EPA pm2.5 data by county appears to be AQI values, not pm2.5 as micrograms/cubic meter

[tibbben]

Something doesn't look quite right ... the data that is loaded is actually the AQI for days where pm2.5 was the defining variable. This is likely not so important for any demos we do for the symposium, but at some point we need to re-curate that data as AQI, not pm2.5 (units, measures, descriptions, vocabularies, even perhaps names of variables). This likely affects all variables that use the county daily AQI summaries as a source.

[kzollove]

This still exists and is a fairly bad bug