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 severely irritate the lungs (see Overview of Environmental Lung Diseases).
Gases such as chlorine and ammonia easily dissolve and immediately irritate the mouth, nose, and throat. The more peripheral parts of the lungs are affected only when the gas is inhaled deeply. A common household exposure occurs when a person mixes household ammonia with cleansers containing bleach. The irritant gas chloramine is released.
Some gases—for instance, nitrogen dioxide—do not dissolve easily. Therefore, they do not produce early warning signs of exposure, such as irritation of the nose and eyes, and they are 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).
Silo filler's disease (which mostly affects farmers) results from inhaling fumes that contain nitrogen dioxide given off by moist silage, such as fresh corn or grains. Fluid may develop in the lungs as late as 12 hours after exposure. The condition may temporarily resolve and then recur 10 to 14 days later, even without further contact with the gas. A recurrence tends to affect the small airways (bronchioles).
Inhalation of some gases and chemicals may also trigger an allergic response that leads to inflammation and, in some cases, scarring in and around the tiny air sacs (alveoli) and bronchioles of the lung. This condition is called hypersensitivity pneumonitis (see Hypersensitivity Pneumonitis).
Radioactive gases, which may be released in a nuclear reactor accident, may cause lung and other cancers many years after the exposure.
Other inhaled gases may cause a general body poisoning (including breathing difficulty) because they are poisonous to the body's cells (such as cyanide) or because they displace oxygen in the blood and therefore limit the amount of blood reaching the tissues (such as methane or carbon dioxide).
In some people, inhalation of small amounts of gas or other chemicals over a long period may result in chronic bronchitis. Also, inhalation of some chemicals, such as arsenic compounds and hydrocarbons, can cause cancer. Cancer may develop in the lungs or elsewhere in the body, depending on the substance inhaled.
Soluble gases such as chlorine, ammonia, and hydrofluoric acid cause severe burning in the eyes, nose, throat, windpipe, and large airways within minutes of exposure to them. In addition, 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 and ozone cause shortness of breath, which may be severe, after a delay of 3 to 4 hours and sometimes up to 12 hours after exposure. With less soluble gases, long-term lung damage can occur and cause chronic wheezing and shortness of breath.
A chest x-ray can show whether pulmonary edema or bronchiolitis has developed. Computed tomography is especially helpful when people have symptoms but their chest x-ray looks normal.
A sensor is attached to the person's finger to determine the amount of oxygen in the blood (pulse oximetry).
Tests of lung function, including determining how much air the lungs can hold and the rate at which oxygen and carbon dioxide are exchanged, are done to evaluate lung damage.
Most people recover completely from accidental exposure to gases. The most serious complications are lung infection or severe damage that causes scarring of the small airways (bronchiolitis obliterans). Some studies have shown long-term impairment of the lung function years after episodes of exposure to gases.
The best way to prevent exposure is to use extreme care when handling gases and chemicals. People using cleaning products or other chemicals at home should work in well-ventilated areas.
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, even fatal. People should not enter an environment where poisonous gases may be present to rescue an exposed person unless they have protective gear.
Oxygen is the mainstay of treatment for people who are exposed to gases. If lung damage is severe, a person may need mechanical ventilation (see Mechanical Ventilation). But any person who has breathing problems after inhaling a gas is usually monitored in a hospital overnight to ensure that serious complications do not occur. Drugs that open the airways (bronchodilators), intravenous fluids, and antibiotics may be helpful. Corticosteroids such as prednisone are often given to reduce inflammation in the lungs.
Last full review/revision January 2015 by Lee S. Newman, MD, MA