Varying coefficient function models to explore interactions between maternal nutritional status and prenatal methylmercury toxicity in the Seychelles Child Development Nutrition Study

Role of one-carbon nutrient intake and diabetes during pregnancy in children's growth and neurodevelopment: A 2-year follow-up study of a prospective cohort

BACKGROUND & AIMS

Both maternal metabolic dysregulation, e.g., gestational diabetes mellitus (GDM), and maternal supply of nutrients that participate in one-carbon (1C) metabolism, e.g., folate, choline, betaine, and vitamin B12, have been demonstrated to influence epigenetic modification such as DNA methylation, thereby exerting long-lasting impacts on growth and development of offspring. This study aimed to determine how maternal 1C nutrient intake was associated with DNA methylation and further, development of children, as well as whether maternal GDM status modified the association in a prospective cohort.

METHODS

In this study, women with (n = 18) and without (n = 20) GDM were recruited at 25-33 weeks gestation. Detailed dietary intake data was collected by 3-day 24-h dietary recall and nutrient levels in maternal blood were also assessed at enrollment. The maternal-child dyads were invited to participate in a 2-year follow-up during which anthropometric measurement and the Bayley Scales of Infant and Toddler Development™ Screening Test (Third Edition) were conducted on children. The association between maternal 1C nutrients and children's developmental outcomes was analyzed with a generalized linear model controlling for maternal GDM status.

RESULTS

We found that children born to mothers with GDM had lower scores in the language domain of the Bayley test (p = 0.049). Higher maternal food folate and choline intakes were associated with better language scores in children (p = 0.01 and 0.025, respectively). Higher maternal food folate intakes were also associated with better cognitive scores in children (p = 0.002). Higher 1C nutrient intakes during pregnancy were associated with lower body weight of children at 2 years of age (p < 0.05). However, global DNA methylation of children's buccal cells was not associated with any maternal 1C nutrients.

CONCLUSIONS

In conclusion, higher 1C nutrient intake during pregnancy was associated with lower body weight and better neurodevelopmental outcomes of children. This may help overcome the lower language scores seen in GDM-affected children in this cohort. Studies in larger cohorts and with a longer follow-up duration are needed to further delineate the relationship between prenatal 1C nutrient exposure, especially in GDM-affected pregnancies, and offspring health outcomes.

Mercury exposure in the Norwegian Mother, Father, and Child Cohort Study - measured and predicted blood concentrations and associations with birth weight

Background

Blood total mercury concentration (BTHg) predominantly contains methyl Hg from seafood, and less inorganic Hg. Measured BTHg is often available only in a small proportion of large cohort study samples. Associations between estimated dietary intake of total Hg (THg) and lower birth weight within strata of maternal seafood intake was previously reported in the Norwegian Mother, Father, and Child Cohort Study (MoBa). However, maternal seafood consumption was associated with increased birth weight, indicating negative confounding by seafood in the association between THg intake and birth weight. Using predicted BTHg as a proxy for measured BTHg, we hypothesized that predicted BTHg would be associated with decreased birth weight.

Objectives

To develop and validate a prediction model for BTHg in MoBa and to examine the association between predicted BTHg and birth weight in the MoBa population.

Methods

Using linear regression, measured maternal BTHg (n = 1437) was used to build the best fitting model (highest R-squared value). Model validation (n = 1436) was based on correlation and weighted Kappa (Кw). Associations between predicted BTHg in the MoBa population (n = 86,775) or measured BTHg (n = 3590) and birth weight were assessed by multivariate linear regression models.

Results

The best fitting model had R-squared = 0.3 and showed strong correlation (r = 0.53, p < 0.001) between predicted and measured BTHg. Cross-classification (quintiles) showed 73 % correctly classified and 3.3 % grossly misclassified, with Кw of 0.37. Measured BTHg was not associated with birth weight. Predicted BTHg was significantly associated with higher birth weight. There were no trends in birth weight with increasing quintiles of measured or predicted BTHg after stratification into high or low seafood consumption.

Conclusions

The results indicate that prediction of BTHg did not overcome negative confounding of the association between Hg exposure and birth weight by seafood intake. Furthermore, effect on birth weight of toxicological concern is unexpected in our observed BTHg range.

Associations of an industry-relevant metal mixture with verbal learning and memory in Italian adolescents: The modifying role of iron status

BACKGROUND

Biomarker concentrations of metals are associated with neurodevelopment, and these associations may be modified by nutritional status (e.g., iron deficiency). No prior study on associations of metal mixtures with neurodevelopment has assessed effect modification by iron status.

OBJECTIVES

We aimed to quantify associations of an industry-relevant metal mixture with verbal learning and memory among adolescents, and to investigate the modifying role of iron status on those associations.

