Lorena Cornejo

One century of arsenic exposure in Latin America: a review of history and occurrence from 14 countries.

The global impact on public health of elevated arsenic (As) in water supplies is highlighted by an increasing number of countries worldwide reporting high As concentrations in drinking water. In Latin America, the problem of As contamination in water is known in 14 out of 20 countries: Argentina, Bolivia, Brazil, Chile, Colombia, Cuba, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Peru and Uruguay. Considering the 10 μg/L limit for As in drinking water established by international and several national agencies, the number of exposed people is estimated to be about 14 million. Health effects of As exposure were identified for the first time already in the 1910s in Bellville (Córdoba province, Argentina). Nevertheless, contamination of As in waters has been detected in 10 Latin American countries only within the last 10 to 15 years. Arsenic is mobilized predominantly from young volcanic rocks and their weathering products. In alluvial aquifers, which are water sources frequently used for water supply, desorption of As from metal oxyhydroxides at high pH (>8) is the predominant mobility control; redox conditions are moderate reducing to oxidizing and As(V) is the predominant species. In the Andes, the Middle American cordillera and the Transmexican Volcanic Belt, oxidation of sulfide minerals is the primary As mobilization process. Rivers that originate in the Andean mountains, transport As to more densely populated areas in the lowlands (e.g. Rímac river in Peru, Pilcomayo river in Bolivia/Argentina/Paraguay). In many parts of Latin America, As often occurs together with F and B; in the Chaco-Pampean plain As is found additionally with V, Mo and U whereas in areas with sulfide ore deposits As often occurs together with heavy metals. These co-occurrences and the anthropogenic activities in mining areas that enhance the mobilization of As and other pollutants make more dramatic the environmental problem.

Arsenic in the human food chain: the Latin American perspective

Many regions of Latin America are widely reported for the occurrence of high arsenic (As) in groundwater and surface water due to a combination of geological processes and/or anthropogenic activities. In this paper, we review the available literature (both in English and Spanish languages) to delineate human As exposure pathways through the food chain. Numerous studies show that As accumulations in edible plants and crops are mainly associated with the presence of high As in soils and irrigation waters. However, factors such as As speciation, type and composition of soil, and plant species have a major control on the amount of As uptake. Areas of high As concentrations in surface water and groundwater show high As accumulations in plants, fish/shellfish, livestock meat, milk and cheese. Such elevated As concentrations in food may result in widespread health risks to local inhabitants, including health of indigenous populations and residents living close to mining industries. Some studies show that As can be transferred from the water to prepared meals, thereby magnifying the As content in the human diet. Arsenic speciation might also change during food preparation, especially during high temperature cooking, such as grilling and frying. Finally, the review of the available literature demonstrates the necessity of more rigorous studies in evaluating pathways of As exposure through the human food chain in Latin America.

Arsenic speciation in human hair: a new perspective for epidemiological assessment in chronic arsenicism

The analysis for arsenic in hair is commonly used in epidemiological studies to assess exposure to this toxic element. However, poor correlation between total arsenic concentration in hair and water sources have been found in previous studies. Exclusive determination of endogenous arsenic in the hair, excluding external contamination has become an analytical challenge. Arsenic speciation in hair appears as a new possibility for analytical assessing in As-exposure studies. This study applied a relative simple method for arsenic speciation in human hair based on water extraction and HPLC-HG-ICP-MS. The concentration of arsenic species in human hair was assessed in chronically As(V)-exposed populations from two villages (Esquiña and Illapata) of the Atacama Desert, Chile. The arsenic concentrations in drinking water are 0.075 and 1.25 mg L(-1), respectively, where As(V) represented between 92 and 99.5% of the total arsenic of the consumed waters. On average, the total arsenic concentrations in hair from individuals of Esquiña and Illapata were 0.7 and 6.1 microg g(-1), respectively. Four arsenic species, As(III), DMA(V), MMA(V) and As(V), were detected and quantified in the hair extracts. Assuming the found species in extracts represent the species in hair, more than 98% of the total arsenic in hair corresponded to inorganic As. On average, As(III) concentrations in hair were 0.25 and 3.75 microg g(-1) in Esquiña and Illapata, respectively; while, the As(V) average concentrations were 0.15 and 0.45 microg g(-1) in Esquiña and Illapata, respectively. Methylated species represent less than 2% of the extracted As (DMA(V)+ MMA(V)) in both populations. As(III) in hair shows the best correlation with chronic exposure to As(V) in comparison to other species and total arsenic. In fact, concentrations of As(total), As(III) and As(V) in hair samples are correlated with the age of the exposed individuals from Illapata (R= 0.65, 0.69, 0.57, respectively) and with the time of residence in this village (R= 0.54, 0.71 and 0.58, respectively).

