Current Respiratory Medicine Reviews - Volume 12, Issue 1, 2016

Infectious diseases transmitted at work are frequent globally. Lung infections due to exposure at work are mainly affecting two broad groups, health care workers (HCW) and people exposed occasionally to sick animals. The main challenge globally during the last decades has been tuberculosis (TB), different influenza strains and coronaviruses. TB is still a global threat infecting almost 9 mill people world-wide and causing 1, 4 mill deaths (2011). Influenza is common during winters in smaller epidemics, but has also caused serious pandemics (1918, 1957, 1968 and 2009). TB in miners is a major health problem in South-Africa. Avian influenza is caused by the influenza A strain in birds. Humans may acquire avian influenza by inhalations of droplets or by contact from infected material. Different avian strains have been shown to infect humans (H5N1, H7N7 and H9N2 strains). Swine influenza H1N1 (S-OIV) were reported from Mexico in 2009 with a further rapid spread to other countries and causing a pandemic. The syndrome of SARS caused by a coronavirus (SARS-CoV) was first described in Guangdong, China in 2002. The infection spread rapidly and 29 countries were affected in the first epidemic in 2002-3. In 2012 a novel coronavirus (MERS-CoV) related to SARS was described in a Saudi Arabian patient who died of pneumonia and multi-organ failure (Middle East Respiratory Syndrome - MERS). Other occupational respiratory infections are also encountered, among them legionella, psittacosis and Q-fever. Increased mortality of pneumonia in welders is a special problem, probably due to reduced resistance to infection because of welding fumes. Knowledge of disease transmission mechanisms is necessary for managing epidemics.

Occupational asthma (OA) has emerged as the commonest occupational lung disease in developed countries and the second commonest in developing countries. Nearly 9-15% of the global adult asthma is occupation associated. However, this is an underestimation as large proportion of occupational asthma remains unidentified in developing world. The economic burden of OA is enormous but the disease is potentially preventable. The western models of documenting and legislation implementation models have provided a scaffold to curb various occupation morbidities of the world. Many government and non-government bodies along pertinent political inclination have been instrumental in the risk factor identification and sensitizer dose assessment for OA in the developed countries, and also ensuring that patients are adequately treated and compensated by the employers, with execution of good ergonomic practices in work places. The characteristic of OA epidemiology in developing world is contrary to the poor diagnosis, inappropriate treatment and inadequate compensation, with lack of political will. This mandates necessity of learning from developed country occupational disease models context to understanding of OA, along with reliable and feasible diagnostics and interventions that will have the potential to minimize the health hazards from the exposures at workplace environments in developing countries.

In the morbidity structure of Russian adult population respiratory disorders are second only to circulatory system diseases. Point prevalence of respiratory diseases was registered at 38,945 per 100,000 people in 2013. 4% of all deaths annually in Russia are due to the respiratory pathology. Risk factors are numerous but principal among them are infections, workplace conditions, environmental pollution, behavioral patterns and socio-economic status. Occupational disease identification in Russia is based on combined efforts of 2 branches – physicians from departments or clinics of occupational diseases and governmental occupational hygienists. These two branches differ in educational background, as well as tasks performed, which could lead to hampered communication and interactions. Occupational respiratory diseases (ORD) are vastly underdiagnosed, with ORD incidence varying at 0.4–0.5 per 10,000 workers. Statistical reports show that while proportion of workers employed in hazardous and (or) dangerous working conditions increases, the rate of occupational diseases actually decreases, which can be explained by ineffective monitoring. Multidisciplinary occupational health services are strongly in need. COPD and chronic bronchitis are the most prevalent among the ORD followed by pneumoconioses, infection diseases, asthma, upper respiratory disorders and tumors. Pneumoconiosis morbidity tends to lower in recent years and severe silicosis cases are diagnosed rarely, although new types of the interstitial lung diseases have emerged, such as sarcoidosis and idiopathic fibrotic alveolitis. Hypersensitivity pneumonites are becoming more frequent as well. Among causative factors of occupational respiratory pathology in Russian population the most prevalent are aerosols, chemicals, biological hazards, and voice load.

Asbestos has been known for many years to cause a range of both non-malignant and malignant diseases. Over fifty countries have totally banned the use of asbestos, but in emerging economies there continues to be considerable use of asbestos. Unfortunately, the United States is one of the very few developed countries that has not banned the use of this material due to industry intransigence. With the continued use of asbestos because of the lack of a worldwide ban there can be expected to be disease well into the future, for at least fifty more years, due to the long latency period for disease development. Stopping the use of asbestos has been shown to decrease the incidence, as seen in Sweden, of disease and is clearly the recommended path forward.

