Inhalation TTC values: A new integrative grouping approach considering structural, toxicological and mechanistic features.

The present publication describes an integrative grouping concept to derive threshold values for inhalation exposure. The classification scheme starts with differences in toxicological potency and develops criteria to group compounds into two potency classes, namely toxic (T-group) or low toxic (L-group). The TTC concept for inhalation exposure is based on the TTC RepDose data set, consisting of 296 organic compounds with 608 repeated-dose inhalation studies. Initially, 21 structural features (SFs) were identified as being characteristic for compounds of either high or low NOEC values (Schüürmann et al., 2016). In subsequent analyses these SF groups were further refined by taking into account structural homogeneity, type of toxicological effect observed, differences in absorption, metabolism and mechanism of action (MoA), to better define their structural and toxicological boundaries. Differentiation of a local or systemic mode of action did not improve the classification scheme. Finally, 28 groups were discriminated: 19 T-groups and 9 L-groups. Clearly distinct thresholds were derived for the T- and L-toxicity groups, being 2 × 10(-5) ppm (2 µg/person/day) and 0.05 ppm (4260 µg/person/day), respectively. The derived thresholds and the classification are compared to the initial mainly structure driven grouping (Schüürmann et al., 2016) and to the Cramer classification.

Exposure and ecotoxicological risk assessment of mixtures of top prescribed pharmaceuticals in Swedish freshwaters.

Surface water concentrations of 54 pharmaceuticals were predicted for seven major Swedish rivers and the Stockholm City area basins using the STREAM-EU model. These surface water concentrations were used to predict the ecotoxicological impact resulting from the exposure of aquatic organisms to this mixture of 54 pharmaceuticals. STREAM-EU model results indicated that <10 substances were present at median annual water concentrations greater than 10 ng/L with highest concentrations occurring mostly in the more densely populated area of the capital city, Stockholm. There was considerable spatial and temporal variability in the model predictions (1-3 orders of magnitude) due to natural variability (e.g. hydrology, temperature), variations in emissions and uncertainty sources. Local mixture ecotoxicological pressures based on acute EC50 data as well as on chronic NOEC data, expressed as multi-substance potentially affected fraction of species (msPAF), were quantified in 114 separate locations in the waterbodies. It was estimated that 5% of the exposed aquatic species would experience exposure at or above their acute EC50 concentrations (so-called acute hazardous concentration for 5% of species, or aHC5) at only 7% of the locations analyzed (8 out of 114 locations). For the evaluation based on chronic NOEC concentrations, the chronic HC5 (cHC5) is exceeded at 27% of the locations. The acute mixture toxic pressure was estimated to be predominantly caused by only three substances in all waterbodies: Furosemide, Tramadol and Ibuprofen. A similar evaluation of chronic toxic pressure evaluation logically demonstrates that more substances play a significant role in causing a higher chronic toxic pressure at more sites as compared to the acute toxic pressure evaluation. In addition to the three substances contributing most to acute effects, the chronic effects are predominantly caused by another five substances: paracetamol, diclofenac, ethinylestradiol, erythromycin and ciprofloxacin. This study provides regulatory authorities and companies responsible for water quality valuable information for targeting remediation measures and monitoring on a substance and location basis.

Variation in predicted internal concentrations in relation to PBPK model complexity for rainbow trout.

The present study is motivated by the increasing demand to consider internal partitioning into tissues instead of exposure concentrations for the environmental toxicity assessment. To this end, physiologically based pharmacokinetic (PBPK) models can be applied. We evaluated the variation in accuracy of PBPK model outcomes depending on tissue constituents modeled as sorptive phases and chemical distribution tendencies addressed by molecular descriptors. The model performance was examined using data from 150 experiments for 28 chemicals collected from US EPA databases. The simplest PBPK model is based on the "Kow-lipid content" approach as being traditional for environmental toxicology. The most elaborated one considers five biological sorptive phases (polar and non-polar lipids, water, albumin and the remaining proteins) and makes use of LSER (linear solvation energy relationship) parameters to describe the compound partitioning behavior. The "Kow-lipid content"-based PBPK model shows more than one order of magnitude difference in predicted and measured values for 37% of the studied exposure experiments while for the most elaborated model this happens only for 7%. It is shown that further improvements could be achieved by introducing corrections for metabolic biotransformation and compound transmission hindrance through a cellular membrane. The analysis of the interface distribution tendencies shows that polar tissue constituents, namely water, polar lipids and proteins, play an important role in the accumulation behavior of polar compounds with H-bond donating functional groups. For compounds without H-bond donating fragments preferable accumulation phases are storage lipids and water depending on compound polarity.

