According to the American Thoracic Society (ATS), the general diagnostic criteria for asbestosis are:

- Evidence of structural pathology consistent with asbestosis, as documented by imaging or histology

- Evidence of causation by asbestos as documented by the occupational and environmental history, markers of exposure (usually pleural plaques), recovery of asbestos bodies, or other means

- Exclusion of alternative plausible causes for the findings

The abnormal chest x-ray and its interpretation remain the most important factors in establishing the presence of pulmonary fibrosis. The findings usually appear as small, irregular parenchymal opacities, primarily in the lung bases. Using the ILO Classification system, "s", "t", and/or "u" opacities predominate. CT or high-resolution CT (HRCT) are more sensitive than plain radiography at detecting pulmonary fibrosis (as well as any underlying pleural changes). More than 50% of people affected with asbestosis develop plaques in the parietal pleura, the space between the chest wall and lungs. Once apparent, the radiographic findings in asbestosis may slowly progress or remain static, even in the absence of further asbestos exposure. Rapid progression suggests an alternative diagnosis.

Asbestosis resembles many other diffuse interstitial lung diseases, including other pneumoconiosis. The differential diagnosis includes idiopathic pulmonary fibrosis (IPF), hypersensitivity pneumonitis, sarcoidosis, and others. The presence of pleural plaquing may provide supportive evidence of causation by asbestos. Although lung biopsy is usually not necessary, the presence of asbestos bodies in association with pulmonary fibrosis establishes the diagnosis. Conversely, interstitial pulmonary fibrosis in the absence of asbestos bodies is most likely not asbestosis. Asbestos bodies in the absence of fibrosis indicate exposure, not disease.

Mesothelioma can be prevented in most cases by preventing exposure to asbestos. The US National Institute for Occupational Safety and Health maintains a recommended exposure limit of 0.1 asbestos fiber per cubic centimeter.

Asbestos can cause lung cancer that is identical to lung cancer from other causes. Exposure to asbestos is associated with all major histological types of lung carcinoma (adenocarcinoma, squamous cell carcinoma, large-cell carcinoma and small-cell carcinoma). The latency period between exposure and development of lung cancer is 20 to 30 years. It is estimated that 3%-8% of all lung cancers are related to asbestos. The risk of developing lung cancer depends on the level, duration, and frequency of asbestos exposure (cumulative exposure). Smoking and individual susceptibility are other contributing factors towards lung cancer. Smokers who have been exposed to asbestos are at far greater risk of lung cancer. Smoking and asbestos exposure have a multiplicative (synergistic) effect on the risk of lung cancer. Symptoms include chronic cough, chest pain, breathlessness, haemoptysis (coughing up blood), wheezing or hoarseness of the voice, weight loss and fatigue. Treatment involves surgical removal of the cancer, chemotherapy, radiotherapy, or a combination of these (multimodality treatment). Prognosis is generally poor unless the cancer is detected in its early stages. Out of all patients diagnosed with lung cancer, only 15% survive for five years after diagnosis.

There is no universally agreed protocol for screening people who have been exposed to asbestos. Screening tests might diagnose mesothelioma earlier than conventional methods thus improving the survival prospects for patients. The serum osteopontin level might be useful in screening asbestos-exposed people for mesothelioma. The level of soluble mesothelin-related protein is elevated in the serum of about 75% of patients at diagnosis and it has been suggested that it may be useful for screening. Doctors have begun testing the Mesomark assay which measures levels of soluble mesothelin-related proteins (SMRPs) released by mesothelioma cells.

Malignant mesothelioma is an aggressive and incurable tumour caused by asbestos arising from mesothelial cells of the pleura, peritoneum (the lining of the abdominal cavity) and rarely elsewhere. Pleural mesothelioma is the most common type of mesothelioma, representing about 75 percent of cases. Peritoneal mesothelioma is the second most common type, consisting of about 10 to 20 percent of cases. Mesothelioma appears from 20 to 50 years after the initial exposure to asbestos. The symptoms include shortness of breath, chronic chest pain, cough, and weight loss. Diagnosing mesothelioma is often difficult and can include physical examination, chest X-ray and lung function tests, followed by CT scan and MRI. A biopsy is needed to confirm a diagnosis of malignant mesothelioma. Mesothelioma has a poor prognosis, with most patients dying within 1 year of diagnosis. The treatment strategies include surgery, radiotherapy, chemotherapy or multimodality treatment. Several tumour biomarkers (soluble mesothelin-related protein (SMRP), osteopontin and fibulin3) have been evaluated for diagnostic purposes to allow early detection of this disease. Novel biomarkers such as volatile organic compounds measured in exhaled breath are also promising.

