Fish consumption (hair mercury) and nutritional status of Amazonian Amer-Indian children

The legacy of artisanal gold mining and its impact on fish health from Tapajós Amazonian region: A multi-biomarker approach

Tapajós Region, is an area with intense historical artisanal and small-scale gold mining. Therefore, the core objective of this study was to evaluate the environmental status of different rivers located in this region, using biomarker endpoints in Serrasalmus rhombeus as a tool. Fish and sediment were collected from two rivers, Tropas and Crepori, affluent of Tapajós River, located inside a Federal Protection Area and in a Reference site. Mercury concentration in sediment and fish were traced, and biomarkers in gills and liver were analyzed. Results showed a clear difference between these two rivers compared to the Reference site. Fish tissues presented biomarker responses according to the site of collection. Catalase (CAT) activity was statistically higher in fish gills from Crepori, confirming the capacity of mercury interference with redox equilibrium. High levels of lipid peroxidation were also noted to contribute greatly in incidence of morphological changes in the liver and gills, suggesting that mercury bioaccumulation during continuous exposure promote biological responses in a cumulative manner, from molecules to tissues. This study also indicates adaptation in fish defense mechanisms given the conditions in the Tropas River, as well as a variation in biomarker responses to that of the Crepori river. In summary, Tapajós affluents presented high mercury levels in fish tissues leading to biomarker responses, demonstrating a hazardous signal of a long history of mercury pollution.

Economic Impacts on Human Health Resulting from the Use of Mercury in the Illegal Gold Mining in the Brazilian Amazon: A Methodological Assessment

Artisanal small-scale gold mining (ASGM) in the Amazon results in the dumping of tons of mercury into the environment annually. Despite consensus on the impacts of mercury on human health, there are still unknowns regarding: (i) the extent to which mercury from ASGM can be dispersed in the environment until it becomes toxic to humans; and (ii) the economic value of losses caused by contamination becomes evident. The main objective of this study is to propose a methodology to evaluate the impacts of ASGM on human health in different contexts in the Brazilian Amazon. We connect several points in the literature based on hypotheses regarding mercury dispersion in water, its transformation into methylmercury, and absorption by fish and humans. This methodology can be used as a tool to estimate the extent of environmental damage caused by artisanal gold mining, the severity of damage to the health of individuals contaminated by mercury and, consequently, can contribute to the application of fines to environmental violators. The consequences of contamination are evaluated by dose-response functions relating to mercury concentrations in hair and the development of the following health outcomes: (i) mild mental retardation, (ii) acute myocardial infarction, and (iii) hypertension. From disability-adjusted life years and statistical life value, we found that the economic losses range from 100,000 to 400,000 USD per kilogram of gold extracted. A case study of the Yanomami indigenous land shows that the impacts of mercury from illegal gold mining in 2020 totaled 69 million USD, which could be used by local authorities to compensate the Yanomami people.

Mercury Exposure in Munduruku Indigenous Communities from Brazilian Amazon: Methodological Background and an Overview of the Principal Results

The Amazonian indigenous peoples depend on natural resources to live, but human activities' growing impacts threaten their health and livelihoods. Our objectives were to present the principal results of an integrated and multidisciplinary analysis of the health parameters and assess the mercury (Hg) exposure levels in indigenous populations in the Brazilian Amazon. We carried out a cross-sectional study based on a census of three Munduruku indigenous villages (Sawré Muybu, Poxo Muybu, and Sawré Aboy), located in the Sawré Muybu Indigenous Land, between 29 October and 9 November 2019. The investigation included: (i) sociodemographic characterization of the participants; (ii) health assessment; (iii) genetic polymorphism analysis; (iv) hair mercury determination; and (v) fish mercury determination. We used the logistic regression model with conditional Prevalence Ratio (PR), with the respective 95% confidence intervals (CI95%) to explore factors associated with mercury exposure levels ≥6.0 µg/g. A total of 200 participants were interviewed. Mercury levels (197 hair samples) ranged from 1.4 to 23.9 μg/g, with significant differences between the villages (Kruskal-Wallis test: 19.9; p-value < 0.001). On average, the general prevalence of Hg exposure ≥ 6.0 µg/g was 57.9%. For participants ≥12 years old, the Hg exposure ≥6.0 µg/g showed associated with no regular income (PR: 1.3; CI95%: 1.0-1.8), high blood pressure (PR: 1.6; CI95%: 1.3-2.1) and was more prominent in Sawré Aboy village (PR: 1.8; CI95%: 1.3-2.3). For women of childbearing age, the Hg exposure ≥6.0 µg/g was associated with high blood pressure (PR: 1.9; CI95%: 1.2-2.3), with pregnancy (PR: 1.5; CI95%: 1.0-2.1) and was more prominent among residents in Poxo Muybu (PR: 1.9; CI95%: 1.0-3.4) and Sawré Aboy (PR: 2.5; CI95%: 1.4-4.4) villages. Our findings suggest that chronic mercury exposure causes harmful effects to the studied indigenous communities, especially considering vulnerable groups of the population, such as women of childbearing age. Lastly, we propose to stop the illegal mining in these areas and develop a risk management plan that aims to ensure the health, livelihoods, and human rights of the indigenous people from Amazon Basin.

