Potentially. It all depends on where the oyster came from, how it was handled, and how it got to your plate, and how strong your immune system is. There is always a risk.
The danger in raw oysters is not in the mercury level, but rather the pathogens and virus that they may contain. The mercury level of oyster considered “lower levels” category in the similar range of that of salmon.
Oysters are filter feeders and can contain pathogens and bacteria. Immuno-compromised individuals, individuals with poor liver functions, or pregnant, or other conditions may want to avoid raw oysters.
But for healthy individuals, oysters are eaten raw as in this Executive Chef shows on YouTube how to shuck and eat one. Shucking an oyster means to open and remove half of its shell. They are usually opened with oyster top up. Which side is the top? The flat shell is top. The rounded shell is bottom.
The Interstate Shellfish Sanitation Conference says …
“Oysters harvested from approved waters, packed under sanitary conditions, and properly refrigerated are usually safe for raw consumption by healthy individuals. Cooking oysters to an internal temperature of 140 F or greater for 4-6 minutes destroys the common microorganisms of public health concern.”
Wikipedia says that “oysters must be eaten alive, or cooked alive.” That is why you do not often see frozen raw oysters. After frozen and thawed, their texture changes so that they need to be consumed cooked, and can no longer be consume raw. If they are canned, they are cooked before canning.
SafeOysters.org says that shucked shellfish can be kept in the refrigerator at …
“Temperatures below 35°F will minimize bacterial growth and help shucked shellfish stay fresh longer, usually 4 to 7 days or by the “use by” date printed on containers. Refrigerator temperatures greater than 40°F will decrease shelf life.”
However, if you remove half its shelf, don’t you kill the shellfish? So personally, I get nervous at keeping shucked oyster that long.
An oyster that can not close its shell is a dead oyster. When buying oyster, buy only those with fully closed shells. Oyster should be purchased live, as fresh as possible, and from a quality source. To avoid killing the oyster due to lack of oxygen, do not keep oysters in air-tight containers.
If you eat at a restaurant, eat them from a place you trust. The chef should know all of the above and be able to detect bad oysters (including by smell) and toss them out. Some bad oysters can look the same as good ones.
If you cook the oyster, scrub and wash the shell thoroughly and then it can be smoked, boiled, baked, fried, roasted, stewed, canned, pickled, steamed, broiled.
Boiling is a good way to kill pathogens. If you boil them in the shell, they will open on its own, saving you the need to shuck them. Boil them until the oyster flesh edge curls.
Here on YouTube is what Oysterologist Daniel Notkin says about oyster and his reply to eating raw oysters: “Get them as fresh as possible, with a chef that you trust. There is always a risk. … But if you look at the grand scheme of things, there are more recalls on peanut butter, meat, eggs, than anything we heard of oysters.”
WiseGeek.com says …
“Eating raw oysters can potentially be dangerous. Taking the time to cook an oyster will greatly reduce the risk of picking up a food-borne illness. People who are pregnant or who have compromised immune systems should always cook an oyster before eating it”
Disclaimer: I am not a profession chef. Everything I learned about oysters, I’ve learn from the Internet.