Occupational Lung Diseases

Occupational lung diseases are caused by harmful particles, mists, vapors, or gases inhaled while a person works. Where in the airways or lungs an inhaled substance ends up and what type of lung disease develops depend on the size and kind of particles inhaled. Larger particles may get trapped in the nose or large airways, but the smallest ones reach the lungs. There, some particles dissolve and may be absorbed into the bloodstream; most solid particles that don't dis-solve are removed by the body's defenses.

The body has several means of getting rid of inhaled particles. In the airways, mucus coats particles so they can be coughed up more easily. In the lungs, special scavenger cells engulf most particles and render them harmless.

Different types of particles produce different reactions in the body. Some particles-plant pol-lens, for example can cause allergic reactions such as hay fever or a type of asthma. Particles such as coal dust, carbon, and tin oxide don't produce much of a reaction in the lungs. Other particles, such as quartz dust and asbestos, may cause permanent scarring of lung tissue (pulmonary fibrosis). In large enough quantities, certain particles, such as asbestos, can cause cancer in smokers.

Black Lung

Black lung (coal workers' pneumoconiosis) is a lung disease caused by deposits of coal dust in the lungs.

Black lung results from inhaling coal dust over a longtime. In simple black lung, coal dust collects around the small airways (bronchioles) of the lungs. Although coal dust is relatively inert and doesn't provoke much reaction, it spreads throughout the lungs and shows up as tiny spots on an X-ray. The coal dust doesn't block the air-ways. Nevertheless, every year 1 to 2 percent of the people with simple black lung develop a more serious form of the disease called progressive massive fibrosis, in which large areas of the lung (at least 1/2 inch in diameter) become scarred. Progressive massive fibrosis may worsen even after a person is no longer exposed to coal dust. Lung tissue and the blood vessels in the lungs can be destroyed by the scarring.

In Caplan's syndrome, a rare disorder that can affect coal miners who have rheumatoid arthritis, large round nodules of scarring develop quickly in the lung. Such nodules may form in people who have had significant exposure to coal dust, even if they don't have black lung.

Symptoms and Diagnosis

Simple black lung usually doesn't cause symptoms. However, many people with this disease cough and easily become short of breath because they also have emphysema (from cigarette smoking) or bronchitis (from cigarette smoking or toxic exposure to other industrial pollutants). The severe stages of progressive massive fibrosis, on the other hand, cause coughing and often disabling shortness of breath.

A doctor makes the diagnosis after noting char-acteristic spots on the chest X-ray of a person who has been exposed to coal dust for a long time - usually someone who has worked underground at least 10 years.

Prevention and Treatment

Black lung can be prevented by adequately sup-pressing coal dust at a work site. Coal workers should have chest x-rays every 4 to 5 years, so that the disease can be detected at an early stage. If the disease is detected, the worker should be transferred to an area where coal dust levels are low to prevent progressive massive fibrosis. Prevention is crucial because there's no cure for black lung. A person who can't breathe freely may benefit from the treatments used for chronic obstructive pulmonary disease, such as drug therapy to keep the airways open and free of secretions.

Asbestosis

Asbestosis is widespread scarring of lung tissue caused by breathing asbestos dust.

Asbestos is composed of fibrous mineral silicates of different chemical compositions. When inhaled, asbestos fibers settle deep in the lungs, causing scars. Asbestos inhalation also can cause the two layers of membrane covering the lungs (the pleura) to thicken.

People who work with asbestos are at risk of developing lung disease. Workers who demolish buildings that have insulation containing asbestos are also at risk, although the risk is small. The more a person is exposed to asbestos fibers, the greater the risk of developing an asbestos related disease.

Symptoms

Symptoms of asbestosis appear gradually only after many scars have formed and the lungs lose their elasticity. The first symptoms are a mild shortness of breath and decreased ability to exercise. Heavy smokers who have chronic bronchitis along with asbestosis may cough and wheeze. Gradually, breathing becomes more and more difficult. In about 15 percent of people with asbestosis, severe shortness of breath and respiratory failure develop.

