Silicosis
OVERVIEW
What is silicosis?
Silicosis, also known as pneumosilicosis, is an abbreviation for silicosis. It is a lung disease caused by long-term inhalation of dust containing large amounts of silica (sand is essentially silica dioxide, while the particles inhaled into the lungs are extremely fine, most commonly found in mining and certain mineral-crushing factories). The main pathological changes are pulmonary fibrosis and the formation of silicotic nodules. Silicosis is one of the most common and severe types of pneumoconiosis in China.
Silicosis is the most severe type of pneumoconiosis in China. So what is pneumoconiosis?
Pneumoconiosis is the abbreviation for pneumoconiosis. As the name suggests, it refers to a lung disease caused by the inhalation and deposition of harmful external dust in the lungs, leading to lung tissue damage and fibrosis. It is a common occupational lung disease.
What are silicotic nodules in silicosis?
Generally, people cannot see the actual condition of lung lesions, but on X-ray films, very distinct granular images different from those of healthy individuals can be observed. These are composed of silicotic nodules, which are round or oval nodules in the lungs of silicosis patients. In the early stages, they are cellular nodules formed by the aggregation of cells that have engulfed silica dioxide. As the disease progresses, the nodules undergo fibrosis to form fibrous nodules, and eventually develop into collagenous nodules. Silicotic nodules impair normal lung function.
Is silicosis common?
According to a nationwide epidemiological survey on pneumoconiosis, in 2008, the Ministry of Health reported 638,234 cases of pneumoconiosis in China, accounting for 90.7% of occupational diseases. Among these, silicosis cases made up 48.3% of the total pneumoconiosis cases. This shows that China has a high incidence of silicosis, and its prevention and treatment remain a challenging task.
SYMPTOMS
What are the classifications of silicosis?
Due to differences in the free silica content in dust, workplace dust concentrations, and the resulting clinical manifestations, disease progression, outcomes, and pathological changes, silicosis is generally classified into the following types:
- Chronic silicosis: The free silica content in dust is below 30%, and exposure duration ranges from 20 to 45 years. Fibrotic nodules are the primary pathological feature, with minimal impact on lung function. Pathological changes in chronic silicosis continue to progress slowly even after exposure to dust ceases. Symptoms often include chest tightness, chest pain, and difficulty breathing, which are initially mild and gradually worsen over time.
< - Accelerated silicosis: The free silica content in dust ranges from 40% to 80%, with exposure duration typically between 5 and 15 years before onset. Fibrotic nodules are larger, disease progression is rapid, and lung function impairment is often severe. This type is common among quartz millers and sandblasters. Symptoms include sudden shortness of breath, chest pain, coughing with sputum, and occasionally blood in the sputum.
< - Acute silicosis: A rare form of pneumoconiosis caused by high concentrations of silica dust, usually developing within 1 to 4 years of exposure. It progresses rapidly and can lead to death from respiratory failure. Symptoms include progressively worsening shortness of breath, chest pain, loss of appetite, dizziness, weakness, and excessive sweating. This is the most severe form.
What are the stages of silicosis?
Based on the number, distribution, size of silicotic nodules, and the extent of pulmonary fibrosis, silicosis is clinically divided into three stages:
- Stage I silicosis: Few and small silicotic nodules, mainly located in the middle and lower lobes of both lungs. Lung weight, volume, and hardness show no significant changes. The condition is mild. X-rays reveal small shadows with diameters of 1–3 mm.
< - Stage II silicosis: Increased number and size of silicotic nodules, scattered throughout the lungs. Lung weight, volume, and hardness slightly increase. X-rays show numerous shadows smaller than 1 cm in diameter.
< - Stage III silicosis: Denser and larger silicotic nodules, often merging into irregular masses resembling tumors. Lung weight and hardness significantly increase. X-rays reveal large mass-like shadows exceeding 2 cm in diameter, with enlarged hilar lymph nodes.
Stage I is the mildest, Stage II is moderate, and Stage III represents severe, advanced silicosis.
What are the symptoms of silicosis?
- Early-stage silicosis may have no symptoms or only mild ones, such as chest tightness and slight pain. Patients often discover the condition during routine physical exams or chest X-rays.