Health Risk Assessment of Mercury Exposure from Fish Consumption in Munduruku Indigenous Communities in the Brazilian Amazon

Fish serves as the principal source of animal protein for the indigenous people of the Amazon, ensuring their food and nutritional security. However, gold mining causes mercury (Hg) contamination in fish, and consequently increases health risks associated with fish consumption. The aim of this study was to assess the health risk attributed to the consumption of mercury-contaminated fish by Munduruku indigenous communities in the Middle-Tapajós Region. Different fish species were collected in the Sawré Muybu Indigenous Land to determine mercury levels. The health risk assessment was carried out according to the World Health Organization (WHO 2008) methodology and different scenarios were built for counterfactual analysis. Eighty-eight fish specimens from 17 species and four trophic levels were analyzed. Estimates of Hg ingestion indicated that the methylmercury daily intake exceeds the U.S. EPA (United States Environmental Protection Agency) (2000) reference dose from 3 to 25-fold, and up to 11 times the FAO (Food and Agriculture Organization)/WHO (2003) dose recommendation. In all situations analyzed, the risk ratio estimates were above 1.0, meaning that the investigated Munduruku communities are at serious risk of harm as a result of ingestion of mercury-contaminated fish. These results indicate that, at present, fish consumption is not safe for this Munduruku population. This hazardous situation threatens the survival of this indigenous population, their food security, and their culture.

Intestinal Parasites, Anemia and Nutritional Status in Young Children from Transitioning Western Amazon

Young children are particularly vulnerable to the chronic sequelae of anemia, including poor nutritional status. The aim of this study was to assess intestinal parasitic-infections and nutritional status (anemia and linear growth) in preschool children living in contemporary Amazonian communities. A cross-sectional study measured children’s intestinal parasites and hair-Hg (HHg)—biomarkers of fish consumption, hemoglobin levels, and growth (anthropometric Z-scores). Children came from traditional-living families (Itapuã), and tin-mining settlements (Bom Futuro) representing current transitioning populations. It covered 937 pre-school children (from 1 to 59 months of age) from traditional (247) and immigrant tin-mining families (688). There was a high prevalence of intestinal polyparasitic-infection in children from both communities, but mild anemia (hemoglobin concentrations) and moderate (chronic) malnutrition were more frequent in children from traditional families than in children from tin-mining settlers. Children from traditional families ate significantly more fish (HHg mean of 4.3 µg/g) than children from tin-mining families (HHg mean of 2.3 µg/g). Among traditional villagers, children showed a significant correlation (r = 0.2318; p = 0.0005) between hemoglobin concentrations and HHg concentrations. High rates of parasitic infection underlie the poverty and attendant health issues of young children in the Brazilian Amazon. The intestinal parasite burden affecting poor Amazonian children resulting from unsafe water, lack of sanitation and poor hygiene is the most urgent environmental health issue.

Influence of Maternal Fish Intake on the Anthropometric Indices of Children in the Western Amazon

We studied trends in fish intake among pregnant women living in the Madeira River Basin in Rondônia State, Brazil, to investigate the influence of maternal fish intake on anthropometric indices of children followed up to 5 years. Maternal fish intake was assessed using hair mercury concentrations of mothers and children at delivery and 6, 24, and 59 months. Data analysis was performed using a linear mixed-effect model. Mothers were predominantly young, had low incomes and limited schooling, and breastfed for >6 months. Only 1.9% of children had low birth weight. Anthropometric indices in approximately 80% of the study population showed Z-score values ranging from ≥-2 to ≤1. The influence of maternal fish intake on anthropometric indices, including height-to-age (H/A), weight-to-age (W/A), and weight-to-height (W/H) were not statistically significant after model adjustments. However, higher income and larger birth weight had a positive influence on H/A and W/A, whereas W/H gain was favored by higher maternal educational status and breastfeeding duration. Other variables (hemoglobin concentration and maternal age) had a positive significant influence on anthropometric indices. Maternal fish intake (or its attendant MeHg exposure) did not affect children growth. Nevertheless, it is advisable to avoid mercury-contaminated fish during pregnancy and childhood.

Mercury and selenium in fishes from the Tapajós River in the Brazilian Amazon: An evaluation of human exposure

