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Environ Geochem Health (2007) 29:109–118 DOI 10.1007/s10653-006-9074-9

ORIGINAL PAPER

Arsenic occurrence in Brazil and human exposure Bernardino Ribeiro de Figueiredo Æ Ricardo Perobelli Borba Æ Roˆmulo Simo˜es Ange´lica

Published online: 10 March 2007 Ó Springer Science+Business Media B.V. 2007

Abstract Environmental exposure to arsenic (As) in terms of public health is receiving increasing attention worldwide following cases of mass contamination in different parts of the world. However, there is a scarcity of data available on As geochemistry in Brazilian territory, despite the known occurrence of As in some of the more severely polluted areas of Brazil. The purpose of this paper is to discuss existing data on As distribution in Brazil based on recent investigations in three contaminated areas as well as results from the literature. To date, integrated studies on environmental and anthropogenic sources of As contamination have been carried out only in three areas in Brazil: (1) the Southeastern region, known as the B. R. de Figueiredo (&) Instituto de Geocieˆncias, Universidade Estadual de Campinas – UNICAMP, Rua Joa˜o Pandia´ Calo´geras, 51, Caixa Postal 6152, 13083-970 Campinas, SP, Brazil e-mail: [email protected] R. P. Borba Instituto Agronoˆmico de Campinas, Centro de Pesquisa e Desenvolvimento de Solos e Recursos Ambientais – IAC, Avenida Bara˜o de Itapura, 1481, 13001-970 Campinas, SP, Brazil e-mail: [email protected] R. S. Ange´lica Centro de Geocieˆncias, Universidade Federal do Para´ – UFPA, Avenida Augusto Correa, 1, Caixa Postal 1611, 66075-110 Bele´m, Para´, Brazil e-mail: [email protected]

Iron Quadrangle, where As was released into the drainage systems, soils and atmosphere as a result of gold mining; (2) the Ribeira Valley, where As occurs in Pb-Zn mine wastes and naturally in Asrich rocks and soils; (3) the Amazon region, including the Santana area, where As is associated with manganese ores mined over the last 50 years. Toxicological studies revealed that the populations were not exposed to elevated levels of As, with the As concentrations in surface water in these areas rarely exceeding 10 lg/L. Deep weathering of bedrocks along with formation of Fe/Al-enriched soils and sediments function as a chemical barrier that prevents the release of As into the water. In addition, the tropical climate results in high rates of precipitation in the northern and southeastern regions and, hence, the As contents of drinking water is diluted. Severe cases of human As exposure related to non-point pollution sources have not been reported in Brazil. However, increasing awareness of the adverse health effects of As will eventually lead to a more complete picture of the distribution of As in Brazil. Keywords Arsenic
Brazil
Environment
Geochemistry
Human health Introduction Widespread public concern of the risks to human health following environmental exposure to

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arsenic (As) has been increasing recognized following cases of mass contamination being reported in several regions, such as West Bengal, Bangladesh and Mexico, among others. However, there seems to be a relative lack of reference to Brazilian territory in terms of As geochemistry in recent maps and article reviews on this subject (see Mandal & Suzuki, 2002; Smedley & Kinniburgh, 2002). The primary reason for this is the poor history of As geochemistry investigations in Brazil, even in some of the more severely polluted areas of Brazil. To date, integrated studies on environmental and anthropogenic As contamination have been carried out only in three areas of Brazil (Fig. 1): (1) the southeastern region, known as the Iron Quadrangle, where large amounts of As have been released into drainages, soils and the atmosphere as a result of gold mining that has been carried out for the past three centuries; (2) the Ribeira Valley, where minor amounts of As has been released as a byproduct of Pb-Zn mining during the last century and where also an important naturalAs anomaly has been identified downstream of the mining area; (3) the Amazon region, including the Santana area,

Fig. 1 Simplified geological map of Brazil with indications of the studied areas

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where As is associated with manganese ores mined in the last 50 years. The main purpose of this paper was to update the information currently available on As occurrence in Brazil, most of which has been provided by recent integrated environmental and human exposure investigations in three contaminated areas of Brazil. Residents in all three regions volunteered for toxicological studies, including As determinations in urine samples obtained from children and adults residing in five municipalities in the Ribeira Valley and two villages in the Iron Quadrangle. Blood and hair collected from residents in Santana were also analyzed for arsenic. Information was also compiled from other published reports. To date, non-point pollution sources (geologic formations of regional extent), such as the shallow high-As aquifer systems reported elsewhere (Smedley & Kinniburgh, 2002), have not been described in Brazil. On the other hand, the dominant tropical and sub-tropical climate of Brazil seems to favor environmental mitigation and may prevent severe human exposure to As in polluted areas.

