What is Silicosis?

Silicosis, also known as silicosis, is the most common type of pneumoconiosis. It is caused by long-term inhalation of a large amount of free silica dust and is mainly caused by extensive nodular fibrosis in the lungs. Silicosis is the most common, fastest progressing, and most harmful type of pneumoconiosis. There are about 20,000 new cases of pneumoconiosis in China every year. Therefore, the prevention and treatment of pneumoconiosis is a difficult task.

Basic Information

Also known as: Silicosis
English name: pulmonarysilicosis
Visiting department: Department of Pathology

Common locations: Lungs
Common causes: Dust concentration in air, contact time, dust dispersion, body state

Causes of silicosis

Dust concentration in the air

The higher the free SiO ₂ content in the environmental dust, the higher the dust concentration, and the greater the harm. Dust concentration is expressed in mg / m ^3. When the content of free SiO _{2 in the} dust is large and the concentration is high (tens or even hundreds of mg / m ³ ), silicon nodules are formed in lung tissue after long-term inhalation.

2. Contact time

The development of silicosis is a chronic process. It usually develops after 5 to 10 years of continuous inhalation of silicon dust, and some of them last for more than 5 to 20 years. However, continuous inhalation of dust with high concentration and high content of free silica can cause disease after 1 to 2 years, which is called "rapid silicosis".

3.Dust dispersion

Dispersion is a measure of the size of dust particles, expressed as a percentage of the diameter of various particles in the dust. The larger the proportion of small particle dust, the greater the dispersion. The degree of dispersion has a close relationship with the floating of dust particles in the air and its retention sites in the respiratory tract. Dust particles larger than 10um settle quickly in the air, and are blocked by nasal and nasal hair even if inhaled, and discharged with snot; most of the dust below 10um is blocked by the upper respiratory tract; dust below 5um can enter the alveoli; For dust below 0.5um, because of its small gravity, it is not easy to settle, and it is discharged with exhalation, so the retention rate decreases. However, for dust below 0.1um, the retention rate increases due to Brownian motion.

4. Body status

The human respiratory tract has a series of defensive devices. When the inhaled dust passes through the nasal cavity first, it is blocked by the filtering effect of the nasal hair and the nasal septum is bent. Generally, it is 30% to 50% of the inhaled dust; the dust entering the trachea and bronchus is extremely large. Part of it can be blocked by bifurcation of the bronchial tree, movement of mucous epithelial cilia and excreted with sputum; part of the dust particles are engulfed by macrophages or alveolar interstitial macrophages into dust cells. Enter the hilar lymph nodes along the lymphatic vessels.

Those with chronic respiratory inflammation have poor clearance of the respiratory tract, and respiratory infections, especially tuberculosis, can promote the rapid progress and exacerbation of silicosis. In addition, individual factors such as age, health quality, personal hygiene habits, and nutritional status are also important conditions that affect the incidence of silicosis.

Clinical manifestations of silicosis

There are three forms: chronic silicosis, acute silicosis, and accelerated silicosis in between. These two clinical manifestations have significant relationships with dust exposure, silicosis content, and exposure duration. Chronic silicosis is the most common clinical form.

Generally early asymptoms or symptoms are not obvious, with the progress of the disease can appear a variety of symptoms. Shortness of breath often appears earlier and increases progressively. I often feel chest tightness and chest pain in the early stage, and the chest pain is mild, which is bloating, tingling or tingling, and has nothing to do with breathing, body position and labor. The degree of chest tightness and shortness of breath is related to the extent and nature of the lesion. Early inhalation of silicon dust can cause irritating cough, and concurrent infection or smokers may have sputum. A few patients have blood sputum. Repeated or massive hemoptysis may be associated with tuberculosis, lung cancer, or bronchiectasis. Patients may still have symptoms such as dizziness, fatigue, insomnia, palpitations, and poor appetite. Stage silicosis due to massive fibrosis shrinks the lung tissue, resulting in bronchial displacement and dull dullness.

Silicosis

Pulmonary function test

Due to the strong compensatory ability of the lung tissue, the pulmonary function tests of early patients were normal. Velocity of pulmonary fibrosis increases, lung compliance decreases, and restrictive ventilatory dysfunction may occur, such as reduced vital capacity, total lung capacity, residual capacity, and maximum ventilation capacity. Generally, the lung capacity of patients with stage I is 10% to 20% lower than normal people. %, Phase II decreased by 20% to 30%, and phase III decreased by 30% to 50%. At the same time, there is diffuse dysfunction, and in severe cases, hypoxemia can occur. If the patient is associated with slow branches and emphysema, it may be accompanied by obstructive ventilation dysfunction, which is manifested as mixed ventilation dysfunction. Pulmonary function measurement is of little significance in diagnosis and is mainly used as the basis for labor capacity identification.

