Toxicity of harmful metals to food

作者：admin  点击次数：17  发布时间：2025-04-15

(I) The pathways of harmful metal contamination of food, characteristics of toxic effects and control measures
More than 80 kinds of metal elements in the environment can enter the human body through food and drinking water, respiratory inhalation and skin contact. Some of these metal elements can have obvious toxic effects on the human body at low intake levels, such as lead, cadmium, mercury, etc., which are often called toxic metals. In addition, many other metal elements, even some essential elements, such as chromium, manganese, zinc, copper, etc., can also have greater toxic effects or potential harm to the human body if they are taken in excessive amounts.
1. The pathways of harmful metal contamination of food
The harmful metals in food mainly come from the following aspects:
(1) High background content in special natural environments in certain regions Due to the heterogeneity of element distribution in the environment of different regions, the background values ​​of certain metal elements in certain regions may be relatively higher or significantly higher than those in other regions, resulting in higher content of harmful metal elements in animal and plant foods produced in these regions.
(2) Food contamination caused by toxic and harmful metal elements due to man-made environmental pollution. With the development of industrial and agricultural production, the number of chemicals used, including those containing toxic and harmful metal elements, is increasing, and the pollution to the environment is becoming more and more serious, which can cause direct or indirect pollution to food.
(3) Food contamination caused by toxic and harmful metal elements contained in machinery, pipes, containers and additives used or contacted during food processing, storage, transportation and sales.
2. Toxic characteristics of harmful metal pollution in food
Intake of food contaminated by harmful metal elements can cause multiple hazards to the human body, and its hazards usually have the following common
characteristics. (1) Strong cumulative toxicity, slow excretion after entering the human body, and long biological half-life. (2) It can reach very high concentrations in organisms and the human body through biological enrichment in the food chain. For example, the content of metal poisons such as mercury and cadmium in aquatic products such as fish and shrimp may be hundreds or even thousands of times higher than the concentration in their living environment. (3) The harm caused by toxic and harmful metal contaminated food to the human body is often mainly chronic poisoning and long-term effects (such as carcinogenicity, teratogenicity, and mutagenicity). Since the amount of toxic and harmful metal contamination in food is usually small, it often leads to chronic poisoning of a large number of people and long-term or potential harm to health that is not easy to detect in time. However, it can also cause acute poisoning due to accidental pollution or intentional poisoning.
3. Factors affecting the intensity of toxic and harmful metal toxicity
(1) The existence form of metal elements Metals in organic form and metal salts with high water solubility are usually more toxic because they are more absorbed by the digestive tract. For example, the digestive tract absorption rate of mercuric chloride is only about 2%, while the absorption rate of methylmercury can reach more than 90% (but there are exceptions, such as the toxicity of organic arsenic is lower than that of inorganic arsenic). Chloride and cadmium nitrate are more toxic because they are more soluble in water than cadmium sulfide and cadmium carbonate.
(2) The health and nutritional status of the body and the content and balance of certain nutrients in food, especially the nutritional level of protein and certain vitamins (such as vitamin C), have a great impact on the absorption and toxicity of metal poisons. (3) Interactions between metal elements or between metal and non-metal elements. For example, iron can antagonize the toxic effects of lead because iron competes with lead for intestinal mucosal carrier proteins and other related absorption and transport carriers, thereby reducing the absorption of lead; zinc can antagonize the toxic effects of cadmium because zinc can compete with cadmium for zinc-containing metal enzymes. On the other hand, some toxic and harmful metal elements can also produce synergistic effects. For example, the synergistic effect of arsenic and can cause severe inhibition of sulfhydryl enzymes and increase their toxicity; mercury and lead can act together on the nervous system, thereby aggravating their toxic effects. 4. General measures to prevent metal poisons from contaminating food and their harm to the human body (1) Eliminate pollution sources. This is the main measure to reduce the contamination of food by toxic and harmful metal elements. For example, control the discharge of industrial waste, strengthen sewage treatment and water quality inspection, prohibit pesticides and inferior food additives containing mercury, arsenic and lead, and make necessary treatments on the surfaces of metal and ceramic pipes and containers. Develop and promote the use of non-toxic or low-toxic food packaging materials. (2) Formulate the maximum allowable limit standards for toxic and harmful metals in various types of food, and strengthen regular supervision and inspection work. (3) Toxic and harmful metals and their compounds should be properly stored to prevent accidental ingestion, misuse, and accidental or intentional contamination of food.