explanation, for at least part of the reason, why we are observing decreases in some fish populations (fisherman take note).
    Rutgers University, Newark, New Jersey



  •  Gill Damage from Malathion Occurs to Popular Sport Fish
    SOURCE: Bulletin of Environmental Contamination Toxicology 43:123-130, 1989

    This study shows one of the most graphic and startling consequences of low level malathion exposure occurring to Florida Game Fish. Scientists placed bluefish in test tanks that had received small doses of malathion equal to the amounts that have been found to occur in the environment after routine spraying. After 24 hours "mild degenerative changes" were seen in the gills of the fish. After 48 hours, researchers stated "damage was more pronounced" and after 96 hours there was severe damage resulting in a condition known as "bulbing." We feel this study is of such importance that we are making the photographs of the malathion damaged gills available by clicking the link damaged fish gill photographs.
    Department of Biological Sciences, Kent State University, Kent, Ohio



  • Turtles Highly Vulnerable to Birth Defects from Malathion SOURCE:Anatomical Record, 175:390, 1973

    For some reason, turtles develop birth defects from malathion easier than many other forms of wildlife. Of concern to the turtle population in our area, malathion was shown to cause 5 times more birth defects, such as skeletal malformations, than the pesticide captan. Therefore, specifically regarding birth defects in turtles - malathion is far more toxic than some other pesticides.  Many turtles throughout rivers in eastern and western Florida are showing tumors over their surface.  Scientists believe these are in fact caused by environmental pollutants (such as pesticides) which are running off via storm water run-off into our river systems.  If you would like to view a photograph of a Florida turtle covered in tumors please click the link cancer-turtle-photograph.
    Department of Anatomy, State University of New York



  • Frogs in Tadpole Stage Develop Mutations from Malathion
    SOURCE: Bulletin of Environmental Contamination Toxicology, 31, 170-176, 1983

    Frogs play a very important role in the food chain, consuming vast amounts of insects. However, like turtles, frogs have been shown to be very susceptible to developing mutations from the pesticide malathion. Levels as low as 1 to 5 parts per million were causing malformed tails and heads and unusual swimming patterns in tadpoles. To view photographs of the mutations seen in frogs please click frog mutation photographs.
    Department of Zoology, University of Poona, India



  • Shrimp Lose Ability to Locate Food - Serious Risk to Food Chain
    SOURCE: Bulletin of Environmental Contamination Toxicology, 53:127-133, 1994

    If you're a shrimp - finding food is not a hit or miss coincidence. Mother nature gives you a sort of radar called "chemo-reception" that allows you to pinpoint where food is located in the murky waters of Tampa Bay. With your chemo-reception radar in working order you move in and grab a bite. However, research from the Department of Biology at the Chinese University of Hong Kong finds a surprising effect from the pesticide malathion. At levels far below that of causing death, the chemical shows it can drastically impair this radar food finding system. For example, in tests of shrimp exposed and not exposed to the low levels of malathion, it was found that the shrimp in the clean malathion-free water were 50% more successful in finding food. Considering that shrimp are one of the more important food sources for many aquatic wildlife - the impact upon the entire food chain is immense. This study certainly gives ammunition for local fisherman to become involved..
    Department of Biology, Chinese University of Hong Kong



  • Lizards Develop Liver & Kidney Damage at Very Low Levels
    SOURCE: Bulletin of Environmental Contamination Toxicology, 55:730-737, 1995

    Perhaps the most sensitive of all forms of wildlife to exposure to malathion are the "dwarf lizards." These reptiles perform a service consuming significant amounts of other small insects. Lizards were exposed to malathion at levels of only 1 milligram of malathion per kilogram body weight (mg/kg) - 2 mg/kg - and 3 mg/kg. Each dosage caused significant damage to the animal's livers, kidneys, and small intestines. Note, these exposure levels are extremely small as the amount needed to cause death in most mammals is well above 500 mg/kg. The researchers concluded by stating "Uncontrolled use of malathion or related compounds will certainly endanger not only the lives of lizards but also affect food chain and ecological balance of nature negatively."
    Department of Biology, Faculty of Science, Osmangazi University, Turkey



  • "Half-Truths" by Officials Hide Important Malthion Facts
    There are two types of malathion that can be used in medical health effects research. One is the "purified form" (which is approximately 99.9% malathion) and the other is called "technical grade"(which is approximately 96.5% malathion) and is the type being sprayed over Tampa and Lakeland. The technical grade is approximately 10 times more potent in causing death to laboratory animals. The type of malathion being sprayed over Tampa is not always the type being referred to in health studies by malathion proponents. Compounding the problem, the malathion we are being sprayed with has been "baking" in the hot summer which research finds converts it into an even more toxic compound.
    Division of Toxicology, University of California



  • Unknown Risks of Malathion
    Perhaps what is more disturbing about malathion (and other chemicals as well) is not what is actually known about the health effects from the chemical, but rather, what is not known. It is important for the public to understand that although chemical companies spend millions of dollars and several years testing their chemicals, the testing protocols they use are dangerously incomplete.

