ABSTRACT
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575 Occupational Asthmagens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 576 Mechanism of Immune Mediated Occupational Asthma . . . . . . . . . . . . . . . . . . . . 576 Diagnosis of Occupational Asthma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579 Personal Risk Factors Associated with the Development of Occupational Asthma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 Exposure Response Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 Socioeconomic Impact of Occupational Asthma . . . . . . . . . . . . . . . . . . . . . . . . . . 583 Management of Occupational Asthma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585
Asthma is a disease characterized by infl ammation in the airways, reversible airfl ow obstruction and bronchial hyper-reactivity. Occupational asthma (OA) is generally defi ned as asthma that has a causal relationship to exposures in the work environment. Various surveys estimate that 3 to 20% of adult onset asthma is related to work and that 4% of adult asthma is made worse by work [1-3]. Surveys conducted in Europe indicate that there are 12 to 170 new cases of OA/million workers/year. Numbers in the United States range from 29 to 710 cases/million workers/year [2]. An estimate of 200 to 300 agents has been causally associated with OA but only about 8 to 12 are responsible for the majority of OA cases reported globally [4]. OA can be associated with exposure to irritants or sensitizing substances that are categorized into high molecular weight (HMW) and low molecular weight (LMW) agents. The HMW agents are usually proteins while the LMW agents are chemicals, metals and drugs. Immune mediated mechanisms are associated with OA to the sensitizing substances since there is a latent period between exposure and onset of disease, there is memory, specifi city and in many cases demonstration of an immune response. OA can occur upon exposure to irritants via exacerbation of pre-existing asthma in a worker or induction of asthma. This chapter will focus on OA caused by exposure to HMW and LMW sensitizing agents, mediating their effect through immune mechanisms.
