International Journal of Health Geographics BioMed Central Review Open Access Hair mercury levels in Amazonian populations: spatial distribution and trends Flavia L Barbieri*1 and Jacques Gardon2 Address: 1IRD - SELADIS, La Paz, Bolivia and 2IRD - HSM, La Paz, Bolivia Email: FlaviaLBarbieri*[email protected]; [email protected] * Corresponding author Published: 21 December 2009 Received: 1 September 2009 Accepted: 21 December 2009 International Journal of Health Geographics 2009, 8:71 doi:10.1186/1476-072X-8-71 This article is available from: http://www.ij-healthgeographics.com/content/8/1/71 © 2009 Barbieri and Gardon; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract 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 μg/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. Page 1 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Background of data in the rest of the Amazonian countries, where Since the Minamata tragedy as well as the Basra incident, there have been a few isolated studies. methylmercury contamination has been a source of con- cern worldwide. There has been extensive work attempt- We aimed to systematize the available data and extract rel- ing to assess the human health impact of mercury evant information regarding hair mercury levels and contamination through fish, seafood or marine mammal observed health effects in Amazonian populations. We consumption, such as the Seychelles and Faroe Islands focused on the spatial distribution trends, in order to birth cohorts and the New Zealand study [1-8]. compare hair mercury levels by river basin and studied population. In the Amazonian aquatic environments, mercury is present in soils, water and food chains from complex Methods sources [9-16]. On one hand, these soils have accumu- We used scientific databases and online libraries such as lated mercury naturally through time [9]. Human activi- PubMed, ISI Web of Knowledge, ScienceDirect, Springer- ties such as deforestation and agricultural land use can Link, SciELO, Horizon, selecting articles with "Mercury, mobilize mercury from soils and vegetation methylmercury, Amazon, hair, human exposure, fish con- [14,15,17,18]. Also, the use of metallic mercury in the sumption" as main keywords. We included the websites gold mining process can contribute to mercury contami- of international public institutions such as the Environ- nation in these areas [10-13,16]. mental Protection Agency (EPA), the Agency for Toxic Substances and Disease Registry (ATSDR), the World According to specific methylation rates, mercury com- Health Organization (WHO) and the Food and Agricul- pounds in certain aquatic environments can be trans- ture Organization (FAO). formed into methylmercury, the most toxic mercury compound. This organic form of mercury is easily assimi- The articles were included in this review if a measure of lated and accumulated into the food chains, with biomag- the hair mercury concentration was presented from the nification along the trophic levels [10]. This is the main general population or a target group of an Amazonian pathway for human exposure via fish consumption. region. We also considered similar basins in Brazil such as the Tocantins River and Guyana Plateau, because of their The most deleterious and studied health effects of methyl- geographic and ecological interfaces with the Amazon mercury are neurological dysfunctions [19-22], especially regions. from in utero exposure [4,19,23-29]. Also, immunotoxic and citotoxic damages have been shown [30-33], as well Exclusion criteria were sample sizes less than 10 people, as cardiovascular deleterious effects [5,34-37]. It was not and the absence of a measure of central tendency (mean, easy to reach a consensus regarding safe values for meth- geometric mean or median). Also, we excluded studies ylmercury exposure [38]. Overall, the tendency through where the hair mercury concentration presented was an time has been to lower the recommended level as much as estimate calculated from the mercury concentration in possible, in order to minimize the health risk [39,40]. fish tissue and the frequency and amount of fish con- Based on in utero neurological development, the Joint sumption. In the