Lactobacillus strains reduce the toxic effects of a subchronic exposure to arsenite through drinking water

The aim of the present study was to determine the efficacy of LAB strains in reducing the intestinal toxicity of arsenite [As(III)] and its tissue accumulation. For this purpose, Balb/c mice were randomly separated in four groups. One group received no treatment (control), one group received only As(III) (30 mg/L) via drinking water and the remaining two groups received As(III) via water and a daily dose of two LAB strains (Lactobacillus intestinalis LE1 and Lacticaseibacillus paracasei BL23) by gavage during 2 months. The results show that both strains reduce the pro-inflammatory and pro-oxidant response observed at the colonic level, partially restore the expression of the intercellular junction proteins (CLDN3 and OCLN) responsible for the maintenance of epithelial integrity, and increase the synthesis of the major mucin of the colonic mucus layer (MUC2), compared to animals treated with As(III) alone. Microbial metabolism of short-chain fatty acids also undergoes a recovery and the levels of fatty acids in the lumen reach values similar to those of untreated animals. All these positive effects imply the restoration of mucosal permeability, and a reduction of the marker of endotoxemia LPS binding protein (LBP). Treatment with the bacteria also has a direct impact on intestinal absorption, reducing the accumulation of As in the internal organs. The data suggest that the protective effect may be due to a reduced internalization of As(III) in intestinal tissues and to a possible antioxidant and anti-inflammatory activity of the bacteria through activation of pathways such as Nrf2 and IL-10. In vitro tests show that the protection may be the result of the combined action of structural and metabolic components of the LAB strains.

Intestinal homeostasis disruption in mice chronically exposed to arsenite-contaminated drinking water

Chronic exposure to inorganic arsenic [As(III) and As(V)] affects about 200 million people, and is linked to a greater incidence of certain types of cancer. Drinking water is the main route of exposure, so, in endemic areas, the intestinal mucosa is constantly exposed to the metalloid. However, studies on the intestinal toxicity of inorganic As are scarce. The objective of this study was to evaluate the toxicity of a chronic exposure to As(III) on the intestinal mucosa and its associated microbiota. For this purpose, BALB/c mice were exposed during 6 months through drinking water to As(III) (15 and 30 mg/L). Treatment with As(III) increased reactive oxygen species (43-64%) and lipid peroxidation (8-51%). A pro-inflammatory response was also observed, evidenced by an increase in fecal lactoferrin (23-29%) and mucosal neutrophil infiltration. As(III) also induced an increase in the colonic levels of pro-inflammatory cytokines (24-201%) and the activation of some pro-inflammatory signaling pathways. Reductions in the number of goblet cells and mucus production were also observed. Moreover, As(III) exposure resulted in changes in gut microbial alpha diversity but no differences in beta diversity. This suggested that the abundance of some taxa was significantly affected by As(III), although the composition of the population did not show significant alterations. Analysis of differential taxa agreed with this, 21 ASVs were affected in abundance or variability, especially ASVs from the family Muribaculaceae. Intestinal microbiota metabolism was also affected, as reductions in fecal concentration of short-chain fatty acids were observed. The effects observed on different components of the intestinal barrier may be responsible of the increased permeability in As(III) treated mice, evidenced by an increase in fecal albumin (48-66%). Moreover, serum levels of Lipopolysaccharide binding proteins and TNF-α were increased in animals treated with 30 mg/L of As(III), suggesting a low-level systemic inflammation.

Lipoteichoic acid depletion in Lactobacillus impacts cell morphology and stress response but does not abolish mercury surface binding

Lipoteichoic acid (LTA) is a key component of the cell wall of most Gram-positive bacteria and plays many structural and functional roles. In probiotic lactobacilli, the function of LTA in mediating bacteria/host cross-talk has been evidenced and it has been postulated that, owing to its anionic nature, LTA may play a role in toxic metal sequestration by these bacteria. However, studies on this last aspect employing strains unable to synthesise LTA are lacking. We have inactivated the LTA polymerase encoding gene ltaS in two different Lactobacillus plantarum strains. Analysis of LTA contents in wild-type and ltaS mutant strains corroborated the role of this gene as a major contributor to LTA synthesis in L. plantarum. The mutant strains displayed strain-dependent anomalous cell morphologies that resulted in elongated or irregular cells with aberrant septum formation. They also exhibited higher sensitivity to several stresses (osmotic and heat) and to antimicrobials that target the cell wall. The toxicity of inorganic [(Hg(II)] and organic mercury (methyl-Hg) was also increased upon ltaS mutation in a strain-dependent manner. However, the mutant strains showed 0 to 50% decrease in their capacity of Hg binding compared to their corresponding parental strains. This result suggests a partial contribution of LTA to Hg binding onto the cell surface that was dependent on the strain and the Hg form.

