A design of two simple models to predict PCDD/F concentrations in vegetation and soils

The vegetation and soil levels of the 17 polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) toxic congeners were calculated by means of a vegetation and a soil model, respectively. Both models predicted the levels of the 17 PCDD/F congeners in quite good agreement with the observed results although the soil model was more accurate than the vegetation model. Four different pathways of contribution to the vegetation concentrations were taken into account: vapour-phase absorption, dry particle deposition, wet particle deposition and uptake by root. The most important pathway was the vapour-phase absorption and the less was the uptake by root. In the soils model four pathways were considered: background soil concentration, dry particle deposition, wet particle deposition and uptake by root. After the background concentration, the most important pathway was the wet deposition.     

Temporal variation of PCDD/PCDF levels in environmental samples collected near an old municipal waste incinerator

In 1996 and 1997, the levels of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were determined in soil and herbage samples taken from 24 sites in the vicinity of an old municipal solid waste incinerator (Montcada, Barcelona, Spain). To determine the temporal variation in the concentrations of PCDD/Fs, recently 24 soiland 24 herbage samples were again collected at the same sampling points and analyzed for PCDD/F levels. In the currentsurvey, PCDD/F concentrations in soils ranged between 0.06 and127 ng I-TEQ kg^-1 (dry matter), with median and mean values of 4.80 and 9.95 ng I-TEQ kg^-1 (dry matter), respectively. In turn, the levels of PCDD/Fs in herbage samples ranged from 0.40 to 1.94 ng I-TEQ kg^-1 (dry matter), with median and mean values of 0.86 and 0.95 ng I-TEQ kg^-1 (dry matter), respectively. The comparison with the data obtained in 1996 and 1997 show that while PCDD/F concentrations in herbage samples decreased substantially during the last two years, no significant differences in the levels of PCDD/Fs in soils were noted. On the other hand, the potential intake of polluted soils from the vicinity of the plant would not imply any significant health risk for the general population living in the area under influence of the facility.     

Survival and activity of Streptococcus faecalis and Escherichia coli in petroleum-contaminated tropical marine waters

The in situ survival and activity of Streptococcus faecalis and Escherichia coli were studied using membrane diffusion chambers in tropical marine waters receiving oil refinery effluents. Protein synthesis, DNA synthesis, respiration or fermentation, INT reduced per cell, and ATP per cell were used to measure physiological activity. Cell densities decreased significantly over time at both sites for both S. faecalis and E. coli; however, no significant differences in survival pattern were observed between S. faecalis and E. coli. Differences in protein synthesis between the two were only observed at a study site which was not heavily oiled. E. coli was more active in protein synthesis and respiration than S. faecalis at both oiled and unoiled sites, and the percentage of the E. coli population that was respiring was significantly higher than S. faecalis fermenting cells at both sites. However, S. faecalis cells were more active in DNA synthesis and higher in ATP content than E. coli cells at both sites. Although fecal streptococci have been suggested as a better indicator of fecal contamination than fecal coliforms in marine waters, in this study both E. coli and S. faecalis survived and remained physiologically active for extended periods of time. These results suggest that the fecal streptococci group is not a better indicator of fecal contamination in tropical marine waters than the fecal coliform group, especially when that environment is high in long-chained hydrocarbons.     

Dioxin and dibenzofuran concentrations in adipose tissue of a general population from Tarragona, Spain

Polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) levels were determined in adipose tissue of 15 autopsied subjects who at the time of death had lived in the city of Tarragona (Catalonia, Spain) and surroundings during at least the last 10 years. PCDD/F concentrations ranged between 13.37 and 69.37 ng I-TEQ/kg fat, with mean and median values of 30.98 and 26.30 ng I-TEQ/kg fat, respectively. PCDD/F concentrations were higher (p < 0.01) in women (mean value: 44.95 ng I-TEQ/kg fat) than in men (mean value: 24.00 ng I-TEQ/kg fat). Although individuals living in industrial areas showed higher PCDD/F levels than those living Tarragona downtown the difference was not statistically significant. When Principal Component Analysis was applied to the concentrations of PCDD/Fs found in the 15 adipose tissue samples together with those found in 20 blood samples collected in a previous study, a single two-dimensional model was obtained, which would explain 62.9% of the variance in the data. The PCDD/F concentrations in adipose tissue found in the current study are of the same order of magnitude than those reported for most industrialized countries.     

