In the season when flowers are in full bloom, the pollen of various flowers is scattered in the air, most of which are so tiny that we need a magnifying glass or even a microscope to see them. These pollen grains float around in the air, floating on the stamens of flowers of similar plants and combining with them to complete the task of bearing children and reproducing the next generation. However, some pollen has drifted into people's respiratory tract, causing some people to induce asthma due to allergies. Of course, this cannot be called air pollution, nor can it be called biological pollution of the air. At best, it can only be regarded as natural pollution, just as volcanic ash erupted from a volcano causes serious pollution of particulate matter in the air. This is a natural (disaster) phenomenon. But at least it shows that some life forms in nature may also endanger our human health. Such as pathogenic bacteria, some pathogenic microorganisms and insects in air, water, soil and food, may endanger our health.
Most microorganisms in the atmosphere are attached to dust particles and dispersed with the wind. Therefore, the increase of dust in the air often means the increase of microorganisms. Generally speaking, there are more microorganisms in urban air than in rural areas, more streets with frequent traffic than green belts, and more air near the ground than in the upper atmosphere. Of course, this is also related to factors such as season, climate and population density. Most microorganisms in the air are non-pathogenic and only a few are pathogenic. Due to the lack of sufficient moisture and nutrients in the air for the growth of bacteria and microorganisms, especially pathogenic bacteria and microorganisms are easy to die under the conditions of sunlight (ultraviolet rays), dryness and rapid dilution of the atmosphere. Therefore, under outdoor conditions, it is generally not easy to spread respiratory infectious diseases. But it is different indoors, especially in public places with poor ventilation and crowded people, where there are more dust, pathogenic bacteria and microorganisms, which are easy to cause the spread of diseases.
How do pathogenic microorganisms and bacteria in the air enter the human body to spread diseases? One is attached to dust and inhaled into human body; Second, it adheres to the droplets ejected from the nasal cavity and mouth, some of which may be directly inhaled into the human body, some of which will die after losing moisture and drying, and some of which will continue to breed in wet places, and then fly up and be inhaled into the human body. Airborne viral respiratory infectious diseases can cause epidemics, such as influenza, mumps, measles, chickenpox, rubella and viral pneumonia. Bacterial infectious diseases include tuberculosis, epidemic cerebrospinal meningitis, scarlet fever, diphtheria and whooping cough. In addition, the excreta of some patients or carriers, such as sputum, purulent blood, feces and surgical dressings (gauze, bandages, etc. ), which may contain staphylococcus aureus or hemolytic streptococcus. After drying, these excrement will become dust with bacteria, which will fly up due to indoor cleaning, personnel activities and air flow, causing air pollution. This polluted air often causes some patients' body surface trauma, burns and so on. Infection causes symptoms such as suppuration and fever, which further worsens the condition.
Therefore, public places and bedrooms should maintain good ventilation and environmental sanitation, and individuals should develop good hygiene habits and avoid spitting.
Biological pollution of water is much more complicated than air pollution. Water is a natural environment where microorganisms are widely distributed. Both surface water and groundwater, even rain and snow water, contain bacteria, viruses, fungi, algae, leptospira, protozoa and other microorganisms. The vast majority of microorganisms in the water are natural residents in the water, and some come from the soil, which falls from the air with dust and generally has no pathogenic effect on the human body. In addition, some will bring endless disasters to the human body. This part enters the water body with garbage, human and animal feces, animal and plant carcasses, industrial and agricultural wastewater and wastes (especially infectious disease hospitals). In addition to various inorganic substances (such as heavy metals, arsenic and other minerals) and organic substances (such as oils, petroleum, nutrients and detergents), there are also some pathogens. Some pathogens can survive in the water environment for a long time, and the close relationship between people and water leads to the epidemic of infectious diseases.
There are three kinds of water-borne diseases: ① Typhoid fever and paratyphoid fever caused by bacteria, bacillary dysentery, cholera, paratyphoid fever and diarrhea caused by Escherichia coli; ② Caused by viruses, mainly viral hepatitis A, viral gastroenteritis and poliomyelitis. What is worth mentioning here is polio, also known as "polio" (poliovirus is an enterovirus, which mainly breeds in the intestine and pollutes water with feces. At present, oral attenuated live vaccine is used as prevention, and the effect is very good); ③ It is caused by parasites, mainly schistosomiasis caused by amoeba dysentery and amoeba protozoa.
According to the survey of the World Health Organization, more than 80% residents in developing countries have no access to safe drinking water. Various diseases caused by unsanitary drinking water are as high as 600 million person-times every year, resulting in tens of thousands of deaths every day, and about 50% of children's deaths are related to drinking water. The quality of drinking water is directly related to people's health, so effective measures should be taken to manage drinking water.
