A300
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Physiological - Other; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Gate; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
After pushing back on the ZZZ ramp; we went to start the engines.  During the start; the Blue Hydraulic pressure gauge came up low; just to the yellow line.  Note that the Blue Hydraulic system had been serviced in ZZZ by Maintenance while we hub turned.  In consultation with ZZZ Maintenance; we shut down in position and they went to service the Blue Hydraulic.  After some time the Blue Hydraulic was back in the Top Hat.  Cleared off Maintenance; and restarted engines.  After start; When the bleed air transferred over to the packs; we immediately started getting smoke in the cockpit.  I initially smelled it.  Then with the rising sun coming in my side window; you could clearly see the smoke (vaporized Skydrol?)  coming out of my air vent starting to fill the cockpit.  The intensity of smoke increased with time.  We opened the windows for fresh air and shut off the packs.  Approximate about 3 - 4 minutes of chemical exposure.  We wound up taxiing back to the gate and eventually shut down the engines.  I felt a little light head; a scratchy throat; and was beginning to cough.  Captain had some similar issues.   After speaking with Chief Pilot; and self-evaluating our symptoms; we were driven to the local ER to get checked out.  At the hospital; poison control was contacted; X-ray's were taken and a breathing treatment administered before being released. Exact cause for this issue is still unknown to me...but it clearly has to do with the servicing of the Blue Hydraulic system and possible failure of aircraft parts.
A300 First Officer reported a ground gate return due to a fume event during departure taxi.