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Waters from the Amazon Basin have distinct physicochemical characteristics that can be optically classified as “black”, “clear” and “white”. We studied the distribution of total-Hg (THg) and methyl-Hg (MeHg) in these waters and respective suspended solids, sediment, phytoplankton, zooplankton, and benthic macroinvertebrates (BM) in the Madeira River Basin. Compared with the other types of water, the more acidic “black” kind had the highest THg and MeHg concentrations. The trend (black > clear > white) occurred for the concentrations of THg and MeHg in sediments and in the biotic compartment (plankton, macroinvertebrates). Organic Hg accounted for a small percentage (0.6–0.4%) of the THg in sediments but was highest in water (17–15%). For plankton and BM, the biota sediment accumulation factor (BSAFs) of MeHg (53–125) were greater than those of THg (4.5–15); however, the BSAF trend according to water type (black > clear > white) was only significant for MeHg. Sediment THg is correlated with all forms of Hg in biotic and abiotic matrices. The results indicate that water acidity in the Amazon is an important chemical characteristic in assessing Hg contamination of sediments and bioaccumulation in the aquatic food web. The differences in the BSAFs between THg and MeHg support the use of this factor for evaluating the bioaccumulation potential of sediment-bound Hg. The results add information critical to assessing environmental and health risks related to Hg methylation and potential fish-MeHg contamination, especially in tropical aquatic environments. [ABSTRACT FROM AUTHOR]

In the transitioning Amazon, we addressed birth environment (home vs hospital) and associated perinatal organic-Hg exposures: methylmercury (MeHg) from maternal fish consumption and ethylmercury (EtHg) from pediatric Thimerosal-containing vaccines (TCVs) taken systematically during hospital delivery. We studied 365 children in relation to linear growth at 60 months and neurodevelopment (milestone achievements, Bayley Scale of Infant Development/BSID at 24 months, and Stanford-Binet intelligence tests at 60 months). Mothers delivered in hospitals vs those gave birth at home had significantly (p<0.0001) lower hair-Hg (HHg) concentrations (12.2 vs 23.9μg/g respectively) and shorter length of breastfeeding (8.5 vs 9.7 months respectively). Home-born children had significantly (p<0.0001) higher HHg (7.1μg/g) than hospital-born children (4.6μg/g). Hospital-born children also had significantly earlier (p<0.0001) hepatitis B vaccine than home-born children (1.5 vs 24.1days respectively) and higher (p<0.0001) exposures to total TCV-EtHg (75.8 vs 49.3μg respectively). Neither anthropometric indices nor neurodevelopment (except for fluid reasoning) were directly affected by birth environment. The percentage of hospital-born children with BSID (MDI or PDI) scores <80 was not significantly different from those born at home. In spite of the differences in HHg and EtHg levels between hospital-born and home-born children, no impact on neurodevelopment was observed. [ABSTRACT FROM AUTHOR]

Background:Features of traditional living in the Amazon Basin (high fish consumption and long breastfeeding) are likely to expose children to Mercury (Hg). Aim:To study neurodevelopment in 690 children in relation to prolonged breastfeeding and mercury exposure. Subjects and methods:Three groups of breastfeeding children were formed: Group 1 (breastfed for 6 months), Group 2 (7–12 months) and Group 3 (extending up to 24 months). Neurodevelopment was assessed as age of walking, age of talking and the Bayley Scales of Infant Development–BSID. Mercury exposure was assessed from Thimerosal-containing vaccines and fish consumption from hair Hg (HHg). Results and conclusions:HHg increased in children and decreased in mothers at 24 months. Frequency of fish consumption was significantly correlated with maternal HHg at birth (Spearman’sr = 0.8583;p = 0.0001); likewise, there was a significant correlation between duration of breastfeeding and children’s HHg (Spearman’sr = 0.15;p = 0.0018). Extended breastfeeding did not influence the Mental Development Index–MDI or Psychomotor Development Index–PDI, but maternal education and HHg (marker of fish consumption) interacted positively and significantly with both. Frequency of maternal fish consumption and education had a positive association with BSID scores; it is speculated that maternal education and nutrients in fish have an opposing effect on Hg exposure. [ABSTRACT FROM AUTHOR]

