Mercury rising

The Missouri Department of Health is advising limited consumptions of fish from Missouri waters, which could be contaminated with increasing levels of mercury.
Saturday, May 5, 2007 | 1:00 a.m. CDT; updated 12:26 a.m. CDT, Sunday, July 20, 2008
Fred Gillmore attaches a crappie on a stringer at Little Dixie Lake Conservation Area on April 26. Species of crappie are not listed in the Missouri Department of Health 2007 guidelines for eating.

Junior Prince sat on a white 5-gallon bucket hoping for a bite on one of his three lines in Little Dixie Lake. The catfish weren’t interested.

Prince, a retired street sweeper for the city of Columbia, hasn’t caught many fish this season at Little Dixie. When he does reel one in, he usually gives the catch away, he said.

Something's fishy

Which fish across the state are under advisory?
  • Carp greater than 21”
  • Largemouth, spotted and smallmouth bass greater than 12”
Which fish in Mississippi and Missouri rivers are under advisory?
  • Sturgeon of all sizes
  • Catfish greater than 17”
How much of these fish are OK to eat?
  • One meal of all bass or sturgeon species no more than once a month
  • One meal of carp, catfish and all other species no more than once a week
What is a meal?
  • Eleven ounces of uncooked fish for a 150-pound adult
  • Three ounces of fish for children under 40 pound or 13 years
Preparing fish
  • Remove bones, internal organs, skin and fat
  • Bake, broil or grill on a rack to allow fat to drip away
  • Avoid pan frying in butter or animal fat, and using juices
  • Do not eat the eggs
  • Even prepared fish will still contain the same amount of mercury
Who is sensitive to mercury poisoning?
  • Women who are pregnant
  • Women of childbearing age
  • Nursing mothers
  • Children under 13 years

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“It’s just a way to get out and be outside,” he said.

Prince said he read newspaper stories about mercury contamination in the Missouri and Mississippi rivers “five or six years ago,” but it’s not something he pays much attention.

Keeping the public apprised of the risk posed by contaminants in fish has become an annual exercise for state governments. The Missouri Department of Health and Senior Services releases advisories before each fishing season that provide guidelines for eating fish from various waters.

The 2007 guidelines include a statewide recommendation to limit the consumption of largemouth, smallmouth or spotted bass larger than 12 inches to one meal a month, or 3 ounces of fillet for children younger than 13 or less than 40 pounds, and 11 ounces for adults, because of mercury.

There are also new advisories this year on the consumption of catfish and carp taken from the Missouri and Mississippi Rivers: no more than one meal per week of catfish greater than 17 inches and carp greater than 21 inches based on the presence of mercury, polychlorinated biphenyls and chlordane. The 2006 advisory had allowed for two carp meals in one week. The only advisory for 2005 advised people not to eat largemouth bass greater than 12 inches caught from anywhere in Missouri.

The Health Department wants people with developing nervous systems — children 13 and under, pregnant women and women who might have children in the near future — to pay special attention to how much locally caught fish they eat.

Prince, who also fishes in Stephens Lake, views fish from lakes as being less contaminated than from rivers. “I don’t catch fish in the river, so I don’t really worry about the mercury,” he said.

Mercury, however, knows no boundaries.

The Missouri Department of Conservation tracks the mercury level in more than 300 bodies of water in the state and has been collecting data for more than 20 years, said Mike McKee, a resource scientist with the Department of Conservation. Testing sites include lakes, rivers and creeks.

McKee estimates that 50 to 60 percent of mercury is introduced to the environment through the air.

“What is released is mercury,” he said. “It is converted to methyl mercury in the water or soil by bacteria. Most of the mercury is from atmospheric deposition. That is why it is all over the state.”

“Mercury can be emitted from coal combustion and other chemical manufacturing,” said John Millett of the Environmental Protection Agency. Medical and urban waste incineration is also a contributor, according to the EPA.

Prince wasn’t surprised by that connection. “Coal’s got a lot of mercury,” he said. “Gotta get electricity somewhere.”

Millett said people should be aware of the types of fish they are eating. “It really is important for people to read the state advisory and follow its warnings,” he said.

The 2007 Missouri advisory suggests that all individuals consume fillets from smaller fish because larger fish are likely to contain higher levels of methyl mercury. That’s because methyl mercury bioaccumulates, or builds up, over time in flesh. Fish absorb methyl mercury from the water and ingest it when they eat smaller fish.

Consuming foods with high levels of mercury is a health risk for humans. “It’s a neurotoxin,” Millett said.

In humans, mercury is primarily associated with damaging the neurosystem, especially when the person is young.

“Mercury does two things; it bioaccumulates in the body and it biomagnetizes to the fish from their surroundings,” said Todd Blanc, fish advisory coordinator for the Health Department. Predatory fish such as bass “tend to have higher concentrations because they are eating other fish,” he said.

Mercury accumulates in humans just as it does in fish and may stay in the body for several years, Blanc said. Research has shown methyl mercury at high levels may damage adult cardiac and gastrointestinal systems, and the kidneys, according to the Department of Health.

Evidence also suggests that mercury can cause developmental delays at low levels in children, Blanc said. “If anyone thinks that they are elevated based on their consumption, I would suggest that they follow up on that and consult their doctor.”

Cleaning or cooking can’t remove methyl mercury from fillets, and testing for mercury contamination is done to mimic human consumption.

“We collect fish and take fillet samples, what people would normally consume,” said Brian Todd, a fisheries regional supervisor for the Department of Conservation. Samples are sent to an outside laboratory. The results are shared between the Conservation Department and the Department of Health.

Fish are taken from different streams and lakes each year to test for contaminants, Todd said. Mark Twain Lake is on the testing list for this year, along with Lake of the Ozarks and the Missouri River near Napoleon.

Updating the consumption guidelines each year is a partnership among several agencies, including the Health Department, Conservation Department and the EPA. The consumption guidelines cover only noncommercial fish, or those harvested and prepared by an individual. Fish in supermarkets are regulated by the U.S. Food and Drug Administration.

Health benefits of eating fish

  • Recent medical research provides evidence that both the young and old can gain significant benefits from eating fish. In adults, the death rate from heart disease was 36 percent lower among those who ate fish twice a week compared with those who ate little or no seafood.
  • Fish is a good source of high-quality protein and essential nutrients. Fish is low in cholesterol, and some fish contain fats (omega-3 fatty acids) that may be beneficial in reducing heart disease.
  • To find more information on the benefits of eating fish and the potential adverse effects from mercury in fish go to

Source: Missouri Department of Health

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