Environ Geochem Health (2007) 29:109–118

Materials and methods A brief description is provided of the sampling and analytical procedures used in the three case studies reported herein: the Iron Quadrangle and the Ribeira Valley in the Southeastern region, and the Santana area in the Amazon deltaic region of northern Brazil. The chemical composition of the surface water and stream sediment was determined for different study periods between 1998 and 2003. The surface waters were sampled in at least two different seasons, and chemical physical parameters, such as pH, alkalinity and Eh, were measured in situ. Water analyses were determined on filtered samples (0.45-lm filters; Millipore, Bedford, Mass.), and the As content of these samples was determined by hydride generation-atomic absorption spectroscopy (HG-AAS). The same procedure was followed for other water sources, such as springs, mine drainages and residential tap water. In general, the bulk compositions of waters were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) (major cations) and by ion chromatography (anions) at the Geological Survey of Brazil. Stream sediment and soil samples were airdried, homogenized and subsequently sieved with nylon sieves. The determination of As and other metals was carried out on grains of asize less than 63 lm for sediments and less than 177 lm for soils by X-ray fluorescence (XRF) at UNICAMP (Ribeira Valley and Iron Quadrangle). The As concentrations in the sediments from the Santana area were determined by HG-AAS at the laboratories of the Evandro Chagas Institute (Brazilian Health Ministry). Accuracy was controlled for by simultaneous analyses of certificated reference standards. Urine samples collected from school children and adults in the Ribeira Valley consisted of the first morning void. The urine was analyzed for As concentrations [As3+ + As5+ + monomethylarsonous acid (MMA) + dimethylarsinous acid (DMAA)] by hydride generation coupled with a flow injection system to an atomic absorption spectrophotometer, at the Adolfo Lutz Institute, State of Sa˜o Paulo. Urine analyses were performed according to the procedures recom-

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mended by Guo, Baasner, and Tsalev (1997) using the certified NIST 2670 (0.06 lg/mL As) reference material. The urine samples collected from residents of the Iron Quadrangle were tested for total inorganic As by means of the HG-AAS technique. At the Evandro Chagas Institute, blood and hair collected from the population at Santana, Amapa´ State, were analyzed using a graphite furnace with Zeemann background correction (Lima, 2003; Santos, Jesus, Brabo, Fayal, & Lima, 2003).

Results The three areas investigated have been subject to long-term mining and metal smelter activities. In the Ribeira Valley, however, in addition to these anthropogenic sources, As-rich gold-sulfide veins, altered bedrock and naturally contaminated soils also occur naturally downstream of the mineral province. These were also considered in this study. The following descriptions are based on up-to-date information collected during the last 6 years. Arsenic in the Iron Quadrangle The Iron Quadrangle (State of Minas Gerais, southeastern region; Fig. 2) is the most famous gold-producing area in Brazil, where approximately 600 t of gold have been extracted since colonial times (beginning of the 17th Century). Arsenic is associated with gold mineralization, commonly occurring as arsenopyrite, lo¨llingite and as a trace element in pyrite. World-class gold deposits are hosted in metamorphosed Banded Iron Formation and schist (displaying carbonate hydrothermal alteration) and also in meta-basalts and meta-sedimentary rocks. These terrains of the Archean and Paleoproterozoic ages represent an important As geochemical anomaly in the southern portion of the San Francisco Craton. During the last 300 years, most of the As associated with gold ores, which has been estimated to be 390,000 t (Borba, Figueiredo, Rawllins, & Matchullat, 2000), has been discarded into the drainages, stored in tailing piles on the banks of some rivers and, to a lesser extent, used

