DOC 041 : Persistent Organic Pollutants (POPs) Response to UNEP/INC/CEG-I Annex 1 | January 2000
An ECETOC Task Force started to work on the definition of scientific criteria for POP identification in May 1998. UNEP started to work on this issue in July 1998 and a Criteria Expert Group (CEG) established by UNEP met in Bangkok in October 1998 and in Vienna in June 1999 to determine scientific criteria for POPs. The results of the ECETOC TF can be considered as an answer to the first document produced by CEG1 and have been submitted at the CEG2 meeting to help the general discussion on criteria. A compound has to be persistent, bioaccumulable, long-range transported and show reasons for concern to be nominated as a candidate POP. If nominated, a compound will need to go through a risk assessment to conclude if it has to be included or not in the protocol POPs. For the nomination step the ECETOC TF has concluded: That a ½ life of 6 months is an acceptable value for the persistence criteria in soil, sediment and water based on information on existing POPs and the relation between environmental compartments. For compounds which are not really biodegradable existing 28-day standard tests are not sufficient to measure persistence in relation to the specific needs of the protocol on POP. Adequate methodology and tests will have to be defined. Regarding bioaccumulation, the value of logKow should range between 5 and 8 for the compound to be considered. These limits are dictated by the data available on correlation between logKow and BCF values which show that outside this range the BCF will be less than 5000. The long-range transport and deposition can be studied on the basis of physicochemical properties e.g. the sub-cooled liquid vapour pressure of the compound. It is shown for example that lipophilic compounds with sub-cooled liquid vapour pressures higher than 1 pa will stay mainly in the atmosphere and will not be deposited. The methodology to define the reasons for concern is by comparing observed or expected concentrations in the environment with toxicological and/or ecotoxicological data. As a general consideration, the ECETOC TF concluded that priority should be given to quantitative criteria. For the evaluation stage: A clear need is emerging for a generally accepted multi-media model capable of predicting persistence and long-range transport in the environment. The model will need to take into account the variability of environmental conditions and the different exchanges between the environmental compartments which cannot be considered by single numbers for each compartment as in the case of the persistence criteria.