Table 5 Associations between incident wheezing symptoms for 3-day mean concentrations (lag 2–4) of air pollutants in infants (age 0–1 years) in period with available UFPNC measurements (15 May 2001 to 19 December 2004)
One-pollutant modelTwo-pollutant modelTwo-pollutant modelTwo-pollutant modelTwo-pollutant model
OR* (95% CI)OR (95% CI)OR (95% CI)OR (95% CI)OR (95% CI)
n†144144144144144
UFPNC§ (particles/m3)1.92 (0.98 to 3.76)1.86 (0.88 to 4.14)1.82 (0.62 to 5.34)2.04 (0.68 to 6.16)1.67 (0.69 to 4.02)
PM10 (μg/m3)2.05 (1.26 to 3.32)‡1.76 (1.12 to 2.76)‡
NO2 (ppb)2.15 (1.02 to 4.57)‡1.47 (0.53 to 4.06)
NOx (ppb)1.73 (0.94 to 3.22)1.18 (0.50 to 2.78)
CO (ppm)2.17 (1.01 to 4.66)‡1.44 (0.51 to 4.06)

  • CO, carbon monoxide; NOx, nitrogen oxide; NO2, nitrogen dioxide; PM10, particulate matter <10 μm in diameter; UFPNC, ultrafine particles.

  • *Odds ratios estimated per IQR of a pollutant and 3-day mean (lag 2–4 days) adjusted for age, gender, exposure to smoking, paternal asthma history, temperature and season.

  • †Number of COPSAC children in the model.

  • ‡p<0.05.

  • §Total concentration of ultrafine particles 10–700 nm in diameter (95% of total concentration comes from particles <100 nm).