cases where we found two or more arti- FAO/WHO Expert Committee on Food Additives sug- cles corresponding to the same study and in the same gested a Benchmark Dose Limit (BMDL) of 14 μg/g of population, we chose one to be represented on the maps. mercury in maternal hair, recommending a daily mercury intake lower than 1.5 μg/kg of body weight [41]. The Envi- We presented the results from all the selected articles in ronmental Protection Agency (EPA) stated the Reference tables, showing author, study sites, sample sizes, hair mer- Dose (RfD) at 0.1 μg/kg/day, expecting no more than 11 cury levels and fish consumption measures when availa- μg/g of mercury in maternal hair [42]. Most researchers ble. The tables were organized by regions and using the have handled for Amazonian populations a BMDL of 10 same continuity given by the maps, starting with studies μg/g of hair mercury [36,43]. from Andean Amazonian countries (Table 1) and French Guyana (Table 2). Brazilian studies are presented in the Amazonian riverside populations, which are amongst the following tables, divided according to the studied popula- highest fish consumers in the world, are exposed to mer- tion or group (Tables 3, 4, 5). The studies conducted in cury because of their alimentary habits. This situation has the Tapajós River basins were presented in independent been widely studied in Brazil and French Guyana since the tables, also separated according to the studied population late eighties, showing quite complete information about or group (Tables 6, 7, 8, 9). Finally, the studies from the the determinants of mercury exposure in these riverside Madeira River basin were displayed separately in the last populations [38,44-51]. However, there is an evident lack table (Table 10). Page 2 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Table 1: Hair mercury levels in Andean Amazonian Countries Studied population Study N Hg mean μg/g Range > 10 μg/ga Fish Country, River Basin (median) [SD] μg/g General population Barbieri et al. 2009 Cachuela Esperanza 150 3.76 (3.01) [2.52] 0.42-15.65 3% 10.5 meals/week Bolivia, Beni River Monrroy et al. 2008 Upper Beni River 556 5.3 (4.0) [4.3] 0.08-34. ≈ 14.0% Bolivia, Beni River Children 393 5.2 (3.9) [4.4] 0.08-34.1 Mothers 163 5.5 (4.4) [4.1] 0.15-20.0 Pregnant women 18 3.2 (3.3) [2.1] 0.2-7.8 Breastfeeding (BF) 57 6.2 (5.5) [4.1] 0.5-18.3 Non pregnant, non BF 93 5.4 (4.1) [4.1] 0.15-20.0 Maurice-Bourgoin et al. 2000 Rurrenabaque 80 Bolivia, Beni River Esse-Ejjas indigenous 37 9.8 4.3-19.5 Webb et al. 2004 Coca 45 1.9(1.5) 0.03-10.0 7.5 meals/month Ecuador, Napo River Añangu 27 8.7 (7.8) 2.2-20.5 17.2 meals/month Pañacocha 27 5.3 (5.0) 1.5-13.6 33.9 meals/month Children Counter et al. 2005 Nambija gold-mining 80 2.8b (2.0) [17.5] 1.0-135.0 <10% Ecuador, Nambija River settlement aPercentage of the population with hair mercury levels higher than 10 μg/g. bGeometric mean. In the cases when an article studied populations from dif- Results and Discussion ferent river basins, we presented them separately, in the We found 58 articles meeting our criteria for the elabora- corresponding basin tables. tion of the maps. The majority of the studies were carried out in Brazil (86%), while there are only 3 studies in For the design of the maps, we located each Amazonian French Guyana, 3 in Bolivia and 2 in Ecuador (Figures 1, study site using their longitude and latitude data when 2). In Brazil, 30 studies are focused on the Tapajós River available in the article. Otherwise, we searched longitude basin (Figure 3), 10 on the Madeira River basin (Figure 4) and latitude data in geographic databases and using and the remaining 20% of these Brazilian studies are from Google Earth, which allowed us to find and successfully other basins, such as the Negro River, the Tocantins River locate the majority of the study sites. When it was not pos- or the Xingu River (Figure 1). sible to identify the coordinates, we used the maps and/or site descriptions presented by the authors. We marked and The approaches and strategies are quite variable between named each study site on the map displaying a represen- studies. Several studies have used a large sample size, tation of the hair mercury