When I am mentioning “metrics” I am referring to the time period over which air quality values are modeled or observed and whether that modeled or observed air quality value is an average, maximum or minimum (i.e. D-8 hour maximum, minimum, D-24 hour maximum or minimum, etc.). I want to know how are these metrics used to calculate the health incidences for short term adverse health impacts such as hospital admission, school/work loss days, emergency room visits, etc. Also, are these metrics used when estimating the health impacts (i.e. development of chronic respiratory diseases, possible cancer, shortened life span, etc.) from long term exposure of polluted air.