Probabilistic human health risk of PCDD/F exposure: a socioeconomic assessment

The aim of the present study was to assess the human health risks (carcinogenic and non-carcinogenic) of PCDD/F exposure for the adult population living in two different areas (industrial and residential) of Tarragona (Catalonia, Spain), as well as to compare these risks according to the socioeconomic status of the population. Two pathways were considered for PCDD/F exposure: direct (air inhalation, dermal contact and ingestion from soils and dust) and dietary. Although environmental exposure was higher for the population living in the neighborhood of the industrial area (mainly lower socioeconomic group subjects), it only accounted 1.05%. On the other hand, PCDD/F exposure through dietary intake was more important for those individuals of an upper socioeconomic level. This was due to the fact that their diet is richer in those foodstuffs containing higher PCDD/F concentrations. Consequently, taking together direct and dietary exposure to PCDD/Fs, the result is that upper socioeconomic group populations are more exposed to these toxic pollutants. In any case, the current levels of PCDD/F exposure would not mean significant carcinogenic and non-carcinogenic risks for the population living in the industrial and residential areas of Tarragona.     

A fuzzy expert system for soil characterization

As soil is a natural resource not always renewable, the risk characterization of contaminated soils is an issue of great interest. Artificial Intelligence (AI), based on Decision Support Systems (DSSs), has been developed for a wide range of applications in contaminated soil management. Decision trees have already shown to be easy to interpret and able to treat large scale applications. Fuzzy logic gives an improvement in the perturbations and the variance of the training data, due to the elasticity of fuzzy set formalism. In this study, we have developed a classificatory tool applied to characterize contaminated soil in function of human and environmental risks. Knowledge engineering for constructing the Soil Risk Characterization Decision Support System (SRC-DSS) involves three stages: knowledge acquisition, conceptual design and system implementation. A total of 26 parameters were divided into three groups to facilitate the configuration of the expert system: source attributes, transfer vector attributes, and local properties. Sixteen case studies were evaluated with the SRC-DSS. In comparison with other techniques, the results of the current study have shown that SRC-DDS is an excellent tool to classify and characterize soils according to the associated risk.     

Health risks of environmental exposure to metals and herbicides in the Pardo River,Brazil

Mixture of metals and herbicides in rivers may pose relevant risks for the health of surrounding communities. Humans may be exposed to river pollution through intake of contaminated water and fish, as well as irrigated agricultural products. The aim of this study was to assess the human health risks of environmental exposure to metals and herbicides through water and fish intake in the Pardo River. Metals (Al, As, Be, Cd, Cr, Cu, Pb, Mn, Hg, Ni, Tl, Sn, V, and Zn) were analyzed in river water and in edible fish. Herbicides (ametryn, atrazine, diuron, hexazinone, simazine, and tebuthiuron) were analyzed in river water. Seasonal variances were also studied. Aluminum, Cd, Cu, Mn, Pb, and Zn levels in river water were higher than the USEPA benchmarks. Non-carcinogenic risks due to pollutants mixture exposure were above the limit, and carcinogenic risks of As exposure were >10^?6 in the sampling points during the rainy season. Metal levels in fish were lower than the Brazilian legislation and do not pose a threat to public health. Herbicides were detected in four sampling points, with atrazine concentrations (range 0.16–0.32 μg/L) below the Brazilian standard (2.0 μg/L), but above the European Union standard (0.1 μg/L). Considering the water supply needs of cities located in the Pardo River Basin and the persistence of metals and herbicides, the present study indicated that there was a seasonal influence on non-carcinogenic and carcinogenic risks to human health, especially in the rainy season. Studies for water treatment plants implantation should consider the risks of exposure to persistent substances, in order to protect the population.     

Novel approach for assessing heavy metal pollution and ecotoxicological status of rivers by means of passive sampling methods

In order to study the pollution of fluvial ecosystems, it is necessary to analyze not only the levels of chemical contaminants in water, but also those accumulated in the sediment matrix, as well as to assess its ecotoxicological status. Eleven Catalan (Spain) river sections (one sampling point per river) located near urban and industrial areas were sampled during winter of 2009. Water pollutants were collected by using passive samplers as Diffusive Gradient in Thin-Films (DGTs) and Semi-Permeable Membrane Devices (SPMDs). Point water samples were also collected. The concentrations of potentially toxic elements (PTE) in water, filtered water, DGTs and sediment samples were analyzed. Aqueous and organic solvent extracts of sediments samples and organic extracts of SPMDs were performed to assess acute toxicity to Vibrio fischeri by Microtox(?), and chronic toxicity to the green alga Pseudokirschneriella subcapitata. Microtox(?) test was also performed with DGT extracts. The results show that metals content of Catalan river waters are below the freshwater screening US EPA benchmarks, excepting some industrial areas (for Hg, Pb, and Zn). In contrast, sediments levels of some rivers were far above freshwater sediment screening US EPA benchmarks (for Zn, As, Cr, Pb, Ni, Hg, and Mn), particularly in the most industrialized areas. A good correlation was found between toxicity values of extracts (from sediments and DGTs) and PTE levels in sediments. The current results support the suitability of using combined point and passive sampling methods for assessing the chemical and ecotoxicological status of aqueous environments.