Evaluation of mixture effects in a crude extract of compost using the CALUX bioassay and HPLC fractionation

Potential synergistic interactions between polycyclic aromatic hydrocarbons in a household sewage sludge compost extract were investigated using the Dioxin-Responsive Chemical-Activated Luciferase gene eXpression (DR-CALUX) assay and reverse-phase high-performance liquid chromatography (RP-HPLC) fractionation. The biological activity of the crude extract was measured in vitro using the CALUX assay. The CALUX activity of the extract was as potent as 360-pg CALUX-TEQ (2,3,7,8-TCDD equivalent value) per g sample, this was 70 times above the WHO-TEQ value which was derived from chemical analyses of dioxins/furans and dioxin-like PCBs of the mixture. The CALUX activity pattern of the crude extract and the retention times of 26 polycyclic aromatic compounds (PACs), as determined by RP-HPLC on an octadecylsilica column, suggested that the dioxin-like compounds with the log K(OW) (n-octanol/water partition coefficient) values corresponding to 6.0-7.0 contributed highly to the whole activity. The CALUX activity of the crude extract was three times the sum of the CALUX activities of the RP-HPLC separated fractions. Mixture effects were assessed by co-exposure of each HPLC fraction and 2,3,7,8-TCDD to the cells. The four concentration levels of added 2,3,7,8-TCDD corresponded to the TEQ value in the original compost sample. The experimental CALUX activity was higher than the predicted CALUX activity for some fractions. It was demonstrated that some compounds in the compost sample interacted synergistically with 2,3,7,8-TCDD in terms of dioxin-like activity. This finding points out the necessity for detailed investigation of synergistic effects in environmental samples.     

The effect of suspended particles coated by humic acid on the toxicity of pharmaceuticals, estrogens, and phenolic compounds

The sorption characteristics of 10 organic chemicals, categorized as pharmaceuticals, estrogens and phenols, onto synthetic suspended particle (i.e., alumina) coated with humic acid were investigated according to their octanol-water partition coefficient (K(ow)). Chemical analyses were performed with gas chromatography and mass spectrometry (GC/MS) and high performance liquid chromatography (HPLC). The effects of particles on the toxicity reduction were evaluated using bioassay tests, using Daphnia magna and Vibrio fisheri for phenols and pharmaceuticals, and the human breast cancer cell MCF-7 for estrogens. Sorption studies revealed that 22 and 38% of octylphenol and pentachlorophenol, respectively, were removed by suspended particle, whereas 2,4-dichlorophenol was not removed, which was directly proportional to the logK(ow) value. Similar to the sorption tests, suspended particles significantly reduced the acute toxicities of octylphenol and pentachlorophenol to D. magna and V. fisheri (p<0.01), but there was no significant difference in the toxicity of 2,4-dichlorophenol to D. magna (p=0.8374). Pharmaceuticals, such as ibuprofen, gemfibrozil and tolfenamic acid, showed no discernible sorption to the suspended particle, with the exception of diclofenac, which revealed 11% sorption. For estrogens, such as estrone, 17beta-estradiol and 17alpha-ethynylestradiol, the results indicated no reduction in the sorption test. This may be attributed to the polar interaction by functional groups in sorption between pharmaceuticals and estrogens and suspended particles. In the bioassays, presence of suspended particles did not significantly modify the toxicity of pharmaceuticals (regardless of their K(ow) values) to D. magna, V. fisheri or E-screen.     

In vitro screening for population variability in toxicity of pesticide-containing mixtures

Population-based human in vitro models offer exceptional opportunities for evaluating the potential hazard and mode of action of chemicals, as well as variability in responses to toxic insults among individuals. This study was designed to test the hypothesis that comparative population genomics with efficient in vitro experimental design can be used for evaluation of the potential for hazard, mode of action, and the extent of population variability in responses to chemical mixtures. We selected 146 lymphoblast cell lines from 4 ancestrally and geographically diverse human populations based on the availability of genome sequence and basal RNA-seq data. Cells were exposed to two pesticide mixtures – an environmental surface water sample comprised primarily of organochlorine pesticides and a laboratory-prepared mixture of 36 currently used pesticides – in concentration response and evaluated for cytotoxicity. On average, the two mixtures exhibited a similar range of in vitro cytotoxicity and showed considerable inter-individual variability across screened cell lines. However, when in vitro-to-in vivo extrapolation (IVIVE) coupled with reverse dosimetry was employed to convert the in vitro cytotoxic concentrations to oral equivalent doses and compared to the upper bound of predicted human exposure, we found that a nominally more cytotoxic chlorinated pesticide mixture is expected to have greater margin of safety (more than 5 orders of magnitude) as compared to the current use pesticide mixture (less than 2 orders of magnitude) due primarily to differences in exposure predictions. Multivariate genome-wide association mapping revealed an association between the toxicity of current use pesticide mixture and a polymorphism in rs1947825 in C17orf54. We conclude that a combination of in vitro human population-based cytotoxicity screening followed by dosimetric adjustment and comparative population genomics analyses enables quantitative evaluation of human health hazard from complex environmental mixtures. Additionally, such an approach yields testable hypotheses regarding potential toxicity mechanisms.     

