By JOAN LOWY
Scripps Howard News Service
February 04, 2004

- About 630,000 children are born each year at risk for lowered intelligence and learning problems due to exposure to high levels of mercury in the womb, according to a new analysis by the Environmental Protection Agency.

That's nearly double the previous EPA estimate of 320,000 babies a year.

The new estimate is based on data collected by the Centers for Diseases Control and Prevention and recent studies that show the level of mercury in the umbilical cord blood of newborns is 1.7 times higher than the mercury level in their mother's blood. According to the new estimate, one in every six women of childbearing age has enough mercury in her blood to pose a risk to her child, compared to previous estimates of one in every 12 women.

Blood samples taken by the CDC from 1,709 women found that 8 percent of the women of childbearing age had mercury levels at or above 5.8 parts per billion, the EPA's safety limit. However, recent studies indicate that the developing fetus may have more difficulty excreting mercury than pregnant women, which would account for the higher mercury levels in cord blood versus maternal blood.

That means a mercury level of only 3.5 ppb in a mother's blood would be enough for her fetus' blood to cross the 5.8 ppb safety threshold, according to an analysis by Kathryn Mahaffey, a scientist with EPA's Office of Prevention, Pesticides and Toxic Substances. Nearly 16 percent of women have mercury blood levels of 3.5 ppb or higher, Mahaffey calculated.

Blood mercury levels were also seven times higher in women who told the CDC they had eaten fish two or more times a week over the previous month compared to women who said they had not eaten fish in the previous month, Mahaffey reported.

While adults can be harmed by long-term exposure to small amounts of mercury, a powerful neurotoxin, the risk is much greater for fetuses and young children because their nervous systems are still developing. The main source of human exposure to mercury is through eating fish, particularly larger species of fish at the top of the food chain like shark, swordfish, and some species of tuna.

The new estimate is likely to add more fuel to the already heated debate over whether the government should be doing more to warn consumers of the health risks of eating fish with high levels of mercury, including such frequently consumed fish as canned albacore tuna.

"Over 600,000 children are born each year overexposed to mercury in seafood," said Jane Houlihan, a scientist with the Environmental Working Group, an advocacy group. "This increases the urgency for the Food and Drug Administration to correct the misinformation it is giving the public and for the Bush administration to crack down on mercury pollution from coal-fired power plants."

However, Linda Candler, a spokeswoman for the National Fisheries Institute, a trade association for the commercial seafood industry, said that the consumption of seafood in the United States is generally so low that children are not at risk. "It's long been known that if you eat a lot of high level mercury species your mercury levels go up," Candler said. "However, fish is so important to the diet and the developing fetus that mothers should not let these things scare them away from eating fish during pregnancy. They should of course follow the FDA's advice to avoid those high mercury species."

Cognitive deficit in 7-year-old children with prenatal exposure to methylmercury.

Grandjean P, Weihe P, White RF, Debes F, Araki S, Yokoyama K, Murata K, Sorensen N, Dahl R, Jorgensen PJ.

Institute of Community Health, Odense University, Denmark. p.grandjean@winsloew.ou.dk

A cohort of 1022 consecutive singleton births was generated during 1986-1987 in the Faroe Islands. Increased methylmercury exposure from maternal consumption of pilot whale meat was indicated by mercury concentrations in cord blood and maternal hair. At approximately 7 years of age, 917 of the children underwent detailed neurobehavioral examination. Neuropsychological tests included Finger Tapping; Hand-Eye Coordination; reaction time on a Continuous Performance Test; Wechsler Intelligence Scale for Children-Revised Digit Spans, Similarities, and Block Designs; Bender Visual Motor Gestalt Test; Boston Naming Test; and California Verbal Learning Test (Children). Clinical examination and neurophysiological testing did not reveal any clear-cut mercury-related abnormalities. However, mercury-related neuropsychological dysfunctions were most pronounced in the domains of language, attention, and memory, and to a lesser extent in visuospatial and motor functions. These associations remained after adjustment for covariates and after exclusion of children with maternal hair mercury concentrations above 10 microgram(s) (50 nmol/g). The effects on brain function associated with prenatal methylmercury exposure therefore appear widespread, and early dysfunction is detectable at exposure levels currently considered safe.
 

