Fish advisories warn about possible mercury contamination, but many people aren't aware of the risks. (Photo by Lester Graham)
There’s no disputing that fish is healthful food, but too much of certain
kinds of fish can be dangerous, especially if you’re a woman planning to
have children. That’s because some fish contain elevated levels of
mercury. Mercury is a toxic contaminant that can cause neurological
damage. Julie Halpert filed this report about the harms mercury can
cause:
Transcript
We’re continuing our series ‘Ten Threats to the Great Lakes.’ One of the
threats identified by experts was air pollution that in turn pollutes the
lakes. The Great Lakes Radio Consortium’s Lester Graham is our guide
in this series. He says the next report looks at one pollutant that
eventually affects people.
There’s no disputing that fish is healthful food, but too much of certain
kinds of fish can be dangerous, especially if you’re a woman planning to
have children. That’s because some fish contain elevated levels of
mercury. Mercury is a toxic contaminant that can cause neurological
damage. Julie Halpert filed this report about the harms mercury can
cause:
Three years ago, when she was 18, Ayla Brown was healthy, but
suddenly, she started getting sick all the time. She was always tired, she
became anemic and had sore throats. Her tonsils had deteriorated so
much that they had to be removed. Her doctor couldn’t figure out why,
so he decided to test her for heavy metals poisoning.
The result? Ayla’s mercury levels were off the charts. They were five
times higher than the normal level. Her entire family was tested and
their levels also were above normal.
“The only conclusion we could come to is that in the past year or so since
we had moved to Ann Arbor, we had started eating a lot of fish and a lot
of fish that we now know is very known to be high in mercury, such as
swordfish and tuna and stuff like that.”
The Browns ate several meals of fish every week. Some of it was
ocean fish. Some of it was Great Lakes fish. After the diagnosis, they
cut fish out of their diet altogether. Within a year, the mercury levels
returned to normal.
“You are trying so hard to eat healthy and my family always was very
health conscious and so it’s so frustrating when you’ve done something
that you thought was good for you and realize that it was completely the
wrong thing.”
Fish are generally considered part of a healthy diet, but not all fish are
entirely safe. That’s because of mercury. Mercury exists naturally in the
environment at low levels, but higher amounts are getting into the food
chain.
Coal-burning power plants emit mercury, which eventually settles into
the Great Lakes. Then, aquatic microorganisms convert the substance
into methyl mercury, which is more toxic.
Those microorganisms form the base of the food chain. Small fish eat
microorganisms. Then, larger fish eat the smaller ones. As that happens,
the mercury concentrations escalate, making big large mouth fish like
trout, salmon and some walleye especially contaminated.
When people eat the fish, the mercury is passed on to them. Women of
childbearing age and their fetuses are most at risk.
Michael Carvan is with the University of Wisconsin-Milwaukee’s Great
Lakes Water Institute. He says the exposure isn’t just from the fish that
women eat while they’re pregnant. A woman can pass her entire lifetime
load of mercury to her baby. He says that 15% of all women of
childbearing age have high enough levels so that their fetuses will
contain mercury of one part per million or higher.
“Even at really low levels, around one part per million, you’re talking
about some subtle coordination difficulties, you’re talking about
problems with memory and problems with neuro-processing and IQ
deficits.”
Because of these concerns, the Environmental Protection Agency and
the Food and Drug Administration issued an advisory for women of
childbearing age and children, suggesting they eat fish and shellfish only
twice a week.
But one expert is concerned by all this talk about how mercury harms
people. John Dellinger was on a task force, which provided guidance on
fish consumption advisories. Dellinger studied people who lived on
Lake Superior who he thought would eat a lot of fish, but he found
something else.
“We basically discovered that from an epidemiologic point of view, these
populations have other things that are adversely affecting their health,
that in fact will probably overshadow anything we’re going to see from
the contaminants in their fish.”
Dellinger said the people were so concerned about contaminants in
fish, that they started relying on store-bought, processed food instead.
Those foods were higher in fat and sugar and contained other, less
healthful, ingredients. So, obesity and diabetes caused health problems,
not mercury poisoning, and Dellinger says that ended up being a worse
situation.
He says the key is to choose wisely, avoiding fish such as swordfish,
tuna steaks and the larger predator Great Lakes fish that are high in
mercury. That’s the only measure you can take right now, but that doesn’t
solve the problem. The real challenge will be to get rid of the mercury
that ends up contaminating the fish.
For the GLRC, I’m Julie Halpert.
