Maternal Blood Mercury Levels Research Articles

Assessment of lead and mercury levels in maternal blood, fetal cord blood and placenta in pregnancy with intrauterine growth restriction

Introduction: Many studies reported that prenatal exposure to lead and mercury are correlated with reduced birth weight and size, and these metals can cause adverse effects on neurodevelopment. In this study, it was aimed to investigate and compare the lead and mercury levels in maternal blood, cord blood, and placenta in pregnant women with IUGR fetuses diagnosed using abnormal Doppler findings and pregnant women with healthy fetuses.
 Material: This study included 75 patients, comprising 41 in IUGR group and 34 in control group. Maternal venous blood, fetal cord blood and placental samples were taken during delivery period.
 Results: Mercury levels in maternal blood and fetal cord blood, and lead levels in the placenta were found to be significantly higher in the IUGR group than in healthy subjects. Correlation analysis revealed that measurement values of body weight, body height, and head circumference of fetus might be lower when mercury level was measured higher in maternal blood and fetal cord blood. Furthermore, fetal body weight and fetal body height also would be lower when lead level measured in placenta was higher. Logistic Regression analysis results revealed that mercury levels measured in fetal cord blood could be used as the best marker in predicting low fetal weight, low fetal body height, and low fetal head circumference.
 Conclusion: In conclusion, it was thought with this study results that in order to identify the etiology and to give therapeutic prenatal care of the IUGR in a fetus diagnosed as idiopathic IUGR it would be appropriate to measure the level of lead and especially mercury in the fetal cord blood during the prenatal follow-up period.

Association of blood mercury levels during pregnancy with infant birth size by blood selenium levels in the Japan Environment and Children's Study: A prospective birth cohort

BackgroundIt is necessary to determine whether there are adverse health effects of prenatal exposure to long-term, low levels of mercury and selenium. However, there are limited that reports on the association between mercury levels by selenium levels and birth size. Therefore, we examined whether maternal mercury levels during pregnancy had any effect on infant birth size, and size, and whether selenium levels influenced this relationship. ObjectivesTo examine the association between mercury and selenium levels during pregnancy with infant birth size. MethodsThe Japan Environment and Children's Study is a prospective birth cohort conducted between 2011 and 2014. Total mercury levels and total selenium levels in maternal blood during the second and third trimesters were measured using Inductively Coupled Plasma-Mass Spectrometry. Birth weight and small-for-gestational-age were confirmed by medical records. Small-for-gestational-age was defined as birth weight below the 10th percentile according to standard percentile for gender, parity, and gestational age. Multiple linear and logistic regression analyses were used to examine the association between maternal mercury exposure and birth weight or small-for-gestational-age adjusted for confounders (including maternal age and body mass index pregnancy). ResultsOverall, 15,444 pregnant women were included in this study. Median (inter-quartile range) of blood mercury and selenium levels were 3.66 (2.59–5.18) ng/g and 170.0 (158.0–183.0) ng/g, respectively. Compared to infants of mothers with the highest blood selenium level, those of mothers with the lowest blood selenium level had neither a significant birth weight increase (9 g, 95% confidence interval: −6, 25) nor a significant odds ratio for small-for-gestational-age (0.903, 95% confidence interval: 0.748, 1.089). Compared to infants of mothers with the lowest blood mercury level, those of mothers with the highest blood mercury level had neither a significant birth weight reduction (−12 g, 95% confidence interval: −27, 4) nor a significant odds ratio for small-for-gestational-age (0.951, 95% confidence interval: 0.786, 1.150). Compared to infants of mothers with the lowest quartile of maternal blood mercury level, all infants of mothers with the highest quartile of maternal blood mercury level had a reduced birth head circumference of 0.073 cm (95% confidence interval: −0.134, −0.011). ConclusionsThere was no association between maternal blood mercury levels and small-for-gestational-age and birth weight among 15,444 pregnant women. In a Japanese population, which has a relatively higher blood mercury level than reported in Western population, reduced birth size was not found to be associated with blood mercury levels, with the exception of birth head circumference.

