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New Hampshire Department of Environmental Services

FAQs – Health Issues
  • Are the shellfish safe to eat?
    Shellfish harvested from "closed" areas have the potential to result in illness if they are consumed, because filter-feeding shellfish can concentrate harmful bacteria and viruses. When contaminated shellfish are eaten by humans, serious illnesses such as gastroenteritis, septicemia, salmonellosis, hepatitis, cholera, and typhoid can result. These illnesses occur mainly from the result of human sewage, as well as animal wastes, reaching the shellfish growing waters.
    Paralytic Shellfish Poisoning (PSP) may cause death through respiratory paralysis. Less severe symptoms start with numbness in extremities and/or tingling of the lips. PSP or "Red Tide" is caused by a population "bloom" of naturally occurring, microscopic algae which produce a potent neurotoxin. These toxins can accumulate in the bodies of filter feeding bivalves, such as clams, mussels and oysters which ingest the organisms. Humans who eat the shellfish may become afflicted with PSP. Although PSP is the most common type of harmful algal bloom to affect NH shellfish, there are other harmful algal blooms which can cause memory loss, gastrointestinal problems, or other symptoms in those who consume the contaminated shellfish.
    The consumption of raw shellfish, even if harvested from open areas, can carry an inherent health risk. This is especially true for people who suffer from liver disease, weakened immune systems, or other health problems. Such people are at greater risk not only from the illnesses associated with human or animal waste, but also from illnesses caused by naturally occurring bacteria.
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  • Does cooking the shellfish eliminate the health risks?
    Adequate cooking of shellfish will destroy harmful bacteria and viruses, thereby eliminating the health risks associated with them. The Interstate Shellfish Sanitation Conference recommends the following guidelines to ensure adequate cooking of shellfish:
    • Tips for Cooking Oysters & Clams in the Shell
      • Boil live oysters in boiling water for 3 to 5 minutes after shells open. Use small pots to boil or steam oysters. Do not cook too many oysters in the same pot because the ones in the middle may not get fully cooked. Discard any oysters that do not open during cooking.
      • Steam live oysters 4 to 9 minutes in a steamer that is already steaming.
    • Tips for Cooking Shucked Oysters & Clams
      • Boil or simmer for at least 3 minutes or until edge curl.
      • Fry in oil for at least 3 minutes at 375° F.
      • Broil 3 inches from heat for 3 minutes.
      • Bake for 10 minutes at 450° F.
    Although adequate cooking will kill bacteria and viruses, it does not eliminate the danger of eating shellfish contaminated by "Red Tide". Paralytic Shellfish Poisoning is a condition caused by a toxin, not by a bacteria or virus. The heat from cooking will not destroy the toxin.
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NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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