Fish consumption mercury exposure

Bengt-Goran S, Nilsson A, Jonsson E, et al. 1995. Fish consumption and exposure to persistent organochlorine compounds, mercury, selenium and methylamines among Swedish fishermen. Scand J Work Environ Health 21(2) 96-105. 

Levy M, Schwartz S, Dijak M, Weber JP, Tardif R, Rouah F (2004) ChUdhood urine mercury excretion dental amalgam and fish consumption as exposure factors. Environ Res 94 283-290... 

Human intake of total mercury from the diet normally ranges between 7 and 16 pg daily (Schumacher et al. 1994 Richardson et al. 1995). Fish consumption accounts for much of this exposure in the form of methylmercury 27% of the intake, and 40% of the absorbed dose. Intake of inorganic mercury arises primarily from foods other than fish, and is estimated at 1.8 pg daily with 0.18 pg absorbed daily (Richardson etal. 1995). In certain areas of India, blood mercury concentrations of people who ate fish were three to four times higher than non-fish eaters (Srinivasen and Mahajan 1989). In some countries, mercury in dental amalgams accounts for 2.8 pg daily, equivalent to as much as 36% of the total mercury intake and 42% of the absorbed dose (USPHS... 

In the late 1950s the subtle and serious consequences of methyl mercury exposure became evident in Minamata, Japan. Initially, early signs of uncoordinated movement and numbness around the lips and extremities, followed by constriction in visual fields in fishermen and their families, baffled health experts. Developmental effects were clearly evident in infants who exhibited subtle to severe disabilities. This spectrum of adverse effects was finally related to methyl mercury exposure from consumption of contaminated fish. Minamata Bay was contaminated with mercury and methyl mercury from a factory manufacturing the chemical acetaldehyde. Mercury was used in the manufacturing process, which also resulted in both mercury and methyl mercury being discharged into Minamata Bay. The fish in the bay accu-... 

The primary human exposure to methyl mercury is from consumption of contaminated fish. The most sensitive population is the developing fetus or infant due to the effects of methyl mercury on the nervous system (neurotoxic) and developmental effects. Exposure limits and fish consumption advisories are directed at pregnant women, women of childbearing age, and children. All agencies also recognize that fish consumption has many nutritional benefits and is an important part of many people s diet. Nevertheless, the widespread distribution of mercury and subsequent bioaccumulation of methyl mercury requires that many agencies have developed recommendation for levels of mercury in fish. Below is a list of some of these recommendations, but it is very important to consult the local fish consumption advisories. 

Myers, G.J., P.W. Davidson, C. Cox, C.F. Shamlaye, D. Palumbo, E. Cernichiari, J. Sloane-Reeves, G.E. Wilding, J. Kost, L.S. Huang, and T.W. Clarkson. 2003. Prenatal methyl mercury exposure from ocean fish consumption in the Seychelle child development study. Lancet 361(9370) 1686-1692. 

The main sources of exposure to mercury for the general population are from the diet and dental amalgam.21,28 The main dietary source of mercury is fish and this has led to interest in potential exposure to mercury on the neurological development of children from populations with high fish consumption.29 There is no statutory control of mercury in most food in the UK, but the levels of mercury in fish are controlled by European Commission Decision 93/351/EEC which sets an average limit for mercury in fish of 0.5 mg/kg or 0.5 ppm (part per million).30 This average limit is, however, increased to 1.0 mg/kg or 1 ppm for the edible parts of the predatory and bottom-dwelling species listed in the Annex to the Decision. 

Dickman, M.D., Leung, K.M.C., 1998. Mercury and organochlorine exposure from fish consumption in Hong Kong. Chemosphere 37, 991-1051. 

Studies from New Zealand and the Faroe Island indicate that adverse effects in children can be correlated with maternal hair levels as low as 10-20 pg/g [44]. Mercury analyses conducted on a single human hair can be used to monitor daily variations in methyl mercury exposure among fish eaters [45,46], and have been utilized to track maternal fish consumption and risk of preterm delivery [47]. Other investigators [48] have utilized measurements of total mercury in hair, toenails and urine to assess exposures in a group of non-occupationally exposed women in relation to renal tubular effects. 

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). 

Mercury can be used for the extraction of gold. In hospitals and homes, it is still used in thermometers and blood-pressure cuffs, can be found in batteries, switches, and fluorescent light bulbs. Large amounts of metallic mercury are employed as electrodes in the electrolytic production of chlorine and sodium hydroxide from saline. Today, exposure of the general population comes from three major sources fish consumption, dental amalgams, and vaccines. 

Concerning interactions with other chemicals, there is an ongoing debate about the value of fish in the diet versus the risk from increased exposure to methylmercury that may be in the fish. One recent study reported a beneficial effect from increased fish consumption even though mercury body burdens were increased to some extent (Davidson et al. 1998). One possible factor in the fish that could improve health is omega 3-fatty acid. Children and adults both benefit from a healthy diet, but there may more emphasis on the benefits to growing children. Other interactions for mercury include the effect of various substances on its gastrointestinal absorption (e.g., iron, zinc) or possibly protective effects from prevention or repair of mercury related oxidative damage (e.g., interactions with selenium as an antioxidant). No information was identified that specifically addresses differences in these interactions for children compared to adults. 

Egeland GM, Middaugh JP. 1997. Balancing fish consumption benefits with mercury exposure. 

Carta P, Flore C, Alinovi R, et al. Sub-clinical neurobehavioral abnormalities associated with low level of mercury exposure through fish consumption. Neurotoxicology2002 24(4-5) 617—23. 

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