levels found in this population selected randomly from the general population (Tables 1, in a six colour scale. Each individual square on the map 2, 3, 6, 10), and usually comparing two or three sites from represents a hair mercury measure and the target group the same basin. Some of them used smaller sample sizes, used for the study, as well as the reference number. We accepting the variability induced by the sampling fluctua- prepared separated maps for the Madeira River, the Tapa- tion in order to extend to several populations geographi- jós River and French Guiana. We also designed a map cally close to each other. In the Madeira River (Figure 4; illustrating the studies that assessed health outcomes in Table 10), the study by Bastos et al. (2006) covered from relation to hair mercury levels in the studied populations, the upper basin (near the Bolivian border) to a point using a three colour scale for the different results. downstream on the Amazon River [52]. Even if some of the populations had sample sizes of less than 10 people, Page 3 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Table 2: Hair mercury levels in French Guyana Studied River Location N Hg mean μg/g Range μg/g > 10 μg/ga Fish population basin (median) [SD] consumption General population BASAG Maroni Sinnamary 285 1.8 5% 2007 River Oyapok Lower Maroni River 740 1.7-3.6 2.4% River Lower Oyapok 144 1.5-3.4 1 person River 181 4.6-7.2 7.6-18.2% Upper Oyapok River Cordier Maroni 11 health centers et al. 1998 River Oyapok River Adults 255 3.4b 0.2-22.0 12.2% Pregnant women 109 1.6b 0.2-13.0 4.6% Children 136 2.5b 0.2-31.0 11.8 Fréry Maroni Cayodé, Twenké, 235 11.4 [4.2] 1.9-27.2 57.4% 20-317 g/day et al. 2001 River Taluhen and Antécume-Pata Mothers and their infants Cordier Maroni Upper et al. 2002 River Maroni River Oyapok River Children 156 10.2b 79% 2 meals/day Mothers 90 12.7b Oyapok River Children 69 6.5b Mothers 63 6.7b Lower Maroni River Children 153 1.4b Mothers 77 2.8b aPercentage of the population with hair mercury levels higher than 10 μg/g. bGeometric mean. the locations evaluated were 44, distributed along the populations with mercury levels above 10 μg/g were largest part of the Madeira basin (Figure 4). located in an Amerindian reservation in the upper Maroni River basin [47,53,54]. In French Guiana the studies have used both approaches, covering almost the totality of the Maroni and Oyapok In Brazilian Amazonia (Figures 1, 3, 4; Tables 3, 4, 5) hair River basins, with large sample sizes from the general pop- mercury levels are very variable between basins and study ulation (Figure 2; Table 2) [47,53,54]. sites. Without considering the studies from the Tapajós and Madeira Rivers, which will be explained in detail Hair mercury levels in the Amazon below, the highest mercury levels can be found in the In the Andean Amazonian regions (Figure 1; Table 1), Negro River basin [61,62] and at the lakes from the mercury levels were found below 10 μg/g in Ecuador Amapá State (Figure 1; Tables 3, 4, 5) [63], with means [55,56] and Bolivia [57-59]. above 20 μg/g and even higher than 25 μg/g. These high values can also be found in two other sites from the Xingu In French Guiana (Figure 2; Table 2), most study sites and Tocantins Rivers, both from Amerindian reservations showed hair mercury levels below 10 μg/g in the Oyapok (Figure 1) [51,64-68]. These levels can be considered of a River and the lower Maroni River basins [53,60]. The only high risk for the populations and would merit further Page 4 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Table 3: Hair mercury levels in Brazilian River Basins, General Population Study Location N Hg mean μg/g Range μ > 10 μg/ga Fish River Basin (median) [SD] g/g consumption Akagi Três Bocas 11 28.1 8.4-54.0 et al. 1995 Araguari River Castro et al. 1991 Surucucus, 162 3.61 1.4-8.1 Paapiu and Mujacai areas Branco River Forsberg et al. 1995 Various sites 154 75.5 [35.2] 5.8-171.2 between Marie and Paduari Rivers Negro River Kehrig et al. 1998 Balbina Reservoir 53 6.5 [5.4] 1.2-22.0 110 g Negro River Leino & Lodenius 1995 Tucuruí area 125 35.0 (29.0) 0.9-240.0 11 meals/week Tocantins River Pinheiro, Nakanishi Belém 13 2.0 et al. 2000 Tocantins River