In Vitro Reduction of Arsenic Bioavailability Using Dietary Strategies

The main route of human exposure to inorganic arsenic (As) is through the consumption of food and water. Continued exposure to inorganic As [As(III) and As(V)] may cause a variety of diseases, including various types of cancer. The removal of As from these sources is complex, especially for food. One way to decrease As exposure could be by reducing intestinal absorption of it. The aim of this study is to seek dietary strategies (pure compounds, extracts, or supplements) that are capable of reducing the amount of As that is absorbed and reaches systemic circulation. Standard solutions of As(III) and As(V) and bioaccessible fractions of food samples with or without the dietary strategies to be tested were added to colon-derived human cells (NCM460 and HT-29MTX) to determine the apparent permeability (P_app) of As. Results show that transport across the intestinal monolayers is substantial, and the passage of As(III) (P_app = 4.2 × 10^-5 cm/s) is greater than that of As(V) (P_app = 2.4 × 10^-5 cm/s). Some of the treatments used (iron species, cysteine, grape extract) significantly reduce the transport of both inorganic As standards across the intestinal monolayer, thus decreasing absorption of them. In food samples, the effect of the dietary compounds on inorganic As bioavailability was also observed, especially in the cases of curcumin and cysteine. Compounds that proved effective in these in vitro assays could be the basis for intervention strategies aimed at reducing As toxicity in chronically exposed populations or regular consumers of food products with high As contents.

Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food: Outcome of the collaborative trial IMEP-41

A collaborative trial was conducted to determine the performance characteristics of an analytical method for the quantification of inorganic arsenic (iAs) in food. The method is based on (i) solubilisation of the protein matrix with concentrated hydrochloric acid to denature proteins and allow the release of all arsenic species into solution, and (ii) subsequent extraction of the inorganic arsenic present in the acid medium using chloroform followed by back-extraction to acidic medium. The final detection and quantification is done by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS). The seven test items used in this exercise were reference materials covering a broad range of matrices: mussels, cabbage, seaweed (hijiki), fish protein, rice, wheat, mushrooms, with concentrations ranging from 0.074 to 7.55mgkg(-1). The relative standard deviation for repeatability (RSDr) ranged from 4.1 to 10.3%, while the relative standard deviation for reproducibility (RSDR) ranged from 6.1 to 22.8%.

Gastrointestinal stromal tumor of the stomach and hepatocellular carcinoma: An unusual association

INTRODUCTION

Gastrointestinal stromal tumors (GIST) are uncommon, potentially malignant tumors, that arise in the wall of the gastrointestinal tract. Up to 50% can develop metastasis, mainly in the liver, but the occurrence of synchronous primary liver tumors is a rare event in these patients.

PRESENTATION OF CASE

The authors report a case of the association of gastric GIST and hepatocellular carcinoma (HCC) in a non-cirrhotic liver in a 76 year-old patient.

DISCUSSION

The appearance of an hepatic lesion in a GIST patient does not necessarily imply its secondary nature.

CONCLUSION

In diagnosed GIST patients, all efforts should be pursued to characterize synchronous hepatic lesions, in order to plan a correct and tailored treatment of the patients.

Participation of b0,+and B0,+systems in the transport of mercury bound to cysteine in intestinal cells

The main source of exposure to mercury (Hg) as divalent inorganic Hg [Hg(ii)] and methylmercury (CH₃Hg) is the diet, in which complexes with the amino acid cysteine (Hg–Cys) may be found.