This work aimed to evaluate associated risks of fish consumption to human health, concerning mercury (Hg) and selenium (Se) concentrations in fish species largely consumed in the Tapajós River basin in the Brazilian Amazon. Total mercury (THg), methylmercury (MeHg) and Se concentrations were measured in 129 fish specimens from four sites of the Tapajós River basin. Estimated daily intake (EDI) of Hg and Se were reported regarding fish consumption. EDI were compared with the reference value of provisional tolerable daily intake proposed by the World Health Organization (WHO). Se:Hg ratios and selenium health benefit values (Se HBVs) seem to offer a more comprehensive fish safety model. THg concentrations in fishes ranged from 0.03 to 1.51 μg g^-1 of wet weight (w.w.) and MeHg concentrations ranged from 0.02 to 1.44 μg g^-1 (w.w.). 80% of the samples were below the value of Hg recommended by the WHO for human consumption (0.5 μg g^-1 w.w.). However, Hg EDI exceeded the dose suggested by the United States Environmental Protection Agency (0.1 μg kg^-1 day^-1), due to the large level of fish consumption in that area. Se concentrations in fishes ranged from 0.02 to 0.44 μg g^-1 w.w. An inverse pattern was observed between Hg and Se concentrations in the trophic chain (highest levels of Se in the lowest trophic levels). The molar ratio Se:Hg and Se HBVs were higher in iliophagous and herbivorous fishes, which is noteworthy to reduce toxic effects of Hg contamination. For planktivores, the content of Se and Hg was almost equimolar. Carnivorous fishes - with the exception of Hemisorubim platyrhynchos and Pseudoplatystoma fasciatum -, showed Se:Hg ratios <1. Thus, they do not act as a favorable source of Se in the diet. Therefore, reduced intake of carnivorous fishes with preferential consumption of iliophages, herbivores and, to some extent, even planktivores should be promoted as part of a healthier diet.

Human Mercury Exposure in Yanomami Indigenous Villages from the Brazilian Amazon

In the Brazilian Amazon, where the majority of Yanomami villages are settled, mercury (Hg) exposure due to artisanal small-scale gold mining (ASGM) has been reported since the 1980s. This study assessed mercury exposure in the Yanomami reserve and whether the level of contamination was related to the ASGM geographical location. It was conducted using a cross-sectional study of 19 villages. Direct interviews were performed and hair samples were used as a bioindicator of Hg exposure. The Prevalence-Ratio (PR) was estimated as an indicator of association between ASGM geographical locations and human exposure to mercury. Mercury levels (239 hair samples) ranged between 0.4 and 22.1 μg·g-1 and presented substantial differences amongst the villages. In the Waikas-Aracaça region, where current ASGM was reported, we observed the highest Hg concentrations (median = 15.5 μg·g-1). Almost all participants presented with hair-Hg levels >6 μg·g-1 (prevalence = 92.3%). In the Paapiu region, we observed the lowest concentrations (median = 3.2 μg·g-1; prevalence = 6.7%). Our findings showed that the Waikas Ye'kuana and Waikas Aracaca villages presented with 4.4 (PR = 4.4; Confidence Interval (CI) 95% = 2.2⁻9.0) and 14.0 (PR = 14.0; CI 95% = 7.9⁻24.9) times higher prevalence of hair-Hg concentration, respectively, compared with Paapiu. Considering seasonal variation of Hg-exposure, the lowest concentrations were observed during the wet season (June⁻September) and the highest in the dry season (December⁻April). Our study suggests that there is an association between mercury exposure and ASGM geographical locations.

Mercury Exposure in Children of the Wanshan Mercury Mining Area, Guizhou, China

To evaluate the mercury (Hg) exposure level of children located in a Hg mining area, total Hg concentrations and speciation were determined in hair and urine samples of children in the Wanshan Hg mining area, Guizhou Province, China. Rice samples consumed by these same children were also collected for total mercury (THg) and methyl-mercury (MeHg) analysis. The geometric mean concentrations of THg and MeHg in the hair samples were 1.4 (range 0.50-6.0) μg/g and 1.1 (range 0.35-4.2) μg/g, respectively, while the geometric mean concentration of urine Hg (UHg) was 1.4 (range 0.09-26) μg/g Creatinine (Cr). The average of the probable daily intake (PDI) of MeHg via rice consumption was 0.052 (0.0033-0.39) µg/kg/day, which significantly correlated with the hair MeHg concentrations (r = 0.55, p < 0.01), indicating that ingestion of rice is the main pathway of MeHg exposure for children in this area. Furthermore, 18% (26/141) of the PDIs of MeHg exceeded the USEPA Reference Dose (RfD) of 0.10 µg/kg/day, indicating that children in this area are at a high MeHg exposure level. This paper for the first time evaluates the co-exposure levels of IHg and MeHg of children living in Wanshan mining area, and revealed the difference in exposure patterns between children and adults in this area.

Mercury levels and human health in the Amazon Basin

CONTEXT

Environmental mercury in the Amazon mostly originates from geochemical sources with some from artisanal gold mining (AGM). Geochemical-originated methylmercury (MeHg) reaches the aquatic food chain, ending up in fish. Inorganic Hg used in AGM is responsible for localised environmental contamination and occupational exposure of adults. In addition to this, iatrogenic ethylmercury (EtHg) derived from Thimerosal-containing vaccines (TCVs) exposes immunised infants.

OBJECTIVE

To understand Hg exposure in the Amazon in relation to environmental fish-MeHg exposure, occupational AGM activities and low-doses of TCV-EtHg.

METHODS

Medline and Thomson-Reuter Web of Science were searched to retrieve and select papers addressing Hg exposure and human health.

RESULTS AND CONCLUSION

Environmental-Hg studies addressed health effects associated with birth weight, infant linear growth and neurodevelopment, while, in adults, environmental and occupational studies addressed immune and neurological issues. No widespread clinical toxicity was reported due to fish-MeHg. However, mixed results associated with Hg exposure can be found. Reducing children's exposure to EtHg is possible using Thimerosal-free vaccines, but it is difficult to interfere with fish consumption without consequences to riverine subsistence populations. Policies to diminish Hg exposure should focus on controlling and/or curbing widespread use of Hg (in gold amalgamation) and promotion of Thimerosal-free vaccines for pregnant women and young children.

