Risk Assessment of Bioaccumulation Substances. Part II: Description of a Model Framework

This report provides a proposal for a framework for risk assessment of bioaccumulative substances, either from produced water discharges or present as background contamination. The proposed framework is such that it is compatible to the current EIF risk assessment models that are used in the Norwegian offshore oil and gas industry. The risk assessment approach selected for this framework is based on the use of critical body residues (CBR); i.e., body-tissue concentrations above which adverse effects are expected. A three-tiered risk assessment approach is distinguished: tier 1 for worst-case screening purposes; tier 2 based on probabilistic risk assessment using species sensitivity distributions and tier 3 focusing on population modelling for specific species. The latter tier is, because of its specific characteristics, not elaborated in detail. It is proposed to use a food-chain accumulation model to translate species sensitivity thresholds on the basis of CBR into external threshold concentrations, those external thresholds could then be used to either derive an ecosystem PNEC (tier I) or Species Sensitivity Distribution (tier II). This would provide a pragmatic approach to risk assessment of bioaccumulative substances in the context of the EIF modelling framework. Finally, an outline is provided for a research project in which the a risk assessment model for bioaccumulative substances is developed. This model will then be applied to two cases for purposes of demonstration and evaluation. An indication of workload and planning is provided

Modelling Emerging Pollutants in Wastewater Treatment: A Case Study using the Pharmaceutical 17??ethinylestradiol

Mathematical modelling can play a key role in understanding as well as quantifying uncertainties surrounding the presence and fate of emerging pollutants in wastewater treatment processes (WWTPs). This paper presents for the first time a simplified emerging pollutant pathway in the WWTP that incorporates two potential pathways to sequestration. It develops de-terministic and stochastic ordinary differential equations to gain insight into the fate and behaviour of a case study pharmaceutical, with particular focus on sorption to the solid phase, as well as the nature of the experimentally measured solid parent compound. Statistical estimation and inferential procedures are developed and via a proof-of-concept examination, the study explores the transformation pathways of the bioactive chemicals (BACs) in the bioreactor, which is the heart of the WWTP. With a focus on the case study pharmaceutical 17??ethinlyestradiol (EE2), the simulation results show good agreement with the EE2 data. In addition, the results suggest that the experimentally measured solid EE2-parent concentration is very similar to the model-based sequestered EE2-parent concentration

Modelling of priority pollutants releases from urban areas

In the framework of the EU project ScorePP (Source Control Options for Reducing Emissions of Priority Pollutants), dynamic PPs (priority pollutants) fate models are being developed to assess appropriate strategies for limiting the release of PPs from urban sources and for treating PPs on a variety of spatial scales. Different possible sources of PP releases were mapped and both their release pattern and their loads were quantified as detailed as possible. This paper focuses on the link between the gathered PP sources data and the dynamic models of the urban environment. This link consists of: (1) a method for the quantitative and structured storage of temporal emission pattern information, (2) the coupling of GIS-based spatial emission source data with temporal emission pattern information and (3) the generation of PP release time series to feed the dynamic sewer catchment model. Steps 2 and 3 were included as the main features of a dedicated software tool. Finally, this paper also illustrates the method’s applicability to generate model input timeseries for generic pollutants (N, P and COD/BOD) in addition to priority pollutants

Spatially explicit multimedia fate models for pollutants in Europe: State of the art and perspectives

A review by Hollander et al. (in preparation), discusses the relative potentials, advantages and shortcomings of spatial and non spatial models of chemical fate, highlighting that spatially explicit models may be needed for specific purposes. The present paper reviews the state of the art in spatially explicit chemical fate and transport modeling in Europe. We summarize the three main approaches currently adopted in spatially explicit modeling, namely (1) multiple box models, (2) numerical solutions of simultaneous advection–dispersion equations (ADE) in air, soil and water, and (3) the development of meta-models. As all three approaches experience limitations, we describe in further detail geographic information system (GIS)-based modeling as an alternative approach allowing a simple, yet spatially explicit description of chemical fate. We review the input data needed, and the options available for their retrieval at the European scale. We also discuss the importance of, and limitations in model evaluation. We observe that the high uncertainty in chemical emissions and physico-chemical behavior in the environment make realistic simulations difficult to obtain. Therefore we envisage a shift in model use from process simulation to hypothesis testing, in which explaining the discrepancies between observed and computed chemical concentrations in the environment takes importance over prediction per se. This shift may take advantage of using simple models in GIS with residual uses of complex models for detailed studies. It also calls for tighter joint interpretation of models and spatially distributed monitoring datasets, and more refined spatial representation of environmental drivers such as landscape and climate variables, and better emission estimates. In summary, we conclude that the problem is not “how to compute” (i.e. emphasis on numerical methods, spatial/temporal discretization, quantitative uncertainty and sensitivity analysis…) but “what to compute” (i.e. emphasis on spatial distribution of emissions, and the depiction of appropriate spatial patterns of environmental drivers)

