NOTE: The graph below shows the measured annual average values of nitrogen dioxide (NO₂) from roadside monitoring locations nearest to Green Port Hull. The levels, derived from passive diffusion tubes, are compared to the air quality objective (AQO) of 40µg/m³. It can be seen that the sites along Hedon Road are higher than the AQO, however, the AQO applies to outdoor, non-occupational exposure over the relevant averaging period. The levels of NO₂ reduce rapidly with distance from the kerb, and before reaching building facades. As an example, the levels monitored at the roadside on the north side of Castle St, west of Market Place, are 63µg/m³, whilst the levels some 10m from the kerb fall to around 45µg/m³. Applying a similar factor to the figures in the chart indicates that the value at the nearest facade would be below the AQO.