Hypersensitivity pneumonitis is a form of interstitial lung disease caused by a wide array of respirable particles. Given the widespread prevalence of many implicated exposures, contributing factors such as genetic predisposition and concomitant environmental factors likely influence the risk of disease development. Common causes include a range of bacterial and fungal species, and a number of chemical exposures such as to isocyanates. Exposures to microbial contaminants can occur in a range of domestic, recreational and occupational settings. Occupational exposures to microbial contamination include and are not limited to the farming industry, the manufacturing industry which frequently requires the use of metalworking fluids, and the food industry. Diagnostic assessment initially relies on a high index of clinical suspicion. Subsequent workup integrates clinical history, pulmonary function testing and radiologic imaging with a high resolution chest CT scan. In certain clinical scenarios, serological testing, bronchoscopy with bronchoalveolar lavage and/or surgical lung biopsy may be informative.

In industrialized countries, inhalational exposure to various industrial chemicals is commonplace, with acute lung injury from industrial chemicals increasing in parallel to industrialization. Most acute toxic inhalation, both in industrial and home settings, is due directly to leaks or spills or indirectly to reaction products such as nitrogen dioxide and phosgene. Acute pulmonary parenchymal injuries range from mild pneumonitis to acute respiratory distress syndrome (ARDS). The main factors that determine the severity of injury after inhalation of irritant gases are their water solubility and exposure levels. Water soluble irritants (e.g., ammonia and sulfur dioxide) generally result in upper airway injury, whereas water-insoluble irritants such as phosgene and nitrogen dioxide may cause damage to lower airways and alveoli. Cadmium and mercury can also cause acute lung injury. This review describes the industrial chemicals primarily responsible for acute lung injuries, and their clinical manifestations and exposure scenarios.

Silicosis is one of the oldest occupational diseases known to man. It is an irreversible fibrotic lung disease caused by inhalation of crystalline silicon dioxide or silica. In spite of optimal regulation in the developed countries, exposure to respirable crystalline silica dust is still a major occupational health problem however the scenario is far more adverse in the industrially developing countries. The USA, Europe, China and India are listed in the top among the countries where the prevalence of silicosis is still extremely high and approximately more than 5 million people are exposed to respirable silica dust globally however the number is still too low because of almost parallel numbers of undiagnosed cases. Silica induces a series of inflammatory reactions that further trigger a chronic or acute fibrotic change in the lungs. Silicosis is often followed by other comorbidities among which tuberculosis, chronic obstructive pulmonary disease (COPD) and cancer are most prevalent. As of now, there is no curative treatment however inclusive management strategies may help to recover quality of life and slow deterioration. Regular medical examinations should be available to all workers who may be exposed to crystalline silica. Further efforts are needed for recognition and control of silica hazards, especially in developing countries.

Coal is the second largest source of energy worldwide. As global energy demands continue to rise, coal will remain an important fuel source for years to come. Coal mine dust lung disease (CMDLD) describes the spectrum of respiratory diseases caused by coal mine dust and includes coal workers’ pneumoconiosis (CWP), mixed-dust pneumoconiosis, chronic obstructive pulmonary disease (COPD), and diffuse dust-related fibrosis (DDF). Estimates of the worldwide prevalence of CMDLD are unknown due to the lack of reliable information. It is recognized that the prevalence is greater in developing countries where working conditions are not well regulated. Strictly enforced dust control limits in the developed world have resulted in a declining prevalence of CMDLD. However, some countries have seen resurgence in both the prevalence and severity of CMDLD in the last 15 years. There is no cure for CMDLD, and it can progress even after exposure has ceased. Primary prevention of CMDLD, mainly through engineering controls to limit the presence of respirable dust, is therefore of critical importance. These methods include dust suppression techniques and ventilation plans. Unbiased dust sampling programs are needed to evaluate the effectiveness of these controls. Personal protective equipment provides inadequate protection due to difficulty with continuous use. Early detection of CMDLD using well-designed medical surveillance screening programs for coal miners is recommended. These programs should include chest imaging, spirometry, and clinical questionnaires. Detection of early disease allows for medical workplace removal as well as evaluation and implementation of improved environmental safety controls that can protect the respiratory health of all miners.

Lung cancer, a disease traditionally attributed to the effects of carcinogens from inhaled tobacco smoke, is now recognised in a population with either a relatively light history of smoking, or never smoking. Although second hand smoke contributes to the risk of neoplasia, the extent to which this affects different individuals varies, and probably depends on a combination of genetic, environmental, and racial factors. In addition, there are known associations of lung cancer in never-smokers with different occupational factors, such as asbestos, as well as potential risks due to naturally occurring diseases, and lifestyle factors. In recent years, targeted molecular therapies of non-small-cell lung cancer have enabled prolonged disease-free-survival times. These are based on the detection of activating mutations or translocations of genes coding for receptor tyrosine kinases, such as EGFR and ALK. They are reported usually in adenocarcinomas, and are often diagnosed in never smoking individuals or light smokers. This has supported the evolving concept of lung cancer in never-smokers as a molecularly different subtype, with its own associated clinical characteristics and histopathological features. Furthermore, genome-wide association studies have suggested that there are genetic polymorphisms, conferring an increased risk of lung cancer, which have a greater impact on the risk in never-smokers compared to smokers. This review considers the different factors that may lead to lung cancer in those considered never-smokers and, where possible, examines these in the context of relevant genetic findings.