Personal exposure to particulate matter oxidative potential and airway inflammation: differences between asthmatic and non-asthmatic adults

We aimed to determine whether exposure to particulate matter PM, measured as the oxidative potential (OP) of filters collected from 24 h personal samplers, is associated with increased airway inflammation in asthmatic and non-asthmatic volunteers. Forty-two adult asthmatic patients (25 women and 17 men) and 37 matched controls wore a personal sampler for a day collecting fine (PM2.5) and coarse (PM10-2.5) particles, and determining 24 h afterwards their fractional exhaled nitric oxide (FeNO). The PM-OP was determined by two methods: dithiothreitol (DTT) and ascorbic acid (AA) being OP levels dichotomized based on the median, to calculate adjusted mean differences (aMDs) and odds ratios (aORs) with sex, age, study level, body mass index and interleukin-6 (IL-6) levels as confounders. Statistically significant associations between PM-OP and FeNO levels in non-asthmatic volunteers were observed: aMD for OP-DTT PM2.5 = 11.64 ppbs; 95 %CI (0.13-22.79); aMD for OP-AA PM10-2.5 = 15.67; 95 %CI (2.91-28.43) with aORs = 4.87 and 18.18 respectively. In asthmatic patients an association was also observed in the form of aORs, but of lower magnitude (1.91 and 1.94 respectively). Non-significant higher FeNO levels (aMD = 5.22) and an aOR = 3.92 were also observed in non-asthmatic volunteers for OP-AA in the fine fraction. As a conclusion, the effect of personal PM-OP on airway inflammation appears to be differential between asthmatic and non-asthmatic volunteers suggesting a potential implication of inhaled corticosteroids diminishing the reactivity of airway epithelium since adjusted associations were higher in volunteers without asthma.