METHODS

We used cross-sectional data from 383 Italian adolescents (10-14 years) living in proximity to ferroalloy industry. Verbal learning and memory was assessed using the California Verbal Learning Test for Children (CVLT-C), and metals were quantified in hair (manganese, copper, chromium) or blood (lead) using inductively coupled plasma mass spectrometry. Serum ferritin, a proxy for iron status, was measured using immunoassays. Covariate-adjusted associations of the metal mixture with CVLT subtests were estimated using Bayesian Kernel Machine Regression, and modification of the mixture associations by ferritin was examined.

RESULTS

Compared to the 50th percentile of the metal mixture, the 90th percentile was associated with a 0.12 standard deviation [SD] (95% CI = -0.27, 0.50), 0.16 SD (95% CI = -0.11, 0.44), and 0.11 SD (95% CI = -0.20, 0.43) increase in the number of words recalled for trial 5, long delay free, and long delay cued recall, respectively. For an increase from its 25th to 75th percentiles, copper was beneficially associated the recall trials when other metals were fixed at their 50th percentiles (for example, trial 5 recall: β = 0.31, 95% CI = 0.14, 0.48). The association between copper and trial 5 recall was stronger at the 75th percentile of ferritin, compared to the 25th or 50th percentiles.

CONCLUSIONS

In this metal mixture, copper was beneficially associated with neurodevelopment, which was more apparent at higher ferritin concentrations. These findings suggest that metal associations with neurodevelopment may depend on iron status, which has important public health implications.

Environmental Metal Exposure, Neurodevelopment, and the Role of Iron Status: a Review

PURPOSE OF REVIEW

Exposure to environmental metals, like lead (Pb), manganese (Mn), and methylmercury (Me-Hg), has consistently been implicated in neurodevelopmental dysfunction. Recent research has focused on identifying modifying factors of metal neurotoxicity in childhood, such as age, sex, and co-exposures. Iron (Fe) status is critical for normal cognitive development during childhood, and current mechanistic, animal, and human evidence suggests that Fe status may be a modifier or mediator of associations between environmental metals and neurodevelopment. The goals of this review are to describe the current state of the epidemiologic literature on the role of Fe status (i.e., hemoglobin, ferritin, blood Fe concentrations) and Fe supplementation in the relationship between metals and children's neurodevelopment, and to identify research gaps.

RECENT FINDINGS

We identified 30 studies in PubMed and EMBASE that assessed Fe status as a modifier, mediator, or co-exposure of associations of Pb, Me-Hg, Mn, copper (Cu), zinc (Zn), arsenic (As), or metal mixtures measured in early life (prenatal period through 8 years of age) with cognition in children. In experimental studies, co-supplementation of Fe and Zn was associated with better memory and cognition than supplementation with either metal alone. Several observational studies reported interactions between Fe status and Pb, Mn, Zn, or As in relation to developmental indices, memory, attention, and behavior, whereby adverse associations of metals with cognition were worse among Fe-deficient children compared to Fe-sufficient children. Only two studies quantified joint associations of complex metal mixtures that included Fe with neurodevelopment, though findings from these studies were not consistent. Findings support memory and attention as two possible cognitive domains that may be both vulnerable to Fe deficiency and a target of metals toxicity. Major gaps in the literature remain, including evaluating Fe status as a modifier or mediator of metal mixtures and cognition. Given that Fe deficiency is the most common nutritional deficiency worldwide, characterizing Fe status in studies of metals toxicity is important for informing public health interventions.

Relationship between thyroid hormone parameters and exposure to a mixture of organochlorine pesticides, mercury and nutrients in the cord blood of newborns

The fetus is prenatally exposed to a mixture of organochlorine pesticides (OCPs), mercury (Hg), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and selenium (Se) through maternal seafood consumption in real-life scenario. Prenatal exposure to these contaminants and nutrients has been suggested to affect thyroid hormone (TH) status in newborns, but the potential relationships between them are unclear and the joint effects of the mixture are seldom analyzed. The aim of the study is to investigate the associations of prenatal exposure to a mixture of OCPs, Hg, DHA, EPA and Se with TH parameters in newborns. 228 mother-infant pairs in Shanghai, China were included. We measured 20 OCPs, total Hg, DHA, EPA and Se in cord blood samples as exposure variables. The total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3), free triiodothyronine (FT3), and thyroid-stimulating hormone (TSH) levels and the FT3/FT4 ratio in cord serum were determined as outcomes. Using linear regression models, generalized additive models and Bayesian kernel machine regression, we found dose-response relationships of the mixture component with outcomes: among the contaminants, p,p'-DDE was the most important positive predictor of TT3, while HCB was predominantly positively associated with FT3 and the FT3/FT4 ratio, indicating different mechanisms underlying these relationships; among the nutrients, EPA was first found to be positively related to the FT3/FT4 ratio. Additionally, we found suggestive evidence of interactions between p,p'-DDE and HCB on both TT3 and FT3, and EPA by HCB interactions for TT3, FT3 and FT3/FT4 ratio. However, the overall effects of the mixture on thyroid hormone parameters were not significant. Our result suggests that prenatal exposure to p,p'-DDE, HCB and EPA as part of a mixture might affect thyroid function of newborns in independent and interactive ways. The potential biological mechanisms merit further investigation.

