I did a compilation of what I considered to be relevant research on the possible side effects of low level chronic mercury intake and guidelines for fish comsumption. I think at this point it's perfectly justified to advise against fish intakes like 3-4 cans of tuna per day.
89% of fish eaters in study number one had mercury levels above the recommended.(1)
Poor performance in motor skills tests in people with high fish intakes.(9,16)
Fish eaters have a 62% higher risk of major pathological syndromes (2). Shame it doesn't specify the quantities they ate in the abstract.
Higher levels of mercury in the hair of subfertile Japanese males.(11)
Fisheaters performed significantly more poorly on tests requiring cognitive flexibility. (12)
Adverse effects in children after 7 years elapsed from pre natal mercuty comsumption. (13)
Guidelines for safe amounts of methylmercury intake trough fish needs further research. (3)
No suppression of imune system in fish eaters but some was observed in people subjected to low levels chronic occupational exposure.(14)
It would be interesting to know how do their levels compare to people eating 3 cans of tuna daily.
Fish eating can lead to mercury levels above the recommended. (18)
Possible allergy triggering by mercury.(17)
Information on methylmercury levels for different species, no tuna though. (5)
Concern of mercury posoning trough fish comsumption might be of some concern.(6)
Single meal guidelines for mercury contents. (7)
Adverse effects at levels previously considered safe.(8)
1-Mercury levels in high-end consumers of fish.
Hightower JM, Moore D.
California Pacific Medical Center, California Pacific Medical Center, San Francisco, California, USA.
Consumption of food containing mercury has been identified as a health risk. The U.S. Environmental Protection Agency (U.S. EPA) and the National Academy of Sciences recommend keeping the whole blood mercury level < 5.0 micro g/L or the hair level < 1.0 micro g/g. This corresponds to a reference dose (RfD) of 0.1 micro g/kg body weight per day. All patients in a 1-year period ((italic)n(/italic) = 720) who came for an office visit in a private internal medicine practice in San Francisco, California, were evaluated for mercury excess using the current RfD. One hundred twenty-three patients were tested (93 females, 30 males). Of these, data were statistically analyzed for 89 subjects. Mercury levels ranged from 2.0 to 89.5 micro g/L for the 89 subjects. The mean for 66 women was 15 micro g/L [standard deviation (SD) = 15], and for 23 men was 13 micro g/L (SD = 5); 89% had levels exceeding the RfD. Subjects consumed 30 different forms or types of fish. Swordfish had the highest correlation with mercury level. Sixty-seven patients with serial blood levels over time after stopping fish showed a decline in mercury levels; reduction was significant ( (italic)p(/italic) < 0.0001). A substantial fraction of patients had diets high in fish consumption; of these, a high proportion had blood mercury levels exceeding the maximum level recommended by the U.S. EPA and National Academy of Sciences. The mean level for women in this survey was 10 times that of mercury levels found in a recent population survey by the U.S. Centers for Disease Control and Prevention. Some children were > 40 times the national mean.
2-[Assessment of health risks upon exposure to methylated mercury]
[Article in Russian]
D'iakovich MP, Efimova NV.
Accumulation of a toxic agent (2-4-fold maximum allowable concentrations) was found in the fish caught in the polluted area of the water storage basin of the Angara river. The authors quantified a risk for major pathological syndromes in individuals exposed to mercury on fish ingestion and assayed biosubstrates for the substance. The integral risk of major pathological syndromes in the potentially mercury loaded persons increased by 62.1% with age and only by 17.1% in the control group. In the risk pattern there were risks for neurological diseases, arterial hypertension, coronary heart disease, borderline mental disorders, and endocrine diseases.
3-Neurotoxicity and molecular effects of methylmercury.
Castoldi AF, Coccini T, Ceccatelli S, Manzo L.
