Pesticides have played a significant role in protecting crops, controlling pests and weeds, and increasing the yield of crops. They have also improved the human living environment and improved the people’s production and living standards. However, the resulting environmental pollution problems and negative effects on the human body have also attracted people’s attention. Many countries in the world have already stipulated the limited use of various pesticide residues in food and food.
It is estimated that the annual production capacity of pesticides in China is about 350,000 tons, and the annual control of diseases, insects, weeds, and rodent damage is about 300 million hm2, which can restore about 15% of agricultural product losses. In May 2005, the pesticide inspection institute of the Ministry of Agriculture organized pesticide testing for 50 vegetable varieties in 5 pesticides in five provinces and cities in Shanghai, Beijing, Chongqing, Shandong and Zhejiang. The rate exceeded 30%. With the enhancement of people's awareness of environmental protection and health awareness, the evaluation of pesticides is no longer confined to its prevention and control of agricultural products against predators and the economic benefits of increased production, but also emphasizes the social benefits of no harm to the environment and health. Therefore, it is of great significance to pay attention to the issue of pesticide residues in agricultural products in China. This article reviews the control of pesticide residues in agricultural products.
1 Concept and current status of pesticide residues Pesticide residues are the general term for trace amounts of pesticides, toxic metabolites, degradants, and impurities that remain in organisms, foods, and the environment after pesticides are used in agriculture. If the pesticide exceeds the maximum residue limit, it will have adverse effects on humans and animals or poison the organisms in the ecosystem through the food chain. The maximum residue limit (abbreviated MRL) refers to the legal maximum allowable concentration of pesticide residues in agricultural and livestock products, that is, the maximum residual concentration in food after using the pesticide in accordance with the pesticide application amount and method specified on the pesticide label. Expressed in mg of pesticide residue per 1 kg of farm animal products. At present, incidents of social poisoning and death caused by the consumption of agricultural products and export of agricultural products that are rejected and returned by foreign countries are mostly caused by pesticide residues in agricultural products exceeding the maximum residue limit.
China is a big country in the production and use of pesticides. Its pesticide use ranks first in the world, its output ranks second in the world, its pesticide active ingredients are more than 400, and its products are more than 7,000. China's pesticides are mainly pesticides, accounting for about 72% of pesticides, fungicides about 11% of pesticides, herbicides about 15% of pesticides, and about 100 pesticides imported from abroad. Although the export volume of pesticides in China exceeds the import volume, there are still some problems: 1 The supply of pesticides exceeds supply, There are more than 1,700 pesticide plants in the country. The production enterprises are small and scattered, and new and better pesticide varieties, many manufacturers As a result, most of the small-scale product quality control is not strict; 2 the structure of pesticide products is irrational. Among the pesticides that account for more than 70% of the total output of pesticides, methamidophos, parathion, methyl parathion, and oxidation Dimethoate, monocrotophos, and other highly toxic and highly toxic species account for about 60% to 70% of pesticides; 3 The majority of farmers in our country lack a correct understanding of the correct use of pesticides, violate pesticide use regulations, use pesticides improperly, and add pesticides to the relevant authorities. Residue supervision is not enough, resulting in more prominent pesticide residues in agricultural and livestock products. If high-toxicity pesticides are used on vegetables and fruits, acute poisoning and the like can be caused by picking and eating them shortly after application.
The main ways of pesticides contaminating agricultural products are: 1 Direct application of pesticides to agricultural products; 2 Pollution of air, water, and soil caused by pesticide residues in plants and indirect pollution; 3 From the food chain and bioconcentration; 4 Caused by improper transport and storage Chemical pollution.
Pesticide residues have become one of the major safety issues for China's agricultural products (mainly cereals and fruits and vegetables).
The results of the quality inspection conducted by the AQSIQ in the third quarter of 2001 showed that the phenomenon of excessive pesticide residues in vegetables was prominent. The first was excessive organic phosphorus, and the second was a phenomenon in which vegetables contained multiple residues.
