EPA has suggested an exponential fit to the upper 10 percent of a PM10 distribution and using that fit to determine a once per year frequency of occurrence. My question is one of pedigree -- does such a technique have merit and status in the statistics community? Or is there a better technique for determining the PM10 value that is expected to occur once per year? TIA Clint -- Clint Bowman INTERNET: clint at ecy.wa.gov Air Quality Modeler INTERNET: clint at math.utah.edu Department of Ecology VOICE: (360) 407-6815 PO Box 47600 FAX: (360) 407-7534 Olympia, WA 98504-7600