In nature, free silica is widely distributed, accounting for about 5% in the crust within the range of 16km, and 95% of ores contain different amounts of free silica. Free silica dust, commonly known as silica dust, accounts for 99% of the free silica in time, and silica timely dust is often regarded as the representative of silica dust.
According to the crystal structure, free silica can be divided into three types: crystalline, cryptocrystalline and amorphous. Tetrahedral arrangement rules of crystalline free silica such as tridymite and quartz, granite or other minerals; The silicon tetrahedron of aphanitic free silicon is irregularly arranged, mainly agate, flint and timely glass; Amorphous free silica mainly exists in diatomite, silica gel and opal, silica vapor produced by timely smelting and aerosol condensed in the air.
The higher the content of free silica in dust, the shorter the onset time and the more serious the illness. Experiments show that the fiber-forming ability of different time variants is tridymite >: Fang time > time > coesite > super time; Different crystal structures have different fiber-forming abilities, and the order is crystalline >: invisible > amorphous.
Harm of silica dust to human body
Exposure to silica dust is generally asymptomatic or not obvious in the early stage, and various symptoms may appear with the progress of the disease. Shortness of breath often occurs earlier and gets worse gradually. I often feel chest tightness and chest pain in the early stage, and the chest pain is mild, which is swelling pain, dull pain or tingling, and has nothing to do with breathing, posture and delivery. The degree of chest tightness and shortness of breath is related to the scope and nature of the lesion. In the early stage, irritating cough may occur due to inhalation of silica dust, and those with infection or smokers may have expectoration. A few patients have bloody sputum. When combined with tuberculosis, lung cancer or bronchiectasis, repeated or massive hemoptysis may occur. Patients can still have dizziness, fatigue, insomnia, palpitations, loss of appetite and other symptoms. Stage Ⅲ silicosis causes lung tissue to contract due to massive fibrosis, which leads to bronchial displacement and dullness.
Silicosis caused by silica dust generally occurs slowly, usually after exposure to low concentration of free silica dust 15 ~ 20 years. However, after the onset, the lesion can continue to develop even if it is separated from dust work. A few people get sick after 1 ~ 2 years due to continuous inhalation of dust with high concentration and free silica content, which is called "rapid pneumoconiosis". Others were sick and exposed to high concentrations of dust, but they left the silica dust operation for a short time. At this time, no obvious abnormality was found in the X-ray chest film, but they were diagnosed with silicosis after several years of exposure to dust, which was called "late-onset silicosis". Silicosis is mainly manifested in abnormal lung function and chest X-ray.
1. Abnormal lung function
Because of the strong compensatory ability of lung tissue, there was no abnormality in lung function examination of early patients. Pulmonary fibrosis increases rapidly, lung compliance decreases, and restrictive ventilation dysfunction may occur, such as decreased vital capacity, total lung capacity, residual volume and maximum ventilation volume. Generally, the vital capacity of patients with rheumatoid arthritis is 65,438+00% ~ 20% lower than that of normal people, 20% ~ 30% lower in stage II and 30% ~ 50% lower in stage III. At the same time, there is diffusion dysfunction, and in severe cases, hypoxemia may occur. If the patient is complicated with chronic bronchitis and emphysema, it may be accompanied by obstructive ventilation dysfunction, which is manifested as mixed ventilation dysfunction. The determination of lung function is of little significance in occupational disease diagnosis and occupational health examination (the author's personal opinions are for reference only), and it is mainly used as the basis for labor ability appraisal.
2.x-ray abnormal performance
The main manifestations are nodular shadows (average diameter 1 ~ 3 mm), reticular shadows or (and) large fusion lesions. Followed by hilar changes, lung texture changes and pleural changes. Silicosis patients exposed to high-content and high-concentration silica dust often have circular or quasi-circular shadows, which appear in the medial zone of the lower and middle lungs in the early stage, mostly on the right side, and then gradually expand upwards, or appear in the upper and lower lungs first. The amount of silica dust is low or mixed dust is mostly round or irregular shadow. Large shadows are usually seen in the outer and middle areas of the upper lobes of both lungs, which are often symmetrically crossed leaves, and the transparency of the outer lung field is increased. Due to the contraction of a large number of pulmonary fibrosis, the hilum of the lung moves up, making the thickened lung lines look like weeping willows, leading to the displacement of trachea and mediastinum. The shadow density of hilum increases, and sometimes "eggshell calcification" lymph nodes can be seen. Pleura may be thickened, adhered or calcified.
Four, the main complications of silicosis
1. Tuberculosis
The common serious complications of silicosis are as high as 20% ~ 50%, and increase with the progress of silicosis staging. The prevalence rate of stage ⅰ-ⅱ pulmonary tuberculosis is 10% ~ 30%, and stage ⅰ-ⅱ is more than 50% ~ 90%. Tuberculosis accounts for 45% of the direct death cause of silicosis. Silicosis complicated with pulmonary tuberculosis will promote each other and accelerate the deterioration. Poisoning symptoms such as fever often appear, and hemoptysis is one of the symptoms. Tuberculosis can be found in sputum.
2. Lung infection
The most common complication of silicosis can promote the development of silicosis and induce respiratory failure and death. Therefore, we should actively prevent and treat respiratory tract infections, especially for advanced silicosis.
3. Chronic bronchitis and obstructive emphysema
Long-term inhalation of dust will damage bronchial ciliary epithelium. Diffuse nodular fibrosis of lung leads to bronchial stenosis, poor drainage, easy infection, chronic bronchitis and cor pulmonale. Severe infection can induce respiratory failure and right heart failure.
4.spontaneous pneumothorax
It is more common in patients with emphysema and bullae, especially in patients with advanced silicosis. Pulmonary infection, severe cough and fatigue are common causes. The common symptoms are sudden dyspnea with chest pain or asymptomatic. The recurrence rate of silicosis complicated with pneumothorax is high, localized pneumothorax is common, and the signs are atypical. Because of fibrosis of lung tissue and pleura. Fracture is difficult to heal and gas absorption is slow.