Partitioning of polar and non-polar neutral organic chemicals into human and cow milk

The aim of this work was to develop a predictive model for milk/water partition coefficients of neutral organic compounds. Batch experiments were performed for 119 diverse organic chemicals in human milk and raw and processed cow milk at 37°C. No differences (<0.3 log units) in the partition coefficients of these types of milk were observed. The polyparameter linear free energy relationship model fit the calibration data well (SD=0.22 log units). An experimental validation data set including hormones and hormone active compounds was predicted satisfactorily by the model. An alternative modelling approach based on log K(ow) revealed a poorer performance. The model presented here provides a significant improvement in predicting enrichment of potentially hazardous chemicals in milk. In combination with physiologically based pharmacokinetic modelling this improvement in the estimation of milk/water partitioning coefficients may allow a better risk assessment for a wide range of neutral organic chemicals.     

Modelling the joint effects of a metal and a pesticide on reproduction and toxicokinetics in Lumbricid earthworms

It is important to understand the aetiology of interactive mixtures effects (i.e. synergism and antagonism) if results from known cases are to be extrapolated to untested combinations. The key role of toxicokinetics in determining internal concentrations at target sites means that understanding chemical uptake in mixtures is an essential requirement for mechanistic understanding of interactions. In this paper, a combined approach using mixture toxicity testing, toxicokinetic studies and modelling has been used to address the link between joint toxicity and internal concentration. The study is conducted in Lumbricid earthworms with a binary mixture of a metal (nickel) and an organophosphate insecticide (chlorpyrifos) not a priori expected to show interactive toxicity. As expected from their dissimilar modes of action and detoxification, exposure to combinations of nickel and chlorpyrifos resulted in additive toxicity. Measurement of internal concentrations indicated that both chemicals were rapidly accumulated (within 3 days) to equilibrium. When exposed as a mixture, Ni uptake followed the same pattern as found for the single chemical. This was not the case for chlorpyrifos which showed a faster rate of uptake and elimination and a slightly higher equilibrium concentration in a mixture. That the difference in chlorpyrifos kinetics in the mixture did not result in interactive toxicity highlights the need to assess chemical toxicodynamics as well as toxicokinetics. Measurement of chlorpyrifos-oxon identified the presence of this toxic form but implementation of more complex approaches encompassing toxicogenomics and epigenetics are ultimately needed to resolve the toxicokinetic to toxicodynamic link for these chemicals.     

The synergistic toxicity of the multiple chemical mixtures: Implications for risk assessment in the terrestrial environment

The combined toxicity of five insecticides (chlorpyrifos, avermectin, imidacloprid, λ-cyhalothrin, and phoxim), two herbicides (atrazine and butachlor) and a heavy metal (cadmium) has been examined with the earthworm acute toxicity test. Toxicological interactions of these chemicals in four, five, six, seven, and eight-component mixtures were studied using the combination-index (CI) equation method. In four-component and five-component mixtures, the synergistic effects predominated at lower effect levels, while the patterns of interactions found in six, seven, and eight-component mixtures displayed synergism. The λ-CY + IMI + BUT + ATR + CPF + PHO combination displayed the most strongly synergistic interaction, with CI values ranging from 0.09 to 0.15. The nature of the interaction changes with the effect level and the relevance of synergistic effects increase with the complexity of the mixture. The CI method was compared with the classical models of concentration addition (CA) and independent action (IA) and we found that the CI method could accurately predict the combined toxicity. The predicted synergism resulted from co-existence of the pesticides and the heavy metal especially at low effect levels may have important implications in risk assessment for the real terrestrial environment.     