Determination of total cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms: outcome of IMEP-116 and IMEP-39

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the International Measurement Evaluation Program (IMEP). IMEP organises inter-laboratory comparisons in support of European Union policies. This paper presents the results of two proficiency tests (PTs): IMEP-116 and IMEP-39, organised for the determination of total Cd, Pb, As, Hg and inorganic As (iAs) in mushrooms. Participation in IMEP-116 was restricted to National Reference Laboratories (NRLs) officially appointed by national authorities in European Union member states. IMEP-39 was open to all other laboratories wishing to participate. Thirty-seven participants from 25 countries reported results in IMEP-116, and 62 laboratories from 36 countries reported for the IMEP-39 study. Both PTs were organised in support to Regulation (EC) No. 1881/2006, which sets the maximum levels for certain contaminants in food. The test item used in both PTs was a blend of mushrooms of the variety shiitake (Lentinula edodes). Five laboratories, with demonstrated measurement capability in the field, provided results to establish the assigned values (Xref). The standard uncertainties associated to the assigned values (uref) were calculated by combining the uncertainty of the characterisation (uchar) with a contribution for homogeneity (ubb) and for stability (ust), whilst uchar was calculated following ISO 13528. Laboratory results were rated with z- and zeta (ζ)-scores in accordance with ISO 13528. The standard deviation for proficiency assessment, σp, ranged from 10% to 20% depending on the analyte. The percentage of satisfactory z-scores ranged from 81% (iAs) to 97% (total Cd) in IMEP-116 and from 64% (iAs) to 84% (total Hg) in IMEP-39.

Evaluation of a joint distractor to facilitate arthroscopy of the hip joint in dogs

OBJECTIVE

To evaluate the technical feasibility and efficacy of a hip joint distraction technique, any potential ligamentous damage linked to the procedure, and the effect of joint venting on the maximum distraction achieved.

METHODS

Twenty hip joints from 11 canine cadavers were evaluated radiographically by standard and stressed projections. Joint distraction was applied with loads from 40 up to 200 N, in 40 N increments, and fluoroscopic images were obtained at each load. At 200 N, a needle was inserted into the joint to achieve a venting effect, and the space was measured again. Standard and stressed radiographs were performed to evaluate potential laxity changes.

RESULTS

Distraction caused a significant increase in joint space at each load of distraction, although there were some variations. Joint venting produced a significant increase in joint space. A statistically significant difference in joint laxity evaluated radiographically before and after the procedure was recorded.

CLINICAL SIGNIFICANCE

Use of the distraction apparatus resulted in an increase in joint space. This could be useful for clinical situations where a larger joint space is required such as for arthroscopic procedures. However, loads in excess of 200 N may induce significant increases in joint laxity.

Characterization of the intestinal absorption of inorganic mercury in Caco-2 cells

The main form of mercury exposure in the general population is through food. Intestinal absorption is therefore a key step in the penetration of mercury into the systemic circulation, and should be considered when evaluating exposure risk. Many studies have investigated the transport of mercury species in different cell lines, though the mechanisms underlying their intestinal absorption are not clear. This study evaluates the accumulation and transport of Hg(II), one of the mercury species ingested in food, using Caco-2 cells as intestinal epithelium model with the purpose of clarifying the mechanisms involved in its absorption. Hg(II) shows moderate absorption, and its transport fundamentally takes place via a carrier-mediated transcellular mechanism. The experiments indicate the participation of an energy-dependent transport mechanism. In addition, H(+)- and Na(+)-dependent transport is also observed. These data, together with those obtained from inhibition studies using specific substrates or inhibitors of different transporter families, suggest the participation of divalent cation and amino acid transporters, and even some organic anion transporters, in Hg(II) intestinal transport. An important cellular accumulation of up to 51% is observed - a situation which in view of the toxic nature of this species could affect intestinal mucosal function. This study contributes new information on the mechanisms of transport of Hg(II) at intestinal level, and which may be responsible for penetration of this mercurial form into the systemic circulation.

Evaluation of a joint distractor to facilitate arthroscopy of the tibio-tarsal joint in dogs

OBJECTIVE

To evaluate the technical feasibility, efficacy and potential soft tissue damage of a joint distraction technique to facilitate arthroscopy of the tibio-tarsal joint and to test the effect of joint venting on the maximum distraction achieved.

METHODS

Twenty hocks were preliminarily evaluated radiographically by standard and stressed projections. Joint distraction was applied with loads from 40 N up to 200 N, in 40 N increments, and radiographic images were obtained at each load. The effect of joint venting by an intra-articular needle was evaluated at the maximum load. Standard and stressed radiographs were repeated to evaluate potential laxity changes.

RESULTS

Joint distraction caused a significant increase in the joint space at each load of distraction except for the 40 to 80 N load increase. Joint venting produced a significant increase in the joint space. No increase of joint laxity could be inferred from the postdistraction radiographic evaluation.

CLINICAL SIGNIFICANCE

Hock distraction can be useful to facilitate arthroscopic procedures, increasing the joint space available for intra-articular manoeuvres. Further clinical studies are required to evaluate potential neurovascular complications.

