Too much of a good thing (fish): methylmercury case study.* Mercury is an element that occurs naturally in the earth's crust. * Over geological time, it has been distributed throughout the environment by natural processes. * Since the industrial revolution, however, anthropogenic an·thro·po·gen·ic adj. 1. Of or relating to anthropogenesis. 2. Caused by humans: anthropogenic degradation of the environment. sources have become a significant contributor to the environmental redistribution of mercury and its compounds. * Elemental mercury can combine in the environment with chlorine, sulfur, phosphorus, and other elements to form inorganic compounds. * In aquatic microorganisms, inorganic mercury can combine with carbon to form organic mercury compounds. * Of these, methylmercury is the most abundant. * In surface waters, methylmercury is rapidly accumulated by aquatic organisms. * It biomagnifies as it ascends the food chain. * Carnivorous car·niv·o·rous adj. 1. Of or relating to carnivores. 2. Flesh-eating or predatory: a carnivorous bird. 3. species (e.g., freshwater pike and marine sharks, swordfish, king mackerel mackerel, common name for members of the family Scombridae, 60 species of open-sea fishes, including the albacore, bonito, and tuna. They are characterized by deeply forked tails that narrow greatly where they join the body; small finlets behind both the dorsal and , and tilefish tilefish, common name for a superior and brilliantly colored food fish of temperate and tropical waters, marked by fleshy flaps on the top of the head and at the corners of the mouth. It is a bottom feeder reaching 3 ft (91 cm) in length and 35 lb (15.8 kg) in weight. ) may have mercury tissue concentrations as much as 10,000 to 100,000 times the concentration in the ambient waters. * In humans, methylmercury typically enters the body through the diet. * Contaminated fish are the primary source in most cases. * Poisoning outbreaks in Japan and Iraq have revealed serious effects on developing fetuses. * These effects occurred at levels of exposure far below those that produced clinical signs or symptoms in their mothers. * Therefore, health guidance values for methylmercury, such as ATSDR's chronic oral minimal risk level (MRL MRL Medical Record Librarian; now called Medical Record Administrator. MRL maximum residue limit. ), have been set at levels that would protect fetuses. * Since adults are less sensitive than fetuses, chronic intakes within an order of magnitude A change in quantity or volume as measured by the decimal point. For example, from tens to hundreds is one order of magnitude. Tens to thousands is two orders of magnitude; tens to millions is three orders of magnitude, etc. of the MRL generally have been considered to represent no adult health risk. * This article considers a case of suspected mercury intoxication in a 53-year-old woman. * The woman did not work in a profession in which exposure to mercury might be expected to occur. * She had no hobbies, activities, or medical conditions that might bring her into contact with mercury. * She had, however, been eating fish on a daily basis for the past 10 years. * She had routinely eaten one or two fish meals each day, at least six days a week. * Two years after beginning the high-fish diet, she consulted a physician for treatment of erythema erythema (ĕr'əthē`mə), more or less diffuse redness of the skin due to concentration of an abnormally large amount of blood within the small vessels of the skin (hyperemia), as in burns. (reddened skin). * Analysis of a hair sample revealed a hair mercury concentration of 67.8 parts per million parts per million mg/kg or ml/l; see ppm. (ppm). * Average concentrations among U.S. adults have been reported to range from 0.47 to 3.8 ppm. * Several years later, she began to experience symptoms that included stomatitis Stomatitis Definition Inflammation of the mucous lining of any of the structures in the mouth, which may involve the cheeks, gums, tongue, lips, and roof or floor of the mouth. , tremors, and ringing in the head and ears. * This case study suggests that some individuals might be susceptible to adverse health impacts of methylmercury at intakes just 7 to 15 times the MRL. This department, "Practical Stuff!" originated from you, our readers. Many of you have expressed to us that one of the main reasons you read the Journal of Environmental Health is to glean practical and useful information for your everyday work-related activities. In response to your feedback, we dedicate this section to you with salient points to remember about two to three articles in each issue. |
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