Sixteen people were taken to hospital early yesterday after pitch fumes were released on to Tiwai Wharf.

New Zealand Aluminium Smelters (NZAS) general manager Ryan Cavanagh said the incident happened at 2.30am.

While metal was being loaded on to the Rakiura Maru, the pitch tank system on the ship appeared to have vented and fumes drifted on to the wharf, he said.

Pitch was not being unloaded at the time.

Liquid pitch is used in the aluminium smelting process and forms part of the carbon anodes, which are made from petroleum coke, liquid pitch, and recycled carbon anodes.

Exposure to pitch fumes can cause irritation to the nose and throat resulting in coughing and nausea. Exposure to pitch can also cause increased photosensitivity to sunlight.

Some team members coughed, felt nauseated and vomited after inhaling the fumes.

All members of the metal load out team, seven stevedores, five truck drivers, and four smelter team members, were taken to Southland Hospital for observation but have since left hospital and been cleared to return to work.

Hospital protocol required that anyone who had come into contact with pitch fume must be decontaminated before entering hospital, Mr Cavanagh said.

NZAS would investigate the incident to prevent it happening again, he said.

Fire service assistant area manager Julian Tohiariki said three appliances and 10 staff attended the incident, and set up two decontamination sites - one at Tiwai Wharf and another at Southland Hospital.

A doctor also went through the decontamination shower, and three ambulance officers went through low-level decontamination as a precaution, he said.

- © Fairfax NZ News