White paper on the promotion of an integrated risk assessment concept in European regulatory frameworks for chemicals.

The vision of a sustainable and safe use of chemicals to protect human health, preserve the environment and maintain the ecosystem requires innovative and more holistic approaches to risk assessment (RA) in order to better inform decision making. Integrated risk assessment (IRA) has been proposed as a solution to current scientific, societal and policy needs. It is defined as the mutual exploitation of environmental risk assessment (ERA) for human health risk assessment (HHRA) and vice versa in order to coherently and more efficiently characterize an overall risk to humans and the environment for better informing the risk analysis process. Extrapolating between species which are relevant for HHRA and ERA requires a detailed understanding of pathways of toxicity/modes of action (MoA) for the various toxicological endpoints. Significant scientific advances, changes in chemical legislation, and increasing environmental consciousness have created a favourable scientific and regulatory environment to develop and promote the concept and vision of IRA. An initial proof of concept is needed to foster the incorporation of IRA approaches into different chemical sectorial regulations and demonstrate their reliability for regulatory purposes. More familiarity and confidence with IRA will ultimately contribute to an overall reduction in in vivo toxicity testing requirements. However, significant progress will only be made if long-term support for MoA-related research is secured. In the short term, further exchange and harmonization of RA terminology, models and methodologies across chemical categories and regulatory agencies will support these efforts. Since societal values, public perceptions and cultural factors are of increasing importance for the acceptance of risk analysis and successful implementation of risk mitigation measures, the integration of socio-economic analysis and socio-behavioural considerations into the risk analysis process may help to produce a more effective risk evaluation and consideration of the risks and benefits associated with the use of chemicals.

High extraction efficiency for POPs in real contaminated soil samples using accelerated solvent extraction

Systematic investigations were performed to study the dependence of the extraction efficiency of persistent organic pollutants (POPs), including chlorobenzenes, HCH isomers, DDX, PCB congeners, and PAHs, on the accelerated solvent extraction (ASE) operating variables solvent and temperature. Mixed soil samples from two locations with considerable differences in soil properties and contamination in the Leipzig-Halle region (Germany) were used. The objective was to optimize ASE for the extraction of POPs from real soil samples and to improve on the results achieved with Soxhlet extraction (SOX). Solvents with differing polarities were tested. Quadruple and triple determinations were performed on the two soils, respectively, between 20 and 180 degrees C in 20 degrees C steps. All the results were compared with those obtained by SOX, as well as, in some cases during preliminary studies, by ultrasonic extraction (USE). In ASE, the optimum conditions proved to be two extraction steps at 80 and 140 degrees C (average RSD 10.7%) with three static cycles (extraction time 35 min) using toluene as solvent and at a pressure of 15 MPa. Owing to the superior analyte/matrix separation by ASE, in many cases for real soil samples analytical values better by up to 1 order of magnitude or even more were obtained compared to SOX results.

Ozone effects on nitrogen incorporation and superoxide dismutase activity in spruce seedlings (Picea abies L.).

The influence of low concentrations of ozone (100 ppb) on nitrogen incorporation and the specific activity of superoxide dismutase (SOD) in 3-yr-old cloned spruce seedlings was studied under controlled conditions (potted plants in fumigation chambers). For the determination of nitrogen uptake, 15 N tracer experiments were performed using emission spectrometric isotope analysis. Superoxide dismutase (SOD) activity was determined by inhibition of formazan formation. Low doses of ozone led to a significant increase in both NO3 -N uptake from the soil and in specific SOD activity. The results show that stable isotope 15 N tracer technique analysis is a suitable tool for the investigation of potential impacts of air pollutants on the nitrogen metabolism of plants.

