Mercury contamination of fish and exposures of an indigenous community in Pará state, Brazil

Fish consumption habits of pregnant women in Itaituba, Tapajós River basin, Brazil: risks of mercury contamination as assessed by measuring total mercury in highly consumed piscivore fish species and in hair of pregnant women

The Tapajós River basin in the Amazon region, Brazil is one of the most active gold mining areas in the world. In this study, we evaluated fish consumption habits and mercury exposure in 110 pregnant women in the city of Itaituba by measuring their total hair mercury concentrations. In addition, we investigated seasonal differences in mercury concentrations in two highly consumed piscivorous fish species, tucunaré (Cichla spp.) and pescada (Plagioscion squamosissimus). Total fish mercury concentrations (THg) during the dry season were 0.62±0.07 mg/kg for Cichla spp. and 0.73±0.08 mg/kg for P. squamosissimus. During the rainy season they were 0.39±0.04 and 0.84±0.08 mg/ kg, respectively. Of our participants 44 % declared that they ate Cichla spp. and 67 % P. squamosissimus. Mean mercury concentration in their hair was 1.6±0.2 mg/kg and was above the US Environmental Protection Agency (US EPA) reference dose of 1 mg/kg in 48 % of them. Mean fish THg concentrations were also above the joint Food and Drug Administration and US EPA safety limit of 0.5 mg/kg for P. squamosissimus during both seasons and for Cichla spp. during the dry season only. These results show that pregnant women should avoid consumption of these piscivorous fish species during pregnancy and call for a regular programme to monitor Hg levels in that area.

An Assessment of Health Outcomes and Methylmercury Exposure in Munduruku Indigenous Women of Childbearing Age and Their Children under 2 Years Old

In line with the 1000-day initiative and the Sustainable Development Goals (SDG) 2 and 3, we present a cross-sectional analysis of maternal health, infant nutrition, and methylmercury exposure within hard-to-reach indigenous communities in the state of Pará, Brazilian Amazon. We collected data from all women of childbearing age (i.e., 12-49) and their infants under two years old in three Munduruku communities (Sawré Muybu, Sawré Aboy, and Poxo Muybu) along the Tapajos River. We explored health outcomes through interviews, vaccine coverage and clinical assessment, and determined baseline hair methylmercury (H-Hg) levels. Hemoglobin, infant growth (Anthropometric Z scores) and neurodevelopment tests results were collected. We found that 62% of women of childbearing age exceeded the reference limit of 6.0 μg/g H-Hg (median = 7.115, IQR = 4.678), with the worst affected community (Sawré Aboy) registering an average H-Hg concentration of 12.67 μg/g. Half of infants aged under 24 months presented with anemia. Three of 16 (18.8%) infants presented H-Hg levels above 6.0 µg/g (median: 3.88; IQR = 3.05). Four of the 16 infants were found to be stunted and 38% of women overweight, evidencing possible nutritional transition. No infant presented with appropriate vaccination coverage for their age. These communities presented with an estimated Infant Mortality Rate (IMR) of 86.7/1000 live births. The highest H-Hg level (19.6 µg/g) was recorded in an 11-month-old girl who was found to have gross motor delay and anemia. This already vulnerable indigenous Munduruku community presents with undernutrition and a high prevalence of chronic methylmercury exposure in women of childbearing age. This dual public health crisis in the context of wider health inequalities has the potential to compromise the development, health and survival of the developing fetus and infant in the first two critical years of life. We encourage culturally sensitive intervention and further research to focus efforts.

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.

Mercury in blood, hair, and feces from subsistence fish-eating riverines of the Madeira River Basin (Western Amazon)

BACKGROUND

The Madeira River (Amazon Basin) has been impacted by activities related to artisanal and small-scale gold mining (ASGM), deforestation and burning (for timber, agriculture, and hydroelectric dam projects). All these activities contribute to environmental mercury (Hg) release and cycling into the Amazon ecosystem and thus to changing lifestyles.

METHOD

We assessed exposure to total and MeHg in two small riverine communities of the Madeira River (Amazon): Lago Puruzinho (LP, n = 26 families) and São Sebastião do Tapurú (SST, n = 31 families). Samples of human hair (n = 137), blood (n = 39), and feces (n = 41) were collected from adults and children (0-15 years of age).

RESULTS

In women of childbearing age from LP village, the mean blood total-Hg (THg) (45.54 ± 24.76 μg.L^-1) and MeHg (10.79 ± 4.36 μg.L^-1) concentrations were significantly (p = 0.0024; p < 0.0001, respectively) higher than in women from SST village (THg: 25.32 ± 16.75 μg.L^-1; MeHg: 2.32 ± 1.56 μg.L^-1) village; the trend in hair-Hg persisted but was statistically significant (p < 0.0145) only for THg (LP, 11.34 ± 5.03 μg. g^-1; SST, 7.97 ± 3.51 μg. g^-1). In women, the median hair:blood ratio of total Hg was 269. In children, the mean hair THg concentrations were 6.07 ± 3.60 μg. g^-1 and 6.47 ± 4.16 μg. g^-1 in LP and SST; thus, not significantly different (p = 0.8006). There was a significant association (p < 0.001) between hair-Hg concentrations of mothers and their respective children. The excretion of Hg in feces of women (0.52 μg. g^-1 dw) was not significantly different from children (0.49 μg. g^-1 dw). The only statistically significant correlation between Hg in feces and in hair was found in children, (n = 16, r_s = 0.38, p = 0.005). Significant relationship was seen between the levels of THg in blood and hair of women from LP and SST. Based on hair-Hg concentrations, fish consumption rate ranged from 94.5 to 212.3 g.day^-1.