Concentrations of heavy metals in maternal and umbilical cord blood. Ong CN, Chia SE, Foo SC, Ong HY, Tsakok M, Liouw P. Biometals. 1993 Spring; 6(1):61-6. 8471826 PubMed. These results suggest that, like essential metals, most heavy metals can move rather freely across the human placenta. The potential health effects of heavy metal transfer from mothers to young infants cannot be discounted.

Disposition of inhaled mercury vapor in pregnant rats: maternal toxicity and effects on developmental outcome. Morgan DL, Chanda SM, Price HC, Fernando R, Liu J, Brambila E, O'Connor RW, Beliles RP, Barone S Jr. Toxicol Sci. 2002 Apr;66(2):261-73. 11896293 PubMed. Total Hg concentrations in maternal tissues increased with increasing number of exposure days and concentration. In general, approximately 70% of Hg was eliminated from maternal tissues during the week following the last exposure (GD 15 to PND 1). Elimination of Hg from maternal brain and kidney was slower than in other tissues, possibly due to higher levels of metallothionein. Total Hg concentrations in fetal tissues increased with increasing number of exposure days and concentration, demonstrating that a significant amount of Hg crossed the placenta. One week after the last exposure, significant amounts of Hg were still present in brain, liver, and kidney of PND 1 neonates. The total amount of Hg in neonatal brain (ng/brain) continued to increase after termination of inhalation exposure, suggesting a redistribution of Hg from the dam to neonatal brain. These data demonstrate that inhaled Hg0 vapor is distributed to all maternal and fetal tissues in a dose-dependent manner. Adverse effects of Hg on developmental outcome occurred only at a concentration that caused maternal toxicity.


Distribution and transfer pathways of antioxidant molecules inside the first trimester human gestational sac. Jauniaux E, Cindrova-Davies T, Johns J, Dunster C, Hempstock J, Kelly FJ, Burton GJ. J Clin Endocrinol Metab. 2004 Mar;89(3):1452-8. 15001647 PubMed. The first-trimester human placenta has limited antioxidant enzyme capacity. We investigated the distribution and transfer pathways of antioxidant molecules inside the first trimester gestational sac. The coelomic fluid of the exocoelomic cavity, which borders the inside of the first-trimester placenta, contained a very low level of reduced glutathione. Glutathione disulfide was undetectable in most coelomic samples, suggesting that the role of glutathione-related detoxification system is limited in fetal fluid compartments. The coelomic fluid contained similar concentrations of ascorbic and uric acid to maternal plasma. The levels of alpha- and gamma-tocopherol were lower in coelomic fluid, compared with maternal plasma. The presence of these molecules inside the early gestational sac suggests that they may play an essential role in the fetal tissues' antioxidant capacity at a time when the fetus is most vulnerable to oxidative stress. We also demonstrated by immunostaining the presence of alpha-tocopherol transfer protein in the cytoplasm of trophoblastic cells, glandular epithelium of the decidua, and mesothelial layer of the secondary yolk sac. This finding indicates that the uterine glands and the secondary yolk sac play key roles in supplying this essential vitamin to the developing fetus before the placental circulations are established.

Effect of inorganic mercury on in vitro placental nutrient transfer and oxygen consumption. Urbach J, Boadi W, Brandes JM, Kerner H, Yannai S. Reprod Toxicol. 1992; 6(1):69-75. 1562801 PubMed. The effect of mercury (HgCl2) on placental amino acid and glucose transfer as determined by the use of their nonmetabolizable radioactive analogues, aminoisobutyric acid (AIB) and 3-o-methyl glucose (3MG), respectively, was studied in an in vitro perfusion model of a term human placenta. Hg2+ was found to decrease the transfer and accumulation of AIB without affecting 3MG transfer. It was also found to decrease the placental oxygen consumption rate. Placental circulation and tissue morphology remained intact, as demonstrated by the antipyrine transfer rate, and by electron microscopy, respectively. The mechanism by which Hg2+ may interfere with placental amino acid transfer and accumulation is discussed. Although much higher concentrations than those found in the ordinary polluted environment were used, this is the first report showing that Hg2+ interferes with an essential human placental function in a system employing a whole human placental cotyledon. This finding may indicate the possible involvement of Hg2+ in impaired organogenesis in early pregnancy or deranged fetal growth during the last trimester.

