Two other straddle crane drivers were made sick by the fumes over the course of the morning, and both have since ended up in hospital, the crane operator said.
A further two stevedores were hospitalised later in the day, bringing the total to five.
He said a container of crude sulphate turpentine was identified as the source of the leak.
The man said the decision was still made to load the container on to the ship, resulting in the injury of two stevedores. The Fire Service was called to that event about 12.30pm.
He said the correct operating procedure was for all operations to be shut down within 300m downwind of such a leak - which he said did not happen.
"I reported this as soon as I got hit with the gas and told them. They sent two managers [who] came out, they walked around and said they never smelled it. But we're up above them, another 10.5m up in the air," he said.
The man's medical discharge certificate shows he reported dizziness, headaches and nausea. He still had headaches and vertigo, he said.
He has contacted the Maritime Union NZ and planned to report the incident to Worksafe and Maritime NZ tomorrow.
Bay of Plenty Regional Council regulatory compliance team leader Alex Miller previously told the Bay of Plenty Times that crude sulphate turpentine leaked from a tank at the port in a "minor spill".
The Bay of Plenty District Health Board has confirmed the five men were treated and discharged on Friday afternoon and evening.
Port of Tauranga corporate services manager Sara Lunam said as far as she knew the Fire Service was called in to assist with a leak and men had been taken to the hospital as a precaution.
"There will be an investigation into the incident but it wouldn't be proper to comment further until we know what happened. We do take it very seriously and will follow up," she said.
Maritime NZ told the Herald the incident happened on land and was in WorkSafe's hands.
A WorkSafe spokeswoman said the organisation was notified of the incident on Friday and was making initial inquiries.