CONCLUSION

Women and children excrete THg in feces in comparable concentrations. However, the mean fish consumption rate and blood MeHg are higher in the most remote villagers. Mother`s hair-Hg concentration is a good predictor of children's hair-Hg.

Impacts of the Goldmining and Chronic Methylmercury Exposure on the Good-Living and Mental Health of Munduruku Native Communities in the Amazon Basin

This paper is an exploratory study that examines the illegal goldmining impacts on Munduruku communities' "Good-Living" (Xipan Jewewekukap) and explores the possible relationship between chronic methylmercury (MeHg) exposure and the worsening mental health conditions in three villages in the Middle-Tapajós River, Brazilian Amazon. The region has been experiencing a long-lasting threat of goldminers' invasions. A total of 109 people were interviewed and evaluated. Total mercury (THg) exposure levels were evaluated through hair samples analysis, from which MeHg exposure levels were calculated. The Geriatric Depression Scale-Short Form (GDS-SF) was used as a screening tool in order to assess mental health indicators. Brief non-structured interviews were carried out to investigate how goldmining is impacting the communities Good-Living. A Poisson regression model was used to estimate the possible association between mental health indicators (assessed through the GDS-SF) and the following independent variables: (i) mercury exposure level (<10.0 μg/g vs. ≥10.0 μg/g), (ii) self-reported nervousness, (iii) self-reported irritability, (iv) age group, and (v) monthly income. The analysis revealed high levels of mercury in hair samples (median: 7.4 µg/g, range 2.0-22.8; 70% and 28% of the participants had THg levels ≥6.0 and ≥10.0 µg/g, respectively) and pointed to a tendency in which higher levels of methylmercury exposure (Hg ≥ 10.0 µg/g) could be linked to worse mental health indicators. Although the GDS-SF has presented limitations due to the Munduruku sociocultural context, our findings suggest a tendency of worse mental health indicators in participants presenting high levels of MeHg exposure. Despite this limitation, the qualitative approach indicates an evident association between the impacts of goldmining and the Munduruku people's decreasing autonomy to maintain a Good-Living on their own terms, pointing to the importance of carrying out new investigations, especially considering longitudinal studies with qualitative methodologies and ethnographic approaches.

Negative impacts of mining on Neotropical freshwater fishes

Abstract Mining activities have significantly affected the Neotropical freshwater ichthyofauna, the most diverse in the world. However, no study has systematized knowledge on the subject. In this review, we assembled information on the main impacts of mining of crude oil, gold, iron, copper, and bauxite on aquatic ecosystems, emphasizing Neotropical freshwater fishes. The information obtained shows that mining activities generate several different disturbances, mainly via input of crude oil, metals and other pollutants, erosion and siltation, deforestation, and road construction. Mining has resulted in direct and indirect losses of fish diversity in several Neotropical waterbodies. The negative impacts on the ichthyofauna may change the structure of communities, compromise entire food chains, and erode ecosystem services provided by freshwater fishes. Particularly noteworthy is that mining activities (legal and illegal) are widespread in the Neotropics, and often located within or near protected areas. Actions to prevent and mitigate impacts, such as inspection, monitoring, management, and restoration plans, have been cursory or absent. In addition, there is strong political pressure to expand mining; if – or when – this happens, it will increase the potential of the activity to further diminish the diversity of Neotropical freshwater fishes.

A State-of-the-Art Review of Indigenous Peoples and Environmental Pollution

Indigenous peoples (IPs) worldwide are confronted by the increasing threat of pollution. Based on a comprehensive review of the literature (n = 686 studies), we present the current state of knowledge on: 1) the exposure and vulnerability of IPs to pollution; 2) the environmental, health, and cultural impacts of pollution upon IPs; and 3) IPs' contributions to prevent, control, limit, and abate pollution from local to global scales. Indigenous peoples experience large burdens of environmental pollution linked to the expansion of commodity frontiers and industrial development, including agricultural, mining, and extractive industries, as well as urban growth, waste dumping, and infrastructure and energy development. Nevertheless, IPs are contributing to limit pollution in different ways, including through environmental monitoring and global policy advocacy, as well as through local resistance toward polluting activities. This work adds to growing evidence of the breadth and depth of environmental injustices faced by IPs worldwide, and we conclude by highlighting the need to increase IPs' engagement in environmental decision-making regarding pollution control. Integr Environ Assess Manag 2020;16:324-341. © 2019 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Assessment of mercury contamination in Brycon falcatus (Characiformes: Bryconidae) and human health risk by consumption of this fish from the Teles Pires River, Southern Amazonia