Prenatal mercury exposure and birth weight

Adverse effects of prenatal mercury exposure on pregnancy outcomes remain a public health concern. We assessed the relationship between prenatal mercury exposure and newborn anthropometric characteristics in 334 mother-child pairs from the early stages of pregnancy to delivery in Tokyo, Japan, between December 2010 and October 2012. We found a negative correlation between blood mercury levels during the first and second trimesters of gestation and birth weight (r = −0.134 and −0.119, respectively; p < 0.05). Multiple linear regression analysis confirmed the relationship between first-trimester maternal blood mercury levels and birth weight when adjusted for independent variables (β = −0.170, t = −2.762; p = 0.006). Mean mercury levels in umbilical cord blood were twice as high as maternal blood levels (10.15 ± 7.74 and 4.97 ± 3.25 μg/L, respectively; r = 0.974, p < 0.001). Our findings suggest that pregnant women and women of reproductive age should avoid mercury exposure, even at low levels, because of its potentially adverse effects on fetal development.

High Maternal Blood Mercury Level Is Associated with Low Verbal IQ in Children.

The objective of the present study was to investigate the relationship of IQ in children with maternal blood mercury concentration during late pregnancy. The present study is a component of the Mothers and Children's Environmental Health (MOCEH) study, a multi-center birth cohort project in Korea that began in 2006. The study cohort consisted of 553 children whose mothers underwent testing for blood mercury during late pregnancy. The children were given the Korean language version of the Wechsler Preschool and Primary Scale of Intelligence, revised edition (WPPSI-R) at 60 months of age. Multivariate linear regression analysis, with adjustment for covariates, was used to assess the relationship between verbal, performance, and total IQ in children and blood mercury concentration of mothers during late pregnancy. The results of multivariate linear regression analysis indicated that a doubling of blood mercury was associated with the decrease in verbal and total IQ by 2.482 (95% confidence interval [CI], 0.749–4.214) and 2.402 (95% CI, 0.526–4.279), respectively, after adjustment. This inverse association remained after further adjustment for blood lead concentration. Fish intake is an effect modifier of child IQ. In conclusion, high maternal blood mercury level is associated with low verbal IQ in children.

Mercury in the Early Life in Mexico to Environmental Toxicants (ELEMENT) Cohort: Levels in Women, Children, and Fish

Mercury in the Early Life in Mexico to Environmental Toxicants (ELEMENT) Cohort: Levels in Women, Children, and FishAbstract Number:2165 Nil Basu*, Rebecca Tutino, Zhenzhen Zhang, Brisa Sanchez, David Cantonwine, Jackie Goodrich, Emily Somers, Lourdes Schnaas, Maritsa Solano, Adriana Mercado, Karen Peterson, Howard Hu, Mara Tellez-Rojo Nil Basu* McGill University, Canada, E-mail Address: [email protected] Search for more papers by this author , Rebecca Tutino University of Michigan, United States, E-mail Address: [email protected] Search for more papers by this author , Zhenzhen Zhang University of Michigan, United States, E-mail Address: [email protected] Search for more papers by this author , Brisa Sanchez University of Michigan, United States, E-mail Address: [email protected] Search for more papers by this author , David Cantonwine University of Michigan, United States, E-mail Address: [email protected] Search for more papers by this author , Jackie Goodrich University of Michigan, United States, E-mail Address: [email protected] Search for more papers by this author , Emily Somers University of Michigan, United States, E-mail Address: [email protected] Search for more papers by this author , Lourdes Schnaas National Institute of Perinatology, Mexico, Mexico, E-mail Address: [email protected] Search for more papers by this author , Maritsa Solano National Institute of Public Health, Mexico, E-mail Address: [email protected] Search for more papers by this author , Adriana Mercado National Institute of Public Health, Mexico, E-mail Address: [email protected] Search for more papers by this author , Karen Peterson University of Michigan, United States, E-mail Address: [email protected] Search for more papers by this author , Howard Hu University of Toronto, Canada, E-mail Address: [email protected] Search for more papers by this author , and Mara Tellez-Rojo National Institute of Public Health, Mexico, E-mail Address: [email protected] Search for more papers by this author AbstractMercury is a global contaminant of concern that is now being acted upon via the UNEP Minamata Convention. While some geographic regions have tremendous resources or biomonitoring data to assess the efficacy of the Convention, there are many areas (such as Mexico) in which little is known about mercury exposures. The objective of this study was to characterize mercury levels in pregnant women, children, and commonly consumed fish and seafood samples from Mexico City. Total mercury levels in biomarkers from 348 pregnant women (blood from three trimesters and cord blood), 825 children (blood, hair, urine) and their mothers (hair), and 91 fish/seafood samples were determined utilizing resources of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) birth cohort. Maternal blood mercury levels correlated across three trimesters and averaged 3.4µg/L. Cord blood mercury averaged 4.7µg/L and correlated with trimester 3 maternal blood (but not trimesters 1 and 2). In children, blood, hair and urine mercury levels correlated and averaged 1.8µg/L, 0.6µg/g, and 0.9µg/L, respectively. Hair mercury was 0.5µg/g in mothers and correlated with child’s hair. Monthly consumption of canned tuna, fresh fish, seafood, and canned sardine was 3.0, 2.2, 0.4, and 1.0 times respectively in pregnant women. Mean mercury content in 7 of 23 fish/seafood species and 5 of 9 canned tuna brands purchased exceeded the guidance value of 0.3 ?g/g. In conclusion, mercury exposures in pregnant women and children from Mexico City, via biomarker studies, are generally 3-5 times greater than population surveys from the U.S., Canada, and elsewhere. In particular, mercury levels in 29-39% of the maternal participants exceeded the reference dose suggesting that 700,414 to 960,008 newborns per year in Mexico may be at increased risk of mercury-associated learning disabilities owing to in utero exposures.

