Food pollution can be divided into biological pollution, chemical pollution and radioactive pollution.
Biological pollution: mainly caused by harmful microorganisms and their toxins, parasites and their eggs and insects. Animal foods such as meat, fish, eggs and milk are easily contaminated by pathogenic bacteria and their toxins, leading to bacterial food poisoning and infectious diseases in humans and animals. Pathogens mainly come from patients, carriers, sick animals and sick birds. Pathogens and their toxins can contaminate food through air, soil, water, utensils, patients' hands or excreta. Food contaminated by pathogenic bacteria and their toxins, especially animal food, will cause bacterial food poisoning such as salmonella or staphylococcus aureus toxin if it is not heated before eating. Eating contaminated food can also cause anthrax, tuberculosis, brucellosis (wave fever) and other infectious diseases.
Mold is widely distributed in nature. Crops, air, soil and containers contaminated by mold will pollute food. Under suitable conditions, some mold strains can produce toxic metabolites, namely mycotoxin (see the impact of mold pollution on health). Such as aflatoxin and trichosporin, are very toxic to humans and animals. Eating a large amount of food contaminated by mold and its toxins at one time will cause food poisoning; Long-term intake of a small amount of contaminated food can also lead to chronic diseases or cancer. Some mycotoxins can also be transferred from animals or human bodies to milk, damaging the health of milk drinkers.
Microorganisms contain enzymes that can decompose various organic substances. After these microorganisms pollute food, they grow and multiply in large numbers under suitable conditions. Protein, fat and sugar in food will be decomposed under the action of various enzymes, which will make the sensory characteristics of food worse, reduce the nutritional value and even deteriorate.
Parasites that pollute food mainly include tapeworms, Trichinella spiralis, Clonorchis sinensis and Ascaris. The pollution sources are mainly patients, sick animals and aquatic organisms. Pollutants generally pollute water or soil through the feces of patients or sick animals, and then infect or pollute livestock, fish and vegetables.
Poor storage conditions of grain and various foods are easy to breed various storage pests. Such as beetles, moths and mites in grains; Fly maggots in fish, meat, sauce or pickles and dry fly larvae in salted fish. Foods with high sugar content such as dates, chestnuts, biscuits and snacks are particularly vulnerable. Insect pollution can destroy a lot of food, but it has not been found that food contaminated by insects causes significant harm to human health.
Chemical pollution: mainly refers to the pollution of pesticides, food additives, food packaging containers and industrial wastes, as well as the pollution caused by organic or inorganic compounds such as mercury, cadmium, lead, arsenic, cyanide, organophosphorus, organochlorine, nitrite and nitrosamine. The causes of chemical pollution are: ① the extensive use and improper use of pesticides. ② Use food additives that do not meet the hygiene requirements. (3) The use of substandard packaging containers may cause soluble harmful substances on the containers to enter food when contacting with food, such as lead in ceramics and vinyl chloride monomer in PVC plastics, which may be transferred to food. For another example, the wax on the packaging wax paper may contain benzo (a) pyrene, and the colored ink and printing paper may contain polychlorinated biphenyls (PCBs), which are particularly easy to dissolve in foods rich in oil. (4) Environmental pollution caused by unreasonable industrial emissions will also endanger human health through the food chain.
Radioactive pollution: radioactive substances in food are radioactive substances from the earth's crust, which is called natural background; There are also radioactive substances produced by nuclear weapons testing or peaceful use of radioactive energy, that is, man-made radioactive pollution (see the impact of radioactive pollution on health). Some fish can enrich metal isotopes, such as 137 cesium and 90 strontium. The latter has a long half-life, mostly concentrated in bone tissue, and is not easy to be excreted, which has a certain impact on the hematopoietic organs of the body. Some marine animals such as molluscs can enrich 90 Sr, oysters can enrich 65 Zn and some fish can enrich 55 Fe.
The harm to human health has many manifestations. A large number of contaminated food can cause acute poisoning, that is, food poisoning, such as bacterial food poisoning, pesticide food poisoning, mycotoxin poisoning and so on. Long-term (generally refers to six months to more than one year) intake of a small amount of food containing pollutants can cause chronic poisoning. The cause of chronic poisoning is difficult to trace, and its influence is extensive, so special attention should be paid to it. For example, a few months after ingesting the grain with residual organic mercury pesticides, there will be symptoms such as general fatigue and increased urine mercury content; Long-term intake of trace aflatoxin contaminated food can cause degeneration, necrosis, fat infiltration and proliferation of bile duct epithelial cells, and even cancer. Chronic poisoning can also be manifested as reproductive dysfunction such as growth retardation, infertility, abortion and stillbirth, and some can also cause fetal malformation through the mother. Known food-related teratogenic substances include phenylmercuric acetate, methylmercury, tetrachlorodiphenyl dioxins, dieldrin, aldrin, DDT, chlordane, heptachlor and dichlorvos.
Some food pollutants also have mutagenic effects. Mutations, such as those in germ cells, can lead to obstacles to normal pregnancy, even infertility, fetal malformation or premature death. Mutation, if it occurs in somatic cells, will cause abnormal proliferation of cells that no longer proliferate under normal circumstances, thus forming the basis of canceration. Food-related mutagens include benzo (a) pyrene, aflatoxin, DDT, dieldrin and alkyl mercury compounds.
Some food pollutants can induce cancer. For example, feeding mice moldy corn or peanuts containing aflatoxin B 1 can induce liver cancer. Carcinogens related to food include polycyclic aromatic hydrocarbons, aromatic amines, chlorinated hydrocarbons, nitrosamines, inorganic salts (some arsenic compounds, etc. ), aflatoxin B 1 and biological alkylating agent (such as epoxide in highly oxidized oil).
Preventive measures Comprehensive measures must be taken to prevent food pollution, mainly including: ① formulating, promulgating and implementing food hygiene standards and hygiene regulations. Formulate hygiene requirements and standards for food containers and packaging materials. Formulate hygienic regulations for food transportation to ensure that food is not polluted and spoiled by water during transportation. ② Strengthen epidemic prevention and quarantine of livestock and poultry and meat inspection. (3) Formulate processing management regulations, prevent pollution and mildew, and implement relevant health standards. Formulate and implement measures and regulations for the safe use of pesticides, and provide more pesticides with high efficiency, low toxicity and low residue to replace pesticides with high toxicity and high residue (organochlorine, organomercury, etc.). (4) Strengthen the treatment of industrial waste. ⑤ Strengthen food inspection and food hygiene supervision.