Mercury in fish of the Madeira river (temporal and spatial assessment), Brazilian Amazon

The Madeira River is the largest tributary of the Amazon River Basin and one of the most impacted by artisanal gold-mining activities, deforestation for agricultural projects, and recent hydroelectric reservoirs. Total Hg (and methylmercury-MeHg) concentrations was determined in 3182 fish samples of 84 species from different trophic levels as a function of standard size. Species at the top of the trophic level (Piscivorous, Carnivorous) showed the highest mean total Hg concentrations (51-1242 µg/kg), Planctivorous and Omnivorous species showed intermediate total Hg concentrations (26-494 µg/kg), while Detritivorous and Herbivorous species showed the lowest range of mean total Hg concentrations (9-275 µg/kg). Significant correlations between fish size (standard length) and total Hg concentrations were seen for Planctivorous (r=0.474, p=0.0001), Piscivorous (r=0.459, p=0.0001), Detritivorous (r=0.227, p=0.0001), Carnivorous (r=0.212, p=0.0001), and Herbivorous (r=0.156, p=0.01), but not for the Omnivorous species (r=-0.064, p=0.0685). Moreover, fish trophic levels influenced the ratio of MeHg to total Hg (ranged from 70% to 92%). When adjusted for standard body length, significant increases in Hg concentrations in the last 10 years were species specific. Spatial differences, albeit significant for some species, were not consistent with time trends for environmental contamination from past alluvial gold mining activities. Fish-Hg bioaccumulation is species specific but fish feeding strategies are the predominant influence in the fish-Hg bioaccumulation pattern.

Brazilian indigenous children: Review of studies about nutritional status

Objective: To systematize studies on the anthropometric nutritional status of Brazilian indigenous children in order to examine the ability to address the totality of biological, anthropological, and ecological aspects, as well as to characterize the main analytical results of the determinants of nutritional status of Brazilian indigenous children. Methods: MedLine and Lilacs were searched using the intersection of "South American Indians" and "nutritional status" descriptors (the search in MedLine also included the descriptor "Brazil"). Results: Overall, 65 studies were identified, and 23 were considered relevant to this study. The systematization of these studies highlights the concentration of studies in the midwestern and northern regions of Brazil, as well as the lack of cultural, biochemical, and food consumption approaches. Regarding nutritional status, we found: 1) greater vulnerability of younger children, especially in relation to stunting; 2) absence of differences in nutritional status according to sex; 3) socioeconomic determination of nutritional status; 4) differences in nutritional status between children from different villages. Conclusion: The nutritional status of Brazilian indigenous children is associated with age, socioeconomic status, and ethnic characteristics. Efforts are needed to understand the ethnic and cultural influence on nutritional status and on its causal network, as well as of various factors minimally discussed.

Role of methylmercury exposure (from fish consumption) on growth and neurodevelopment of children under 5 years of age living in a transitioning (tin-mining) area of the western Amazon, Brazil

Human occupation of the Amazon region has recently increased, bringing deforestation for agriculture and open-cast mining, activities that cause environmental degradation and pollution. Families of new settlers in mining areas might have a diet less dependent on abundant fish and their children might also be impacted by exposures to mining environments. Therefore, there is compounded interest in assessing young children's nutritional status and neurobehavioral development with regard to family fish consumption. Anthropometric (z-scores, WHO standards) and neurologic [Gesell developmental scores (GDS)] development in 688 preschool children (1-59 months of age) was studied. Overall, the prevalence of malnutrition [i.e., moderate stunting (≤2 H/A-Z), underweight (≤2 W/A-Z), and wasting (≤2 W/H-Z) were respectively 0.3% (n = 2), 1.6% (n = 11), and 2.5% (n = 17). Children's mean hair Hg (HHg) concentration was 2.56 μg/g (SD = 1.67); only 14% of children had HHg concentrations lower than 1 μg/g and 1.7% had ≥5 μg/g. The biomarker of fish consumption was weakly but positively correlated with GDS (Spearman r = 0.080; p = 0.035). In the bivariate model, attained W/H-Z scores were not significantly correlated with GDS. A moderate level of GDS deficits (70-84%) was seen in 20% of children. There was significant correlation between family fish consumption and children's hair Hg (HHg) (Spearman r = 0.1756; p < 0.0001) but no significant correlation between children's HHg and W/H-Z scores. However, the multivariate model showed that breastfeeding, a fish consumption biomarker (HHg), maternal education, and child's age were statistically significant associated with specific domains (language and personal-social) of the Gesell scale. In this mining environment, family fish-eating did not affect children's linear growth, but it showed a positive influence (along with maternal variables) on neurodevelopment. Health hazards attendant on a high prevalence of moderate neurodevelopment delays coexisting with exposure to multiple neurotoxic substances merits further investigation in poor environmental settings of tin-mining areas.

Hydroelectric reservoir inundation (Rio Madeira Basin, Amazon) and changes in traditional lifestyle: impact on growth and neurodevelopment of pre-school children

Objective

To assess the dependence on fish consumption of families and its impact on nutritional status and neurodevelopment of pre-school children.

