Organophosphorus pesticides refer to organic compound pesticides containing phosphorus elements.It is mainly used to control plant diseases, insects and weeds.Most of them are oily liquid, with garlic smell, strong volatility, slightly soluble in water, and damaged by alkali.In practical application, varieties with high efficiency, low toxicity and low residue should be selected, such asDimethoate、TrichlorfonEtc.Its wide use in agricultural production has led to residues of different degrees in crops.The harm of organophosphorus pesticides to human body is mainly acute toxicity, which mostly occurs after large doses or repeated exposure, and a series of neurotoxicity symptoms will appear, such as sweating, tremor, mental disorder, language disorder, and even respiratory paralysis, even death, in serious cases.[1]
Chinese name
Organophosphorus pesticide
Foreign name
organophosphorus pesticide
Role
Control plant diseases, pests and pests
Physical and chemical properties
Most of them are in the form of oil or crystal
Interpretation
Organic compound pesticide containing phosphorus element
The vast majority of organophosphorus pesticides produced in China are pesticides, such as those commonly usedParathion、Phosphorus uptake、malathion、Dimethoate、TrichlorfonanddichlorvosIn recent years, organophosphorus pesticides such as fungicides and rodenticides have been synthesized successively.Organophosphorus pesticides are mostly phosphate or thiophosphate.
The harmful effects of organophosphorus pesticides on human beings vary from highly toxic to low toxic.It can inhibit acetylcholinesterase, make acetylcholine accumulate, and cause muscarinic symptoms, nicotine like symptoms and central nervous system symptoms. In serious cases, it can cause death due to pulmonary edema, brain edema, and respiratory paralysis.Delayed sudden death may also occur in patients with severe acute poisoning.Some kinds of organophosphorus poisoning can cause delayed neuropathy 8 to 14 days after poisoning, and the blood cholinesterase activity of organophosphorus poisoning patients is reduced.[2]
type
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There are many kinds of organophosphorus pesticides. According to their toxicity, they can be divided into three categories: highly toxic, toxic, and low toxic. The majority of commonly used organophosphorus pesticides in China have oral LD50 (mg/kg) as follows:Parathion(1605) is 3.5 ～ 15mg;Phosphorus uptake(1059) is 4-10mg;Phorate(3911) is 2.1~3.7 mg;Ethyl phosphate4 mg;Thiotep5mg;Phosphoamine7.5 mg (above is highly toxic).dichlorvos50 ～ 110mg;Methyl parathion(methyl 1065) is 14-42 mg;Methyl phosphorus absorption(methyl 10594044) is 80~130mg (above is toxic),Trichlorfon450 ～ 500mg;Dimethoate230~450mg;malathion(4049, marathon) 1800mg;Dibromophos430 mg;Fenitrothion(fenitrothion) is 250mg (above is low toxic).A small amount of highly toxic organophosphorus pesticides can be poisoned, while a large amount of low toxic organophosphorus pesticides can also cause harm if they enter the body.The toxic dose and lethal dose of organic phosphorus vary greatly in human body, and the poisoning symptoms are serious and acute when inhaled from the digestive tract into the respiratory tract or absorbed by the skin with a higher concentration;However, if a large amount or high concentration of organophosphorus pesticides are inhaled, the disease can occur within 5 minutes and quickly cause death.
Physical and chemical properties
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Organophosphorus pesticides are mostly oily or crystalline, and industrial products are light yellow to brown. Except trichlorfon and dichlorvos, most of them have garlic odor.Generally insoluble in water, soluble in organic solvents such asbenzene、acetone、Ether、TrichloromethaneAnd oils, which are relatively stable to light, heat and oxygen, are easy to decompose and damage in case of alkali, with the exception of trichlorfon, which is white crystal and soluble in water, and can be transformed into dichlorvos with greater toxicity in case of alkali.The formulations of organophosphorus pesticides sold on the market mainly includeEmulsifier、Wettable powder、GranuleandpowderFour dosage forms.In recent years, the number of mixtures and compounding agents has gradually increased.
toxicology
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The toxicity of different varieties can be different, most of them are highly toxic and highly toxic, and a few are low toxic.