University of Pavia and "Salvatore Maugeri" Foundation, Pavia, Italy. firstname.lastname@example.org
The neurotoxicity of high levels of methylmercury (MeHg) and the high susceptibility of the developing brain are well established both in humans and experimental animals. Prenatally poisoned children display a range of effects varying from severe cerebral palsy to subtle developmental delays. Still unknown is the lowest dose that impairs neurodevelopment. The primary source of human exposure is the fish. The data obtained so far from epidemiological studies on fish-eating populations are not consistent. A reference dose of 0.1 microg MeHg/kg per day has been established by the U.S. Environmental Protection Agency based on a study on Iraqi children exposed to MeHg in utero. However, these exposures occurred at high level for a limited period of time, and consequently were not typical of lower chronic exposure levels associated with fish consumption. Major obstacles for estimation of a threshold dose for MeHg include the delayed appearance of the neurodevelopmental effects following prenatal exposure and limited knowledge of cellular and molecular processes underlying these neurological changes. In this respect, a strategy which aims at identifying sensitive molecular targets of MeHg at environmentally relevant levels may prove particularly useful to risk assessment. Here some examples of MeHg molecular effects occurring at low doses/concentrations are presented.
4-Toxicology and immunotoxicology of mercury: a comparative review in fish and humans.
Sweet LI, Zelikoff JT.
Department of Environmental and Industrial Health, School of Public Health, University of Michigan, Ann Arbor, Michigan, USA. Isweet@umich.edu
This review addresses an important area of environmental and mammalian toxicology by evaluating and comparing mercury-induced effects upon the immune responses of two evolutionarily divergent yet immunologically-related species. The mechanisms of mercury toxicology and immunotoxicology are described herein, including supporting data from the following: sources of exposure; bioavailability and biodistribution; metabolism; and laboratory and field investigations. Based upon the studies presented, the relative sensitivities of fish and human immune cells to mercury exposure are compared and contrasted with regard to mercury's ability to stimulate and/or suppress host immunocompetence. In addition, results from immune assays are compared to mercury tissue burdens, as well as to toxicological threshold level estimates. Such comparisons may help to resolve gaps in our knowledge regarding sensitivity of immunological assays, standardization of immunotoxicological techniques between species, and the extent to which the vertebrate immune system possesses functional reserve and redundancy in response to xenobiotics. A review of this type begins to provide support for the potential usefulness of fish immune cells to serve as indicators for human immunotoxicology risk assessment. Analysis of the reviewed studies supports the following conclusions in both lower and higher vertebrates: a threshold for mercury-induced immunotoxicological effects is likely; multiple exposure scenarios involving high and/or chronic exposures leading to increased body burdens are linked to increased risk of immunomodulation; and highly exposed and/or susceptible subpopulations are at greater risk of toxicological impact.
5-Fish for human consumption: risk of contamination by mercury.
Storelli MM, Marcotrigiano GO.
Instituto di Chimica-Facolta di Medicina Veterinaria, Universita di Bari, Italy.
Total mercury concentrations were measured in the muscle of different kinds of fish: megrim (Lepidorhombus boscii), common sole (Solea vulgaris), striped mullet (Mullus barbatus), anglerfish (Lophius piscatorius), and black-bellied angler (Lophius budegassa), caught in the South Adriatic Sea (South Italy). The highest total mercury levels were found in anglerfish (0.61-2.22 mg/kg wet wt, mean 1.26 +/- 0.58), followed by black-bellied angler (0.22-1.62 mg/kg wet wt, 0.68 +/- 0.36), megrim (0.05-0.92 mg/kg wet wt, 0.39 +/- 0.30), striped mullet (0.10-0.63 mg/kg wet wt, 0.31 +/- 0.13) and common sole (0.05-0.44 mg/kg wet wt, 0.19 +/- 0.15). According to current regulations, 62.5% of anglerfish (Lophius piscatorius) and 23% of black-bellied angler (Lophius budegassa) samples showed concentrations exceeding the peak value of 1 mg/kg, while only 25% of samples of megrim (Lepidorhombus boscii), and 8.3% of striped mullet (Mullus barbatus), exceeded the peak value fixed at 0.5 mg/kg. Correlations between total mercury concentration and specimen weight were evident in all the species examined.
6-Recent advances in recognition of low-level methylmercury poisoning.
Division of Exposure Assessment Coordination and Policy, United States Environmental Protection Agency, Washington, District of Columbia 20460, USA. email@example.com
Clinically evident neurologic damage from methylmercury exposure was well described following poisoning episodes in Japan and Iraq several decades ago. Paresthesias have been considered to be an early effect; however, additional data raise questions about whether this is the most sensitive adverse effect among adults. Fetuses are considered the most sensitive subpopulation because of the vulnerability of the developing nervous system. Over the past 5 years questions have been raised about what is an appropriate level of exposure for sensitive groups. A recent evaluation by a committee for the US National Research Council found that 0.1 microg/kg body weight per day is a scientifically justified level of methylmercury exposure for maternal-fetal pairs. The conclusions of this report and other issues are discussed in the present review. Because of anthropogenic release of mercury into the environment, methylmercury exposure from fish consumption is a pathway that is of increasing concern.
