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.
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 affect the lungs. They include:
Localized pollutants such as arsenic, asbestos, lead, and mercury
Outdoor pollutants caused by industry and intensified by weather conditions
Household heating, such as wood-burning stoves
Household chemical products
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, such as 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 also are 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.
While tobacco smoke is a culprit in many smokers, a 2003 report found that those who work in the tobacco industry experience higher incidence of lung disease from tobacco dust in their work environment.
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.
Tobacco use scars the lungs and causes emphysema and lung cancer.
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.
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 still is unclear, a lung biopsy aids diagnosis.
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 trained in these methods. Finally, there are several machines available to enrich the oxygen content of breathed air.
A surgical treatment called lung reduction volume surgery is emerging as a treatment for certain people over age 65 with severe emphysema. It promises substantial return of lung function for selected patients by cutting away diseased parts of the lungs so that healthy tissue functions better. In the fall of 2003, Medicare announced that it would begin paying for the surgery.
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.
Industrial air filters, adequate ventilation, and respirators in polluted work sites now are mandatory. Tobacco smoke is the world's leading cause of lung disease and many other afflictions. Smoking cessation programs are widely available.