The application of human and animal manure as fertilizer causes soil pollution, mainly due to inadequate treatment, in which parasites, germs and viruses are brought into the soil, which can affect crop growth and human health. In addition, the corpses of animals and people, especially those buried directly after death, will make the bacteria in the corpses pollute the soil. Parasites, germs and viruses in polluted soil can attach to vegetables and eat into human body, and people can also get sick through contact with polluted soil. Studies have shown that pathogenic microorganisms can survive in soil for a long time, such as Vibrio cholerae for 8-60 days, Shigella dysenteriae for 22- 142 days, Salmonella for 70 days, and parasitic eggs can survive in soil for longer, such as ascaris eggs for more than 2 years.
Pesticides pollute the soil mostly because of long-term residues in the soil. For example, it takes several years to decades for organochlorine pesticides to degrade in soil, and it can be enriched in crops, which can affect crops and human body for a long time. Crops absorb pesticides from soil, accumulate in roots, stems, leaves, fruits and seeds, and endanger human and animal health through food and feed. Organophosphorus pesticides and organochlorine pesticides can cause acute and chronic poisoning. Organophosphorus pesticide is a neurotoxic agent, which can inhibit cholinesterase in the body, cause acetylcholine aggregation and lead to neurological dysfunction. Symptoms of acute poisoning include nausea, vomiting, dyspnea, pupil contraction, muscle spasm and unconsciousness. The main symptoms of chronic poisoning are headache, dizziness, fatigue, loss of appetite, nausea, shortness of breath, chest tightness and so on. Chronic poisoning of organochlorine pesticides is similar to organophosphorus pesticide poisoning, with symptoms such as low back pain, hepatomegaly and abnormal liver function. In addition, organochlorine pesticides will also have a wide impact on the endocrine system, immune function and reproductive function of humans and animals. Animal experiments show that it has mutagenic, teratogenic and carcinogenic effects.
The harm of heavy metal pollution in soil to health is mainly through the enrichment of crops and the pollution of grain. Through the role of the food chain, people eat contaminated food and vegetables, which affects their health. The soil is easy to enrich crops, and the metal pollutants that do great harm to health are cadmium (Cd), mercury (Hg), chromium (Cr), lead (Pb) and so on. Heavy metals in crops are mainly absorbed from polluted soil through roots. The aforementioned 1955 "painful disease" incident in Japan is a typical public disease of cadmium poisoning caused by cadmium (Cd) polluting river water, irrigating crops with polluted river water and people eating contaminated food. Lead is toxic to the nervous system. Long-term consumption of food with high lead content will lead to anemia, nervous system damage, mental retardation and kidney damage. Chromium (Cr) is toxic, corrosive to skin and mucosa, and has carcinogenic and teratogenic effects. Mercury is toxic to the liver, kidneys and nerves. Arsenic (As) is highly toxic, carcinogenic and teratogenic.
Heavy metal pollution in soil makes the quality of agricultural and sideline products decline continuously, and the content of heavy metals in food such as grain, vegetables and fruits in many places exceeds the standard or approaches the critical value. Some polluted farmland produces "cadmium rice", and some vegetables in polluted irrigation areas have unpleasant smells. Soil pollution is enriched into human and animals through the food chain, which endangers health and causes diseases. According to the investigation, the cadmium concentration in rice in a mining area in Guangxi seriously exceeded the standard due to sewage irrigation, and the local residents have been eating this kind of cadmium rice for a long time, which has reached the third stage of "pain". In some areas, many people suffer from various diseases because of drinking sewage for a long time.
In addition, heavy metals in soil can also flow into rivers with rainwater to pollute river water, and immerse underground with rainwater to pollute groundwater, thus affecting human health through drinking water. Heavy metals in soil can also float in the air with dust to pollute the air, and enter the human body with the air to affect human health.
Long-term use of chemical fertilizers, especially nitrogen fertilizers, will increase the nitrate content in vegetables, such as Chinese cabbage, spinach, celery and green vegetables. Vegetables containing nitrate will be converted into nitrite under processing conditions, while nitrite will be converted into nitrite under anoxic conditions, and nitrite can synthesize nitrosamines under acidic conditions. It has been proved that nitrosamines can cause tumors in organs such as liver, esophagus and stomach. It can also induce tumors in brain, large intestine, skin, kidney, larynx, lung, nasal cavity, pancreas, bladder, hematopoietic organs and lymph.
In short, the impact of soil pollution on health is like an invisible killer, which is hidden and lagging behind. Although it has no obvious impact on health like air pollution and water pollution, it quietly and slowly poisons our bodies. In many modern diseases, especially cancer, we can find the shadow of soil pollution. Therefore, caring for our land, reducing the use of chemical fertilizers, reducing the use of pesticides, not littering, caring for the environment, caring for our air and caring for our water resources means caring for our health and ourselves.