Santos, Camara Caxiuanã 214 8.6 [6.3] 0.6-46.0 12.3 meals/week et al. 2002 Amazon River Santos Lower Mamoré: 910 8.4 (6.9) [6.4] 0.5-83.9 et al. 2003 Pakaás Novos Indigenous Areas Mamoré River Soares et al. 2002 Doutor Tanajura 13 (6.1) 1.4-11.7 Mamoré River Vasconcellos et al. 1994 Indigenous Xingu Park 27 18.5 (18) [5.9] 6.9-34.0 Xingu River Billings Dam 28 0.9 (0.7) [0.7] 0.3-3.0 Controls 25 1.1 (1.0) [0.6] 0.3-2.5 Vasconcellos Xingu Park 1.2-57.3 et al. 2000 (13 groups) Xingu River Highest values 21.8 (20.8) [6.1] Lowest values 3.6 (2.6) [2.4] The Tapajós and Madeira Rivers basins are not displayed in this table (see Tables 5, 6, 7, 8, 9, 10). aPercentage of the population with hair mercury levels higher than 10 μg/g. investigations about the health impact of this exposure. above 10 μg/g, especially in some populations such as The rest of these study sites show hair mercury levels Rainha, Barreiras, Brasília Legal or São Luís do Tapajós below 10 μg/g, with the exception of an Amerindian res- [34,70-73], where exposure levels seem to be alarming, ervation on the Mamoré River (13.1 μg/g) [69]. even reaching a mean over 30 μg/g in the Apiacás Reserva- tion study [74]. In very few sites the hair mercury levels Tapajós River basin remained below 5 μg/g [75,76]. The populations living in In the Tapajós River basin (Figure 3; Tables 6, 7, 8, 9) there urban or suburban areas (Santarém and Santana do Itu- is a wide difference in mercury levels between the various quí) were used as control populations by the authors and populations. Most locations present hair mercury levels showed lower exposure levels attributed to their food Page 5 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Table 4: Mercury levels in Brazilian River Basins, Target Groups Studied population Location N Hg mean μg/g Range > 10 μg/ga Fish River Basin (median) [SD] μg/g consumption Adults Barbosa Negro River 76 21.4 (17.8) [12.7] 1.7-59.0 79% et al. 2001 shores Negro River Men 17 26.2 [13.7] Women 31 18.3 [11.1] Pinheiro Panacauera 22 ≈ 7.0 et al. 2006 Tocantins Pindobal Grande 43 ≈ 3.0 River Silva Tabatinga 98 (6.4) 1.2-17.0 et al. 2004 Amazon River, lakes Yokoo Pantanal region 129 4.2 (3.7) [2.4] 0.6-13.6 et al. 2003 Cuiabá River Children Barbosa Negro River 73 18.5 (16.4) [10.0] 0.5-45.9 79% et al. 2001 shores Negro River Pinheiro Pindobal Grande 88 ≈ 3.0 et al. 2006 Tocantins River Pinheiro Panacauera 36 2.3 0.4-9.5 0% et al. 2007 Tocantins River Santos-Filho Cubatão 217 0.8 [0.5] 0.2-3.0 0% et al. 1993 Municipality Cubatão River Tavares Barão de Melgaço 114 2.1 (1.8) [1.4] 0.4-7.6 0% 4.6 meals/week et al. 2005 Cuiabá River Riverside 72 5.4 (4.7) [3.4] 0.6-17.1 7.8 meals/week communities Women Pinheiro Panacauera 20 3.3 1.3-6.0 0% et al. 2008 Tocantins River Mothers and their infants Barbosa Garimpo et al. 1998 Maria Bonita Fresco River Mothers 28 8.1 (8.3) [3.2] 0.8-13.7 (Xingu basin) Infants 54 7.3 (6.6) [3.5] 2.0-20.4 The Tapajós and Madeira Rivers basins are not displayed in this table (see Tables 5, 6, 7, 8, 9, 10). aPercentage of the population with hair mercury levels higher than 10 μg/g. Page 6 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 diversification [33,77-79]. In the same way, some authors ner in all the studies. Each research team chose their indi- used study sites from different river basins to compare cators according to their objectives, so this measure can be their exposure levels, such as Panacuera or the city of found in grams per day, percentage of meals composed by Belém (Figure 1) [65,73]. fish, meals per week or per day and/or times per week. No matter which indicator for fish consumption the authors Unexpectedly, studies carried out in the same site and tar- chose, there was always a positive relation between fish get group obtained quite different results. For example, in consumption and hair mercury levels Jacareacanga the studies on the general population pub- [19,46,47,49,64,75,76]. Most of these study sites are usu- lished in 1995 [77,80] showed much higher levels (means ally small and traditional riverside villages, some of them of 16.6 and 25.0 μg/g) than those carried out in the fol- Amerindian reservations, without the proper roads con- lowing