Risk assessment of trace elements from consuming local seafood by the population living in the Ebro river basin in Catalonia, Spain

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1 Risk assessment of trace elements from consuming local seafood by the population living in the Ebro river basin in Catalonia, Spain Ferré-Huguet Núria 1, Nadal Martí 1, de la Iglesia Pablo 2,3, Diogène, Jorge 2,3, Domingo José L.*,1 1 Laboratory of Toxicology and Environmental Health, IISPV, Universitat Rovira i Virgili, Sant Llorenç 21, Reus, Catalonia, Spain. 2 IRTA. Crta. de Poble Nou Km 5.5, Sant Carles de la Ràpita, Tarragona, Catalonia, Spain. 3 XRAq, Xarxa de Referència en Aquicultura. Generalitat de Catalunya. *Corresponding author : joseluis.domingo@urv.cat The aim of this study was to investigate the dietary intake and the human health risks associated with metal exposure through local shellfish consumption near a chlor-alkali plant in the Catalan stretch of the Ebro River, Spain. Levels of heavy metals were determined in different shellfish species and their concentrations were generally found to be similar or lower than those recently reported in the literature. Oyster and purple dye murex presented the highest levels of most metals. The current dietary intake is analogous to that recently estimated for the non-exposed population of Catalonia. In general terms, the average exposure of the population to contaminants through local seafood consumption did not exceed the tolerable daily intake levels of the analyzed elements. The only exception was arsenic (As), for which the percentage of the inorganic form (the most toxic) should be determined in detail. Dietary intake was higher in children than in adults. Carcinogenic and non-carcinogenic risks were separately assessed according to age and gender. Metal exposure through local shellfish consumption would only mean a very slight increase of non-carcinogenic and carcinogenic risk for As, whereas the remaining elements showed risk values below the corresponding threshold levels. Consequently, a speciation study is highly recommended in order to determine the true exposure to inorganic As, as well as to obtain reliable values of carcinogenic risk of dietary exposure to metals. Keywords: Metals, local seafood, dietary exposure, human health, risk assessment, Ebro River. Introduction Because of their non-biodegradable nature, long biological half-lives and their potential to accumulate in different parts of the body, heavy metals are very harmful. Contaminants in water can bioaccumulate in fish, and be biomagnified through the food chain (Nadal et al., 2008). Even low concentrations of heavy metals have damaging effects to man and 1

2 animals because there is no good mechanism for their elimination from the body (Arora et al., 2008). The northeast coast of Spain has been subjected to high inputs of anthropogenic contamination over the past decades, mainly contributed by anthropogenic activities and river contamination. The Ebro River basin constitutes an important agricultural area in Catalonia (Spain) and there is a significant shellfish production area in its Delta. In addition to agriculture, other anthropogenic activities can be also found there. Among these, industries and sewage treatment plants are of notable concern, taking into account the potential adverse impacts on local soils. The riparian soil and river pollution in the Catalan basin of the Ebro River, as well as the influence of a chlor-alkali plant located in Flix, has been previously studied by a number of investigators (Ramos et al., 1999; Terrado et al., 2006). This plant was an important source of pollution for the environment in the past, when it was still in operation. Humans are exposed to environmental and dietary metals through various pathways (i.e., inhalation, dermal absorption and ingestion), but diet is the main route of entrance of these contaminants into the human body (Llobet et al., 2003). Shellfish may be an important source of exposure to metals (Domingo, 2007). Because most of these foodstuffs have a local origin, the exposure to these pollutants could pose a risk for the health of the population. The purpose of the present study was to assess the health risks from exposure to metals through the consumption of local shellfish for the population living near the Ebro River in Catalonia, including the Delta. Taking into account the potentially different sensitivities according to the age/gender of the consumers, a risk assessment was carried out for various population groups. 1. Materials and methods 1.1. Sampling and analytical procedure Between 2005 and 2008, a screening study was developed in the Catalan basin of the Ebro River to evaluate the state of pollution of the area as well as the influence of the chloralkali plant on the surrounding environment. Samples of seafood from Delta production areas were acquired in different localities from the riparian zone of the Ebro River in Tarragona Province (9 locations) and its Delta (10 locations) within the monitoring programme of shellfish production areas in the Ebro River Delta (Catalonia). The levels of metals were determined in duplicate on a total of 60 composite samples. Only edible parts of each individual were included in the composite. The following shellfish species and number of composites (comp) were examined: Pacific cupped oyster (Crassostrea gigas; 3 comp), European flat oyster (Ostrea edulis; 3 comp), Manila clam (Ruditapes philipinarum, 4 comp), smooth clam (Callista chione, 3 comp), mussel (Mytilus galloprovincialis L.; 4 comp), grooved carpet shell (Ruditapes decussates; 4 comp), wedge shell (Donax trunculus, 3 comp), Mediterranean striped venus (Chamelea gallina, 3 comp), and purple dye murex (Bolinus brandaris, 3 comp). Composites were made by mixing, shredding, homogenizing and freeze-drying the samples, which were subsequently treated with nitric acid in teflon vessels. Details of the pre-treatment and analytical procedure are already published elsewhere (Linares et al., 2010). Metal analysis was carried out by means of inductively coupled plasma mass spectrometry (ICP-MS, Perkin Elmer Elan 6000). The concentrations of the following elements were determined: arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn). The mean recovery 2

