PNEC

Data sets on toxicity to aquatic organisms vary considerably from compound to compound, with dibutyltin being the best studied. Results of toxicity tests for all compounds are summarized in Figure 2. Values for all but one test on the octyltins have been set at the solubility of the compounds, since no toxicity was observed below the solubilities derivation of PNECs for the octyltins are, therefore, more precautionary than for the other compounds. 

Table 28 outlines the critical end-points for the organotin species and the estimated PNECs derived using appropriate uncertainty factors. For the purposes of comparability, all values have been converted to the chloride salt. 

Organotin End-point Uncertainty factor Estimated PNEC (ug/i)... 

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.

Les rapports PEC/PNEC sont sensiblement inferieurs a 1, ce qui indique que, compte tenu de leur concentration dans Tenvironnement, ces organostanniques representent un risque faible. Localement, le rapport PEC/PNEC peut etre parfois superieur a 1, en... 

Finally, in the risk characterization step, the PEC/PNEC quotient that defines the risk of the substance in the environment is calculated. If the quotient (PEC/PNEC) is less than 1, the substance do not present risk to the environment. More information is available in the European Commission Technical Guidance Document on Risk Assessment [3] and in the United States Environmental Protection Agency s Guidelines for Ecological Risk Assessment [6]. 

The risk characterization procedure will result in a quantitative comparison per substance of the outcome of the exposure assessment and of the effects assessment. This comparison is made through the ratio PEC/PNEC. The generic name for PEC/ PNEC in EUSES is risk characterization ratio (RCR). Other ratios are used in EUSES for the risk characterization such as the margin of safety (MOS) or the ratio of the estimated no-effect or effect level parameter to the estimated exposure level for human subpopulations and the acceptable operator exposure level (AOEL). 

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. 

Reference toxicological values for HRA for the selected pollutants were obtained from ISS/ISPESL [21] and IRIS [22] databases or derived from animal in vivo studies (rat or mouse) and using appropriate safety factors while PNEC concentrations were obtained from previously selected peer-reviewed freely available databases [23] such as ECOTOX [24], ChemIDPlus advanced [25] and specific reviews. 

Table 4 EC50 (in mg L ) used to calculate PNEC (by dividing EC50 by an assessment factor (AF) of 1,000), for fish, daphnids (Daphnia magna) and algae for some of the most ubiquitous pharmaceuticals detected in environmental waters...

PEC / PNEC < 1 no Risk for this application - no action needed PEC / PNEC 21 there is a Risk regulative Action needed... 

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... 

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. 

Alternative Methods PNEC Predicted no effect concentration... 

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

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