Correlation of field-measured toxicity with chemical concentration and pollutant availability.

Direct field toxicity tests were performed in two Louisiana waterways, Bayous Trepagnier and St. John, on sediments containing organic/heavy metal mixtures. Our approach involved bioluminescent bacterial toxicity assays (using DeltaTox, which qualitatively identifies polluted areas, and Microtox, which quantifies toxicity). Samples were more completely analyzed in our laboratory using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and gas chromatography/mass spectrometry (GC/MS). Results indicate that lead is the primary toxic metal at the sites examined, though concentrations of metals fluctuate due to spatial variation and the dynamic nature of the waterways. Polycyclic aromatic hydrocarbons (PAHs) are the most abundant group of organics measured and appear to contribute to the overall toxic response. DeltaTox located toxic hotspots where there was an average light loss of 53-100%. Toxicity results from both assays agree but are well correlated with concentration measurements only for certain sediment fractions. Overall, the DeltaTox/Microtox approach appears to be rapid and cost effective for on-site hotspot identification, and may increase understanding of hazards associated with heavy metal and organic contaminants in these waterways.     

Development of a synthetic PCB mixture resembling the average polychlorinated biphenyl profile in Chicago air

Studies of environmental and toxic effects of polychlorinated biphenyls (PCBs) are ideally performed with PCB mixtures reflecting the composition of environmental PCB profiles to mimic actual effects and to account for complex interactions among individual PCB congeners. Unfortunately, only a few laboratory studies employing synthetic PCB mixtures have been reported, in part because of the challenges associated with the preparation of complex PCB mixtures containing many individual PCB congeners. The objective of this study was to develop a PCB mixture that resembles the average PCB profile recorded from 1996 to 2002 at a satellite station of the Integrated Atmospheric Deposition Network located at the Illinois Institute of Technology (IIT) in Chicago, Illinois, using commercial PCB mixtures. Initial simulations, using published Aroclor profiles, showed that a mixture containing 65% Aroclor 1242 and 35% Aroclor 1254 was a good approximation of the target profile. A synthetic Chicago air mixture (CAM) was prepared by mixing the respective Aroclors in this ratio, followed by GC/MS/MS analysis. Comparison of the PCB profile of the synthetic mixture with the target profile suggests that the synthetic PCB mixture is a good approximation of the average IIT Chicago air profiles (similarity coefficient cos θ = 0.82; average relative percent difference = 84%). The synthetic CAM was also a reasonable approximation of the average of 184 PCB profiles analyzed in 2007 at 37 sites throughout Chicago as part of the University of Iowa Superfund Basic Research Program (isbrp), with a cos θ of 0.70 and an average relative percent difference of 118%. While the CAM and the two Chicago air profiles contained primarily di- to pentachlorobiphenyls, higher chlorinated congeners, including congeners with seven or eight chlorine atoms, were underrepresented in the synthetic CAM. The calculated TCDD toxic equivalency quotients of the synthetic CAM (2.7 ng/mg PCB) and the IIT Chicago air profile (1.6 ng/mg PCB) were comparable, but lower by two orders of magnitude than the isbrp Chicago air profile (865 ng/mg PCB) due to surprisingly high PCB 126 levels in Chicago air. In contrast, the calculated neurotoxic equivalency quotients of the CAM (0.33 mg/mg PCB) and the two Chicago air profiles (0.44 and 0.30 mg/mg PCB, respectively) were similar. This study demonstrates the challenges and methods of creating and characterizing synthetic, environmental mixtures of PCBs.     

Radioactivity and heavy metal composition of Nigerian phosphate rocks: possible environmental implications

Phosphate rock samples collected from the Dange Formation within the Sokoto basin were analyzed for trace element constituents using instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRFA) techniques, while natural activity concentrations due to 235U, 232Th, and 40K were determined by gamma-ray spectrometry. The analytical results show that the average concentrations of some toxic elements (As, Sb, Cr, and Zn) in phosphate rocks are not appreciably different from that in agricultural soils. However the U and Th contents are enriched significantly in comparison. The results were used to assess the environmental toxicity of heavy metals and radiation hazard attributable to the direct application of phosphate rock as fertilizer.     

