(1) Polycyclic aromatic hydrocarbons Polycyclic aromatic hydrocarbons are widely distributed in coal and petroleum, among which benzopyrene (BdP) is a strong carcinogen (lung cancer), which mainly exists in coal. If tar is added to cigarettes, it can promote the occurrence of cancer, which shows that cigarettes are closely related to lung cancer. Many substances can induce the carcinogenesis of BdP, because polycyclic aromatic hydrocarbons hardly react with intracellular components. In order to react with the components in the body, it is necessary to activate hydroxylase in cells, and the activation of hydroxylase requires transition elements (such as iron and nickel).
(2)N- nitroso compound N- nitroso compound is a strong carcinogen (mainly liver cancer), which is widely distributed in human living environment. N- nitroso compounds have two precursors: ① nitrite, which exists in all agricultural products, especially in pickled products (ham, bacon, pickles). The content of nitrite in fresh vegetables stored for too long and food stewed for too long increased obviously. ② Secondary amine is an intermediate product of protein metabolism in animals and plants. It is rich in marine fish and canned fish.
Nitrite not only has a strong carcinogenic effect, but also can make hemoglobin lose its ability to transport oxygen, causing different degrees of hypoxia symptoms.
The hygienic standard of nitrite in grain is 3 mg/kg, leafy vegetables are 1200 mg/kg, melons and fruits are 600 mg/kg, freshwater fish and meat are 3 mg/kg, and drinking water (calculated by nitrogen) is 20 mg/L.
(3) Haloalkanes, such as chloroform and carbon tetrachloride, have strong damage and carcinogenic effects on the liver. During the disinfection of liquid chlorine in waterworks, volatile halogenated organic compounds such as trihalomethane, dibromomethyl chloride and tribromomethane (THMS) and non-volatile halogenated organic compounds such as halogenated acetonitrile, halogenated acetic acid, halogenated acid, halogenated ketone and halogenated aldehyde are often produced. When boiling water, it should be boiled for a period of time to volatilize volatile halogenated organic compounds, so as to reduce the content of chlorine secondary metabolites in water.
(4) Pesticide pesticide pollution pesticides include organochlorine pesticides, organophosphorus pesticides, organomercury pesticides, carbamate pesticides, herbicides, etc. Organochlorine pesticides, including HCH and DDT, are fat-soluble pesticides with long half-life and high toxicity. The State Council stopped using them on 1982. According to the investigation of 16 provinces in China in 2000, the detection rates of bhc and DDT in 19 14 batches of grain were 100% and 49.8% respectively, both exceeding the national hygiene standards. Organophosphorus pesticides, including parathion, malathion, ethion, parathion, trisodium sulfate, etc. , easy to decompose, not easy to cause chronic poisoning, but it has strong acute toxicity, which can make people nervous dysfunction, drowsiness and language disorder. Organomercury pesticides include Xilisheng (ethyl mercuric chloride) and Xilisan (phenyl mercuric acetate). This is a highly toxic pesticide, which can destroy the main enzyme system in human body, and its half-life in soil is as long as 10 ~ 30 years. Carbamate pesticides, such as carbaryl, are easy to decompose and less toxic to animals, but they can synthesize ammonium nitrite with nitrite in vivo, which has carcinogenic effect. Herbicides are usually mutagenic, teratogenic and carcinogenic.
Hygienic standard for pesticides in grain: parathion 0. 1mg/kg (grain), methamidophos 0. 1mg/kg (grain), phoxim 0.05mg/kg (corn), dichlorvos 0. 1mg/kg (grain) and dimethoate 0. Hygienic standard for vegetables: malathion and parathion can not be detected, phoxim 0.05 mg/kg, acephate 0.2 mg/kg, dichlorvos 0.2 mg/kg, dimethoate 1.0 mg/kg.