Design

Cross-sectional study that measured children’s hair mercury (HHg) as an indicator of family fish consumption, growth (anthropometricZ-scores, WHO standards) and neurological (Gesell developmental scores (GDS)) development.

Setting

Traditional living conditions among families residing in the area adjacent to the Samuel Dam (Western Amazon) hydroelectric reservoir.

Subjects

Two hundred and forty-nine pre-school children (1–59 months of age) from families transitioning from the traditional Amazonian lifestyle.

Results

Family fish consumption was significantly correlated with children’s HHg concentration (Spearman’sr= 0·246,P< 0·0001); however, HHg had no significant association with growth (Z-scores). Overall, the prevalence of severe malnutrition, i.e. stunting (height-for-ageZ-score (HAZ) ≤ −3), underweight (weight-for-ageZ-score (WAZ) ≤ −3) and wasting (weight-for-heightZ-score (WHZ) ≤ −3) was 5·2 % (n13), 0 % and 0·8 % (n2), respectively. The prevalence of moderate stunting (HAZ ≥ −3 to ≤ −2), underweight (WAZ ≥ −3 to ≤ −2) and wasting (WHZ ≥ −3 to ≤ −2) was 8·8 % (n22), 2·4 % (n6) and 4·8 % (n12), respectively. Although 76 % of the children showed adequate GDS (>85), multiple regression analysis showed that fish consumption (as HHg) had no impact on GDS, but that some variables did interact significantly with specific domains (motor and language development).

Conclusions

The study showed that the families’ shift in fish consumption had no negative impact on the growth of young children and that ensuing methylmercury exposure has not been a noticeable neurodevelopmental hindrance.

Sequential hair mercury in mothers and children from a traditional riverine population of the Rio Tapajós, Amazonia: seasonal changes

Riverine populations of the Brazilian Amazon depend on fish for their principal source of protein, which changes in availability with seasonal fluctuations in the aquatic ecosystem. We report seasonal (high and low waters) and interannual changes in total mercury and methylmercury concentrations in hair of subsistence fish-eaters from a traditional riverine village on the banks of the Rio Tapajós in the Brazilian Amazonia. Retrospective exposure assessment was conducted from hair concentrations in segments representative of 2 years. A total of 32 mothers and their 51 children were studied. They reported high fish consumption (4-14 times a week). Ranges of total mercury and methylmercury concentrations in hair were 1.0-51.0 and 0.5-41.4microgg(-1), with means of 12.4 and 10.2microgg(-1), respectively. The relative mean value for methylmercury was 80%. There was a significant correlation between mothers and children for both total-Hg (r=0.4826; P=0.003) and methyl-Hg (r=0.5214; P=0.004). Mercury concentrations along hair strands of individuals showed significant variation coinciding with seasonal high and low waters. The changes in the aquatic environment impacted fish species availability, which is reflected in the total and MeHg concentrations in hair.

Mercury in the Tapajós River basin, Brazilian Amazon: a review

This paper presents a review about mercury contamination and human exposure in the Tapajós River basin (Brazil), one of the major tributaries of the Amazon impacted by traditional gold mining from the mid 1980s. The most recent review in this region was published more than ten years ago and since then many articles about environment and especially human populations have revealed new aspects of mercury toxicology. Additionally, new biomarkers of mercury exposure and toxicity have been studied in these populations. However, there are still many open, about both mercury's biogeochemical cycle and mercury health risks. Further environmental and human risk research directions are proposed.

Hair mercury levels in Amazonian populations: spatial distribution and trends

BACKGROUND

Mercury is present in the Amazonian aquatic environments from both natural and anthropogenic sources. As a consequence, many riverside populations are exposed to methylmercury, a highly toxic organic form of mercury, because of their intense fish consumption. Many studies have analysed this exposure from different approaches since the early nineties. This review aims to systematize the information in spatial distribution, comparing hair mercury levels by studied population and Amazonian river basin, looking for exposure trends.

METHODS

The reviewed papers were selected from scientific databases and online libraries. We included studies with a direct measure of hair mercury concentrations in a sample size larger than 10 people, without considering the objectives, approach of the study or mercury speciation. The results are presented in tables and maps by river basin, displaying hair mercury levels and specifying the studied population and health impact, if any.

RESULTS

The majority of the studies have been carried out in communities from the central Amazonian regions, particularly on the Tapajós River basin. The results seem quite variable; hair mercury means range from 1.1 to 34.2 microg/g. Most studies did not show any significant difference in hair mercury levels by gender or age. Overall, authors emphasized fish consumption frequency as the main risk factor of exposure. The most studied adverse health effect is by far the neurological performance, especially motricity. However, it is not possible to conclude on the relation between hair mercury levels and health impact in the Amazonian situation because of the relatively small number of studies.

CONCLUSIONS

Hair mercury levels in the Amazonian regions seem to be very heterogenic, depending on several factors. There is no obvious spatial trend and there are many areas that have never been studied. Taking into account the low mercury levels currently handled as acceptable, the majority of the Amazonian populations can be considered exposed to methylmercury contamination. The situation for many of these traditional communities is very complex because of their high dependence on fish nutrients. It remains difficult to conclude on the Public Health implication of mercury exposure in this context.