Exploiting monitoring data in environmental exposure modelling and risk assessment of pharmaceuticals

In order to establish the environmental impact of an active pharmaceutical ingredient (API), good information on the level of exposure in surface waters is needed. Exposure concentrations are typically estimated using information on the usage of an API as well as removal rates in the patient, the wastewater system and in surface waters. These input data are often highly variable and difficult to obtain, so model estimates often do not agree with measurements made in the field. In this paper we present an approach which uses inverse modelling to estimate overall removal rates of pharmaceuticals at the catchment scale using a hydrological model as well as prescription and monitoring data for a few representative sites for a country or region. These overall removal rates are then used to model exposure across the broader landscape. Evaluation of this approach for APIs in surface waters across England and Wales showed good agreement between modelled exposure distributions and available monitoring data. Use of the approach, alongside estimates of predicted no-effect concentrations for the 12 study compounds, to assess risk of the APIs across the UK landscape, indicated that, for most of the compounds, risks to aquatic life were low. However, ibuprofen was predicted to pose an unacceptable risk in 49.5% of the river reaches studied. For diclofenac, predicted exposure concentrations were also compared to the Environmental Quality Standard previously proposed by the European Commission and 4.5% of river reaches were predicted to exceed this concentration. While the current study focused on pharmaceuticals, the approach could also be valuable in assessing the risks of other ‘down the drain’ chemicals and could help inform our understanding of the important dissipation processes for pharmaceuticals in the pathway from the patient to ecological receptors

Vergelijking van modellen om consumentenblootstelling te berekenen. Inventarisatie van mogelijke verbeteringen van ConsExpo

ConsExpo is een geschikt computerprogramma met rekenmodellen om de mate van blootstelling van mensen aan stoffen in consumentenproducten te schatten. Het programma kan verder verbeterd worden door bepaalde elementen uit andere bestaande rekenmodellen over te nemen. In ConsExpo wordt rekening gehouden met verschillende manieren van blootstelling: via de huid, via inhalatie en via orale opname. Bij het programma hoort een database, waarin standaardwaarden en blootstellingscenario's (wie wordt waar en hoe blootgesteld aan wat en hoe vaak) voor vele producttypen worden aangeboden (bijvoorbeeld cosmetica, verf, reinigingsmiddelen, ongediertebestrijdingsmiddelen en desinfectantia). De beschrijving van deze standaardwaarden en blootstellingscenario's wordt gerapporteerd in zogenoemde 'fact sheets'. Om ConsExpo verder te kunnen verbeteren is een vergelijking gemaakt met andere bestaande rekenmodellen. In de inventarisatie werd gekeken of deze modellen blootstellingscenario's, wiskundige methoden of andere aspecten bevatten die een nuttige aanvulling kunnen zijn voor ConsExpo. Uit de inventarisatie bleek dat ConsExpo zeer geschikt is om de blootstelling te schatten voor stoffen in consumentenproducten. In andere rekenmodellen werden namelijk geen blootstellingscenario's aangetroffen, die niet met ConsExpo berekend kunnen worden. Wel zijn er wiskundige methoden en andere elementen gevonden die voor ConsExpo van groot belang kunnen zijn. Zo kunnen sommige rekenmodellen blootstelling aan stoffen uit meerdere producten berekenen. De berekening van deze zogenaamde 'geaggregeerde blootstelling' zal mogelijk een rol gaan spelen in de risicoschatting van chemische stoffen onder de toekomstige wetgeving in de EU (REACH).ConsExpo is a suitable computer software programme with mathematical models for assessing the exposure of consumers to chemicals in consumer products. This tool can be further improved by adopting certain features from other existing consumer exposure modelling tools. In ConsExpo, different routes of exposure are taken into account, such as the route via the skin, and through inhalation and oral uptake. An important feature of ConsExpo 4.1 is that it contains a database with default values and standard exposure scenarios (who is exposed? where? how? and how often?) for a wide range of consumer product types. Examples include cosmetics, paint, cleaning products, pest control products and disinfectants. The default values and exposure scenarios are described in detail in fact sheets. ConsExpo was compared with other existing consumer modelling tools in an investigation to discover whether the tools contained any exposure scenarios, mathematical models or other features that might be useful for ConsExpo. The aim of the study was to find features that may improve this version (4.1). The investigation demonstrated that ConsExpo is very suitable for assessing exposure to chemicals in consumer products. The other tools did not contain any exposure scenarios for which assessment with ConsExpo is not possible. Nonetheless, a number of mathematical models and other software features have been found that may be of importance to ConsExpo. For example, some tools are capable of assessing exposure to a chemical in multiple products. Assessment of this so-called 'aggregate exposure' will possibly play an important role in the risk assessment of chemicals in future legislation in the EU (REACH).VW