Emerging mitigation needs and sustainable options for solving the arsenic problems of rural and isolated urban areas in Latin America : A critical analysis

In this work, current information about the contamination of ground- and surface-water resources by arsenic from geogenic sources in Latin America is presented together with possible emerging mitigation solutions. The problem is of the same order of magnitude as other world regions, such as SE Asia, but it is often not described in English. Despite the studies undertaken by numerous local researchers, and the identification of proven treatment methods for the specific water conditions encountered, no technologies have been commercialized due to a current lack of funding and technical assistance. Emerging, low-cost technologies to mitigate the problem of arsenic in drinking water resources that are suitable for rural and urban areas lacking centralized water supplies have been evaluated. The technologies generally use simple and low-cost equipment that can easily be handled and maintained by the local population. Experiences comprise (i) coagulation/filtration with iron and aluminum salts, scaled-down for small community- and household-scale-applications, (ii) adsorption techniques using low-cost arsenic sorbents, such as geological materials (clays, laterites, soils, limestones), natural organic-based sorbents (natural biomass), and synthetic materials. TiO(2)-heterogeneous photocatalysis and zerovalent iron, especially using nanoscale particles, appear to be promising emergent technologies. Another promising innovative method for rural communities is the use of constructed wetlands using native perennial plants for arsenic rhizofiltration. Small-scale simple reverse osmosis equipment (which can be powered by wind or solar energy) that is suitable for small communities can also be utilized. The individual benefits of the different methods have been evaluated in terms of (i) size of the treatment device, (ii) arsenic concentration and distribution of species, chemical composition and grade of mineralization in the raw water, (iii) guidelines for the remaining As concentration, (iv) economical constrains, (v) complexity of installation and maintenance, and infrastructure constraints (e.g. electricity needs).

Arsenic in volcanic geothermal fluids of Latin America

Numerous volcanoes, hot springs, fumaroles, and geothermal wells occur in the Pacific region of Latin America. These systems are characterized by high As concentrations and other typical geothermal elements such as Li and B. This paper presents a review of the available data on As concentrations in geothermal systems and their surficial discharges and As data on volcanic gases of Latin America. Data for geothermal systems in Mexico, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Ecuador, Bolivia, and Chile are presented. Two sources of As can be recognized in the investigated sites: Arsenic partitioned into volcanic gases and emitted in plumes and fumaroles, and arsenic in rocks of volcanic edifices that are leached by groundwaters enriched in volcanic gases. Water containing the most elevated concentrations of As are mature Na-Cl fluids with relatively low sulfate content and As concentrations reaching up to 73.6 mg L⁻¹ (Los Humeros geothermal field in Mexico), but more commonly ranging from a few mg L⁻¹ to tens of mg L⁻¹. Fluids derived from Na-Cl enriched waters formed through evaporation and condensation at shallower depths have As levels of only a few μg L⁻¹. Mixing of Na-Cl waters with shallower meteoric waters results in low to intermediate As concentrations (up to a few mg L⁻¹). After the waters are discharged at the ground surface, As(III) oxidizes to As(V) and attenuation of As concentration can occur due to sorption and co-precipitation processes with iron minerals and organic matter present in sediments. Understanding the mechanisms of As enrichment in geothermal waters and their fate upon mixing with shallower groundwater and surface waters is important for the protection of water resources in Latin America.

In field arsenic removal from natural water by zero-valent iron assisted by solar radiation

An in situ arsenic removal method applicable to highly contaminated water is presented. The method is based in the use of steel wool, lemon juice and solar radiation. The method was evaluated using water from the Camarones River, Atacama Desert in northern Chile, in which the arsenic concentration ranges between 1000 and 1300 microg L(-1). Response surface method analysis was used to optimize the amount of zero-valent iron (steel wool) and the citrate concentration (lemon juice) to be used. The optimal conditions when using solar radiation to remove arsenic from natural water from the Camarones river are: 1.3 g L(-1) of steel wool and one drop (ca. 0.04 mL) of lemon juice. Under these conditions, removal percentages are higher than 99.5% and the final arsenic concentration is below 10 microg L(-1). This highly effective arsenic removal method is easy to use and inexpensive to implement.

Small-scale and household methods to remove arsenic from water for drinking purposes in Latin America.

Small-scale and household low-cost technologies to provide water free of arsenic for drinking purposes, suitable for isolated rural and periurban areas not connected to water networks in Latin America are described. Some of them are merely adaptation of conventional technologies already used at large and medium scale, but others are environmentally friendly emerging procedures that use local materials and resources of the affected zone. The technologies require simple and low-cost equipment that can be easily handled and maintained by the local population. The methods are based on the following processes: combination of coagulation/flocculation with adsorption, adsorption with geological and other low-cost natural materials, electrochemical technologies, biological methods including phytoremediation, use of zerovalent iron and photochemical processes. Examples of relevant research studies and developments in the region are given. In some cases, processes have been tested only at the laboratory level and there is not enough information about the costs. However, it is considered that the presented technologies constitute potential alternatives for arsenic removal in isolated rural and periurban localities of Latin America. Generation, handling and adequate disposal of residues should be taken into account in all cases.