    Let's correct several common misunderstandings. First, the EPA does not test malathion. EPA only sets up the guidelines for the testing. The chemical companies then conduct their own tests and submit the results to EPA for review (foxes guarding the hen house?). In fact, there have been occurrences in the past, such as with Industrial Bio-Test Labs, in which falsified and fraudulent data was submitted to EPA. (Remember, there is extreme financial gain to be made from registration of a chemical).

    The primary tests EPA required for malathion include:

    * LD-50 (the amount needed to kill 50% of the test animals)
    * Tests for major organ damage
    * Tests for delayed neurotoxicity in a hen after a single dose
    * Skin hypersensitivity tests
    * Physical birth defects
    * Cancer Risk

    These tests, however, are seriously inadequate. For example, EPA has been stating for years that they would require more detailed tests for chemical effects upon the immune and nervous system. However, to date, these requirements have not been implemented and probably will not be considering the large amounts of "donations" currently being given by pesticide manufacturers to members of Congress.

    Below are examples of effects that could very well be occurring from malathion and other pesticides - but which there is just no information. In other words, this provides an excellent example of chemical Russian Roulette with the American people.   Perhaps the biggest unknown risk from malathion is its potential to increase risk of contracting bacteria or viral infections such as encephalits. 

    This paradoxical situation arises since exposure to malathion can weaken a person's immune system.  Therefore, people whose immune integrity was marginally above that needed to protect from encephalitis (remember, encephalitis only appears in the elderly, very young and sick who already have a weak immune system) could now be placed into a weakened enough state that the encepahalitis virus could grow more quickly in the body.

    Other effects of malathion for which there is no research, but seriously needed include its ability to cause -

    ? Learning Disabilities in math, reading, etc.
    ? Attention Deficit Disorder (A.D.D.)
    ? Hyperactivity
    ? Mild mental retardation?
    ? Lower IQ
    ? Language or speech delays
    (found highly vulnerable to low level chemical exposure)
    ? Short term memory damage
    ? Tests of all personality facets including -
    ? Aggression
    ? Irritability
    ? Depression
    ? Increased emotionality
    ? Decreased head circumference in offspring
    (suggesting reduced brain cell growth)
    ? Damage to the blood brain barrier
    (which functions to block toxic chemicals from entering the brain and has been found weaker in psychiatric and Alzheimer's patients)
    ? Increase infertility or miscarriage
    ? Alter hormones involved in defining sexuality
    (as occurs with pesticide chlordane)
    ? Lower sperm count
    (linked to increases in genetic flaws in sperm DNA)
    ? Slower sperm movement
    ? Autoimmunity -
    renegade immune cells which attack the body by mistake causing rheumatoid arthritis and over 40 other diseases.
    ? Lower the number of immune system cells -
    thereby increasing risk of infection
    ? Slow the movement of immune system cells -
    thereby increasing risk of infection
    ? Weaken ability of immune system cells to locate bacteria, viruses, etc. -
    thereby increasing risk of infection
    ? Weaken the ability of immune system cells to produce interferon, interleukins and other natural compounds essential to stimulate the body's infection fighting capability -
    thereby increasing risk of infection
    ? Weaken the ability of immune system cells
    (such as natural killer cells) to locate cancer cells and efficiently remove them
    ? Increase risk of asthma -
    as has been found to occur with other pesticides
    ? Increase risk of allergies
    ? Reduce the efficiency of our DNA repair process -
    thereby accelerating aging
    ? Complete all of these tests on second generation offspring to look for true long term subtle genetic effects

    Each of the above "unknown effects" are listed here for a reason The reason being that all of the above effects have been found to occur after exposure to other pesticides and chemicals when tested by various University Research Agencies. Of great concern, the amount of chemical exposure required to cause the above effects is many times lower than the amount required to cause cancer, birth defects, organ damage or other major effects. (This may be one of several reasons the tests are not added to the protocols of chemical testing requirements). 

    If you would like to review our website that addresses the potential for extremely low levels of chemicals to damage the developing unborn child - please visit our website developed from a University of Florida Graduate Research Project on Environmental Causes of Learning and Behavior Disorders.

    Malathion Research Index
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    Other Pesticide
    Health Effects Research