First-order and pseudo-first-order elimination kinetics.

There is evidence that, for a number of chemicals, the elimination characteristics during bioconcentration do not follow monophasic first-order kinetics. In the first part of the present communication, a simple mathematical formula is presented that allows a clear-cut distinction between monophasic (pseudo-) and first-order and morephasic or higher-order elimination processes. The second part gives the mathematical description of a simple monophasic pseudo-first-order two-compartment model, which allows a quantitative kinetic analysis in the case of both initial compound and metabolite elimination.

Fate of POPs (DDX, HCHs, PCBs) in upper soil layers of pine forests.

Organochlorines (HCH isomers, DDX and individual PCBs) were determined in pine needle litter and upper soil layers of three forest test areas in central Germany. The contents accumulating over a number of years or even decades in the organic surface layer are compared with the levels of new inputs from needle fall as well as with the levels of older inputs in the upper mineral soil layer. Differences in behaviour between the soil horizons are discussed, especially concerning the DDX and HCH groups. With approximately comparable Corg values (approx. 21-24%) the pH value in the range of 4.24-2.90 in the O-horizon of the forest soils exerts a large influence. Hence the A-horizon represents--for p,p'-DDT and gamma-HCH in particular--at pH values of 2.90 a pollutant reservoir which should not be underestimated and which could endanger the rhizosphere and the groundwater. According to PCBs, in the more acidic soils with a pH value <4.0 the lipophilic higher polychlorinated biphenyls were found to be more highly enriched in the humus layer.

Biomonitoring of airborne inorganic and organic pollutants by means of pine tree barks. I. Temporal and spatial variations.

Scots pine (Pinus sylvestris L.) bark samples were collected at two field sites (Neuglobsow, Rösa) and in different years between 1987 and 1996 in the east of Germany. The barks were analyzed with respect to the following inorganic and organic substances: Al, As, B, Ca, Cd, Ce, Cr, Cu, Fe, Hg, Mo, NH4+, Ni, NO3-, PO4(3)-, Pb, Sr, SO4(2)-, Ti, V, W, Zr, Zn, benzo[a]pyrene, fluoranthene, pyrene, alpha-hexachlorocyclohexane (alpha-HCH) and dichlorodiphenyltrichloroethane (DDT). In addition to bark samples from the site Rösa, 53 test sites were investigated in the Nature Park Dübener Heide. Here, the analysis of the barks aimed at discovering spatial patterns of the above-mentioned substances. Since 1991, most of the determined substances (e.g. sulfate, nitrate, calcium, lead, benzo[a]pyrene, alpha-HCH) show decreased concentration values in bark samples from both sites. Temporal variations reflect substantial infra-structural changes in eastern Germany, especially at Rösa and in the industrial region around the cities Leipzig, Halle, and Bitterfeld. Moreover, nitrate concentrations in barks are increasing since 1995. The trend can be explained with increased nitrogen emissions from motor traffic and livestock farms. Spatial patterns of sulphate and ammonia reflect inputs from power plants and agriculture in pine stands of the Nature Park Dübener Heide. The results show that barks of pine trees can be used as biomonitoring tools to indicate and characterize depositions of airborne organic and inorganic pollutants.

Economic upheaval in 1990-93 and the ecological situation in central Germany.

German reunification in 1990 resulted in economic and social upheavals in all of the newly-formed German states. One typical example is the Leipzig-Halle-Bitterfeld region, where many of the industrial plants were fully or partly demolished for economic and technical reasons. Additionally, changes in the political climate led to the closure of a number of major military bases. Despite generally improved environmental standards, dismantling was sometimes accompanied by substantial emissions of chlorinated insecticides and other persistent organic pollutants, as is highlighted for the first time in the present paper. Our analyses are based on a regional biomonitoring net covering 7500 km2 in the Leipzig-Halle-Bitterfeld area during the time period 1990-93. The results enable increased concentrations of airborne contaminants to be attributed to processes linked to the economic upheaval of this time.