A review of botanical phytochemicals with mosquitocidal potential

Identification of novel effective mosquitocidal compounds is essential to combat increasing resistance rates, concern for the environment and food safety, the unacceptability of many organophosphates and organochlorines and the high cost of synthetic pyrethroids. An increasing number of researchers are reconsidering botanicals containing active phytochemicals in their efforts to address some of these problems. To be highly competitive and effective, the ideal phytochemical should possess a combination of toxic effects and residual capacity. Acute toxicity is required at doses comparable to some commercial synthetic insecticides while chronic or sub-chronic toxicity is required to produce growth inhibition, developmental toxicity and generational effects. In this article, we review the current state of knowledge on larvicidal plant species, extraction processes, growth and reproduction inhibiting phytochemicals, botanical ovicides, synergistic, additive and antagonistic joint action effects of mixtures, residual capacity, effects on non-target organisms, resistance, screening methodologies, and discuss promising advances made in phytochemical research.     

Fate of glutaraldehyde in hospital wastewater and combined effects of glutaraldehyde and surfactants on aquatic organisms

Glutaraldehyde (GA), an aliphatic dialdehyde disinfectant, and surfactants, one of the major components of detergents, are widely used in hospitals in order to eliminate pathogenic organisms causing nosocomial infectious diseases. After their use, disinfectants and surfactants reach the wastewater network together. The discharge of chemical compounds from hospital activities into wastewater is also a well-known problem, causing pollution of water resources and constituting an ecological risk for aquatic organisms. In this study, the chemistry and toxicology of GA and surfactant mixtures were reviewed in order to estimate their fate in aquatic ecosystems. Furthermore, their joint effects on aquatic organisms were experimentally assessed in the laboratory. A simple model of the additive joint action of toxicants was used to determine combined acute toxicity effects on the bacteria luminescence and Daphnia mobility of three mixtures containing GA at 1.5 x EC50 24 h [in mg/L] on Daphnia and anionic, cationic and nonionic surfactants at twice their critical micellar concentration (CMC). The mixture of GA and a cationic surfactant gave an EC50 30 min on Vibrio fischeri of 0.158%, with a concentration of 0.04 mg GA/L and 1.04 mg CTAB/L, which provided an additive action. The interaction between GA and an anionic surfactant on V. fischeri produced an antagonistic joint action with an EC50 30 min of 3.95%, containing 1.06 mg GA/L and 33.2 mg SDS/L. A synergistic action with an EC50 30 min of 8.4% on V. fischeri was observed for the mixture containing GA and a nonionic surfactant. Antagonistic interactions were observed for the joint action between GA and the surfactants studied on Daphnia. The mixture of GA and CTAB was more toxic (EC50 24 h=0.02%) than the two other mixtures (EC50 24 h GA+SDS=6%; EC50 24 h GA+TX 100=10%). This study provides new data on the toxicity of certain hospital pollutants entering the aquatic environment and detected in surface and groundwaters. It is necessary to study the joint effects of GA and surfactant mixtures following chronic and sublethal standard bioassays in order to estimate the contribution of the additive joint action models in assessing the environmental risk of hospital wastewater (HW).     

Effect of K and bentonite additions on Cs-transfer to ryegrass

Bentonite amendments are generally ineffective in reducing the soil-to-plant radiocaesium transfer but have previously been shown that bentonites in the K-form having been subjected to wetting-drying cycles had pronounced radiocaesium binding capacities. We have investigated the effect of wetting-drying (WD) on Radiocaesium Interception Potential (RIP) development in three K-bentonites and K-bentonite soil mixtures, using a variety of procedures: homogenisation of the bentonites with K through dialysis (K(B)), or partial transformation of the bentonite to the K-form in the presence of a solution of K2CO3 (K(L)) or in presence of solid K2CO3 (K(S)). Of the three strategies tested, addition of K2CO3 (solid) at a dose of 2 meq g(-1) clay and adding the K-bentonite mixtures to the soil resulted in the highest RIP increase after 20 WD cycles. The procedure giving the highest RIP yield is the most practical for further applications and was used in a pot experiment under greenhouse condition. When expressing the RIP increase of the soil-bentonite mixtures per unit bentonite added (RIP yield), 28- to 110-fold RIP increases were observed up to a value of approximately 60,000 meq kg(-1) (6 times higher than the RIP for illite). The beneficial effect following K-bentonite application was shown to be dependent both on a sorption enhancement effect (direct RIP effect) and fixation effects (indirect RIP effect). Greenhouse testing proved that the RIP effects observed in greenhouse could be predicted by making use of the sorption data from the laboratory tests. Optimum soil-amendment would be obtained with bentonites with high initial sorption RIP and a high sorption RIP increase when subjected to WD in the presence of potassium. Hypothised Transfer Factor (TF)-reductions of at least 10-fold could result when mixing approximately 1% bentonite, like Otay bentonite (RIP yield 99,000 meq kg(-1) after WD in presence of K if only fine particle size of <1mm considered) with the contaminated ploughing layer.     