ABSTRACT Brycon falcatus is one of the most highly consumed species of fish within the region in the Teles Pires basin, and has great commercial importance in sport and professional artisanal fishing. The objective of this study was to analyze the presence and concentration of total mercury (THg) in the muscle, liver and gills of B. falcatus, and calculate the risk to human health of THg contamination from ingestion of the fish. THg concentrations were similar in the liver (0.076 mg kg-1) and muscle (0.052 mg kg-1), and higher than in the gills (0.009 mg kg-1). The levels of HgT present in B. falcatus tissues did not influence weight gain and nutritional status. Based on the condition factor, weight and length ratio and hepatosomatic index, it seems that the concentrations of THg did not influence the health and well-being of B. falcatus collected in the Teles Pires River basin. THg concentrations in the muscle of B. falcatus are below the limit recommended by the World Health Organization for people who consume until 250 g of fish per week. The risk of deleterious effects on human health may exist if there is a greater consumption of B. falcatus such as 340 g/day, that is the mean of fish consumption by indigenous and riverine.

Mercury and methyl mercury in fishes from Bacajá River (Brazilian Amazon): evidence for bioaccumulation and biomagnification

This study assessed total mercury (THg) and methyl mercury (MeHg) concentrations, bioaccumulation and biomagnification of THg through the food web in fishes consumed by indigenous communities of Bacajá River, the largest tributary of the right bank of Xingu River. In total, 496 fish (22 species) were sampled. Nine species had THg concentrations above the limit recommended by the World Health Organisation (0·5 µg g(-1) wet mass), and one exceeded the recommended level for Hg in predatory fishes by Brazilian law (1·0 µg g(-1) ). The average concentration of THg increased significantly with trophic guild (herbivorous to piscivorous) and trophic level, with higher accumulation in fishes with greater total length. Ninety-six per cent of all mercury was methylated. These results suggest that feeding habits determine THg concentrations in fishes and that Hg elimination rate is slow during growth, which allows greater accumulation. These findings show that fishes in the Bacajá River contain high concentrations of THg and MeHg.

Mercury levels of marine fish commonly consumed in Peninsular Malaysia

This study was conducted to determine the concentration of total mercury in the edible portion of 46 species of marine fish (n = 297) collected from selected major fish landing ports and wholesale markets throughout Peninsular Malaysia. Samples were collected in June to December 2009. Prior to analysis, the fish samples were processed which consisted of drying at 65 °C until a constant weight was attained; then, it was grounded and digested by a microwave digestion system. The analytical determination was carried out by using a mercury analysis system. Total mercury concentration among fish species was examined. The results showed that mercury concentrations were found significantly higher (p < 0.001) in demersal fish (the range was from 0.173 to 2.537 mg/kg in dried weight) compared to pelagic fish (which ranged from 0.055 to 2.137 mg/kg in dried weight). The mercury concentrations were also higher in carnivorous fish especially in the species with more predatory feeding habits. Besides, the family group of Latidae (0.537 ± 0.267 mg/kg in dried weight), Dasyatidae (0.492 ± 0.740 mg/kg in dried weight), and Lutjanidae (0.465 ± 0.566 mg/kg in dried weight) showed significantly (p < 0.001) higher mercury levels compared to other groups. Fish collected from Port Klang (0.563 ± 0.509 mg/kg in dry weight), Kuala Besar (0.521 ± 0.415 mg/kg in dry weight), and Pandan (0.380 ± 0.481 mg/kg in dry weight) were significantly higher (p = 0.014) in mercury concentrations when compared to fish from other sampling locations. Total mercury levels were significantly higher (p < 0.002) in bigger fish (body length >20 cm) and were positively related with fish size (length and weight) in all fish samples. Despite the results, the level of mercury in marine fish did not exceed the permitted levels of Malaysian and JECFA guideline values at 0.5 mg/kg methylmercury in fish.

Comparative study of mercury speciation in commercial fishes of the Brazilian Amazon

Mercury is responsible for serious episodes of environmental pollution throughout the world, especially in the Amazon. This toxicity has led regulatory agencies to focus on fish as the target organism for protecting the health of humans and other sensitive organisms. Unfortunately, in the Amazon area, different sampling strategies and the wide variety of sampling areas and fish species make it extremely difficult to determine relationships across geographic regions or over time to ascertain historical trends. Thus, the aim of this work was to achieve three main objectives: a comparative study of mercury contamination in fish of Itaituba (Tapajós, located downstream of the largest gold-mining region in Amazon) and Belém (an area non-exposed to mercury pollution of anthropogenic origin), perform an analysis of inorganic mercury (IHg) versus monomethylmercury (MeHg) contents, and, finally, compare mercury contamination in Tapajós over time. Five piscivorous species were obtained in Itaituba and Belém. Also, four non-piscivorous species were collected in Itaituba. For the first time, mercury speciation showed that (1) current MeHg levels in piscivorous species in Tapajós are higher than those of the non-exposed area, (2) piscivorous species from Itaituba (dourada, filhote, and sarda) contained mercury levels above the World Health Organization safety limit (~17%) and/or above the US Environmental Protection Agency tissue residue criterion (40%), (3) increased MeHg is usually accompanied by increased IHg, and (4) the mean total mercury concentrations for piscivorous species in Itaituba were within the same range and, associated uncertainties as those previously reported, although a remarkable decreasing trend over time was observed for mean total Hg concentrations in non-piscivorous species from Itaituba. The present study supports the importance of continuous monitoring of both populations in the Amazon Rivers. Our results will better assist the development of preventive strategies and governmental actions to confront the problem of mercury contamination in the Amazon.

