Occupational Lung Disease

Toluene

Toluene diisocyanate (TDI) and related compounds are predominantly used in the production of polyurethanes and consumer products, such as coatings, elastomers, adhesives, certain paints, and sealants. Exposure to TDI is known to result in skin and lung sensitization among workers and has been documented to cause asthma, lung damage and, in severe cases, fatal reactions. However, the clinical manifestations are typically subacute to chronic in nature and are not associated with a particular odor (choice B is incorrect).

Cadmium

Cadmium poisoning has been reported from many parts of the world. It is a toxic metal that may affect multiple organs. Long-term exposure to cadmium through air, water, soil, and food leads to cancer and organ system toxicity involving skeletal, urinary, reproductive, cardiovascular, central and peripheral nerves, and the respiratory system. Possible involvement of cadmium in pulmonary diseases (such as chronic obstructive pulmonary disease and emphysema) has been reported, and animal studies have shown that cadmium chloride can decrease lung vital capacity and increase alveolar wall thickness. Inhalation of cadmium as a vapor in the absence of antioxidants and in the condition of oxidative stress may result in pulmonary inflammation and emphysema. These changes typically occur gradually and therefore are not consistent with the case presented (choice D is incorrect).

When to Suspect an Occupational Lung Disease

Occupational lung disease can affect any part of the respiratory tract, including sinuses, airways, the lung parenchyma, and the surrounding pleura. As a result, signs and symptoms associated with occupational exposure include rhinitis, reactive airways disease, COPD, pleural disease, diffuse parenchymal lung disease, and malignancy. Occupational lung diseases can present acutely, subacutely, or slowly after many years of exposure. As a result, these diseases require that clinicians maintain suspicion for and obtain a careful history of occupational exposures. Clinical presentations related to silica and asbestos exposures are well characterized and recognized. However, new agents that may lead to respiratory diseases are frequently introduced in industry. Factors suggesting an underlying occupational lung disease include patient concerns about an exposure, a temporal association with an exposure, unexplained signs or symptoms, and evidence of coworkers with similar symptoms (Table 17). In addition, patients may experience relief of symptoms when away from the work environment and recurrence of symptoms upon their return. For the patient with occupational lung disease, similar to diffuse parenchymal lung disease, cough and dyspnea on exertion are common.

Key Elements of the Exposure History

The time course from exposure to the development of signs and symptoms of occupational lung disease is highly variable. Therefore, it is essential to obtain a complete history, including employment history. Exposures within the same industry can vary based on use of best practices and on the type of workplace. For example, coal worker's pneumoconiosis in the United States has substantially decreased since the institution of federal safety standards. However, rates of coal worker's pneumoconiosis are higher for individuals who work for companies with fewer than 50 employees, and for those who work in thin-seam mines. Thin-seam mines appear to have higher crystalline silica exposure and pose greater risk. More than 95% of these mines are located in Kentucky, West Virginia, and Virginia. Adequate determination of exposure requires a clear description of job duties and determination of the extent of dust exposure. Clinicians should also obtain a history of additional exposures from hobbies or the home environment (see Table 17).

When an occupational lung disease is suspected, clinicians should request Material Safety Data Sheets (MSDSs) from the employer, which detail chemical properties and known health risks associated with substances within the workplace. The U.S. Occupational Safety and Health Administration (OSHA) requires that this information is available upon request for employees who work with potentially harmful materials.

For individuals who have undiagnosed disorders, persistent unexplained symptoms, or permanent impairment possibly due to an occupational lung disease, referral to an occupational and environmental lung disease specialist is appropriate.

Management

The key to management of occupational lung disease is removal of the offending agent from the workplace or the worker from the offending agent. Because workers typically have colleagues in a similar environment, further investigation of the workplace to ensure identification of all affected individuals is essential. Beyond one specific patient, prevention through mitigation of further exposures in the workplace is best practice.

Workers' compensation often becomes an issue during medical management. It may be difficult to define the degree of impairment resulting from the exposure, and the determination of disability related to the impairment may require referral to a specialist with expertise in occupational lung disease.

Surveillance

For individuals at high risk for the development of pulmonary disease, the use of health questionnaires and pulmonary function screening is appropriate; such screening can also identify a new exposure and any associated risk of disease development. Surveillance systems that catalogue sentinel cases of disease can help identify clustering of cases. However, one major limitation of these databases is the failure of physicians to report events.