7-Development of a single-meal fish consumption advisory for methyl mercury.
Ginsberg GL, Toal BF.
State of Connecticut, Department of Public Health, Division of Environmental Epidemiology and Occupational Health, Hartford, CT 06134-0308, USA.
Methyl mercury (meHg) contamination of fish is the leading cause of fish consumption advisories in the United States. These advisories have focused upon repeated or chronic exposure, whereas risks during pregnancy may also exist from a single-meal exposure if the fish tissue concentration is high enough. In this study, acute exposure to meHg from a single fish meal was analyzed by using the one-compartment meHg biokinetic model to predict maternal hair concentrations. These concentrations were evaluated against the mercury hair concentration corresponding to the U.S. Environmental Protection Agency's reference dose (RfD), which is intended to protect against neurodevelopmental effects. The one-compartment model was validated against blood concentrations from three datasets in which human subjects ingested meHg in fish, either as a single meal or multiple meals. Model simulations of the single-meal scenario at different fish meHg concentrations found that concentrations of 2.0 ppm or higher can be associated with maternal hair concentrations elevated above the RfD level for days to weeks during gestation. A single-meal fish concentration cutoff of > or = 2.0 ppm is an important consideration, especially because this single high exposure event might be in addition to a baseline meHg body burden from other types of fish consumption. This type of single-meal advisory requires that fish sampling programs provide data for individual rather than composited fish, and take into account seasonal differences that may exist in fish concentrations.
8-Methylmercury: a new look at the risks.
National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC 20074, USA. firstname.lastname@example.org
In the US, exposure to methylmercury, a neurotoxin, occurs primarily through consumption of fish. Data from recent studies assessing the health impact of methylmercury exposure due to consumption of fish and other sources in the aquatic food web (shellfish, crustacea, and marine mammals) suggest adverse effects at levels previously considered safe. There is substantial variation in human methylmercury exposure based on differences in the frequency and amount of fish consumed and in the fish's mercury concentration. Although virtually all fish and other seafood contain at least trace amounts of methylmercury, large predatory fish species have the highest concentrations. Concerns have been expressed about mercury exposure levels in the US, particularly among sensitive populations, and discussions are underway about the standards used by various federal agencies to protect the public. In the 1997 Mercury Study Report to Congress, the US Environmental Protection Agency summarized the current state of knowledge on methylmercury's effects on the health of humans and wildlife; sources of mercury; and how mercury is distributed in the environment. This article summarizes some of the major findings in the Report to Congress and identifies issues of concern to the public health community.
9-Neurotoxic effects of low-level methylmercury contamination in the Amazonian Basin.
Lebel J, Mergler D, Branches F, Lucotte M, Amorim M, Larribe F, Dolbec J.
Centre pour l'Etude des Interactions Biologiques entre la Sante l'Environnement (CINBIOSE), Universite du Quebec a Montreal, Canada. email@example.com
Many studies have demonstrated mercury contamination in the Amazonian ecosystem, particularly in fish, a dietary mainstay of populations in this region. The present study focused on potential health effects of this low-level methylmercury exposure. The study was carried out in a village on the Tapajos River, a tributary of the Amazon, on 91 adults inhabitants (15-81 years), whose hair mercury levels were inferior to 50 mu/g. Performance on a neurofunctional test battery and clinical manifestations of nervous system dysfunction were examined in relation to hair mercury concentrations. Near visual contrast sensitivity and manual dexterity, adjusted for age, decreased significantly with hair mercury levels (P < 0.05), while there was a tendency for muscular fatigue to increase and muscular strength to decrease in women. For the most part, clinical examinations were normal, however, hair mercury levels were significantly higher (P < 0.05) for persons who presented disorganized movements on an alternating movement task and for persons with restricted visual fields. These results suggest dose-dependent nervous system alterations at hair mercury levels below 50 micrograms/g, previously considered a threshold for clinical effects. The profile of dysfunction in this adult population is consistent with the current knowledge on methyl-mercury poisoning. The long-term implications of these findings are unknown and need to be addressed.