decade (mean = 8.6 μg/g and median = 8.0 μg/g) necting them to larger villages and cities. It is possible to [33,81]. The sample sizes and study designs were very dif- hypothesize that this situation makes those populations ferent. In 1995, Jacareacanga was a village with approxi- more dependent on fish as source of protein intake. mately 3000 inhabitants, and the two studies published that year took samples of 10 and 48 people. In 2002, the In spite of those considerations, some populations with population of Jacareacanga was around 2000 inhabitants, high fish consumption showed hair mercury levels below and the studies published in 2002 and 2004 took samples 10 μg/g, even if there was a significant relation with fish of 140 and 205 people. Other than that, there is not consumption frequency [55-57,59,78,79]. In those partic- enough information to explain the observed difference in ular six studies, it is important to consider the different hair mercury levels. There is no evidence of a change in the geographical and socio-economic situation those popula- fish consumption frequency, deforestation, colonization, tions are in: three of those studies were conducted in the agricultural land use or gold mining activities. Andean piedmont Amazonian regions, the two Ecuado- rian studies [55,56] and one of the Bolivian studies [57]. Madeira River basin Also, those populations are not solely dependent on fish In the Madeira River basin (Figure 4; Table 10) most study because they are also farmers or hunters, even if fish sites showed hair mercury levels between 11 μg/g and 15 remains the most important source of nutrients. The μg/g [52,82-85]. A couple of sites (very close to each Bolivian population of Cachuela Esperanza, located near other) presented hair mercury levels above 20 μg/g [52]. A the Brazilian border, consumes large amounts of fish (10 few sites showed levels between 16 μg/g and 20 μg/g and fish meals per week), but only during the dry season, pre- the others presented hair mercury levels under 10 μg/g ferring game meat during the rainy season, which lasts [52,82,83,85]. This shows a mercury exposure distribu- from October to April [57]. tion that appears to be less heterogenic than the Tapajós River basin. The higher mercury levels seem to be found The other two cases with intense fish consumption and in small isolated villages on the middle of the basin, low hair mercury levels are the studies conducted in downstream from Humaitá, near Manicoré (Figure 4). Aldeia do Lago Grande, Santana do Ituquí and Vila to Tabatinga. These communities are located on the Amazon Mercury levels and fish consumption River shore, near the confluence with the Tapajós River. In the Brazilian Amazon, many studies include especially They are small but not isolated because they are connected fish consumption in the population, even though not all by roads to the cities of Monte Alegre, Santarém and of them show these results (Tables 1, 2, 3, 4, 5, 6, 7, 8, 9, Juruti. The low hair mercury levels cannot be explained by 10). Fish consumption is not measured in a uniform man- food diversification, because these populations consume Table 5: Hair mercury levels in Brazilian River Basins, Occupational Groups Study Location N Hg mean μg/g Range > 10 μg/ Fish ga consumption River Basin (median) [SD] Guimarães et al 1999 Pracuúba Lake 15 16.7 Tartarugal Grande River (Fishermen) Duas Bocas Lake 15 28.0 87% 14 meals/week (200 g per day) Groups Palheta & Taylor 1995 Garimpeiros 20 0.4-32. Gurupi River Cachoeira Villagers 5 0.8-4.6 River dwellers 10 0.2-15 The Tapajos and Madeira Rivers basins are not displayed in this table (see Tables 5, 6, 7, 8, 9, 10). aPercentage of the population with hair mercury levels higher than 10 μg/g. Page 7 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Table 6: Hair mercury levels in the Tapajós River Basin, General Population Study Location N Hg mean μg/g Range μg/g > 10 μg/ga Fish (median) [SD] consumption Akagi et al. 1995 Rainha 11 15.8 2.4-31.0 Brasília Legal 56 22.6 3.5-151.0 Ponta de Pedra 10 10.2 6.2-12.6 Jacareacanga 48 16.6 1.5-46.0 Barbosa et al. 1997 Apiacás Reservation 55 34.2 (42.8) ?