In 2006, elementary schools of inner-city Lisbon, Portugal were given questionnaires to identify respiratory problems. In
1,175 children aged 5–10 years, 27.7% reported rhinitis, 2.5% reported hay fever and 25.9% reported asthma symptoms. April
and August were the months with higher incidence of rhinitis, with a considerable difference nonetheless (10.5% and 2.3%,
respectively.). The former trends are addressed here by using meteorological data, PM2.5, and its elemental speciation. Mann-Whitney U-tests were applied to the data sets. Significantly higher values were found for humidity, K+, NH4+, Sb and Zn in April, and for temperature, Cl−, Mg2+ and Na+ in August. Commuter and heavy-duty traffic may contribute to rhinitis episodes.