New challenges in environmental analytical chemistry: Identification of toxic compounds in complex mixtures

Toxic effects evidenced in the environment are most often caused by mixtures of known and unknown pollutants. One of the key challenges in environmental chemistry and ecotoxicology is to characterize and identify those toxicants in relation with the effect. However, many of the current bottlenecks in the assessment of organic contaminants in our environment are related to the difficulty of evaluating various chemical classes and biological effects within complex mixtures and more precisely to link both approaches. To tackle these analytical challenges, the bioanalytical concept has emerged during the last decade. In this article, we describe through some outstanding examples the current limitations in the chemical-driven approach such as problems encountered for a correct evaluation of water quality when the continuous introduction of new chemicals has to be taken into account in monitoring for correct evaluation of this quality and could led to tremendous analytical costs or some of the integrated bioanalytical approaches as promising powerful tools to improve environmental risk assessment by taking into account the link presence/effect.     

Recent advances in biosensor techniques for environmental monitoring

Biosensors for environmental applications continue to show advances and improvements in areas such as sensitivity, selectivity and simplicity. In addition to detecting and measuring specific compounds or compound classes such as pesticides, hazardous industrial chemicals, toxic metals, and pathogenic bacteria, biosensors and bioanalytical assays have been designed to measure biological effects such as cytotoxicity, genotoxicity, biological oxygen demand, pathogenic bacteria, and endocrine disruption effects. This article is intended to discuss recent advances in the area of biosensors for environmental applications.     

Recombinant cell bioassay systems for the detection and relative quantitation of halogenated dioxins and related chemicals

Proper epidemiological, risk assessment and exposure analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related halogenated aromatic hydrocarbons (HAHs) requires accurate measurements of these chemicals both in the species of interest and in various exposure matrices (i.e. biological, environmental, food and feed). High-resolution instrumental analysis techniques are established for these chemicals, however, these procedures are very costly and time-consuming and as such, they are impractical for large scale sampling studies (i.e. for epidemiological studies and assessment of areas with widespread contamination). Accordingly, numerous bioanalytical methods have been developed for the detection of these chemicals in extracts from a variety of matrices, the majority of which take advantage of the ability of these chemicals to activate the aromatic hydrocarbon receptor (AhR) and the AhR signal transduction pathway. Here we review the currently available in vitro AhR-based cell bioassay systems with a focus on recent recombinant reporter gene cell lines that have been developed for detection and relative quantitation of TCDD and related HAHs. Comparison of the relative sensitivities of the various cell bioassays and examples of their use in screening and analysis of environmental, biological, and food and feed samples are presented. Currently available experimental results and validation studies demonstrate the utility of these cell bioassay systems to provide a relatively rapid, accurate, and cost effective screening approach for the detection of TCDD and related HAHs in a variety of environmental, biological, food and feed samples. The availability of these cell bioassay systems will not only facilitate the large scale sampling studies needed for accurate assessment of contamination and exposure to these environmental chemicals, but they provide avenues for the identification of novel classes of TCDD-like chemicals.     

A perspective on environmental models and QSARs

A general review is presented of the roles of QSARs and mass balance models as tools for assessing the environmental fate and effects of chemicals of commerce. It is argued that all such chemicals must be assessed using a consistent and transparent methodology that uses chemical property data derived from QSARs, or experimental determinations when possible and applies evaluative or region-specific environmental models. These data and models enable an assessment to be made of the key chemical features of persistence, bioaccumulation, potential for long-range transport and toxicity. The other key feature is quantity used or discharged to the environment. A taxonomy of environmental models is presented in which it is suggested that rather than develop a single comprehensive model, the aim should be to establish a set of coordinated and consistent models treating evaluative and real environmental systems at a variety of scales from local to global and including food web models, organism-specific models and human exposure and pharmacokinetic models. The concentrations derived from these models can then be compared with levels judged to be of toxic significance. A brief account is given of perceived QSAR needs in terms of partitioning, reactivity, transport and toxicity data to support these models.     

A perspective on environmental models and QSARs

A general review is presented of the roles of QSARs and mass balance models as tools for assessing the environmental fate and effects of chemicals of commerce. It is argued that all such chemicals must be assessed using a consistent and transparent methodology that uses chemical property data derived from QSARs, or experimental determinations when possible and applies evaluative or region-specific environmental models. These data and models enable an assessment to be made of the key chemical features of persistence, bioaccumulation, potential for long-range transport and toxicity. The other key feature is quantity used or discharged to the environment. A taxonomy of environmental models is presented in which it is suggested that rather than develop a single comprehensive model, the aim should be to establish a set of coordinated and consistent models treating evaluative and real environmental systems at a variety of scales from local to global and including food web models, organism-specific models and human exposure and pharmacokinetic models. The concentrations derived from these models can then be compared with levels judged to be of toxic significance. A brief account is given of perceived QSAR needs in terms of partitioning, reactivity, transport and toxicity data to support these models.     