Amazonian former gold mined soils as a source of methylmercury: evidence from a small scale watershed in French Guiana

Total mercury (HgT) and monomethylmercury (MMHg) were investigated in a tropical head watershed (1 km(2)) of French Guiana. The watershed includes a pristine area on the hill slopes and a former gold mined flat in the bottomland. Concentrations of dissolved and particulate HgT and MMHg were measured in rain, throughfall, soil water and at three points along the stream. Samples were taken in-between and during 14 storm events at the beginning and middle of the 2005 and 2006 rainy seasons. Dissolved and particulate HgT concentrations in the stream slightly increased downstream, while dissolved and particulate MMHg concentrations were low at the pristine sub-watershed outlet (median = 0.006 ng L(-1) and 1.84 ng g(-1), respectively) and sharply increased at the gold mined flat outlet (median = 0.056 ng L(-1) and 6.80 ng g(-1), respectively). Oxisols, which are dominant in the pristine area act as a sink of HgT and MMHg from rain and throughfall inputs. Hydromorphic soils in the flat are strongly contaminated with Hg (including Hg(0) droplets) and their structure has been disturbed by former gold-mining processes, leading to multiple stagnant water areas where biogeochemical conditions are favorable for methylation. In the former gold mined flat high dissolved MMHg concentrations (up to 0.8 ng L(-1)) were measured in puddles or suboxic soil pore waters, whereas high dissolved HgT concentrations were found in lower Eh conditions. Iron-reducing bacteria were suggested as the main methylators since highest concentrations for dissolved MMHg were associated with high dissolved ferrous iron concentrations. The connection between saturated areas and stagnant waters with the hydrographic network during rain events leads to the export of dissolved MMHg and HgT in stream waters, especially at the beginning of the rainy season. As both legal and illegal gold-mining continues to expand in French Guiana, an increase in dissolved and particulate MMHg emissions in the hydrographic network is expected. This will enhance MMHg bio-amplification and present a threat to local populations, whose diet relies mainly on fish.

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.

Mercury and Selenium - A Review on Aspects Related to the Health of Human Populations in the Amazon

Mercury (Hg) toxicity is governed by cellular thiol compounds and its capacity to generate reactive oxygen radicals and oxidative stress. Selenium (Se) plays a key role in the prevention of the toxic effects of Hg by modulating the activity of several Se-dependent enzymes, including glutathione peroxidase (GSH-Px). In addition, dietary Se can reduce Hg toxicity by directly interacting with either Hg(II) or methylmercury (MeHg) to form inert products, such as HgSe complexes.. Although experimental and environmental data have indicated a protective role for selenium against Hg toxicity, human data are more limited and somewhat conroversial In the Amazon Region of Brazil, Hg pollution is rampant as a result of gold (Au) mining and other anthropogenic factors, leading to pervasive release of large quantities of metallic Hg⁰ into the environment. Exposure to Hg in this region is associated with direct occupational exposure in the gold mining industry, as well as consumption by in inhabitants of riverside communities of a diet rich in MeHg-contaminated fish. Human exposure to MeHg in the Amazon through the diet has been monitored by measuring Hg and MeHg in hair samples. In this paper, we review the environmental contamination of Hg in the Amazon and detail human exposures in populations of this region. We conclude with a brief synopsis on Se levels in the Amazon population and provide a brief review of data available on the interaction between Hg and Se in this region. Overall, the literature supports the notion that low environmental Se is linked to susceptibility to Hg toxicity and that Se levels could be used as a bioindicator to monitor the health of Hg exposed subjects. However, in light of the limited human data on this subject, further epidemiological studies are needed to clarify how changes in Se levels modify the toxicity of environmental Hg.

Mercury in fish: Concentrationvs. fish size and estimates of mercury intake

Total mercury concentrations were determined in different fish size classes of commercial importance such as, conger eel (Conger conger), starry ray (Raja asterias), forkbeard (Phycis blennoides), frostfish (Lepidopus caudatus), striped mullet (Mullus barbatus), red gurnard (Aspitrigla cuculus) and yellow gurnard (Trigla lucerna) in order to evaluate variations in consumer exposure to mercury as a function of fish consumption of a spectrum of different sizes. The highest mean levels of total mercury were detected in conger eel (0.80 microg g(-1)) and starry ray (0.75 microg g(-1)). Forkbeard (0.67 microg g(-1)), frostfish (0.59 microg g(-1)) and striped mullet (0.55 microg g(-1)) showed slightly lower levels, while red gurnard (0.33 microg g(-1)) and yellow gurnard (0.22 microg g(-1)) exhibited the lowest concentrations. The results of linear regression analysis showed a significant relationship between mercury concentrations and fish size for all species. Consequently, dietary consumption of larger size specimens leads to an increase in the exposure level for consumers. Understanding by consumers of all factors leading to an increase of exposure to mercury is the first step to enable them to make decisions about eating fish.