Since the 1980s, the area under cultivation of greenhouses and greenhouses and other protected vegetables has increased rapidly. Repeated cropping and continuous cropping have led to aggravation of vegetable diseases and insect pests. As a result, the total annual output has been lost by more than 20%. Chemical pesticides are widely used in the prevention and control of vegetable pests and diseases throughout the country. In the cities around the Yangtze River basin, pesticides use 30-45 kg/hm2 per year, and some of them reach 75 kg/hm2 or more. The use of pesticides in northern protected areas is even greater, according to relevant authorities. The survey showed that the amount of vegetables in Beijing suburbs was 135 kg/hm2. Over the years, due to the large and continuous use of chemical pesticides, vegetable pests have caused widespread resistance to chemical pesticides, and farmers have been able to increase the use of pesticides. As a result, the use and dependence of pesticides have shown a vicious cycle. . The heavy use of pesticides has made the problem of excessive pesticide residues in vegetables prominent, and vegetable poisoning accidents have occurred from time to time. In the second half of 2002, Yang Jianglong investigated the residue of organophosphorus pesticides in 9 representative vegetables such as Chinese cabbage, cauliflower and tomatoes in the surrounding suburbs of Xi’an. The results showed that omethoate was detected in 25.43% of the vegetable samples, and The detection rate is much higher than that of other types of organophosphorus pesticides. It is the main residue in vegetables and the detection rates of different pesticides in different vegetables are significantly different. In 1991, Tianjin Leek Poisoning, only Nankai Hospital treated more than 100 poisoned people; in 1991, 1605 from Lakeside Township, Boxing County, Shandong Province, polluted leeks and caused poisoning to 120 people; in the summer of 1997, the high temperature season occurred in Jiangsu Province. There were more than 70 incidents of poisoning caused by excessive use of pesticide residues in vegetables. In 1998, a vegetable farmer in Ningjin County of Shandong Province violated the national regulations on the safe use of pesticides and used “1605†on leeks, causing more than 10 poisonings. 1 People die. According to statistics from the Ministry of Health, there were 37 cases of chronic poisoning of vegetables and foods caused by pesticide residues in China in 1999. Under normal circumstances, acute poisoning can also cause people's attention, and the situation of chronic poisoning and cumulative poisoning is not known. In fact, the result will be even more terrible.
2 Current Status of Pesticide Residue Detection Techniques 2.1 Rapid Detection of Commonly Used Pesticide Residues 2.1.1 The enzyme inhibition method used at this stage is the use of pesticide residue rapid-measuring devices to monitor pesticide residues, in addition to organophosphorus and carbamate pesticides. All of them are inhibitors of the acetylcholinesterase of the nervous system. Therefore, organophosphorus can be detected using the degree of inhibition of the pesticide target enzyme, acetylcholinesterase (AChE), but this method can only be used for the determination of organophosphorus and carbamates. Insecticides are sensitive to the sensitivity of the enzyme used, the reaction time and the temperature of the reaction. After testing positive by enzymatic method, it needs to be further tested with standard instruments to identify residual pesticide species and accurate residue.
2.1.2 ELISA Immunoassay methods include radioimmunoassay, enzyme immunoassay, multi-component analyte immunoassay, and immunosensor analysis. The most commonly used is the enzyme-linked immunosorbent assay (ELISA), which is based on the specific and reversible binding of antigens and antibodies. However, due to the large number of pesticides, antibody preparation is difficult, there is a certain degree of blindness in the determination of pesticide residues in the sample, and the dependence of antibodies on foreign imports, the scope of application of enzyme-linked immunoassay is greatly limited.
2.2 Physical and Chemical Detection of Pesticide Residues 2.2.1 Immunoassay Immunoassay assays are based on antigen-antibody specific recognition and binding reactions. High molecular weight pesticides can directly enter the vertebrate body as an antigen to produce an immune response, thereby obtaining antibodies that can specifically bind to the pesticide molecules; pesticides with a small molecular weight (molecular weight < 2500) generally do not have immune resistance and do not stimulate the animals to produce immune response. This method has the advantages of being quick, simple, sensitive and selective.
