A320 flight crew reported a fumes event after pushback during a taxi delay. The fumes were described as a 'dirty socks' odor which caused the flight crew to experience physiological symptoms. The flight crew executed a ground gate return for maintenance.

Narrative

After pushback; single engine start; and disconnect a squall line hit the airport. We sat on the ramp for approximately 10 minutes talking with Dispatch to get a reroute around the weather and decided to shut down the engine to conserve fuel as the sit would be a bit lengthier than initially expected. After shutdown the FO (First Officer) noticed a musty dry; dirty sock smell. Eventually I could smell the same odor. We queried in-flight and they agreed they were picking up the scent in the forward and aft cabin. One of the inflight described that it smelled like a box of crayons. It was what the FO and I would categorize as a Level 2 moderate and persistent smell. We shut off the packs and APU bleed valve and noticed the odor slowly; but eventually dissipated.We notified ZZZ Ops that we would be doing a gate return and would require maintenance. On taxi back to the gate I noticed that my throat was irritated and the FO said his lips and tongue felt a bit tingly. As we deplaned a few passengers seated in the middle of the cabin mentioned they noticed the odor as well. After we deplaned and spoke with maintenance the FO also had a dull headache and what he could only describe as 'brain fog'. No other physiological symptoms were present by the inflight crew beyond the strong odor they could smell in the cabin.