Variable
arsenic_pm10
arsenic_pm25
cadmium_pm10
cadmium_pm25
chromium_pm10
chromium_pm25
cobalt_pm10
cobalt_pm25
copper_pm10
copper_pm25
lead_pm10
lead_pm25
manganese_pm10
manganese_pm25
nickel_pm10
nickel_pm25
vanadium_pm10
vanadium_pm25
zinc_pm10
zinc_pm25