HEALTHY ENVIRONMENTS

Eating shellfish contaminated by marine biotoxins, bacteria, viruses or chemicals may cause serious illness.

Shellfish are a high-risk food because they may grow in contaminated (unsafe) water where they filter and accumulate biotoxins, bacteria, viruses, and chemicals from their surroundings. They are often eaten without being cooked. People who eat contaminated seafood can become seriously ill.

Shellfish and seawater samples around New Zealand are regularly tested to ensure they are not contaminated with biotoxins, and public warnings are issued when shellfish are not safe to eat. Biotoxins are toxins or poisons produced by algae that live in seawater and can ‘bloom’ or massively increase, when conditions are favourable.

Auckland Regional Public Health Service advises people not to eat shellfish gathered from urban areas because of the risk from illegally dumped contaminants, animal waste, road runoff, industrial discharges, leaching from buried materials and sewage overflows.

Our recommendations are:

• don’t gather shellfish if there are warning signs posted
• don’t gather shellfish within 28 days of a nearby sewage overflow
• don’t gather shellfish from beaches with a history of poor water quality
• don’t gather shellfish after heavy rain and storms, as rain may flush sewage residues or farm run-off into waterways
• only gather shellfish from areas where the seawater is visibly clean and there are no obvious sources of contamination such as:
• sewage outfall pipes
• farm animals, especially at dairy farms
• stormwater outlets, pipes or culverts
• industrial areas
• homes – particularly if they are on septic tanks
• where boats may discharge on-board toilets.

Cooking shellfish at boiling point for several minutes will destroy most harmful bacteria and viruses, but not biotoxins or chemicals. Shellfish eaten undercooked or raw will still be risky to eat.