The central nervous system is a critical target for Hg toxicity in all living organisms. Total Hg (THg) was determined in brain and muscle samples of 165 specimens of eight species of catfish ( Brachyplatystoma filamentosum; Brachyplatystoma platynemum ; Brachyplatystoma rousseauxii ; Brachyplatystoma vaillantii ; Phractocephalus hemiliopterus ; Pseudoplatystoma punctifer; Pseudoplatystoma tigrinum ; Zungaro zungaro ) from the Madeira River, Brazilian Amazon. Despite the narrow range of Fishbase trophic level (4.2–4.6) the median THg concentrations ranged from 0.39 to 1.99 mg/kg and from 0.03 to 0.29 mg/kg respectively in muscle and brain from the studied species. Overall, the median concentration for all samples analyzed was 0.93 mg/kg and 0.16 mg/kg respectively in muscle and brain; most samples (76%) showed muscle Hg concentrations >0.5 mg/kg. There were statistically significant THg differences between sex (female>males). The correlation between THg concentrations in muscle and brain was statistically significant ( r =0.9170; p <0.0001). In the studied specimens, fish total length was significantly correlated with muscle ( r =0.3163; p =0.0001) and brain ( r =0.3039; p =0.0003) THg; however, fish age was negatively and significantly correlated ( r =−0.2991; p =0.0012) with THg in muscle but not with THg in brain ( r =−0.0190; p =0.8492). Amazonian catfish accumulate high levels of Hg in muscle and brain; however, brain-THg concentrations can be predicted from muscle-THg. Muscle-Hg in catfish can be a tool to detect brain-Hg concentrations associated with environmental Hg. [ABSTRACT FROM AUTHOR]

Abstract: The variance of variables associated with neurodevelopment at 180 days, pre-natal variables (Hg in placenta, blood and hair) and post-natal Hg exposure (including Thimerosal-containing vaccines, TCV) were examined in 82 exclusively breastfed infants using principal component analysis (PCA). This multivariate method was applied to identify hierarchy and sets of interrelated variables. The PCA yielded a two-factor solution, explaining 92% of variance and summarizing most of the relevant information in the dataset matrix: the first component represented birth weight and vaccine (first doses of Hepatitis B and DTP) variability and explained 57% of variance; the second component represented a gradient of neurodevelopment (Gesell scores) and explained 35% of variance. The third component explained only 3% of the remaining 8% variance. Beside CNS priming by breastfeeding, infant development (birth weight) and time of immunization with TCV should be considered in epidemiological studies. PCA can classify sets of variables related to vaccination and neuromotor development schedules, clearly discriminating between earlier and later TCV exposures of exclusively breastfed infants. In conclusion, the incommensurable concept of the chance of toxic risk caused by TCV-EtHg exposure against the proven benefit of immunization is in no way disputed here. However, infant neurodevelopmental (ND) disorders linked to Thimerosal-Hg stands in need of proof, but PCA points to the possibility of identifying exposure risk variables associated with ND schedules. [Copyright &y& Elsevier]

Few studies have addressed co-occurring methylmercury (MeHg) from maternal origin and ethylmercury (EtHg) from Thimerosal-containing vaccines (TCVs) during infant's neurodevelopment. We studied children ( n =1139) from the Western Amazon based on combined (low, intermediate, and high) exposure to chronic MeHg from fish consumption and acute TCV- EtHg. Neurodevelopment outcomes were age of walking and age of talking, and the Bayley Scale of Infant Development (BSID). The Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI) were measured at six and 24 months of age. Median hair-Hg (HHg) at birth was 6.4 µg g −1 in mothers, and 1.94 µg g −1 in newborns; total (pregnancy and infancy) EtHg exposure ranged from 0 to 187.5 µg. The combined (MeHg+EtHg) exposure showed significant differences for MDI but not for PDI; however, there was a significant decrease in both MDI and PDI scores at 24 months. The increase in BSID delays (scores <80) between six and 24 months was not discernible with regards to EtHg or MeHg exposure. We found a statistically significant increase in neurodevelopmental (BSID) delays related to the combined exposure to Hg (MeHg>EtHg). Neurodevelopment delays due to low-doses of organic mercury (albeit undiscernible) are not predictable but can be avoided by choosing low-Hg fish and providing Thimerosal-free vaccines. [ABSTRACT FROM AUTHOR]