When some varieties are mixed, they can increase the toxicity, such as malathion and trichlorfon, trichlorfon and fenitrothion.
Some varieties can become more toxic after transformation, for example, after oxidation in 1605, trichlorfon will become dichlorvos in alkaline solution and become more toxic.
Organophosphorus pesticides (organophosphate pesticides) in vivo andcholinesterasePhosphoylated cholinesterase is formed, and the cholinesterase activity is inhibited, making the enzyme unable to play the role of decomposing acetylcholine, causing excessive accumulation of acetylcholine in the tissue, making cholinergic nerve overexcited, causing muscarinic, nicotine like and central nervous system symptoms.Phosphoylcholinesterase esterase generally "ages" after about 48 hours, and is not easy to recover.
Some ester alkyl and aryl alkyl phosphate compounds still have delayed neurotoxicity, which is caused by organophosphorus pesticides inhibiting the neuropathic target esterase (neurotoxic esterase) in the body and aging it.This toxic effect has nothing to do with cholinesterase activity.
Organophosphorus pesticides with sustained release microcapsules can have a longer action time.
Poisoning mechanism
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Organophosphorus pesticides can enter human body through digestive tract, respiratory tract and intact skin and mucosa.Occupational pesticide poisoning is mainly caused by skin pollution.Organophosphorus pesticides absorbed in the body are distributed in various organs, of which the liver has the largest content, and the brain content depends on the ability of pesticides to penetrate the blood-brain barrier.
The organic phosphorus in the body is firstly biotransformed through oxidation and hydrolysis;Oxidation increases toxicity, such as parathion in the smooth endoplasmic reticulum of liverMixed functional oxidaseUnder the action, it is oxidized to paraoxon with greater toxicity;Hydrolysis can reduce toxicity. Parathion is oxidized andPhosphataseLoss of function due to hydrolysis.Secondly, some of the metabolites after oxidation and hydrolysisGlucuronic acidIt reacts with sulfuric acid and is discharged with urine;Partial hydrolysateP-NitrophenolOr p-nitrocresol, etc., is discharged directly through urine without binding reaction.
The main mechanism of organophosphorus pesticide poisoning is inhibitioncholinesteraseActivity.Organic phosphorus combines with cholinesterase to form phosphorylated cholinesterase, which makes cholinesterase lose catalysisacetylcholineHydrolysis, accumulated acetylcholine has three effects on cholinergic nerve:
1. Muscarinic effect
2. Nicotine like effect
3. Central nervous system function
There are two forms of phosphorylated cholinesterase formed by the combination of organic phosphorus and cholinesterase.One combination is unstable, such as parathion, imbibited phosphorus, phorate, etc., some of which can be hydrolyzed and re energized;The other form is completely stable, such as trimethoprim, trichlorfon, dichlorvos, parathion, malathion, etc., which can no longer reactivate the inhibited cholinesterase, which is called cholinesterase aging.
Cholinesterase cannot be reactivated, which can cause delayed effects, such as axonal degeneration of peripheral nerves and long spinal cord bundles, and delayed peripheral neuropathy.
Poisoning performance
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acute poisoning
Clinical manifestations can be divided into three categories:
(1) Muscarinic symptoms: It can appear at an early stage, mainly showing loss of appetite, nausea, vomiting, abdominal pain, diarrhea, salivation, sweating, blurred vision, narrowed pupils, increased secretion of respiratory tract, and even pulmonary edema in severe cases.
(2) Nicotine like symptoms: when the disease gets worse, there will be a feeling of tightness in the whole body, unclear speech, tremor in the chest, upper limbs, face and neck, and even in the muscle bundles of the whole body, a feeling of chest compression, heart rate, elevated blood pressure, and respiratory paralysis in severe cases.
(3) Central nervous system symptoms: dizziness, headache, fatigue, restlessness, ataxia, coma and convulsion in severe cases, often life-threatening due to respiratory center or respiratory muscle paralysis.