Elevated prenatal methylmercury exposure in Nigeria: Evidence from maternal and cord blood

Methylmercury is a neurodevelopmental toxicant that is globally distributed though little is known about prenatal exposures in sub-Saharan Africa. The objective of the current study was to measure total mercury levels in cord blood and maternal blood from 95 mother-newborn pairs recruited from hospitals in Nnewi, Nigeria. The secondary aims of the study were to explore if demographic and dietary factors were associated with blood mercury levels, and to explore if mercury levels were associated with any self-reported health outcome and childbirth outcome. Maternal blood mercury levels averaged 3.6μgL−1 and ranged from 1.1μgL−1 to 9.5μgL−1. Cord blood mercury averaged 5.1μgL−1 and ranged from 1.2μgL−1 to 10.6μgL−1. The mean ratio of mercury in paired cord blood to maternal blood was 1.5 and it ranged from 0.4 to 3.2. Mercury in maternal and cord blood were significantly correlated (r=0.471). More than one-third of mothers reported eating fish at least once per day, and a weak (p=0.08) fish consumption-related increase in blood mercury was found. Cord blood mercury was positively and significantly associated with birth weight and length, and head and chest circumference. Mercury levels in 36% of the participants exceeded the biomonitoring guideline associated with the United States Environmental Protection Agency (U.S. EPA) reference dose for mercury. The study shows that pregnant women and their newborns are exposed to methylmercury and that their exposures are higher compared to general populations sampled from other regions of the world.

Effect of Low-Level Prenatal Mercury Exposure on Neonate Neurobehavioral Development in China

BackgroundThis study aimed to assess the effects of low-level prenatal mercury exposure on neonate neurobehavioral development in China. MethodsIn total, 418 mother-neonate pairs were included in the study. Maternal urine, hair, and blood samples and cord blood samples were used to document prenatal exposure to mercury. The Neonatal Behavioral Neurological Assessment was used to estimate neurobehavioral development in the neonates at 3 days of age. ResultsTotal mercury level was significantly higher in cord blood than that in maternal blood. A strong correlation was found between total mercury levels in maternal blood and those in cord blood (r = 0.7431; P < 0.0001). Trend analysis revealed that mothers who consumed more fish had higher blood and cord blood mercury levels (all P < 0.0001). Significant differences were also found between male and female cord blood mercury levels among groups with different fish consumption frequencies (all P < 0.0001). Cord blood mercury level was significantly associated with total Neonatal Behavioral Neurological Assessment scores (β = 0.03; standard error = 0.01; P = 0.0409), passive muscle tone (odds ratio = 1.07; 95% confidence interval = 1.12-1.13; P = 0.0071), and active muscle tone (odds ratio = 1.06; 95% confidence interval = 1.01-1.11; P = 0.0170) scores after adjustment, respectively. ConclusionsNeonatal neurodevelopment was associated with prenatal exposure to mercury. Women with high mercury levels should avoid intake seafood excessively during pregnancy. Long-term effects of exposure to mercury on childhood development need to be further explored.