< - In Stages II to III, respiratory symptoms become more apparent, including difficulty breathing, chest tightness, coughing, and sputum production. Some patients may experience hemoptysis (blood in sputum), with recurrent or severe bleeding if complicated by bronchiectasis or tuberculosis.
< - Beyond respiratory symptoms, late-stage silicosis patients often develop tuberculosis, accompanied by loss of appetite, weakness, weight loss, and night sweats.
What are the complications of silicosis?
- Tuberculosis: Silicosis-associated tuberculosis, called silicotuberculosis, occurs due to reduced lung defense against Mycobacterium tuberculosis. The risk increases with silicosis severity and is a leading cause of death in patients.
< - Cor pulmonale: A heart condition caused by lung damage, leading to right heart strain. Over 60% of late-stage silicosis patients develop cor pulmonale.
< - Lung infections: Weakened immunity and impaired respiratory defenses make silicosis patients prone to bacterial or viral infections, which can be fatal.
< - Obstructive emphysema and spontaneous pneumothorax: Late-stage patients often develop emphysema. Alveolar wall rupture forms bullae, which may rupture during coughing or exertion, causing pneumothorax.
Can silicosis develop into lung cancer?
Silicosis can progress to lung cancer. Chronic lung infections and irritation from nodules increase the risk of malignant transformation over time.
CAUSES
What are the causes of silicosis?
Silicosis is caused by long-term inhalation of dust containing free silica. Free silica refers to silica that exists independently in rocks without combining with other substances.
The onset of silicosis is related to factors such as the amount of silica inhaled, particle size, duration of exposure, presence of protective measures, and individual health conditions. The higher the content of free silica in the dust, the shorter the onset time and the more severe the condition. Prolonged exposure to silica dust leads to greater accumulation of dust in the lungs, resulting in more significant harm. Individuals with a history of tuberculosis, especially active tuberculosis during dust exposure, or other chronic respiratory diseases are more susceptible to silicosis.
Which groups are commonly affected by silicosis?
Workers who are engaged in long-term mining, quarrying, tunnel operations, construction materials industries, as well as those working in quartz powder factories, glass factories, and ceramic factories are at high risk of developing silicosis if protective measures are inadequate.
DIAGNOSIS
What tests are needed to diagnose silicosis?
- Chest X-ray: Chest X-ray is the primary basis for diagnosing silicosis.
< - Laboratory tests: These serve as auxiliary tests to aid in confirming silicosis. In early-stage silicosis patients, routine blood and urine tests are often normal. In advanced stages, erythrocyte sedimentation rate may increase, while blood and urine silicon measurements show significant variability. Serum albumin decreases in silicosis patients, while globulin levels rise, particularly α-globulin and γ-globulin.
< - Pulmonary function tests: As the name suggests, pulmonary function tests examine lung function using instruments or chemical methods. These tests help determine the presence of lung lesions, their location, disease severity, and treatment efficacy. Early-stage silicosis patients without complications often show no significant changes in lung function.
< - Bronchoscopy: This allows direct observation of the trachea. During the procedure, bronchoalveolar lavage can be performed, and analysis of the lavage fluid can assist in diagnosing silicosis.
< - Lung biopsy: A lung tissue sample is obtained via puncture and examined for the presence of silicotic nodules. This is the gold standard for diagnosing silicosis.
What diseases should silicosis be differentiated from?
Early-stage silicosis may resemble acute miliary tuberculosis, pulmonary hemosiderosis, sarcoidosis, pulmonary alveolar microlithiasis, or bronchioloalveolar carcinoma. However, differentiation can be achieved by considering the patient's dust exposure history and conducting relevant tests.
TREATMENT
What are the treatment methods for silicosis?
There is currently no cure for silicosis. General treatments include:
- Avoiding silica-exposed work environments, ensuring adequate rest, improving nutrition, engaging in moderate exercise, and preventing respiratory infections, especially in winter and spring.
< - Actively preventing, detecting, and treating complications, particularly tuberculosis.
< - Do not believe in rumors, folk remedies, or foods claiming to "cleanse the lungs." Maintain a balanced diet.
