Occupational asthma

Abstract

Occupational asthma (OA) is defined as “a disease characterized by variable airflow limitation and/or hyperresponsiveness and/or inflammation due to causes and conditions attributable to a particular occupational environment and not to stimuli encountered outside the workplace”. OA classically is characterized by a latency period during which time workers are exposed to either a high-molecular-weight (HMW) or low-molecular-weight (LMW) agent for a varying amount of time before becoming sensitized and subsequently developing asthma symptoms. HMW agents include plant or animal proteins larger than 1000 kD, which include natural rubber latex, enzymes, or laboratory animal allergens. LMW agents include chemicals smaller than 1000 kD that require conjugation with an endogenous protein (i.e., human serum albumin) to form a complete antigen capable of eliciting a specific immune response; they include isocyanates, acid anhydrides, and metallic salts. However, it is now well recognized that OA can occur in the absence of a latency period after a large exposure to an irritating or toxic material, resulting in airway hyperresponsiveness (AHR) and asthma within 24 h, referred to as reactive airways dysfunction syndrome (RADS) or irritant-induced asthma. The term work-exacerbated asthma has been recommended for patients with preexisting asthma that later develop worsening of asthma due to exposures in the workplace.