-128 93% ≈ 6 times/week Crompton et al. 2002 Jacareacanga 205 8.6 0.3-83.2 Dorea et al. 2005 Kaburuá 89 2.5 [1.4] 22 g/day Cururu Mission 138 3.7 [1.6] 32 g/day Terra Preta 22 6.0 [2.9] 52 g/day Kayabi 47 12.8 [7.0] 110 g/day Malm et al. 1995 Jacareacanga 10 25.0 5.7-52.0 Brasília Legal 13-29 26.0 4.7-151.0 Ponta de Pedra 4-26 12.0 Santarem 11 2.7 Pinheiro, Guimarães et al. 2000 Rainha 29 17.2 Barreiras 111 18.9 São Luís do Tapajós 30 25.3 Paranα-Mirim 21 9.2 Pinheiro, Nakanishi et al. 2000 Rainha 29 17.6 Barreiras 78 19.1 Santos et al. 2000 Brasília Legal 220 11.8 [8.0] 0.5-50.0 10 meals/week São Luís do Tapajós 327 19.9 [12.0] 0.1-94.5 13 meals/week Santana do Ituquí 321 4.3 [1.9] 0.4-11.6 13 meals/week Santos, Camara et al 2002 Santana do Ituquí 321 4.3 [2.2] 0.4-12.0 12.7 meals/week Aldeia do Lago Grande 316 4.0 [2.1] 0.4-12.0 12.0 meals/week Vila do Tabatinga 499 5.4 [3.1] 0.4-17.0 10.5 meals/week Santos, de Jesus et al. 2002 Sai Cinza 324 16.0 [18.9] 4,5-90,4 Silva et al. 2004 Jacareacanga 140 (8.0) 0.3-58.5 Rio-Rato 98 0.01-81.4 a Percentage of the population with hair mercury levels higher than 10 μg/g. 10 to 13 fish meals per week. However, the fish they con- Some studies measured mercury concentrations in fish tis- sume is collected from local lakes and minor rivers, and sue, finding positive relations between fish mercury con- the mercury concentrations in fish tissue was found to be centrations, fish consumption and human hair mercury much lower than in other exposed populations levels [13,75,77,80,86]. [52,78,79]. Studied populations On the Madeira River basin, where most hair mercury lev- Due to the importance of mercury exposure and its health els remained under 10 μg/g, the fish consumption in the effects in children, as well as in utero exposure, many stud- majority of the populations was around seven meals per ies have chosen fertile age women and children as target week (Table 10). On the contrary, on the Tapajós River groups (Tables 1, 2, 4, 8, 10). These studies are generally basin the fish consumption in the majority of the popula- consistent with studies on the general population, with tions was higher than 10 meals per week (Table 6). comparable hair mercury levels. When studied together as mother-infant pairs, there was always a strong relation Page 8 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Table 7: Hair mercury levels in the Tapajós River Basin, Adults Study Location N Hg mean μg/g Range μg/ > 10 μg/ Fish (median) [SD] g ga consumption Amorim et al. 2000 Brasília Legal 98 (13.5) 0.6-71.8 >50% Women (10.8) Men (17.1) Dolbec et al. 2000 Cametá 68 10.8 (9.0) [6.1] 61.8% of total meals Women 41 9.9 (8.0) [5.6] >25% Men 27 12.2 (10.8) [6.8] >50% Fillion et al. 2006 São Luís do Tapajós, 251 17.8 0.2-77.2 69.7% 6.8 meals/week Nova Canaã, Santo Antônio, Mussum, Vista Alegre and Açaituba Lebel et al. 1997 Brasília Legal 96 (12.9) >50% Women (11.2) 44.7% of total meals Men (15.7) 43.9% of total meals Lebel et al. 1998 Brasília Legal Men 34 14.3 [9.4] Women 46 12.6 [7.0] Passos et al. 2007 SLTapajós, Nova Canaã, 457 16.8 (15.7) [10.3] 0.2-58.3 >50% 6.6 meals/week Santo Antônio, Ipaupixuna, Novo Paraíso, Teça, Timbu, Açaituba, Campo Alegre, Samauma, Mussum, Vista Alegre and Santa Cruz Pinheiro et al. 2006 São Luís do Tapajós 32 ≈ 15.0 Barreiras 37 ≈ 15.5 Silva et al. 2004 Vila do Tabatinga 98 (6.4) 1.2-17.0 aPercentage of the population with hair mercury levels higher than 10 μg/g. between maternal hair mercury and the exposure in their No study revealed physiological basis that could lead to infants; the mothers always had higher mercury levels hypothesize a difference between female and male mer- than their infants [26,60,82,83,85,87]. cury metabolism. In fact, most studies (78%) did not find any significant relation between mercury exposure and The majority of the studies did not find any significant gender. relationship between age and hair mercury levels [13,30,33,44,48,61,66,77,78,85,88-92]. Some studies A few studies focused their attention on fishermen, found that hair mercury levels increase with age because of their obvious access to fish as main nutrient [74,78,79,81,84]. Nevertheless, a couple of studies found [49,63,70]. Their hair mercury means ranged from 16 to the opposite