I'm just worried about the steelwork near my home. Even if somebody measure emissions every once in a while, two problems can arise:
1) In some particular time frame (for example night) the steelwork could also emits more than usual pollution; it means that emissions control which are eventually done every once in a while could not really fully correspond to the reality.
2) The level of pollution, I think, is not the same in all the area. If I live near the steelwork maybe there is more pollution with respect to someone living far away. So a given measure is however not reflecting the effective pollution in every housing units.
However , thanks for your interest.