< - Medications can alleviate symptoms and slow disease progression, including Polyvinylpyridine-N-Oxide (PVNO), aluminum citrate, tetrandrine, hydroxy piperaquine, and piperaquine phosphate.
< - Lung lavage.
< - Lung transplantation.
How is lung lavage used to treat silicosis?
Lung lavage involves separating the lungs via tubing, using a ventilator to assist one lung with oxygen supply while flushing the other lung with saline. This removes dust, inflammatory cells, and other harmful factors, significantly improving symptoms, lung function, disease progression, and quality of life.
Can all silicosis patients undergo lung lavage?
Lung lavage has strict eligibility criteria. Patients who cannot undergo it include:
- Elderly individuals with age-related conditions;
- Those with active tuberculosis;
- Patients with subpleural bullae larger than 2 cm (risk of pneumothorax or hydrothorax during lavage);
- Severely impaired lung function;
- Severe tracheal or bronchial deformities;
- Major organ dysfunction (heart, brain, liver, kidneys);
- Coagulation disorders;
- Malignancy or immunodeficiency.
What is lung transplantation for silicosis?
Lung transplantation replaces damaged lungs with healthy donor lungs to restore function. Like other organ transplants, it faces challenges such as donor shortages, high recipient mortality, and chronic rejection.
Who is eligible for lung transplantation in silicosis?
Patients at any stage of silicosis may qualify. Early transplantation while in good general health improves success rates and outcomes.
When is lung transplantation contraindicated for silicosis?
Absolute contraindications:
- Malignancy within 2 years (except squamous/basal cell skin cancers);
< - Untreatable major organ (heart, liver, kidney) disease;
< - Incurable infections (e.g., active hepatitis B, HIV);
< - Chest or spinal deformities;
< - Psychiatric conditions hindering treatment compliance.
Relative contraindications:
- Advanced age (recommended cutoff: 65 years);
< - Critical illness requiring mechanical ventilation;
< - Highly pathogenic infections;
< - Severe obesity or osteoporosis.
What are the benefits of lung transplantation for silicosis?
Despite risks like rejection, successful transplantation allows patients to live and work normally. Decisions should be made at specialized centers based on individual assessments.
Can silicosis be cured?
Lung damage from silicosis is irreversible. Early detection and treatment can normalize lifespan (excluding heavy labor), but full recovery requires transplantation. Acute silicosis has poor prognosis; chronic cases progress even after dust exposure ends. Common fatal complications include tuberculosis (34.5% of deaths), cor pulmonale, infections, emphysema, and pneumothorax. Cardiovascular disease accounts for 16.51% of deaths.
DIET & LIFESTYLE
What should silicosis patients pay attention to in daily life?
- Pay attention to nutritional supplementation, eat more vegetables, fruits, lean meat, and eggs. Avoid overly greasy or spicy foods, and refrain from consuming items that irritate the stomach or are difficult to digest;
< - Keep the patient's respiratory tract clear, promptly remove secretions or foreign objects from the mouth and trachea, and perform sputum drainage care. If there is excessive phlegm, family members can pat the patient's back to help expel it. For patients with overly thick and difficult-to-expel phlegm, nebulization therapy can be administered at the hospital to dilute the sputum;
< - Administer oxygen therapy when experiencing difficulty breathing. Additionally, pay attention to the patient's sleeping posture—if lying flat is unsuitable, adopt a side-lying or semi-reclined position;
< - Prevent reinfection. Silicosis patients have weakened respiratory defenses and low immunity, making them prone to infections. Keep warm, maintain indoor ventilation, and avoid crowded places. If an infection is detected, seek early treatment and use antibiotics appropriately;
< - Engage in moderate physical exercise, avoiding overly intense activities;
< - Silicosis patients must refrain from smoking, as it can worsen coughing and phlegm symptoms and exacerbate lung damage.
PREVENTION
How to prevent silicosis?
- Wear protective masks, protective face shields, protective clothing, etc., while working,
< - Wash promptly after working in a dusty environment.
< - Strengthen physical exercise, balance work and rest, maintain a nutritious diet, and improve your own resistance.
< - Undergo regular health check-ups, especially chest X-rays, to detect the condition early.
< - Patients with pre-existing lung diseases should not engage in jobs involving dust exposure.