Bronchitis in adults is caused by the viruses that often cause influenza and colds, according to Mayo Clinic. Adults who smoke cigarettes are also prone to the condition. Dust, toxic gases and air pollution in the environment can also cause bronchitis or promote symptoms of the illness.
Lung irritants and bacterial infections can cause an adult to develop bronchitis, explains the National Heart, Lung and Blood Institute. Individuals who are exposed to high levels of fumes or dust are also at risk for bronchitis. Adults can develop acute or chronic bronchitis, depending on the severity of the illness and the condition of the lungs.