Tetraethyl lead

The antiknock effect of thermal power plants was first discovered in 1921 in the USA by General Motors . In 1923, the three largest US corporations General Motors, DuPont , and Standard Oil formed a joint venture called Ethyl Gasoline Corporation. The name "ethyl" was chosen specifically so as not to frighten people with the word "lead". The author of this invention, Thomas Midgley, was well aware of the dangers of lead poisoning. Almost immediately, workers in the workplace began to appear unstable gait and mental disorders. So in 1924, on one poorly ventilated installation, five workers died in a few days and thirty-five became disabled. Ethyl Corporation has always followed the practice of firmly denying the toxicity of its products ^[2] . Over the next few decades, the bulk of gasoline in the States contained thermal power plants.

The harmful effects caused by lead have been known since the late forties - early fifties. In 1965, the stubborn struggle to ban tetraethyl lead was launched by the American geophysicist Claire Cameron Patterson . Collecting data on the catastrophic increase in lead in the atmosphere and on its accumulation in humans, Patterson argued the need to prohibit the use of this substance. However, for a long time no measures were taken due to the strong lobby of the fuel producers.

However, in 1972, the US Environmental Pollution Prevention Agency (EPA) banned the use of thermal power plants and the production of engines designed for leaded gasoline; a lawsuit from manufacturers followed. The EPA won the process, and in 1976 a gradual displacement of TPP-containing fuel began, which was completed by 1986. According to research, by 1994, lead in the blood of Americans decreased by 78% compared with 1978.

Tetraethyl lead was widely used including in the USSR . A dye was added to the motor gas containing it for marking purposes: until 1979, the AI93, A-76, and A-66 gasoline containing tetraethyl lead were painted in blue, green, orange, respectively, and unleaded A-72 was not painted ^[3] . Since 1979, leaded gasoline began to be painted in orange-red (AI-93), yellow (A-76), blue (AI-98) ^[4] , green (A-66) or pink (A-72) colors ^[5] . The instructions introduced requirements for observing safety measures when working with fuel and fuel equipment of automobiles. Since the late 1970s ( GOST 2084–77), the process of abandoning the use of thermal power plants began, ending in the 2000s.

In the European Union, leaded gasoline was banned on January 1, 2000, although most member states introduced a similar ban much earlier. Great Britain continues to produce small amounts of levied levy gas. China refused to use a thermal power plant in 2000 ^[6] , but some gasoline is produced for export. In Russia, leaded gasoline was banned on November 15, 2002 ^[7] .

Thus, due to the high carcinogenic activity of tetraethyl lead and environmental pollution by lead when using it, to date, the addition of tetraethyl lead to fuel has been largely abandoned. Another reason for not using tetraethyl lead is the use of catalytic converters in modern cars, since tetraethyl lead is the cause of the converter failure ^[8] . Tetraethyl lead continues to be added to aviation gasoline ^[9] and fuel for some racing engines. However, leaded gasoline is still used in underdeveloped countries like Yemen, Palestine, Afghanistan or North Korea because of the relative cheapness and ease of production.

Instead of TPPs, less harmful high-octane additives, such as ferrocene or methyl tert-butyl ether, are currently used. In some countries, ethanol , which also has a rather high octane number, is used as an additive.

Tetraethyl lead is a colorless oily volatile liquid with a density of 1.65 g / cm³ and a boiling point of 80 ° C with decomposition.

Tetraethyl lead is obtained by reacting ethyl chloride C ₂ H ₅ Cl and a lead alloy with sodium PbNa (about 10% Na).

Tetraethyl lead is a volatile poisonous liquid that at a temperature of 0 ° passes into a vaporous state and penetrates the body through the upper respiratory tract . Tetraethyl lead can also enter the body through intact skin . This substance is a strong poison that selectively affects the nervous system , causing acute, subacute and chronic poisoning. The latter are due to the functional cumulation inherent in this toxic substance.

Most poisoning is acute and subacute. The cortex of the brain is primarily affected. In the area of ​​the autonomic centers of the diencephalon, a focus of stagnant excitation arises, which leads to gross violations of the cortical-subcortical interconnections.

Pathogenesis

In the pathogenesis of tetraethyl lead poisoning, a certain role is played by a violation of enzymatic processes, leading to the development of degenerative changes in nerve cells against the background of severe vascular disorders ( hyperemia , edema, hemorrhage ).

