Pesticide residues are harmful, how to detect and prevent them?

The use of pesticides is an inevitable step in modern agriculture, but the pesticide residues on agricultural products due to improper use or ineffective detection of pesticides will bring serious harm to the human body, agricultural products and production environment. Understanding the detection standards, causes and hazards of pesticide residues can enable us to better remove and prevent pesticide residues.

1. Standard for pesticide residues

In order to solve the limit standards for vegetables and fruits and agricultural products with Chinese characteristics, and to improve the detection methods matched with the pesticide residue limit standards, the 2016 edition of the maximum residue limits for pesticides in Food, the National Standard for Food Safety, jointly formulated by the State Health and Family Planning Commission, the Ministry of Agriculture and the State Administration of Food and Drug Administration in 2016, was formally promulgated and implemented on January 18, 2017. The new national standard for pesticide residues has made a great breakthrough in the standard quantity and coverage, setting 4140 residue limits for 433 pesticides in 13 categories of agricultural products, an increase of 490 items compared with the 2014 edition. it basically covers the commonly used pesticides that have been approved for use in China and the main agricultural products for daily consumption by residents.

The new pesticide residue limit standard released this time has three major characteristics:

First, the maximum residue limits of 184 pesticides for 24 banned and restricted pesticides, such as benzophos, were established, which provided a basis for judging the supervision of illegal use of prohibited pesticides.

Second, in accordance with international practice, 33 pesticides without dietary risk are exempted from the establishment of MRLs in food, which enhances the scientific, practical and systematic nature of pesticide residue standards in food in China.

Third, in addition to recommending matching detection methods for the limits involved in the standards, 106 national standards for pesticide residue detection methods were issued at the same time.

As the chairman of the Committee on Pesticide residues in the Codex Alimentarius, China is one of the few countries that have participated in the formulation of international standards. During the 12th five-year Plan period, the ability and influence of China to participate in the formulation of international standards has gradually increased. The number of international limit standards using China's residue data has reached 11. At present, the principles, methods and data requirements of dietary risk assessment of pesticide residues in China have been in line with international standards. According to reports, the formulation of pesticide residue standards during the 13th five-year Plan has set out clear tasks and plans: to formulate 6000 pesticide residue limit standards, focusing on solving the limit standards for vegetables, fruits and agricultural products with Chinese characteristics; to improve the detection methods matched with pesticide residue limit standards; to gradually implement the Import limit Standard and uniform limit Standard, and to expand the coverage of China's limit standards. At the same time, we will focus on the independent innovation of pesticides in China, actively participate in the formulation of international Codex Alimentarius standards, and promote the independent innovation of pesticides in China.

two。 Causes of pesticide residues

There are many reasons that lead to and affect pesticide residues, among which the nature of pesticides, environmental factors and the use of pesticides are the main factors affecting pesticide residues.

⑴ Pesticide Properties and Pesticide residues

Organic arsenic, mercury and other pesticides, which have been banned, remain in the environment and plants because their metabolites arsenic and mercury can not be degraded.

Organochlorine pesticides such as BHC and DDT and their metabolites are chemically stable, digest slowly in crops and environment, and are easy to accumulate in human and animal fats. Therefore, although organochlorine pesticides and their metabolites are not highly toxic, the problem of their residual toxicity still exists.

The chemical properties of organophosphorus and carbamate pesticides are unstable and easy to decompose under the influence of external conditions after application. However, there are some highly toxic and highly toxic varieties of organophosphorus and carbamate pesticides, such as methamidophos, parathion aldicarb, carbofuran, isocarbophos and so on, if they are applied to vegetables with short growing period and continuous harvest, it is difficult to avoid human and animal poisoning caused by excessive residues.

In addition, although some pesticides have low toxicity, their production impurities or metabolites are high, such as impurities produced in the production of dithiocarbamate fungicides and their metabolites ethylthiourea are carcinogens. impurities in dicofol, carbosulfan, carbofuran and 3-hydroxy carbofuran are the main metabolites of carbofuran and carbofuran.

The internal absorption, volatility, water solubility and adsorption of pesticides directly affect their residues in plants, atmosphere, water, soil and other surrounding environment. Environmental factors such as temperature, light, rainfall, soil pH and organic matter content, vegetation / microorganisms also affect the degradation rate of pesticides and pesticide residues to some extent.

⑵ usage and Pesticide residues

Generally speaking, the dosage forms used for direct spraying, such as EC and suspending agent, are relatively harmful to crops. Because the powder is easy to disperse, it is more harmful to the environment and drug users. Any pesticide variety has its suitable control objects and crops, and has its reasonable application time, frequency, dosage and safety interval (the safe interval between the last application and harvest).

Lack of basic knowledge of the correct use of pesticides, the vast majority of farmers only use pesticides for prevention and control, the reason is very simple: good insecticidal effect, quick effect. There are also some farmers who do not pay attention to the technology of drug use (such as the front of powdery mildew, the back of downy mildew, and cannot be injected at noon on a sunny day). Once they think that the control effect is not good, they will increase the dosage, resulting in drug resistance to diseases and insect pests. When drug-resistant diseases and insect pests are harming vegetables in the field, larger doses are used to control them. In such a vicious circle, pesticide residues in vegetables will increase greatly. What is more serious is that some farmers are also in violation of regulations to use banned or restricted pesticides on vegetables. After the use of pesticides, they are busy on the market before the safe interval for the use of pesticides, so the harm to the human body is even greater.

⑶ structure error

Understanding of the use of pollution-free pesticides is not enough to affect the quality of vegetables are mainly pesticides, and in such pesticides are mainly organophosphorus pesticides, that is, three 70%: 70% of pesticides are pesticides; 70% of pesticides are organophosphorus pesticides; 70% of organophosphorus pesticides are poisonous, highly toxic and highly residual pesticides. Some farmers think that the pesticide that takes effect immediately after medicine is a good pesticide, while the low-grade, pollution-free biological pesticide has high price and slow effect, which is a waste of manpower and material resources, which also has a certain impact on the quality of vegetables.

one hundred and twenty three