10-Preliminary evidence of neurotoxicity associated with eating fish from the Upper St. Lawrence River Lakes.
Mergler D, Belanger S, Larribe F, Panisset M, Bowler R, Baldwin M, Lebel J, Hudnell K.
Universite du Quebec a Montreal, Canada.
Pollution of hydrographic basins has affected the flora and fauna that thrive in these aquatic ecosystems, and fish, which constitute an important food resource, often contain a plethora of potentially toxic chemicals. In a major research project on early neurotoxic effects of environmental exposure to manganese among residents in Southwest Quebec, fish consumption from 2 lakes of the Upper St. Lawrence River System, was surveyed as a potential confounding factor. Participants were selected using a random, stratified sampling strategy from lists of the Quebec Health Plan. Following exclusions, 273 men and women between 20-69 years were retained for the present analysis. A total of 103 (37.7%) reported eating fish from the Upper St. Lawrence. Although fisheaters and non-fisheaters were similar for most socio-demographic variables, significantly more fisheaters (65.2%) reported consuming alcoholic beverages as compared to non-fisheaters (42.4%) (Chi Sq. <0.01). To eliminate this possible bias, fisheaters were matched to non-fisheaters for the variables sex, alcohol consumption (never or occasionally vs. regularly), age (+/-5y) and education (+/-2y). A total of 63 matched pairs were thus created. Paired analyses (t-test or Signed Rank) showed that fisheaters had higher levels of blood organic mercury and lead. Analysis of nervous system functions revealed that both groups performed similarly on tests of sensory function, visual memory and recognition, fine motor performance and some motor tests, but fisheaters performed significantly more poorly (p<0.05) on tests requiring cognitive flexibility, word naming, auditory recall, and more complex motor tasks. The profile of deficits is consistent with diminished capacity for information processing. These observations were made within a study that was not specifically designed to examine the effects of fish eating from these two lakes, and the characterization of fish dietary habits has many limitations. Nevertheless, the findings are sufficiently compelling to warrant further studies, since fish from the Upper St. Lawrence Lakes are known to contain multiple neurotoxic substances.
11-Hong Kong male subfertility links to mercury in human hair and fish.
Dickman MD, Leung CK, Leong MK.
Ecology and Biodiversity Department, University of Hong Kong, Hong Kong. firstname.lastname@example.org
The focus of the present study was on the relationship between Hong Kong male subfertility and fish consumption. Mercury concentrations found in the hair of 159 Hong Kong males aged 25-72 (mean age = 37 years) was positively correlated with age and was significantly higher in Hong Kong subjects than in European and Finnish subjects (1.2 and 2.1 ppm, respectively). Mercury in the hair of 117 subfertile Hong Kong males (4.5 ppm, P < 0.05) was significantly higher than mercury levels found in hair collected from 42 fertile Hong Kong males (3.9 ppm). Subfertile males had approx. 40% more mercury in their hair than fertile males of similar age. Although there were only 35 female subjects, they had significantly lower levels of hair mercury than males in similar age groups. Overall, males had mercury levels that were 60% higher than females. Hair samples collected from 16 vegetarians living in Hong Kong (vegans that had consumed no fish, shellfish or meat for at least the last 5 years) had very low levels of mercury. Their mean hair mercury concentration was only 0.38 ppm.
12-The toxicology of mercury.
Department of Environmental Medicine, University of Rochester School of Medicine, New York 14642, USA.
The major physical forms of mercury to which humans are exposed are mercury vapor, Hg0, and methylmercury compounds, Ch3HgX. Mercury vapor emitted from both natural and anthropogenic sources is globally distributed in the atmosphere. It is returned as a water-soluble form in precipitation and finds its way into bodies of fresh and ocean water. Land run-off also accounts for further input into lakes and oceans. Inorganic mercury, present in water sediments, is subject to bacterial conversion to methylmercury compounds that are bioaccumulated in the aquatic food chain to reach the highest concentration in predatory fish. Human exposure to mercury vapor is from dental amalgam and industries using mercury. Methylmercury compounds are found exclusively in seafood and freshwater fish. The health effects of mercury vapor have been known since ancient times. Severe exposure results in a triad of symptoms, erethism, tremor, and gingivitis. Today, we are concerned with more subtle effects such as preclinical changes in kidney function and behavioral and cognitive changes associated with effects on the central nervous system. Methylmercury is a neurological poison affecting primarily brain tissue. In adults, brain damage is focal affecting the function of such areas as the cerebellum (ataxia) and the visual cortex (constricted visual fields). Methylmercury also at high doses can cause severe damage to the developing brain. Today the chief concern is with the more subtle effects arising from prenatal exposure such as delayed development and cognitive changes in children.
