ABSTRACT
Asthma, chronic obstructive pulmonary disease (COPD), and asthma-COPD overlap syndrome or ACO are not well differentiated in the occupational literature. However, many occupational obstructive lung disease syndromes have a number of features that are suggestive of and meet the current clinical criteria for ACO. The workplace exposures causing occupational asthma and occupational COPD have been intensively investigated and reported, and it is likely that some of these exposures are also responsible for the development of ACO in a subset of susceptible workers. Further, exposures to combinations of particulates, gases, vapors, dusts, irritants, and allergens are known to cause ACO, and many such “mixed” exposures are found in the workplace. In addition, epidemiological studies implicate occupational exposures as risk factors for ACO. Indeed, the many phenotypes of ACO likely reflect the effects of differing exposures modulated by host characteristics. It is important to identify occupations and workplace exposures that are risk factors for ACO, as this not only establishes the etiologies of the disease, but may impact prognosis, recommendations for removal from exposure, and workers’ benefits. As an example, workers with ACO have been documented to experience the highest frequency of pulmonary symptoms, use more respiratory medications, develop more frequent respiratory exacerbations, are more likely to require hospitalization, and report worse quality of life 1 than those with either asthma or COPD alone. Similar to published work on other occupational lung diseases, removal from exposure may be necessary to prevent progression of disease. This makes identification of the source of exposure critical, and most importantly, provides the potential to reduce exposure for other workers, thereby preventing occurrences of future disease. In this chapter, the definition of ACO used is an obstructive airways disease with evidence of partial reversibility via inhaled bronchodilator, along with persistent airflow obstruction. Given the lack of studies that have examined occupational exposure risks specifically for ACO, studies that describe exposures associated with airflow obstruction and/or COPD will be included in this review, as it is likely that some such exposures may also cause ACO that was not considered as a specific outcome at the time. This chapter will review some of the epidemiological studies that identify specific occupations and exposures as risk factors for ACO, as well as general exposures quantified as vapors, dusts, gases, and fumes. We will then proceed to discuss specific workplace exposures with the best documentation for causing potential ACO. Finally, specific jobs and exposures with limited documentation, but nonetheless suggestive of causing ACO, will be examined.