Trivalent arsenic species induce changes in expression and levels of proinflammatory cytokines in intestinal epithelial cells

Chronic arsenic (As) toxicity in humans has been documented in many countries where exposure mostly occurs through drinking water. The As immunotoxic effects have been demonstrated in animal models as well as in humans. The studies of the immunotoxicity of As have centered on organs related to immune response or target organs, with few data being available at intestinal level. The present study has evaluated the changes in the expression and release of cytokines in Caco-2 cells, widely used as an intestinal epithelial model. Differentiated cells were exposed to 1 μM of As(III), 0.1 μM of monomethylarsonous acid [MMA(III)] and 1 μM of dimethylarsinous acid [DMA(III)] during 2, 4, 6 and 24 h. Additionally, the effect of As coexposure with lipopolysaccharide (LPS, 10 ng/mL) has been evaluated. The results show trivalent species to induce increases in the expression and release of the proinflammatory cytokines tumor necrosis factor alpha (TNFα), IL6, IL8 - the magnitude and time of response being different for each As species. The response of greatest magnitude corresponds to DMA(III), followed by As(III), while MMA(III) generates a limited response. Furthermore, the presence of LPS in the co-exposed cells could affect the expression and secretion of cytokines compared with individual exposure to arsenicals, especially for As(III)/LPS and DMA(III)/LPS.

Factors affecting the bioaccessibility of fluoride from seafood products

Fluoride is considered important for health because of its beneficial effect on the prevention of dental caries and on bone development in the child population. However, excessive intake has negative effects. The main pathway for exposure is oral, through consumption of drinking water, and some food products. Therefore its bioaccessibility (quantity of the element solubilized during the digestive process) is a parameter to be considered when estimating the risk/benefit associated with this element. The aim of the present study was to evaluate the influence of the digestion phase, gastrointestinal digestion factors (pH, pepsin and bile salt concentrations) and the presence of cations on the bioaccessibility of fluoride from seafood products. The results show that the solubilization of fluoride takes place entirely during the gastric phase. Its bioaccessibility is strongly influenced by conditions that favor the formation of insoluble complexes of fluoride with other elements present in the matrix. The factors that are most influential in reducing its bioaccessibility are the increase in pH in the gastric phase, the presence of cations, especially in the intestinal phase, and a low concentration of bile salts.

Is it possible to agree on a value for inorganic arsenic in food? The outcome of IMEP-112

Two of the core tasks of the European Union Reference Laboratory for Heavy Metals in Feed and Food (EU-RL-HM) are to provide advice to the Directorate General for Health and Consumers (DG SANCO) on scientific matters and to organise proficiency tests among appointed National Reference Laboratories. This article presents the results of the 12th proficiency test organised by the EU-RL-HM (IMEP-112) that focused on the determination of total and inorganic arsenic in wheat, vegetable food and algae. The test items used in this exercise were: wheat sampled in a field with a high concentration of arsenic in the soil, spinach (SRM 1570a from NIST) and an algae candidate reference material. Participation in this exercise was open to laboratories from all around the world to be able to judge the state of the art of the determination of total and, more in particular, inorganic arsenic in several food commodities. Seventy-four laboratories from 31 countries registered to the exercise; 30 of them were European National Reference Laboratories. The assigned values for IMEP-112 were provided by a group of seven laboratories expert in the field of arsenic speciation analysis in food. Laboratory results were rated with z and ζ scores (zeta scores) in accordance with ISO 13528. Around 85 % of the participants performed satisfactorily for inorganic arsenic in vegetable food and 60 % did for inorganic arsenic in wheat, but only 20 % of the laboratories taking part in the exercise were able to report satisfactory results in the algae test material.

Organoarsenical species contents in cooked seafood

The organoarsenical species arsenobetaine (AB), arsenocholine (AC), tetramethylarsonium ion (TMA+), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) were determined in 64 cooked seafood products (fish, bivalves, squid, crustaceans) included in a Total Diet Study carried out in the Basque Country (Spain). For cooking, various treatments were employed (grilling, roasting, baking, stewing, boiling, steaming, microwaving). The results obtained show that in cooked seafood AB is the major species, followed by DMA and TMA+. AC and MMA are minor species. The results in cooked seafood were compared with the arsenic species contents obtained for the same product raw. After cooking there was an increase in DMA for sardines and bivalves and an increase or appearance of TMA+ for meagrim, anchovy, Atlantic horse mackerel, and sardine. The data provided add to the very scant information available about organoarsenical species contents in cooked seafood.

