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, Florida. The technical grade is approximately 10 times stronger 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 being sprayed with in Florida had been "baking" in the hot summer sun which research finds converts it into an even more toxic compound. If malathion was as safe as proponents state - why did 5 men die and 2,800 become severely ill out of 7,500 Pakistani spraymen who sprayed malathion poison? Could it be possible the hidden chemical ingredients that make malathion drastically more toxic? - Centers for Disease Control, Atlanta. Note: 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 - none of which have been tested or included in malathion’s MSDS! 

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/contaminants, actually increase in amounts during simple storage [especially 3-6 months after manufacture], making malathion far more toxic than when it was first formulated! 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. Journal of Agricultural Food Chemistry, 25 (4) : 946-953, 1977. 

Two studies showing how technical grade malathion poison contains chemical impurities which can 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). 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. Obviously, the consequences of not having these lymphocytes remove viruses or cancer efficiently could result from either mild to serious health disorders. Journal of Immunology, 140 (2) : 564-570, University of Virginia. 

In trying to calm the fears of Tampa residents, spokespeople for Florida Department of Agriculture have make public statements that after application, malathion "breaks down" in a matter of hours.. What they don’t tell you is that malathion can actually breakdown 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, biolocated or converted into more dangerous chemicals." 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 breakdown 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, Hacetepe University, Turkey. 

A favorite tactic of pro-malathion supporters is to use the phrase "less toxic than salt." However, it is important to realize that the word toxic in this context refers only to malathion’s ability not to cause immediate death in laboratory animals. Not only is this seriously inaccurate due to the impurities which can form during storage and heat are present only in technical malathion, but we also have to consider malathion’s ability to harm life in other ways. This can include weakening the immune system and the body’s ability to fight infections, gradual damage to the nervous system during pregnancy, the ability to cause accelerated aging to organs such as the liver and kidneys, as well as the potential to accelerate damage to the genes on the DNA molecule. Again, none of these health effects are considered when using the word "toxic" - only immediate death. 

Malathion does not appear to produce point mutations in standard gene mutation assays in bacteria, but its metabolite malaoxon (94% pure) was positive in mammalian cell mutation tests. In their haste to "completely eradicate" the medfly in the Tampa, Fla., region, Florida agriculture department officials may have violated some of the terms of their Section 18 quarantine exemption an aerial malathion spraying. At least one biologist responsible for collecting water samples and testing for malathion said he believed that levels of the chemical was increasing in local waterways, and might soon pose an acute toxicity threat to fish and other wildlife. 

Citizens in or near the spray zones around Tampa and Hillsborough County had been flooding a Medfly Spraying Hotline and the Hillsborough County EPC with phone calls saying that wetlands, lakes and streams had been sprayed, neighborhoods that had not yet been officially designated had been sprayed, and that spraying had occurred during rainstorms. Two people told Pesticide Report that they had been sprayed, or witnessed malathion sprayings, while standing at or near bodies of water. Richard Bowler, a biologist with the Hillsborough County Environmental Protection Commission, said he was collecting water samples for analysis in mid-June at Rocky Creek near Hillsborough Avenue, when he was sprayed. "You could see the mist coming out of the helicopter nozzles, and I felt it on my face," he remarked. Bowler also reported that it has rained in Tampa and Hillsborough County almost every day for the last 10 days in June, and that the spraying has continued, unabated, despite the exemption condition prohibitions on spraying close to or during periods of rainfall. EPA fined two DC3’s (aerial applicators) $20,000 that dumped their malathion "rinse water" into the Gulf of Mexico! Obviously, misuse increases the danger to us, but not to the medfly - which was not finally controlled in Florida by malathion, but by sterile medflies.

Sincerely, Stephen L. Tvedten