A strategy to identify specific biomarkers related to the effects of a PCDD/F mixture on the immune system of marine mammals

The cell lines chosen have demonstrated a positive response in terms of cell proliferation and associated modifications in proteins content, evaluated through DNA and proteins synthesis, at environmentally relevant dose of dioxins, brought by a typical environmental PCDD/F mixture. The response is time and species dependent. After completion of the identification of proteins affected by the intoxication, we will identify a set of specific proteins whose expression is correlated to the dioxin dose and submit the cell culture to the treatment with a single chemical as well as with mixtures. We hope that this will allow us to construct and validate a set of protein biomarkers of exposure to pollutants that will show a predictive aspect for unknown chemicals. The quantitative analysis of the set of biomarkers can then be a more specific bioassay and an alternative to physico-chemical or other already established bioanalytical methods for screening purposes.     

效应引导的污染物分析与识别方法

识别环境样品中主要贡献污染物有助于确定环境风险的来源,是环境治理的前提。单一的化学分析和生物学检测方法常常遗漏主要贡献污染物的信息。效应引导的污染物识别(effected-directed analysis, EDA)是以生物检测引导组分分离、化学分析与污染物鉴定的实用方法,是环境风险评价以及环境样品中主要贡献污染物筛查与识别的有力手段。该方法已成功用于环境中遗传毒物、内分泌干扰物和芳香烃受体效应污染物等污染物的鉴定,为特定污染地区贡献污染物及其来源的确定提供了宝贵的基础数据。本文综述了EDA中所应用的样品提取、分离策略、生物效应检测以及贡献化合物的识别方法,总结了近年来以EDA为手段在环境中识别的效应污染物并对目前EDA应用所存在的问题与未来的发展趋势进行了分析。     

Improved detection of toxic chemicals using bioluminescent bacteria

A sensitive, rapid and simple bioluminescent (BL) assay using bioluminescent bacteria to detect the toxic activity of several chemicals is described. This assay is based on the measurement of inhibition of light production of a bioluminescent bacterial strain, isolated from seawater, in the presence of different toxins like heavy metals, organic chemicals, such as benzene, toluene, ethylbenzene, xylene (BTEX) and a wide range of pesticides in environmental samples. The improvement with respect to other commercial and non-commercial bioluminescent assays consists of the possibility to work at room temperature without the need to thermostat, thus allowing the use of simpler and low cost instruments, or to improve the assay using a microplate format, which makes it possible to analyse several samples also continuously for several hours. Using lyophilised bacteria, the assay is performed in less than an hour, without any bacterial cultivation, which makes the test suitable for rapid and sensitive evaluation of chemical pollutants in environmental samples.     

Wastewater-based epidemiology to assess human exposure to personal care and household products – A review of biomarkers,analytical methods,and applications

Humans are nowadays exposed to numerous chemicals in our day-to-day life, including parabens, UV filters, phosphorous flame retardants/plasticizers, bisphenols, phthalates and alternative plasticizers, which can have different adverse effects to human health. Estimating human’s exposure to these potentially harmful substances is, therefore, of paramount importance. Human biomonitoring (HBM) is the existing approach to assess exposure to environmental contaminants, which relies on the analysis of specific human biomarkers (parent compounds and/or their metabolic products) in biological matrices from individuals. The main drawback is its implementation, which involves complex cohort studies. A novel approach, wastewater-based epidemiology (WBE), involves estimating exposure from the analysis of biomarkers in sewage (a pooled urine and feces sample of an entire population). One of the key challenges of WBE is the selection of biomarkers which are specific to human metabolism, excreted in sufficient amounts, and stable in sewage. So far, literature data on potential biomarkers for estimating exposure to these chemicals are scattered over numerous pharmacokinetic and HBM studies. Hence, this review provides a list of potential biomarkers of exposure to more than 30 widely used chemicals and report on their urinary excretion rates. Furthermore, the potential and challenges of WBE in this particular field is discussed through the review of pioneer WBE studies, which for the first time explored applicability of this novel approach to assess human exposure to environmental contaminants. In the future, WBE could be potentially applied as an “early warning system”, which could promptly identify communities with the highest exposure to environmental contaminants.     