3 rates of metals ranged between 85% and 98%, except Pb whose recovery percentage was 113% 1.2. Human health risk assessment methodology To evaluate the health risks derived from the intake of local foods, four different age and gender groups of population were considered. The daily intake of each metal was calculated and compared with the reference standards (Linares et al., 2010). For the calculations, a Monte Carlo simulation (Crystal Ball 4.0 software), with an iteration size of 10,000, was executed to handle the variability and uncertainty associated with each parameter. Non-carcinogenic risk was assessed using the Hazard Index (HI), a numeric estimate of the systemic toxicity potential posed by all chemicals reaching a receptor through a single exposure route. The use of HI has frequently been used to evaluate the toxicity of chemical mixtures (Roney and Colman, 2004; Huang et al., 2008). The distribution of carcinogenic risk was only estimated for As (Nadal et al., 2008), as this is the only element for which an oral slope factor is derived. 2. Results 2.1. Metal concentrations in seafood The calculated distribution of metal concentration in shellfish, considering all species, as a Log-normal distribution (mean ± standard deviation) is summarized in Table 1. The concentrations of Cd, Hg and Pb were compared with the maximum limits of tolerance (MTL) for metals in foodstuffs recommended by the European Commission for shellfish: 1.0, 0.5 and 1.5 mg/kg for Cd, Hg and Pb, respectively (EC, 2001, 2005, 2006). In all cases, the metal concentrations were below these recommended values. Currently, there are no recommended maximum limits of tolerance in Spain for the other elements studied here. Table 1. Total metal concentrations (in µg g -1 ww) in shellfish (all species), as a log-normal distribution (mean ± standard deviation) As 42.4 ± 25.6 Cu 27.1 ± 22.2 Ni 2.38 ± 0.96 Cd 1.57 ± 1.14 Hg 0.49 ± 0.09 Pb 0.84 ± 0.32 Cr 2.62 ± 0.90 Mn 2.02 ± 0.69 Zn ± Human health risks: non-cancer risks The estimation of the current dietary intake of chemical hazards is essential for the assessment of non-carcinogenic risks, in case there is a relationship between the observed adverse effects in humans and the exposure to a particular contaminant. However, it must be taken into account that only some forms, such as inorganic As or organic Hg (methylmercury, MeHg), are toxic for the human health. In the present study, only total metal concentrations were determined, so speciation data were not available. However, an estimation in a worst-case scenario was obtained by considering percentages of inorganic As and MeHg (11% and 92%, respectively) from the literature (Muñoz et al., 2000). Bearing this in mind, the estimated intake of As, Hg and MeHg would be of concern for the child age group, as intake by this group exceeds the threshold values. Nevertheless, it must be clearly stated that these figures are only a first examination of the state of pollution, and it would be useful to determine the percentage of inorganic As with respect to the total and MeHg in order to obtain an accurate risk assessment. 3