2.2.2 Capillary electrophoresis Capillary electrophoresis is a separation technique developed on the basis of electrophoresis technology. The working principle is that the different charged particles in the capillary are directed and migrated in the background buffer at different speeds under the action of the high pressure field to separate them. It is characterized by high sensitivity, low cost, low sample usage, and ease of use.
2.2.3 Liquid Chromatography Liquid chromatography is a chromatographic method using liquid as the mobile phase. It can be used for separation and detection of strong polarity, high molecular weight, and ionic pesticides. It can be used for easily decomposing pesticides that are difficult to vaporize or heat. Testing. In recent years, a new type of high-efficiency and high-sensitivity detectors, precolumn and postcolumn derivatization technologies, and computer linkages have been used to greatly increase detection efficiency, sensitivity, detection speed, and automation of operations.
3 Countermeasures for Control of Pesticide Residues Effective control of pesticide residue contamination in agricultural products is a systematic project that includes policies, legislation, management, and technology, and requires multiple efforts to achieve both the symptoms and the root causes.
3.1 Scientifically controlling the use of pesticides should strictly abide by the "Pesticide Safety Use Regulations" and "Pesticide Safety Use Standards" and other provisions, prevention-oriented, comprehensive prevention and control. High-toxic and high-residual pesticides shall not be used in crops such as fruit trees, vegetables, Chinese medicinal materials, and tobacco. It is forbidden to use pesticide poisons to kill fish, shrimps, frogs and beneficial birds and beasts. Pesticides must be applied within safe intervals.
3.2 Strengthening supervision of pesticide residues At present, although China has announced regulations for pesticides, formulated standards for the safe use of pesticides, guidelines for the rational use of pesticides, and methods for detecting pesticide residues, there are few mandatory regulations and there is no corresponding penalty clause. Problems such as the quality of pesticides and pesticide poisoning cannot be followed, which is the main reason for the frequent occurrence of pesticide poisoning accidents in China. Therefore, it is necessary to increase government involvement, formulate appropriate legal monitoring mechanisms, publicize the hazards of pesticide residues, and let the community generally pay attention to this issue so as to raise the awareness of safety and environmental protection among farmers and pesticide manufacturers.
3.3 Adjust pesticide product structure Phase out high-toxicity and high-residue pesticide products. In 2002, the registration of newly approved methamidophos, methyl parathion, parathion, monocrotophos, and phosphoammonium five highly toxic organophosphorus pesticides (including mixtures) was stopped, and methyl parathion (including mixed) was withdrawn. Agent) Registration used on fruit trees. For those products that have been approved for registration and contain the above five highly toxic organophosphorus pesticides, a timetable will be established with the relevant departments, and the use of these products will be gradually restricted until the registration is cancelled and the use stops. From 2001 to 2003, all other highly toxic pesticide products registered, including mixed preparations containing highly toxic active ingredients, will be completely cleaned up and rectified, and measures such as restricting the scope of registration and cancellation of partial product registration will be adopted to reduce highly toxic pesticides. The proportion of registered products. On the basis of further investigation and study, through the formulation of pesticide structural adjustment plans, the registration of highly toxic and highly toxic pesticides will be phased out, and a batch of alternative products will be recommended to pesticide users. Support and encourage manufacturers to develop and develop safe, efficient and economical new pesticide products, and control the hazards of highly toxic pesticide residues to humans, livestock and the environment from the source. At the same time, regular announcements were made to the society recommending high-quality pesticide products suitable for the production of pollution-free agricultural products. One or two batches were issued each year to guide producers to choose the right pesticide products.
3.4 Establish a standard system for the development of pollution-free agricultural products Based on a thorough study of pesticide residues both at home and abroad, study and formulate guidelines for the rational use of 3 batches of more than 100 pesticides, 10 to 20 national or industry standards for comprehensive pest control and technical regulations, and 19 types of pesticides. The above national standards and industry standards for pesticide residue testing methods, and national and industrial standards for the highest residue levels of pesticides in 18 agricultural products have basically improved the pesticide residue limit standard system for agricultural products in China.
