1? Microbial pollution in food and human health is 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 cooked or heated before eating; Eating contaminated food can also cause infectious diseases such as anthrax, tuberculosis and brucellosis (wave fever); Others such as Vibrio cholerae, Escherichia coli, Shigella dysenteriae, hemolytic streptococcus, foot-and-mouth disease virus, avian influenza virus, hepatitis A virus, etc. , thus causing corresponding diseases. 1988 the outbreak of hepatitis a in Shanghai is a typical example. In addition, some bacteria also contain enzymes that can decompose various organic substances, and they grow and reproduce in large quantities under suitable conditions. After food is polluted by these bacteria, protein, fat and sugar in it will be decomposed under the action of various enzymes, which will make the sensory properties of food worse, reduce the nutritional value and even deteriorate.
If food is contaminated by parasites or parasite eggs, people can cause corresponding parasitic diseases after eating it, such as taeniasis, cerebral cysticercosis, cerebral echinococcosis, clonorchiasis (also known as liver fluke disease), ascariasis and so on. 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.
Fungi are widely distributed in nature. Fungal contaminated crops, air, soil and containers can pollute food. Under suitable conditions, some fungal strains can produce toxic metabolites, namely mycotoxins, which are very toxic to people and animals. Eating a large amount of food contaminated by fungi and their toxins at one time will cause food poisoning; Long-term intake of small amounts of contaminated food can also lead to chronic diseases or cancer. For example, aflatoxin not only has strong hepatotoxicity, leading to acute and chronic hepatotoxicity and even death, but also has strong carcinogenicity, which can cause cancers such as liver cancer, gastric cancer, renal cancer, colon cancer and breast cancer. Aflatoxin is an active substance produced by Aspergillus flavus. Aspergillus flavus is a fungus, which is ubiquitous in air and soil. It is easy to grow under aerobic, high temperature and humid conditions, and easy to grow mildew on agricultural products such as peanuts, corn, rice, wheat, barley, cottonseed and soybeans. Aflatoxin contamination of food raw materials and finished products is very common, and the contamination rate of aflatoxin in food in South China, India, the United States and some Southeast Asian countries is relatively high. The acute toxicity of aflatoxin mainly causes liver injury, hepatocyte degeneration, fat infiltration and bile duct hyperplasia. Aflatoxin not only causes liver cancer in poultry, fish, livestock and other animals, but also has a high incidence of human liver cancer in areas where grain, oil and food are seriously polluted by aflatoxin. The International Institute of Cancer has identified aflatoxin as a first-class human carcinogen.
After eating food seriously contaminated by aflatoxin, symptoms such as fever, abdominal pain, vomiting and loss of appetite may occur. In severe cases, toxic liver diseases such as hepatosplenomegaly, pain in liver area, yellow staining of skin and mucosa, ascites, edema of lower limbs, abnormal liver function, and symptoms such as enlargement of heart, pulmonary edema, even spasm and coma may occur within 2-3 weeks.
As early as BC 1 century, it was recorded that eating moldy grains would cause some diseases, leading to abortion and teratogenesis in pregnant women. Moldy feed will slow down the growth of livestock, leading to deformity or death. In 1960s, 65,438+10,000 turkeys on a farm in England died within a few months after eating moldy peanut powder. Researchers have found that some mycotoxins are not only highly toxic, but also important carcinogens.
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 cheese fly larvae in salted fish. Foods with high sugar content such as dates, chestnuts, biscuits and snacks are particularly vulnerable. Insect pollution will destroy a lot of food, and eating these food contaminated by insects may also cause harm to human health.
