Risk factors

Occupations or hobbies

Some occupations and hobbies carry higher risks of pneumonitis, including:

• Farming. Many types of farming operations expose workers to aerosolized mists and pesticides. Inhaling airborne particles from moldy hay is one of the most common causes of occupational pneumonitis. Mold particles also can be inhaled during harvests of grain and hay.
• Bird handling. Poultry workers and people who breed or keep pigeons are often exposed to droppings, feathers and other materials that can cause pneumonitis.
• Hot tubs and humidifiers. Moldy conditions in hot tubs can trigger pneumonitis because the bubbling action makes a mist that can be inhaled. Home humidifiers are another common reservoir for mold.

Cancer treatment

Some chemotherapy drugs can cause pneumonitis, as can radiation therapy to the lungs. The combination of the two increases the risk of irreversible lung disease.