Predicted environmental concentrations PECs

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... 

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]. 

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. 

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 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... 

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... 

Table 8.4 Predicted environmental concentrations (PECs), predicted no-effect concentrations (PNECs), and risk quotients (RQs) for nano-Ag, nano-Ti02, and CNTs in the environmental compartments air, water, and soil calculated in a realistic (RE) and a worst-case (HE) scenario.

The ecotoxicology of pharmaceuticals is of critical concern to the issue of PIE. The all important question is not whether pharmaceuticals are present in the environment-there is ample evidence that they are-but, at the concentrations at which they are found, whether they do any harm The almost universally used paradigm for attempting to answer this question is the comparison of the Predicted Environmental Concentration (PEC) with the Predicted No Effect Concentration (PNEC)-the so called PEC/PNEC ratio. 

Geographic Information System (GIS) A system that allows for the interrelation of quality data (as well as other information) from a diversity of sources based on multilayered geographical information-processing techniques, hazard (toxic) The set of inherent properties of a stressor or mixture of stressors that makes it capable of causing adverse effects in humans or the environment when a particular intensity of exposure occurs. See also risk, hazard assessment (HA) Comparison of the intrinsic ability to cause harm with expected environmental concentration. In Europe, it is typically a comparison of predicted environmental concentration (PEC) with predicted no-effect concentration (PNEC). It is normally based on a single value for effects and exposure. It is sometimes incorrectly referred to as risk assessment. 

If the chemical composition of the samples is known or at least partly known (in a stepwise TIE approach) or existing data allow for QSAR calculation, the samples can be ranked by TUs. Arts et al. (2006) studied, in 12 outdoor ditch mesocosms, the effects of sequential contamination with 5 pesticides in a regression design. They applied dosages equivalent with 0.2%, 1%, and 5% of the predicted environmental concentration (PEC) subsequently over 17 weeks. Endpoints recorded over 30 weeks included community composition of macroinvertebrates, plankton, and macrophytes, and leaf litter decomposition as functional ecosystem parameters. TUs were calculated in relation to acute toxicity data for the most sensitive standard species Daphnia magna and Lemna minor. Principal response curves (PRCs), a special form of constrained PCA, and Williams test (NOEC, class 2 LOEC) were used to identify the most sensitive taxa. Next to direct effects on certain species, also indirect effects, for example, how the change in abundance of a sensitive species affects the abundance of another, more tolerant species, can be detected only in mesocosm or in situ experiments. All observed effects were summarized in effect classes in a descriptive manner. 

The environmental risk characterization is typically carried out by comparing the predicted no effect concentration (PNEC) to the predicted environmental concentration (PEC). A PEC/PNEC ratio above 1 indicates that the substance poses a potential risk to the environment (European Commission 2003a). 

Calculations are performed to obtain values for the predicted environmental concentration (PEC) and the predicted non-effect environmental concentration (PNEC). Calculations of PEC are based on known release rates and dilution factors in the environment. To estimate PNEC, one divides the LC50 or EC50 for the most sensitive species tested in the laboratory by an arbitrary safety factor (often 1000). This allows room for the great uncertainty in extrapolating from laboratory toxicity data for one species to expected field toxicity for other species. 

The evaluation of the results from the environmental fate leads to a predicted environmental concentration (PEC) of the pesticide representing the exposure level. The accumulation in the food chain of fish is expressed as BAF ( bioaccumulation factor in aquatic environment), that of mammals and birds as BCF (bioconcentration factor in terrestrial environment). Accumulation increases the exposure. The NOAEL (no observed adverse effect level) represents the hazard level. It is the result... 

Monitoring data (measured data), together with calculated data (modelling estimation), are the basis for environmental exposure assessment through the calculation of a predicted environmental concentration (PEC). Compared to modelling data, measured... 

In environmental hazard assessment of chemicals, it is necessary to evaluate exposure and effects on humans or ecosystems, and then to perform an assessment. It consists of comparing the predicted environmental concentration (PEC) and the predicted no effect concentration (PNEC) and to make a judgement as to whether the chemical ent ng into environments is hazardous or not. Ultimately, risk management including regulation of chemicals is necessary if a potential hazard is predicted (see also chapter by Motschi). 

In the hazard assessment of chemicals released into the environment, it is important to evaluate the environmental concentrations of chemicals. Predicted environmental concentrations (PEC) are compared with toxicity data of environmental organisms. Thus, environmental fate models are becoming a valuable tool for the assessment of the potential hazard of chemicals, especially new chemical substances. 

Adverse or harmful effects will occur if measured or predicted environmental concentration (PEC) in various environmental media such as water, soil, sediment and the atmosphere is higher than predicted no effect concentrations (PNEC, or maximum tolerable concentration MTC) based on the above ecotoxicity test results. PNEC values combine the ecotoxicity data with an assessment factw (AF). Data from short-term studies in the laboratory generally need large AFs (100-KXX) are applied to the lowest L(E)C5o) data from long-term laboratory studies or ecosystem field studies need smaller AFs (usually 10 applied to the lowest no observable effect levels (NOEL). 

Such simple models need validation and for this reason ETAD is conducting in a field study to investigate some representative dyes (at manufacturing sites and dyehouses) under a project termed Pathways of Colorants to the Environment. The environmental risk posed by a colorant is a function of both its inherent ecotoxicity and the concentrations attained in the environmental compartments. Unlike other substances eg, household detergents) which are emitted continuously, dyes releases result mainly from batch processes and result in spatial and temporal peak emissions. Obviously, short-time concentrations should be compared with acute data on ecotoxicity, whereas long-tom residual concentrations need to be cranpared with chronic effect levels. Because, data on chronic effects are not often available, empirical information serves as a basis for the effects assessment, ie, the extrapolation to a Predicted No Effect Concentration (PNEC). This PNEC value is to be compared with the so-called Predicted Environmental Concentration (PEC) in order to estimate safe levels of residual dye in the environment. Since it is the dissolved state in which a dyes may become biologically available, it is the aquatic environmental compartment which is primarily addressed here. Nonetheless, some consideration of the impact of dyes on sewage and soil is also included. 

The rationale behind this scheme is to extrapolate environmental release concentrations into steady-state Predicted Environmental Concentrations (PEC) by modelling fate and distribution of a substance using specific exposure scenarios. 

Subsequently, an efficient method of ecological risk assessment was developed. It is based on a comparison of the predicted environmental concentration (PEC) and the predicted no-effect concentration (PNEC). If PEC < PNEC, the substance under consideration is expected to pose no ecological risk in the environment. A comprehensive review about the ecological profile was provided by J. Steber. ... 

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