2. X-ray performance

X-ray chest radiography is the main method for diagnosing silicosis. Mainly manifested as nodular shadows (diameter is generally 1 to 3mm), reticular shadows or (and) large fusion lesions. Followed by hilum changes, lung texture changes and pleural changes. Patients with silicosis who are exposed to high levels and high concentrations of silicon dust are usually dominated by round or round-like shadows. They appear early in the inner and middle zones of the two middle and lower lungs, with the right side being the most, and then gradually expanding upward. Appears on both upper lobe. Low silicon dust or mixed dust, mostly round or irregular shadows. Large shadows are more common in the upper and lower lobes of the upper lobe of the two lungs, and are often symmetrically shaped with trans-lobes in the figure. The outer edge of the lung field has increased transparency. Due to the massive pulmonary fibrosis, the hilum is moved upward, the thickened lung pattern is weeping willow, and tracheal mediastinal displacement occurs. The hilar shadow density increases, sometimes with "egg-like calcification" of the lymph nodes. The pleura may have thickening, adhesions, or calcification.

Silicosis diagnosis

Based on reliable production dust exposure history and on-site labor hygiene survey data, the main chest radiograph performance after X-rays with qualified technical quality is taken as the main basis, with reference to dynamic observation data and pneumoconiosis epidemiological investigations, combined with clinical manifestations and experiments After laboratory examinations and other similar lung diseases were excluded, a diagnosis and X-ray staging of pneumoconiosis were made against the pneumoconiosis diagnostic standard.

Silicosis complications

Tuberculosis

It is a common serious complication of silicosis, up to 20% to 50%, and it increases with the progress of silicosis. The incidence of tuberculosis in stage I-II is 10% to 30%, and that of stage III is 50% to 90%. Tuberculosis accounts for 45% of the direct causes of silicosis. When silicosis is complicated by tuberculosis, it will promote each other and accelerate the deterioration. Toxic symptoms such as fever often occur, and hemoptysis is one of the symptoms. Tuberculosis bacteria can be found in sputum.

2. Lung infection

It is the most common complication of silicosis, which can promote the development of silicosis, induce respiratory failure and death. Therefore, it is important to actively prevent and treat respiratory infections, especially for advanced silicosis.

3. Chronic bronchitis and obstructive emphysema

Bronchial ciliary epithelium is damaged by long-term inhalation of dust. Diffuse nodule fibrosis of the lungs causes bronchoconstriction, poor drainage, and prone to infection. It is accompanied by slow branch and pulmonary heart disease, which can induce respiratory failure and right heart failure in severe infections.

4. Spontaneous pneumothorax

More common in patients with emphysema and bullae, especially patients with advanced silicosis. Lung infection, severe cough, and exertion are common causes. Common symptoms are sudden dyspnea and chest pain, which can be asymptomatic. Silicosis complicated by pneumothorax has a high recurrence rate, local pneumothorax is more common, and the signs are atypical. Due to fibrosis of lung tissue and pleura. The fracture is more difficult to heal, and the gas is absorbed slowly.

Silicosis treatment

Pneumoconiosis patients should be promptly removed from the dust operation, and comprehensive treatment should be carried out according to the needs of the disease to actively prevent and treat tuberculosis and other complications in order to reduce symptoms, delay the progress of the disease, improve patient life and improve the quality of life of patients.

Prognosis of silicosis

Once the silicosis patients are diagnosed, they should be removed from the dust and given active comprehensive treatment. Life expectancy can be extended to the average life expectancy of ordinary people, but their labor may be lost to varying degrees. Silicosis is often caused by severe tuberculosis, spontaneous pneumothorax, and respiratory failure.

Silicosis prevention

Patients have a close history of silicon dust exposure and a detailed occupational history, causing many types of silicosis. Workers who have been in contact with various metals, coal powder, refractory materials, stone powder, cement, glass, ceramics and other types of work for a long time.

1. The key to controlling or reducing the incidence of silicosis is to prevent dust. Industrial and mining enterprises should pay attention to comprehensive dust prevention measures such as reforming production processes, wet operations, closed dust sources, ventilation and dust removal, and equipment maintenance and repair.

2. Strengthen personal protection and observe dust-proof operation regulations. Regularly monitor the dust concentration in the air for the production environment and strengthen publicity and education. Do a good physical examination before employment, including X-rays.

3. People with active tuberculosis inside and outside, as well as patients with various respiratory diseases, should not participate in silica dust work. Intensify the regular physical examination of silicon dust workers, including X-ray chest radiographs. The interval between examinations depends on the silicon dioxide exposure and air dust concentration.

4. Strengthen the prevention and control of tuberculosis in industrial and mining areas. Those who are negative for the tuberculin test should be vaccinated with BCG; those who are positive should be given prophylactic antituberculosis chemotherapy to reduce the incidence of silicosis and tuberculosis.

5. Comprehensive measures should be taken for patients with silicosis, including detachment from the dust, and appropriate work should be arranged separately to strengthen nutrition and proper rehabilitation exercises to enhance physical fitness. Prevention of respiratory infections and complications.