Tin is a silvery white metal with a slight blue color. Atomic weight 1 18.70, density 5.75g/cm3, melting point 23 1.89℃, boiling point 2260℃. Tin has the characteristics of high ductility, good corrosion resistance, low melting point and high boiling point. It does not react with dilute sulfuric acid and dilute hydrochloric acid at room temperature, but is soluble in dilute nitric acid and hot alkali. When the temperature is lower than 13.2℃, tin can be transformed into powder gray tin.
The valence states of tin are +2 and +4, but all its important compounds are +2.
Occupational contact
Tin is used as a protective layer for metals, such as the inner layer of canned food and tinned wires. Tin is often used to weld metal, tin alloy (such as tin-zinc alloy) is used as the protective shell of sluice parts, and tin-cadmium alloy is used as the coating of machine parts.
Inorganic compounds of tin are often used in textile industry, such as stannous chloride as reducing agent in white cotton printing and dyeing; Hydrated stannic acid, sodium silicate, hydrated stannic chloride and ammonium stannate are used as mordants for printing and dyeing. In addition, it is also used in the glass and enamel industry. Therefore, workers in these industries have the opportunity to contact inorganic compounds of tin. The workers who have more contact opportunities are tin miners and tin smelters. Tin workers are mostly exposed to tin dioxide (SnO2), and some are tin sulfides, such as stannous minerals (Cu2FeSnS and PbZnSn2). Tin smelters are mainly exposed to tin dioxide dust.
clinical picture
1. Acute poisoning
It is reported that the lowest concentration of acute poisoning caused by tin-contaminated canned food and fruit is 5 mg/kg. In addition, it has been reported that eating canned fruits with tin pollution concentration of 563mg/kg or 400mg/kg can cause acute gastroenteritis symptoms such as nausea, vomiting and diarrhea. This should be differentiated from acute bacterial gastroenteritis and given symptomatic support treatment.
2. Tin pneumoconiosis
Tin smelters work in an environment with a tin dust concentration of 9.362mg/m3, and tin pneumoconiosis occurs. Clinically, there are few symptoms such as cough, expectoration and chest tightness, and most patients have no change in lung function. Chest X-ray films are typically clustered round or quasi-round speckled shadows widely distributed in both lung fields, like small osmanthus flowers with petals, but they are not fused with each other, with a diameter of 3 ~ 5 mm, high density and sharp edges. The hilum is usually not enlarged. Most lung textures are unrecognizable or only faintly visible. After the diagnosis of 10 ~ 15 years, the variegated shadows in both lung fields gradually became smaller, the density decreased and the number decreased. The lung field gradually became clear, but the hilum density gradually increased. After 25 ~ 30 years, there are many kinds of metallic massive shadows in hilum, but the lung field is basically clear.
3. Chronic effects
Workers exposed to stannic chloride for a long time may have respiratory tract irritation and digestive tract symptoms, such as nausea, epigastric discomfort, constipation, and sometimes shoulder and foot pain. Tin tetrachloride can still cause skin ulcers and eczema.
Diagnosis and differential diagnosis
The diagnosis of tin pneumoconiosis should be based on occupational history, clinical manifestations and chest X-ray examination. However, other lung diseases should be excluded and differentiated from silicosis.
treat cordially
Give priority to with symptomatic treatment. According to reports, after tin pneumoconiosis patients are out of contact, after a slow process, the cluster shadows in the lungs are alleviated or disappeared to varying degrees, regardless of treatment. It is also reported that sodium dimercaptopropane sulfonate can be used to expel tin and reduce lung lesions.
prevent
Tin smelting and crushing processes should be mechanized and sealed, and ventilation and dust removal should be strengthened. Besides strengthening personal protection, workers exposed to tin dust should also be monitored regularly.