PEC/PNEC ratio

Using the PECs from section 6 and the above PNECs (Table 28), both based on the organotin chlorides, risk ratios (PEC/PNEC) can be derived for each of the identified uses of organotins these are summarized in Table 29. Regional PEC/PNEC ratios are given in Table 30. 

Regional PEC/PNEC ratios are all substantially lower than 1, indicating low risk from general... 

Table 29 Local PEC/PNEC ratios for the various uses of organotins.

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. 

Risk assessment for any given environmental compartment is a comparison of the PEC with the PNEC, i.e., the PEC PNEC ratio. If this ratio is below 1, there is no immediate concern. If the ratio is above 1, the assessor decides on the basis of its value and other relevant factors what conclusions apply. If it has not been possible to derive a PEC/PNEC ratio, the risk assessment is a qualitative evaluation of the likelihood that an adverse effect will occur. 

The risk posed by the potential to concentrate into sediments was approached similarly to the aquatic compartment, i.e. using a PEC/PNEC ratio (Table 3.2). When no actual effect data on sediment organisms were available, PNECs in sediments were estimated on the basis of physico-chemical parameters and PNECs in water [1]. The risk posed by the potential to bioconcentrate in fish was assessed by the methodology described by Nendza et al. [2] with the determination of the critical body burden (CBB). This parameter predicts the level of the chemical in the organism which could... 

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. 

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. 

Level 1 provides a simple environmental risk phrase based on the PEC/PNEC ratio ... 

Component-based approach. This is an option if the mixture composition can be determined, for example, by means of chemical analysis, and if a mixture model is available that can predict the mixture effects. The mixture model can either be simple, for example, summation of PEC/PNEC ratios over all compounds into a hazard index (HI) moderately complex, for... 

Figure 5.3 Three alternative options to assess the risk of mixtures 1) mixtures can be tested in the field or the laboratory, particularly completely unknown mixtures 2) if toxicity data on (sufficient) similar mixtures are available, the mixture can be evaluated using a reference value, for example, in a PEC/PNEC ratio and 3) mixtures of which the components are known can be evaluated using component-based approaches (mixture algorithms). PEC = Predicted Environmental Concentration, PNEC = Predicted No Effect Concentration.

Hydrocarbon block method Method for environmental risk assessment of petroleum substances based on calculating and combining PEC/PNEC ratios for blocks of constituent hydrocarbons. 

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). 

Concerning the results of the risk assessments, all three documents state that the margin-of-safety for health risks is significantly uncertain. For Octa and Deca uncertainty in the PEC/PNEC ratio is also stressed, and it is proposed that the traditional PEC/PNEC approach may not be appropriate for these highly lipophilic and largely water insoluble substances. 

As shown in the risk assessment figure, the decision making takes place at the risk characterisation step, where the results of the environmental distribution, the calculated concentration, and the ecotoxicological data, the effect concentration, come together. The most common way is to divide the predicted environmental concentration by the effect concentration in the acute or chronic situation, called the PEC-PNEC-ratio. In the European Union the toxicological concentration is divided by the predicted environmental concentration revealing the TER the toxicity-exposure-ratio. 

The PEC values will then be compared to the appropriate PNEC values for the environmental compartment and a PEC/PNEC ratio determined. 

If the PEC/PNEC ratio is <1, then this indicated that there is no concern and that the substance will not pose an unacceptable risk to the environment. 

Based on this assessment of surface waters, environmental effects in this compartment from esterquats are considered unlikely because comparison of PEC/PNEC ratios are in all cases lower than 1. Moreover, the PNECs are based on values that are higher than the water solubility of the substances and are therefore not due to the direct toxicity of the compounds. 

The esterquats discussed are readily biodegradable and effects are found only at concentrations greater than their water solubility. The (bio)degradation pathway demonstrates that formation of persistent toxic compounds is circumvented. The main degradation products, i.e., polyalcohol quaternary ammonium salts, are not toxic. The ready biodegradability and determined effect concentration strongly indicate that esterquats are safe at the intended maximum usage volumes. PEC/PNEC ratios are lower than 1 for all esterquats examined. 

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