Lower than expected mercury concentration in piscivorous African sharptooth catfish Clarias gariepinus (Burchell)

The concentrations of total mercury (THg), stable isotopes of nitrogen (delta(15)N) and carbon (delta(13)C), and the diet of the African sharptooth catfish Clarias gariepinus in Lake Awassa, Ethiopia, were studied from January 2003 to February 2004. Values of the delta(15)N were used as an index of trophic position in four length groups and compared to actual stomach contents. The diet of C. gariepinus within the length range of 201-600 mm L(T) mainly consisted of the small barb Barbus paludinosus, aquatic insects, and mollusks. The proportion of fish prey in the diet was 60% by volume, irrespective of fish size. The differences in delta(15)N values of individuals within and between length classes were less than 3 per thousand, and were not significantly related to total length, showing the similarity in trophic niche of the different sizes, which corresponded to recorded stomach contents. Mercury concentrations were in the range of 0.002-0.154 mg kg(-1) ww, and had no significant relationship to total length. Hence, even large specimens of C. gariepinus have Hg values below the WHO threshold of 0.2 mg kg(-1) ww. The slope of the regression line between log [Hg] and delta(15)N was small, 0.06, indicating the absence of trophic shifts and biomagnification of Hg in larger specimens in our samples. The low Hg concentrations in C. gariepinus compared to the Hg concentrations in other piscivorous fish species in Lake Awassa, such as Barbus intermedius and B. paludinosus, may be due to its dependence on invertebrate preys at small size, diet switching towards low Hg prey fish at larger size, and growth biodilution owing to higher growth rate.

Effects of mercury intoxication on the response of horizontal cells of the retina of thraira fish (Hoplias malabaricus)

Methyl mercury (MeHg) is highly neurotoxic, affecting visual function in addition to other central nervous system functions. The effect of mercury intoxication on the amplitude of horizontal cell responses to light was studied in the retina of the fish Hoplias malabaricus. Intracellular responses were recorded from horizontal cells of fish previously intoxicated with MeHg by intraperitoneal injection (IP group) or by trophic exposure (T group). Only one retina per fish was used. The doses of MeHg chloride administered to the IP group were 0.01, 0.05, 0.1, 1.0, 2.0, and 6.0 mg/kg. The amplitudes of the horizontal cell responses were lower than control in individuals exposed to 0.01 (N = 4 retinas), 0.05 (N = 2 retinas) and 0.1 mg/kg (N = 1 retina), whereas no responses were recorded in the 1.0, 2.0, and 6.0 mg/kg groups. T group individuals were fed young specimens of Astyanax sp previously injected with MeHg corresponding to 0.75 (N = 1 retina), 0.075 (N = 8 retinas) or 0.0075 (N = 4 retinas) mg/kg fish body weight. After 14 doses, one every 5 days, the amplitude of the horizontal cell response was higher than control in individuals exposed to 0.075 and 0.0075 mg/kg, and lower in individuals exposed to 0.75 mg/kg. We conclude that intoxication with MeHg affects the electrophysiological response of the horizontal cells in the retina, either reducing or increasing its amplitude compared to control, and that these effects are related to the dose and/or to the mode of administration.

Mercury toxicity in the Amazon: contrast sensitivity and color discrimination of subjects exposed to mercury

We measured visual performance in achromatic and chromatic spatial tasks of mercury-exposed subjects and compared the results with norms obtained from healthy individuals of similar age. Data were obtained for a group of 28 mercury-exposed subjects, comprising 20 Amazonian gold miners, 2 inhabitants of Amazonian riverside communities, and 6 laboratory technicians, who asked for medical care. Statistical norms were generated by testing healthy control subjects divided into three age groups. The performance of a substantial proportion of the mercury-exposed subjects was below the norms in all of these tasks. Eleven of 20 subjects (55%) performed below the norms in the achromatic contrast sensitivity task. The mercury-exposed subjects also had lower red-green contrast sensitivity deficits at all tested spatial frequencies (9/11 subjects; 81%). Three gold miners and 1 riverine (4/19 subjects, 21%) performed worse than normal subjects making more mistakes in the color arrangement test. Five of 10 subjects tested (50%), comprising 2 gold miners, 2 technicians, and 1 riverine, performed worse than normal in the color discrimination test, having areas of one or more MacAdam ellipse larger than normal subjects and high color discrimination thresholds at least in one color locus. These data indicate that psychophysical assessment can be used to quantify the degree of visual impairment of mercury-exposed subjects. They also suggest that some spatial tests such as the measurement of red-green chromatic contrast are sufficiently sensitive to detect visual dysfunction caused by mercury toxicity.

