AN MD80; PRIOR TO DEP; HAD HAZE OF BLUE SMOKE IN CABIN. SMOKE CLRED DURING SAFETY DEMO. FLT ATTENDANT ADVISED COCKPIT THAT AFTER TKOF; SMOKE REAPPEARED IN CABIN. AN EMER WAS DECLARED AND RETURNED TO DEP ARPT.

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AFTER CLOSE DOOR WE NOTICED THAT THE CABIN HAD A HAZE OF BLUE SMOKE. NOTIFIED THE CAPT; WHO OPENED DOOR; SAW THE HAZE; MENTIONED PERHAPS IT WOULD CLR -- LET'S DO DEMO TO SEE IF IT IS THERE AFTERWARDS. DID SAFETY DEMO; THE BLUE HAZE SEEMED TO HAVE CLRED; NOTIFIED COCKPIT SAME AND WE TOOK OFF. WITHIN A FEW MOMENTS WE NOTICED THE CABIN HAD AGAIN FILLED WITH BLUE HAZY SMOKE AND FLT ATTENDANT #2 NOTIFIED FLT ATTENDANT #1; WHO NOTIFIED THE COCKPIT. THE CAPT APPEARED TO IMMEDIATELY DECIDE TO TURN BACK (THE ENGS WERE CUT BACK AND WE TURNED) AND I NOTICED SEVERAL PAX WERE BEGINNING TO LOOK ALARMED AND HAD NOTICED THE SMOKE ALSO. FLT ATTENDANT #1 MADE A PA THAT WE WERE TURNING BACK TO LAND IN ZZZ IN APPROX 10 MINUTES DUE TO 'POOR AIR QUALITY IN CABIN.' THE CAPT THEN MADE A PA NOTIFYING THE PAX THAT WE WERE LNDG BACK IN ZZZ WITHIN MINUTES. WE LANDED AND NOTICED FIRE TRUCKS IN THE AREA. WE TAXIED AND STOPPED ON TXWY TO ALLOW FIREMEN TO LOOK OVER PLANE FOR SIGNS OF FIRE; ETC. SOON WE TAXIED TO GATE AND DEPLANED ASKING PAX TO LEAVE 'BINS CLOSED' TO EXPEDITE LEAVING THE ACFT. THE #2 FLT ATTENDANT AND I NOTICED OUR EYES REALLY HURT FROM BURNING SENSATION (SMOKE?). ALSO; I NOTICED I HAD DEVELOPED A REALLY BAD HEADACHE. WE DEPLANED THE ACFT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE BLUE SMOKE HAZE WAS HYD FLUID DRIPPING ONTO HOT PNEUMATIC DUCTING IN THE AFT END OF THE AIRPLANE. RPTR DIDN'T KNOW IF IT WAS A LEAK; OR JUST LEFT OVER FLUID FROM MAINT. AT THE GATE; THE PAX DEPLANED IN AN ORDERLY MANNER WITH NO RPT OF INJURIES. RPTR STATED TWO FLT ATTENDANTS; INCLUDING THE RPTR; HAD BURNING OF THE EYES FROM THE BLUE HAZY SMOKE.