Maternal methylmercury exposure through rice ingestion and child neurodevelopment in the first three years: a prospective cohort study in rural China

BACKGROUND

Rice is an important dietary source for methylmercury; however, rice does not contain the same beneficial nutrients as fish. Our main objective was to assess associations of prenatal methylmercury exposure through rice ingestion with child neurodevelopment in rural China.

METHODS

Eligible peripartum women were enrolled (n = 391), provided peripartum hair samples, and children's neurodevelopment was assessed at 12 months (n = 264, 68%) and 36 months (n = 190, 48%) using the Bayley Scales of Infant Development, 2nd Edition, including the Mental Developmental Index (MDI) and the Psychomotor Developmental Index (PDI). Associations between prenatal methylmercury exposure during the third trimester [log2 maternal hair total mercury (THg)] and child's neurodevelopment were assessed using linear mixed models for repeated measures.

RESULTS

In adjusted models, a doubling in maternal hair THg corresponded to a 1.3-point decrement in the MDI score [95% confidence interval (CI): - 2.6, - 0.14], and a 1.2-point decrement in the PDI score (95% CI: - 2.6, 0.14). Overall, adverse associations between maternal hair THg and MDI scores attenuated over time. However, associations were robust and stable over time among children whose primary caregiver was their parent(s). During the study follow-up, an increasing proportion of children were raised by grandparents (12 months: 9% versus 36 months: 27%), a trend associated with rural-to-urban parental migration for work.

CONCLUSIONS

For young children living in rural China, a biomarker of prenatal methylmercury exposure was associated with decrements in cognitive function assessed between 12 and 36 months of age. Changes in the family structure over the study follow-up time interval potentially impacted children's sensitivity to prenatal methylmercury exposure.

Environmental Health Research in Africa: Important Progress and Promising Opportunities

The World Health Organization in 2016 estimated that over 20% of the global disease burden and deaths were attributed to modifiable environmental factors. However, data clearly characterizing the impact of environmental exposures and health endpoints in African populations is limited. To describe recent progress and identify important research gaps, we reviewed literature on environmental health research in African populations over the last decade, as well as research incorporating both genomic and environmental factors. We queried PubMed for peer-reviewed research articles, reviews, or books examining environmental exposures and health outcomes in human populations in Africa. Searches utilized medical subheading (MeSH) terms for environmental exposure categories listed in the March 2018 US National Report on Human Exposure to Environmental Chemicals, which includes chemicals with worldwide distributions. Our search strategy retrieved 540 relevant publications, with studies evaluating health impacts of ambient air pollution (n=105), indoor air pollution (n = 166), heavy metals (n = 130), pesticides (n = 95), dietary mold (n = 61), indoor mold (n = 9), per- and polyfluoroalkyl substances (PFASs, n = 0), electronic waste (n = 9), environmental phenols (n = 4), flame retardants (n = 8), and phthalates (n = 3), where publications could belong to more than one exposure category. Only 23 publications characterized both environmental and genomic risk factors. Cardiovascular and respiratory health endpoints impacted by air pollution were comparable to observations in other countries. Air pollution exposures unique to Africa and some other resource limited settings were dust and specific occupational exposures. Literature describing harmful health effects of metals, pesticides, and dietary mold represented a context unique to Africa. Studies of exposures to phthalates, PFASs, phenols, and flame retardants were very limited. These results underscore the need for further focus on current and emerging environmental and chemical health risks as well as better integration of genomic and environmental factors in African research studies. Environmental exposures with distinct routes of exposure, unique co-exposures and co-morbidities, combined with the extensive genomic diversity in Africa may lead to the identification of novel mechanisms underlying complex disease and promising potential for translation to global public health.

Relationships between seafood consumption during pregnancy and childhood and neurocognitive development: Two systematic reviews