Vulnerability assessments of pesticide leaching to groundwater

Pesticides may have adverse environmental effects if they are transported to groundwater and surface waters. The vulnerability of water resources to contamination of pesticides must therefore be evaluated. Different stakeholders, with different objectives and requirements, are interested in such vulnerability assessments. Various assessment methods have been developed in the past. For example, the vulnerability of groundwater to pesticide leaching may be evaluated by indices and overlay-based methods, by statistical analyses of monitoring data, or by using process-based models of pesticide fate. No single tool or methodology is likely to be appropriate for all end-users and stakeholders, since their suitability depends on the available data and the specific goals of the assessment. The overall purpose of this thesis was to develop tools, based on different process-based models of pesticide leaching that may be used in groundwater vulnerability assessments. Four different tools have been developed for end-users with varying goals and interests: (i) a tool based on the attenuation factor implemented in a GIS, where vulnerability maps are generated for the islands of Hawaii (U.S.A.), (ii) a simulation tool based on the MACRO model developed to support decision-makers at local authorities to assess potential risks of leaching of pesticides to groundwater following normal usage in drinking water abstraction districts, (iii) linked models of the soil root zone and groundwater to investigate leaching of the pesticide mecoprop to shallow and deep groundwater in fractured till, and (iv) a meta-model of the pesticide fate model MACRO developed for 'worst-case' groundwater vulnerability assessments in southern Sweden. The strengths and weaknesses of the different approaches are discussed

Where do uncertainties reside within environmental risk assessments? Expert opinion on uncertainty distributions for pesticide risks to surface water organisms

A reliable characterisation of uncertainties can aid uncertainty identification during environmental risk assessments (ERAs). However, typologies can be implemented inconsistently, causing uncertainties to go unidentified. We present an approach based on nine structured elicitations, in which subject-matter experts, for pesticide risks to surface water organisms, validate and assess three dimensions of uncertainty: its level (the severity of uncertainty, ranging from determinism to ignorance); nature (whether the uncertainty is epistemic or aleatory); and location (the data source or area in which the uncertainty arises). Risk characterisation contains the highest median levels of uncertainty, associated with estimating, aggregating and evaluating the magnitude of risks. Regarding the locations in which uncertainty is manifest, data uncertainty is dominant in problem formulation, exposure assessment and effects assessment. The comprehensive description of uncertainty described will enable risk analysts to prioritise the required phases, groups of tasks, or individual tasks within a risk analysis according to the highest levels of uncertainty, the potential for uncertainty to be reduced or quantified, or the types of location-based uncertainty, thus aiding uncertainty prioritisation during environmental risk assessments. In turn, it is expected to inform investment in uncertainty reduction or targeted risk management action

Current issues in the characterisation of toxicological impacts

Fate, exposure and effect measures provide a basis for the calculation of characterisation factors in Life Cycle Assessment (LCA). Such characterisation factors provide insights into the relative concern of chemical emissions within and across life cycle inventories, in the context of toxicological stress to humans and to ecosystems. A brief overview is presented in this paper of the available options for toxicological characterisation and of associated issues that will need to be addressed in future consensus-building initiatives. An introduction is provided to issues such as: (1) the benefit of measures calculated at midpoints versus at endpoints in the toxicological cause-effect chains (sometimes termed environmental mechanisms); (2) the need to use multimedia models with spatial resolution; (3) the political consequences of accounting for variations in population density; (4) uncertainties in the toxicological potency measures; and (5) the different options for the toxicological endpoint measure(s). These issues are addressed under the headings of Fate and Exposure, Human Health and (aquatic) Ecosystem Healt