results, showing higher hair mercury levels in more than 25 μg/g, regardless of the river basin. For younger people, children and infants [58,69]. instance, the studies conducted by Lebel et al. (1997, 1998) compared fishermen and other adults from the Bra- Several studies found that men have higher hair mercury silia Legal population. Both men and women had mer- levels than women [19,30,34,61,65,69,71,74,84,87]. In cury levels lower than 15 μg/g, while fishermen presented two articles from the Tapajós River basin, only the fisher- levels of 27.3 μg/g and 23.9 μg/g (Figure 3; Tables 7, 8) men had hair mercury levels significantly higher than the [20,49]. women, while the other men from the same village pre- sented hair mercury levels similar to those of the women The particular case of gold miners (called garimpeiros in (Tables 7, 8). Those differences corresponded to their fish Brazil and Bolivia) has been documented in a couple of consumption, which was also significantly higher for the studies. It is important to remark that occupational mer- fishermen [20,49]. Only one study found women to have cury exposure is very different from the environmental higher mercury levels than men [69]. exposure. Artisanal garimpeiros are occupationally exposed to metallic mercury vapours, which are rapidly trans- Page 9 of 20 (page number not for citation purposes) International Journal of Health Geographics 2009, 8:71 http://www.ij-healthgeographics.com/content/8/1/71 Table 8: Hair mercury levels in the Tapajós River Basin Women and Children Studied Location N Hg mean μg/g Range μg/g > 10 μg/ga Fish population (median) [SD] consumption Mothers and their Children Grandjean et al. 1999 Mothers 114 11.6 (14.0) Children 11.0 (12.8) 0.5-83.5 2 meals/day Brasilia Legal 76 11.9 0.7-35.8 76% São Luís do Tapajós 71 25.4 0.6-83.5 91% Sai-Cinza 87 17.7 7.3-63.8 92% Santana do Ituquí 105 3.8 0.5-12.4 2% Children Barbosa et al. 1997 Apiacás Reservation 28 29 86% Dorea, Barbosa et al. 2005 Kaburuá 77 2.9 [2.1] Cururu Mission 86 4.8 [2.1] Kayabi 40 16.6 [11.4] Pinheiro et al. 2007 São Luís do Tapajós 48 10.9 1.3-53.8 52% Barreiras 84 6.1 1.4-23.6 21% Women Barbosa et al. 1997 Apiacás Reservation 13 41.2 100% Dolbec et al. 2001 Cametá 98 (12.5) 2.9-27.0 >50% Hacon et al. 2000 Alta Floresta 75 1.12 [1.2] 0,05-8,2 0% 8-20 g/day Passos et al. 2003 Brasília Legal 26 10.0 (9.1) 4.0-20.0 ≈ 50% 8 meals/week Pinheiro et al. 2007 São Luís do Tapajós 5-14 meals/week Rainha, and Barreiras Pregnant 19 8.2 1.5-19.4 37% Non-pregnant 21 9.4 5.2-21.0 28% Pinheiro et al. 2005 São Luís do Tapajós 28 13.7 3.2-30.04 36% Barreiras 39 12.1 3.04-33.4 38% aPercentage of the population with hair mercury levels higher than 10 μg/g. formed in the human body into inorganic mercury, best Amazonian studies. In both the Bolivian study and the measured in urine or plasma, while total hair mercury cor- Colombian study, hair mercury means remained below 6 responds mainly to methylmercury exposure in high fish μg/g, even in the most exposed groups [57,95]. It would eating populations [36,93]. Generally, the authors found be possible to assume that metallic mercury exposure can that garimpeiros had lower hair mercury levels than the acquire significance in hair mercury levels in some specific ribeirinhos [58,94], concluding that because of their better situations of low methylmercury exposure. However, con- economical situation, they were able to diversify their sidering the differences between those studies and food, consuming less fish than the rest of the popula- regions, and without hair mercury speciation, it is not tion[13]. However, in a few studies the garimpeiros or gold possible to reach valid conclusions. miners had higher total mercury levels in hair than the general population, without apparent relation with fish Multidisciplinary studies consumption frequency [45,57,95,96]. Consistently, in Five studies carried out a multidisciplinary approach, those three studies the hair mercury means in the general measuring as well mercury in air, water, sediments, fish population were lower than those found in most central and human samples [13,52,58,63,96]. In those studies, Page 10 of 20 (page number not for citation purposes)