Malathion is a non-systemic, wide spectrum insecticide. It was one of the earliest organophosphate insecticides developed (introduced in 1950) and still is/was one of the most commonly used organophosphates. Malathion is suited for the control of sucking and chewing insects on fruits and vegetables. Malathion is also used to control mosquitoes, flies, household insects, animal parasites (ectoparasites) and head and body lice. It has a wide range of uses including agriculture, stored grain and forests.

Other names of Malathion (O,O-dimethyl-S-[1,2-carbethoxyethyl]phosphorodithionate) include:
carbophos, maldison and mercaptothion.
Trade names for products containing malathion include:
Celthion, Cythion, Dielathion, El 4049, Emmaton, Exathios, Fyfanon and Hilthion, Karbofos en Maltox. From:

General effect

Malathion inhibits acetylcholinesterase (AChE). Acetylcholinesterase breaks acetylcholine down. Acetylcholine is essential in transmitting impulses between nerves. With malathion AChE becomes unable to break down acetylcholine, which consequently accumulates in nerve cells. This abnormal acetylcholine build-up can cause incoordination, rapid twitching, incoordination, paralysis and death (Tucker J.W et al 1987, Gallo, M.A et al 1991).

Studies revealed that inhaled Malathion caused the inhibition of AChE equivalent to an oral dose 15 to 20 times higher (Weeks, M.H. et al. 1977).
Malathion absorbs very well through the skin too.

Symptoms of exposure to malathion insecticides include: headache, nausea and vomiting, diarrhoea, dizziness, burning or watery eyes, difficulty breathing or wheezing, weakness, irritated or itchy skin, exacerbation of asthma, sore or burning throat, pallor, light-headedness, abdominal cramps, and lethargy (Calif. Environmental Protection Agency. 2003).
Other symptoms include: pinpoint pupils and blurred vision, excessive sweating, salivation and lacrimation, wheezing, excessive tracheobronchial secretions, agitation, seizures, bradycardia or tachycardia, muscle twitching and weakness, and urinary and faecal incontinence, blue skin (lips and fingernails), loss of appetite, anxiety, confusion agitation, coma...


The technical grade malathion ( the type we are exposed to) contains approximately 11 impurities. These impurities are the main poisoning ingredients in malathion. One impurity (O,S,S-trimethyl phosphorodithioate) was approximately 500 times more toxic than purified malathion (Umetsu N et al 1977).
Malaoxon is 40 times more toxic as malathion, and is the primary source of malathion’s toxicity. (Brown et al 1993).

Bacteria, UV light, heat, fungi, break malathion down into new highly toxic chemicals like monocarboxylic acid trimethyl phosphate esters and malaoxon, relatively quickly. (Barlas NE. 1996, Bavcon Kralj M et al 2007).
Impurities in commercial formulations are potent inhibitors of carboxylesterase, allowing a dramatic increase in malaoxon formation, the toxic oxidized metabolite (Talcott RE et al 1979, Buratti FM et al 2005).
The disaster in Pakistan is tentatively attributed to the impurities, especially, S-methyl malathion (Umezu K 1978).

Some people could be far more sensitive, due to a different metabolism (Buratti FM et al 2004, 2005).


Finding literature about the damaging effect of malathion is easy. Countermeasures to be taken in case of Prioderm® Noury® overdosing are rather tough (label instructions).
Malathion, the active substance in these two remedies, is banned since 1996 in the U.S. as suspected hormone disrupter and so endangering hormonal development. (

Malation is banned December 6th 2007 as crop protector in the European Union: Malathion was not included in the Appendix I Regulation 91/414/EEG. Up to June 6th 2008 the substance could be deliverd, but after December 6th 2008 the insecticide could not be applied anymore. The College voor de Toelating van Gewasbeschermingsmiddelen en Biociden (CTGB) in the Netherlands was withdrawing the admission for ‘Brabant Malathion 50 procent’ and ‘Luxan Malathion 50 procent Vloeibaar’.


In the experiments is dealt with the pure form (999.9% malathion) and the more toxic TG malathion (technical grade 96.5% malathion).


DNA regulates the business in sex cells liver cells, immune cells, skin cells……

According to the NIOSH (National Institute for Occupational Safety and Health) malathion is mutagenic, it affects the DNA (Mongst others: Flessel P et al 1993, Balaji et al 1993, Pluth JM 1996). More recent studies do conclude the same for mice (Giri, S. et al. 2002, Amer, S.M. et al. 2002) and human (Pluth, J.M. et al. 1998, Blasiak, J. et al. 1999, Blasiak, J. and D. Stankowska 2001).


Melathion is carcinogen (Balaji M. et al 1993, Cancer Research 1996)), it causes breast cancer (rats, probably humans too) (Cabello, G. et al. 2001, 2003) and it doubles the risk of human non-Hodgkin′s lymphoma (McDuffie, H.H. et al. 2001, Cantor, K.P. et al. 1992.)