Environmental factors associated with a spectrum of neurodevelopmental deficits. Mendola P, Selevan SG, Gutter S, Rice D. Ment Retard Dev Disabil Res Rev. 2002; 8(3):188-97. 12216063 PubMed. At high levels of prenatal exposure, methylmercury produces mental retardation, cerebral palsy and visual and auditory deficits in children of exposed mothers. Exposure to environmental agents with neurotoxic effects can result in a spectrum of adverse outcomes from severe mental retardation and disability to more subtle changes in function depending on the timing and dose of the chemical agent.

Evolution of our understanding of methylmercury as a health threat. Watanabe C, Satoh H. Environ Health Perspect. 1996 Apr; 104 Suppl 2:367-79. 9182044 PubMed. After repeated occurrences of MeHg poisoning, it gradually became clear that the fetus is much more susceptible to the toxicity of this compound than the adult. The results of these studies revealed that the effects encompass a wide range of behavioral categories without clear identification of the functional categories distinctively susceptible to MeHg.

Influence of prenatal mercury exposure upon scholastic and psychological test performance: benchmark analysis of a New Zealand cohort. Crump KS, Kjellstrom T, Shipp AM, Silvers A, Stewart A. Risk Anal. 1998 Dec; 18(6):701-13. 9972579 PubMed. The original analyses of five test scores found an association between high prenatal mercury exposure and decreased test performance, using category variables for mercury exposure. Our regression analyses, which utilized the actual hair mercury level, did not find significant associations between mercury and children's test scores. However, this finding was highly influenced by a single child whose mother's mercury hair level (86 mg/kg) was more than four times that of any other mother. When that child was omitted, results were more indicative of a mercury effect and scores on six tests were significantly associated with the mothers' hair mercury level. BMDs calculated from five tests ranged from 32 to 73 mg/kg hair mercury, and corresponding BMDLs (95% lower limits on BMDs) ranged from 17 to 24 mg/kg.


Intrauterine methylmercury intoxication. Consequence of the inherent brain lesions and cognitive dysfunction in maturity. Kakita A, Wakabayashi K, Su M, Yoneoka Y, Sakamoto M, Ikuta F, Takahashi H. Brain Res. 2000 Sep 22; 877(2):322-30. 10986347 PubMed. Morphometric analysis of the amygdala and hippocampus revealed significantly fewer neurons in both areas in the MeHg-exposed rats. Thus, chronic intrauterine exposure to low-dose MeHg induces a decrease in neuron population in the limbic system, and the offspring have impaired higher brain function.

Longitudinal study of methylmercury and inorganic mercury in blood and urine of pregnant and lactating women, as well as in umbilical cord blood.
Vahter M, Akesson A, Lind B, Bjors U, Schutz A, Berglund M. Environ Res. 2000 Oct ;84(2):186-94. 11068932 PubMed. We have investigated exposure to methylmercury (MeHg) and mercury vapor (Hg0) in pregnant women and their newborns in Stockholm. The women were followed for 15 months post delivery. MeHg, inorganic Hg (I-Hg), and total Hg (T-Hg) in maternal and cord blood were determined by automated alkaline solubilization/reduction and cold vapor atomic fluorescence spectrometry. T-Hg in urine was determined by inductively coupled plasma mass spectrometry. About 72% of the Hg in blood (n = 148) in early pregnancy was MeHg (median 0.94 microg/L, maximum 6.8 microg/L). Blood MeHg decreased during pregnancy, partly due to decreased intake of fish in accordance with recommendations to not eat certain predatory fish during pregnancy. Cord blood MeHg (median 1.4 microg/L, maximum 4.8 microg/L) was almost twice that in maternal blood in late pregnancy and was probably influenced by maternal MeHg exposure earlier and before pregnancy. Blood I-Hg (median 0.37 microg/L, maximum 4.2 microg/L) and urine T-Hg (median 1.6 microg/L, maximum 12 microg/L) in early pregnancy were highly correlated, and both were associated with the number of amalgam fillings. The concentrations decreased during lactation, probably due to excretion in milk. Cord blood I-Hg was correlated with that in maternal blood. The results show the importance of speciation of Hg in blood for evaluation of exposure and health risks.