4 The mean total HI values resulting from the dietary intake of local foods were below the safety level of 1.0 in different population groups (Figure 1a). Consequently, food consumption was not found to be a pathway of concern for metals. In any case, the resulting HI was simply the summation of the individual contribution for each metal normalized by number of heavy metals. This is only a preliminary value because potential interactions among chemicals were neglected. Therefore, a new approach is required to estimate the risk from chemical mixtures (USEPA, 1997) (a) (b) Hazard Index distribution M 4-9 F M F M F >65 M >65 F 3.5E-04 As ing = 11% As T As ing = 0.2% As T 3.0E E E E E E E M 4-9 F M F M F > 65 M > 65 F Figure 1. a) Non-carcinogenic risk: Hazard Index (HI) distribution (mean and standard deviation), and b) Cancer risk distribution for As through the consumption. Lower- (As ing=0.2% AsT) and upper- (As ing= 11.0% AsT) bound values. 4-9 M: Children (boys); 4-9 F: Children (girls); M: Male adolescents; F: Female adolescents, M: Male adult; F: Female adults; >65 M: Male seniors; >65 F: Female seniors Human health risks: cancer risks Of the twelve target chemicals, carcinogenicity values were only reported for As. The oral carcinogenic risk (CR) was assessed, and therefore, only As risks were estimated. Although for various age/gender groups, the oral CR of As could be considered of concern according to international standards, it should again be noted that these values were obtained with As being present in all its sources as inorganic As, which is clearly overrated because these levels were estimated in a worst scenario. The risk distribution due to dietary intake of local foodstuffs for children and adults is shown in Figure 1b, considering two different hypotheses: assuming 0.2% and 11% of inorganic vs. total As 4

5 content. Carcinogenic risks were above 10-4 when assuming the maximum percentage of inorganic As (11%), the population group presenting the highest values being the children. 3. Discussion 3.1. Metal concentrations in seafood In general terms, the As, Cd, Cr, and Pb concentrations in shellfish species found in this survey are higher than those reported in other studies previously performed in Catalonia (Falcó et al., 2005; Llobet et al., 2003). For instance, the current As concentrations in mussel were higher than those found by Falcó et al. (2006), who reported As levels of and μg/g fresh weight in mussel and clam, respectively. In the present study, the average total Cd, Hg and Pb concentrations in shellfish were 1.54, 0.70 and 0.84 μg/g fresh weight, respectively; levels higher than those found by Falcó et al. (2006). However, while the metal content was determined in 6 species in the current survey, only 2 (clam and mussel) were analyzed by these investigators. Because data on the specific amount of each seafood species were not available, it is likely that the proportion of the number of composites of each species is not proportional to the food consumption data. This fact would have led to a minor misrepresentation of the total intake of metals. Cephalopods and shellfish have been pointed out as the species showing the greatest accumulation of metals in some Spanish studies on dietary intake (Delgado-Andrade, 2003; Bordajandi et al., 2004), with a special emphasis on As. Recently, the General Directorate of Health and Consumer Protection of the EU published a report to evaluate dietary exposure to As, Cd, Hg and Pb of the population of EU Member States (SCOOP, 2004). In comparison to data from some recent studies performed in France, Germany and United Kingdom, the current dietary intake of metals via seafood is similar to those found here. However, it is worth noting that only 6 seafood species were analyzed here, and dietary exposure was limited to these few, excluding other foodstuffs. Previous investigations have already gathered data regarding the noncarcinogenic and carcinogenic risks derived from the ingestion of fish (Nadal et al., 2008) as well as fruits, vegetables and rice (Ferré-Huguet et al., 2008) for the population living in the Ebro river basin in Catalonia. Moreover, it was estimated that the percentage of metal intake through seafood consumption from all marine species ranged between 0.5% and 56%, depending on the metal and the population group (Nadal et al., 2008) Human health risks The Hazard Index following exposure to non-carcinogenic pollutants, calculated as the sum of HQs, was between 0.08 and 0.25, in boys and female adults, respectively. The mean contribution for As exceeded the safe value of 1 in the child groups (1.6 and 1.2 for boys and girls, respectively). A high variability in the concentrations in the environmental area (e.g., soils, river water, sediments) can contribute to high levels of As in shellfish (Nadal et al., 2008). In addition, the knowledge of the health effects that result from exposure to hazardous chemicals in the diet is difficult because heavy metals are ubiquitous, being in air, water, soils, fuels and marine life (Lee et al., 2006). Similar risk assessment results have been also found in recent investigations for fish from Adriatic Sea (Storelli et al., 2008). In comparison to data from some recent studies in the Ebro River basin, the current HQ are similar to those previously found for shellfish (Nadal et al., 2008). Those authors observed that, in all cases and with the exception of As, the HQ was lower than for fish and shellfish. Contrastingly, the HQ due to As intake 5