CARACTERIZACIÓN QUÍMICA Y MINERALÓGICA DE LOS MATERIALES GRISES DE LOS CUERPOS CHINCHORRO MODELADOS

En este trabajo se investiga la composicion quimica y mineralogica de los materiales arcillosos grises utilizados por las poblaciones Chinchorro en la creacion de las llamadas Momias Negras (cuerpos modelados). En particular, se analiza y cuantifica si este tipo de material corresponde a arcilla, cual es su composicion mineralogica y cual es su calidad plastica. Para ello se seleccionaron micro-muestras de material gris de relleno de 13 Momias Negras de Arica (ca. 4.000-2.800 a.C.), las que se analizaron en el Laboratorio de Investigaciones Medioambientales de Zonas Aridas, LIMZA (CIHDE-UTA, Universidad de Tarapaca), utilizando Espectrometria de Fluorescencia de Rayos X de Energia Dispersiva (EDXRF) y en el Laboratorio de Ciencias Geologicas de la Universidad del Norte, Antofagasta, mediante Difraccion de Rayos X (DRX) y microscopia electronica de barrido. Ademas se realizaron pruebas de ceramologia experimental en el Laboratorio de Conservacion del Museo Arqueologico, Universidad de Tarapaca, Arica. Los resultados obtenidos por la tecnica EDXRF indican que el material gris esta compuesto principalmente por SiO2 (68%), Al2O3 (13%), Fe2O3 (7%) y, en menor proporcion, K2O (4%), CaO (3%), Cl (2%), SO3 (1%), y TiO2 (1%). Los analisis obtenidos por DRX demostraron que la composicion mineralogica estaba constituida por cuarzo (30%), albita (26%), sanidina (15%) y moscovita (12%), entre otros. Estos resultados, en conjunto con los analisis experimentales ceramologicos y microscopicos, permiten concluir que las poblaciones Chinchorro utilizaban sedimentos naturales que pueden ser considerados como arcillas de buena a mediana calidad plastica para preparar sus Momias Negras y que no le agregaban inclusiones como conchuela o fibras vegetales.

Urinary arsenic speciation profile in ethnic group of the Atacama desert (Chile) exposed to variable arsenic levels in drinking water.

Ethnic groups from the Atacama Desert (known as Atacameños) have been exposed to natural arsenic pollution for over 5000 years. This work presents an integral study that characterizes arsenic species in water used for human consumption. It also describes the metabolism and arsenic elimination through urine in a chronically exposed population in northern Chile. In this region, water contained total arsenic concentrations up to 1250 μg L−1, which was almost exclusively As(V). It is also important that this water was ingested directly from natural water sources without any treatment. The ingested arsenic was extensively methylated. In urine 93% of the arsenic was found as methylated arsenic species, such as monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)]. The original ingested inorganic species [As(V)], represent less than 1% of the total urinary arsenic. Methylation activity among individuals can be assessed by measuring primary [inorganic As/methylated As] and secondary methylation [MMA/DMA] indexes. Both methylation indexes were 0.06, indicating a high biological converting capability of As(V) into MMA and then MMA into DMA, compared with the control population and other arsenic exposed populations previously reported.

ÓXIDOS DE MANGANESO EN EL EXTREMO NORTE DE CHILE: ABASTECIMIENTO, PRODUCCIÓN Y MOVILIDAD DEL COLOR NEGRO DURANTE EL PERÍODO ARCAICO

La utilizacion de oxidos de manganeso se evidencia en el extremo norte de Chile desde el periodo Arcaico (ca. 10.500-4.000 cal. a.p.) en tierras bajas (costa y valles) y tierras altas (precordillera y altiplano). En tierras bajas aparece en contextos de cazadores-recolectores y pescadores Chinchorro, en los procesos de momificacion artificial y en cuerpos momificados de forma natural. En tierras altas se encuentra en aleros ocupados por cazadores-recolectores terrestres altoandinos. Adicionalmente, la informacion geologica existente apunta a que las fuentes de los oxidos de manganeso se encuentran solo en sectores altoandinos. Con toda esta informacion, sumado a nuestros resultados obtenidos a partir de analisis fisico-quimicos de los pigmentos y pinturas de contextos arqueologicos se discute sobre la produccion o cadena operativa del color negro a partir del mineral de manganeso, la criptomelana. Adicionalmente, se proponen alternativas interpretativas en torno al abastecimiento y movilidad de los oxidos de manganeso desarrollados por las sociedades arcaicas de la region.