Maternal-fetal transfer of metallic mercury via the placenta and milk. Yang J, Jiang Z, Wang Y, Qureshi IA, Wu XD. Ann Clin Lab Sci. 1997 Mar-Apr; 27(2):135-41. 9098513 PubMed. Therefore, this study concluded that the metallic mercury can be transferred to the fetus via the placenta and secreted to a newborn via milk.


Placental to fetal transfer of mercury and fetotoxicity. Yoshida M. Tohoku J Exp Med. 2002 Feb; 196(2):79-88. 12498319 PubMed. Mercury vapor is known penetrate the placental barrier more easily than inorganic mercury. A relative amount of mercury accumulates in the fetus after exposure of pregnant animals to mercury vapor. Mercury concentration in fetal organs is much lower than that in maternal organs except the liver, and fetal liver shows significantly higher mercury concentrations than maternal liver. In fetal liver, a substantial portion of mercury is bound to metallothionein (MT), which plays an important role as a reservoir of mercury during the prenatal period. The mercury retained in fetal liver is redistributed to other organs, such as the brain and kidney, with diminishing MT levels during postnatal development. Consequently, an increase in mercury concentration in the brain and kidney of the neonate is observed. In studies on animal offspring in utero exposed to mercury vapor, behavioral changes, such as radial arm maze, morris maze and lever-press durations, are observed when the levels of mercury vapor exceed the threshold limit value (TLV).


Technical report: mercury in the environment: implications for pediatricians. Goldman LR, Shannon MW. American Academy of Pediatrics: Committee on Environmental Health. Pediatrics. 2001 Jul; 108(1):197-205. 11433078 PubMed. Mercury is a ubiquitous environmental toxin that causes a wide range of adverse health effects in humans. Three forms of mercury (elemental, inorganic, and organic) exist, and each has its own profile of toxicity. Exposure to mercury typically occurs by inhalation or ingestion. Readily absorbed after its inhalation, mercury can be an indoor air pollutant, for example, after spills of elemental mercury in the home; however, industry emissions with resulting ambient air pollution remain the most important source of inhaled mercury. Because fresh-water and ocean fish may contain large amounts of mercury, children and pregnant women can have significant exposure if they consume excessive amounts of fish. The developing fetus and young children are thought to be disproportionately affected by mercury exposure, because many aspects of development, particularly brain maturation, can be disturbed by the presence of mercury. Minimizing mercury exposure is, therefore, essential to optimal child health. This review provides pediatricians with current information on mercury, including environmental sources, toxicity, and treatment and prevention of mercury exposure.

The effect of mercury vapour on cholinergic neurons in the fetal brain: studies on the expression of nerve growth factor and its low- and high-affinity receptors. Soderstrom S, Fredriksson A, Dencker L, Ebendal T. Brain Res Dev Brain Res. 1995 Mar 16;85(1):96-108. 7781173 PubMed. These findings suggest that low levels of prenatal mercury vapour exposure can alter the levels of the NGF and its receptors, indicating neuronal damage and disturbed trophic regulations during development.


Total and inorganic mercury in breast milk in relation to fish consumption and amalgam in lactating women. Oskarsson A, Schultz A, Skerfving S, Hallen IP, Ohlin B, Lagerkvist BJ. Arch Environ Health. 1996 May-Jun;51(3):234-41. 8687245 PubMed. The concentrations of total mercury and organic mercury (calculated by subtraction of inorganic mercury from total mercury) in blood (r = .59, p = .0006, and r = .56, p = .001; respectively) and total mercury in hair (r = .52, p = .006) were correlated with the estimated recent exposure to methylmercury via intake of fish. A significant correlation was found between levels of total mercury in blood and in milk (r = .66, p = .0001), with milk levels being an average of 27% of the blood levels. There was an association between inorganic mercury in blood and milk (r = .96, p < .0001); the average level of inorganic mercury in milk was 55% of the level of inorganic mercury in blood. The results indicated that there was an efficient transfer of inorganic mercury from blood to milk and that, in this population, mercury from amalgam fillings was the main source of mercury in milk. Exposure of the infant to mercury from breast milk was calculated to range up to 0.3 microg/kg x d, of which approximately one-half was inorganic mercury. This exposure, however, corresponds to approximately one-half the tolerable daily intake for adults recommended by the World Health Organization. We concluded that efforts should be made to decrease mercury burden in fertile women.

