What is a common cause of bronchitis?

Bronchitis is most commonly associated with respiratory infections and long-term exposure to irritants. Respiratory infections, particularly viral infections, are frequent precursors to bronchitis, leading to inflammation and irritation of the bronchial tubes. Additionally, prolonged exposure to irritants such as tobacco smoke, air pollution, or chemical fumes can significantly contribute to the development of chronic bronchitis.

Whereas bacterial infections may play a role in some instances, they are not the primary or most common cause. Excessive exercise typically does not lead to bronchitis, and cold air exposure, while it may exacerbate symptoms or trigger airway constriction in some individuals (especially those with pre-existing conditions), is not a direct cause of bronchitis itself. Thus, the combination of viral respiratory infections and long-term irritants clearly establishes the primary cause of bronchitis, making it the correct choice.