Inhaling asbestos fibers can occasionally cause fluid to accumulate in the space between the two pleural layers, called the pleural space. Rarely, asbestos causes tumors in the pleura, called mesotheliomas, or in the membranes of the abdomen, called peritoneal mesotheliomas. The mesotheliomas caused by asbestos are cancerous and can't be cured. Mesotheliomas most commonly appear after exposure to crocidolite, one of four types of asbestos. Amosite, another type. also causes mesotheliomas. Chrysotile probably doesn't cause mesotheliomas, but sometimes it's contaminated with tremolite, which does cause them. Mesotheliomas usually develop 30 to 40 years after exposure.

Lung cancer is related in part to the level of exposure to asbestos fibers; however, among people with asbestosis, lung cancer develops almost exclusively in those who also smoke cigarettes. particularly those who smoke more than a pack a day.

Diagnosis

In a person who has a history of exposure to asbestos, a doctor sometimes can diagnose asbestosis with a chest x-ray that shows characteristic changes. Usually, the person also has abnormal lung function, and a doctor listening with a stethoscope placed over the lungs can hear abnormal sounds called crackles. To determine if a pleural tumor is cancerous, a doctor must perform a biopsy (remove a small piece of pleura and examine it under a microscope). Fluid around the lungs may be removed with a needle and analyzed (a procedure called thoracentesis); however, this procedure isn't usually as accurate as performing a biopsy.

Prevention and Treatment

Diseases caused by asbestos inhalation can be prevented by minimizing asbestos dust and fibers in the workplace. Because industries that use asbestos have improved dust control, fewer people develop asbestosis today, but mesotheliomas are still occurring in people who were exposed as much as 40 years ago. Asbestos in the home should be removed by workers trained in safe removal techniques. Smokers who have been in contact with asbestos can reduce their risk of lung cancer by giving up cigarettes.

Most treatments for asbestosis ease symptoms-for example, oxygen therapy relieves shortness of breath. Draining fluid from around the lungs also may make breathing easier. Occasionally, lung transplantation has been successful in treating asbestosis. Mesotheliomas are invariably fatal; chemotherapy doesn't work well, and surgical removal of the tumor doesn't cure the cancer.

Occupational Asthma

Occupational asthma is a reversible spasm of the airways caused by inhaling work related particles or vapors that act as irritants or cause an allergic reaction.

Many substances in the workplace can cause spasms of the airways, which make breathing difficult. Some people are particularly sensitive to airborne irritants.

Symptoms

Occupational asthma may cause shortness of breath, a tightness in the chest, wheezing, coughing, sneezing, runny nose, and watery eyes. For some people, wheezing at night is the only symptom.

Symptoms may develop during work hours but often don't start until a few hours after work. In some people, symptoms begin as much as 24 hours after exposure. Also, symptoms may come and go for a week or more after exposure. Thus, the link between the workplace and the symptoms is often obscured. Symptoms often become milder or disappear on weekends or over holidays. They worsen with repeated exposure.

Diagnosis

To make a diagnosis, a doctor asks the person about the symptoms and exposure to a substance known to cause asthma. Occasionally, the allergic reaction can be detected with a skin test (patch test), in which a small amount of a suspected sub-stance is placed on the skin. When making a diagnosis is more difficult, a doctor uses an inhalation challenge test, in which the person inhales small amounts of a suspected substance and is observed for wheezing and shortness of breath and tested for decreasing lung function.

Because the airways may begin to narrow be-fore symptoms appear, a person with delayed symptoms may use a device to monitor the airways while at work. This device, a portable peak flow meter, measures the speed at which a person can blow air out of the lungs. When the airways narrow, the rate slows markedly, suggesting occupational asthma.

Prevention and Treatment

Industries using substances that can cause asthma follow dust and vapor control measures, but eliminating the dusts and vapors may be impossible. Workers with severe asthma should change jobs, if possible. Continued exposure often leads to more severe and persistent asthma.

Treatments are the same as for other types of asthma. Drugs that open the airways (bronchodilators) may be given in an inhaler (for ex-ample, albuterol) or as a tablet (for example, theophylline). For severe attacks, corticosteroids (such as prednisone) may be taken by mouth for a short time. For longterm management, inhaled corticosteroids are preferred.

