Adults breathe about 10 ~ 12 cubic meters of air every day, and harmful chemicals in the atmosphere generally enter the human body through the respiratory tract. There are also a few harmful chemicals entering the human body through the digestive tract or skin. The impact of air pollution on health depends on the type, nature, concentration and duration of harmful substances in the atmosphere, and also depends on the sensitivity of human body. For example, the harmful effect of floating dust on human body depends on the particle size, hardness, solubility and chemical composition of floating dust, as well as various harmful gases and microorganisms adsorbed on the surface of dust particles. Different chemical properties, toxicity and water solubility of harmful gases will also cause different degrees of harm. In addition, the structure of each part of the respiratory tract is different, and the retention and absorption of poisons are also different. Generally speaking, the deeper the entry, the larger the area, the longer the residence time and the greater the absorption. Adult alveoli have a total area of about 55 ~ 70 square meters and are covered with capillaries. Poison can be quickly absorbed by alveoli and sent to the whole body through blood, and it can work without the transformation of liver, so it is most harmful for poison to enter the body from respiratory tract.
Inhalation of harmful chemicals (such as sulfur dioxide, sulfuric acid fog, chlorine, ozone, smoke, etc.) that directly stimulate the respiratory tract will cause bronchial reflex contraction, spasm, cough, sneezing and increased airway resistance. Under the chronic action of poisons, the resistance of respiratory tract will gradually weaken, thus inducing chronic respiratory diseases, and even serious pulmonary edema and pulmonary heart disease may occur. Epidemiological survey data show that urban air pollution is the direct cause or inducement of chronic bronchitis, emphysema and bronchial asthma. In areas with serious air pollution, the total mortality and incidence of respiratory diseases are higher than those in areas with light pollution. The symptoms of chronic bronchitis get worse with the aggravation of air pollution.
There are also potentially harmful chemicals in the air around cities, especially some factories, such as cadmium, beryllium, antimony, lead, nickel, manganese, mercury, arsenic, fluoride, asbestos and organochlorine pesticides. Although their concentration is very low, they can gradually accumulate in the body. These toxic pollutants in the atmosphere can also land on crops, water bodies and soil, and then be absorbed by crops and enriched in vegetables, fruits and grains, and can also accumulate in the human body through food and drinking water, leading to chronic poisoning. The harm of these substances to the body is not obvious in the short term. Long-term accumulation will also affect the nervous system, visceral function, reproduction and heredity.
Another pollutant harmful to human health in the atmosphere is radioactive substances, which mainly come from nuclear explosion products. Some tiny radioactive dust can be suspended in the atmosphere for many years. The mining and processing of radioactive minerals and the production and application of radioactive substances will also cause air pollution. The atmospheric pollution is mainly caused by radioactive elements with long half-lives, such as fission products of uranium, among which 90 strontium and 137 cesium are very important. Radioactive elements have external irradiation effect on the body in vitro; When it enters the body through the respiratory tract, it has an internal irradiation effect. The concentration of radioactive substances in the lungs is usually higher than that in other organs, so lung tissue is generally strongly irradiated. Lung macrophages can form radioactive sources with high ionization density after swallowing radioactive particles. Radioactive substances entering the lungs can spread throughout the body very quickly. Except in nuclear explosion areas, radioactive substances in the atmosphere generally do not cause acute radiation sickness, but low-dose external irradiation or long-term internal irradiation beyond the allowable range can also cause chronic radiation sickness or chronic skin damage. The more important effects of radioactive substances in the atmosphere on the human body are long-term effects, including cancer, infertility, genetic changes or premature death.
Biological pollutants in the atmosphere are air allergens, mainly including pollen and some mold spores. These airborne substances can cause allergic reactions in individuals. Air allergens can induce rhinitis, asthma and allergic lung diseases. The other is pathogenic microorganisms. Pathogenic microorganisms with weak resistance are easy to die in sunlight and dry conditions, and the number is very small in the general air. Pathogenic microorganisms with strong resistance, such as mycobacterium tuberculosis, carbuncle, pyogenic cocci, etc., can attach to dust particles and pollute the atmosphere.