No Detectable Risk From Mercury In Seafood, Study Shows

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University Of Rochester Medical Center

 

Date:

 

2003-05-16

No Detectable Risk From Mercury In Seafood, Study Shows

 

An exhaustive study of 643 children from before birth to 9 years of age

shows no detectable risk from the low levels of mercury their mothers were

exposed to from eating ocean seafood, according to a study in the May 16

issue of The Lancet.

 

Children born to mothers-to-be who ate an average of 12 meals of fish a week

­ about 10 times the average U.S. citizen eats ­ showed no harmful symptoms.

 

The study by scientists at the University of Rochester Medical Center is the

latest in a series of updates on children who have been studied since their

birth in 1989 and 1990 in the Republic of the Seychelles, an island nation

in the Indian Ocean. The children have been evaluated five times since their

birth, and no harmful effects from the low levels of mercury obtained by

eating seafood have been detected.

 

" Consumption of fish is generally considered healthy for your heart, yet

people are hearing that they should be concerned about eating fish because

of mercury levels, " says lead author Gary Myers, M.D., a pediatric

neurologist. " We've found no evidence that the low levels of mercury in

seafood are harmful. In the Seychelles, where the women in our study ate

large quantities of fish each week while they were pregnant, the children

are healthy. "

 

In a commentary on the research in The Lancet, Johns Hopkins scientist

Constantine Lyketsos writes that, " For now, there is no reason for pregnant

women to reduce fish consumption below current levels, which are probably

safe. " He calls the Seychelles study a " methodological advance over previous

studies. "

 

Questions about the health effects of mercury often boil down to seafood

because fish are the primary source of exposure to mercury for most people.

Scientists estimate that about half the mercury in the Earth and its

atmosphere originates from natural sources such as volcanoes, and about half

comes from man-made sources.

 

People receive most of their mercury exposure by eating ocean fish like

tuna, swordfish and shark. The fish eaten by women in the Seychelles had

approximately the same levels of mercury as those eaten by consumers in the

United States ­ but they ate much more fish than most people in the United

States. The Seychelles women, however, had an average of six times as much

mercury in their bodies, as measured in hair samples, as most people in the

US.

 

" This study indicates that there are no detectable adverse effects in a

population consuming large quantities of a wide variety of ocean fish, " says

Myers, the senior author of the Seychelles study and an internationally

recognized authority on mercury. " These are the same fish that end up on the

dinner table in the United States and around the world. "

 

In the current study doctors and nurses tested the children in a variety of

ways and measured 21 different cognitive, behavioral, and neurological

functions such as concentration, attention span, problem-solving abilities,

intelligence, and motor skills. Only two functions varied slightly according

to mercury level: Children of women with higher mercury levels were slightly

less likely to be hyperactive, and sons of such women did slightly worse on

a pegboard task. Statistically, both findings are likely due to chance, the

researchers say.

 

The Seychelles findings apply to fish bought and sold commercially, at

grocery stores, supermarkets, seafood markets, and restaurants. Those fish

are already regulated based on their mercury levels. Consumers should

carefully follow advisories about eating fish caught in lakes and rivers,

since there are hundreds of polluted waterways whose fish are dangerous to

eat in abundance, often because of pollutants like PCBs.

 

The Seychelles study came about as a result of previous work by the same

Rochester team, which put together the first precise data showing that

pre-natal exposure to mercury could harm a developing child. Their study of

the victims of an accidental mercury poisoning event in Iraq more than 30

years ago spurred them to start the Seychelles study to try to pinpoint the

levels at which mercury poses a danger.

 

Now the team is launching a new study in the Seychelles to compare the

levels of nutrients pre-natally to the health of children early in their

lives. The study has its roots in a finding in one of the previous

Seychelles reports, that children born to mothers with slightly higher

mercury levels did better on some neurological and intelligence tests than

their counterparts. That may be because those children's mothers with the

higher mercury ate more fish. This study, funded by the National Institute

of Environmental Health Sciences, is being done with colleagues at the

University of Ulster in Northern Ireland and Cornell University.

 

" There are a lot of good, vital nutrients in fish, " says Myers, who is

directing the team that is studying 300 children to compare their health

with the levels of polyunsaturated fatty acids, selenium, and other

nutrients in their mothers during pregnancy.

 

The Seychelles study, ongoing since 1989 with funding from the National

Institute of Environmental Health Sciences, is one of the longest

" longitudinal " studies ever done in children. The research has been funded

by the NIH, the U.S. Food and Drug Administration, and the Republic of the

Seychelles.

 

" The cooperation from people in the Seychelles and the Ministry of Health

has been extraordinary, " Myers says. " They recognize the importance of this

subject both to their own citizens and to the people around the world who

consume fish. "

 

In addition to Clarkson and Myers, the Seychelles team includes Philip

Davidson, Ph.D.; Donna Palumbo, Ph.D.; Li-Shan Huang, Ph.D.; Elsa

Cernichiari; and Jean Sloane-Reeves, all of the University of Rochester; and

Conrad Shamlaye of the Republic of the Seychelles. Christopher Cox, Ph.D.,

of the National Institutes of Health; Gregory Wilding, Ph.D., of the

University at Buffalo; and James Kost, Ph.D., also took part.