2? Chemical fertilizer pollution in food and human health in agricultural production, in recent years, a large number of long-term indiscriminate application of chemical fertilizers has caused agricultural environmental pollution, which in turn has brought pollution to food. In vegetable planting, excessive application of nitrogen fertilizer, coupled with the fact that vegetables are plant foods rich in nitrate, has the greatest influence on nitrate content in leafy vegetables. About 80%-90% of nitrate ingested by human beings comes from vegetables. Although nitrate in vegetables is harmless to human body, it is easy to be reduced to nitrite, which leads to cancer. 1993, the World Health Organization and the Food and Agriculture Organization of the United Nations stipulated that the daily allowable intake of nitrate was 0? 36 mg/kg (body weight), and the daily allowable intake of nitrite is 0? 13mg/kg (weight). A certain determination result shows that the nitrate content of some vegetables (leafy vegetables) has exceeded the standard, and the nitrite content of most vegetables has not exceeded the standard, but the mustard tuber obviously exceeds the standard, which poses a potential threat to human health and should be paid great attention to.
The main effects of vegetables contaminated with nitrate on human body are as follows: first, high nitrate content may cause methemoglobinemia; Second, nitrate and nitrite are precursors of strong carcinogens, which can induce digestive system cancer.
3? Pesticide pollution in food and human health Organochlorine pesticides have been used in China for more than 30 years. Although 1983 stopped the production of organochlorine pesticides, its residue problem can not be ignored. For example, the residue period of DDT and HCH is as long as 50 years. Organochlorine pesticides have low volatility, strong fat solubility and stable chemical properties, and are easy to accumulate in fat-rich tissues of animals and plants and fat-rich parts of grain shells.
Long-term intake of food containing organochlorine pesticides mainly causes acute and chronic poisoning, which infringes on the liver, kidney and nervous system. In addition, pesticides also have the function of environmental hormones, which will also cause certain damage to endocrine and reproductive systems.
In a county with high incidence of liver disease, the residual amount of DDT and BHC in body fat of tumor patients is higher than that of healthy people. Some people abroad have warned that even if DDT and BHC are stopped immediately, the accumulated amount of human body fat will not change within 10-20 years.
Since China stopped using organochlorine pesticides, organophosphorus pesticides have become the most important category of pesticides, especially vegetables, fruits and tea. According to a survey in a city, dimethoate, DDV, methamidophos and malathion are widely used in vegetables, and it is difficult for these pesticides to enter the market within a safe interval after use.
Regular intake of a small amount of organophosphorus pesticides can cause mental disorders and chronic neuritis, have adverse effects on visual function, reproductive function and immune function, and also have carcinogenic, teratogenic and mutagenic hazards.
4? Heavy metal and nonmetal pollution in food is harmful to human health. The main source of metal and nonmetal pollution in food is the waste water, waste gas and waste residue (referred to as "three wastes") discharged without treatment, which pollutes water and soil, and then pollutes cultured edible animals. This is an important cause of harmful metal and nonmetal pollution in food. The "three wastes" discharged without treatment contain a lot of mercury, cadmium, arsenic, lead, nickel, antimony, tin, cobalt, chromium, fluorine and selenium, which can seriously pollute water sources and soil. Through irrigation, aquaculture and aquaculture, harmful pollutants are absorbed and enriched by animals and plants and enter the food chain, seriously polluting aquatic products such as fish and shrimp and agricultural and sideline products such as grain.
Mercury pollution: According to the survey, the detection rate of mercury in fish in major river systems in Jiangsu Province reached 100%. More than 95% mercury in fish is highly toxic methylmercury, which is harmful to human body. It not only damages the central nervous system and causes a series of neurological and mental symptoms, but also is hereditary and prone to teratogenesis.
In Minamata, Japan, 6% of "Minamata disease" is congenital. These children are characterized by developmental retardation, mental retardation, deformity, and some died of paralysis. The detection rate of mercury in grain, vegetables, fruits and vegetables irrigated by "three wastes" wastewater is also very high, and some contents have exceeded the national standard.