ALSPAC Mercury Study and Fish Consumers

Golding et al. (2013) described regression analysis of dietary contributions to maternal blood mercury levels, nested within the Avon Longitudinal Study of Parents and Children (ALSPAC). Fish intake explained only about 7% of the variance in blood mercury, leading them to conclude somewhat cautiously that “limiting seafood intake during pregnancy may have a limited impact on prenatal blood mercury levels” (Golding et al. 2013). The media, however, has been quick to overinterpret the results, and Golding herself was quoted: We were pleasantly surprised to find that fish contributes such a small amount … to blood mercury levels…. We hope many more women will now consider eating more fish during pregnancy. (ALSPAC 2013) This is a much less cautious conclusion. ALSPAC and Golding are responsible for many valuable publications on human development, but ALSPAC was not designed to investigate mercury exposure and effects. The categories of white fish, oily fish, and shellfish used by Golding et al. (2013) do not meaningfully reflect mercury content. With respect to the internal validity of the exposure estimate from the dietary questionnaire, high-mercury and low-mercury fish are represented among both the “white” and “oily” categories, and shellfish generally have very little mercury. Thus, internal validity is limited by a poor exposure metric. External validity is more of a problem. The results of Golding et al. (2013) are not generalizable to the frequent consumers of fish who are most vulnerable to methylmercury exposure from fish during pregnancy. Women who ate fish frequently (> 3 times/week) made up 5.8 µg/L, the level corresponding to the U.S. Environmental Protection Agency (EPA) methylmercury reference dose of 0.1 µg/kg/day (U.S. EPA 2013). Although frequent fish consumers are a small part of the general population and the ALSPAC study, they are the population at risk for methylmercury exposure, particularly during pregnancy. Frequent fish consumers should reduce frequency or size of fish meals or choose among the many types of fish low in mercury. The mercury in fish is predominantly methylmercury, and for most people, fish is the only significant source of methylmercury (Bjornberg et al. 2005; Mahaffey et al. 2004). Methylmercury is the toxic form that is almost 100% absorbed from the gut, and it is readily translocated to both the brain and the fetus. This is the reason for public health concern regarding consumption of high-mercury fish by frequent fish-eaters. At low levels of fish intake, other, nonorganic forms and pathways influence blood mercury levels. The results of Golding et al. (2013) suggest that women who rarely eat fish and already have a low blood mercury concentration will not further lower the mercury by eating even less fish. The study, however, did not address the risk for the frequent fish-eater who has elevated blood mercury. It is not clear whether the developmental benefits ascribed to eating fish are due to its nutrients or to the healthy lifestyles that often correlate with eating fish frequently. We conclude that women who eat fish rarely or never may benefit both self and fetus by eating fish occasionally. Pregnant women should choose low-mercury fish species, particularly if they eat fish frequently (more than twice a week).

Mercury levels in maternal and cord blood and attained weight through the 24 months of life

Birth weight is a strong determinant of attained weight at early ages. Until now, many studies have reported that low birth weight corresponds with high mercury levels. However, the relationship between mercury exposure and attained weight of infant has not been well studied. Therefore, the aim of the present study was to assess the degree of prenatal exposure to mercury by measuring the total mercury levels in maternal and cord blood, and examine the relationship between the mercury level during pregnancy and the attained weight of infant during the first 24 months of life. The prospective cohort study of Mothers and Children's Environmental Health (MOCEH) was built up in 2006, and 921 mother–infant pairs were recruited. Information on the socio-demographic characteristics, health behavior and environmental exposure were collected from an interview with trained nurses. After delivery, infants and mothers were followed up at 6, 12 and 24 months and the weights of the infants were measured. The mercury concentrations in the late maternal blood (β = − 0.19. p = 0.05) and cord blood (β = − 0.36. p = 0.01) were negatively associated with the infants' attained weight over the first 24 months of age. The infants' attained weight in the small for their gestational age (SGA) group was lower than the normal birth weight group at the highest quartile of the mercury level. Therefore, efforts should be made to reduce the mercury level in the maternal blood at late pregnancy and cord blood. Further research on the possible harmful effects of prenatal mercury exposure on postnatal growth is recommended.

