Toluene and xylene are colorless, transparent and volatile liquids with aromatic odor. Toluene boiling point 110.4 ℃, xylene has three isomers, namely, o-, inter- and para-, three isomers with similar physical and chemical properties, molecular weight 106.16, are insoluble in water, soluble in ethanol, acetone and chloroform and other organic solvents. Contact opportunities Used as intermediates in chemical production, as solvents or diluents for paint, spray paint, rubber and other industries, used in the manufacture of dyes and synthetic fibers, etc. Toxicokinetics Toluene and xylene are low toxicity, can be absorbed through the respiratory tract, skin, digestive tract, in the blood circulation, mainly adsorbed on the red blood cell membrane and plasma lipoproteins, and later accumulate in lipid-rich tissues, most in the adipose tissue and adrenal glands. It can act directly on the embryo through the placental barrier, but its carcinogenic and mutagenic effects have not been confirmed. Human oral LDL0 is 50mg/kg, rat oral LD50 is 2~4.3g/kg. High concentration of toluene and xylene mainly produce anesthetic effect on the central nervous system; the irritating effect on skin mucous membrane is stronger than benzene, skin contact can cause erythema, dryness, defatting and chapping, etc. The effect of pure toluene and xylene on the blood system is not obvious. Clinical manifestations 1, acute poisoning: short exposure to high concentrations of toluene, xylene can appear in the central nervous system dysfunction and skin mucous membrane irritation symptoms. In mild cases, headache, dizziness, staggering gait, excitement, etc., mild respiratory and conjunctival irritation; in severe cases, nausea, vomiting, confusion and even coma, accompanied by eye and upper respiratory irritation, conjunctivitis and pharyngitis may occur. Liquid contamination of the eye can cause conjunctivitis and corneal damage. In recent years, serious liver damage caused by oral poisoning with mixed benzene (xylene, toluene and benzene) has been a cause for concern. 2, chronic poisoning: long-term exposure to low and medium levels of toluene and xylene can cause varying degrees of dizziness, headache, fatigue, sleep disorders and memory loss, and temporary mild changes in peripheral blood picture, which can return to normal after leaving the exposure. Chronic dermatitis and skin cracking can occur with skin exposure.