For more info see this excellent website.
http://www.dentalwellness4u.com/products/refdoc.html
 

Toxicol Pathol. 2004 Sep-Oct;32(5):519-26

Ultrastructural demonstration of mercury granules in the placenta of metallothionein-null pregnant mice after exposure to mercury vapor.

* Shimada A. et al Department of Veterinary Pathology, Tottori University, Minami 4-101, Koyama, Tottori-shi, Tottori 680-0945, Japan. aki@muses.tottori-u.ac.jp

The placenta plays an important role in the regulation of maternal to fetal transfer of toxic substances, including nonessential metals. Metallothioneins (MTs), which are known to have protective effects against
heavy metal toxicity, exist in the placenta, but the exact localization of placental MTs (both MT-I and MT-III) and their physiological role in the placenta exposed to mercury are unclear. The present study was performed to examine the localization of MTs and mercury granules in the placenta of mice exposed to mercury vapor. On gestational day 16, MT-I & II-null and wild-type mice were exposed to mercury vapor at 4.9 to 5.9 mg/m3 for 2 hours. At 24 and 48 hours after exposure, the placentas were examined for mercury distribution (autometallography), MT immunoreactivity, and MT mRNA expression (in situ hybridization). No histological changes were observed in the placentas of either MT-null or wild-type mice. Mercury deposition was demonstrated along the boundary between the junctional zone and the labyrinth zone, as well as in the yolk sac, maternal decidual cells, and labyrinth trophoblasts of both MT-null and wild-type mice. MT-I & -II immunoreactivity, which was confined to wild-type mice, was demonstrated in the yolk sac and decidual cells; mercury was also shown in both structures, suggesting that mercury granules were bound to MTs. MT-III mRNA expression was observed in the yolk sac, decidual cells, and spongiotrophoblasts in both MT-null and wild-type mice. There was, however, no evidence of MT at the boundary between the junctional and labyrinth zones, where substantial mercury deposits were demonstrated. These results suggest that placental MTs and the other unknown molecules may be related to the barrier to the placental transfer of mercury.

PMID: 15603537 [PubMed - indexed for MEDLINE]

Brain Pathol. 2006 Jan;16(1):1-14.

 

Mercury Triggers Premature Birth

By Kim Rahn
Staff Reporter
The more mercury pregnant women are exposed to, the greater chance they have of giving premature birth to babies, according to a study.

Research on 85 pregnant women conducted by Ha Eun-hee, a professor of Ewha Womans University's preventive medicine department, showed that women with high levels of mercury in cord blood are three to five times more likely to give premature birth, which is  to deliver a child in less than 37 weeks of pregnancy.

Ha announced the study results on Friday during a meeting of the Korean Society for Preventive Medicine.

According to the study, the 50 percent of the 85 people with the highest levels of mercury had a 3.1 times greater chance of having a premature delivery than the lower 50 percent. The upper 25 percent had a 5.3 times more of a chance than the lower 75 percent. ``Mercury in cord blood, which connects the mother and the fetus, is critical to the child, as it directly flows to the fetus,'' Ha said. The study disclosed two main reasons for the mercury concentration _ dental treatment with amalgam and fish consumption.

Pregnant women who had treatments with amalgam during the pregnancy had an average of 5.15 micrograms of mercury per 1 liter of blood, 1.3 times more than the 3.98 micrograms in women who hadn't had the treatment. The mercury level increased in proportion to the frequency of treatment. Women undergoing the amalgam treatment fewer than three times had an average 4.8 micrograms  of mercury in their blood, while those having undergone the treatment three to six times  had 5.04 micrograms, and seven times or more 5.2 micrograms.

Also, a woman who never had fish during pregnancy had 4.6 micrograms of mercury per 1  liter of blood, while the mercury level of women who consumed fish more than four times  per week had an average mercury level of 8.3 micrograms.

``The nation should prepare education programs for pregnant women, advising them not  to undergo dental treatments with amalgam,'' Ha said. Professor Yi Seung-muk at Seoul National University's graduate school of public health  said a great deal of mercury in the air above the Korean Peninsula is from China's  industrial areas.

