Predicted environmental concentration

Analytical methods for the determination of environmental concentrations (MEC) Models for predicting environmental Concentrations (PEC) In vivo/In vitro assays QSAR models In silico methods... 

On the other hand, indirect methods should be considered as an alternative when analytical measurements are not feasible. Predicting methods involve extrapolating exposure estimates from existing data, e.g., previous environmental monitoring, data about emissions and chemicals production, and questionnaires. Distribution of chemicals among the different environment compartments is also a key aspect for predicting environmental concentrations. Therefore psysicochemical properties (see Sect. 4) are required inputs in these tools. 

For environmental purposes, different approaches for predicting environmental concentrations have been used. Table 3 gives some representative examples of these studies. The input data required are usually the production or consumption of chemicals in the studied area that allow estimating their emission rates to the environment. Depending on the complexity of the scenario, different number of variables can be used to achieve the prediction. 

Regardless the complexity of the models used for predicting environmental concentrations, they share some common requirements regarding to the influencing factors that govern the occurrence and fate of chemicals in the environment ... 

Domenech X, Peral J, Munoz I (2009) Predicted environmental concentrations of cocaine and benzoylecgonine in a model environmental system. Water Res 43(20) 5236-5242... 

Exposure assessment using monitoring data or fate and transport models calculate the predicted environmental concentration (PEC) in each environmental compartment. More information can be obtained from Suciu et al. [4]. 

For the ecological assessment, risk analysis was based on the traditional PEC/ PNEC ratio (Hazard Quotient) where PEC is the predicted environmental concentration (resulting from chemical analysis) and PNEC the predicted no-effect concentration. Ecological assessment for aquatic species was based on rainbow trout or fathead minnow while terrestrial assessment was based on small rodents like mice rats and rabbits. Exposures associated with HQ<1 were considered negligible. 

Table 6 shows the result of predicted environmental concentration in air, soil (natural, agricultural, and industrial), freshwater, and sediment for regional scale (Guiyu region). 

Table 6 Predicted environmental concentration (PEC) of DeBDE (mean standard deviation) ...

Selection of target pharmaceuticals (see Table 1) was based on the following criteria (1) the sales and practices in Spain (according to National Health system), (2) compound pharmacokinetics (the percentage of excretion as nonmetabolized substance), (3) their occurrence in the aquatic media (data taken from other similar studies), and (4) on data provided by environmental risk assessment approaches, which link the calculation of predicted environmental concentrations (PEC) with toxicity data in order to evaluate which compounds are more liable to pose an environmental risk for aquatic organisms [20-22], In the current European... 

The aim of the exposure assessment is to predict the concentration of the substance that is likely to be found in the environment, i.e., the predicted environmental concentration (PEC). Again it may not be possible to establish a PEC, and a qualitative estimation of exposure has to suffice. 

ECVAM European Centre for the Validation of PEC Predicted environmental concentration... 

The method compares the predicted environmental concentrations (PECs), as indices of exposure, with predicted no effect concentrations (PNECs), as indices of... 

For most of the compounds considered, their environmental presence may not only result from direct release during present production or use but also from historical production and use, natural formation or transformation of other products. Therefore, to derive predicted environmental concentrations (PECs), data collected during analytical monitoring programmes are preferred to modelling data provided they are reliable and representative [1]. 

The assessment of whether a substance presents a risk to the receiving environmental compartment is based on a comparison of the measured or predicted environmental concentration (PEC) of the chemical of concern with the predicted no effect concentration (PNEC) to organisms in the ecosystem. This is briefly discussed in Chapter 7.4. Studies carried out so far, e.g. by Vandepitte and Feijtel [91], show that the risk of anionic surfactants such as LAS, AE and AES for the aquatic environment is low, since the PECs are always lower than the maximum permissible concentrations. 

To determine the risks for individual substances in the environment, the concentration of a substance is determined in the individual environmental compartments - water, soil, air - (on the basis of measurements or calculations). This measured or calculated concentration (PEC = Predicted Environmental Concentration) is compared to the concentration at which no detrimental effects on ecosys-... 

To assess the potential environmental impact, studies on environmental fate and effects were conducted for a risk assessment. Steger-Hartmann et al. [125] calculated the predicted environmental concentration (PEC) in surface water and compared the resulting concentration of 2 g with the predicted no-effect... 

The indirect exposure is estimated by the use of FUSES. FUSES estimates concentrations in food and the total daily intake of a substance based on predicted environmental concentrations for (surface) water, groundwater, soil, sediment, and ambient air. The indirect exposure is principally assessed on two spatial scales locally near a point source of the substance, and regionally using averaged concentrations over a larger area. A third spatial scale, the continental scale, is... 

Predictive methods of exposure assessment often rely on single values for input parameters to the exposure model that represent one point on the distribution curve of all possible values for this parameter. This point value can range from a 50th percentile, mean, median, or typical value to a worst-case estimate. In the predictive exposure assessment, a number of parameters are integrated through an algorithm to produce an output such as the predicted environmental concentration (PEC). If many worst-case values are involved, this integration can result in a PEC that has a... 

Guidance to date supports the risk assessment principles for general chemical substances already published by the Commission (1996). Consequently, the risk characterisation simply involves a quantitative comparison of the outcome of the hazard/effects assessment with the exposure assessment. For human risk this involves the calculation of the TER (Toxicity Exposure Ratio) and comparing it with the MOS (Margin Of Safety). For environmental risk the PEC/PNEC ratio (Predicted Environmental Concentration versus the Predicted No-Effect Concentration) for the various environmental compartments. 

Spaepen K.R.I., L.J.J. Van Leemput, P.G. Wislocki, and C. Verschueren (1997). A uniform procedure to estimate the predicted environmental concentration of the residues of veterinary medicines in soil. Environmental Toxicology and Chemistry 16 1977-1982. 

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