The Relationship between Blood Levels and Dose of Methylmercury in Man

Kershaw, Thomas G.; Dhahir, Patricia H.; Clarkson, Thomas W.

doi:10.1080/00039896.1980.10545720

Cited by 36 publications

(53 citation statements)

References 5 publications

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“…Similar findings were reported from an experimental test in human volunteers in a study in Finland (13). Our observations on blood levels in subjects ingesting known amounts of methylmercury in fish were consistent with a high efficiency ofabsorption [more than 90% of the ingested amount (14)]. …”

Section: Disposition Of Methylmercurysupporting

confidence: 67%

“…Our observations on six subjects ingesting a single low dose (14) and on Iraqi mothers exposed for many months (26) yielded almost identical average half-times of about 50 days. These values are in agreement with those reported by Miettinen et al (13) in young adult males taking a single oral dose ofradiolabeled methyl mercury.…”

Section: Disposition Of Methylmercurymentioning

confidence: 57%

“…The study by Kershaw et al (14) showed that distribution to the blood compartment was complete in about 30 hr and accounted for 7 % of the ingested dose. Earlier work in Sweden using radiolabeled methylmercury indicated that distribution to the brain took longer, about 3 days (15).…”

Section: Disposition Of Methylmercurymentioning

confidence: 99%

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Mercury: major issues in environmental health.

Clarkson

1993

Environ Health Perspect

455

185

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In the past, methylmercury compounds were manufactured as fungicides or appeared as unwanted byproducts of the chemical industry, but today the methylation of inorganic mercury in aquatic sediments and soils is the predominant if not the sole source of methylmercury. This form of mercury is bioaccumulated to a high degree in aquatic food chains to attain its highest concentrations in edible tissues in long-lived predatory fish living in both fresh and ocean waters. It is well absorbed from the diet and distributes within a few days to all tissues in the body. It crosses without hindrance the blood-brain and placental barriers to reach its principal target tissue, the brain. It is eliminated chiefly in the feces after conversion to inorganic mercury. The biological half-time of methylmercury in human tissues is about 50 days, but there is wide individual variation. Adult poisoning is characterized by focal damage to discrete anatomical areas of the brain such as the visual cortex and granule layer of the cerebellum. A latent period of weeks or months may ensue before the appearance of signs and symptoms of poisoning. The latter manifest themselves as paresthesia, ataxia, constriction of the visual fields, and hearing loss. The prenatal period is the most sensitive stage of the life cycle to methylmercury. Prenatally poisoned infants exhibit a range of effects from severe cerebral palsy to subtle developmental delays. Methylmercury is believed to inhibit those processes in the brain specially involved in development and growth such as neuronal cell division and migration.

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Section: Disposition Of Methylmercurysupporting

confidence: 67%

Section: Disposition Of Methylmercurymentioning

confidence: 57%

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Mercury: major issues in environmental health.

Clarkson

1993

Environ Health Perspect

455

185

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“…Studies that have compared mercury maternal hair levels with mercury blood levels have produced various ratios ranging from 140 to 415 ( Berglund et al, 1971;Birke et al, 1972;Den Tonkelaar et al, 1974;Kershaw et al, 1980;Sherlock et al, 1982;Davidson et al, 1995 ). Within this range of ratios ( which differ by approximately three ), the most frequently used value has been 250.…”

Section: Results /Discussionmentioning

confidence: 99%

Exposure analysis of five fish-consuming populations for overexposure to methylmercury

Mariën

Patrick

2001

J Expo Sci Environ Epidemiol

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Mercury, in the form of methylmercury, is found in a myriad of fish species consumed by recreational and subsistence fishers around the world. Many agencies have attempted to address the issue of mercury consumption, resulting at times in the placement of advisories on waterways used for fishing. In this study, consumption rates of three Native American populations and two recreational fishing populations consuming freshwater or saltwater fish species were examined. These consumption rates were combined with fish contamination data to assess the level of exposure to methylmercury and to determine if any of these populations exceed a derived tolerable daily intake ( TDI ) for methylmercury ( 0.035 to 0.08 g / kg / day ) . The TDI is unlikely to result in adverse health effects and is based on scientific studies investigating sensitive endpoints in children of mothers who consume fish over prolonged periods of time. Results from the exposure analysis indicate that many within the Native American populations exceed the TDI. This occurs even though the mercury concentrations in certain fish species are comparable to concentrations found in fish from open waters where``background'' levels are assumed. Recreational anglers consuming freshwater species have exposure levels below the TDI as do nearly all anglers consuming saltwater species. Similar populations or populations having comparable consumption patterns of fish with equal or higher mercury levels in other areas will also exceed the TDI level for mercury. The public health implications of this exposure analysis are discussed.

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“…Some of the released Hg 2+ is biotransformed by microbial methylation to form CH 3 Hg + , which humans are exposed to via the consumption of contaminated water and/or food (ATSDR, 2003). Over 90′ of ingested CH 3 Hg + is absorbed by the gastrointestinal tract (Kershaw et al, 1980). After…”

Section: Introductionmentioning

confidence: 99%

Transport of thiol-conjugates of inorganic mercury in human retinal pigment epithelial cells

Bridges¹,

Battle²,

Zalups³

2007

Toxicology and Applied Pharmacology

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Inorganic mercury (Hg 2+ ) is a prevalent environmental contaminant to which exposure to can damage rod photoreceptor cells and compromise scotopic vision. The retinal pigment epithelium (RPE) likely plays a role in the ocular toxicity associated with Hg 2+ exposure in that it mediates transport of substances to the photoreceptor cells. In order for Hg 2+ to access photoreceptor cells, it must be first be taken up by the RPE, possibly by mechanisms involving transporters of essential nutrients. In other epithelia, Hg 2+ , when conjugated to cysteine (Cys) or homocysteine (Hcy), gains access to the intracellular compartment of the target cells via amino acid and organic anion transporters. Accordingly, the purpose of the current study was to test the hypothesis that Cys and Hcy S-conjugates of Hg 2+ utilize amino acid transporters to gain access into RPE cells. Time-and temperaturedependence, saturation kinetics, and substrate-specificity of the transport of Hg 2+ , was assessed in ARPE-19 cells exposed to the following S-conjugates of Hg 2+ : Cys (Cys-S-Hg-S-Cys), Hcy (Hcy- S-Hg-S-Hcy), N-acetylcysteine (NAC-S-Hg-S-NAC) or glutathione (GSH-S-Hg-S-GSH).We discovered that only Cys-S-Hg-S-Cys and Hcy-S-Hg-S-Hcy were taken up by these cells. This transport was Na + -dependent and was inhibited by neutral and cationic amino acids. RT-PCR analyses identified systems B 0,+ and ASC in ARPE-19 cells. Overall, our data suggest that Cys-SHg-S-Cys and Hcy-S-Hg-S-Hcy are taken up into ARPE-19 cells by Na-dependent amino acid transporters, possibly systems B 0,+ and ASC. These amino acid transporters may play a role in the retinal toxicity observed following exposure to mercury.

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The Relationship between Blood Levels and Dose of Methylmercury in Man

Cited by 36 publications

References 5 publications

Mercury: major issues in environmental health.

Mercury: major issues in environmental health.

Exposure analysis of five fish-consuming populations for overexposure to methylmercury

Transport of thiol-conjugates of inorganic mercury in human retinal pigment epithelial cells

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