Shellfish mercury

Fig. 15-8 The mercury cycle, demonstrating the bioaccumulation of mercury in fish and shellfish. Reprinted with permission from An Assessment of Mercury in the Environment" (1978) by the National Academy of Sciences, National Academy Press, Washington, DC.

The Ebro catchment is the largest river basin in Spain. It covers an area of 85,362 km2 (http //www.chebro.es) and receives the potential influence of three million people. It suffers a considerable ecological impact from different industrial activities located predominantly in the last third of its course. These activities result on the release to the Ebro River and to some of its tributaries of Tm quantities of chlorinated organic compounds, PBDE and other brominated flame retardants, mercury, and other metals. In addition, intensive agricultural practices, mainly concentrated in the last 30 km of the river course and in its Delta, imply the use of large quantity of pesticides and fertilizers. In this paper, we review physiological effects of these pollutants in resident fish and shellfish populations and provide a general picture of the health status of the low course of the Ebro River. 

Tokuyama Bay, Japan, received 6.6 metric tons of mercury wastes between 1952 and 1975 in wastewater from two chloralkali plants, although sediment analysis suggests that as much as 380 tons of mercury were released (Nakanishi et al. 1989). Unlike Minamata Bay, however, there were no human sicknesses reported, and the hair of residents contained 0 to 5 mg Hg/kg FW vs. 15 to 100 mg Hg/kg FW in Minamata residents. In 1970, a maximum concentration of 3.3 mg total Hg/kg FW was reported in tissues of Squilla, a crustacean. In 1973, a health safety limit was set of 0.4 mg total Hg/kg FW in edible fish and shellfish tissues with a maximum of 0.3 mg methyl-mercury/kg FW permitted at least five species of fish had more than 0.4 mg total Hg/kg FW, and fishing was prohibited. Contaminated sediments (>15 mg total Hg/kg) were removed by dredging and reclamation between 1974 and 1977. By 1979, the mercury content of all fish, except one species, was less than 0.4 mg total Hg/kg FW fishing was prohibited. By 1983, all fish and shellfish contained less than 0.4 mg Hg/kg FW and fishing was allowed (Nakanishi et al. 1989). 

Fujiki, M. 1963. Studies on the course that the causative agent of Minamata disease was formed, especially on the accumulation of the mercury compound in the fish and shellfish of Minamata Bay. Jour. Kumamoto Med. Soc. 37 494-521. 

Holden, A.V. 1973. Mercury in fish and shellfish, a review. Jour. Food Technol. 8 1-25. 

In the 1960s, organic residues (e.g. DDT, PCBs, methyl mercury) began to be detected in several species of shellfish, fish and fish-eating birds [1,2]. Since then, assessment of the bioaccumulation of chemicals has been considered decisive for determining the potential hazard and environmental risk it is regulated by various official organisations such as the OECD [3], EPA [4,5] and ASTM [6],... 

The particular form of mercury that accumulates in fish or shellfish, methylmercury, has been the subject of extensive investigations in recent years, and results from these studies tell us much about the potential some chemicals have for interfering with the highly sensitive processes that are at work to build the nervous system during the developmental period of life. We shall come back to this subject later, when the subject of developmental toxicity is covered. 

Methylmercury, which we referred to in the neurotoxicity section, occurs in fish and shellfish found in both the ocean and fresh water systems. The mercury that is the source of methylmercury arises from power plant emissions and industrial processes. Some even comes from... 

Since the late 1960 s problems related to ccxitaminaticxi of fish and shellfish have been recognized. The problem compounds share one characteristic biopersistence. Compounds such as various salts of lead or mercury have contaminated shellfish or fish living in either fresh or salt water. Chlorinated compounds such as DDT, PCB and dioxins have been found in fish living in fresh water rivers and lakes and to some extent in the Baltic and Mediterranean Seas (25). 

Despite its availability and current use, coal is not as widely used today as the other fossil fuels. Coal s major weakness is that it does not burn cleanly. It often contains trace amounts of other elements, including mercury, arsenic, and sulfur, and when it burns, it releases these toxic substances into the air. Over time, coal pollution builds up in the environment. Mercury released during coal combustion, for example, settles in water and builds up in the bodies of fish and shellfish. When these fish and shellfish are eaten by humans and other animals, harmful amounts of mercury can be ingested. In 2008, bluefm tuna served in expensive New York restaurants was found to contain unacceptably high levels of mercury. These fish eat smaller organisms in the ocean, and when these small organisms contain mercury, the toxic element becomes concentrated in the body of the tuna. 

B. Gagnaire, H. Thomas-Guyon and T. Renault, In vitro effects of cadmium and mercury on Pacific oyster, Crassostrea gigas (Thunberg), Haemocytes, Fish Shellfish, 16 (2004) 501-512. 

Mercury. In Japan in the 1950s and 1060s, wastes from a chemical and plastics plant containing mercury were discharged into Minamata Bay. The mercury was converted to the readily absorbed methylmercury by bacteria in the aquatic sediments. Consumption of fish and shellfish by the local population resulted in numerous cases of mercury poisoning, or Minamata disease. By 1970, at least... 

Mercury can be present in shellfish as mercury metal, inorganic mercury salts or as organomercury compounds. 

The analyst has used an analytical method to determine the concentration of mercury in a sample of shellfish. The analytical method chosen might measure total mercury (the metal mercury and all its compounds) or it might only measure certain mercury species e.g. mercury(II) salts, organomercury compounds). Therefore, the method chosen may have a significant effect on the mercury concentration found in the sample. 

Potential sources of human exposure to mercury include food contaminated with mercury, inhalation of mercury vapors in ambient air, and exposure to mercury through water, soil and sediment. Dietary intake is by far the most important source of exposure to mercury for the general population. Fish and other seafood products are the main source of methylmercury in the diet studies have shown that methylmercury concentrations in fish and shellfish are 10-100 times greater than in other foods, including cereals, potatoes, vegetables, fruits, meats, poultry, eggs, and milk. As of December 1998, mercury was the chemical contaminant responsible, at least in part, for the issuance of 1931 fish consumption advisories by 40 states, including the US territory of American Samoa. Almost 68% of all advisories issued in the United States are a result of mercury contamination in fish and shellfish. Advisories for mercury have increased steadily by 115% from 899 advisories in 1993 to 1931 advisories in 1998. The number of states that have issued mercury advisories also has risen steadily from 27 states in 1993 to 40 states in 1997, and remains at 40 states for 1998. Advisories for mercury increased nearly 8% from 1997 (1782 advisories) to 1998 (1931 advisories). 

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