Toxic and Harmful Substances

In the agricultural production process, heavy metals in the soil have a great impact on the yield and quality of agricultural products. Common soil heavy metals include mercury, lead, cadmium, arsenic, etc. These heavy metals come from many sources, including the unreasonable use of agricultural fertilizers, the random discharge of industrial wastewater, and the pollution leakage in the mining process and the random accumulation of industrial waste, which will lead to heavy metal pollution in the soil of agricultural products producing areas. Heavy metals can not be biodegraded, on the contrary, they can be enriched hundreds of times under the biological amplification of the food chain, and finally enter the human body. Heavy metals interact strongly with proteins and enzymes in the human body, making them inactive, and may accumulate in certain organs of the body, causing chronic poisoning.

According to the results of many tests at present, it is found that the content of nitrate and nitrite in vegetables exceeds the standard from time to time. The reason is that excessive application of nitrogen fertilizer in vegetable production leads to imbalance of nitrogen, phosphorus and potassium nutrients, which cannot satisfy the nutrient needs of vegetable production and affect vegetable production. When applying organic fertilizer, there is also a misunderstanding that the more organic fertilizer is used, the better. Of course, organic fertilizer can improve the soil structure, increase the content of organic matter in the soil, and is conducive to the production of vegetables. However, the unreasonable application of organic fertilizer will also cause the accumulation of nitrate in vegetables, resulting in the excess of nitrate and nitrite content.

Sulfur dioxide has bleaching and antiseptic effects on food. The use of sulfur dioxide can make the product bright and white. However, eating too much food containing sulfur dioxide can easily cause breathing difficulties, vomiting, diarrhea and other symptoms, especially in asthmatic patients, which may lead to the relapse of asthma due to allergy, and in severe cases there is a fatal risk. Therefore, sulfur dioxide must be used in strict accordance with the relevant international standards for food.

Melamine is called "protein concentrate" because of its nitrogen content of up to 2/3. The daily intake of melamine in the human body exceeds the standard and can cause poisoning. The common poisoning reaction is kidney stones and kidney failure.

There are many sources of melamine contamination in agricultural products. Firstly, pesticide pollution. Cyclopropazine is a new type of low-toxic and high-efficiency insecticide. It is widely used in animal husbandry and planting industry worldwide. In the process of animal breeding, cyromazine is used to eliminate insects and kill mites, but cypromazine will be metabolized in animals to produce melamine. Small amounts of melamine is detected in eggs and milk. Secondly, chemical fertilizer pollution. Nitrogen, phosphorus and potassium are the main components for fertilizing the soil. The high nitrogen content of melamine is beneficial to increase the percentage of nitrogen fertilizer in chemical fertilizer. After melamine is absorbed by plants in chemical fertilizers, some of them will remain in the plants and affect the safety of agricultural products. Thirdly, feed contamination. Some feed producers add melamine to animal feed ingredients to increase their crude protein content. The feed from such raw materials is accompanied by melamine residues, which will accumulate in the food chain. Fourthly, the contamination of dairy products. Adding melamine to dairy products increases the protein content and shoddy. Finally, packaging materials contamination. Melamine formaldehyde resin is very common in current packaging materials. Although the chemical properties of melamine formaldehyde resin are relatively stable under normal conditions, trace amounts of melamine are released under certain conditions. These trace amounts of melamine are transferred from packaging materials to packaged foods and lead to food contamination.