Decrease of soil fertility and release of mercury following deforestation in the Andean Amazon, Napo River Valley, Ecuador

Soil erosion and degradation provoked by deforestation in the Amazon is a global concern, and recent studies propose a link between deforestation, soil erosion and the leaching of naturally occurring mercury (Hg). In the Ecuadorian Amazon, elevated deforestation rates and the proximity of volcanoes could play an important role in soil fertility and soil Hg levels. The goal of this study is to evaluate the impacts of deforestation on Andisol and Inceptisol fertility and Hg levels in the Napo River Valley, Ecuador. Results show a significant decrease in surface soil organic matter (-15% to -70% of C and N) and exchangeable cations (-25% to -60%) in deforested plots. Hg concentrations at the surface (0-5 cm), higher in Andisols (225 ng/g average) than in Inceptisols (95 ng/g average), show a decrease of up to 60% following deforestation. Soil erosion exposes the mineral horizon, a layer with a higher Hg burden, to the elements thus provoking and accelerating Hg leaching. These results suggest that deforestation and the associated Hg leaching could contribute to the fish Hg contamination measured in the Napo River watershed.

Abatement of mercury pollution in the small-scale gold mining industry: restructuring the policy and research agendas

This paper critiques contemporary research and policy approaches taken toward the analysis and abatement of mercury pollution in the small-scale gold mining sector. Unmonitored releases of mercury from gold amalgamation have caused considerable environmental contamination and human health complications in rural reaches of sub-Saharan Africa, Latin America and Asia. Whilst these problems have caught the attention of the scientific community over the past 15-20 years, the research that has since been undertaken has failed to identify appropriate mitigation measures, and has done little to advance understanding of why contamination persists. Moreover, the strategies used to educate operators about the impacts of acute mercury exposure, and the technologies implemented to prevent further pollution, have been marginally effective at best. The mercury pollution problem will not be resolved until governments and donor agencies commit to carrying out research aimed at improving understanding of the dynamics of small scale gold mining communities. Acquisition of this knowledge is the key to designing and implementing appropriate support and abatement measures.

Fish mercury bioaccumulation as a function of feeding behavior and hydrological cycles of the Rio Negro, Amazon

The acidic black waters of the Rio Negro are unimpacted by anthropogenic sources and yet, are characterized by fish containing relatively high Hg concentrations. Regular annual flooding alters the aquatic environment, thereby affecting fish feeding strategies. We studied the impact of annual flooding on fish-Hg bioaccumulation. Tucunarés (Cychla spp, carnivorous), Peixe-cachorro (Hydrolycus scomberoides, carnivorous), Traíra (Hoplias malabaricus, carnivorous), Piranha-branca (Serrasalmus aff. eigenamanni, carnivorous), Piranha-preta (Serrasalmus rhombeus, carnivorous), Acará (Acarichthys heckellii, omnivorous), Aracú (Leporinus friderici, omnivorous), Orana-preta (Hemiodus unimaculatus, omnivorous), Sardinha (Triportheus elongatus, omnivorous), Branquinha (Potamorhina latior, detritivorous), Jaraqui-escama-fina (Semaprochilodus taeniurus, detritivorous), and Pacú-branco (Myleus torquatus, herbivorous) were studied during high (July) and low waters (February) and categorized by body mass. Regardless of hydrological period, ranges of total-Hg concentrations were higher for carnivorous than for omnivorous, detritivorous and herbivorous species. Some species (Traíra, Sardinha, Peixe-cachorro, Piranha branca, Piranha preta) showed changes in feeding patterns as indicated by an inverse trend of Hg bioaccumulation with season. Species with similar trends of Hg bioaccumulation showed higher Hg concentrations during the flooded season (Aracú, Pacú branco and Orana preta) and some had lower Hg (Acará, Branquinha and Tucunarés). Fish Hg concentration is species specific and reflects changes in feeding-behavior dominance brought by annual inundation.

Losses of immunoreactive parvalbumin amacrine and immunoreactive alphaprotein kinase C bipolar cells caused by methylmercury chloride intoxication in the retina of the tropical fish Hoplias malabaricus

To quantify the effects of methylmercury (MeHg) on amacrine and on ON-bipolar cells in the retina, experiments were performed in MeHg-exposed groups of adult trahiras (Hoplias malabaricus) at two dose levels (2 and 6 microg/g, ip). The retinas of test and control groups were processed by mouse anti-parvalbumin and rabbit anti-alphaprotein kinase C (alphaPKC) immunocytochemistry. Morphology and soma location in the inner nuclear layer were used to identify immunoreactive parvalbumin (PV-IR) and alphaPKC (alphaPKC-IR) in wholemount preparations. Cell density, topography and isodensity maps were estimated using confocal images. PV-IR was detected in amacrine cells in the inner nuclear layer and in displaced amacrine cells from the ganglion cell layer, and alphaPKC-IR was detected in ON-bipolar cells. The MeHg-treated group (6 microg/g) showed significant reduction of the ON-bipolar alphaPKC-IR cell density (mean density = 1306 +/- 393 cells/mm2) compared to control (1886 +/- 892 cells/mm2; P < 0.001). The mean densities found for amacrine PV-IR cells in MeHg-treated retinas were 1040 +/- 56 cells/mm2 (2 microg/g) and 845 +/- 82 cells/mm2 (6 microg/g), also lower than control (1312 +/- 31 cells/mm2; P < 0.05), differently from the data observed in displaced PV-IR amacrine cells. These results show that MeHg changed the PV-IR amacrine cell density in a dose-dependent way, and reduced the density of alphaKC-IR bipolar cells at the dose of 6 microg/g. Further studies are needed to identify the physiological impact of these findings on visual function.