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Fig. 2 Location map of the Iron Quadrangle, Minas Gerais State

for industrial arsenic oxide production, near the two largest mines in the area. Oliveira, Ribeiro, Souza Oki, and Barros (1979) and Deschamps et al. (2002) have shown that soils around the Iron Quadrangle gold deposits are enriched with As, which is used as a tracer for gold prospecting in the region. The release of natural As originating from the oxidation of arsenopyrite into water was examined in situ by Borba and Figueiredo (2004) in several underground mines. These researchers observed that, in the presence of carbonate, the higher pH of the aqueous solutions prevents the formation of acidic drainage from arsenopyrite oxidation; on the other hand, it also promotes the simultaneous destabilization of neo-formed Fe, Ca-arsenates, the release of As into water and the partial absorption of As onto iron oxides and hydroxides. As mentioned, the anthropogenic contribution to As pollution in the Iron Quadrangle was significant. The environmental impact on river sediments and surface waters, soils and ground water have been studied in three hydrographic basins where the most important gold mines are located. The results are summarized as the following. Arsenic contents in stream sediments (<63 lm) are at very high levels over the entire region – especially so near gold mines, where up to 4000 mg As/kg sediment may be found. The cation exchangeable fraction was estimated to be

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between 1 and 4%. These sediments contain quartz, kaolinite, goethite and hematite and As, which is preferentially adsorbed onto the iron oxide and hydroxide phases. Filtered (<0.45 lm) surface water samples were collected on different occasions and in different seasons during the period 1998–2001, and the As levels rarely exceeded the threshold of 50 lg/L established by Brazilian regulations for non-treated water at that time1. A few samples collected in the proximity of mines and old tailing piles were found to have higher As contents – up to 350 lg As/L surface water. Groundwater sampling was limited to a very few natural springs and wells, all of which contained very low levels of As in the water. However, the runoff water from some old gold mines in the region had very high As contents, up to 2980 lg Astotal/L, and up to 86 lg As3+/L (Borba, Figueiredo, & Matschullat, 2003). In 1998, a human monitoring campaign was carried out among school children (7–12 years) in two municipalities in the Iron Quadrangle in which As content in the urine was used as a bioindicator (Matschullat et al., 2000). The mean

1

More recently, a new regulation was adopted by CONAMA (National Council for the Environment), Resolution 357 of March 17, 2005, which lowers the total As upper limit in fresh water to 10 lg As/L for some rivers and to 33 lg As/L for others.

Environ Geochem Health (2007) 29:109–118

value of inorganic As content in urine for a population sample of 126 children was 25.7 lg As/ L. Around 20% of this group presented with As levels in the urine of above 40 lg/L, for which adverse health effects cannot be excluded on a long-term basis. The probable route of exposure was contact with contaminated soil and dust as the As content in the domestic water supply did not exceed 10 lg/L (the threshold for potable water according to the Brazilian Ministry of Health regulations). There is no information available, however, on whether those elevated exposure levels were confirmed in subsequent human monitoring campaigns carried out on the same population. Arsenic in the Ribeira Valley The Ribeira Valley is located in southeastern Brazil (Fig. 3), extending for about 500 km from the headwaters of the river in Parana´ State to its mouth on the Atlantic Ocean on the south coast of Sa˜o Paulo State. The region contains the largest remaining portion of the Atlantic Forest (7% of its original area), and important fresh water reservoirs are found in the Ribeira Valley. Arsenic in the rocks, soils, surface water and stream sediments have been studied both in the Upper Valley, where several Pb-Zn mines and a refinery operated during the 20th century, and in the Middle Valley, where a number of As and base metal-bearing gold occurrences, coincident