Abundant data are now available to evaluate relationships between seafood consumption in pregnancy and childhood and neurocognitive development. We conducted two systematic reviews utilizing methodologies detailed by the Dietary Guidelines for Americans Scientific Advisory Committee 2020-2025. After reviewing 44 publications on 106,237 mother-offspring pairs and 25,960 children, our technical expert committee developed two conclusion statements that included the following: "Moderate and consistent evidence indicates that consumption of a wide range of amounts and types of commercially available seafood during pregnancy is associated with improved neurocognitive development of offspring as compared to eating no seafood. Overall, benefits to neurocognitive development began at the lowest amounts of seafood consumed (∼4 oz/wk) and continued through the highest amounts, above 12 oz/wk, some range up to >100 oz/wk.", "This evidence does not meet the criteria for "strong evidence" only due to a paucity of randomized controlled trials that may not be ethical or feasible to conduct for pregnancy" and "Moderate and consistent evidence indicates that consumption of >4 oz/wk and likely >12 oz/wk of seafood during childhood has beneficial associations with neurocognitive outcomes." No net adverse neurocognitive outcomes were reported among offspring at the highest ranges of seafood intakes despite associated increases in mercury exposures. Data are insufficient for conclusive statements regarding lactation, optimal amounts, categories or specific species characterized by mercury content and neurocognitive development; although there is some evidence that dark/oily seafood may be more beneficial. Research was conducted in healthy women and children and is generalizable to US populations. Assessment of seafood as a whole food integrates inherently integrates any adverse effects from neurotoxicants, if any, and benefits to neurocognition from omega-3 fats, as well as other nutrients critical to optimal neurological development. Understanding of the effects of seafood consumption on neurocognition can have significant public health implications.

Sex hormones and n-3 fatty acid metabolism

α-Linolenic acid (ALA) is an n-3 fatty acid found in plant-derived foods such as linseeds and linseed oil. Mammals can convert this essential fatty acid into longer-chain fatty acids including EPA, docosapentaenoic acid (DPA) and DHA. Women demonstrate greater increases in the EPA status after ALA supplementation than men, and a growing body of animal model research identifies mechanisms by which sex hormones such as oestrogen and progesterone interact with the synthesis of EPA and DHA. Alternatively, EPA, DPA and DHA can be consumed directly, with oily fish being a rich dietary source of these nutrients. However, current National Diet and Nutrition Data reveals a median oily fish intake of 0 g daily across all age ranges and in both sexes. As longer-chain n-3 fatty acids have a crucial role in fetal and neonatal brain development, advice to consume dietary ALA could prove to be a pragmatic and acceptable alternative to advice to consume fish during pregnancy, if benefits upon tissue composition and functional outcomes can be demonstrated. Further research is required to understand the effects of increasing dietary ALA during pregnancy, and will need to simultaneously address conflicts with current dietary advice to only eat 'small amounts' of vegetable oils during pregnancy. Improving our understanding of sex-specific differences in fatty acid metabolism and interactions with pregnancy has the potential to inform both personalised nutrition advice and public health policy.

Relation of prenatal low-level mercury exposure with early child neurobehavioral development and exploration of the effects of sex and DHA on it

BACKGROUND

The extent to which low-level, in utero mercury exposure affects child neurobehavioral development during early childhood has been inconclusive. In addition, the effects of sex and docosahexaenoic acid (DHA) on these relationships remain unclear and controversial.

OBJECTIVES

This study aimed to explore the associations between prenatal low-level mercury exposure and child neurobehavioral development during the neonatal and toddler periods and to examine the potential confounding or interactive effects of sex and DHA status on these relationships.

METHODS

This longitudinal study included 286 mother-child pairs in Shanghai, China, whose cord blood samples were analyzed for total mercury, DHA, other nutrients and coexposure contaminants possibly due to maternal consumption of seafood. Children's neurobehavioral development was assessed with the Neonatal Behavioral Neurological Assessment (NBNA) three days after birth and the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) at 18 months of age.

RESULTS

Cord blood mercury concentration, with geometric mean of 2.00 μg/l, was related to poorer NBNA performance but unrelated to BSID-III scores with adjustment for DHA and other covariates. Cord serum DHA was positively associated with motor development assessed by the BSID-III. The interaction was found between mercury and DHA on the NBNA score, and the inverse relation of cord blood mercury with NBNA was significant only among the children with lower DHA levels (<45.54 μg/ml). Additional adjustment for DHA didn't change the associations between cord blood mercury and neurodevelopmental outcomes substantially. The mercury by sex interaction for language of BSID-III was borderline significant.

CONCLUSIONS

Our research provides initial evidence for the negative effects of prenatal low-level mercury exposure on neonates' neurobehavioral development. Prenatal DHA status may modify the relationship between cord blood mercury level and neonatal neurobehavioral development, but the confounding effects of DHA were not observed. Further studies are warranted before the causality of the observed associations can be determined.

Analysis of Nonlinear Associations between Prenatal Methylmercury Exposure from Fish Consumption and Neurodevelopmental Outcomes in the Seychelles Main Cohort at 17 Years

BACKGROUND

The Seychelles Child Development Study has been examining the relationship between prenatal methylmercury (MeHg) exposure from consuming fish during pregnancy and child development. This study re-analyzes seven outcomes in the 17 year Main Cohort data to determine if there are nonlinear or non-homogeneous (subgroup) associations that were not identified in the linear analysis.

