Werner Kördel, et al
Environ Sci Pollut Res 20, 2810-2827 (2013)
Substance-related monitoring is an essential tool in different fields of environmental risk assessment. Soil or water quality is monitored, for example, to check the compliance of environmental burdens with legal threshold values. This is, e.g., an essential element of the Water Framework Directive implemented in the European Union (EU). In case of non-compliance with environmental quality standards, risk mitigation measures have to be taken (e.g., improvement of filter technologies). Another application of environmental monitoring is in the risk assessment of chemicals. Appropriate monitoring data may support the assessment by providing data for the exposure of organisms to certain chemicals or the persistence or accumulation of compounds in environmental matrices. Based on such data it may be ruled that the application of a chemical may only be possible if certain risk mitigation measures are implemented (e.g., usage only in closed systems). Environmental monitoring may also be used for identifying chemicals of emerging concern in different environmental media (e.g., compounds with endocrine properties). Such emerging substances may require the implementation of certain regulations to protect the environment. However, the coverage of new substances in monitoring programs is sometimes hindered by a vicious circle (Figure 1).
A vicious circle may prevent monitoring of emerging chemicals of concern (modified after Kördel et al. 2013).
Since the soundness of such policy decisions (risk mitigation measures and the restriction of the use of chemicals) is partly based on data provided by environmental monitoring programs, the reliability of the monitoring data has to be proven by adequate quality assurance measures.
Recently a project was finalized which investigated substance-related monitoring strategies in environmental media which may be applied in this context. The project work was sponsored by the IUPAC Chemistry and the Environment Division (Div VI) and involved scientists with backgrounds in environmental monitoring and analytical methodology (www.iupac.org/project/2009-048-1-600).
In the course of the project an overview on available problem-orientated monitoring strategies for the substance-related environmental monitoring was elaborated. Besides trend and spatial monitoring, the guidance presents information on snapshot monitoring, non-target monitoring, and retrospective monitoring approaches. These approaches are characterized below.
To assess the relevance of emerging substances, it is often not necessary to investigate a high number of sampling sites in high frequency, as is required for a compliance monitoring. Examples in both the USA and the EU reveal that a snapshot monitoring based on a non-probabilistic approach allows representative data sufficient to establish benchmarks for typical concentrations in environmental media to be generated. There are also new approaches, such as the usage of samples taken according to an opportunistic approach where samples are collected and analyzed centrally. Although such data may be imprecise and incomplete, they help generate the first information on novel or less-investigated compounds.
Most monitoring programs cover only defined target compounds where analytical standards are available. However, in recent years the advancement of analytical methods and data management tools also allows the investigation of unknown compounds in samples. For such a non-target screening, appropriate sample extracts are investigated by sophisticated “hyphenated” methods (mainly chromatographic separation coupled with mass-spectrometric detection). Unknown substances are first characterized by chromatographic and mass fragment parameters, which are now often shared by different laboratories. In a second step, these chemicals may be identified by comparative analysis of appropriate reference compounds. Currently the first attempts to integrate non-target screening into routine monitoring programs are being made.
Retrospective monitoring data on potential exposures and environmental concentration trends may be helpful to evaluate the exposure relevance of a certain chemical which has to be assessed. Trend monitoring data may also be used to identify chemicals of concern (e.g., by revealing increasing concentrations) or to check whether bans of chemicals are effective (decrease of environmental levels after a restriction; policy success control). Such a retrospective monitoring may be realized with samples from environmental specimen banks (ESBs). ESBs are collections of materials sampled with standardized methods and stored under conditions which assure that the chemical information does not change over time. Such archives are operated in several European and Asian countries as well as in the USA and Canada (website of the International ESB Group: www.inter-esb.org). Recent ESB monitoring studies provided valuable information on trends of chemicals like perfluorinated compounds, biocides, ingredients of personal care products, and other emerging substances. An example is shown in Figure 2.
Monitoring data for methyltriclosan, a bioaccumulating transformation product of the biocide triclosan, in fish retrieved from the German Environmental Specimen Bank archive. Data for bream muscle tissue from two sites of the German river Saar are given as ng/g lipid weight. After an increase of levels until about 2004, fish concentrations decreased by about 20 %. Source: www.umweltprobenbank.de/en/ or www.bit.ly/1ZbUgUV
Regarding the performance of environmental monitoring studies, the IUPAC project highlights the necessity of well-trained personnel and appropriate technical equipment, as well as the implementation of quality assurance and quality control measures. It also emphasized that scientifically sound and feasible monitoring concepts strongly depend on a clear definition of the aim of each monitoring program or study. Decisions on sample handling, storage, and the analysis of the samples are important steps for the development of problem-oriented monitoring strategies. The same applies to the selection of appropriate sampling sites, which should be representative for the scenarios to be investigated. These steps are especially critical within international monitoring programs, to ensure the quality of the final monitoring data.
The project findings, based on relevant documents and discussions in the project group, were compiled in a review article published in Environmental Science and Pollution Research.
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