Analytical challenges and the development of biomarkers to measure and to monitor the effects of ocean acidification

Changing ocean-carbonate chemistry caused by oceanic uptake of anthropogenic atmospheric carbon dioxide leads to the formation of carbonic acid, thus lowering the pH of the sea with predictions of a decrease from current levels at 8.15 to 7.82 by the end of the century. The exact measurement of subtle pH changes in seawater over time presents significant analytical challenges, as the equilibrium constants are governed by water temperature and pressure, salinity effects, and the existence of other ionic species in seawater.Here, we review these challenges and how pH also affects dissolved inorganic and organic chemicals that affect biological systems. This includes toxic compounds (xenobiotics) as well as chemicals that are beneficial for marine organisms, such as the chemical signals (i.e. pheromones) that are utilized to coordinate animal behavior. We review how combining analytical, molecular and biochemical tools can lead to the development of biosensors to detect pH effects to enable predictive modeling of the ecological consequences of ocean acidification.     

A novel 'peak parking' strategy for ultra-performance liquid chromatography/tandem mass spectrometric detection for enhanced performance of bioanalytical assays

Sensitive and high-throughput bioanalytical assays are of vital importance to drug discovery and development. Ultra-performance liquid chromatography (UPLC), utilizing sub-2-microm particles, greatly increases the separation throughput and efficiency, resulting in LC peaks as narrow as or less than 1 s (full width at half maxima, FWHM). This, however, could pose practical challenges for bioanalytical applications using quadrupole mass spectrometry (MS) to acquire sufficient data points to ensure accurate and reliable quantitation. Here, we present a novel 'peak parking' strategy to reduce the flow rate during UPLC peak elution, therefore extending the useful MS acquisition window. The high-throughput advantage of UPLC is maintained since no significant increase of the overall UPLC run time is needed. This strategy was demonstrated in an assay development for lansoprazole, a gastric proton-pump inhibitor, in human plasma employing liquid-liquid extraction. The method was validated from 50.0 to 50,000 pg/mL.     

Quality assurance in biological monitoring of environmental exposure to pollutants: from reference materials to external quality assessment schemes

The presence of chemicals in the environment is a matter of concern in that it poses potential health risks. At present, exposure to toxic chemicals and their biological and biochemical effects can be better estimated by biological monitoring, through the systematic collection of specimens from potentially exposed humans. Biological monitoring of human exposure to environmental pollutants is hampered by the difficulty to assess data reliability. As a consequence, the validity of biological monitoring should depend on the strict implementation of a quality assurance (QA) program, which includes a series of procedures aiming to ensure that laboratory results meet defined standards of quality and are reliable. For the validation and monitoring of methods’ performance, to ensure the trueness of measurements and to warrant the traceability to international standards, reference materials (RMs) and certified reference materials should be used. Internal quality control and external quality assessment (EQA) are part of overall QA and are carried out to verify that analytical errors are compatible with the specific requirements or needs of the user. In particular EQA schemes (EQAS) allow to test independently the analytical performance of participating laboratories. In the last decades, increasing concern has been raised by urban air pollution; lead and benzene, two gasoline components released by motor vehicle exhausts, are known to be toxic to humans. For biological monitoring of lead exposure of the general population, screening campaigns, utilizing lead in blood as a biomarker, have been carried out since the 1970s. Strict strategies were adopted to ensure data comparability, including the preparation of RMs, the organization of EQAS and the cross-exchange and analysis of blood samples between laboratories. Biological monitoring of benzene exposure could be carried out by means of various biomarkers such as benzene in blood and benzene, trans,trans-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA) in urine. At present, few RMs and EQAS are available for these biomarkers. A pilot EQAS for t,t-MA in urine, adopted to assess the reliability of data regarding benzene exposure, has been organized and carried out between 1996 and 1997 in Italy. From the accrued experience, it clearly emerges the importance of strategies designed to guarantee the quality of biological monitoring data. The use of RMs and the participation in EQAS are highly recommended in order to improve the global performance of methods and laboratories involved in biological monitoring.     

Use of Knowledge Bases and QSARS to Estimate the Relative Ecological Risk of Agrichemicals: A Problem Formulation Exercise

Abstract

Ecological risk assessments can be used to establish the likelihood that an adverse effect will result from exposure to one or more chemicals. When evaluating contaminated sites with many chemicals present, risk assessors must grapple with the problem of quickly identifying the chemicals that are most likely to be of concern, based on effect and exposure assessment information. Many times data gaps exist and the risk assessor is left with decisions on which models to use to estimate the parameter of concern. In the present paper, a procedure is presented for ranking agrichemicals, utilizing the ASTER (ASsessment Tools for the Evaluation of Risk) system. The procedure was employed to rank the relative ecological risk of forty-nine pesticides historically used in agricultural sites in the Walnut Creek watershed near Ames, Iowa, USA. Empirical data from the ASTER system were used when available in the associated data-bases, and quantitative structure-activity relationships and expert systems were invoked when data were lacking. Separate rankings were conducted based on major species taxonomic groupings. Resulting toxic effects thresholds were compared to surface water concentrations.     