6 derived from the consumption of seafood for an adult population living near the Ebro River was slightly higher than 1 in both studies. The total carcinogenic risk derived from the intake of metals greatly exceeded the generally acceptable risk level for individual chemicals of This risk level, basically due to the dietary intake of As through shellfish, would be a cause for concern about human health. However, these relatively high concentrations of As in shellfish would be more similar to As concentrations from the Mediterranean Sea (Muñoz et al., 2000). In turn, when the percentage of inorganic As with respect to total (organic + inorganic) As has been established for the 0.2 % hypothesis (Muñoz et al., 2000), the total carcinogenic risk derived from the intake of metals was very close to the acceptable risk level for individual chemicals of Consequently, it would be advisable to perform a continuous surveillance of this element, as well as to exhaustively monitor the degree of exposure of the population to As. Therefore, an As speciation study would be of great importance in order to establish reliable values of cancer risk. Finally, it is important to note that, since the exposure assessment was based on composite samples of shellfish, only chronic risks, rather than acute risks, were evaluated. In summary, in general terms no significant increases of health risks derived from the consumption of seafood were noted for the population living near the Ebro River in Catalonia. Arsenic would be an exception, since arsenic slightly exceeded the maximum recommended values of non carcinogenic and carcinogenic (As) risks. Therefore, it seems essential to perform a speciation study to establish the amount of inorganic As, and complementarily, of MeHg. The present study is the first of a wide set of investigations to be done in the Ebro River area in Catalonia. Further studies will assess the health risks due to organochlorinated compounds and radionuclides in local foods. Acknowledgments This study was financially supported by the Spanish Ministry of Environment and the Catalan Water Agency (ACA), Generalitat de Catalunya, through the Mobitrof project. References Arora M., Kiran B., Rani S., Rani A., Kaur B., Mittal N., Heavy metal accumulation in vegetables irrigated with water from different sources, Food Chemistry, 111, Bordajandi L.R., Gomez G., Abad E., Rivera J., Fernandez-Baston M.M., Blasco J., Gonzalez M.J., Survey of persistent organochlorine contaminants (PCBs, PCDD/Fs, and PAHs), heavy metals (Cu, Cd, Zn, Pb, and Hg), and arsenic in food samples from Huelva (Spain): Levels and health implications, Journal of Agricultural and Food Chemistry, 52, Delgado-Andrade C., Navarro M., López H., López M.C., Determination of total arsenic levels by hydride generation atomic absorption spectrometry in foods from south-east Spain: estimation of daily dietary intake, Food Additives and Contaminants, 20, Domingo J.L., Bocio A., Martí-Cid R., Llobet J.M., Benefits and risks of fish consumption Part II. RIBEPEIX, a computer program to optimize the balance between the intake of omega-3 fatty acids and chemical contaminants, Toxicology, 230, EC, 2001, Commision Regulation CE466/2001. Maximum levels for certain contaminants in foodstuffs, European Commission, Brussels. EC, 2006, Commision Regulation CE1881/2006. Maximum levels for certain contaminants in foodstuffs, European Commission, Brussels. EC, 2005, Commision Regulation CE 78/2005. Maximum levels for heavy metals in foodstuffs, European Commission, Brussels. Falcó G., Bocio A., Llobet J.M., Domingo J.L., Health risks of dietary intake of environmental pollutants by elite sportsmen and sportswomen, Food and Chemical Toxicology, 43,

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