Byssinosis

Byssinosis is a narrowing of the airways caused by inhaling cotton, flax, or hemp particles.

In the United States and Great Britain, byssi-nosis occurs almost exclusively in people who work with unprocessed cotton. Those who work with flax and hemp may also develop the condition. People who open bales of raw cotton or who work in the first stages of cotton processing seem to be most affected. Apparently, something in the raw cotton causes the airways of susceptible people to narrow.

Symptoms and Diagnosis

Byssinosis may cause wheezing and tightness in the chest, usually on the first day of work after a break. Unlike with asthma, the symptoms tend to diminish after repeated exposure, and the chest tightness may disappear by the end of the workweek. However, after a person has worked with cotton for many years, the chest tightness may last for 2 or 3 workdays or even the whole Week. Prolonged exposure to cotton dust increases the frequency of wheezing but doesn't lead to permanent disabling lung disease.

The diagnosis is made by using a test that shows decreasing lung capacity over the course of a workday; usually, this decrease is greatest on the first day of the workweek.

Prevention and Treatment

Controlling dust is the best way to prevent bys-sinosis. Wheezing and chest tightness can be treated with the drugs used for asthma. Drugs that open the airways (bronchodilators) may be given in an inhaler (for example, albuterol) or as a tablet (for example, theophylline).

Gas and Chemical Exposure

Many types of gases - such as chlorine, phosgene, sulfur dioxide, hydrogen sulfide, nitrogen dioxide, and ammonia may suddenly be released during industrial accidents and may se-verely irritate the lungs. Gases such as chlorine and ammonia easily dissolve and immediately irritate the mouth, nose, and throat. The lower parts of the lungs are affected only when the gas is inhaled deeply. Radioactive gases, which may be released in a nuclear reactor accident, may cause lung and other cancers that take many years to develop.

Some gases-for instance, nitrogen dioxide - don't easily dissolve. Therefore, they don't produce early warning signs of exposure, such as irritation of the nose and eyes, and they're more likely to be inhaled deeply into the lungs. Such gases can cause inflammation of the small airways (bronchiolitis) or lead to fluid accumulation in the lungs (pulmonary edema). In silo filler's disease, which results from inhaling fumes that contain ni-trogen dioxide given off by moist silage, fluid may not develop in the lungs for up to 12 hours after exposure; the condition maytemporarily improve and then recur 10 to 14 days later, even without further contact with the gas. A recurrence tends to affect the small airways (bronchioles).

In some people, exposure to small amounts of gas or other chemicals over a long period may result in chronic bronchitis. Also, exposure to some chemicals, such as arsenic compounds and hydrocarbons, is thought to cause cancer in some people. Cancer may develop in the lungs or elsewhere in the body, depending on the substance inhaled.

Symptoms and Diagnosis

Soluble gases such as chlorine cause severe burning in the eyes, nose, throat, windpipe, and large airways. They often produce a cough and blood in the sputum (hemoptysis). Retching and shortness of breath also are common. Less soluble gases such as nitrogen dioxide produce shortness of breath, sometimes severe shortness of breath, after a delay of 3 to 4 hours.

A chest x-ray can show whether pulmonary edema or bronchiolitis has developed.

Prognosis, Prevention, and Treatment

Most people recover completely from accidental exposure to gases. The most serious complication is lung infection.

The best way to prevent exposure is to use extreme care when handling gases and chemicals. Gas masks with their own air supply should be available in case of accidental spillage. Farmers need to know that accidental exposure to toxic gases in silos is dangerous.

Oxygen is the mainstay of treatment. If lung damage is severe, a person may need mechanical ventilation. Drugs that open the airways, intravenous fluids, and antibiotics may be helpful. Corticosteroids such as prednisone are often prescribed to reduce inflammation in the lungs.

Benign Pneumoconioses

Other substances occasionally cause the lungs to appear abnormal on x-rays. Sid erosis results from inhalation of iron oxide, baritosis from inhalation of barium, and stannosis from inhalation of tin particles. Although these dusts are evident on a chest x-ray, they don't cause much of a reaction in the lung, so people exposed to them don't have any symptoms or functional impairment.

Courtesy By:
PROFESSOR G.L. SNIDER

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