Methyl mercury in fish

Methyl mercury (MeHg) may be directly released in the environment (e.g. in Mina-Mata, Japan, from poly-vinyl wastes) or originate from the biomethylation of 

In view of the urgent need for the improvement of the quality of the analyses, a project for MeHg has been discussed and designed with a group of experts in the frame of the BCR-Programme. The programme of work was set up in the form of an improvement scheme (see Chapter 12). In particular, the various steps of the analytical methods were studied individually by each of the participants e.g. extraction, clean-up and separation. This improvement scheme is fully described in Chapter 12 the present section gives a summary of this certification of tuna fish, which followed the interlaboratory studies. 

The freeze-dried materials were sent to the Joint Research Centre of Ispra where they were ground using a mill equipped with zirconium dioxide balls. The ground materials were sieved using a vibrating stainless steel sieve. The fractions with particles larger than 125 pm were discarded and the remaining materials were stored in polyethylene 

The between bottle homogeneity was verified by the determination of total and methyl mercury on sample intakes of 0.2 g. For the determination of total mercury, the samples were mineralised by digestion using nitric acid. The final determination was performed by CVAAS. Methyl mercury was determined by CGC/ECD after extraction of 0.2 g fish powder in toluene, back extraction with a cysteine acetate solution and further extraction with toluene. Calibrations were performed by standard additions. The study showed that the two materials are homogeneous at an analytical portion of 0.2 g and above for total and methyl mercury [7]. 

Bottles were kept at respectively -20°C, +20°C and +40°C over a period of 12 months and total and methyl mercury were determined at regular intervals during the storage period. No instability could be demonstrated [7], 

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In a report from the U.S. EPA (1980), fish contained between 10,000 and 100,000 times the concentration of methyl mercury present in ambient water. In a study of methyl mercury in fish from different oceans, higher levels were reported in predators than in nonpredators (see Table 8.2). Taken overall, these data suggest that predators have some four- to eightfold higher levels of methyl mercury than do nonpredators, and it appears that there is marked bioaccumulation with transfer from prey to predator. 

Fimreite N, Holsworth WN, Keith JA, Pearce PA, Qruchy IM. 1971. Methyl mercury in fish and fish-eating birds from sites of industrial contamination in Canada. Can Field Natural 85 2211-2220. 

The primary concern with organic mercury is methyl mercury in fish. Children and women of childbearing age should be cautious about consuming fish known to accumulate mercury such as tuna, shark, swordfish, and pike. Local fish consumption advisories should be followed. 

Determination of methyl mercury in fish tissue using electrochemical glucose oxidase biosensors based on invertase inhibition... 

Knowing that the inorganic mercury is biomagnified in the aquatic food chain through bacterial conversion to methyl mercury and then accumulated primarily in fish, this part is focused to the determination of methyl mercury in fish samples. The developed method described above using the combination of biphasic system and glucose oxidase biosensor was used. 

Berglund F, Berlin M, Birke G, et al. 1971. Methyl mercury in fish. A toxicologic-epidemiologic evaluation of risks. Report from an expert group. Nordisk Hygienisk Tidskrift. Supplementum 4. Stockholm. 

Clarkson TW, Strain JJ. Nutritional factors may modify the toxic action of methyl mercury in fish-eating populations. J Nutr 2003 133(5 Suppl 1) 1539S-43S. 

Newbeme, P.M., O. Glaser, L. Friedman, and B.R. Stillings. 1972. Chronic exposure of rats to methyl mercury in fish protein. Nature 237(5349) 40-41. 

Hight, S.C. and Capar, S.G. (1983) Electron capture gas-liquid chromatographic determination of methyl mercury in fish and shellfish Collaborative study. J. Assoc. Off. Anal. Chem., 66,1121-1128. 

Kamps, L. and McMahon, B. (1972) Utilization of the West procedure for the determination of methyl mercury in fish by gas-liquid chromatography. JAOAC, 55, 590-595. 

Velghe, N. Campe, A. and Claeys, A. (1978b) Semi-automated cold vapor determination of inorganic and methyl mercury in fish by direct injection of tissue in the aeration cell. Atom. Abs. Newsl., 17,139-143. 

There is now a considerable effort going into studying the factors involved in the variation of mercury concentration in freshwater fish in remote areas (6,24). Such studies will require an examination of often quite small differences in the many factors which contribute to the bio-accumulation of methyl mercury in fish. This will involve the determination of mercury and its forms and other species involved in the transport of mercury through to its uptake as methyl mercury in fish. Clearly, the sampling and analytical techniques, used in studying differences in background areas require to be much more refined than for a comparison of mercury levels in sediments, upstream and downstream from a point source. For instance, the concentration of mercury in water is measured in units of ng/liter (ppt), units one millionth the size of ppm, the units normally used for expressing concentration of mercury in fish and water. 

Berglund F, Berlin M, Birke G, von Euler U, Friberg L, Holmstedt B, Jonsson E, Ramel C, Skerfving S, Swensson A, Tejning S (1971) Methyl mercury in fish, a toxicologic-epidemiologic evaluation of risks. Report from an expert group. Nord. Hyg. T., suppl. 4 (publ. in Nord. Hyg. T., suppl 3, 1970 - Swedish)... 

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