You know that bit on most weather forecasts which offers information on daily pollution levels?
How often do you see an H for high - or a VH for very high? - Seriously rare!
Outnumbered by scores of of times over by L for low, innit?
M for medium is pretty rare, too. I mention it today only because I've actually spotted one.
Does this not suggest that we may be tilting at imaginary pollutant windmills?