(4) Delayed neuropathy: generally, sensory disturbance occurs 8 to 14 days after the remission of acute poisoning symptoms, followed by weakness of lower limbs until flaccid paralysis of the distal lower limbs. In severe cases, upper limbs may be involved, mostly bilateral.
Chronic poisoning
It is mostly found in pesticide factory workers.The prominent manifestation is neurasthenia syndrome and the decrease of cholinesterase activity.Some organophosphorus pesticides can cause bronchial asthma, allergic dermatitis and contact dermatitis.
diagnostic criteria
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According to the history of exposure to a large amount of organic phosphorus, clinical manifestations, and the whole blood cholinesterase activity of acute poisoning.Occupational poisoning can be diagnosed only after comprehensive analysis of the reference work environment and skin pollution detection, urine metabolites detection, food pollution poisoning reference residual food or gastric lavage detection and population epidemiology, and other diseases are excluded.
Observation object
Mild muscarinic, nicotine like symptoms or central nervous system symptoms, and the whole blood cholinesterase activity is not less than 70%;Or there is no obvious clinical manifestation of poisoning, but the whole blood cholinesterase activity is below the first 70%.
Acute mild poisoning
After a short time of contact with a large amount of organophosphorus pesticides, dizziness, headache, nausea, vomiting, sweating, chest tightness, blurred vision, weakness and other symptoms will appear within 24 hours, and the pupils may shrink.The whole blood cholinesterase activity is generally 50%~70%.
Acute moderate poisoning
In addition to the severe symptoms mentioned above, there are also muscle bundle tremor, pupillary constriction, mild dyspnea, salivation, abdominal pain, diarrhea, gait faltering, clear or vague consciousness.The whole blood cholinesterase activity is generally 30%~50%.
Acute severe poisoning
In addition to the above symptoms, one of the following cases can be diagnosed as severe poisoning: (1) pulmonary edema;(2) Coma;(3) Respiratory paralysis;(4) Brain edema.The whole blood cholinesterase activity is generally below 30%.
Delayed neuropathy
In some cases, sensory and motor peripheral neuropathy may occur 2 to 3 weeks after the symptoms of acute severe poisoning disappear. Neurogenic damage is shown by neuro electromyography.
Prevention and control
The main reasons for the high incidence of pesticide poisoning are: backward production technology, lax storage, improper preparation, arbitrary abuse, poor operation and poor protection.Therefore, the focus of prevention is:
1. Reform pesticide production process, especially implement automatic or semi-automatic discharging and packaging;
2. Strictly implement the regulations for safe use of pesticides
(1) Special tools and containers shall be provided for dispensing and seed mixing, and the concentration shall be appropriate to prevent environmental pollution;
(2) When spraying, observe the safety operation rules. The spraying tools are kept and maintained by special personnel to prevent blockage and leakage;
(3) Use pesticides reasonably.Highly toxic pesticides shall not be used to control insects on food crops and fruit trees in the mature period.The use period of pesticides for edible crops or fruit trees shall be strictly specified.It is forbidden to abuse pesticides;
3. Pesticides shall be managed professionally and kept strictly to prevent abuse;
4. Strengthen personal protection and improve people's awareness of self health care.
Poisoning screening for people exposed
1. High risk groups of pesticide poisoning, such as pesticide discharging, packagers and maintenance workers in pesticide plants;In busy farming season, pesticide preparation and application personnel shall take blood cholinesterase as screening index to screen pesticide poisoning regularly.
2. The patients with acute poisoning such as dichlorvos, trichlorfon and malathion were screened by neuroelectromyography after the symptoms of acute poisoning disappeared.Early detection of delayed peripheral neuropathy.
Control of complications of acute pesticide poisoning
The mortality rate of acute organophosphorus pesticide poisoning is high, and there are two peaks of death: (1) In the early stage of rescue, severe inhibition of cholinesterase, pulmonary edema, brain edema, and respiratory and circulatory failure often occur;(2) The "rebound" in the later stage of rescue is mostly caused by incomplete gastric lavage and reabsorption of organic phosphorus or premature withdrawal of atropine.The causes of sudden death in the recovery period are not completely clear, and some are caused by complications or toxic damage to the heart.Therefore, the focus of control is detoxification and detoxification.