Heavy metal, total arsenic, and inorganic arsenic contents of algae food products

The total arsenic, inorganic arsenic, lead, cadmium, and mercury contents of 18 algae food products currently on sale in Spain were determined. The suitability of the analytical methodologies for this type of matrix was confirmed by evaluating their analytical characteristics. The concentration ranges found for each contaminant, expressed in milligrams per kilogram of dry weight, were as follows: total arsenic, 2.3-141; inorganic arsenic, 0.15-88; lead, < 0.05-1.33; cadmium, 0.03-1.9; and mercury, 0.004-0.04. There is currently no legislation in Spain regarding contaminants in algae food products, but some of the samples analyzed revealed Cd and inorganic As levels higher than those permitted by legislation in other countries. Given the high concentrations of inorganic As found in Hizikia fusiforme, a daily consumption of 1.7 g of the product would reach the Provisional Tolerable Weekly Intake recommended by the WHO for an average body weight of 68 kg. A more comprehensive study of the contents and toxicological implications of the inorganic As present in the algae food products currently sold in Spain may be necessary, which might then be the basis for the introduction of specific sales restrictions.

Arsenic in cooked seafood products: study on the effect of cooking on total and inorganic arsenic contents

Total and inorganic arsenic contents were analyzed in cooked seafood products consumed in Spain during the period July 1997-June 1998: hake, meagrim, small hake, anchovy, Atlantic horse mackerel, sardine, bivalves, crustaceans, squid, and salted cod. Various cooking treatments were used (grilling, roasting, baking, stewing, boiling, steaming, and microwaving). The results obtained were compared statistically with those found previously in the same products raw, and they showed that after cooking there was a significant increase in the concentration of total arsenic for salted cod and bivalves, and in the concentration of inorganic arsenic for bivalves and squid. The mean content of inorganic arsenic was significantly higher in bivalves than in any other type of seafood. For the Spanish population, the mean intake of total arsenic estimated on the basis of the results obtained in this study is 245 microg/day. The intake of inorganic arsenic (2.3 microg/day) represents 1.7% of the World Health Organization provisional tolerable weekly intake (PTWI), leaving an ample safety margin for this population, which has a very high consumption of seafood.

Effect of cooking temperatures on chemical changes in species of organic arsenic in seafood

The concentrations of arsenobetaine (AB), tetramethylarsonium ion (TMA(+)), and trimethylarsine oxide (TMAO) were determined in samples of sole, dory, hake, and sardine, raw and after being subjected to cooking processes--baking, frying, and grilling--at various temperatures. In all cases, the temperature attained inside the product during the cooking process was measured. The arsenic species extracted from the samples with methanol/water were separated by means of a column switching technique between a PRP-X100 column and a PRP-X200 column. AB was detected by hydride generation atomic absorption spectrometry, whereas TMA(+) and TMAO were detected by hydride generation atomic fluorescence spectrometry. The results obtained showed that, in all of the types of seafood studied, TMA(+) appeared after cooking, possibly because heating facilitates decarboxylation of AB to TMA(+).

Kinetic study of transformations of arsenic species during heat treatment

The combination of temperatures and pH levels applied in domestic or industrial cooking and in the sterilization of seafood might cause the transformation of certain species of arsenic into other more toxic species, which could pose a risk to the consumer. To clarify the effect of the temperatures traditionally used in cooking or sterilization on the stability of the various species of arsenic, a kinetic study was carried out, using standards of arsenobetaine (AB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), trimethylarsine oxide (TMAO), tetramethylarsonium ion (TMA(+)), and arsenocholine (AC) heated at different temperatures (85--190 degrees C) and for different treatment times. Various pH levels (4.5, 5.5, 6.5, and 8.0) were applied during the heating process. The results obtained indicated that there were no transformations of arsenic species after temperature treatments up to 120 degrees C. However, when temperatures between 150 and 190 degrees C were used, a partial decomposition of AB was achieved, producing TMAO at 150 degrees C and TMAO and TMA(+) at temperatures of 160 degrees C or above, in proportions that varied according to the temperature and duration of the heat treatment.

