Chemical contamination of food and its prevention

作者：admin  点击次数：22  发布时间：2025-04-10

There are many types of chemical pollution in food, the most common and important ones are pesticides, toxic metals, N-nitroso compounds, polycyclic aromatic hydrocarbons, heterocyclic amines, dioxins, and pollution from food containers and packaging materials.
Pesticides and veterinary drugs pollution to food and its prevention
(I) Overview
1. Pesticides and pesticide residues
According to the definition of my country's "Regulations on Pesticide Management", pesticides refer to chemical synthesis or mixtures of one or several substances derived from biological or other natural substances and their preparations used to prevent, eliminate or control diseases, insects, weeds and other harmful organisms that endanger agriculture and forestry, as well as to purposefully regulate the growth of plants and insects.
The pollution caused to the environment and food by the use of pesticides (including pollution of pesticides and their toxic derivatives) is called environmental pesticide residues or food pesticide residues (pesticide residues). According to the purpose, pesticides can be divided into types such as insecticides, fungicides, herbicides, nematicides, insecticides, rodenticides, defoliants and plant growth regulators. Among them, the most commonly used are insecticides, fungicides and herbicides. According to the chemical composition and structure, pesticides can be divided into organophosphorus, carbamate, pyrethroid, organochlorine, organoarsenic, organomercury and other types. At present, there are more than 1,000 kinds of pesticide raw materials used in the world. There are nearly 200 kinds of raw materials and more than 1,000 kinds of preparations used in my country.
2. Veterinary drugs and veterinary drug residues
Veterinary drugs refer to substances (including drug feed additives) used to prevent, treat, diagnose animal diseases or purposefully regulate animal physiological functions, mainly including serum products, vaccines, diagnostic products, microecological products, Chinese medicinal materials, Chinese patent medicines, chemical drugs, antibiotics, biochemical drugs, radioactive drugs and external insecticides, disinfectants, etc. (Veterinary Drug Management Regulations, 2004). Veterinary drug residues (abbreviated as veterinary residues) refer to the parent compounds and (or) their metabolites of veterinary drugs contained in any edible part of animal products, as well as the residues of veterinary drug-related impurities. Veterinary drug residues include both the original drug and the metabolites of the drug in the animal body. The main veterinary drug residues include seven categories:
D antibiotics;
② anthelmintics;
③ growth promoters;
④ antiprotozoal drugs;
⑤ trypanocide drugs;
⑥ sedatives;
⑦ B-adrenergic receptor blockers.
3. Advantages and disadvantages of using pesticides and veterinary drugs
Reducing crop losses, increasing yields, improving the economic benefits of agricultural production and increasing food supply are the greatest benefits of using pesticides. It is estimated that the loss of crops due to diseases, insects and weeds during the growth period is 30%~35%, and the loss after harvest is 10%~20%. If pesticides are used properly, the amount of loss can be greatly reduced. In addition, pesticides are used in forestry, animal husbandry, fisheries, public health and disease control, and have played a good role in improving greening efficiency, increasing production, reducing the occurrence of insect-borne infectious diseases, and improving the living environment of humans.
On the other hand, due to the large-scale and widespread use of pesticides, they can not only cause multiple harms to the human body through food and water intake, air inhalation and skin contact, such as acute and chronic poisoning and carcinogenic, teratogenic and mutagenic effects, but also cause serious pollution to the environment, deteriorate environmental quality, reduce species, and destroy ecological balance. Therefore, the use of pesticides and veterinary drugs should be reduced as much as possible. In terms of controlling crop diseases and insect pests, one is to develop high-efficiency, low-toxic and low-residue pesticides; the other is to carry out comprehensive prevention and control, such as increasing the use of biological pesticides (microorganisms, plants, antibiotics, hormones, etc.), cultivating crop varieties resistant to diseases and insect pests, cultivating and utilizing insect natural enemies, and improving crop cultivation technology. (II) Sources of pesticide and veterinary drug residues in food
Pesticides that enter the environment can contaminate food through various channels. It is estimated that about 90% of pesticides that enter the human body are ingested through food. The main sources of pesticide residues in food are as follows.
1. Direct pollution of crops by pesticide application includes surface adhesion pollution and systemic pollution. Factors affecting the degree of pollution should be considered from the following aspects: (1) Pesticide properties Systemic pesticides (such as systemic phosphorus and parathion) have more residues, while penetrating pesticides (such as fenitrothion) and contact pesticides (such as pyrethroids) have less residues and mainly remain on the surface of crops (i.e. surface adhesion pollution). Stable varieties (such as organochlorine, heavy metal preparations, etc.) have longer residual time than easily degradable varieties (such as organophosphate).
(2) Dosage form and application method Oil preparations are more likely to have residues than powder preparations, and spraying with alcohol has higher residues than mixing with soil. Applying pesticides in irrigation water will cause greater pollution to the root base of plants.
(3) Application concentration, time and frequency The higher the concentration, the more frequent the application, and the shorter the interval from harvest, the higher the residue.
(4) Meteorological conditions Temperature, rainfall, wind speed, sunshine, etc. can all affect the removal and degradation of pesticides.
(5) Crop varieties, growth and development stages, and edible parts.
2. Crops absorb pesticides from polluted environments
Crops can absorb pesticides from polluted environments for a long time, especially from soil and irrigation water. The amount absorbed is related to the plant species, root conditions, edible parts, pesticide dosage, application method and usage, as well as soil type, structure, pH, organic matter and microbial types and content.
3. Food contamination through the food chain
For example, feed contaminated with pesticides leads to contamination of meat, milk, and eggs; industrial wastewater containing pesticides pollutes rivers, lakes, and seas and then pollutes aquatic products. Some relatively stable pesticides, pesticides that have a high affinity for special tissues and organs, or pesticides that can be stored in adipose tissue for a long time (such as organic gases, organic mercury, organic tin, etc.) can be concentrated step by step through the action of the food chain, which is called bioconcentration.
4. Pollution from other sources
(1) Pollution of grain caused by the use of fumigants in grain depots
(2) Pollution of animal food caused by the application of pesticides in livestock and poultry breeding sites and on livestock and poultry;
(3) Pollution during grain storage, processing, transportation and sales, such as mixed loading, mixed storage, container and vehicle pollution, etc.;
(4) Accidental pollution, such as mistakenly eating seeds mixed with pesticides as grain, mistakenly adding pesticides to or mixing them into food, using the wrong variety or dosage when applying, resulting in high pesticide residues, etc.