I wasn't sure whether there's anything to this so I went to UpToDate, which is a peer-reviewed database that summarizes findings from the medical literature. Here's what it had to say about mercury poisoning and fish (emphasis mine):
So basically, it looks like unless you're a pregnant woman, the amounts of mercury you can be exposed to by eating fish are several times too low to cause toxicity. I wouldn't worry about it.
Quote:Quote:
Exposure from diet — The concentration of mercury is very low in most foodstuffs (below 0.02 mg Hg/kg). However, certain types of marine fish (such as shark, swordfish, and tuna) and certain fish taken from polluted fresh waters (such as pike, walleye, and bass) may contain high concentrations of mercury. In this setting, mercury is almost completely in the form of methylmercury. It is not uncommon that concentrations of methylmercury in these fish are 1 mg/kg or even higher. Severe epidemics caused by the consumption of fish polluted with mercury have been reported from Minamata in Japan [7].
Monitoring of mercury in blood is commonly used to identify and quantify exposure to methylmercury [10]. Heavy consumers of fish, in particular those who eat mercury-containing species, may have blood mercury levels in excess of 20 µg/L (normal value less than 5 µg/L).
There is also concern that dietary exposure of children and fetuses (via the mother) may result in neuropsychological deficits [11]. (See "Genetic and environmental causes of birth defects".)
Quote:Quote:
Clinically significant poisoning from mercury is unlikely if blood and urine concentrations are below 100 µg/L.
So basically, it looks like unless you're a pregnant woman, the amounts of mercury you can be exposed to by eating fish are several times too low to cause toxicity. I wouldn't worry about it.