The Air Quality Health Index and Emergency Department Visits for Otitis Media.

Otitis media (OM) is one of the most common diseases of young children, associated with substantial healthcare utilization and potential long-term consequences. OM is characterized by inflammation of the middle ear linked to anatomic, genetic, infectious, and environmental factors (Coticchia, Chen, Sachdeva, & Mutchnick, 2013; Lack, Caulfield, & Penagos, 2011). Environmental and behavioral factors that increase the risk for OM include exposure to tobacco smoke, bottle-feeding (as opposed to breast-feeding), daycare attendance, and specific outdoor pollutants (Ladomenou, Kafatos, Tselentis, & Galanakis, 2010; Zemek, Szyszkowicz, & Rowe, 2010). There is mixed evidence that allergies are linked to OM (Lack et al., 2011). There is a paucity of both evidence and statistical modeling methods on the relationship of ambient multipollutant exposure and childhood OM.Otitis Media and Outdoor Air PollutionBroadly, OM includes a continuum of conditions of inflammation of the middle ear from acute OM (AOM) to OM with effusion (OME) and chronic suppurative OM (CSOM). Globally, there are an estimated 709 million cases of AOM each year, with a high incidence rate for toddlers and preschool children (ages 1-4 years) of 61 per 100, and infants (less than 1 year) of 45 per 100 (Monasta et al., 2012). Up to 80% of children experience at least one episode of OME (Qureishi, Lee, Belfield, Birchall, & Daniel, 2014). Of the estimated 31 million cases of CSOM, over one fourth occur in children less than 5 years old. A common reason for a healthcare visit, OM accounts for at least one annual ambulatory care visit for every four children in the United States, with the greatest proportion of these visits composed of infants and toddlers (National Institute on Deafness and Other Communication Disorders, 2012). One of the most common complications from OM, particularly CSOM, is hearing loss.Because of anatomically smaller, shorter, and more horizontally aligned Eustachian tubes, small children are more at risk for OM (Coticchia et al., 2013). The Eustachian tube connects the middle ear to the nasal passage and is lined with cells that provide a mucociliary transport system to eliminate potential infectious and inflammatory agents from the middle ear. The Eustachian tube is essential for drainage of middle ear fluid, prevention of backward flow from the nasopharynx to the middle ear, and allowing air exchange and pressure balance. When infectious (particularly viral), allergic, or other irritants trigger inflammation in the nasal mucosa, the opening of the Eustachian tube may become narrowed or blocked, leading to fluid stasis in the middle ear. This fluid stasis leads to inflammation, and an environment for the proliferation of bacterial pathogens such as Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis commonly seen in AOM. AOM, OME, and CSOM are linked to Eustachian tube dysfunction. Generally, AOM demonstrates a consistent temporal relationship with viral upper respiratory infections, peaking 3 to 4 days after the onset of nasal and upper respiratory infection symptoms. CSOM and OME are closely linked to AOM. Theorized to be associated with chronic bacterial biofilm colonies in the middle ear, the chronic inflammatory middle ear conditions frequently follow or precede AOM, but may be tied to inflammation from allergic causes (Qureishi et al., 2014).Poor indoor and outdoor air quality is associated with an increased risk for OM. Exposure to second-hand smoke increases the amount of pathogens present in the nasopharynx (Brook, 2010; Fuentes-Leonarte et al., 2015). Exposing human middle ear epithelial cells to diesel exhaust particles and acrolein induces an inflammatory response and decreases the cell's viability, indicating a direct cellular link between air pollution and OM (Song, Lee, Lee, Chae, & Park, 2012, 2013). In human studies of outdoor air pollution, an increased risk for OM has been linked to combinations of persistent organic pollutants, increased levels of carbon monoxide, fine particulate matter (PM2. …