Malathion accumulates in male reproduction organs (J. of the Med. Ass. of the State of Alabama 1972). It damages mice sperm, lowers the production, sinks the testosterone level, affects the production location (Amer, S.M. et al. 2002, Akbarsha, M.A., et al 2000, Contreras, H.R et al 1999, Bustos-Obregón, E et al 2003) and it affects the enzymes in the testis (partly irreversible) (Balasubramanian, K. et al. 1987).
Malathion hinders sex hormone transport in blood (Meulenberg, E.P. 2002) and so inhibits the rats virility. This virility regenerates in time, but it never reaches the original level. 3 times less compared to original ( Vrbovsky L, et al 1958).

Malathion deforms the embryo (Samimi A et al 2001, 2001) of mice (Asmatullah S et al 1993), chicken (Gill GR et al 1972, Wyttenbach CR et al, 1985), and probably also of humans.

Some health problems malathion causes, only become visible in the second Generation.
Pregnant test animals exposed to malathion did not show any physical health effects. When their offspring were born, there were also no obvious health effects observed. However, when this 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 (Kalow W et al, 1961)

Immune system

Malation can provoke hypersensitivity symptoms but also affect the immune system (Galloway, T. and R. Handy. 2003, Rodgers K 1996, Reeves, Jerry D et al 1991) This depending on the dose and the incubation time (Vrbovsky L,et al 1958, Rodgers KE et al 1990).


Malathion affects the brain function. Already in 1996 malathion was suspected to be (co) responsible for the Chronic fatigue syndrome (BEHAN PO). Misra UK et al (1981) discovered that almost half of the sprayers using no protective devices were plagued by anxiety, sleep disturbance, somatic concern and depression. Electroencephalographic abnormalities were also found.
Rats hippocampus (short term memory), midbrain, brainstem and cerebellum (motor skills) were affected (Abdel-Rahman A et al 2004). Rats aversive memories are affected (Valvassori SS et al (2007). These rats lost the ability to lean from negative experiences and persisted in showing the same behaviour. Carter WG et al (2007) saw that malathion attaches to certain brain and thymic proteins.
Remarkable is the fact that elder rats were 5 times more sensitive (Hirvonen MR, et al 1993).


To the technical grade malathion exposed mice showed significant decreases in spleen weights and significant changes in liver blood tests, which suggested liver damage (Barlas NE 1996). Oral administration of O,O,S-trimethyl phosphorothioate (OOS), caused morphological changes in the bronchiolar epithelium of rat lungs (Imamura T et al 1983). Administration of a single oral dose of 60 mg/kg OOS-Me-induced kidney tubule damage to rats (Keadtisuke S et al 1987) and induced liver damage (Keadtisuke S et al 1990).

Malathion led in rats to a significant decrease in serum concentration of T3 and T4. Administration of malathion also increased the TSH secretion (Akhtar N et al, 1996).

A group of children in Saku City, Japan, involved in chronic intoxication by malathion showed all kinds of reduction of vision, including: narrowing of peripheral visual fields, refraction anomaly with high astigmatism, neurological abnormalities with EEG abnormalities, disturbance of the smooth pursuit motion of the eyes, insufficiency of the pupillary sphincter, optic neuritis and/or retinochoroidal atrophy (Ishikawa S JR et al 1971, Ohto K 1971).

Malathion may cause the birth defect known as ‘Amyoplasia’, which is a disorder characterized by almost total absence of skeletal muscle. Gastrointestinal anomalies were related to second trimester exposure of malation (Lindhout D et al 1987, Duncan C. et al 1992). Malathion enhances anemia (Vrbovsky L,et al 1958).


Children are more exposed to malathion than are adults. The Minnesota Children’s Exposure Study found malathion breakdown products in children about five times as often, as a comparable study of adults; Concentrations were about 4 times higher too (Adgate, J.L. et al. 2001). Children's excretion is less and the absorption is higher.
As malathion runs through the placenta, infants are already exposed to malathion before birth when they are most vulnerable (Ostrea, E.M. et al. 2002).

The Natural Resources Defense Council is pointing out that products intended to kill fleas and ticks can also poison pets and the people who handle them. Particularly toddlers, who's normal behaviour bring them in close contact with their pets

Fish, frogs, toads, bees, birds

Fish, frogs, toads, bees are extremely sensitive to malathion.
The very intensive spraying of malathion in New York State during autumn 1999 did have disastrous consequences not only for these animals.
Jim West, a researcher who works with the No Spray Coalition gives a very interesting view on the close correlation of the ‘West Nile virus encephalitis’ in New York City in 1999, with the very high levels of atmospheric pollution, air toxins

References Malathion

Literature references Malathion.
Internet references Malathion.

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Last update: June 6th 2009
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