Hypersensitivity Pneumonitis

Abstract

Chronic exposure to a broad array of antigens after workers inhale aerosolized organic dust particles from mold, animal dander, bird droppings, and chemicals, especially pesticides or herbicides, increases risk for hypersensitivity pneumonitis. Several demographic characteristics of immigrant workers in farming, poultry processing, construction, and landscaping increase this worker population’s risk.

Chronic exposure to a broad array of antigens less than 5 µm in size increases the risk of hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis (Zacharisen & Fink, 2011). These microscopic antigens reach the distal airways after workers inhale aerosolized organic dust particles from mold, animal dander, bird droppings, or chemicals, especially pesticides or herbicides. Individuals most at risk are those working in farming, poultry, and cattle industries; metalworking with synthetic fluids during high-speed machining processes; processing cheese, sausage, or flour; or brewing malt or soy sauce. Risk also increases during lumber milling; wood processing; construction; textile, clothing, plastics, or electronics manufacturing; or working with paints or other chemicals.

Frequency and intensity of antigen exposure have a greater effect on symptom presentation than the actual antigen. Workers experiencing a hypersensitivity reaction exhibit high fever, chills, body ache, nonproductive cough, chest tightness, dyspnea, and malaise usually within 4 to 6 hours of significant antigen exposure; symptoms generally resolve within 24 hours after removal of the antigen (Zacharisen & Fink, 2011). Misdiagnosis or inadequate treatment of acute HP may lead to the slowly developing chronic form, even without further exposure. Subacute HP can develop after continuous low-level antigen exposures over weeks or months with progressive cough, dyspnea on exertion, and nonspecific complaints of anorexia and malaise (Zacharisen & Fink, 2011). Chronic cough, dyspnea, fatigue, and weight loss may worsen long after exposure ends. Finger clubbing or pulmonary fibrosis may develop in severe chronic cases (National Heart, Lung, and Blood Institute, 2014).

No specific test or biomarker has been developed to confirm HP. Clinicians primarily diagnose HP based on compatible symptoms, history of antigen exposure, antibodies in serum or bronchoalveolar lavage fluid, or reproduction of symptoms and diagnostic abnormalities after repeated exposure (Zacharisen & Fink, 2011). Treatment includes removal of the antigen source and symptom management.

Several worker demographics increase risk for HP. Immigrant workers in farming, poultry processing, construction, and landscaping may be at risk for developing HP. Often these workers speak primarily Spanish, especially in the Southern and Southwestern United States. Workers with limited English proficiency have difficulty understanding verbal or written instructions about health risks or job hazards. Low educational levels, common among immigrants from Mexico and Central America, hamper workers’ comprehending verbal instructions and heeding warning labels on pesticides or other chemicals. Lack of awareness about airborne pollutants and potential antigens increases workers’ risks of exposures and may delay treatment.

Engineering controls that reduce antigen exposure are not always feasible, especially in agriculture and construction. Personal protective equipment (PPE), including dust masks and respirators, can prevent antigen exposure. Occupational and environmental health nurses can recognize at-risk workers and collaborate with local community partners and employers to educate supervisors and workers about appropriate PPE. Educational materials and instructions provided in a language and format that workers can understand may decrease antigen exposures and facilitate accurate diagnoses. Nurse educators can teach signs and symptoms of HP, its similarity to other illnesses, and the need for occupational and environmental histories in every patient encounter. A detailed history and workplace exposure assessment is the best way to identify at-risk workers.