Lung diseases due to gas or chemical exposure are conditions that can be acquired from indoor and outdoor air pollution and from ingesting tobacco smoke.
Description
The lungs are susceptible to many airborne poisons and irritants. Mucus present in the airways blocks foreign particles of a certain size, however it is unable to filter all airborne particulates. There are hundreds of substances that can pollute air and harm lungs. Harmful gases and chemicals are just one type of airborne pollutant that can adversely effect the lungs. They include:
outdoor pollutants caused by industry and intensified by weather conditions
household heating, such as wood-burning stoves
household chemical products
tobacco smoke
Lungs respond to irritants in four ways, each of which can occur separately or, more often, trigger other responses.
Asthma occurs when irritation causes the smooth muscles surrounding the airways to constrict.
Increased mucus comes from irritated mucus glands lining the airway. Excess mucus clogs the airway and prevents air from circulating.
Constriction of the lungs results from scarring when the supporting tissues are damaged.
Cancer is caused by certain irritants, like asbestos and tobacco smoke.
The major categories that airborne irritants fall into are allergic, organic, inorganic, and poisonous, with many agents occupying more than one category.
Allergic irritants bother only people who are sensitive to them. Cat hair, insect parts, and pollen are common allergens. Chemicals called sulfites, which are widely used as food preservatives, also cause asthma.
There are many organic dusts that irritate the lungs. Most of them occur on the job and cause occupational lung disease. Grain dust causes silo filler's disease. Cotton and other textile dusts cause byssinosis. Mold spores in hay cause farmer's lung.
Inorganic dusts and aerosolized chemicals are also found mostly on the job. Classic among them are asbestos and coal dust. Many metals (cadmium, arsenic, chromium, and phosphorus), various other fine particles (cement, mica, rock), acid fumes, ammonia, ozone, and automobile and industrial emissions are part of a very long list.
Most intentional poisons (cyanide, nerve gas) that enter through the lungs pass through and damage other parts of the body. Mustard gas, used during World War I and banned since, directly and immediately destroys lungs.
Lung disease generates three major symptoms—coughing, wheezing, and shortness of breath. It also predisposes the lungs to infections such as bronchitis and pneumonia. Cancer is a late effect, requiring prolonged exposure to an irritant. In the case of tobacco, an average of a pack of cigarettes a day for forty years, or two packs a day for twenty years, will greatly increase the risk of lung cancer.
Diagnosis
A history of exposure combined with a chest x ray and lung function studies completes the diagnostic evaluation in most cases. Lung function measures the amount of air breathed in and out, the speed it moves, and the effectiveness of oxygen exchange with the blood. If the cause is still unclear, a lung biopsy reveals the answer.
Treatment
Eliminating the offending irritant and early antibiotics for infection are primary. There are many techniques available to remove excess mucus from the lungs. Respiratory therapists are experts in these methods. Finally, there are several machines available to enrich the oxygen content of breathed air.
A new surgical treatment called "lung reduction surgery" is just emerging from the experimental stage. It promises substantial return of lung function for selected patients with advanced emphysema.
Prognosis
Many of these diseases are progressive, because the irritants stay in the lungs forever. Others remain stable after the offensive agents are removed from the environment. Lungs do not heal from destructive damage, but they can clean out infection and excess mucus, and function better.
Prevention
Industrial air filters, adequate ventilation, and respirators in polluted work sites are now mandatory. Tobacco smoke is the world's leading cause of lung disease and many other afflictions. Smoking cessation programs are widely available.
BOOKS
Beckett, William S., W. Morgan, and C. Keith. "Byssinosis and Respiratory Disease Caused by Vegetable Dusts." In Textbook of Pulmonary Diseases, ed. Gerald L. Baum, et al. Philadelphia: Lippincott-Raven, 1997.
Graham, David R. "Noxious Gases and Fumes." In Textbook of Pulmonary Diseases, ed. Gerald L. Baum, et al. Philadelphia: Lippincott-Raven, 1997.
Kelley, Jason. "Occupational Lung Diseases Caused by Asbestos, Silica, and Other Silicates." In Textbook of Pulmonary Diseases, ed. Gerald L. Baum, et al. Philadelphia: Lippincott-Raven, 1997.
Looney, R. John, and Mark J. Utell. "Occupational Asthma and Industrial Bronchitis." In Textbook of Pulmonary Diseases, ed. Gerald L. Baum, et al. Philadelphia: Lippincott-Raven, 1997.
Morgan, W., and C. Keith. "Occupational Lung Diseases: Coal Workers' Beryllium, and Other Pneumoconioses." In Textbook of Pulmonary Diseases, ed. Gerald L. Baum, et al. Philadelphia: Lippincott-Raven, 1997.
PERIODICALS
Rogers, R. M., F. C. Sciurba, and R. J. Keenan. "Lung Reduction Surgery in Chronic Obstructive Lung Disease." Medical Clinics of North America 80 (May 1996): 623-44.
Sciurba, F. C., and R.M. Rogers. "Lung Reduction Surgery for Emphysema." Current Opinion In Pulmonary Medicine 2 (Mar. 1996): 97-103.
ORGANIZATIONS
American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872. <http://www.lungusa.org>.
J. Ricker Polsdorfer, MD
KEY TERMS
Allergen—A substance that causes an allergic reaction in those who are sensitive to it.
Asthma—Temporary airway narrowing that causes wheezing and shortness of breath due to allergies.
Bronchitis—Infection in the bronchi (breathing tubes).
Pneumonia—Infection or inflammation in the lung itself.