Yi's team measured mercury levels in the air and followed the path of wind to China. ``We obtained Chinese institutes' data about the industrial locations emitting mercury and compared them with our data, which correlated with the Chinese data,'' Yi said. It was the first South Korean research about mercury pollution from China, although international academic circles have presented studies about the issue. It is said that half of the world's mercury pollutants in the air come from the country with the largest populace.

``Mercury is contained not only in the air, but also in fish. Korea and Japan, which are near China and consume large amounts of fish, have a greater chance of being exposed to mercury than other countries,'' Yi said. The research was announced at a meeting of the Korean Society for Atmospheric
Environment on Friday. Yi will soon present the amount and ratio of pollutants carried to Korea.

rahnita@koreatimes. <mailto:rahnita%40koreatimes.co.kr> co.kr
 

Thought this might interest some of you.

Hair mercury in breast-fed infants exposed to thimerosal-preserved
vaccines.

Marques RC, Dorea JG, Fonseca MF, Bastos WR, Malm O.
Fundacao Universidade Federal de Rondonia, Porto Velho, RO, Brazil.

Because of uncertainties associated with a possible rise in neuro-developmental deficits among vaccinated children, thimerosal-preserved vaccines have not been used since 2004 in the USA (with the
exception of thimerosal-containing influenza vaccines which are routinely recommended for administration to pregnant women and children), and the EU but are widely produced and used in other countries. We investigated the impact of thimerosal on the total Hg in hair of 82 breast-fed infants during the first 6 months of life. The infants received three doses of the hepatitis-B vaccine (at birth, 1 and 6 months) and three DTP (diphtheria, tetanus, and pertussis) doses at 2, 4 and 6 months, according to the immunization schedule recommended by the Ministry of Health of Brazil. The thimerosal in vaccines provided an ethylmercury (EtHg) exposure of 25 mugHg at birth, 30, 60 and 120 days, and 50 mugHg at 180 days. The exposure to vaccine-EtHg represents 80% of that expected from total breast milk-Hg in the first month but only 40% of the expected exposure integrated in the 6 months of breastfeeding. However, the Hg exposure corrected for body weight at the day of immunization was much higher from thimerosal- EtHg (5.7 to 11.3 mugHg/kg b.w.) than from breastfeeding (0.266 mugHg/kg b.w.). While mothers showed a relative decrease (-57%) in total hair-Hg during the 6 months lactation there was substantial increase in the infant's hair-Hg (446%). We speculate that dose and parenteral mode of thimerosal-EtHg exposure modulated the relative increase in hair-Hg of breast-fed infants at 6 months of age.

PMID: 17237965 [PubMed - as supplied by publisher]

 

http://www.indystar.com/apps/pbcs.dll/article?AID=/20070211/LOCAL17/702110366/1012

 5 to 6 parts per billion shuts down the brain cells. A flu shot is 50,000 ppb!

February 11, 2007

Study: Low toxicant levels can damage brain
Researchers find that cells will shut down when exposed to small
amounts of mercury, lead
By Jamie Talan
Newsday
February 11, 2007

Low levels of mercury and lead exposure can damage developing brain cells, a finding that might help explain how these toxicants can lead to a host of mental and medical problems, a new study said. "There are 80,000 to 150,000 environmental toxicants about which we know nothing," said Mark Noble, a professor of biomedical genetics and neurobiology at the University of Rochester in New York and senior author of the study in the journal PLoS Biology. "Nobody knows
how to screen for them or even where to start." His study could be a major step in identifying methods of prevention and treatment. Noble and his colleagues conducted their work in the laboratory, where they subjected so-called glial progenitor stem cells in the brain to low levels of lead and mercury. They found that these brain cells simply shut down. The mercury levels previously were thought to be safe in humans, Noble said."These levels -- 5 to 6 parts per billion -- have adverse effects on these progenitor stem cells," he said. Noble said studies have shown that between 300,000 and 600,000 babies are born each year with fetal mercury levels in cord blood that are 5 to 6 parts per billion. The researchers found that progenitor stem cells, the brain's support cells that carry out a number of key housekeeping functions, are extraordinarily vulnerable to low levels of toxicants. In the test tube, as many as 25 percent of the progenitor cells obtained from rats shut down when exposed to the low levels of lead or mercury. Glial progenitor cells also are present in adult brains. Noble said they have no idea what effects low level environmental toxicants are having, but he suspects they might be making these brain cells more  vulnerable to damage and disease.
 

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