Bioaccumulation of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in wild aquatic species from an electronic waste (e-waste) recycling site in South China

Water and several wild aquatic species including Chinese mysterysnail, prawn, fish, and water snake were collected from a reservoir surrounded by several e-waste recycling workshops in South China. The samples were examined to investigate the levels and bioaccumulation extent of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) released from electronic waste (e-waste) which was processed by crude recycling method. Elevated levels of PBDEs [52.7 to 1702 ng/g wet weight (ww)] and PCBs (20.2-25958 ng/g ww) were found in the collected biota species compared to that in the reference samples (13.0-20.5 ng/g ww for PBDEs and 75.4-82.8 ng/g ww for PCBs). log BAF (bioaccumulation factor) ranged from 2.9 to 5.3 for PBDEs and from 1.2 to 8.4 for PCBs, depending on congeners and species. The relationship between log BAFs and log K(OW) (octanol-water partition coefficient) can be adequately described by species-specific parabolic models wherein log BAFs generally increased at log K(OW)<7 then decreased with further increasing log K(OW) both for PBDEs and PCBs. The exceptions were for Chinese mysterysnail and prawn, in which the log BAFs showed a positive linear correlation with log K(OW) for PBDEs. Some PBDE and PCB congeners showed BAF values declining from the general trend predicted by K(OW), largely attributing to metabolism of these congeners in species sampled.     

Measurement of natural radioactivity in building materials in Qena city, Upper Egypt

Building materials cause direct radiation exposure because of their radium, thorium and potassium content. In this paper, samples of commonly used building materials (bricks, cement, gypsum, ceramics, marble, limestone and granite) in Qena city, Upper Egypt have been collected randomly over the city. The samples were tested for their radioactivity contents by using gamma spectroscopic measurements. The results show that the highest mean value of (226)Ra activity is 205+/-83 Bqkg(-1) measured in marble. The corresponding value of (232)Th is 118+/-14 Bqkg(-1) measured in granite. For (40)K this value is (8.7+/-3.9)x10(2) Bqkg(-1) measured in marble. The average concentrations of the three radionuclides in the different building materials are 116+/-54, 64+/-34 and (4.8+/-2.2)x10(2) Bqkg(-1) for (226)Ra, (232)Th and (40)K, respectively. Radium equivalent activities and various hazard indices were also calculated to assess the radiation hazard. The maximum mean of radium equivalent activity Ra(eq) is 436+/-199 Bqkg(-1) calculated in marble. The highest radioactivity level and dose rate in air from these materials were calculated in marble.     

Predictions of in situ solid/liquid distribution of radiocaesium in soils

Previous work has demonstrated that plant uptake of radiocaesium (RCs) is related to the activity concentration of RCs in soil solution, which is linked to the soil/soil solution distribution coefficient, K(D). The solid-liquid distribution of RCs is generally studied in soil suspensions in the laboratory and there are few reported measurements for in situ soil solutions. From a data set of 53 different soils (contaminated with either 134CsCl or 137CsCl) used in pot trials to investigate grass uptake of RCs, we analysed the variation of in situ K(D) with measured soil properties. The soils differed widely in % clay (0.5-58%), organic matter content (1.9-96%) and pH (2.4-7.0, CaCl2). The K(D) varied between 29 and 375,000 L kg-' (median 1460 L kg(-1)). Stepwise multiple regression analysis showed a significant correlation between the log K(D) and pH (p < 0.001), log %clay (p < 0.01) and log exchangeable K (p < 0.001) (overall R2 = 0.70). The in situ K(D) values were further compared to K(D)S predicted using an existing model, which assumes that RCs sorption occurs on specific sites and regular ion-exchange sites on the soil solid phase. Sorption of RCs on specific sites was quantified from the radiocaesium interception potential (RIP) measured for each soil and the soil solution concentrations of K+ and NH4+. The in situ log K(D) correlated well with the predicted K(D) (R2 = 0.85 before plant growth, R2 = 0.83 after plant growth). However, the observations were fivefold to eightfold higher than the predictions, particularly for the mineral soils. We attribute the under-prediction to the long contact times (minimum 4 weeks) between the RCs tracers and our experimental soils relative to the short (24 h) contact times used in RIP measurements. We conclude that our data confirmed the model but that ageing of RCs in soil is a factor that needs to be considered to better predict in situ KD values.     