In the development of the clinical picture of acute poisoning (in case of accidental ingestion of leaded gasoline, in case of accidental contact with it on a large surface of the skin), 3 stages are distinguished - initial, preculminating and climax.

In the initial stage , pronounced vegetative disorders are noted: hypothermia , arterial hypotension and bradycardia , hypersalivation due to sleep disturbance, fear of death at night, anxious, depressed mood, headache, general weakness (vegetative-asthenic syndrome). In this period, peculiar paresthesias are observed in the form of a sensation of a ball of hair or threads on the tongue.

In the pre-climax stage , pronounced mental disorders are manifested: the fear of death begins to bother the patient not only at night, but also during the day; auditory, visual, tactile hallucinations of a frightening nature, delusions of persecution and relationships appear. Under the influence of delirium, psychomotor agitation develops; patients become aggressive; cases are not uncommon when, trying to save their lives from supposedly persecuting persons, patients were thrown out of windows. The clinical picture shows signs of organic brain damage: ataxia, intentional tremor, nystagmus , anisoreflexia, dysarthria, euphoria.

At the culmination stage, psychomotor agitation reaches maximum tension. Consciousness in patients is confused. It seems to them that they are being cut into pieces, that snakes encircle their body, etc. Epileptic seizures may develop. At the height of psychomotor agitation, hypothermia is replaced by hyperthermia (up to 40 ° C), arterial hypotension - by hypertension, bradycardia - by tachycardia. The pronounced dystonia of the vegetative centers can lead to the development of a collapse ending in death.

In those cases when delirium is delayed, the prognosis is favorable. The psychomotor agitation is replaced by a vegetative-asthenic state. Mental defects, emotional dullness , decreased intelligence, loss of interest in the environment, etc. can remain.

Chronic Poisoning

Chronic poisoning is possible in individuals who have been in prolonged contact with small doses of tetraethyl lead. The clinical picture of poisoning, as with other intoxications, in the initial stages is characterized by a vegetative-asthenic state, when increased fatigue, decreased memory and attention, anxious, intermittent sleep, emotional instability, bradycardia, arterial hypotension, hypothermia, hypersalivation, hyperhidrosis. The initial stage of chronic tetraethyl lead poisoning, as with poisoning by other poisons, is reversible.

The next stage, which develops as chronic poisoning increases, is characterized by the appearance of organic changes in the brain. These are various forms of encephalopathy with severe mental disorders (anxiety, fear, hallucinations) against the background of symptoms such as nystagmus, dysarthria, ataxia, intentional tremor, anisoreflexia, and decreased intelligence.

The third stage in chronic poisoning with tetraethyl lead is rare and proceeds as a toxic psychosis.

Treatment

To normalize cortical-subcortical relationships, sleeping pills ( barbiturates ), hexenal , chlorpromazine , and drugs (except morphine , which gives a paradoxical effect, enhancing arousal) are recommended. Intravenous glucose with B vitamins and ascorbic acid, dehydrating agents (glucose, magnesium sulfate), as well as cardiac and vascular agents (with collapse) are also prescribed.

Prevention of intoxication with tetraethyl lead and its mixtures requires further improvement of the technological process and an increase in work culture. If tetraethyl lead gets on the skin, you must immediately remove it with kerosene or gasoline. At the end of the work, you must systematically use the shower. Once every three months it is necessary to conduct medical examinations of people working in factories producing Tetraethyl Lead, and once every 12 months - people working with leaded gasoline. Medical examinations are necessary for the timely detection of initial forms of intoxication. A neurologist and therapist must necessarily participate in medical examinations, other specialists - as necessary.

According to the influential hypothesis proposed to explain fluctuations in crime rates in the second half of the 20th and beginning of the 21st centuries, poisoning with tetraethyl lead in childhood entailed a disruption in the development of the central nervous system , resulting in an increase in delinquent behavior in adulthood, which led to an increase crime from the 1960s to the early 1990s . The decline in crime since the 1990s, according to this hypothesis, is due to a decrease in the consumption of gasoline made using tetraethyl lead since the 1970s. ^[ten]

• Traffic fumes
• Carcinogen
• Ethyl fluid