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with a NE-trending As soil anomaly (Piririca belt) have been mapped in previous geochemical surveys (CPRM, 1982; Perrota, 1996). Modern mining has never been attempted in the Middle Ribeira Valley as the small scale of the gold deposits are not economical. Most of the Pb-Zn ore found in the Upper Valley was produced from lode ore-deposits hosted in dolomitic limestone, which isa widespread occurrence in the mineral province. Galena, sphalerite and pyrite are the major phases in the ores, but pyrrhotite, arsenopyrite and minor tennantite are also present. Decades of mining activities without environmental concern has contributed to severe pollution of river sediments and, to a lesser extent, soils. The levels of As and metals in surface waters have only occasionally exceeded the reference values (according to Brazilian regulations) because the current physical-chemical conditions of the water (pH > 7) do not favor the release of As and heavy metal from contaminated sediments. In the period 1999–2001, a human monitoring campaign was carried out among the population of all municipalities affected by mining and metal refining activities in the Upper Ribeira Valley (Figueiredo et al., 2003). The population of Cerro Azul village, which is located upstream from the mineral district, was chosen as a control or reference group. This campaign included blood analysis for Pb and Cd, and urine analysis for As in children and adults. The results revealed that

Fig. 3 Location map of the Ribeira Valley, Southeastern Brazil

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the inhabitants of two communities near the refinery had been exposed to elevated levels of Pb and to low levels of As (mean contents below 10 lg As/L in urine) and Cd, as reported by Paoliello et al. (2002, 2003) and Cunha (2003). The level of As in theurine is an indicator of recent human exposure to this element. For members of the work force, Brazilian law has established a reference value of 10 lg/g of creatinine and a maximum permitted biological index of 50 lg/g of creatinine. According to international reference values for As and compared to other biomonitoring studies from elsewhere in Brazil (Matschullat et al., 2000), the levels of As in urine found in the Upper Ribeira Valley cannot be considered to be elevated. Despite these results showing low As levels in urine, there were significant differences in terms of As mean values between different population groups. As expected, the lowest values were obtained in the control area Cerro Azul (3.60 lg As/L for children, n = 73; 3.87 lg As/L for adults, n = 83), and the highest As contents in urine were found in the Serra district, Iporanga municipality (8.94 lg As/L for children, n = 89; 8.54 lg As/L for adults, n = 86). The difference in As levels between these groups was proven to be statistically significant, a finding that may be explained by the fact that the population of the Serra District is exposed to an environment contaminated by residues originating from the Pb-Zn-Ag Furnas mine that is in the vicinity. In previous geochemical studies carried out in the Upper Valley, the highest As and Pb contents in stream sediments were found in the Betari river, which runs across the Serra district. Elevated As contents in soils – up to 80 mg As/kg – have been reported in this locality. Downstream of Iporanga town, in the Middle Ribeira Valley, the occurrence of As was investigated in surface water, river sediments and soils. Surface water quality was analysed at ten collection stations in the Ribeira River and tributaries on five different occasions during the period of 2001–2003. Arsenic levels were found in the water that varied from 1 to 9 lg/L. The highest As level was found in Piririca creek, which runs across a gold-sulfide mineralization (Takamori & Figueiredo, 2002). In an earlier study, Toujague (1999)

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reported that the stream sediments of this same creek contained the highest As levels found in the region (355 As mg/kg). As discussed, chemical weathering of bedrock and Au-sulfide veins along the Piririca belt produced soils with high contents of As, Pb and other heavy metals. Arsenic contents ranging from 25 to 764 mg/kg have been reported by Abreu and Figueiredo (2004) in shallow soils (0–30 cm depth) collected in the area. During the period between 2002 and 2003, a population from six communities around the Piririca anomaly volunteered for toxicological studies, which consisted of As determination in urine collected from children and adults. The mean values fell in the interval 2.24–11.35 lg As/L, as shown in Table 1, where the results for the control group (Cerro Azul) and for the Serra district (near the Furnas mine) are included for comparison. Again, the exposure levels of the investigated groups in the Middle Ribeira Valley to As cannot be considered to be elevated. However, the difference between the highest As levels in urine obtained at the Castellanos and Sa˜o Pedro localities and that from the control area in Cerro Azul is statistically significant. Since the communities with higher As levels are located in the Piririca area and the other groups investigated are not, as stated before, the quality of the environment seems to be an important factor determining the level of human exposure to As in the region. Arsenic at Santana, Amapa´ In Amapa´ State, As is related to the arsenopyritebearing manganiferous formation of the Precambrian age. These have been mined for Mn for more than 50 years at the well-known Serra do Navio deposit. Environmental As contamination did not appear at the site of the mine, but rather in Santana municipality, which is about 350 km from the mine, on the Amazonas River, where the As-rich ore was processed and shipped (Fig. 4). Ores and wastes with an As content of as high as 0.17% were disposed of in open air areas, without cover. Groundwater from some of the monitoring wells nearby the ore/waste heaps were found to have extremely high As contents,