METHODS

We adopted two statistical approaches. First, we carried out an additive nonlinear analysis assuming homogeneous prenatal MeHg-outcome relationships to explore overall associations. Second, we applied the regression tree to the Woodcock-Johnson Calculation subtest (it was significantly associated in earlier analyses) and identified 4 clusters based on covariates. Then we used additive models to assess the prenatal MeHg association in each of the four clusters for all seven outcomes. This approach assumes nonlinear associations in each cluster and non-homogeneous associations between clusters.

RESULTS

The additive nonlinear analysis yielded prenatal MeHg curves similar to the linear analysis. For the regression tree analysis, the curves relating prenatal MeHg to outcomes between the 4 clusters differed and some crossed at higher prenatal MeHg levels, suggesting non-homogeneity in the upper range of exposure. Additionally, some of the curves suggested a possible non-linear relationship within the range of exposure we studied.

CONCLUSION

This non-linear analysis supports the findings from the linear analysis. It shows little evidence to support an adverse association of prenatal MeHg exposure through maternal consumption of fish contaminated with natural background levels. However, the tree analysis suggests that the prenatal exposure/outcome relationship may not be homogeneous across all individuals and that some subpopulations may have an adverse association in the upper range of the exposures studied. More robust data in the higher levels of exposure in this cohort are needed to confirm this finding.

Prenatal methylmercury exposure and language delay at three years of age in the Norwegian Mother and Child Cohort Study

Prenatal methylmercury (MeHg) exposure and its possible neurodevelopmental effects in susceptible children are of concern. Studies of MeHg exposure and negative health outcomes have shown conflicting results and it has been suggested that co-exposure to other contaminants and/or nutrients in fish may confound the effect of MeHg. Our objective was to examine the association between prenatal exposure to MeHg and language and communication development at three years, adjusting for intake of fish, n-3 long chain polyunsaturated fatty acids (n-3 LCPUFAs) and co-exposure to dioxins and dioxin like polychlorinated biphenyls (dl-PCBs). We used data from the Norwegian Mother and Child Cohort Study (MoBa) collected between 2002 and 2008. The study sample consisted of 46,750 mother-child pairs. MeHg exposure was calculated from reported fish intake during pregnancy by a FFQ in mid-pregnancy. Children's language and communication skills were measured by maternal report on the Dale and Bishop grammar rating and the Ages and Stages communication scale (ASQ). We estimated odds ratios (OR) and 95% confidence intervals (CI) using logistic regressions. Median MeHg exposure was 1.3μg/day, corresponding to 0.14μg/kgbw/week. An exposure level above the 90th percentile (>2.6μg/day, >0.29μg/kgbw/week) was defined as the high MeHg exposure. Results indicated an association between high MeHg exposure and unintelligible speech with an adjusted OR 2.22 (1.31, 3.72). High MeHg exposure was also associated with weaker communication skills adjusted OR 1.33 (1.03, 1.70). Additional adjustment for fish intake strengthened the associations, while adjusting for PCBs and n-3 LCPUFA from diet or from supplements had minor impact. In conclusion, significant associations were found between prenatal MeHg exposure above the 90th percentile and delayed language and communication skills in a generally low exposed population.

Mercury, selenium and fish oils in marine food webs and implications for human health

Humans who eat fish are exposed to mixtures of healthful nutrients and harmful contaminants that are influenced by environmental and ecological factors. Marine fisheries are composed of a multitude of species with varying life histories, and harvested in oceans, coastal waters and estuaries where environmental and ecological conditions determine fish exposure to both nutrients and contaminants. Many of these nutrients and contaminants are thought to influence similar health outcomes (i.e., neurological, cardiovascular, immunological systems). Therefore, our understanding of the risks and benefits of consuming seafood require balanced assessments of contaminants and nutrients found in fish and shellfish. In this paper, we review some of the reported benefits of fish consumption with a focus on the potential hazards of mercury exposure, and compare the environmental variability of fish oils, selenium and mercury in fish. A major scientific gap identified is that fish tissue concentrations are rarely measured for both contaminants and nutrients across a range of species and geographic regions. Interpreting the implications of seafood for human health will require a better understanding of these multiple exposures, particularly as environmental conditions in the oceans change.

Low-level mercury, omega-3 index and neurobehavioral outcomes in an adult US coastal population

BACKGROUND

Neurodevelopmental effects of omega-3 fatty acids and mercury from fish consumption have been characterized in children. In contrast, neurobehavioral outcomes associated with fish are not well studied in adults.

OBJECTIVE

This study of avid seafood consumers on Long Island (NY, USA) sought to define associations between mercury, seafood consumption, omega-3 fatty acids and neurobehavioral outcomes.

METHODS

A computer-based test system was used to assess neurobehavioral function. Blood total Hg (Hg) and omega-3 index were measured in 199 adult avid seafood eaters, who also completed the neurobehavioral assessment and an extensive food and fish frequency and demographic questionnaire.

