Table 4

Risk of a PEF episode starting within seven days of an upper respiratory tract infection according to personal exposure to NO2

NO2 exposure
level (μg/m3)
No of upper
respiratory
episodes
No of PEF
episodes
RR95% CI
⩽895211
8–1383191.10.6 to 1.8
13–2869191.20.7 to 2.1
>2826111.91.1 to 3.4
  • Exposures to NO2 were estimated for the seven day period starting two days before the onset of the relevant upper respiratory episode by a method described in the text.

  • p for trend = 0.04.