Cadmium pollution: the content of cadmium is quite low in the general environment, but it can reach a quite high concentration after being enriched in the food chain. Because industrial wastewater containing cadmium is discharged into water, aquatic organisms can enrich cadmium from water. Its concentration in the body is about 4500 times higher than that in water. Food is the main source of cadmium intake, and only a small part of cadmium intake by human body is excreted. Cadmium that enters the body with food is absorbed into the blood through the digestive system, and most of the cadmium in the blood enters the kidney and liver, and accumulates in the body, causing damage to renal proximal tubule epithelial cells, resulting in clinical hypercalciuria, proteinuria, glycosuria, amino acid urine, etc., which eventually leads to negative calcium balance and osteoporosis.
5? Organic and inorganic pollution in food and human health The types of organic and inorganic pollutants in food are complex, and the ways of pollution are also varied. Their main sources are: environmental pollutants such as industrial "three wastes" discharge lead to food production process pollution; Pollution in food processing; Pollution of packaging materials such as food containers.
Polycyclic aromatic hydrocarbons (PAHs) are a kind of chemical carcinogens with large quantity, complex species, wide distribution, close relationship with human beings and great threat to human health. Polycyclic aromatic hydrocarbons mainly come from incomplete combustion of coal, diesel, gasoline, crude oil, cigarettes and other organic substances. Benzopyrene is the main carcinogenic pollutant in polycyclic aromatic hydrocarbons contaminated food. Benzopyrene can be detected in fresh meat, bacon, fried and baked food, various vegetables, fruits, grains, seafood, vegetable oil and alcohol, especially in fried, barbecue and smoked food, carcinogens will increase greatly. The main harm of polycyclic aromatic hydrocarbons to human body may be carcinogenesis.
Epidemiologists have done a lot of research to predict the cancer risk of polycyclic aromatic hydrocarbons in food. The incidence of gastric cancer in western Hungary is obviously high, which is related to the fact that residents in this area often eat homemade bacon with high benzopyrene content. The former Soviet Union reported that the incidence of gastric cancer in a coastal area of Latvia was obviously high, which was thought to be caused by eating more smoked fish.
Nitrosamines are also recognized as one of carcinogenic pollutants, which can act on all important organs of animals, but the liver and esophagus are the most sensitive. Because the precursors of nitrosamines, secondary amine and nitrite, are widely distributed in nature and can be produced in animals and humans, nitrosamines are also harmful substances in food. The pollution of nitrosamines and benzopyrene to food is related to processing methods. For example, the nitrosamine of raw carp is 4 μ g/kg, which is increased to 9 μ g/kg after smoking. If it is dyed with nitrate and smoked, it can be increased to 14-26 μ g/kg.
Vinyl chloride and a? Phenyl R- aminonaphthalene and dioctyl phthalate are harmful substances in food packaging and container materials. Vinyl chloride is a monomer of plastic products, which is carcinogenic. Plasticizer (dioctyl phthalate) and stabilizer added in vinyl chloride have certain toxicity, and may dissolve and migrate into food when they contact with water, oil, alcohol, acid and alkali. If plastic products containing vinyl chloride are used as food packaging, it will lead to food pollution; Fish may die if they are raised in fresh water or seawater in PVC containers containing plasticizers. According to experiments, dioctyl phthalate can cause leukocytosis, anemia, hematuria and death of fiber cells in the central nervous system.
Another example is porcelain-like tableware, also called melamine tableware, which is a new type of tableware and is widely used in restaurants and families. According to Zhongxin. com. Com April, 2009 12 Recently, during the inspection of porcelain-like tableware in Beijing, Hebei and other places, it was found that some enterprises had quality problems such as formaldehyde exceeding the standard. In-depth investigation found that some enterprises are actually producing porcelain-like tableware with banned raw material urea-formaldehyde resin. Urea-formaldehyde resin is easy to decompose formaldehyde at high temperature, and formaldehyde is recognized as a carcinogen. Using such tableware to hold food will inevitably cause food pollution.