On call: Tuna on white; hold the mercury

[Guest guest]

http://waldo.villagesoup.com/guestcolumns/story.cfm?storyID=67879 On call: Tuna on white; hold the mercury By Dana Whitten Email

this story to a friend Printer-friendly Format Add your comments Send Letter to

Editor BELFAST (Feb 21): Parents of youngsters exploring solid foods sometimes ask if fish, particularly tuna fish, is safe for them. Advertisement Most of us are aware that there is a concern about mercury contamination with harmful side effects in many species of fish; remember when swordfish was unavailable because of mercury? This article will briefly survey what is known of the environmental dangers of mercury, particularly how it is related to us in Maine, a state in which mercury levels in fish, loons and eagles are among the highest in the country. Mercury is an environmental toxin, found everywhere, that causes a wide range of adverse

health effects in humans. Three forms of mercury (elemental, inorganic and organic) exist, each with its own type of toxicity. Exposure to this heavy metal occurs after inhalation or ingestion, and everyone is exposed to at least small amounts. It occurs naturally in ore and fossil fuels such as coal and petroleum. Environmental contamination results from the actions of man, mining, smelting and industrial discharges. Elemental mercury or quicksilver is that funny silvery, beady substance we were entranced with as kids, rolling it around in our palms after a thermometer broke. (If you ever see a kid playing with liquid mercury, intervene and find out from a toxicology expert how to safely dispose of the substance; poisoning can occur from inhaling invisible vapors.) It is the liquid form of the metal and was once used in other medical instruments and is now used in dental fillings, fluorescent light bulbs and button batteries. Indiscriminate

disposal of these items in landfills or waste incinerators is a major source of environmental contamination as the substance readily vaporizes, is inhaled and passes from the lungs to the red blood cells and deposits in the brain, spinal cord and kidneys. It easily crosses the placenta and accumulates in the fetus. Elemental mercury can cause acute, life-threatening illness and chronic brain disease such as occurred with hat makers who used liquid mercury in processing felt hats. (Hence the “Mad Hatter” from "Alice in Wonderland.") It is presently believed that dental fillings do not pose a threat as elemental mercury is poorly absorbed from the gut. We didn’t worry too much when a child bit off the end of a thermometer and swallowed some. Inorganic mercury compounds (salts) have long been used for their antibacterial properties. They were also used a century ago in teething powders, all of these being long-banned from use in this country.

Ingestion can be very toxic and was a not-uncommon form of suicide. A long forgotten childhood illness, pink disease, was seen in infants exposed to teething powders and organic mercury compounds in latex paint and diaper fungicides. Inorganic mercury compounds are still available on the world market. Organic mercury compounds, primarily methyl mercury and ethyl mercury, have been produced as biocides and pesticides and were once found in two common household antiseptics: mercurochrome and merthiolate. Methyl mercury is a predominant form of mercury in our environment and is formed by microorganisms from elemental mercury dropped out of the air in precipitation, originating mainly from incineration and discarded household products evaporating into the atmosphere. It is estimated that 650 tons of mercury escape into the environment and are formed in microorganisms each year. Methyl mercury produced by microorganisms when atmospheric mercury hits water is ingested

by small fish and shellfish and bioaccumulates up the food chain as larger fish eat smaller ones. Methyl mercury is a permanent resident in these small animals and others that eat them (loons, eagles, sharks, whales, humans) and cannot be removed by processing. It is slowly excreted as consumption levels continue to rise. There is an alarming rate of death in loons in Maine due to methyl mercury; fatality rates in other animals are unknown. Methyl mercury is 95 percent absorbed by the bowel in man and passes through the placenta, into the brain and breast milk. It is most toxic to the developing brain of the fetus, causing destruction of certain cell types; after birth, retardation, blindness, deafness and seizures may develop. There have been two large human-produced disasters, in Mina Mata Bay, Japan and in Iraq. While most of the mothers were mainly unaffected, unborn children were severely affected. Interestingly, already

born, exposed children had a good capacity to recover from neurological involvement. Their symptoms included behavior changes and learning problems. There are two ongoing large studies in the world regarding the development of children in saltwater fish-eating populations. In older children and adults, larger amounts of mercury ingested from eating fish are required to produce symptoms; these include tingling, prickling or numbness of the hands and feet, or visual changes. All fish in Maine lakes, ponds and rivers have methyl mercury in them. We receive the industrial waste that blows west to east across the country, bringing to coastal states our increased rates of asthma and mercury exposure. Fish-eating fish, such as pickerel and bass, and older fish have the highest levels. Brook trout and landlocked salmon are the safest. "Safe Eating Guidelines" produced by the Bureau of Health states that pregnant and nursing women, women who may get

pregnant, and children under 8 should not eat freshwater fish, and one meal per week of the trout and salmon is safe. That is pretty sad, as fish is a nutritious, low-fat and otherwise healthy food. Other contaminants such as PCBs, dioxins or DDT are found at high levels in certain freshwater bodies preventing any safe eating of any fish. In this part of Maine that includes the Kennebec River from Augusta to the Chops. As for saltwater fish, the guidelines say no swordfish, shark or tilefish or king mackerel for pregnant or nursing women, women who may become pregnant, or children under 8. The same group should only eat one can of “white” (albacore) or two cans of light tuna per week. Consumption of striped bass and bluefish should be limited to two meals per month for everyone. Lobster tomalley is high in environmental contaminants and should not be eaten by anyone. Lastly, I need to mention that ethyl mercury in the form of thimerosal was used

in routine childhood immunizations prior to 1999. Less is known of the toxic effects of ethyl mercury than methyl mercury, but the FDA questioned whether infants receiving thimerosal-containing vaccines might be exposed to higher-than-acceptable levels of mercury. Studies have not been completed, but so far there is no consensus that this form of mercury in the doses used caused neurotoxicity that is detectable. Based on a joint recommendation by the American Academy of Pediatrics and the U.S. Public Health Service, none of the routine childhood vaccines contain thimerosal. Phenyl mercury was removed from interior latex paints in 1991. Mercury in all forms is toxic to fetuses and children. There is no effective method of treating mercury poisoning, so prevention is essential. In our state, where fishing is a popular pastime and an important form of livelihood, all of us who are consumers and providers of this generally healthy food need to be aware and up to date

on the safety issues of what goes on our plates. Pass the lemons, please! Dr. Dana Whitten practices at Belfast Pediatrics. Email this story to a friend Printer-friendly Format Add your comments Send Letter to

Editor

Relax. virus scanning helps detect nasty viruses!