P
PNEC (Predicted No-Effect Concentration)
Definition
A Predicted No-Effect Concentration (PNEC) is the environmental concentration of a substance below which adverse effects on the environment are not expected to occur. PNECs are derived for relevant environmental compartments (freshwater, marine water, sediment, soil, and secondary poisoning) as part of the Chemical Safety Assessment (Annex I). They are used in the environmental risk characterisation: the risk characterisation ratio (RCR) = measured/predicted environmental concentration (PEC) divided by the PNEC.
Source
REACH Regulation (EC) No 1907/2006, Annex I, Section 3.3; ECHA Guidance on Information Requirements and Chemical Safety Assessment.
Practical Explanation (Compliance Context)
Environmental risk characterisation using PNECs informs the exposure scenarios in the eSDS and the risk management measures required for safe use. Downstream users discharging substances to the environment must ensure their releases do not cause PEC/PNEC ratios above 1.0 in any relevant compartment. If they do, additional risk management (e.g., wastewater treatment improvements) is required.