13-Environmental epidemiology research leads to a decrease of the exposure limit for mercury]
[Article in Danish]
Weihe P, Debes F, White RF, Sorensen N, Budtz-Jorgensen E, Keiding N, Grandjean P.
Faeroernes Sygehusvaesen, afdeling for arbejdsmedicin og folkesundhed, Syddansk Universitet, Institut for sundhedstjenesteforskning, og Kobenhavns Universitet, Institut for Folkesundhedsvidenskab, Biostatistisk afdeling.
The central nervous system is particularly vulnerable to prenatal exposure to methylmercury. Due to the widespread exposure to methylmercury from fish, several prospective environmental epidemiology studies have been initiated, in which the maternal exposure during the pregnancy is related to the neurobehavioural development of the children. We have studied a Faroese birth cohort prenatally exposed to methylmercury from maternal intake of contaminated pilot whale meat. At seven years of age, clear dose-response relationships were observed for deficits in attention, language, and memory. An increase in blood pressure was also associated with the prenatal exposure level. The exposure limit for mercury has therefore been decreased.
14-[Immunologic effects of exposure to low levels of inorganic mercury]
[Article in Italian]
Soleo L, Colosio C, Alinovi R, Guarneri D, Russo A, Lovreglio P, Vimercati L, Birindelli S, Cortesi I, Flore C, Carta P, Colombi A, Parrinello G, Ambrosi L.
Dipartimento di Medicina Interna e Medicina Pubblica, Servizio di Medicina del Lavoro, Policlinico, P.zza G. Cesare 11, 70124 Bari.
OBJECTIVE: The immune system is a target for the toxic effects of inorganic mercury, both in humans and animals. In humans it has been observed that occupational and environmental exposure to inorganic mercury may cause both clinical (autoimmunity, hypersensitivity) and subclinical effects (cellular and humoral immunologic variable modifications). To obtain a better definition of these effects with respect to the exposure levels, a multicentre study was performed on 117 workers exposed to very low doses of inorganic mercury and 172 subjects from the general population of the same geographical area with environmental exposure to mercury from dental amalgams and dietary fish intake. RESULTS: The white blood cell count was included in the normality range for all subjects and there was no difference between exposed and non exposed subjects. The immunologic variables studied showed an increase of the CD4+ and CD8+ number in exposed workers compared to non-exposed subjects, with a statistically significance only for CD4+, while no difference was observed regarding CD4+, CD8+, NK+ percentage and CD4+/CD8+ ratio. A significative decrease of serum IL-8 and an inverse correlation between serum levels of this cytokine and HgU were observed in exposed workers compared to non exposed subjects. No association between immunologic variables and both dental amalgams and dietary fish intake was found in subjects not occupationally exposed to inorganic mercury. DISCUSSION: The decrease in IL-8 serum levels observed in exposed workers might suggest an immunosuppressive effect of occupational exposure to very low doses of inorganic mercury. This result suggests the need to revise of current HgU BEI after further definition of its prognostic significance.
15-Neuroendocrine and neurobehavioral effects associated with exposure to low doses of mercury from habitual consumption of marine fish]
[Article in Italian]
Carta P, Flore C, Alinovi R, Ibba A, Tocco M, Aru G, Carta R, Girei M, Mutti A, Sanna FR.