Human mercury exposure and adverse health effects in the Amazon: a review

This paper examines issues of human mercury (Hg) exposure and adverse health effects throughout the Amazon region. An extensive review was conducted using bibliographic indexes as well as secondary sources. There are several sources of Hg (mining, deforestation, reservoirs), and exposure takes place through inhalation or from fish consumption. There is a wide range of exposure, with mean hair-Hg levels above 15 microg/g in several Amazonian communities, placing them among the highest reported levels in the world today. Dietary Hg intake has been estimated in the vicinity of 1-2 microg/kg/day, considerably higher than the USEPA RfD of 0.1 microg/kg/day or the World Health Organization recommendation of 0.23 microg/kg/day. Neurobehavioral deficits and, in some cases, clinical signs have been reported both for adults and children in relation to Hg exposure in several Amazonian countries. There is also some evidence of cytogenetic damage, immune alterations, and cardiovascular toxicity. Since fish provide a highly nutritious food source, there is an urgent need to find realistic and feasible solutions that will reduce exposure and toxic risk, while maintaining healthy traditional dietary habits and preserving this unique biodiversity.

Prenatal and early childhood exposure to mercury and methylmercury in Spain, a high-fish-consumer country

Exposure to mercury, a risk factor for neurodevelopmental toxicity, was assessed in Spanish children (preschool children and newborns, n = 218) in a four-locations survey by performing mercury determination in hair. To assess the prenatal and children's exposure and its potential risk, total mercury (THg) and methylmercury (MeHg) were analyzed and examined for associations with maternal sociodemographic characteristics and dietary intake through interviews and food frequency questionnaires. The mean THg in hair was 0.94 microg/g, ranging from 0.19 to 5.63 microg/g in preschool children and 1.68 microg/g (0.13-8.43 microg/g) in newborns. Associations between mercury levels in hair and fish consumption frequency were found regardless of the group evaluated. Neither other food item nor maternal covariates were associated with mercury levels in the newborn group. In children, the mean THg values among frequent fish consumers (more than four times per week) were almost threefold higher compared with non-consumers (1.40 vs. 0.49 microg/g). Newborns from mothers who had intake of fish two or more times per week exhibited nearly threefold higher hair levels than those who rarely or never consumed fish (2.26 vs. 0.78 microg/g). Finally, mercury levels in hair exceeded the EPA reference dose (RfD) of 0.1 microg Hg/kg body weight per day (equivalent to 1 microg Hg/g hair) in 42% of the population studied. Overall, we conclude that levels of mercury in Spain are among the highest in the non-exposed populations probably because of the relatively high fish consumption.

A nutritional dilemma: fish consumption, mercury exposure and growth of children in Amazonian Bolivia

To study associations between nutritional status and mercury exposure among communities of the Beni River. Cross-sectional survey of mothers and their children from 15 riverside Amerindian communities in the Beni River valley (Amazonian Bolivia). Hair mercury content (H-Hg) served as a bioindicator of mercury exposure. A total of 556 people were measured. Anthropometric indices of nutrition were calculated after measurements of stature, weight, arm circumference and subcutaneous fat folds. Indicators of lifestyle were collected: subsistence activity, fish consumption and ethnicity. The median of H-Hg was equal to 4.0 microg/g (CI 95%: 3.6 approximately 4.4). There existed a significant relationship between H-Hg and nutritional indices in 5- to 10-year-old children (F = 12.1; p < 0.0001) but not in other age groups. Fishing activity, fish consumption and ethnicity had an effect upon the variance of H-Hg. Positive relationships between nutritional status and H-Hg may be related to the high nutritional value of fish. Among women, the relationship between H-Hg and nutritional status was negative (F = 7.1; p < 0.001), but this disappeared when ethnicity and subsistence activity were taken into account. In these Amazonian communities, recommendations aimed at lowering fish consumption to prevent mercury exposure should be balanced against nutritional advantages conferred upon growing children.

Maternal fish consumption in the nutrition transition of the Amazon Basin: growth of exclusively breastfed infants during the first 5 years

BACKGROUND

Changes in fish-eating habits due to rapid urbanization in Western Amazon was used as model to investigate whether maternal fish-intake rate impacts on children's weight and height during the first 5 years.

AIM

The study examined the growth of 82 breastfed children, and maternal fish consumption (hair mercury concentrations, HHg) during pregnancy and lactation.

SUBJECTS AND METHODS

Fish consumption in mothers and children was estimated through HHg. The children were measured and weighed at birth and at 6 (exclusive breastfeeding), 36 and 60 months.

RESULTS

Fish consumption rate (HHg) had no significant impact on children's growth at the specified ages (p = 0.35). After 6 months of exclusive breastfeeding, children had the highest proportion of Z-scores <-1 SD; however, weaning (with extended breastfeeding) had a substantial impact in moving up the attained growth at 3 years. The duration of breastfeeding was significantly correlated with attained Z-scores for weight-for-age (r = 0.26; p = 0.02) and weight-for-height (r = 0.22; p = 0.04) but not for height-for-age. At 3 years most children had improved Z-scores (>-1 SD) for height-for-age (70/82), weight-for-age (74/82) and weight-for-height (74/82). At 5 years, all but one child attained Z-scores >-1.