Bronchoalveolar lavage (BAL) is a well-tolerated diagnostic procedure in ILD. BAL cytology analyses (differential cell counts) should be considered in the evaluation of patients with IPF at the discretion of the treating physician based on availability and experience at their institution. BAL may reveal alternative specific diagnoses: malignancy, infections, eosinophilic pneumonia, histiocytosis X, or alveolar proteinosis. In the evaluation of patients with suspected IPF, the most important application of BAL is in the exclusion of other diagnoses. Prominent lymphocytosis (>30%) generally allows excluding a diagnosis of IPF.

According to the updated 2011 guidelines, in the absence of a typical UIP pattern on HRCT, a surgical lung biopsy is required for confident diagnosis.

Histologic specimens for the diagnosis of IPF must be taken at least in three different places and be large enough that the pathologist can comment on the underlying lung architecture. Small biopsies, such as those obtained via transbronchial lung biopsy (performed during bronchoscopy) are usually not sufficient for this purpose. Hence, larger biopsies obtained surgically via a thoracotomy or thoracoscopy are usually necessary.

Lung tissue from people with IPF usually show a characteristic histopathologic UIP pattern and is therefore the pathologic counterpart of IPF. Although a pathologic diagnosis of UIP often corresponds to a clinical diagnosis of IPF, a UIP histologic pattern can be seen in other diseases as well, and fibrosis of known origin (rheumatic diseases for example). There are four key features of UIP including interstitial fibrosis in a ‘patchwork pattern’, interstitial scarring, honeycomb changes and fibroblast foci.

Fibroblastic foci are dense collections of myofibroblasts and scar tissue and, together with honeycombing, are the main pathological findings that allow a diagnosis of UIP.

Positive indications on patient assessment:

- Shortness of breath

- Chest X-ray may show a characteristic patchy, subpleural, bibasilar interstitial infiltrates or small cystic radiolucencies called honeycombing.

Pneumoconiosis in combination with multiple pulmonary rheumatoid nodules in rheumatoid arthritis patients is known as Caplan's syndrome.

Respiratory disease is a common and significant cause of illness and death around the world. In the US, approximately 1 billion "common colds" occur each year. A study found that in 2010, there were approximately 6.8 million emergency department visits for respiratory disorders in the U.S. for patients under the age of 18. In 2012, respiratory conditions were the most frequent reasons for hospital stays among children.

In the UK, approximately 1 in 7 individuals are affected by some form of chronic lung disease, most commonly chronic obstructive pulmonary disease, which includes asthma, chronic bronchitis and emphysema.

Respiratory diseases (including lung cancer) are responsible for over 10% of hospitalizations and over 16% of deaths in Canada.

In 2011, respiratory disease with ventilator support accounted for 93.3% of ICU utilization in the United States.

There is no cure available for asbestosis. Oxygen therapy at home is often necessary to relieve the shortness of breath and correct underlying low blood oxygen levels. Supportive treatment of symptoms includes respiratory physiotherapy to remove secretions from the lungs by postural drainage, chest percussion, and vibration. Nebulized medications may be prescribed in order to loosen secretions or treat underlying chronic obstructive pulmonary disease. Immunization against pneumococcal pneumonia and annual influenza vaccination is administered due to increased sensitivity to the diseases. Those with asbestosis are at increased risk for certain cancers. If the person smokes, quitting the habit reduces further damage. Periodic pulmonary function tests, chest x-rays, and clinical evaluations, including cancer screening/evaluations, are given to detect additional hazards.

Respiratory diseases may be investigated by performing one or more of the following tests

- Biopsy of the lung or pleura

- Blood test

- Bronchoscopy

- Chest x-ray

- Computed tomography scan, including high-resolution computed tomography

- Culture of microorganisms from secretions such as sputum

- Ultrasound scanning can be useful to detect fluid such as pleural effusion

- Pulmonary function test

- Ventilation—perfusion scan

There are three key elements to the diagnosis of silicosis. First, the patient history should reveal exposure to sufficient silica dust to cause this illness. Second, chest imaging (usually chest x-ray) that reveals findings consistent with silicosis. Third, there are no underlying illnesses that are more likely to be causing the abnormalities. Physical examination is usually unremarkable unless there is complicated disease. Also, the examination findings are not specific for silicosis. Pulmonary function testing may reveal airflow limitation, restrictive defects, reduced diffusion capacity, mixed defects, or may be normal (especially without complicated disease). Most cases of silicosis do not require tissue biopsy for diagnosis, but this may be necessary in some cases, primarily to exclude other conditions.

