Leptophos is an organophosphates, which at room temperature it is represented as a stable white solid. Leptophos primarily usage was as a pesticide for grasshoppers, fleas and beetles, fungicide for rice, cotton, fruit and vegetables until its use was discontinued in 1975 in USA, but still sold in South-Eastern Asia until 1981.
Leptophos was first discovered to be toxic in 1974, that is the year when more than 1000 water buffaloes died after being exposed to leptophos in Egypt. As a response, the effect of leptophos was investigated on chickens, mice and sheep.
In Egypt, leptophos used on cotton in 1971 caused the death of more than 1000 water buffalos and a number of farmers. The chemical was never allowed to be used for domestic use by the Environmental Protection Agency but was exported from the U.S. to at least 30 countries. Leptophos was discontinued for use in late 1975 due to its high toxicity.
One of the first group of people who acted against the chemical were workers in the Velsicol’s chemical plant in Bayport, Texas, 1976. They reported serious neurological symptoms and filed a lawsuit against the company. When Colombia banned leptophos in 1977, the American company Velsicol stopped the production and shipped its Colombian stocks to El Salvador. However, no prohibitions exist in El Salvador.
There are no substantial advantages other than that it was used as a pesticide and fungicide for rice, cotton and other vegetables. However, there are tons of disadvantages that come with using leptophos, hence why it was banned. They include several nerve symptoms, which also brought the death of more than 1000 water buffalos and also come with the symptoms that any other organophosphate has, which are listed below.
The symptoms that come, when somebody comes in contact with an organophosphate are: skin rash, itching, and burning of the skin, numbness of hands and the face, cramps in the face, neck and limbs. Chest pain, shortness of breath, difficulties with breathing, wheezing, runny nose, irritation of the throat and cough. Excessive sweating, nausea, vomiting, diarrhea, excessive salivation, abdominal pain, burning on urination and poor appetite.
Lacrimation and irritation of the eyes. If both symptoms were observed the patient was considered to have eye problems due to the poisoning. Trembling hands difficulty in seeing, irritability, forgetfulness, restlessness and difficulties falling asleep.
Leptophos is stable at normal temperatures. At 180 degrees Celsius, more than 85 percent of the material is decomposed in 5 hours, and at 208 degrees Celsius it decomposes in 2 hours. Leptophos is hydrolyzed slowly under alkaline conditions. The material is stable toward acids.
Leptophos is an inhibitor of cholinesterase’s in vitro, this means that the cholinesterase, an example would be acetylcholinesterase, converts the neurotransmitter acetylcholine into the inactive metabolites acetate and choline.
Acetylcholine receptors are of two types. One is a fast-acting ion-channel controlled receptor, and the second one is a slow-acting receptor that acts through guanine nucleotide-binding protein that stimulates second-messengers to indirectly open ion-channels.
When leptophos binds to the AChE, the acetylcholine does not get inactivated. This interferes with a normal signal transfer. This means that a nerve signal can’t get transmitted in the way it should be and leads to a broad range of clinical symptoms.
Leptophos is excreted in urine and feces as several components. Several components found in urine such as O-methyl phenyl phosphate, which is a major component in rat urine, O-methyl phenyl phosphoric, which is a major component in mice urine, and leptophos phenol. The difference in metabolism between species can explain the difference in major metabolites between mice and rats.
Studies in plants indicated that leptophos was slowly absorbed following a foliar treatment with the major quantity found to remain on the leaf surface. Studies with several leaf types (bean – lettuce) showed that residues diminished rapidly on both types of surfaces.
The primary mechanism by which leptophos was lost was presumed to be by volatilization. Additionally, leptophos was metabolized to products similar to those found with the mouse.
A chemical that successfully replaced Leptophos is Chlorpyrifos, which is an organophosphate pesticide used to kill a number of pests including insects and worms. It was introduced by Dow Chemical company, and it acted on the nervous system of insects by inhibiting acetylcholinesterase.
The damage that Leptophos has made to the environment is the main reason of why more than 1000 water buffalos died, and why people who were working, and handling this chemical had several nerve problems. Not only that this chemical is lethal, but it also bio accumulates. This would mean that the highest trophic level would get the most of this pesticide, which would put most of the tertiary and secondary consumers at risk of being killed by this pesticide. This is one of the reason why this chemical is incredibly lethal and has been banned from commercial use. However, the toxicity levels differ from species to species based on their trophic level.
In a final consideration, leptophos is a chemical that was used as a pesticide and fungicide. It has been banned by the EPA in 1975 because it has been discovered that the chemical bio accumulates and causes severe symptoms when it interacts with organisms. An example would be the deaths of more than 1000 water buffalos who had come in contact with this lethal chemical.