Persistent organic pollutants in agricultural soils of central Germany.

Concentrations of persistent organic pollutants (HCHs, DDX, PCBs and HCB) were measured in topsoils from 11 agricultural fields in the lee of large disused industrial plants in the Leipzig-Halle region at varying distances from emitters. The investigations clearly indicate the deposition of anthropogenic pollutant inputs, not only in the past, but also today. The pollution potential was assessed on the basis of current guide values and limits, as well as in relation to values found in agricultural soils elsewhere in Germany, in Europe and in the USA. The reference values were mainly exceeded for DDX and gamma-HCH (lindane). The PCB pattern was determined and the degradation ratios between the parent substances and their metabolites (DDX and HCH isomers) were calculated in order to distinguish between the previous and current pollutant input of pesticides by means of principal component analysis.

Anthropogenic impacts on natural nitrogen isotope variations in Pinus sylvestris stands in an industrially polluted area.

Natural variations of the nitrogen isotopes 15N/14N (delta15N values) and the N concentrations of one-year-old needles from 7-12-year-old pine trees (Pinus sylvestris L.) were determined on 27 sites in the heavily polluted Leipzig-Halle region (former GDR). At three selected sites measurements were repeated over a period of 2 years. N concentrations and delta15N values in different needle age classes were compared at the three sites. The delta15N values of the N in the humus layer and the potential plant available N in the A(h) horizon of the local soil were determined. The 15N/14N isotope ratios (delta15N values) of one-year-old pine needles in the region of Leipzig-Halle were found to vary depending on their specific location by a factor of up to one order of magnitude (-9.6 per thousand to + 0.4 per thousand ). N concentrations in one-year-old pine needles varied between 0.71 and 1.38 mmol eq N g dw(-1). Pine stands with positive or slightly negative delta15N values and high N concentrations in one-year-old needles were concentrated around the cities of Leipzig and Halle and in the industrial areas. More negative delta15N values and lower N concentrations in one-year-old pine needles were found on sites at greater distances from the industrial agglomerations, mainly in the NE forested part. Site specific differences in the delta15N values of the N in the humus layer from three selected sites were similar to those found for the needles. No site specific differences, however, were found for the delta15N values of the water soluble nitrogen fraction from the mineral soil horizons of the same sites.

Application of different RP-HPLC methods for the determination of the octanol/water partition coefficient of selected tetrachlorobenzyltoluenes.

Reversed-phase high-performance liquid chromatography (RP-HPLC) in both, isocratic and gradient elution mode (stationary phase: LiChrospher 100 RP-18; mobile phase: water/methanol or water/acetonitrile) was used for a renewed determination of octanol/water partition coefficients (Kow) of selected tetrachlorobenzyltoluene (TCBT) isomers. Reported Kow values identify this substance class as very hydrophobic but the data are relatively inconsistent. Based on a series of calibration runs with hydrophobic reference substances of different chemical structure at various eluent compositions we tested different approaches for the evaluation of isocratic retention factors (logk) and found substantial differences between the direct calibration procedure at special methanol volume fractions in the mobile phase (0.95-0.80) and the use of retention factors extrapolated to pure water as eluent (logkw). The logKow values obtained for the TCBTs with the latter approach are around 0.5 units higher and closer to literature data. The gradient elution experiments yield slightly better results compared to the isocratic direct calibration procedure, but not as good as the calibration with log kw. In addition, the use of the RP-HPLC retention factors for estimating sorption coefficients (Koc) of TCBT isomers is discussed.

Correlation of aerobic biodegradability of sulfonated azo dyes with the chemical structure.

