Organochlorine pesticides, such as BHC and DDT, have strong stability and are not easy to decompose. Large-scale use not only directly pollutes crops, but also remains in water and soil, which enters the human body through food and is harmful to health. Organochlorine pesticides are very stable in chemical properties and are not easy to decompose in organisms. After it enters the human body through the food chain, it accumulates in the human body, and the human body cannot excrete it through metabolism. Therefore, the content of organochlorine pesticides in human body will be higher and higher, and poisoning will occur when it reaches a certain level. Organochlorine pesticides have polluted every corner of the earth because of their indecomposable stability, and even penguins in the Antarctic continent have found organochlorine pesticides.
Metal preparations are also very dangerous. Grains, fruits and vegetables sprayed with mercury preparations all contain mercury, which can directly cause food poisoning. Herbicides and fungicides are often not very toxic, but their decomposition products are very toxic, so the harm is also quite serious.
Most pesticides are toxic to people and animals, and a large number of contacts and accidental eating can lead to acute poisoning and death. According to the statistics of the World Health Organization, due to the lack of scientific knowledge and safety measures, farmers in developing countries suffer from 2 million times of pesticide poisoning every year, of which 40,000 people die, with an average of 28 people poisoned every 10 minute and 1 person killed every 17 minute! And this does not include the victims of stillbirth, carcinogenesis and abortion caused by pesticide pollution. According to the survey in 68 countries, 93% of acute poisoners are caused by pesticides such as organochlorine, organophosphorus and mercury preparations.
Chronic poisoning caused by the accumulation of a small amount of pesticides in human body can not be ignored.
Pesticide pollution has caused public hazards in many countries. Many countries have banned the use of pesticides such as DDT, dieldrin and chlorine preparations, and actively developed and produced pesticides with low toxicity and high efficiency. At the same time, they pay attention to the scientific use of pesticides, vigorously advocate biological control, protect beneficial birds and insects, and achieve "bird control insects" and "insect control insects".
Pesticides are very important to agriculture. Due to diseases, insects, weeds and other reasons, the annual loss of grain in the world accounts for about half of the total output, and the use of pesticides can save about 15% of the total output. The annual output of chemical pesticides in the world has reached millions of tons, with varieties exceeding 1000, and about 250 kinds are commonly used. The earliest pesticides used were inorganic compounds. At about 1940, organochlorine pesticides such as DDT and bhc were started to be used. Because of its low price and long-term insecticidal ability, it spread rapidly and became the most important pesticide variety. Organochlorine pesticides are cumulative and difficult to degrade. Since the 1960s, many countries began to ban or restrict the use of organophosphorus pesticides, which were gradually replaced by organophosphorus pesticides in the 1950s. However, some scholars believe that the toxicity of organochlorine pesticides is still inconclusive, and organochlorine herbicides are still used.