Adaptation requirements for the use of measured BCF for a realistic risk assessment of organic chemicals
Résumé
One of the main factor in the secondary poisoning risk assessment is the bioavailability of potentially hazardous organic chemicals, especially in the case of soil contaminated with persistent organic pollutants. In the context of the TROPHé project, the transfer of PCBs and PCDD/Fs to plants and invertebrates has been studied: BCF in several plants and in earthworm had been measured and different models to calculate predator exposition have been used. One of the conclusions drawn is that there is no match between available guidelines to produce measured BCF in terrestrial organisms and the BCF needed with the REACH regulation guidance for ecological risk assessment. This guidance states that the exposure concentration for terrestrial predators can be calculated in taking in account the quantity of soil contained in the earthworms guts and the contaminant fraction bioaccumulated in its flesh. This fraction is calculated as the product of the contaminant concentration in interstitial water and the BCF. But this BCF, relatable to interstitial water, is not comparable with BCF measured with available guideline as OECD 317 – Bioaccumulation in Terrestrial Oligochaetes, relatable to total concentration in soil. Data obtained in the context of the TROPHé project allow for the comparison between PCB-PCDD/F BCFearthworm measured with the OECD 317 guideline and PCB-PCDD/F BCFearthworm extrapolated from the Kow of the substance. It was also possible to illustrate the impact of these differences on the results of the secondary poisoning exposure modeled concentrations. A screening on the ECHA registration site also provides an approximation of the number of registered substances that have a BCFearthworm measured with guideline relatable to total concentration in soil and therefore unusable as such in the recommended methodology according to REACH.