The reported data of biodegradability of variously substituted 25 sulfonated azo dyes were divided into two classes: 8 dyes designated "rapidly biodegradable" and 17 dyes "not rapidly biodegradable", by applying principal components analysis (PCA). The biodegradability of the dyes was modeled with the discriminant technique of two-value regression analysis based on structural descriptors. A statistically significant and biologically meaningful regression model that gives perfect classification was obtained, and the results were compared with the previous qualitative interpretation of the substituent effects on biodegradation. The coefficients of the regression model revealed a significant interaction between ring substituents for biodegradability. The results facilitate understanding of the mechanism of degradation.

Urease inhibition: a tool for toxicity identification in sediment elutriates.

A method for the detection and confirmation of heavy metal toxicants in sediment elutriates based on a urease inhibition assay, ICP-AES analysis and EDTA chelation in the frame of toxicity identification evaluation (TIE) is presented. Zinc was identified as the major toxicant in pHstat elutriates of sediments of the river Saale (Germany). Implications of natural and anthropogenic chelating agents, which are frequently present in environmental samples, on toxicity confirmation of heavy metals based on the toxic unit approach are discussed.

Bioassay-directed identification of organic toxicants in river sediment in the industrial region of bitterfeld (Germany)-A contribution to hazard assessment

Bioassay-directed identification of toxicants in an acetonic extract of a sediment of the riverine Spittelwasser in the industrial region of Bitterfeld (Germany) was conducted. For this purpose, a combination of chromatographical fractionation, chemical analysis, and a biotest battery including Vibrio fischeri (inhibition of bioluminescence), Daphnia magna (immobilization), and Scenedesmus vacuolatus (inhibition of cell multiplication) was applied. Major toxicants identified and confirmed were methyl parathion (D. magna), prometryn, N-phenyl-beta-naphthalene amine, PAHs (S. vacuolatus), and tributyltin (all biotests). Toxicity to V. fischeri was dominated by elemental sulfur. Results indicate high toxicant loads in the sediment about 7 years after closedown of a majority of chemical production sites at Bitterfeld. Comparison of potential exposure and toxicity data indicate a severe hazard potential to aquatic organisms due to organic toxicants. The results illustrate the potency of a biotest battery for identification of toxicants in contaminated sediment within the frame of toxicity identification procedures.http://link.springer-ny. com/link/service/journals/00244/bibs/37n2p164.html

15N metabolic test for the determination of phytotoxic effects of chemicals and contaminated environmental samples.

A stable isotope(15)N-nitrogen test (ESIMA = Ecotoxicological Stable Isotope Metabolic Assay) was developed to assess biological effects and the potential toxicological hazard of chemicals and contaminated environmental samples on plant metabolism. The assay measures the effect of toxicants on the incorporation of a(15)N labelled tracer into the total nitrogen fraction (both the nonprotein and protein fraction) of plants. Segments of Pisum arvense epicotyls are used as test substrates because of their high metabolic activity. The plant material is incubated under standardised conditions for two hours; subsequently(15)N incorporation is analysed by determining the(15)N abundance ((15)N atom-%) in the epicotyl segments. The effects of toxicants are evaluated by comparing the(15)N incorporation rates of control tissue and epicotyl segments exposed to individual chemicals or complex environmental samples. The specificity and sensitivity of effects as indicated by ESIMA were compared with effects as measured by two established ecotoxicological bioassays, the pollen tube growth test using pollen of Nicotiana sylvestris and the bacterial luminescence inhibition test using pollen of Photobacterium phosphoreum. The results of the study clearly indicate the suitability of ESIMA for assessing toxic impacts on plant nitrogen metabolism.

Use of semipermeable membrane devices (SPMDs). Determination of bioavailable, organic, waterborne contaminants in the industrial region of Bitterfeld, Saxony-Anhalt, Germany.