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

Fish are abundant and important dietary items for the Amer-Indians, and total hair-Hg (HHg) concentration is a reliable marker of fish consumption. We studied the impact of fish consumption (HHg) on the nutritional status of Indian children of Eastern Amazonia. Weight-for-height Z score (WHZ) was measured, and HHg was determined in 203 children younger than 10 years of age in three villages. There was significantly higher fish consumption in Kayabi children (16.55 microg Hg/g; SD, 11.44) than in children of the Munduruku villages of Missão-Cururu (4.76 microg Hg/g; SD, 2.09) and Kaburua (2.87 microg Hg/g; SD, 2.13). Anthropometric indices showed WHZ means of -0.27, -0.22, and 0.40, respectively, for Kayabi, Missão-Cururu and Kaburua villages. Despite a different pattern of fish-protein consumption between tribes, there was no significant correlation between WHZ and HHg concentrations (r2 = 0.0079; P < 0.2021). Dietary differences among Amazonian tribes can be traced and used in measuring health outcomes. Higher fish consumption, although important for Kayabis, was compensated by other protein sources by the Kaburua villagers.

Mercury in lakes and lake fishes on a conservation-industry gradient in Brazil

Mercury contamination in freshwater food webs can be severe and persistent, and freshwater fish are a major source of mercury contamination in humans. Northern hemisphere studies suggest that the primary pathway by which freshwater fish accumulate mercury is the food web, and that atmospheric deposition is the primary route by which mercury enters freshwater systems. Levels of atmospheric deposition are closely linked to proximity to sources of mercury emissions. These propositions have not been tested in the southern hemisphere. In this study, we measured mercury levels at three lakes in southern Brazil and assessed relationships between mercury in precipitation, lake water, sediment and fish tissues at sites close to (industrial and suburban areas) and distant from (protected conservation area) sources of mercury emissions. We also assessed relationships between mercury in fish species and their trophic habits. Mercury concentrations in sediment and lake water did not vary among lakes. In contrast, mercury in precipitation at the study lakes increased with proximity to industrial sources. Mercury in fish tissue generally increased along the same gradient, but also varied with trophic level and preferred depth zone. Atmospheric mercury deposition to these closed lakes may be directly linked to concentrations in fish, with surface-feeding piscivorous species attaining the highest concentrations.

Hair mercury (signature of fish consumption) and cardiovascular risk in Munduruku and Kayabi Indians of Amazonia

Fish is an important natural resource in the diet of inhabitants of the Amazon rain forest and a marker of its consumption (hair Hg) was used to compare selected cardiovascular risk parameters between tribes of Eastern Amazonia. Three Munduruku (Terra Preta, Kaburua, Cururu) villages and one Kayabi village at the banks of head rivers (Tapajos, Tropas, Kabitutu, Cururu, Curuzinho, Teles Pires) of the Tapajos Basin were studied in relation to fish Hg concentrations, mercury in hair (fish consumption) and erythrocytes, body mass index (height/weight, kg/cm2), and blood pressure. The mean fish Hg concentrations were higher in predatory (578.6 ng/g) than in nonpredatory species (52.8 ng/g). Overall only 26% of fish Hg concentrations were above 500 ng/g, and only 11% were above 1000 ng/g. There was no systematic trend in fish Hg concentrations from rivers with a history of gold-mining activities. The biomarker of fish consumption (hair Hg) was significantly associated with erythrocyte-Hg (r=0.5181; P=0.0001) and was significantly higher in Kayabi (12.7 microg/g) than in the Munduruku (3.4 microg/g). Biomarker-assessed fish consumption rate was higher in the Kayabi (110 g/day) than in the Munduruku villages (30 g/day). Although no significant differences in body mass index (BMI) were observed between tribes, there was a trend of lower increase in blood pressure with age among the higher fish consumers (Kayabi). Summary clinical evaluation did not detect neurologic complaints compatible with Hg intoxication (paraparesis, numbness, tremor, balancing failure), but endemic tropical diseases such as clinical history of malaria showed a high prevalence (55.4%). Fish is an abundant natural resource, important in the Indian diet, that has been historically consumed without perceived problems and can easily be traced through hair Hg. The exposure to freshwater fish monomethyl mercury is less of an issue than endemic infectious diseases such as malaria and lack of basic medical services.

Piranhas (Serrasalmus spp.) as markers of mercury bioaccumulation in Amazonian ecosystems

Mercury (Hg) concentration in fish depends on feeding strategies and age/size within the species as well as on water parameters related to acidity and Hg speciation. We chose two species of piranhas (Serrasalmus aff. eigenmanni and Serrasalmus rhombeus) to test their suitability as markers of Hg bioaccumulation. The results of Hg concentrations in piranhas of the Rio Negro, with no history of gold-mining activity, are similar to other Amazonian rivers with intensive gold mining. An increase in water Hg associated with low pH favored higher mean Hg concentrations in the two species. S. rhombeus in this habitat showed a consistently higher Hg concentration than S. eigenmanni. This result was attributed to fish size because of differences in correlation coefficient between S. rhombeus (r = 0.4443; P < 0.0001) and S. eigenmanni (r = 0.1520; P = 0.0135). Matching for fish weight resulted in comparable ranges of Hg concentrations between the two species.