CONCLUSION

The apparently good nutritional status of subjects is more likely due to a well balanced diet composition than to only one dietary protein source--fish.

Persistent, bioaccumulative and toxic substances in fish: human health considerations

Fish are important dietary items that provide essential nutrients. Fish however, bioaccumulate monomethyl mercury (MMHg) and organo-halogenated pollutants (OHP) that are persistent bioaccumulative and toxic substances (PBTS). Unlike man-made OHP, MMHg is mainly of natural origin but background concentrations of aquatic systems are determined by the environmental Hg-methylating potential. Industrial activities can modulate environmental discharges and fish bioaccumulation of PBTS. Fish and seafood consumption are associated with human body load of PBTS, but farming practices that utilize fishmeal increase the terrestrial food chain resulting in farm-animal accumulation of PBTS. These substances are neurotoxic and endocrine active that can impact humans and wild life, but chemical characteristics of MMHg and OHP modulate interactions with animal tissues. MMHg is protein reactive with a faster metabolism (months) than OHP that are stored and slowly (years) metabolized in fat tissues. Except for brain-Hg, neither Hg nor OHP in tissues are markers of toxic effects; however, deficits in neurobehavioral test-scores of children have been shown in some fish-eating populations. These deficits are transient and within normal range, and are not prodromes of neurological diseases. Although population studies show that consumption of fish at current levels of contamination do not explain neurological disorders, endocrine activity remains controversial. Understanding risk of hazard caused by fish-PBTS consumption requires a wide range of expertise. We discuss chemical, toxic, metabolic, and ecological characteristics associated with PBTS in fish. There are proven health outcome derived from fish consumption, while risk of exposure to avoidable PBTS is a chance that can be minimized by societal actions.

Poor psychometric scores of children living in isolated riverine and agrarian communities and fish-methylmercury exposure

Because of heavy dependence on fish, Amazonian riparian communities are chronically exposed to high levels of methylmercury (MeHg). We studied fish-MeHg exposure (total hair-Hg, HHg) as a determinant of neurocognitive scores of children living in two geographically distant, culturally distinct and isolated poor communities of non-urban environments: Amazonian riverines (Riparians, n=38) of the Puruzinho Lake community in the Rio Madeira Basin and rural agrarians from Iúna, Espírito Santo (Agrarians, n=32). Nutritional status was estimated by anthropometry (Z-scores) and individual cognitive abilities were assessed by the Wechsler Intelligence Scale for Children-III (WISC-III) and the Human Figure Drawings (HFD), both validated versions for Brazilian children. Anthropometric assessment showed slightly elevated Z-scores for the Agrarian children (not statistically significant) but median HHg concentrations were 14.4 and 0.25microgg(-1) respectively for Riparian and Agrarian children (p=0.000). Despite paradoxical MeHg exposures, both groups showed comparable HFD scores but very poor performance in WISC-III test battery; median of sum of WISC-III subtests scores (SigmaTOT) were 17.9 and 28.6 (p<0.000) for Riparian and Agrarian children, respectively (percentage scale). Spearman correlation between nutritional status (attained growth) and psychometric scores were statistically significant between height-for-age Z-score and Object Assembly subtest (r=0.269; p=0.043), SigmaTOT (r=0.319; p=0.016), Performance-IQ (r=0.311; p=0.019) and Perceptual Organization Index scores (r=0.302; p=0.023). In these isolated communities there are stronger determinants of neurocognitive poor performance than MeHg exposure. Global strategies for reducing human exposure to MeHg by curtailing fish consumption are unrealistic options for riverine subsistence populations and are not justifiable to prevent low cognitive scores.

Changes in children hair-Hg concentrations during the first 5 years: Maternal, environmental and iatrogenic modifying factors

Children are exposed to Hg from mothers (via placenta and lactation), environment (food), and in many parts of the world by thimerosal-containing vaccines (TCV) during immunization. Neurodevelopment studies based on infant hair-Hg (HHg) have been designed without explicit attention to the factors associated with changes in infant physiology and Hg sources of exposure. A longitudinal study of changes in HHg concentrations from birth to 5 years was done in a sample of children from Porto Velho (Rondonia), Brazilian Amazonia. The study extracted information from the asymmetry associated with maternal and infant HHg changes at specified sampling: birth (fetal exposure), 6 months of exclusive breastfeeding, 36 months (weaning) and 60 months (pre-school). The distribution of HHg in breastfed infants followed a pattern different from their mothers. While mothers had the highest HHg concentrations at childbirth, infants showed the highest HHg values at 6 months after the recommended full schedule (six shots) of immunization with TCV; after that, the downward trend in HHg shown by children coincided with both weaning and less frequent vaccination period (5 years). Extended lactation (up to 36 months) was not significantly associated with HHg of infants or mothers; however, significant association (Spearman's r) between maternal and infant HHg concentration was seen at birth (r=0.3534; P=0.001), 6 months (r=0.4793; P<0.0001), 3 years (r=0.0122; P=0.012) and 5 years (r=0.0357; P=0.005). Maternal postpartum metabolic changes, infant development and transitional diets and possibly Hg from TCV contribute to the asymmetry of HHg changes between mothers and children.