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Table 1 Arsenic concentration in urine (lg As/L urine) for different communities (2002–2003) in the Ribeira Valleya Locality

n

Cerro Azul Serra district—Iporanga Iporanga Pilo˜es Castelhanos Sa˜o Pedro Maria Rosa Nhungara Total

156 175

a

Mean Minimum Maximum 3.86 1 8.90 1

34.12 62.54

108 8.35 1 49 4.63 1 54 9.48 1 51 11.35 1 26 2.24 1 22 6.98 1 641

33.49 68.92 60.32 76.19 24.34 36.55

Sources: Sakuma (2004); De Capitani et al. (2005)

as much as 2,000 lg As/L. An extensive geochemical survey has been carried out in this area (Lima, 2003; Santos et al., 2003), which included surface and groundwater samples, stream sediments, soils, ores and wastes. Arsenic concentrations in the surface water was found to range from 5 to 231 lg As/L (2001–2002), but most of the As values fell below 50 or even 10 lg/L (WHO threshold) and they did not exceed 0.5 lg As/L in residential tap water. Up to 1600 and 696 mg As/ kg were found in river sediments and suspended particulate material, respectively. Blood and hair samples were taken from a population of a small community around the mining area (approx. 2000 people) for As analysis. Previous studies had shown that, in general, levels of As in the blood do not correlate well

with As exposure in the drinking water, particularly at low levels. Since inorganic As is very quickly cleared from human blood, this measure is used only as an indicator of very recent and/or relatively high-level exposure (Mandal, Ogra, Anzai, & Suzuki, 2004). These authors, however, suggested that the levels of As in the urine, fingernails and hair are positively correlated with As in the water and that any of these measurements can be considered to be a biomarker for As exposure. Inorganic As has a special affinity for hair and other keratin-rich tissues, and measurements of As levels in these tissues may be a useful indicator of past exposure. According to Choucair and Ajax (1988) and Franzblau and Lilis (1989), As levels of 1 ppm or less in the hair and nails can be considered to be normal levels. This threshold is also assumed by ATSDR (2000). In the Santana area, hair from a total of 512 people supposedly exposed to As contamination were analyzed (Santos et al., 2003). The results yielded a mean value of 0.20 lg As/g, with maximum levels of less than 2 lg As/g (Table 2). These results are in agreement with those of previous studies carried out in other countries (Granero, Lobet, Schuhmacher, Corbella, & Domingo, 1998; Pazirandeh, Brati, & Marageh, 1998; Saad and Hassanien, 2001; among others), in that the As levels in the population studied at the Santana village are suggestive of a low exposure to As. However, it is necessary to obtain complementary data from urine analyses from residents of this area.

Fig. 4 Location map of the Santana area, Amapa´ State, including sampling stations for surface water and sediments

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Other occurrences of As in Brazil Although integrated studies on environmental and human health in terms of As exposure have concentrated in these areas described above, other As pollution point sources can be inferred in other regions in Brazil (Fig. 1). Gold mines have been operational in the Rio Itapicuru greenstone belt (northern Bahia State) and the Crixa´s area (Goia´s State), where the occurrence of As in the gold ores and in the surrounding environment have been found in previous studies. The mining and processing of gold in these areas has not been as intensive as in the Iron Quadrangle, but the impacts of mining and ore processing on the environment may be significant. In southern Brazil, the occurrence of As in association with coal is well known. Large waste basins and sulfur-rich lagoons have been left behind from the coal mining activities that took place in the Santa Catarina and Rio Grande do Sul states. The occurrence of As associated with U-bearing coal formations has been reported at Figueira in the Parana´ State (Licht, 2001). A total of 18,670 arsenic analyses of stream sediments and soils are available in the geochemical data bank of the Geological Survey of Brazil. About 20% of the samples have As levels higher than 100 ppm: sediments and soils in the Ribeira Valley (Piririca belt), in Amapa´ State (around potential gold deposits in granite-greenstone terrains), in the Rio das Velhas greenstone belt (Iron Quadrangle) as well as in areas in the northeastern region and in Rondonia State. A low-density geochemical map showing the distribution of As throughout Parana´ State was produced by Licht (2001), who pointed out a positive As anomaly associated with organic-rich shales and coal formations of the Parana´ Paleozoic basin.

