Cases of mercury poisoning go back thousands of years. Mercury probably killed the first Chinese emperor, Qin Shi Huang, in 210 B.C.E. at the age of 39. He believed mercury pills would grant him immortality (oops). But Mercury doesn’t just kill. It can first drive a victim to insanity. The phrase “as mad as a hatter” harkens back to Victorian England, where mercury was used in haberdasheries. (Mercury inhalation is still a problem in many workplaces.)
Mercury’s notoriety as a poison derives from these instances of acute exposure. Diagnosing these cases is clinical child’s play. The symptoms—like numbness in the extremities, weakness, and a narrowing of the field of vision—are well known, and they appear soon after exposure. The challenge for toxicologists is sussing out the more subtle effects of lower doses of mercury, like the ones you might get from eating fish.
Fetuses and small children, for example, are extremely sensitive to mercury. Exposure to mercury in the womb can affect cognitive development, impair memory and attention, and slow language acquisition, even when the doses are too low to cause any observable symptoms in the mother.
Chronic, low-dose exposure in adults could also be a concern. Some doctors believe that trace levels of mercury contribute to heart disease and high blood pressure, though the evidence for this is currently inconclusive. These claims are based on a small number of studies conducted on discrete populations living in remote areas. In addition, the precise mechanism that would link low-dose mercury to heart disease isn’t fully understood.
So how much is too much?
The Environmental Protection Agency recommends consuming a daily maximum of0.1 micrograms of mercury for each kilogram of your body weight. That would limit a 176-pound adult (the national average) to 8 micrograms of mercury each day.
What does that mean in terms of cans of tuna or pieces of sashimi? Well, you’ll need a species-by-species chart of mercury concentration to figure that out. The amount of mercury in certain types of fish varies greatly. For instance, the average adult could eat 13 ounces of fresh salmon per day while staying under the EPA recommended maximum. You should avoid swordfish, though—eating just 0.14 ounces, a mere forkful, would put you over the limit.
The Environmental Protection Agency recommends consuming a daily maximum of0.1 micrograms of mercury for each kilogram of your body weight. That would limit a 176-pound adult (the national average) to 8 micrograms of mercury each day.
What does that mean in terms of cans of tuna or pieces of sashimi? Well, you’ll need a species-by-species chart of mercury concentration to figure that out. The amount of mercury in certain types of fish varies greatly. For instance, the average adult could eat 13 ounces of fresh salmon per day while staying under the EPA recommended maximum. You should avoid swordfish, though—eating just 0.14 ounces, a mere forkful, would put you over the limit.
SpeciesFDA AverageAtlantic, Pacific Catch
Domestic Samples
Anchovies0.04ND, 0.04
Cod0.100.06, 0.11
Crab0.060.26, 0.15
Flounder0.050.08, 0.07
Halibut0.250.25, 0.28
Herring0.040.04, 0.14
Lobster0.170.28, 0.17
Mackerel0.150.22, 0.09
MusselsND0.08, 0.03
OystersND0.07, 0.06
Perch (ocean)ND0.08, 0.08
Pollock0.060.02, 0.06
Salmon (fresh)0.010.13, 0.04
Salmon (canned)0.05ND, 0.04
Scallops0.050.01, 0.04
Shark0.990.75, 0.80
ShrimpND0.04, 0.03
Snapper0.190.28, 0.25
Swordfish0.980.98, 0.98
Tilefish1.451.45, ND
Tuna (fresh/frozen)0.380.28, 0.24
Tuna/albacore (all forms)ND-0.760.47, 0.17
Tuna/yellowfin (all forms)ND-0.760.31, 0.06
Data Source: Sunderland EM. (2007)
http://www.salon.com/2014/08/17/the..._lot_higher_than_you_think/?source=newsletter
]
Woods Hole Oceanographic Institution
Mercury’s notoriety as a poison derives from these instances of acute exposure. Diagnosing these cases is clinical child’s play. The symptoms—like numbness in the extremities, weakness, and a narrowing of the field of vision—are well known, and they appear soon after exposure. The challenge for toxicologists is sussing out the more subtle effects of lower doses of mercury, like the ones you might get from eating fish.
Fetuses and small children, for example, are extremely sensitive to mercury. Exposure to mercury in the womb can affect cognitive development, impair memory and attention, and slow language acquisition, even when the doses are too low to cause any observable symptoms in the mother.
Chronic, low-dose exposure in adults could also be a concern. Some doctors believe that trace levels of mercury contribute to heart disease and high blood pressure, though the evidence for this is currently inconclusive. These claims are based on a small number of studies conducted on discrete populations living in remote areas. In addition, the precise mechanism that would link low-dose mercury to heart disease isn’t fully understood.
So how much is too much?
The Environmental Protection Agency recommends consuming a daily maximum of0.1 micrograms of mercury for each kilogram of your body weight. That would limit a 176-pound adult (the national average) to 8 micrograms of mercury each day.
What does that mean in terms of cans of tuna or pieces of sashimi? Well, you’ll need a species-by-species chart of mercury concentration to figure that out. The amount of mercury in certain types of fish varies greatly. For instance, the average adult could eat 13 ounces of fresh salmon per day while staying under the EPA recommended maximum. You should avoid swordfish, though—eating just 0.14 ounces, a mere forkful, would put you over the limit.
The Environmental Protection Agency recommends consuming a daily maximum of0.1 micrograms of mercury for each kilogram of your body weight. That would limit a 176-pound adult (the national average) to 8 micrograms of mercury each day.
What does that mean in terms of cans of tuna or pieces of sashimi? Well, you’ll need a species-by-species chart of mercury concentration to figure that out. The amount of mercury in certain types of fish varies greatly. For instance, the average adult could eat 13 ounces of fresh salmon per day while staying under the EPA recommended maximum. You should avoid swordfish, though—eating just 0.14 ounces, a mere forkful, would put you over the limit.
SpeciesFDA AverageAtlantic, Pacific Catch
Domestic Samples
Anchovies0.04ND, 0.04
Cod0.100.06, 0.11
Crab0.060.26, 0.15
Flounder0.050.08, 0.07
Halibut0.250.25, 0.28
Herring0.040.04, 0.14
Lobster0.170.28, 0.17
Mackerel0.150.22, 0.09
MusselsND0.08, 0.03
OystersND0.07, 0.06
Perch (ocean)ND0.08, 0.08
Pollock0.060.02, 0.06
Salmon (fresh)0.010.13, 0.04
Salmon (canned)0.05ND, 0.04
Scallops0.050.01, 0.04
Shark0.990.75, 0.80
ShrimpND0.04, 0.03
Snapper0.190.28, 0.25
Swordfish0.980.98, 0.98
Tilefish1.451.45, ND
Tuna (fresh/frozen)0.380.28, 0.24
Tuna/albacore (all forms)ND-0.760.47, 0.17
Tuna/yellowfin (all forms)ND-0.760.31, 0.06
Data Source: Sunderland EM. (2007)
http://www.salon.com/2014/08/17/the..._lot_higher_than_you_think/?source=newsletter
]
Woods Hole Oceanographic Institution
