Children are particularly vulnerable to airborne pollutants due to their immature lungs and immune system. Many studies have reported deleterious effects of exposure to ambient air pollution, in acute or chronic timeframe, on respiratory health in children.1 Airborne pollen are microscopic grains that are released from trees, grasses and weeds. Ample epidemiological evidence has suggested associations between high airborne pollen count and emergency hospital visits for allergies and asthma exacerbation in children.2

The interplay between air pollutants and pollen is well described in many experimental studies. Particulate matter and gaseous pollutants (eg, nitrogen dioxide (NO₂), ozone (O₃)) can increase allergen absorption into the lungs by binding to pollen grains, facilitate faster release of allergens, and/or modulate pollen allergenic potency.3 In epidemiological studies, while it is clear that both ambient air pollution and pollen have independent associations with poor respiratory health, their interactive effects are less certain.3 4 These mixed results, in fact, reflect the complexity in concentration, toxicity/allergenicity and seasonality of both air pollutants and pollen in diverse geographical settings. To date, most studies in this field were of time-series or case-crossover design, and focused primarily on asthma and respiratory symptoms.

To address this knowledge gap, in this issue of Thorax, Amazouz et al investigated whether recent exposure to both air pollution and pollen could affect levels of spirometric lung function and fractional exhaled nitric oxide (FeNO) among 1063 eight-year-old children from the …