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A study of the transformation of arsenic species by the microflora of the freshwater crayfish Procambarus clarkii was carried out. The study of the degradation of AB (arsenobetaine) was performed in aerobic conditions in two culture media (tryptic soy broth and saline medium) at two temperatures (30 and 8°C). The microflora transformed AB into TMAO (trimethylarsine oxide), DMA (dimethylarsinate), MA (methylarsonate), and an unidentified compound (U1). The quickest transformations were carried out by microflora from hepatopancreas incubated in saline medium at 30 °C. The individualized study of other arsenic species [AC (arsenocholine), TETRA (tetramethylarsonium ion), TMAO, DMA, and MA] was also performed in saline medium. The only transformation observed was of AC into AB. The bacteria possibly responsible for AB degradation were isolated, identified by phenotypic and genotypic methods, and individually assayed for AB transformation. Only isolates allocated to the species Pseudomonas putida were able to metabolize AB.

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.

During the twentieth century, scientific progress took precedence over quality of life. The impressive development of technology, its negative impact on the foodchain, and the ascendancy of productivity and profitability over quality reduced public confidence in thehealthiness of foods. In the present century, however, it is expected that goals connected with Food Safety, adiscipline concerned with the study of toxic substances present in foods, will be a priority in developedcountries. The metals and metalloids present in the earth's crust, soils, water, atmosphere, and biosphere, and consequently in foods, are stable compounds, persisting in the environment, having a slow rate of elimination, accumulating in tissues, and capable of undergoing transformations that increase their toxi-city. Among the metals and metalloids present in foods, lead, cadmium, arsenic, and mercury stand out because of their possible toxicological potential. These four elements can be considered the starelements, and systems of legislation in most countries have established limits that regulate their presence infoods. The criteria of toxicity for metals and metalloids have traditionally been established on the basis of totalcontent. During recent decades, however, it has been shown that their toxicity depends on their atomic ormolecular form. This has led to the need to carry out

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.

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 °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 °C. However, when temperatures between 150 and 190 °C were used, a partial decomposition of AB was achieved, producing TMAO at 150 °C and TMAO and TMA+ at temperatures of 160 °C or above, in proportions that varied according to the temperature and duration of the heat treatment.

A column-switching system between a cation-exchange column (PRP-X200) and an anion-exchange column (PRP-X100) was used for separation of eight arsenic species. The sample was injected on the PRP-X200 column and the species eluted in the void volume of that column [arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and arsenobetaine (AB)] were transferred to the PRP-X100 column and, after separation, were thermo-oxidized on-line and detected by hydride generation (HG) atomic absorption spectrometry (AAS). The species initially retained in the PRP-X200 column were subsequently separated in that column, thermo-oxidized on-line and detected by HG atomic fluorescence spectrometry (AFS). The organoarsenical species present in natural seafood products were extracted with methanol-water and quantified using the proposed method. The analytical features of the method are reported. The highest limit of detection (LOD) for the sample was obtained for AB [3.6 ng g-1, dry mass (dm)], whereas TMAO and DMA gave the lowest LOD (0.9 ng g-1 dm). For all species the methodology developed provides optimum precision, ranging from 1 to 12%, and the recovery percentage was greater than 95% for all species. The method was applied to the following certified reference materials: CRM 627 (Tuna fish tissue, Institute for Reference Materials and Measurements, IRMM), DORM-2 (Dogfish muscle, National Research Council of Canada, NRCC), TORT-2 (Lobster hepatopancreas, NRCC) and NFA-Shrimp and NFA-Plaice (National Food Agency of Denmark). Only CRM 627 is certified for arsenic species (AB and DMA), and the contents obtained for these species were compared with the certified values. The contents of the other arsenic species present in CRM 627 and the species in the other reference materials were compared with the data reported by other authors.

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+.

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 Aznalcollar, 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 Aznalcollar. 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 pro

A long-term monitoring plan was established to study if bird populations around Donana National Park were affected by the toxic spill from the Aznalcollar 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.

The impact of the spill from the mine in Aznalcollar (Seville, Spain) on waterfowl in the Donana National Park is assessed. The concentrations of Cu, Pb, Cd, Zn and 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.