​Bivalve shellfish are filter feeders, ingesting and concentrating micro-organisms and particulate matter from the water column and sediments. This filter feeding process can result in the accumulation of certain chemical residues of concern to human health if those chemicals are present in the shellfish growing areas. Such chemical residues are typically related to industrial activity in catchments and include heavy metals, organo-chlorines and organo-phosphates.

Food Standards Australia New Zealand (FSANZ) sets Maximum Levels (ML’s) for chemicals with significant health impacts. Such chemicals include cadmium, mercury, lead, and arsenic.  

FSANZ sets Generally Expected Levels (GELs) for some other chemical contaminants with less significant health impacts. These GELs are not legally enforceable but act as a benchmark to measure the contaminant levels in food.

Chemical contaminant surveys show that all commercial shellfish farms in Tasmania comply with FSANZ standards.