Table 1

Summary of upper exposure limits of the UK National Air Quality Strategy10

Upper exposure limit or “standard”
PollutantConcentrationMeasured as
Benzene5 ppbRunning annual mean
1,3-Butadiene1 ppbRunning annual mean
Carbon monoxide10 ppm (10 000 ppb)Running 8 h mean
Lead0.5 μg/m3Annual mean
Nitrogen dioxide150 ppb1 h mean
21 ppbAnnual mean
Ozone50 ppbRunning 8 h mean
Fine particles (PM10)50 μg/m3Running 24 h mean
Sulphur dioxide100 ppb15 min mean