It is estimated that the annual production capacity of pesticides in China is about 350,000 tons, and the annual control of diseases, insects, weeds, and rodent damage is about 300 million hm2, which can restore about 15% of agricultural product losses. In May 2005, the pesticide inspection institute of the Ministry of Agriculture organized pesticide testing for 50 vegetable varieties in 5 pesticides in five provinces and cities in Shanghai, Beijing, Chongqing, Shandong and Zhejiang. The rate exceeded 30%. With the enhancement of people's awareness of environmental protection and health awareness, the evaluation of pesticides is no longer confined to its prevention and control of agricultural products against predators and the economic benefits of increased production, but also emphasizes the social benefits of no harm to the environment and health. Therefore, it is of great significance to pay attention to the issue of pesticide residues in agricultural products in China. This article reviews the control of pesticide residues in agricultural products.
1 Concept and current status of pesticide residues Pesticide residues are the general term for trace amounts of pesticides, toxic metabolites, degradants, and impurities that remain in organisms, foods, and the environment after pesticides are used in agriculture. If the pesticide exceeds the maximum residue limit, it will have adverse effects on humans and animals or poison the organisms in the ecosystem through the food chain. The maximum residue limit (abbreviated MRL) refers to the legal maximum allowable concentration of pesticide residues in agricultural and livestock products, that is, the maximum residual concentration in food after using the pesticide in accordance with the pesticide application amount and method specified on the pesticide label. Expressed in mg of pesticide residue per 1 kg of farm animal products. At present, incidents of social poisoning and death caused by the consumption of agricultural products and export of agricultural products that are rejected and returned by foreign countries are mostly caused by pesticide residues in agricultural products exceeding the maximum residue limit.
China is a big country in the production and use of pesticides. Its pesticide use ranks first in the world, its output ranks second in the world, its pesticide active ingredients are more than 400, and its products are more than 7,000. China's pesticides are mainly pesticides, accounting for about 72% of pesticides, fungicides about 11% of pesticides, herbicides about 15% of pesticides, and about 100 pesticides imported from abroad. Although the export volume of pesticides in China exceeds the import volume, there are still some problems: 1 The supply of pesticides exceeds supply, There are more than 1,700 pesticide plants in the country. The production enterprises are small and scattered, and new and better pesticide varieties, many manufacturers As a result, most of the small-scale product quality control is not strict; 2 the structure of pesticide products is irrational. Among the pesticides that account for more than 70% of the total output of pesticides, methamidophos, parathion, methyl parathion, and oxidation Dimethoate, monocrotophos, and other highly toxic and highly toxic species account for about 60% to 70% of pesticides; 3 The majority of farmers in our country lack a correct understanding of the correct use of pesticides, violate pesticide use regulations, use pesticides improperly, and add pesticides to the relevant authorities. Residue supervision is not enough, resulting in more prominent pesticide residues in agricultural and livestock products. If high-toxicity pesticides are used on vegetables and fruits, acute poisoning and the like can be caused by picking and eating them shortly after application.
The main ways of pesticides contaminating agricultural products are: 1 Direct application of pesticides to agricultural products; 2 Pollution of air, water, and soil caused by pesticide residues in plants and indirect pollution; 3 From the food chain and bioconcentration; 4 Caused by improper transport and storage Chemical pollution.
Pesticide residues have become one of the major safety issues for China's agricultural products (mainly cereals and fruits and vegetables).
The results of the quality inspection conducted by the AQSIQ in the third quarter of 2001 showed that the phenomenon of excessive pesticide residues in vegetables was prominent. The first was excessive organic phosphorus, and the second was a phenomenon in which vegetables contained multiple residues.
