What was found
PHL - FLT 719 FCO TO PHL. THE CABIN CREW, AND SEVERAL PASSENGERS, EXPERIENCED DISCOMFORT DUE TO APPARENT "DUSTY" AIR FLOW FROM A/C AIR SYSTEM. THE FLIGHT CONTINUED TO PHL WITHOUT FURTHER INCIDENT. REMOVED AND REPLACED ALL EIGHT CABIN RECIRC FILTERS. FOUND VERY DIRTY.