Universita degli Studi di Cagliari, Dipartimento di Sanita Pubblica-Sezione di Medicina del Lavoro, Via S. Giorgio 12, 09124 Cagliari. email@example.com
OBJECTIVES: To evaluate neuroendocrine and neurobehavioral effects possibly associated with increased dietary intake of organic mercury (Hg), a group of 22 subjects living on the island of Carloforte (south-west Sardinia) was examined, who were regular consumers of tuna fish with relatively high Hg content. This group, never exposed occupationally to either Hg or to other neurotoxic substances, was compared with 22 age-matched controls employed at a chemical plant in Portotorres (northern Sardinia). METHODS: Hg in urine (HgU) and serum prolactin (PRL) were measured in all cases, whereas measurements of total (HgB) and organic blood mercury were available only for 10 subjects from Carloforte and 6 controls. Data about working history and lifestyle (education, smoking habit, alcohol and sea fish consumption) were collected by an interviewer using a standardised questionnaire. Neurotoxic symptoms were evaluated by a self-administered questionnaire, whereas a test battery, including some computerised tests of the Swedish Performance Evaluation System (SPES) to assess vigilance and psychomotor performance, some tests on motor coordination (Luria-Nebraska and Branches Alternate Movement Task) and one memory test for numbers (Digit Span) was administered to assess neurobehavioral changes associated with exposure to dietary intake of organic mercury. In all cases, characteristics of hand tremor were evaluated by the CATSYS System 7.0. RESULTS: HgU values were significantly higher in the Carloforte group (median 6.5, range 1.8-21.5 micrograms/g creatinine) compared with controls (median 1.5, range 0.5-5.3 micrograms/g creatinine). Serum PRL was significantly higher among subjects from Carloforte and correlated with both urine and blood Hg levels. The scores of each item of the questionnaire investigating neurological symptoms were not statistically different in the two groups. In some tests of the SPES battery (Color Word Vigilance, Digit Symbol and Finger Tapping) the performance of the Carloforte group was significantly worse than that of controls, whereas in the other neurobehavioral tests poorer performances by the Carloforte group were not statistically significant. None of the tremor parameters was significantly different comparing the two groups. Multivariate analysis--controlling for education level and other covariates--carried out for the Symbol-Digit Reaction Time and for the Branches Alternate Movement Task (BAMT) showed that organic Hg concentration in blood was the most significant factor negatively affecting individual performance in these tests. Serum PRL was correlated with some neurobehavioral tests (Digit Symbol, Finger Tapping and BAMT). CONCLUSIONS: Some of the neurobehavioral tests were sensitive enough to discriminate groups with different Hg body burden, even in the low-dose range. However, the pattern of results suggests adverse neurobehavioral effects, especially on psycho-motor coordination, with a significant dose-effect relationship, mostly associated with long-term exposure to low levels of organic mercury due to the usual consumption of large fish with relatively high levels of Hg in the flash.
16-[Neurotoxic effect of exposure to low doses of mercury]
[Article in Italian]
Lucchini R, Cortesi I, Facco P, Benedetti L, Camerino D, Carta P, Urbano ML, Zaccheo A, Alessio L.
Cattedra di Medicina del Lavoro, Universita di Brescia, P.le Spedali Civili 1, 25125 Brescia.
OBJECTIVES: To assess early effects on the Central Nervous System due to occupational exposure to low levels of inorganic mercury (Hg) in a multicenter nationwide cross-sectional study, including workers from chloro-alkali plants, chemical industry, thermometer and fluorescent lamp manufacturing. The contribution of non-occupational exposure to inorganic Hg from dental amalgams and to organic Hg from fish consumption was also considered. METHODS: Neuropsychological and neuroendocrine functions were examined in a population of 122 workers occupationally exposed to Hg, and 196 control subjects, not occupationally exposed to Hg. Neuropsychological functions were assessed with neurobehavioral testing including vigilance, motor and cognitive function, tremor measurements, and with symptoms concerning neuropsychological and mood assessment. Neuroendocrine functions were examined with the measurement of prolactin secretion. The target population was also characterized by the surface of dental amalgams and sea fish consumption. RESULTS: In the exposed workers the mean urinary Hg (HgU) was 10.4 +/- 6.9 (median 8.3, geometric mean 8.3, range 0.2-35.2) micrograms/g creatinine, whereas in the control group the mean HgU was 1.9 +/- 2.8 (median 1.2, geometric mean 1.2, range 0.1-33.2) micrograms/g creatinine. The results indicated homogeneous distribution of most neurobehavioral parameters among exposed and controls. On the contrary, finger tapping (p < 0.01) and the BAMT (Branches Alternate Movement Task) coordination test (p = 0.05) were associated with occupational exposure, indicating an impairment in the exposed subjects. Prolactin levels resulted significantly decreased among the exposed workers, and inversely related to HgU on an individual basis (p < 0.05). An inverse association was also observed between most neuropsychological symptoms and sea fish consumption, indicating a "beneficial effect" from eating sea fish. On the contrary, no effects were observed as a function of dental amalgams. CONCLUSIONS: In conclusion, this study supports the finding of early alterations of motor function and neuroendocrine secretion at very low exposure levels of inorganic Hg, below the current ACGIH BEI and below the most recent exposure levels reported in the literature.
