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The chemical residue and contaminant status of New Zealand foods

Seafood, including bivalve molluscan shellfish

The Animal Products Act requires seafood operators to produce seafood products that are safe and suitable for their intended purpose. In addition, all fish and fish products exported from New Zealand and intended for human consumption must have a certificate to show the product meets the relevant regulations both here and for the importing country. Since the New Zealand fishing industry depends on export earnings for approximately 90% of its total revenue, ensuring our seafood is safe is critical to this sector.

Shellfish

Shellfish and seawater samples around New Zealand are tested each week to ensure they are not contaminated with biotoxin from blooms of algae.

New Zealand shellfish have been monitored for the presence of marine biotoxins since January 1993 when shellfish toxicity was first detected in New Zealand. As more new marine biotoxins are discovered in shellfish, new methods are developed to detect them and set appropriate guidelines. However, any new methods of analysis are rigorously tested and validated before they are used for routine regulatory testing.

Monitoring of commercial bivalve molluscan shellfish for biotoxins, heavy metal and toxic substances originating from phytoplankton is carried out under the Animal Products (Regulated Control Scheme – Bivalve Molluscan Shellfish) Regulations 2006. District Health Boards manage these monitoring programmes in commercial shellfish harvesting areas under contract to the shellfish industry via local marine biotoxin management plans.

NZFSA is also responsible for monitoring the safety of non-commercially harvested shellfish from harmful marine biotoxins through contracts with District Health Boards (DHBs) for sampling and management services, and with science providers for analytical and advice services.

DHBs issue warnings to the public about the risks of consuming non-commercial shellfish when toxicity in shellfish exceeds pre-determined limits. NZFSA also maintains a website advising the public about areas subject to warnings.

The key components of the non-commercial marine biotoxin monitoring system are:

• weekly phytoplankton sampling at suitable sites to provide early warning of shellfish toxicity

• weekly shellfish flesh testing for paralytic shellfish poison (PSP) toxins at sites with significant previous history of Alexandrium catenella and Gymnodinium catenatum induced PSP contamination

• surveillance and investigation of toxic shellfish poisoning cases.

For monitoring purposes, bivalve species are taken because their filter feeding makes them much more susceptible to contamination than non-bivalve species. Mussels are the preferred species for use for monitoring for PSP and diarrhetic shellfish poison (DSP). They are used as a sentinel species in both New Zealand and overseas monitoring programmes. This is because they accumulate toxins quickly and depurate them quickly.

Phytoplankton monitoring provides an early warning indicator of toxicity in shellfish. In areas where phytoplankton is used as the only routine monitoring option, cell numbers at or above a trigger level should prompt immediate shellfish flesh sampling and analysis for the specific toxin produced by that phytoplankton species.

Finfish

Farmed salmon is randomly sampled at the farm and processing premises, and tested for a variety of specified contaminants and veterinary medicines. Approximately 70 samples are tested each year.

Monitoring of finfish and farmed salmon is managed under the Animal Products (Regulated Control Scheme – Contaminant Monitoring and Surveillance) Regulations 2004.

NZFSA runs a fin-fish monitoring programme mainly to assess mercury, cadmium and lead levels, but may include other contaminants as appropriate. Each year a number of fish species are checked, normally 60 samples of each species are taken for analysis. Sampling is carried out under the supervision of NZFSA officers or by research organisations (eg NIWA) and samples are analysed in an NZFSA-approved laboratory.

Data from the heavy metal monitoring programme provides information for public health initiatives in New Zealand, and as a basis for official assurances to accompany fish exports.