Health Effects of Mercury Exposure through Fish

Mercury is a toxic, persistent pollutant that bioaccumulates and biomagnifies through food webs. People are exposed to methyhnercruy mainly through their diet, especially through the consumption of freshwater and marine fish and of other animals that consume fish (e.g., marine mammals). All humans are exposed to low levels of mercury. Dietary patterns can increase exposure to a fish-eating population where the fish and seafood are contaminated with mercury. The primary toxicity targets of mercury and mercury compounds are the nervous system, kidneys, and cardiovascular system. It is generally accepted that developing organ systems are most sensitive to the toxic effects of mercury. The fetal-brain mercury levels appear to be significantly higher than the maternal-blood mercury levels, and the developing central nervous system of the fetus is currently regarded as the main system of concern as it demonstrates the greatest sensitivity. The subpopulation that may be at greater risk for mercury toxicity are those exposed to higher levels of methylmercury due to carnivorous fish, including sharks.

Methylmercury and IQ: Dose–Response Estimate of Prenatal Effect

Vol. 115, No. 4 EnvironewsOpen AccessMethylmercury and IQ: Dose–Response Estimate of Prenatal Effect Valerie J. Brown Valerie J. Brown Search for more papers by this author Published:1 April 2007https://doi.org/10.1289/ehp.115-a212aAboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Methylmercury, the most biologically active mercury compound, is well known to cause serious health effects, particularly to the developing fetal nervous system. Effects can include attention deficits as well as IQ, motor, memory, and language impairment. A new analysis now combines data from three earlier studies to produce an integrated estimate of the dose–response relationship between maternal mercury exposure during pregnancy and lowered childhood IQ [EHP 115:609–615; Axelrad et al.].The authors analyzed combined IQ data from three longitudinal studies conducted in the Faroe Islands, the Seychelles Islands, and New Zealand. These studies measured a variety of neurodevelopmental end points, including IQ, attention, and motor skills. The range of pre-natal exposures in the three populations is comparable to those of some U.S. populations. For example, a 2003 study found the lowest maternal blood mercury level in the Faroe Islands to be 0.53 μg/L, and the CDC reported in 2004 that more than half of U.S. women had blood mercury concentrations higher than this. Geometric mean blood concentrations in the United States from 1999 to 2002 were 0.92 μg/L for women of childbearing age; for children the mean was 0.33 μg/L.The New Zealand and Seychelles studies reported results in terms of ppm of hair mercury, whereas the Faroe Islands study reported effects in terms of ppb of cord blood mercury. So the team converted the Faroe Islands results to their equivalents in units of hair mercury. They found a childhood IQ decrease of 0.18 points for each ppm rise in maternal hair mercury. The team assumed a linear, nonthreshold dose–response curve. However, they noted that if very low exposures produce a steeper curve, as has been found recently with childhood lead exposure, their calculation may underestimate the effects of prenatal mercury exposure. Similarly, certain cognitive abilities such as word retrieval and retention of verbally presented information are not captured by IQ scores, so relying only on IQ as a measure of cognitive function will also underestimate mercury’s effects.Eating fish is the most common route of human exposure to methylmercury. In 2004 the FDA and the EPA issued a joint statement advising women of childbearing age and children to limit their weekly consumption of commercially caught fish to 12 oz (6 oz for locally caught fish) in order to avoid harmful exposure. The EPA has set a reference dose of 0.1 μg/kg/day for methylmercury as an estimate of the daily exposure unlikely to cause harm over a lifetime.Methylmercury’s effect on IQ is separate from its effect on attention and motor skills. But because IQ is a well-established end point used in cost–benefit and economic analyses of the effects of environmental contaminants, establishing the dose–response relationship for IQ is a first step in quantifying the benefits of reducing mercury exposure.Smart moveA new analysis takes a first step toward quantifying the benefits of reducing mercury exposure, which may include avoiding IQ deficits.FiguresReferencesRelatedDetails Vol. 115, No. 4 April 2007Metrics About Article Metrics Publication History Originally published1 April 2007Published in print1 April 2007 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Mercury levels in cord blood and meconium of healthy newborns and venous blood of their mothers: Clinical, prospective cohort study