For uncomplicated silicosis, chest x-ray will confirm the presence of small ( 1 cm) occurs from coalescence of small opacities, particularly in the upper lung zones. With retraction of the lung tissue, there is compensatory emphysema. Enlargement of the hilum is common with chronic and accelerated silicosis. In about 5–10% of cases, the nodes will calcify circumferentially, producing so-called "eggshell" calcification. This finding is not pathognomonic (diagnostic) of silicosis. In some cases, the pulmonary nodules may also become calcified.

A computed tomography or CT scan can also provide a mode detailed analysis of the lungs, and can reveal cavitation due to concomitant mycobacterial infection.

Ectopic endometrial tissue reaches the pleural space of the lung or the right hemi-diaphragmatic region and erodes the visceral pleura, causing the formation of a spontaneous pneumothorax. The condition is often cyclical, due to its associations with the beginning of the menstrual cycle.

Affected persons usually present with recurrent spontaneous pneumothorax associated with the onset of the menstrual cycle. Additionally, chest/scapular pain and/or evidence of endometriosis in the abdominopelvic cavity are other manifestations.

On radiological studies, pneumothorax is visualized using conventional chest x-rays and CT scans. In 90% of the cases, the pneumothorax is located on the right side. In some cases, small nodules can be seen in the pleura using CT scans. Confirmation can be done using video assisted thoracoscopic surgery (VATS).

Treatment for the pneumothorax is with chest tube placement. As for the ectopic endometrial tissue, therapy with gonadotropin-releasing–hormone or resection of the lesions can improve symptoms.

Following thoracoabdominal trauma, most commonly a penetrating injury, laceration of the diaphragm, and spleen allows ectopic splenic tissue to reach the pleural space of the lung.

Affected persons are usually asymptomatic. However, on rare occasions, thoracic splenosis can present with chest pain and/or hemoptysis.

On radiological studies, thoracic splenic lesions are visualized using CT scans. Visualized lesions can be described as solitary or multiple nodules. The locations of the lesions are mostly in the lower left pleural space and/or splenic bed. Confirmation can be done using scintigraphy with 99mTc tagged heat-damaged red blood cells.

No treatment is required since thoracic splenosis is a benign condition.

The best way to prevent silicosis is to identify work-place activities that produce respirable crystalline silica dust and then to eliminate or control the dust ("primary prevention"). Water spray is often used where dust emanates. Dust can also be controlled through dry air filtering.

Following observations on industry workers in Lucknow (India), experiments on rats found that jaggery (a traditional sugar) had a preventive action against silicosis.

Health care professionals are at risk of occupational influenza exposure; during a pandemic influenza, anyone in a close environment is at risk, including those in an office environment.

Once a pleural effusion is diagnosed, its cause must be determined. Pleural fluid is drawn out of the pleural space in a process called thoracentesis, and it should be done in almost all patients who have pleural fluid that is at least 10 mm in thickness on CT, ultrasonography, or lateral decubitus X-ray and that is new or of uncertain etiology. In general, the only patients who do not require thoracentesis are those who have heart failure with symmetric pleural effusions and no chest pain or fever; in these patients, diuresis can be tried, and thoracentesis is avoided unless effusions persist for more than 3 days. In a thoracentesis, a needle is inserted through the back of the chest wall in the sixth, seventh, or eighth intercostal space on the midaxillary line, into the pleural space. The use of ultrasound to guide the procedure is now standard of care as it increases accuracy and decreases complications. After removal, the fluid may then be evaluated for:

1. Chemical composition including protein, lactate dehydrogenase (LDH), albumin, amylase, pH, and glucose

2. Gram stain and culture to identify possible bacterial infections

3. White and red blood cell counts and differential white blood cell counts

4. Cytopathology to identify cancer cells, but may also identify some infective organisms

5. Other tests as suggested by the clinical situation – lipids, fungal culture, viral culture, tuberculosis cultures, lupus cell prep, specific immunoglobulins

A pleural effusion is usually diagnosed on the basis of medical history and physical exam, and confirmed by a chest X-ray. Once accumulated fluid is more than 300 mL, there are usually detectable clinical signs, such as decreased movement of the chest on the affected side, dullness to percussion over the fluid, diminished breath sounds on the affected side, decreased vocal resonance and fremitus (though this is an inconsistent and unreliable sign), and pleural friction rub. Above the effusion, where the lung is compressed, there may be bronchial breathing sounds and egophony. A large effusion there may cause tracheal deviation away from the effusion. A systematic review (2009) published as part of the Rational Clinical Examination Series in the Journal of the American Medical Association showed that dullness to conventional percussion was most accurate for diagnosing pleural effusion (summary positive likelihood ratio, 8.7; 95% confidence interval, 2.2–33.8), while the absence of reduced tactile vocal fremitus made pleural effusion less likely (negative likelihood ratio, 0.21; 95% confidence interval, 0.12–0.37).