RESULTS

For most of the outcomes considered, neither Hg nor omega-3 index was associated with neurobehavioral outcomes after adjustment for key confounding variables. Fish consumption, however, was associated with decreased odds of both self-reported fatigue (OR 0.85; 95 % CI 0.72, 1.01) and a constellation of neurologic symptoms (OR 0.79; 95 % CI 0.66, 0.96).

CONCLUSIONS

Results from our study provide little evidence that omega-3 fatty acids or Hg is associated with cognitive function in adult avid seafood consumers. Larger studies are needed to confirm our finding of associations between fish consumption and decreased self-reported fatigue and neurologic impairment.

Prenatal exposure to methyl mercury from fish consumption and polyunsaturated fatty acids: associations with child development at 20 mo of age in an observational study in the Republic of Seychelles

BACKGROUND

Fish is a rich source of n-3 polyunsaturated fatty acids (PUFAs) but also contains the neurotoxicant methyl mercury (MeHg). PUFAs may modify the relation between prenatal MeHg exposure and child development either directly by enhancing neurodevelopment or indirectly through the inflammatory milieu.

OBJECTIVE

The objective was to investigate the associations of prenatal MeHg exposure and maternal PUFA status with child development at 20 mo of age.

DESIGN

The Seychelles Child Development Study Nutrition Cohort 2 is an observational study in the Republic of Seychelles, a high-fish-eating population. Mothers were enrolled during pregnancy and their children evaluated at 20 mo of age by using the Bayley Scales of Infant Development II (BSID-II), the MacArthur Bates Communicative Development Inventories (CDI), and the Infant Behavior Questionnaire-Revised. There were 1265 mother-child pairs with complete data.

RESULTS

Prenatal MeHg exposure had no direct associations with neurodevelopmental outcomes. Significant interactions were found between MeHg and PUFAs on the Psychomotor Developmental Index (PDI) of the BSID-II. Increasing MeHg was associated with lower PDI but only in children of mothers with higher n-6/n-3. Among mothers with higher n-3 PUFAs, increasing MeHg was associated with improved PDI. Higher maternal docosahexaenoic acid (DHA) was associated with improved CDI total gestures (language development) but was significantly adversely associated with the Mental Development Index (MDI), both with and without MeHg adjustment. Higher n-6:n-3 ratios were associated with poorer scores on all 3 CDI outcomes.

CONCLUSIONS

We found no overall adverse association between prenatal MeHg exposure and neurodevelopmental outcomes. However, maternal PUFA status as a putative marker of the inflammatory milieu appeared to modify the associations of prenatal MeHg exposure with the PDI. Increasing DHA status was positively associated with language development yet negatively associated with the MDI. These findings may indicate the existence of an optimal DHA balance with respect to arachidonic acid for different aspects of neurodevelopment.

Assessment of dietary fish consumption in pregnancy: comparing one-, four- and thirty-six-item questionnaires

OBJECTIVE

Fish consumption influences a number of health outcomes. Few studies have directly compared dietary assessment methods to determine the best approach to estimating intakes of fish and its component nutrients, including DHA, and toxicants, including methylmercury. Our objective was to compare three methods of assessing fish intake.

DESIGN

We assessed 30 d fish intake using three approaches: (i) a single question on total fish consumption; (ii) a brief comprehensive FFQ that included four questions about fish; and (iii) a focused FFQ with thirty-six questions about different finfish and shellfish.

SETTING

Obstetrics practices in Boston, MA, USA.

SUBJECTS

Fifty-nine pregnant women who consumed ≤2 monthly fish servings.

RESULTS

Estimated intakes of fish, DHA and Hg were lowest with the one-question screener and highest with the thirty-six-item fish questionnaire. Estimated intake of DHA with the thirty-six-item questionnaire was 4·4-fold higher (97 v. 22 mg/d), and intake of Hg was 3·8-fold higher (1·6 v. 0·42 μg/d), compared with the one-question screener. Plasma DHA concentration was correlated with fish intake assessed with the one-question screener (Spearman r = 0·27, P = 0·04), but not with the four-item FFQ (r = 0·08, P = 0·54) or the thirty-six-item fish questionnaire (r = 0·01, P = 0·93). In contrast, blood and hair Hg concentrations were similarly correlated with fish and Hg intakes regardless of the assessment method (r = 0·35 to 0·52).

CONCLUSIONS

A longer questionnaire provides no advantage over shorter questionnaires in ranking intakes of fish, DHA and Hg compared with biomarkers, but estimates of absolute intakes can vary by as much as fourfold across methods.

Prenatal and neonatal peripheral blood mercury levels and autism spectrum disorders

BACKGROUND

Prenatal and early-life exposures to mercury have been hypothesized to be associated with increased risk of autism spectrum disorders (ASDs).