Triolein-containing semipermeable membrane devices (SPMDs) were employed as passive samplers to provide data on the bioavailable fraction of organic, waterborne, organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs) in streams flowing through a highly polluted industrial area of Bitterfeld in Saxony-Anhalt, Germany. The contamination of the region with organic pollutants originates in wastewater effluents from the chemical industry, from over one-hundred years of lignite exploitation, and from chemical waste dumps. The main objective was to characterise time-integrated levels of dissolved contaminants, to use them for identification of spatial trends of contamination, and their relationship to potential pollution sources. SPMDs were deployed for 43 days in the summer of 1998 at four sampling sites. The total concentration of pollutants at sampling sites was found to range from a low of 0.8 microgram/SPMD to 25 micrograms/SPMD for PAHs, and from 0.4 microgram/SPMD to 22 micrograms/SPMD for OCPs, respectively. None of the selected PCB congeners was present at quantifiable levels at any sampling site. A point source of water pollution with OCPs and PAHs was identified in the river system considering the total contaminant concentrations and the distribution of individual compounds accumulated by SPMDs at different sampling sites. SPMD-data was also used to estimate average ambient water concentrations of the contaminants at each field site and compared with concentrations measured in bulk water extracts. The truly dissolved or bioavailable portion of contaminants at different sampling sites ranged from 4% to 86% for the PAHs, and from 8% to 18% for the OCPs included in the estimation. The fraction of individual compounds found in the freely dissolved form can be attributed to the range of their hydrophobicity. In comparison with liquid/liquid extraction of water samples, the SPMD method is more suitable for an assessment of the background concentrations of hydrophobic organic contaminants because of substantially lower method quantification limits. Moreover, contaminant residues sequestered by the SPMDs represent an estimation of the dissolved or readily bioavailable concentration of hydrophobic contaminants in water, which is not provided by most analytical approaches.

Individual and combined effects of mycotoxins from typical indoor moulds.

The mycotoxins patulin, gliotoxin and sterigmatocystin can be produced by common indoor moulds and enter the human body via inhalation of mycotoxin containing spores and particulates. There are various studies about the individual effects of these mycotoxins, but a lack of knowledge about their effects in mixtures. The aim of this study was to evaluate combined effects on the singe celled organism Tetrahymena pyriformis. Using the MIXTOX model (EU project NOMIRACLE) synergistic or antagonistic effects with dose level deviation or dose ratio dependent deviation were analyzed. The most toxic compound gliotoxin (EC50 0.37 µM) and patulin (EC50 9.3 µM) as shown by the MIXTOX model acted synergistic, caused by similar mode of actions. Within the combination with sterigmatocystin (maximum inhibition of 45% at 12.5 µM) antagonistic effects were observed with switch to synergism if the toxicity of the mixture is mainly caused by sterigmatocystin. In the end the MIXTOX model was applicable for the prediction of combined effects of toxic compounds.

Perspectives for integrating human and environmental risk assessment and synergies with socio-economic analysis.

For more than a decade, the integration of human and environmental risk assessment (RA) has become an attractive vision. At the same time, existing European regulations of chemical substances such as REACH (EC Regulation No. 1907/2006), the Plant Protection Products Regulation (EC regulation 1107/2009) and Biocide Regulation (EC Regulation 528/2012) continue to ask for sector-specific RAs, each of which have their individual information requirements regarding exposure and hazard data, and also use different methodologies for the ultimate risk quantification. In response to this difference between the vision for integration and the current scientific and regulatory practice, the present paper outlines five medium-term opportunities for integrating human and environmental RA, followed by detailed discussions of the associated major components and their state of the art. Current hazard assessment approaches are analyzed in terms of data availability and quality, and covering non-test tools, the integrated testing strategy (ITS) approach, the adverse outcome pathway (AOP) concept, methods for assessing uncertainty, and the issue of explicitly treating mixture toxicity. With respect to exposure, opportunities for integrating exposure assessment are discussed, taking into account the uncertainty, standardization and validation of exposure modeling as well as the availability of exposure data. A further focus is on ways to complement RA by a socio-economic assessment (SEA) in order to better inform about risk management options. In this way, the present analysis, developed as part of the EU FP7 project HEROIC, may contribute to paving the way for integrating, where useful and possible, human and environmental RA in a manner suitable for its coupling with SEA.