By age three, 80 percent of children in North America have experienced a middle ear infection, or otitis media. Symptoms include ear discharge, pain, fever, vomiting and diarrhea. This condition is the number one reason for young children to visit their doctor. Consequently, otitis media has high health care costs and is thought to contribute to overconsumption of antibiotics. The identification of preventable risk factors will aid in reducing the incidence of this common childhood disease, and the associated costs to our health care system. Known risk factors for otitis media include recent respiratory infection, age, gender, race, season, non-initiation of breast feeding, familial history, daycare enrolment, and exposure to passive smoking. Outdoor air pollution has been hypothesized as a risk factor. Elaina MacIntyre is conducting the first study in North America to investigate whether exposure to air pollution from industrial, traffic and residential woodburning sources is linked to the incidence of otitis media in children under 2 years of age. She is examining the health records of 60,000 children in British Columbia born between 1999 and 2000 to see if episodes of increased residential air pollution correspond with increased rates of diagnosis for otitis media. If a link is found, Elaina will analyze the cost of cases attributable to air pollution.