Fish are central in the diet of Amazonian riparians: should we worry about their mercury concentrations?

The Amazon rain forest extends over an area of 7.8x10(6)km(2) in nine countries. It harbors a diverse human population distributed in dense cities and isolated communities with extreme levels of infrastructure. Amazonian forest people, either autochthons or frontier riparians (ribeirinhos) living in isolated areas, share the same environment for survival and nutritional status. The peculiarities of the hydrological cycle determine disease patterns, agricultural conditions, and food availability. Feeding strategies depend heavily on cassava products and fish. These two foods carry toxic substances such as linamarin (naturally present in cassava) and monomethyl mercury (MMHg) (bioconcentrated in fish flesh) that cause neurotoxic diseases in other parts of the world but not in Amazonia, where neurotoxic cases of food origin are rare and not related to these staples. While cassava detoxification processes may partly explain its safe consumption, the Hg concentrations in Amazonian fish are within traditionally safe limits for this population and contribute to an important metabolic interaction with cassava. The gold rush of the 1970s and 1980s brought large-scale environmental disruption and physical destruction of ecosystems at impact points, along with a heavy discharge of metallic Hg. The discharged Hg has not yet impacted on MMHg concentrations in fish or in hair of fish consumers. Hair Hg concentration, used as a biomarker of fish consumption, indicates that the Amazonian riparians are acquiring an excellent source of protein carrying important nutrients, the lack of which could aggravate their existing health problems. Therefore, in a scenario of insufficient health services and an unhealthy environment, food habits based on fish consumption are part of a successful survival strategy and recommendations for changes are not yet justifiable.

Exposição ao mercúrio e ao arsênio em Estados da Amazônia: síntese dos estudos do Instituto Evandro Chagas/FUNASA

Este artigo é uma revisão das pesquisas da Seção de Meio Ambiente do Instituto Evandro Chagas/FUNASA sobre exposição ao mercúrio (Hg) no vale do rio Tapajós e Estado do Acre, e exposição ao arsênio (As) através de resíduos da exploração de manganês (Mn) realizada pela ICOMI deixados no Porto de Santana-AP. Em relação ao mercúrio, têm sido pesquisadas populações sob risco através da via respiratória ou alimentar. No primeiro caso, os trabalhadores de casas de compra e venda de ouro têm apresentado teores mais elevados de Hg em urina do que os garimpeiros estudados. No segundo caso, as populações ribeirinhas têm mostrado níveis diferenciados de exposição (Hg em cabelo). Comunidades ribeirinhas situadas em áreas não afetadas pelo mercúrio da garimpagem e com hábitos alimentares semelhantes às de área de risco têm sido avaliadas, visando a construção de parâmetros de normalidade regional. São também pesquisados os teores de Hg em materiais ambientais e na biota aquática. Os estudos de saúde humana e ambiente na cidade de Santana-AP objetivaram avaliar as fontes e possíveis vias de exposição da população da comunidade do Elesbão ao arsênio. Verificou-se a existência de fonte de risco através dos rejeitos de Mn, porém os níveis de As na água consumida pela população mostraram-se dentro dos parâmetros de normalidade. As médias encontradas em sangue e cabelo coincidem com médias de normalidade referidas na literatura, em populações não expostas, e as associações entre variáveis epidemiológicas, avaliação clínico-laboratorial e os teores de arsênio não mostraram significância estatística.

Mercury exposure in Munduruku Indians from the community of Sai Cinza, State of Pará, Brazil

The objective of this cross-sectional study was to evaluate mercury exposure and health status among Munduruku Indians from the community of Sai Cinza, State of Pará, Brazil. The population studied included 330 indians, who submitted to a questionnaire, clinical exams, and collection of hair, blood, urine, and feces. Mercury was measured in hair and fish. Although no person was found to have overt mercury intoxication, the mean levels of mercury in hair were elevated (14.45 micrograms/g for children from 7 to 12 years old, 15.70 micrograms/g for women between 14 and 44 years old, and 14.1 micrograms/g for the remaining population). Mercury levels in fish were below levels recommended by the World Health Organization, but rates of fish consumption were high. These results place this indigenous populations as a group under risk of mercury toxicity from the gold production.

Assessment of mercury exposure and malaria in a Brazilian Amazon riverine community

Small-scale gold mining in the Brazilian Amazon occurs in areas with high rates of malaria transmission. Amazonian populations can be exposed to mercury through direct contact with the mining process and/or through fish consumption. Because of data from experimental studies, we examined the potential for mercury to affect host response to malaria. A cross-sectional survey was done in Jacareacanga, a riverine community in Para state, in a region of intense alluvial gold mining. A sample of 205 persons was selected by cluster sampling from the total population of approximately 2000. A brief medical history and exam were conducted, malaria slides were obtained, and hair samples were taken to measure mercury levels. The average hair mercury level was 8.6 micrograms/g, ranging from 0.3 to 83.2 micrograms/g. The most important predictors of elevated mercury levels were high fish consumption and low income. Although there was no prevalent malaria, the odds of reporting a past malaria infection was four times higher for those also reporting a history of working with mercury.