Toxic substances exist widely in the process of scientific research and production, from raw materials to products, from intermediate products to by-products, from various chemicals to waste water, waste gas and other wastes. Therefore, the main ways of poison invading human body are respiratory tract, skin and digestive tract
1. Respiratory tract is the most important, common and dangerous way for poison to enter human body
poisons exist in the form of gas, steam, smoke, dust and fog in scientific research and production. Gas and steam are in molecular state and can directly enter human alveoli. When the particle size of smoke, dust and fog is less than 5 μ m, especially less than 3 μ m, they can be directly inhaled into alveoli
People’s whole respiratory tract has great respiratory capacity, so the absorption of poisons is very fast, and the poisons entering the human body through the respiratory tract are directly distributed to the whole body through the blood circulation without detoxification of liver and viscera
particles larger than 10 microns can not enter the human body through the nasal cavity and upper respiratory tract2. Skin: there are many ways of skin absorption, through non-invasive skin; Percutaneous pore and sweat gland; Through the hair follicle and sebaceous gland
transdermal surface is the main way of skin absorption. Toxic substances with fat solubility and water solubility are easily absorbed by human body through the skin surface, such as benzene, organophosphorus compounds, etc
the quantity and speed of toxicants absorbed through the skin are not only related to the concentration of fat soluble and water-soluble, but also related to the temperature and humidity of the working environment, the degree of skin damage and the contact area< (3) digestive tract: in scientific research and production, it is rarely seen that poisons enter the human body through the digestive tract, which is generally caused by taking them by mistake some of the toxicants entering the respiratory tract adhere to the nasopharynx or mixed in the secretion, enter the digestive tract by swallowing, or enter the digestive tract due to bad hygiene habits or eating in the laboratory or workshop where the toxicants are used, smoking, or taking contaminated food by hand