Exposure to urban air pollution and emergency department visits for diseases of the ear and mastoid processes

Exposure to ambient air pollutants may cause adverse health effects. This study sought to assess the association of five major air pollutants concentration levels and number of Emergency Department (ED) visits for ear and mastoid pathology in the large Canadian urban city, Toronto. A time-stratified case-crossover study design was used for the period between April 1, 2004 and December 31, 2015. Daily air pollution data were collected from the National Air Pollution Surveillance Database for carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ground-level ozone (O3) and fine particulate matter (PM2.5). Data were also collected for weather variables. ED visit data were extracted from the National Ambulatory Care Reporting System database. Conditional Poisson models were applied using daily counts of the ED visits. Temperature and relative humidity in the models were represented by natural splines. Independent variables (air pollutants and weather conditions) were lagged by the same number of exposure days, from 0 to 14. The analyses were grouped by strata according to patients’ sex and age, also by seasons. For each studied pollutant, 270 models were derived (15 lags × 18 strata). There were 188,997 ED visits during the 140-month study period. Children under 10 years represented 31.7% of all visits, compared to 53.8% for patients aged 11–60 years, and 14.5% for those above 60 years. Short-term (time lags 4 and 5 days) NO2 exposure was positively associated with number of ED visits for ear and mastoid pathology for children independent of sex. Boys had relative risks (RR) of 1.030 (95% confidence intervals: 1.009–1.053) and 1.033 (1.011–1.055) for ED visits on days 4 and 5 after exposure to NO2 by one interquartile range (IQR = 8.8 ppb), respectively. Girls had RR of 1.046 (1.021–1.071) and 1.039 (1.014–1.064) on days 4 and 5 after exposure to NO2 by the same IQR, respectively. For lag 4, a one unit increase in the calculated air quality health index results in a 1.038 (1.020–1.057), 1.042 (1.017–1.067), and 1.036 (1.014–1.058), for all children, girls, and boys, respectively. In this large urban cohort, number of ED visits for ear and/or mastoid process infections peaked in the acute period following elevated overall air pollution and NO2 specifically, especially among young children.