All shellfish growing waters are classified by the Maine Department of Marine Resources using the requirements and standards of the National Shellfish Sanitation Program (NSSP). Maine's shellfish program must conform to the NSSP in order for its shellfish industry to engage in interstate commerce. Each area classification is strictly evaluated by the United States Food and Drug Administration on an annual basis.
Molluscan shellfish (soft shell clams, quahogs, oysters, mussels, razor clams, and others that have a hinged shell) are filter feeders. They pump water through their systems, filtering out and absorbing any particles that are in the water. The main food source for molluscan shellfish is microscopic algae. Some microscopic algae produce toxins, called biotoxins, that don't harm shellfish but can cause illness or death in people who eat them.
Molluscan shellfish also absorb anything else that's in the water including bacteria, viruses, and contaminants. These can accumulate to the point where the shellfish become unsafe to eat. Excellent water quality, pollution control, and biotoxin monitoring are essential for shellfish to be a safe food source.
The Maine Department of Marine Resources and the Town of Brunswick collect and regularly test both molluscan shellfish and the water where they grow to make sure the shellfish are safe to eat. When conditions pose a threat to public health, action is taken, by closing the area to shellfish harvesting.
Maine Department of Marine Resources Brunswick Growing Area Classification Maps