Predicted no-effect concentration PNEC

The objective is to predict the concentration of the substance below which adverse effects in a particular environmental compartment are not expected to occur, i.e., the predicted no effect concentration (PNEC). However, in some cases, it may not be possible to establish a PNEC, and a qualitative estimation has to be made instead. An assessment factor is applied to... 

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

In general, only valid studies were used to derive predicted no effect concentrations (PNECs). Because in some cases only a few valid data were available, studies valid with restrictions have been used based on expert judgement. Invalid or non-assignable studies have not been used. In instances of volatile compounds, valid studies were generally those using closed, flow-through systems, preferably with analytical measurements. 

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. 

Effects assessment, by, as in the case of risk assessment for chemicals and pesticides, determining a set of marker organisms (including algae, zebrafish, insect larvae, benthic worm, water flea, etc.) that represent ecosystem components and food networks and are used to indicate acute and chronic effects. This step is also used to define the predicted no-effect concentrations (PNECs). 

The environmental risk assessment approach most commonly adopted consists of estimation of the risk quotient (RQ) (as suggested by Hernando et al. [103]), which is defined as the ratio between the environmental concentration (measured or predicted, respectively MEC and PEC) and the predicted no-effect concentration (PNEC), and can be used to collocate compounds in one of three risk bands RQ < 0.1, minimal risk to aquatic organisms 0.1 < RQ < 1, median risk and RQ > 1, high risk [103—105]. In their risk assessment calculations, [106], further to [107], estimated PNEC values at 1,000 times lower than the most sensitive species assayed, so as to take into account the effect on other, potentially more sensitive, aquatic species to those used in toxicity studies. 

REACH uses the terms derived no-effects level (DNEL) for hazards to human health and predicted no-effect concentration (PNEC) for hazards to the environment. 

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. 

As noted previously, the use of (Q)SAR for effects assessment nearly always uses a static assessment factor to extrapolate to a predicted no-effect concentration (PNEC). Assessment factors may be as high as 10000 (Environment Canada 2003). 

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. 

The Japan Soap and Detergent Association has voluntarily implemented monitoring surveys since 1994 on the concentration of surfactants in the surface layer water of rivers in Japan in order to monitor the situation of persistence of surfactants in public waters and evaluate the effects ofsurfactants on aquatic organisms [2 ]. Table 8.7 shows the measurement results of the concentrations of four surfactants regulated by the PRTR system in the major Japanese rivers during the period from June 1998 to September 2003 (mean levels and highest levels) [2]. The highest levels in the table were all lower than the predicted no-effect concentrations (PNEC) [3, 4] and therefore it was considered that the surfactants cause almost no risks to the ecosystem in the environmental waters. 

It is important to recognize that there are different types of standards Table 2.1 provides some examples of different terms that have been used. This list does not include the technical terms that are sometimes used within that process (such as predicted no effect concentration, PNEC), but those that tend to be used in public documents. 

Guidelines within a process of decision making that may use other information to corroborate success or failure. The outcome might be to seek more information or to impose controls (e.g., use of predicted no effect concentrations [PNECs] in Existing Substances Regulations in the EU). 

Predicted no-effect concentrations (PNECs) are traditionally used in risk assessments and form the basis of most EQS values. There are 3 basic approaches to the derivation of PNECs and resultant EQS values. The traditional method uses standard toxicity data and applies an AF to the most sensitive endpoint to derive a protective concentration. The SSD approach utilizes all available toxicity data to derive a value that is protective of a given percentage (e.g., 95%) of the species and is increasingly being used by many countries, often with a small AF placed on, for example, a predicted HC5 (hazardous concentration to 5% of species, i.e., the 5th percentile of the SSD) based on chronic data. Finally, model ecosystems such as lentic mesocosms can be used to derive safe values, again usually with a small AF. 

There is no consensus about the minimum amount of data required for deriving EQSs, but the use of very small data sets (e.g., toxicity data on 1 alga, 1 crustacean, and 1 fish species) is likely to result in unreliable predicted no-effect concentrations (PNECs) from which EQS limit values... 

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). 

Ultimately a derived no-effect level (DNEL) (in humans) or a predicted no-effect concentration (PNEC)20 (in ecosystems) is calculated for a substance, group of substances or chemical mixture. Assessment factors (AF) - sometimes referred to as uncertainty factors or safety factors - compensate for lack of data and assumptions resulting from dose spacing and other test model parameters (adapted from [124]) ... 

For ecosystems, the collection of threshold values for NO(A)EL for several species is used to determine a predicted no-effect concentration (PNEC) for each environmental compartment. Environmental monitoring often observes effects that different environmental concentrations have on various ecosystem sub-groups. Laboratory multi-species test systems are available, but are limited in number and rarely appear in EU chemical risk assessments (see [125]). 

Commission, exposure of humans and the environment can be considered to be adequately controlled if the Derived No Effect Levels (DNEL) or the Predicted No Effect Concentrations (PNEC) are not exceeded [199]. 

The use of NOECs and LOECs has been questioned as they have some major limitations. Their values depend very much on the concentrations that have been selected in the test set-up. Large concentration steps will result in a large difference between NOEC and LOEC. Moreover, poor test design (e.g. low number of replicates) will result in increased variance of effects and the acceptance of the null hypothesis. As a consequence, the toxicity of a chemical may be underestimated. Statistical measurement endpoints obtained from ecotoxicity testing may be used to derive predicted no effect concentration (PNEC) levels that are employed in ecological risk assessment for chemicals. 

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). 

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). 

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