17-Mercury exposure and early effects: an overview.
Environmental Geochemistry Research Group, Department of Environmental Science and Technology, Imperial College of Science, Technology & Medicine, Prince Consort Road, London SW7 2BP, UK.
OBJECTIVES: This paper was given as a keynote address at the conference on The Assessment of the Effects Due to Low Doses of Inorganic Mercury following Environmental and Occupational Exposures: Human and in vitro Studies on the Specific Mechanisms of Toxicity in Gargnano, Italy, in September 2001. METHODS: The most relevant literature over the past 40 years has been reviewed, and in particular, the proceedings of the World Health Organisation conferences on the health effects of inorganic and organic mercury exposure have been considered. RESULTS: In an uncontaminated environment the general population is exposed to mercury vapour from the atmosphere and from dental amalgam, while the diet, mainly from fish, is the principal source for methyl mercury absorption. Mercury vapour release from amalgam fillings increases with chewing, with absorption and uptake by the brain and kidneys. Infants exposed to phenyl mercury from treated diapers and young children ingesting mercurous chloride in teething powders have developed acrodynia (pink disease), and Kawasaki disease and the use of mercurial skin lightening creams has been followed by the development of the nephrotic syndrome. Both mercury compounds and mercury vapour have given rise to contact dermatitis in the general population. Epidemics of mercury poisoning have followed release of mercury into the environment from industrial activity, with uptake of methyl mercury from fish eating in Minamata Bay and uptake of both inorganic and methyl mercury following release of mercury vapour and deposition into waterways from gold recovery procedures in the Amazon basin. The ingestion of wheat and barley seed treated with an alkyl mercury fungicide for sowing, by a largely illiterate population in Iraq, led to a major outbreak of poisoning with a high fatality rate. Following exposure to mercury vapour, the earliest clinically observed adverse effects at urine mercury levels of the order of 30-100 mg/g creatinine, are objectively detectable tremor, psychological disorder and impaired nerve conduction velocity in sensitive subjects, with subjective symptoms of irritability, fatigue and anorexia. At these and at lower levels, proteinuria has also been observed. Both glomerular and tubular damage may occur at exposure levels lower than those giving rise to central nervous system effects. An immunological effect has also been observed in studies on clinically asymptomatic workers with low level exposure. CONCLUSIONS: As mercury can give rise to allergic and immunotoxic reactions which may be genetically regulated, in the absence of adequate dose-response studies for immunologically sensitive individuals, it has not been possible to set a level for mercury in blood or urine below which mercury related symptoms will not occur.
18-Mercury exposure: current concepts, controversies, and a clinic's experience.
Kales SN, Goldman RH.
Cambridge Health Alliance, Harvard Medical School, Harvard School of Public Health, Department of Environmental Health (Occupational Health Program), Cambridge, MA, USA. firstname.lastname@example.org
In the context of controversies surrounding fish consumption, amalgams, and commercial hair testing, we reviewed all cases from an occupational and environmental medicine clinic that had undergone mercury testing. Sixty-nine of 71 (97%) patients had no known mercury exposures other than diet or amalgams. Of these 69, 48 had blood mercury tested and 58 had urine testing. Regular-to-heavy fish consumption explained 10 of 11 cases with blood mercury concentrations > 15 micrograms/L (19 to 53 micrograms/L). Six of these 10 individuals reported regular swordfish consumption. For the 31 patients with adequate dietary history, there was a significant relationship between fish consumption and blood mercury concentration (P < 0.001). Higher blood mercury concentrations were, however, not associated with specific patterns of health complaints. Ninety-eight percent (57 of 58) of urine values were < 10 micrograms/L. Fourteen patients were evaluated because they were labeled as mercury toxic by other practitioners after unconventional commercial testing. Using standard tests of blood and urine, we could not document evidence of mercury toxicity in any of these 14 cases. We conclude that consumption of commercially available fish can lead to elevated blood mercury concentrations. A recognized exposure source is a better predictor of significant mercury concentrations in biologic media than any particular symptom constellation. Unconventional commercial panels that test hair or urine for multiple metals have questionable validity. Clinicians should use standard blood and urine tests to evaluate mercury exposure.
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