Microbial pathogens also pollute soil and do harm to human body. There are three main ways: ① "human-soil-human" way, that is, pathogens discharged by human body directly pollute soil through fertilization and sewage irrigation, and people are infected through direct contact with soil or eating fruits and vegetables grown on soil raw. In addition to bacterial and viral diseases caused by microbial pollution in water, it mainly causes intestinal parasitic diseases. Ascariasis is one of them. Ascariasis has spread all over the world, and it is reported that the infection rate in China can reach more than 70%, which is significantly higher in rural areas than in cities. The prevalence of hookworm disease is also very common in China, and anemia is the main symptom of hookworm disease. (2) The pathogens discharged by sick animals pollute the soil, and people get sick through direct contact with the polluted soil, which is the "animal-soil-human" model. The most noteworthy thing in this respect is the acute infectious disease caused by Bacillus anthracis. Anthrax is an infectious disease of herbivores, but Bacillus anthracis can enter the human body from damaged skin, gastrointestinal tract and respiratory mucosa to release toxins. The main manifestations are skin necrosis or specific depression, acute infection of lung, intestine and meninges, and sometimes accompanied by anthrax septicemia. (3) Pathogens existing in natural soil, people will get sick when they come into contact with contaminated soil, that is, the "soil-human" way. Tetanus is a serious infection caused by exotoxin produced by tetanus Bacillus invading through a wound. The main clinical manifestations are clenching teeth, local or systemic muscle rigidity and paroxysmal spasm. Tetanus widely exists in human and animal intestines, excreted with feces, forms spores in the external environment and can survive for many years. Because it is widely distributed in nature and exists in general soil, it is considered as a pathogen existing in natural soil.
Harmless sterilization of human and animal manure and sludge applied to soil is an effective method to prevent soil biological pollution.
Microorganisms can also pollute food, vegetables and fruits, eggs and meat, aquatic products, cooking oil, salt and sugar and other condiments, cakes, tea, milk, alcohol, cold drinks and so on. The effects of biological pollution of food on human health can be roughly divided into three categories: bacterial food poisoning, fungal food poisoning and parasitic diseases.
The food that causes bacterial food poisoning is mainly contaminated animal food, such as fish, meat, milk and its products. Of course, other contaminated food can also cause poisoning. After food is contaminated by pathogenic bacteria, the pathogenic bacteria multiply in large numbers under suitable conditions, and the food is not heated or heated incompletely before eating, which makes people poisoned after eating. There are many pathogenic bacteria that can cause human food poisoning. For example, yersinia enterocolitica is a psychrophilic bacterium, which can still reproduce at low temperature (0℃). Food poisoning is mainly caused by contaminated meat and milk, and the infant infection rate is high. Common symptoms include diarrhea, abdominal pain, nausea and vomiting. So don't store the food in the refrigerator for too long. In addition, there are Clostridium botulinum, Bacillus cereus, Vibrio parahaemolyticus, Salmonella and pathogenic Escherichia coli. Clostridium botulinum exists in soil, dust and animal feces, and can produce a strong neurotoxin under anoxic conditions. After the toxin is absorbed by the digestive tract, it can cause muscle paralysis, damage the cranial nerves, and be accompanied by symptoms of the central nervous system such as unstable walking. Botulinum poisoning in China is mostly caused by plant foods, such as homemade fermented soybean and soybean paste. Botulinum toxin is unstable to heat, and it can be completely destroyed when heated to 100℃ for about 10 ~ 20 minutes. Bacillus cereus is widely distributed in nature and can reproduce at room temperature, which leads to the deterioration of rice and cooked food. Vibrio parahaemolyticus is a halophilic bacterium, and the symptoms of food poisoning caused by Vibrio parahaemolyticus are paroxysmal colic and watery stool in the upper abdomen.
Some fungi parasitize in grain and feed, which will produce toxic metabolites or toxins. These toxins have strong heat resistance and will not be destroyed by ordinary heating. Once people and livestock eat contaminated grain or feed, poisoning may occur. At present, more than 300 mycotoxins have been found, among which aflatoxin and Fusarium graminearum toxin have great influence on human health.
Aflatoxin is the metabolite of Aspergillus flavus, parasitic mold and other strains. There are more than ten kinds of structures that have been defined, mainly polluting grain and oil and their products. It is more toxic to experimental animals than potassium cyanide and can also cause acute poisoning in humans. Aflatoxin has a strong carcinogenic effect on animals and can induce liver cancer, but it is difficult to obtain direct evidence on the relationship between human liver cancer. Nevertheless, at present, many countries have formulated the hygienic standard for the allowable content of aflatoxin in food, which is generally in the range of 5 ~ 20 μ g/kg.
Wheat scab is an important disease of food crops. Farmers in China have discovered scab wheat for a long time, which is called "coma wheat" because it will cause coma after eating, and the pathogenic mold is Fusarium graminearum. After eating wheat with scabs by mistake, people feel dizzy and bloating, and those with severe digestive tract symptoms have headaches and facial flushing.
Food contaminated by parasites can cause various parasitic diseases, the most common of which are ascariasis, taeniasis, trichinosis, amoebiasis and liver fluke disease. It is worth mentioning that taeniasis, including beef taeniasis and pork taeniasis, is caused by different kinds of taeniasis. The intermediate host of Taenia solium is mainly pigs, followed by dogs, cats and sheep, and the final host is human. After the pregnant section of tapeworm containing eggs is swallowed by pigs with feces, hookworms hatch and drill into various parts of pigs to form cysticercosis, which is mostly in muscles and visible to the naked eye, commonly known as "rice pork". People are infected by eating undercooked "rice and pork". Cysticercosis develops into an adult in the human intestine, which can be as long as 2 ~ 4 meters, causing symptoms of intestinal mucosal damage.