Pesticide residue detection method
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Organophosphorus pesticides are gradually moving towards the development trend of ultra-high efficiency and low residue, high efficiency and environmental protection. Their residues in the environment and agricultural products are also very low, and they coexist with a variety of pesticide residues. Especially in developed countries, the established pesticide residue limit standards are often too harsh.This requires trying to eliminate the interference of other substances in the tested sample during detection, which requires the use of highly sensitive detectors.With the development of detection technology, the current detection methods for organophosphorus pesticide residues are increasingly diversified.According to different detection principles, it can be roughly divided into two categories: one is traditional instrument detection, that is, chromatographic techniques:Gas chromatography（GC）、High performance liquid chromatography(HPLC) and chromatography-mass spectrometry technology developed on this basis;The second is based on the principle of biological detection technology:Biosensors, enzyme inhibition testImmunoassayEtc.[3]
Gas chromatography
Gas chromatography is widely used in pesticide residue analysis because of its high efficiency, accuracy and sensitivity.Gas chromatographic analysisFor solid or liquid substances that are easy to gasify and heat stable, it has certain advantages in the detection of organophosphorus pesticide multi residues.
High performance liquid chromatography
Gas chromatography is not suitable for the analysis of pesticide residues that are difficult to gasify, with poor thermal stability and strong polarity. High performance liquid chromatography has become an indispensable analytical method for pesticide residues.
Gas chromatography-mass spectrometry
Gas chromatography-mass spectrometry (GC-MS), with strong anti-interference ability, can complete the qualitative and quantitative work of the substance to be measured at one time. It has become one of the best means for the analysis of organophosphorus pesticide residues and the most commonly used means for researchers at home and abroad.
Liquid chromatography-mass spectrometry
The online combination of liquid chromatography and mass spectrometer has strong anti-interference ability, which can eliminate the interference of unknown components in the matrix, and give the structural information of analytes, which not only improves the sensitivity and accuracy of analysis, but also extends the application range of liquid chromatography.
Biosensors
Because of its simplicity, rapidity, low cost, high sensitivity and good selectivity, many researchers use biosensors to detect organophosphorus pesticide residues.In the actual detection of organophosphorus pesticide residues, researchers at home and abroad pay more attention to enzyme biosensors.Among them, the biosensors with cholinesterase and organophosphate hydrolase as biological activity recognition elements have developed into two dominant types of enzyme biosensors.
Immunoassay technology
In 1971, Ercegovich and others tried to use immunoassay for pesticide residue detection for the first time, and looked forward to the potential advantages of immunoassay in routine pesticide detection.Later, Hammock and Mumma proposed the possibility of using immunoassay to detect pesticides, which was recognized by environmentalists.Grennan uses the recombinant antibody fragments to detect atrazine. The sensor fixes the electropolymer on the surface of the carbon paste electrode, which promotes the electron transfer between the HRP labeled antigen and the electrode surface. The detection limit of the sensor is 0.1ng/mL.
Gold nanoparticles
As a nano material, it has the characteristics of surface effect, quantum size effect, macro quantum tunnel effect, etc., so it shows some unique advantages in continent inspection.Lin experimental group obtained ZrO by hydrothermal methodtwo-SiOtwoNano composite, then gold nanoparticles are introduced on its surface to prepare Au ZrOtwo-SiOtwoThe electrode was modified and used for the detection of ethyl paraoxon. The introduction of gold nanoparticles not only improved the electron transfer rate of the sensor, but also further increased the pesticide adsorption capacity with a large specific surface area. The linear range of the method was 1.0~500ng/mL, and the minimum detection limit was 0.5ng/mL.
Molecular Imprinting Technology
Molecular imprinting technology (MIT) is a new and efficient separation and molecular recognition technology, which has excellent recognition and selectivity.In recent years, this technology has been applied to the detection of pesticide residues and achieved good results.