Since the 1980s, the area under cultivation of greenhouses and greenhouses and other protected vegetables has increased rapidly. Repeated cropping and continuous cropping have led to aggravation of vegetable diseases and insect pests. As a result, the total annual output has been lost by more than 20%. Chemical pesticides are widely used in the prevention and control of vegetable pests and diseases throughout the country. In the cities around the Yangtze River basin, pesticides use 30-45 kg/hm2 per year, and some of them reach 75 kg/hm2 or more. The use of pesticides in northern protected areas is even greater, according to relevant authorities. The survey showed that the amount of vegetables in Beijing suburbs was 135 kg/hm2. Over the years, due to the large and continuous use of chemical pesticides, vegetable pests have caused widespread resistance to chemical pesticides, and farmers have been able to increase the use of pesticides. As a result, the use and dependence of pesticides have shown a vicious cycle. . The heavy use of pesticides has made the problem of excessive pesticide residues in vegetables prominent, and vegetable poisoning accidents have occurred from time to time. In the second half of 2002, Yang Jianglong investigated the residue of organophosphorus pesticides in 9 representative vegetables such as Chinese cabbage, cauliflower and tomatoes in the surrounding suburbs of Xi’an. The results showed that omethoate was detected in 25.43% of the vegetable samples, and The detection rate is much higher than that of other types of organophosphorus pesticides. It is the main residue in vegetables and the detection rates of different pesticides in different vegetables are significantly different. In 1991, Tianjin Leek Poisoning, only Nankai Hospital treated more than 100 poisoned people; in 1991, 1605 from Lakeside Township, Boxing County, Shandong Province, polluted leeks and caused poisoning to 120 people; in the summer of 1997, the high temperature season occurred in Jiangsu Province. There were more than 70 incidents of poisoning caused by excessive use of pesticide residues in vegetables. In 1998, a vegetable farmer in Ningjin County of Shandong Province violated the national regulations on the safe use of pesticides and used “1605†on leeks, causing more than 10 poisonings. 1 People die. According to statistics from the Ministry of Health, there were 37 cases of chronic poisoning of vegetables and foods caused by pesticide residues in China in 1999. Under normal circumstances, acute poisoning can also cause people's attention, and the situation of chronic poisoning and cumulative poisoning is not known. In fact, the result will be even more terrible.
2 Current Status of Pesticide Residue Detection Techniques 2.1 Rapid Detection of Commonly Used Pesticide Residues 2.1.1 The enzyme inhibition method used at this stage is the use of pesticide residue rapid-measuring devices to monitor pesticide residues, in addition to organophosphorus and carbamate pesticides. All of them are inhibitors of the acetylcholinesterase of the nervous system. Therefore, organophosphorus can be detected using the degree of inhibition of the pesticide target enzyme, acetylcholinesterase (AChE), but this method can only be used for the determination of organophosphorus and carbamates. Insecticides are sensitive to the sensitivity of the enzyme used, the reaction time and the temperature of the reaction. After testing positive by enzymatic method, it needs to be further tested with standard instruments to identify residual pesticide species and accurate residue.
2.1.2 ELISA Immunoassay methods include radioimmunoassay, enzyme immunoassay, multi-component analyte immunoassay, and immunosensor analysis. The most commonly used is the enzyme-linked immunosorbent assay (ELISA), which is based on the specific and reversible binding of antigens and antibodies. However, due to the large number of pesticides, antibody preparation is difficult, there is a certain degree of blindness in the determination of pesticide residues in the sample, and the dependence of antibodies on foreign imports, the scope of application of enzyme-linked immunoassay is greatly limited.
2.2 Physical and Chemical Detection of Pesticide Residues 2.2.1 Immunoassay Immunoassay assays are based on antigen-antibody specific recognition and binding reactions. High molecular weight pesticides can directly enter the vertebrate body as an antigen to produce an immune response, thereby obtaining antibodies that can specifically bind to the pesticide molecules; pesticides with a small molecular weight (molecular weight < 2500) generally do not have immune resistance and do not stimulate the animals to produce immune response. This method has the advantages of being quick, simple, sensitive and selective.