Receptor-Based Screening Assays: New Perspectives in Anti-Doping Control

The so-called “growth promoters”, steroid hormones and β-agonists, are currently controlled by using hyphenated analytical methods (chromatography coupled to mass spectrometry) or, sometimes for screening purposes, on immunoassays. These methods are often too specific to allow an effective multianalyte control. To develop more efficient assays, the use of hormonal receptors as detection tools (receptor-based binding assays and cell-based assays) is proposed. Receptor-based assays represent useful tools in screening of hormonal residues in food, but they could also be applied in doping control (to detect “new” hormonal substances). Furthermore, these assays could be used to monitor the human exposure to endocrine disruptors.     

Recording from an Identified Neuron Efficiently Reveals Hazard for Brain Function in Risk Assessment

Modern societies use a continuously growing number of chemicals. Because these are released into the environment and are taken up by humans, rigorous (but practicable) risk assessment must precede the approval of new substances for commerce. A number of tests is applicable, but it has been very difficult to efficiently assay the effect of chemicals on communication and information processing in vivo in the adult vertebrate brain. Here, we suggest a straightforward way to rapidly and accurately detect effects of chemical exposure on action potential generation, synaptic transmission, central information processing, and even processing in sensory systems in vivo by recording from a single neuron. The approach is possible in an identified neuron in the hindbrain of fish that integrates various sources of information and whose properties are ideal for rapid analysis of the various effects chemicals can have on the nervous system. The analysis uses fish but, as we discuss here, key neuronal functions are conserved and differences can only be due to differences in metabolism or passage into the brain, factors that can easily be determined. Speed and efficiency of the method, therefore, make it suitable to provide information in risk assessment, as we illustrate here with the effects of bisphenols on adult brain function.     

Identification of Phototoxic Polycyclic Aromatic Hydrocarbons in Sediments Through Sample Fractionation and QSAR Analysis

Abstract

The toxicity of certain polycyclic aromatic hydrocarbons (PAHs) can be greatly increased by simultaneous exposure of test organisms to ultraviolet (UV) wavelengths present in sunlight. This phenomenon, commonly termed photoinduced toxicity, had been evaluated extensively in laboratory settings where only one chemical of concern was present. However, more recent studies have demonstrated that complex mixtures of PAHs present, for example in sediments, also can cause phototoxicity to a variety of aquatic species when the samples are tested in simulated sunlight. Unfortunately, because these types of samples can contain thousands of substituted and unsubstituted PAHs it is difficult, if not impossible, to use conventional analytical techniques to identify those responsible for photoinduced toxicity. The objective of the present study was to link two powerful ecotoxicology tools, toxicity-based fractionation techniques and QSAR models, to identify phototoxic chemicals in a sediment contaminated with PAHs emanating from an oil refinery. Extensive chromatographic fractionation of pore water from the sediment, in conjunction with toxicity testing, yielded a simplified set of sample fractions containing 12 PAHs that were identified via mass spectroscopy. Evaluation of these compounds using a recently developed QSAR model revealed that, based upon their HOMO-LUMO gap energies, about half were capable of producing photoinduced toxicity. We further evaluated the phototoxic potential of the reduced set of PAHs by determining their propensity to bioaccumulate in test organisms, through calculation of octanol-water partition coefficients for the chemicals. These studies represent a novel linkage of sample fractionation methods with QSAR models for conducting an ecological risk assessment.     

Bioanalytics: detailed insight into bioprocesses

The principles of bioanalytical systems for an on-line bioprocess monitoring are described within this paper. These sensor systems can be interfaced to the bioprocess in different ways according to the needs of the single bioprocess. Modular systems are necessary, which can fit exactly to the needs of the single process. Invasive as well as non-invasive bioanalytical tools are described and discussed in detail. Immunosensors give the possibility to monitor high molecular weight components within short time intervals. Non-invasive optical sensors allow the direct monitoring of various analytes such as oxygen pH for the complex fluorescence behavior of the bioprocess medium. These so-called fluorescence sensors offer the possibility to monitor intra- as well as extracellular components without interfering with the bioprocess. An industrial example for the application of bioanalytical tools for a process optimization are presented in this application. Here a biosensor system is used to optimize the downstreaming of molasses on a technical scale. The economic as well ecological advantages are discussed.