OBJECTIVES

This study investigated the association between ASDs and levels of total mercury measured in maternal serum from mid-pregnancy and infant blood shortly after birth.

METHODS

The study sample was drawn from the Early Markers for Autism (EMA) Study. Three groups of children who were born in Orange County, CA in 2000-2001 were identified: children with ASD (n=84), children with intellectual disability or developmental delay (DD) (n=49), and general population controls (GP) (n=159). Maternal serum specimens and newborn bloodspots were retrieved from the California Department of Public Health prenatal and newborn screening specimen archives. Blood mercury levels were measured in maternal serum samples using mass spectrometer and in infant bloodspots with a 213 nm laser.

RESULTS

Maternal serum and infant blood mercury levels were significantly correlated among all study groups (all correlations >0.38, p<0.01). Adjusted logistic regression models showed no significant associations between ASD and log transformed mercury levels in maternal serum samples (ASD vs. GP: OR [95% CI]=0.96 [0.49-1.90]; ASD vs. DD: OR [95% CI]=2.56 [0.89-7.39]). Results for mercury levels in newborn blood samples were similar (ASD vs. GP: OR [95% CI]=1.18 [0.71-1.95]; ASD vs. DD: OR [95% CI]=1.96 [0.75-5.14]).

CONCLUSIONS

Results indicate that levels of total mercury in serum collected from mothers during mid-pregnancy and from newborn bloodspots were not significantly associated with risk of ASD, though additional studies with greater sample size and covariate measurement are needed.

Meeting the fetal requirement for polyunsaturated fatty acids in pregnancy

PURPOSE OF REVIEW

The aim of this review is to summarize recent evidence on the importance of individual long chain polyunsaturated fatty acid (LCPUFA) to the developing fetus and the maternal dietary requirement for these.

RECENT FINDINGS

Large-scale randomized controlled trials and innovative genetic and stable isotope studies are providing new insights in this field.

SUMMARY

Large randomized controlled trials of LCPUFA supplementation in pregnancy suggest that higher n-3 LCPUFA intake reduces the risk of preterm birth and increases the length of gestation, with secondary effects on birth weight. There is little evidence of an effect on postnatal visual function and cognition, but interpretation is complicated by maternal metabolic adaptations and adipose tissue status in the newborn. The links between polymorphisms in the FADS genes and tissue fatty acid composition suggest that LCPUFA synthesis influences overall availability. Stable isotope studies have also demonstrated the capacity for LCPUFA synthesis in pregnancy, the fact that n-6 synthesis is greater than n-3, metabolic channeling of individual fatty acids to different fates, and selective placental transfer. Studies linking FADS genotype to cognition imply that n-3 LCPUFA synthesis could have an effect on infant cognition, but more large-scale genetic studies are needed.

High consumption of farmed salmon does not disrupt the steady state of persistent organic pollutants (POP) in human plasma and adipose tissue

The aims of this study were to (1) determine any changes in the levels of persistent organic pollutants (POP) and mercury (Hg) in human plasma and adipose tissue and (2) examine associations between plasma levels of pollutants and dietary fat intake. Outpatients with different metabolic disorders (n = 42) consumed 380 g of farmed Atlantic salmon fillets or 60 g of salmon oil per week in two study periods of 15 wk each, and were compared with a control group (n = 14). Concentrations of POP and Hg were measured in salmon fillets, salmon oil capsules, plasma and abdominal fat biopsies from patients before and after intervention. Mean concentrations of hexachlorobenzene (HCB), p,p'-DDE, sum of indicator polychlorinated biphenyls (PCB) (id-PCB), and sum polybrominated diphenyl ethers (PBDE) in abdominal fat at intervention start were 21, 191, 267, and 4.2 ng/g lipid weight. After 15 or 30 wk of salmon consumption no significant changes in concentrations of POP and Hg in samples of human plasma and abdominal fat were observed, indicating that steady-state levels of these pollutants were not markedly affected. The lack of significant changes may partly be attributed to a limited number of samples, large interindividual variation in POP levels, and a large age span (20-70 yr). After adjusting for age, significant associations were found between different plasma long-chain fatty acid concentrations, including n-3 and n-6 fatty acids and oleic acid, and some of the POP. The results indicate that the latter have different food products as their main sources of human exposure.