The purpose of this study is to investigate the chronic mercury intoxication in pregnant women and newborns living in Istanbul, Turkey. The research was carried out as a prospective with 143 pregnant women and their newborns. Venous blood from the mother, cord blood from the neonate, and meconium were collected for mercury analysis. Frequency of fish and vegetable-eating and the number of teeth filled were investigated. Analyses were made in cold vapor Atomic Absorption Spectrophotometer (AAS, microg/L). Mercury levels were 0.38+/-0.5 microg/L (0-2.34) in venous blood of pregnant women, 0.50+/-0.64 microg/L (0-2.36) in umbilical cord blood and 9.45+/-13.8 microg/g (0-66.5) in meconium. Maternal blood mercury level was lower than the known toxic limit for humans (EPA, 5 microg/L). Mercury levels of the maternal venous blood were significantly correlated with umbilical cord blood. The primary risk factors affecting mercury levels were eating fishmeals more than twice a week and having filled teeth more than five. The fact that the mother had a regular vegetable diet everyday reduced the mercury levels. Increased levels of mercury in the mother and umbilical cord blood could lead to retarded newborns' weight and height. Pregnant women living in Istanbul may be not under the risk of chronic mercury intoxication. Fish consumption more than twice per week and tooth-filling of mother more than five may increase mercury level. On the contrary, regular diet rich in vegetable decreases the mercury level.

Mercury Concentrations of Maternal and Umbilical Cord Blood in Korean Pregnant Women: Preliminary Study

Objectives: To evaluate the level of maternal and prenatal mercury exposure and to analyze the related factors. Methods: Fifty-nine pregnant women were recruited into this study after obtaining informed consent. Samples were collected at delivery from normal pregnant women who were living in the city of Busan, Korea. Mercury concentrations in maternal and umbilical cord blood samples were measured using a gold-amalgam collection method. The total and methyl mercury levels of 36 of the 59 pregnant women were analyzed after randomization, and the results were compared. Results: The mean total mercury concentration was 3.16±1.21 ppb and 5.43±2.22 ppb in maternal and cord blood, respectively. The average, maternal blood mercury level was lower than the prescribed toxic limit for human (WHO, 5 ppb), whereas the cord blood mercury was higher. The mercury exposure level exceeded the WHO recommendation in 5 (8.47%) cases of maternal blood and 29 of (49.15%) cord blood. There was a significant correlation between maternal and cord blood mercury concentrations. Total mercury and methyl mercury concentrations of the 36 random pregnant women were 3.06±1.17 ppb, and 2.60±1.11 ppb in maternal blood, and 5.20±2.36 ppb, and 4.70±1.97 ppb in cord blood, respectively. Methyl mercury accounted for 85.0% of the total mercury in maternal blood and 90.4% in cord blood. There was a significant correlation between total and methyl mercury concentrations.

The Effect of Fish Consumption on Blood Mercury Levels of Pregnant Women

In the present study, we examined the relationship between average fish consumption, as well as the type of fish consumed and levels of mercury in the blood of pregnant women. We also performed follow-up studies to determine if blood mercury levels were decreased after counseling and prenatal education. To examine these potential relationships, pregnant women were divided into two groups: a study group was educated to restrict fish intake, whereas a control group did not receive any prenatal education regarding fish consumption. We measured blood mercury level and performed follow-up studies during the third trimester to examine any differences between the two groups. Out of the 63 pregnant women who participated in our study, we performed follow-up studies with 19 pregnant women from the study group and 12 pregnant women from control group. The average initial blood mercury level of both groups was 2.94 µg/L, with a range of 0.14 to 10.75 µg/L. Blood mercury level in the group who ate fish more than four times per month was significantly higher than that of the group who did not consume fish (p = 0.02). In follow-up studies, blood mercury levels were decreased in the study group but slightly increased in the control group (p = 0.014). The maternal blood mercury level in late pregnancy was positively correlated with mercury levels of cord blood (r = 0.58, p = 0.047), which was almost twice the level found in maternal blood. Pregnant women who consume a large amount of fish may have high blood mercury levels. Further, cord blood mercury levels were much higher than that of maternal blood. Because the level of fish intake appears to influence blood mercury level, preconceptual education might be necessary in order decrease fish consumption.

