The picture below summarizes common assessment factors used for PNEC calculation (from ECHA guidance on chemical risk assessment). More data on more species in the same environmental compartment can also reduce uncertainties, thus further decreasing assessment factors. Assessment factors applied for long-term tests are smaller because the uncertainty of the extrapolation from labs to natural environment is reduced. How to Choose Appropriate Assessment Factors?Īssessment factors (AFs) are used to address the differences between laboratory data and natural conditions, taking into account of interspecies differences and intraspecies differences. Usually PNECs are only derived for 4 compartments: fresh water, soil, STP micro-organism and sediment. It is not always necessary to derive PNECs for all mentioned environmental compartments. Required when log Kow>3 or BCF >100 and there is no mitigating property such as ready biodegradability or hydrolysis.NOEC bird/mammal=NOAEL bird/mammal* conversion factors(8-40 for different species) if only NOAEL is available.The lowest value of LC50 bird, NOEC bird or NOEC mammal divided by assessment factors (30-3,000).Important for gases and highly volatile substances.The lowest NOEC/EC10/EC50 value from activated sludge inhibition test or biodegradability studies divided by assessment factors (1~100).The lowest LC50/NOEC/EC10 value for soil living organisms divided by assessment factors (10~100) or.
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