Total and inorganic arsenic in fresh and processed fish products

Total arsenic and inorganic arsenic contents were determined in 153 samples of seafood products consumed in the Basque Country (Spain): fish (white fish and blue fish), mollusks, crustaceans, and preserved fish. White fish presented higher levels of total arsenic and lower levels of inorganic arsenic than the blue fish, indicating possible differences in the metabolization of inorganic arsenic. For total arsenic, 66% of the samples exceeded the maximum permitted level by the strictest international legislation in seafood products [1 microg g(-)(1), wet weight (ww)]. The levels of inorganic arsenic were considerably lower than the maximum authorized in New Zealand (2 microg g(-)(1), ww), the only country with legislation for inorganic arsenic in fish and fish products. It is recommended that legislation based on levels of inorganic arsenic should be established.

Accumulation of heavy metals and As in wetland birds in the area around Doñana National Park affected by the Aznalcollar toxic spill

The impact of the spill from the mine in Aznalcollar (Seville, Spain) on waterfowl in the Doñana National Park is assessed. The concentrations of Cu, Pb, Cd, Zn nd As in the liver and eggs of 16 species of waterfowl found dead in the Park between April and November 1998 were determined. The highest levels were found for Zn, followed by Cu, Pb, Cd and As. The main parameters related to the accumulation of these elements in the waterfowl studied were species and trophic level. The other variables studied--distance from the spill, days of exposure, sex, size, and age--are important, although this depends on the element studied. Zn and Cu from the spill have entered the food chain of the aquatic birds studied, but Cd, Pb and As have not. There is currently no evidence to suggest that the trace element concentrations measured have reached toxic levels.

Trace elements in blood collected from birds feeding in the area around Doñana National Park affected by the toxic spill from the Aznacóllar mine

A long-term monitoring plan was established to study if bird populations around Doñana National Park were affected by the toxic spill from the Aznalcóllar mine. The concentrations of Zn, Pb, As, Cu, Sb, Co, Tl and Cd in the blood of 11 bird species feeding in the area were determined. The parameters which most affect the accumulation of trace elements in the birds studied are, firstly, species and secondly, trophic position, sex, days of exposure and weight. In some individuals, Zn and Cu occurred at higher levels than the reference values for contaminated areas. Concentrations of Pb and Cd in a considerable number of individuals were higher than those found in birds from uncontaminated areas. The present data, together with the lack of data on blood metal concentration prior to the spill, do not offer any conclusive evidence of the influence of the spill on avian blood metal concentrations.

Total and inorganic arsenic in the fauna of the Guadalquivir estuary: environmental and human health implications

To evaluate the impact on fauna of the release of toxic waste from the tailings dam operated by the Boliden Apirsa S.L company at Aznalcóllar, Seville (Spain) a study was carried out of total and inorganic arsenic contents in 164 samples from six different estuary species, including molluscs, crustaceans and fish, collected at six sampling stations distributed along the estuary and mouth of the River Guadalquivir. The contents found, expressed in micrograms per gram wet weight, were as follows. Total arsenic: Crassostrea angulata--giant cupped oyster (2.44 +/- 0.45); Scrobicularia plana--peppery furrow (2.50 +/- 0.73); Palaemon longirostris--delta prawn (1.33 +/- 0.54); Uca tangeri--AfroEuropean fiddler crab (1.76 +/- 0.08); Melicertus kerathurus--shrimp (3.60 +/- 1.92); and Liza ramada--mullet (0.65 +/- 0.38). Inorganic arsenic: C. angulata (0.09 +/- 0.02); S. plana (0.38 +/- 0.23); P. longirostris (0.04 +/- 0.01); U. tangeri (0.22 +/- 0.03); M. kerathurus (0.03 +/- 0.01); and L. ramada (0.03 +/- 0.03). The levels of total As are comparable to those obtained by other authors. With respect to inorganic arsenic, only S. plana and U. tangeri present high levels of inorganic arsenic. This may be due to the fact that these organisms live in estuary sediments, reservoirs of inorganic arsenic, and ingest particles of sediments during feeding. Because of the lack of information for this area concerning previous levels of total and inorganic arsenic in the species analysed, it was not possible to establish the impact on the fauna of the River Guadalquivir estuary of the toxic spill resulting from the failure of the mine tailings dam at Aznalcóllar. With respect to the implications to human health as a result of consumption of species from the Guadalquivir estuary, only with the species Scrobicularia plana, as a high consumption of this mollusc might, in some cases, exceed the maximum tolerable intake for inorganic arsenic indicated by the FAO/WHO. Consumption of the liver of L. ramada does not appear to present problems to human health.