2.2.2 Capillary electrophoresis Capillary electrophoresis is a separation technique developed on the basis of electrophoresis technology. The working principle is that the different charged particles in the capillary are directed and migrated in the background buffer at different speeds under the action of the high pressure field to separate them. It is characterized by high sensitivity, low cost, low sample usage, and ease of use.
2.2.3 Liquid Chromatography Liquid chromatography is a chromatographic method using liquid as the mobile phase. It can be used for separation and detection of strong polarity, high molecular weight, and ionic pesticides. It can be used for easily decomposing pesticides that are difficult to vaporize or heat. Testing. In recent years, a new type of high-efficiency and high-sensitivity detectors, precolumn and postcolumn derivatization technologies, and computer linkages have been used to greatly increase detection efficiency, sensitivity, detection speed, and automation of operations.
3 Countermeasures for Control of Pesticide Residues Effective control of pesticide residue contamination in agricultural products is a systematic project that includes policies, legislation, management, and technology, and requires multiple efforts to achieve both the symptoms and the root causes.
3.1 Scientifically controlling the use of pesticides should strictly abide by the "Pesticide Safety Use Regulations" and "Pesticide Safety Use Standards" and other provisions, prevention-oriented, comprehensive prevention and control. High-toxic and high-residual pesticides shall not be used in crops such as fruit trees, vegetables, Chinese medicinal materials, and tobacco. It is forbidden to use pesticide poisons to kill fish, shrimps, frogs and beneficial birds and beasts. Pesticides must be applied within safe intervals.
3.2 Strengthening supervision of pesticide residues At present, although China has announced regulations for pesticides, formulated standards for the safe use of pesticides, guidelines for the rational use of pesticides, and methods for detecting pesticide residues, there are few mandatory regulations and there is no corresponding penalty clause. Problems such as the quality of pesticides and pesticide poisoning cannot be followed, which is the main reason for the frequent occurrence of pesticide poisoning accidents in China. Therefore, it is necessary to increase government involvement, formulate appropriate legal monitoring mechanisms, publicize the hazards of pesticide residues, and let the community generally pay attention to this issue so as to raise the awareness of safety and environmental protection among farmers and pesticide manufacturers.
3.3 Adjust pesticide product structure Phase out high-toxicity and high-residue pesticide products. In 2002, the registration of newly approved methamidophos, methyl parathion, parathion, monocrotophos, and phosphoammonium five highly toxic organophosphorus pesticides (including mixtures) was stopped, and methyl parathion (including mixed) was withdrawn. Agent) Registration used on fruit trees. For those products that have been approved for registration and contain the above five highly toxic organophosphorus pesticides, a timetable will be established with the relevant departments, and the use of these products will be gradually restricted until the registration is cancelled and the use stops. From 2001 to 2003, all other highly toxic pesticide products registered, including mixed preparations containing highly toxic active ingredients, will be completely cleaned up and rectified, and measures such as restricting the scope of registration and cancellation of partial product registration will be adopted to reduce highly toxic pesticides. The proportion of registered products. On the basis of further investigation and study, through the formulation of pesticide structural adjustment plans, the registration of highly toxic and highly toxic pesticides will be phased out, and a batch of alternative products will be recommended to pesticide users. Support and encourage manufacturers to develop and develop safe, efficient and economical new pesticide products, and control the hazards of highly toxic pesticide residues to humans, livestock and the environment from the source. At the same time, regular announcements were made to the society recommending high-quality pesticide products suitable for the production of pollution-free agricultural products. One or two batches were issued each year to guide producers to choose the right pesticide products.
3.4 Establish a standard system for the development of pollution-free agricultural products Based on a thorough study of pesticide residues both at home and abroad, study and formulate guidelines for the rational use of 3 batches of more than 100 pesticides, 10 to 20 national or industry standards for comprehensive pest control and technical regulations, and 19 types of pesticides. The above national standards and industry standards for pesticide residue testing methods, and national and industrial standards for the highest residue levels of pesticides in 18 agricultural products have basically improved the pesticide residue limit standard system for agricultural products in China.
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