A one-year study of Tauranga Harbour's shellfish showed they were often contaminated at levels unsafe for eating.

The study showed a direct causal link between pollution like sewage overflows or heavy rainfall and unsafe levels of viruses and bacteria in the gut tissue of shellfish.
Bay of Plenty District Health Board medical officer of health Dr Phil Shoemack says Tauranga Harbour is not unique with its contaminated shellfish.
'Shellfish harvested close to urban or significant pastoral farming areas are often contaminated. It's a common problem in New Zealand and also reflects the situation in many harbours around the world,” Phil says.
'The benefit of this study is we now have direct knowledge of the state of shellfish locally and can let people know the risks,” he says.
In addition to testing the viral and bacterial levels in the shellfish, New Zealand Food Safety Authority scientists have tested cooking methods to determine when viruses are destroyed.
They found steaming or lightly cooking shellfish was not sufficient. Boiling shellfish for at least three minutes was the only effective cooking method.