Combined toxicity of copper and phenol derivatives to Daphnia magna: effect of complexation reaction

The complexation of Cu with phenol was investigated in aqueous solution to find the changes in toxicity toward Daphnia magna in mixtures of copper and phenol derivatives and determine an appropriate prediction model for the toxicity of these mixtures. In the titration experiment, the results showed that phenol played an important role in the remarkable reduction of the Cu(2+) concentration, due to its complexation with Cu, with the subsequent reduction in the toxicity of aqueous mixtures containing both Cu and phenol. As a result, it was clearly demonstrated that Cu-phenol formed a non-toxic complex toward D. magna as the mortality declined, despite the addition of phenol to a fixed Cu concentration. Meanwhile, prediction of the combined toxicity for binary mixtures of Cu and 11 phenol derivatives more accurately followed an independent action model (p = 0.143, df = 124, and t = -1.475 in t-test) than an effect summation model (p approximately 0, df = 134, and t = 7.528 in t-test) due to the dissimilar modes of action and the complexation reactions between Cu and each of the phenolic compounds. Consequently, this study supports the importance of considering complexation reactions in assessing the combined toxicity for the formulation of water quality in mixtures of heavy metals and organic compounds, and in these cases, an independent action model was found to be appropriate.     

Linking high resolution mass spectrometry data with exposure and toxicity forecasts to advance high-throughput environmental monitoring

There is a growing need in the field of exposure science for monitoring methods that rapidly screen environmental media for suspect contaminants. Measurement and analysis platforms, based on high resolution mass spectrometry (HRMS), now exist to meet this need. Here we describe results of a study that links HRMS data with exposure predictions from the U.S. EPA's ExpoCast™ program and in vitro bioassay data from the U.S. interagency Tox21 consortium. Vacuum dust samples were collected from 56 households across the U.S. as part of the American Healthy Homes Survey (AHHS). Sample extracts were analyzed using liquid chromatography time-of-flight mass spectrometry (LC–TOF/MS) with electrospray ionization. On average, approximately 2000 molecular features were identified per sample (based on accurate mass) in negative ion mode, and 3000 in positive ion mode. Exact mass, isotope distribution, and isotope spacing were used to match molecular features with a unique listing of chemical formulas extracted from EPA's Distributed Structure-Searchable Toxicity (DSSTox) database. A total of 978 DSSTox formulas were consistent with the dust LC–TOF/molecular feature data (match score ≥ 90); these formulas mapped to 3228 possible chemicals in the database. Correct assignment of a unique chemical to a given formula required additional validation steps. Each suspect chemical was prioritized for follow-up confirmation using abundance and detection frequency results, along with exposure and bioactivity estimates from ExpoCast and Tox21, respectively. Chemicals with elevated exposure and/or toxicity potential were further examined using a mixture of 100 chemical standards. A total of 33 chemicals were confirmed present in the dust samples by formula and retention time match; nearly half of these do not appear to have been associated with house dust in the published literature. Chemical matches found in at least 10 of the 56 dust samples include Piperine, N,N-Diethyl-m-toluamide (DEET), Triclocarban, Diethyl phthalate (DEP), Propylparaben, Methylparaben, Tris(1,3-dichloro-2-propyl)phosphate (TDCPP), and Nicotine. This study demonstrates a novel suspect screening methodology to prioritize chemicals of interest for subsequent targeted analysis. The methods described here rely on strategic integration of available public resources and should be considered in future non-targeted and suspect screening assessments of environmental and biological media.     