Table 2 Arsenic concentration in haira (lg/g) of residents of Santana, Amapa´ State (2001–2002) Population

n

Mean

Minimum

Maximum

Men Women Total

182 330 512

0.200 0.200 0.200

0.074 0.063 0.063

1.936 1.855 1.936

a

Source: Santos et al. (2003)

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The quality of surface waters in terms of As levels has been examined in other regions of the country. For example, Wilson Scarpelli (personal communication) provided As data for several rivers in the Amazon region, and these results are comparable to those presented here, confirming the very low As content of the surface waters of Brazil. In summary, current knowledge of the distribution of As in Brazil is limited to certain areas, where recent geochemical surveys have been performed for mineral exploration purposes. In the last several decades, additional information on impacted areas with respect to As contamination has been obtained in some mineral provinces (gold, lead-zinc, coal) and, to a lesser extent, in regions where there is intensive pesticide use. Concluding remarks Coincidentally, the world’s most under-developed countries lie in tropical environments (Dissanayake & Chandrajith, 1999). The geochemical environment of such regions is characterized by high rainfall rates and extreme leaching of some major and trace elements, including those that play an important role as essential nutrients for soils and plants. Other elements, such as iron and aluminum become residually enriched and the newly formed minerals, including several poor crystalline oxy-hydroxides, usually act as important scavengers for heavy metals or potentially toxic elements that can be taken up in soils and sediments. In Brazil, as expected, exposure to toxic substances usually affects low income and undernourished populations. Although Brazil is one of the regions of the world with the greatest richness in water resources, potable water and sewage pumping stations mainly attend urban areas. Despite this, most rural communities only use surface water for domestic consumption, taking advantage of high precipitation and the abundant fresh water supply in northern and southeastern regions. The Brazilian tropical climate also favors deep weathering of bedrocks, along with formation of iron–aluminum enriched soils and sediments that function as a chemical barrier preventing arsenic release into water.

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As reported here, integrated geochemical and toxicological studies were only carried out in three areas of Brazil. The natural occurrence of arsenic-bearing rocks and soils has been exacerbated by anthropogenic induced processes (gold, base metals and manganese ore extraction) leading to severe contamination of river sediments. However, very low arsenic concentrations were found in surface waters commonly used for human consumption, and in addition, no elevated arsenic levels of human exposure were found in the study areas reported. Smedley and Kinniburgh (2002) concluded that arsenic-bearing geological formations and major aquifers are restricted to certain environments. Up to now, non-point arsenic pollution sources, such as listed by the authors, have not been reported in Brazil. The only situation described in this work that could approach such a concern is the Piririca belt (Ribeira Valley), but the geological context points to very restricted As-rich soils where the vegetation is still preserved. Fortunately, the area is not highly populated and the local people are not dependent on groundwater supply. To date, no cases of adverse health effects or diseases related to arsenic contamination due to drinking water consumption have been found in Brazil. One of the most important targets for further studies are the savanna-like arid to semi-arid areas of northeast Brazil, one of the most underdeveloped areas of the country, where most people depend on underground water resources. In this area, information about the chemical composition of groundwater, including arsenic concentrations, is very limited. Acknowledgements The authors wish to express their gratitude to all colleagues and students that we dealt with during the last years for their major contribution to medical geology studies in Brazil. The anonymous review work of two SEGH referees was deeply appreciated. Research funds were provided by FAPESP (Grant 2002/ 0271-0) and CNPq (The Brazilian National Research Council).

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