Effects of Prenatal Exposure to Mercury on Cognitive and Psychomotor Function in One-Year-Old Infants: Epidemiologic Cohort Study in Poland

The aim of the study is to assess the cognitive and psychomotor status of 1-year-old infants whose mothers were exposed to low, but varying, amounts of mercury during pregnancy. Mercury levels in cord and maternal blood at delivery were used to assess prenatal environmental exposure to mercury. Bayley Scales of Infant Development were used to assess neurobehavioral health outcomes. The cohort consisted of 233 infants who were born at 33 to 42 weeks of gestation between January 2001 and March 2003 to mothers attending ambulatory prenatal clinics in the first and second trimesters of pregnancy. Enrollment included only nonsmoking women with singleton pregnancies between the ages of 18 and 35 years who were free from chronic diseases. The geometric mean (GM) for maternal blood mercury level for the group of infants with normal neurocognitive performance was lower (GM = 0.52 mug/L; 95% confidence interval [CI], 0.46-0.58) than that observed in the group with delayed performance (GM = 0.75 mug/L; 95% CI, 0.59-0.94), and this difference was significant (p = 0.010). The GM of cord blood mercury level in the normal group also was lower (GM = 0.85 mug/L; 95% CI, 0.78-0.93) than that observed in the group with delayed performance (GM = 1.05 mug/L; 95% CI, 0.87-1.27), and this difference was of borderline significance (p = 0.070). The relative risk (RR) for delayed performance increased more than threefold (RR = 3.58; 95% CI, 1.40-9.14) if cord blood mercury level was greater than 0.80 mug/L. Risk for delayed performance in the group of infants with greater maternal mercury levels (>0.50 mug/L) also was significantly greater (RR = 2.82; 95% CI, 1.17-6.79) compared with children whose mothers had mercury levels less than 0.50 mug/L. The results may be of public health importance because delayed psychomotor or mental performance in infants is assumed to be an indicator of later neurocognitive development in children, which may persist into adult life.

MATERNAL MERCURY LEVELS ARE RELATED TO NEURO-COGNITIVE DEVELOPMENT AT AGE 6 MONTHS

ISEE-79 Introduction: Coal-burning in Poland is a major source of environmental mercury exposure, via air pollution or bio- accumulation in the food chain. Aim: The purpose of the study was to assess the neuro-cognitive status of 6-month-old infants whose mothers were exposed to low but varying amounts of mercury during pregnancy. Methods: Mercury levels in maternal blood at delivery were used to assess environmental exposure to mercury; and the Fagan Test of Infant Intelligence (FTII) assessed visual recognition memory (VRM). The cohort consisted of 233 infants of mothers who gave birth to babies at 33–42 weeks of gestation, between January 2001 and March 2003. None of the children manifested obvious neurological abnormalities at the development check-up. Results: VRM in 6-month-olds, as measured by novelty scores from the FTII, was inversely related to maternal blood mercury levels. The estimated risk of scoring in the suspected or at risk groups for developmental delay (FTII risk group classifications 2+3) due to higher mercury blood levels (above 0.50 μg/L) was threefold greater (OR = 3.21, CI = 1,12 to 9.20), than for lower mercury blood levels (≤ 0.5 μg/dL), after adjusting for potential confounders such as gestational age, gender of the child, maternal education, exposure to environmental tobacco smoke and lead. Conlcusion: The results of the study suggest that the Fagan Test may be a sensitive end-point for low level mercury exposure and that the group of infants at risk of delayed neuro-cognitive development may be defined by a maternal blood mercury level exceeding 0.5 μg/L at delivery. As the risk of reduced VRM attributable to this exposure level is 63%, a large portion of developmental delay could be prevented by reducing maternal blood mercury level below 0.5 μg/L.

Comparison of mercury levels in maternal blood, fetal cord blood, and placental tissues

Previous studies have reported that mercury accumulates in cord blood during pregnancy. This study was carried out to determine where in cord blood the mercury accumulates, i.e., in cord erythrocytes, in cord plasma, or in both, and to determine whether the predominant form of mercury which accumulates is methyl or inorganic mercury. From our data it is clear that methyl mercury accumulates in cord erythrocytes: A total of 30% more methyl mercury was found in fetal erythrocytes than in maternal erythrocytes. Also correlation analysis of the methyl mercury levels in maternal and fetal erythrocytes showed a strong correlation (r = 0.87). In regard to inorganic mercury, the highest concentration was found in the placenta, suggesting a barrier role, but a significant correlation (r = 0.62) was also found between the maternal and fetal plasma levels of inorganic mercury. Moreover, the inorganic mercury concentration per gram of plasma was higher in fetal cord plasma than in maternal plasma. Overall, the relative levels of methyl and inorganic mercury reported here varied considerably in maternal and fetal erythrocytes, plasma, and in the placenta, but all of the levels were low (<6 ng Hg/gm of tissue) and in agreement with “total” mercury levels reported by others.