Natural radioactivity in some major rivers of coastal Karnataka on the southwest coast of India

Systematic studies on radiation level and distribution of radionuclides have been carried out in riverine environs of three major rivers of coastal Karnataka, viz. Kali, Sharavathi and Netravathi. The ambient gamma radiation levels along three rivers were measured using a portable plastic scintillometer. Activity concentrations of (226)Ra, (232)Th and (40)K in soil, sediment and rock were measured using a NaI(Tl) gamma-ray spectrometer. In the Kali, Sharavathi and Netravathi riverbanks, the median values of absorbed gamma dose rates in air were found to be 44 nGy h(-1), 35 nGy h(-1) and 57 nGy h(-1), respectively. The highest activity of (226)Ra was found in riverbank soil samples of Sharavathi River. The highest activities of (232)Th and (40)K were found in riverbank soil and sediment samples of Netravathi River. In Kali River, the highest (226)Ra activity was recorded for rock samples. To assess the radiological hazard of natural radioactivity in the samples, absorbed gamma dose rates in air, radium equivalent activity, representative level index, external hazard index and internal hazard index associated with the radionuclides were calculated and compared with internationally recommended values. The representative level index (I(gammar)) values are high in sediment samples of Netravathi River. The radium equivalent activity (Ra(eq)), external hazard index (H(ex)) and internal hazard index (H(in)) values are high in rock samples of Kali River. The results of these investigations are presented and discussed in this paper.     

Using air pollution based community clusters to explore air pollution health effects in children

To study respiratory health effects of long-term exposure to ambient air pollutant mixture, we observed 7058 school children 5-16 years of age living in the four Chinese cities of Lanzhou, Chongqing, Wuhan, and Guangzhou. These children were enrolled from elementary schools located in eight districts, one urban district and one suburban district in each of the above cities. Ambient levels of PM(2.5), PM(10-2.5), total suspended particles (TSP), SO(2), and NO(x) were measured in these districts from 1993 to 1996. Based on a cluster analysis of arithmetic mean concentrations of PM(2.5), PM(10-2.5), (TSP-PM(10)), SO(2), and NO(x), we classified these children into four ordinal categories of exposure to ambient air pollutant mixtures. We tested for exposure-response relationships using logistic regression models, controlling for relevant covariates. We observed monotonic, positive relationships of exposure to the pollutant mixture with prevalence rates of cough with phlegm and wheeze. Other outcomes were not associated with the exposure in a monotonic exposure-response pattern. Even so, odds ratios for cough, phlegm, bronchitis, and asthma in the higher exposure district clusters were all higher than in the lowest exposure district cluster. We found evidence that exposure to the pollutant mixtures had adverse effects on children living in the four Chinese cities.     

An integrated approach to the toxicity assessment of Irish marine sediments: application of porewater Toxicity Identification Evaluation (TIE) to Irish marine sediments

An integrated approach to the ecotoxicological assessment of Irish marine sediments was carried out between 2004 and 2007. Phase I Toxicity Identification Evaluation (TIE) of sediment porewaters from two sites on the east coast of Ireland were conducted. Initial Tier I screening of three Irish sites identified the need for TIE after significant toxicity was observed with Tisbe battagliai and the Microtox assay at two of the assayed sites (Alexandra Basin and Dunmore East). Porewaters classified as toxic were characterised using four manipulations, ethylenediaminetetraacetic acid (EDTA) chelation, sodium thiosulphate addition, C(18) Solid Phase Extraction (SPE) and Cation Exchange (CE) SPE. Prior to initial testing, and TIE manipulations, all porewater samples were frozen at -20 degrees C for several months until required. After initial Tier I testing Alexandra Basin porewater was classified as highly toxic by both assays while Dunmore East porewater only warranted a TIE with T. battagliai. Results of TIE manipulations for Alexandra Basin porewater and the Microtox Basic test were inconclusive. The toxicity of the porewater in this assay was significantly reduced after freezing. Three experimental episodes were conducted with one month between each for the Alexandra Basin porewater. After each month of freezing the baseline toxicity was further reduced in the Microtox assay, therefore it was not possible to draw accurate conclusions on the nature of the active contaminants in the sample. However, toxicity to T. battalgiai did not change after storage of the porewater. The C(18) and CE SPE decreased the toxicity of Alexandra Basin porewater to the copepod indicating that both organic and cationic compounds (e.g. metals) were active in the sample. Dunmore East porewater was assayed with T. battalgiai and again a combination of organic and inorganic compounds were found to be partly responsible for the observed toxicity (C(18), CE SPE and EDTA reduced toxicity). Results from these TIEs provide insight into the complexity of interpreting marine TIE data from porewater studies where mixtures of unknown substances are present.