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2A - Mixture toxicity (MOP/80) Uncertainties in Dioxin like response testing in the presence of PCB. Schramm, Karl-Werner1, 1 GSF - Institute of Ecological Chemistry, Neuherberg, Bavaria, Germany ABSTRACT- Uncertainties to measure dioxin like response of PCB are determined by several factors. Additivity and antagonism of non-dioxin-like PCB are known and can alter the effect. In general dioxin like PCB can be considered to be additive in a concentration related manner.TEF values are differing within one order of magnitude which has also been reported elsewhere. Antagonistic effects of PCB seem to be less important. The time course of the response to different PCB reveals to be an even more important factor. Short testing can lead to increased values for dioxin like response. For example the difference between CALUX and EROD is obvious and caused by different testing durations. In this context it should be mentioned that testing times such as that in the CALUX protocol which are located in a dynamic part of the time response curve are especially critical and should be avoided. In conclusion the uncertainties of DLR testing in vitro in the presence of PCB are low within a given test system. The robustness of the result depends more on the time point of testing than on antagonism. In addition the sample pre-treatment protocol can dramatically affect the results. Especially the testing of crude extracts on a short term will cause overestimations of DLR. PCB respond to an lower extend in the in-vitro assays and are metabolised to a certain extend, which resulted significantly different TEF values published. Key words: CALUX, EROD, PCB, UNCERTAINTY |