Maternal mercury exposure and neuro-motor development in breastfed infants from Porto Velho (Amazon), Brazil

Fish is an important item in the diet of Amazonians, and per se is their best single source of essential nutrients. Rapid urbanization and migration are bringing changes in dietary habits of Amazonians. Exposure to fish-Hg during pregnancy and lactation were studied in 100 women and newborns from Porto Velho. Tissue-Hg concentrations and neurodevelopment (Gesell Developmental Schedules) were assessed at birth and at 6 months in exclusively breastfed infants. Maternal mean frequency of fish consumption was low (<2 meals/week; range 0->7 meals/week) compared to Amazonian standards. Women consuming <2 fish meals/week showed less median hair-Hg (3.5 microgg-1) than women that consumed 2 fish meals/week (5.7 microgg). Median total Hg in maternal hair (5.4 microgg-1) was higher than in newborns (1.6 microgg-1). Significant correlation was observed between maternal hair-Hg and infant hair-Hg at birth (r=0.353; p<0.01) and at six months (r=0.510; p<0.01). Placenta-Hg was also significantly correlated to maternal hair-Hg (r=0.321; p<0.01), newborn hair-Hg (r=0.219; p<0.05), maternal blood-Hg (r=0.250; p<0.01) and to umbilical cord-Hg (r=0.857; p<0.01). Most infants (74%) had normal Gesell Schedules but among the 26% showing neuro-motor development delays only six (7%) had multiple (motor, language, and adaptative) delays. The infants with multiple delays were born from mothers with range of hair-Hg comparable to mothers of normally developed infants. Coincidentally, mothers of infants with multiple delays also showed the lowest range of income and level of education. Fish consumption, income, and level of education varied greatly among these breastfeeding urban mothers. It seems that development delays of exclusively breastfed infants are a component of the health inequalities that accompanies socioeconomic disadvantages.

A preliminary study of mercury exposure and blood pressure in the Brazilian Amazon

BACKGROUND

Fish is considered protective for coronary heart disease (CHD), but mercury (Hg) intake from fish may counterbalance beneficial effects. Although neurotoxic effects of methylmercury (MeHg) are well established, cardiovascular effects are still debated. The objective of the present study was to evaluate blood pressure in relation to Hg exposure and fish consumption among a non-indigenous fish-eating population in the Brazilian Amazon.

METHODS

The study was conducted among 251 persons from six communities along the Tapajós River, a major tributary of the Amazon. Data was obtained for socio-demographic information, fish consumption, height and weight to determine body mass index (BMI), systolic and diastolic blood pressure, and Hg concentration in hair samples.

RESULTS

Results showed that overall, systolic and diastolic blood pressure, were relatively low (mean: 113.9 mmHg +/- 14.6 and 73.7 mmHg +/- 11.0). Blood pressure was significantly associated with hair total Hg (H-Hg), age, BMI and gender. No association was observed between fish consumption and blood pressure, although there were significant inter-community differences. Logistic regression analyses showed that the Odds Ratio (OR) for elevated systolic blood pressure (> or = 130 mmHg) with H-Hg > or = 10 microg/g was 2.91 [1.26-7.28], taking into account age, BMI, smoking, gender and community.

CONCLUSION

The findings of this preliminary study add further support for Hg cardiovascular toxicity.

Mercury speciation in the hair of pre-school children living near a chlor-alkali plant

Exposure to mercury species was assessed in the hair of 130 Spanish children (age 4) from the general population in two areas. Both areas are exposed to different sources of mercury: a point source in Ribera d'Ebre (northeastern Spain) and a diffuse source on the island of Menorca (northwestern Mediterranean). The median MeHg values in the hair of children from Ribera d'Ebre (RE) were nearly twice (0.631 microg/g vs. 0.370 microg/g) those of children from Menorca (MC) (p < 0.05). Total Hg showed a similar trend (REmedian: 0.720 microg/g vs. MCmedian: 0.476 microg/g). Nevertheless, inorganic mercury levels were similar in the two groups of children (REmedian: 0.186 microg/g vs. MCmedian: 0.210 microg/g). Two subgroups of the Ribera d'Ebre group were defined: children living in Flix (a village near a chlor-alkali plant) (RE1) and children living on the outskirts of Flix with no clear, direct influence of the plant (RE2). The mercury concentrations in RE1 were also significantly higher than those in Menorca, but no significant differences were found between Menorca and the RE2 subgroup. We evaluated the fish consumption of RE1, RE2 and MC and found that the Menorcan children consumed significantly less fish (p < 0.05) than the other two subgroups. Children who consumed fish more than three times a week had higher MeHg concentrations (beta (SE) = 0.991 (0.279) than those who ate it less than once a week. Nevertheless, the differences in MeHg levels between children from Ribera d'Ebre and Menorca remained statistically significant after adjustment for fish intake and other variables (beta (SE) = 0.779 (0.203) for children from RE1). In conclusion, local sources other than seafood contribute significantly to MeHg content in hair in the two Ribera d'Ebre subgroups.