Fish, mercury and Joe's Valley
|Justin Hart with a cutthroat caught at Joe's Valley Reservoir.|
John Whitehead of the Utah State Division of Water Quality gave a power point presentation to the Emery County Public Lands Council. "Our charge at the Division Of Water Quality is to monitor the water in the streams and lakes in Utah and keep them clean and not polluted," said Whitehead. He stated the problem with mercury came to light in 2005 in several reports in the Salt Lake Tribune.
The Trib reported the existence of toxic mercury in the Great Salt Lake, and warned the duck hunters who hunt on those shores not to eat the ducks. After that announcement, the division of water quality decided to undertake testing of other waters in the state.
Whitehead explained the differences of elemental mercury and methylmercury, these are the two key forms of mercury. Elemental mercury is less toxic, poorly absorbed if ingested, non-bioaccumulative, has a higher exposure if inhaled, and is the same as the mercury in dental fillings.
Methylmercury is much more toxic, easily absorbed if ingested, very slowly eliminated with a half life of two-three months, is bioaccumulative, toxic to the nervous system and kidneys, and affects pregnant women, infants and small children more easily. This mercury is the more worrisome type which is found in the tissue of fish and waterfowl.
The cycle of mercury begins with pollutants entering the air, being carried back to the earth in rain and snow where it ends up in lakes and streams. The mercury then settles in the phytoplankton on the bottom of the body of water. The bigger zooplankton feed on the smaller type, and the amount of mercury increases in the tissues of the larger plankton. Small fish then eat the bigger plankton, and the mercury is again increased in the tissue. When the larger predator fish eat the smaller fish, the mercury level in the tissue again rises. With a half life of two-three months, the mercury remains in the fish tissue.
Levels of methylmercury are higher in larger, longer lived predator fish. Those levels may be increased again by regional environmental pollution. Small fish, mollusks and crustaceans have low levels unless in polluted waters.
As for the water in Joe's Valley, the water is low in mercury. The water is safe to drink, but as the levels of mercury climb the food chain, those levels in the tissue of the bigger predator fish becomes more concentrated. Mercury has been found in fish tissue in five waters in Emery County: Huntington Creek, (two locations); Joe's Valley Reservoir; Huntington Lake North; and Range Creek. Thirty three fish samples have been taken from these locations, and four results were higher than the Environmental Protection Agency threshold, with all of these being from Joe's Valley, and those samples were taken from Splake, with the cutthroat trout testing below levels of concern.
Whitehead went on to say the source of mercury in the waters of Utah is from pollution sources in other, more highly populated areas of the world. In many larger countries, the technology is not far enough advanced to remove pollutants from the emissions. These pollutants are carried in the air and moisture redeposits them in other parts of the world.
Coal fired power plants are one source of the pollutants. "Utah has very clean coal and the plants are very well equipped to reduce the contaminants in their emissions. Other countries however, with a very dirty coal supply are not as good at removing pollutants from their emissions," said Whitehead. Other sources are cement and lime plants and incinerators.
For 2007, samples are being taken throughout the year by the Division of Wildlife Resources. The Division of Water Quality has an agreement with DWR to receive fish from those samples. These fish are tested and the results of the mercury levels are posted on their Web site, along with the Department of Health Web site.
There is a national health advisory for women of child bearing age and young children to eat fish carefully. Do not eat those fish at the top of the food chain such as swordfish, shark, king mackerel or tile fish. Eat fish, but make it a fish of lesser mercury content. Those are: shrimp, canned tuna not albacore, salmon, pollock and catfish. If a person is in doubt of the mercury content of the fish, eat only six ounces a week, but do not consume any other fish during that week.
"We are in the process of sampling the fish tissues which have been gathered. By January 2008, we may have a revised advisory on our Web site," said Whitehead. "Eat fish, because they are a healthy choice, but be aware of the place that fish holds in the food chain. Avoid high end predatory fish."
The Web site to check is www.deq.utah.gov/Issues/Mercury/index.htm.
Other advisory Web pages are www.fishadvisories.utah.gov/ and www.deq.utah.gov/Issues/Mercury/duck_advisory.