Mercury as a global pollutant: sources, pathways, and effects

Mercury (Hg) is a global pollutant that affects human and ecosystem health. We synthesize understanding of sources, atmosphere-land-ocean Hg dynamics and health effects, and consider the implications of Hg-control policies. Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, resulting in increases in Hg reservoirs and subsequent secondary Hg emissions that facilitate its global distribution. The ultimate fate of emitted Hg is primarily recalcitrant soil pools and deep ocean waters and sediments. Transfers of Hg emissions to largely unavailable reservoirs occur over the time scale of centuries, and are primarily mediated through atmospheric exchanges of wet/dry deposition and evasion from vegetation, soil organic matter and ocean surfaces. A key link between inorganic Hg inputs and exposure of humans and wildlife is the net production of methylmercury, which occurs mainly in reducing zones in freshwater, terrestrial, and coastal environments, and the subsurface ocean. Elevated human exposure to methylmercury primarily results from consumption of estuarine and marine fish. Developing fetuses are most at risk from this neurotoxin but health effects of highly exposed populations and wildlife are also a concern. Integration of Hg science with national and international policy efforts is needed to target efforts and evaluate efficacy.

Which fish should I eat? Perspectives influencing fish consumption choices

BACKGROUND

Diverse perspectives have influenced fish consumption choices.

OBJECTIVES

We summarized the issue of fish consumption choice from toxicological, nutritional, ecological, and economic points of view; identified areas of overlap and disagreement among these viewpoints; and reviewed effects of previous fish consumption advisories.

METHODS

We reviewed published scientific literature, public health guidelines, and advisories related to fish consumption, focusing on advisories targeted at U.S. populations. However, our conclusions apply to groups having similar fish consumption patterns.

DISCUSSION

There are many possible combinations of matters related to fish consumption, but few, if any, fish consumption patterns optimize all domains. Fish provides a rich source of protein and other nutrients, but because of contamination by methylmercury and other toxicants, higher fish intake often leads to greater toxicant exposure. Furthermore, stocks of wild fish are not adequate to meet the nutrient demands of the growing world population, and fish consumption choices also have a broad economic impact on the fishing industry. Most guidance does not account for ecological and economic impacts of different fish consumption choices.

CONCLUSION

Despite the relative lack of information integrating the health, ecological, and economic impacts of different fish choices, clear and simple guidance is necessary to effect desired changes. Thus, more comprehensive advice can be developed to describe the multiple impacts of fish consumption. In addition, policy and fishery management interventions will be necessary to ensure long-term availability of fish as an important source of human nutrition.

A strategy for comparing the contributions of environmental chemicals and other risk factors to neurodevelopment of children

BACKGROUND

The impact of environmental chemicals on children's neurodevelopment is sometimes dismissed as unimportant because the magnitude of the impairments are considered to be clinically insignificant. Such a judgment reflects a failure to distinguish between individual and population risk. The population impact of a risk factor depends on both its effect size and its distribution (or incidence/prevalence).

OBJECTIVE

The objective was to develop a strategy for taking into account the distribution (or incidence/prevalence) of a risk factor, as well as its effect size, in order to estimate its population impact on neurodevelopment of children.

METHODS

The total numbers of Full-Scale IQ points lost among U.S. children 0-5 years of age were estimated for chemicals (methylmercury, organophosphate pesticides, lead) and a variety of medical conditions and events (e.g., preterm birth, traumatic brain injury, brain tumors, congenital heart disease).

DISCUSSION

Although the data required for the analysis were available for only three environmental chemicals (methylmercury, organophosphate pesticides, lead), the results suggest that their contributions to neurodevelopmental morbidity are substantial, exceeding those of many nonchemical risk factors.

CONCLUSION

A method for comparing the relative contributions of different risk factors provides a rational basis for establishing priorities for reducing neurodevelopmental morbidity in children.

In vitro effect of lead, silver, tin, mercury, indium and bismuth on human sperm creatine kinase activity: a presumable mechanism for men infertility

BACKGROUND

The aim of the present study was to investigate the in vitro effects of mercury (Hg+2), lead (Pb+2), silver (Ag+2), tin (Sn+2), bismuth (Bi+3) and indium (In+3) ions on sperm creatine kinase.

METHODS

creatine kinase was isolated from human sperm homogenates after chromatography on a DEAE cellulose column.

RESULTS

At 60 mug ml-1 metal concentration, 70% of the creatine kinase activity was inhibited by Hg+2, while at the same concentration, Pb+2, Ag+2, Sn+2, Bi+3 and In+3 caused 68%, 66.5%, 65.7%, 64.7% and 62.7% inhibition, respectively. All six metal ions displayed a competitive type of inhibition mechanism for the isolated creatine kinase as analyzed by Lineweaver-Burk plot. Ki values of Hg+2, Pb+2, Ag+2, Sn+2, Bi+3 and In+3 were calculated and 8.34 mM, 5 mM, 4.54 mM, 3.45 mM, 3.12 mM and 2.63 mM values were obtained, respectively.

CONCLUSION

All the studied metal ions, at levels of 60 mug ml-1, may reduce normal sperm metabolism by inhibition of sperm creatine kinase, which probably is an important cause of infertility in men. However, further investigations, as in vitro and in vivo, are needed to elucidate the exact mechanism of heavy metals on male reproductive functioning at the molecular level.