Port Health Authorities are responsible for ensuring that bivalve molluscs harvested in UK waters are safe for consumers to eat. This is achieved by sampling shellfish beds for contaminants. Shellfish beds are classified depending on contaminant levels and movement documentation is issued to enable processing plants to see the origin of the shellfish. Port Health Authorities, in conjunction with CEFAS, are also responsible for monitoring seawater quality and approving and regulating shellfish purification plants.

Port Health Authorities, along with representatives from the shellfish industry, the Food Standards Agency (FSA), CEFAS and other regulatory bodies form Local Action Groups, set up to improve the long term classification of shellfish harvesting areas. These groups produce an Action Plan which defines procedures in the event that contamination levels in shellfish beds exceed certain levels. The actions taken vary from further investigation to closure of the shellfish bed depending on contamination levels.