Air carrier Captain reported a fumes event described as a 'dirty socks' odor after disconnecting from the ground pushback crew. After an extensive delay in which passengers and flight attendants experienced physiological symptoms; a parking spot was assigned and all passengers and flight attendants deplaned safely.

Narrative

This was the second odor event for the day in Aircraft X. APU was deferred. We were parked at a hard stand at ZZZZ. Engine #2 was started per external air procedures. We pushed back and disconnected from ground crew. Engine #1 was started per crossbleed start procedures. Dirty sock and chemical odor was detected by the flight crew after turning on bleeds and packs. Seconds later; the inflight crew notified us of strong odor in the cabin; especially in the aft cabin. The First Officer and I decided to return to a gate immediately to deplane the customers and crew. We referenced the airport company pages for an OPS frequency; but unfortunately there is none. We immediately asked Ground Control for a gate and to taxi to terminal. He said he would return shortly and asked us the nature of our situation. We answered that we had odor in the aircraft and needed to deplane immediately. While we waited; we referenced and performed the Fumes/Smoke Removal checklist in the QRH. I referenced the A320/321 odor guidance in the operations manual. Customers and inflight complained of the odor and were uncomfortable. I asked Ground Control several times for a gate; but was denied. They responded that I must park at the hard stand and that ground crew was returning. It took XX minutes for ground crew to finally waves us into the parking spot. I repeatedly stated that I needed immediate assistance. Upon shutdown of the engines; I went to the back to check on the inflight crew and customers. Some of the crew were showing signs of discomfort (headache and dizziness) and some customers were covering their faces due to the odor. I also witnessed some of those customers coughing. The air stairs arrived rather quickly and I helped deplane customers and opened the forward right door for ventilation.