Tuberculosis is a lung disease endemic in many parts of the world. Health care professionals and prison guards are at high risk for occupational exposure to tuberculosis, since they work with populations with high rates of the disease.

Cancer screening uses medical tests to detect disease in large groups of people who have no symptoms. For individuals with high risk of developing lung cancer, computed tomography (CT) screening can detect cancer and give a person options to respond to it in a way that prolongs life. This form of screening reduces the chance of death from lung cancer by an absolute amount of 0.3% (relative amount of 20%). High risk people are those age 55–74 who have smoked equivalent amount of a pack of cigarettes daily for 30 years including time within the past 15 years.

CT screening is associated with a high rate of falsely positive tests which may result in unneeded treatment. For each true positive scan there are about 19 falsely positives scans. Other concerns include radiation exposure and the cost of testing along with follow up. Research has not found two other available tests—sputum cytology or chest radiograph (CXR) screening tests—to have any benefit.

The United States Preventive Services Task Force (USPSTF) recommends yearly screening using low-dose computed tomography in those who have a total smoking history of 30 pack-years and are between 55 and 80 years old until a person has not been smoking for more than 15 years. Screening should not be done in those with other health problems that would make treatment of lung cancer if found not an option. The English National Health Service was in 2014 re-examining the evidence for screening.

Lung symptoms in a patient who is taking a medicinal drug that can cause pulmonary toxicity should not automatically lead to a diagnosis of "pulmonary toxicity due to the medicinal drug", because some patients can have another (i.e., simultaneous) lung disease, e.g. an infection of the lungs "not" related to the medicinal drugs the patient is taking. But if the patient is taking such a medicinal drug, this should not be overlooked. Diagnostic care should be executed. The correct diagnosis is an exclusion diagnosis and can require some tests.

Pneumoconiosis is an occupational lung disease and a restrictive lung disease caused by the inhalation of dust, often in mines and from agriculture.

In 2013, it resulted in 260,000 deaths, up from 251,000 deaths in 1990. Of these deaths, 46,000 were due to silicosis, 24,000 due to asbestosis and 25,000 due to coal workers pneumoconiosis.

Performing a chest radiograph is one of the first investigative steps if a person reports symptoms that may suggest lung cancer. This may reveal an obvious mass, widening of the mediastinum (suggestive of spread to lymph nodes there), atelectasis (collapse), consolidation (pneumonia) or pleural effusion. CT imaging is typically used to provide more information about the type and extent of disease. Bronchoscopy or CT-guided biopsy is often used to sample the tumor for histopathology.

Lung cancer often appears as a solitary pulmonary nodule on a chest radiograph. However, the differential diagnosis is wide. Many other diseases can also give this appearance, including metastatic cancer, hamartomas, and infectious granulomas such as tuberculosis, histoplasmosis and coccidioidomycosis. Lung cancer can also be an incidental finding, as a solitary pulmonary nodule on a chest radiograph or CT scan done for an unrelated reason. The definitive diagnosis of lung cancer is based on histological examination of the suspicious tissue in the context of the clinical and radiological features.

Clinical practice guidelines recommend frequencies for pulmonary nodule surveillance. CT imaging should not be used for longer or more frequently than indicated as extended surveillance exposes people to increased radiation.

In rounded atelectasis (Folded lung or Blesovsky syndrome), an outer portion of the lung slowly collapses as a result of scarring and shrinkage of the membrane layers covering the lungs (pleura), which would show as visceral pleural thickening and entrapment of lung tissue. This produces a rounded appearance on x-ray that doctors may mistake for a tumor. Rounded atelectasis is usually a complication of asbestos-induced disease of the pleura, but it may also result from other types of chronic scarring and thickening of the pleura.

Side effects on the lungs can be very varied, and can include signs and symptoms that are either clinical, or radiological (i.e., seen on chest X-ray or CT), or both. They can include lung inflammation (pneumonitis), secondary (in this context, indirectly caused) lung infection (pneumonia), lung fibrosis, organising pneumonia (bronchiolitis obliterans organising pneumonia, BOOP), ARDS (acute respiratory distress syndrome), solitary pulmonary mass (even including lung cancer in some cases, mainly in cases of asbestos-related lung disease, but today this is very rare, because asbestos is now completely prohibited by law in most countries), or pulmonary nodule. The diagnosis should be made by a specialist, if possible.