COP 4 (conference of parties Stockholm Convention): from May 4th until May 8th in Geneve. As Switzerland is already busy with the problem of "open application of PCB", some activities seem to start again as well in Germany. Many years ago there were some very few activities at schools in Germany but now others follow. I hope that the awareness of PCB in "open applications" will encrease rapidly. Main sources of the PCB in open application are caulkings with very often above 10 % PCB, paints with often above 5 % PCB and the so-called Wilhelmi-sealings. All bigger buildings constructed in the 60ths and 70ths should be considered as potential sources for open applications of PCB. Besides PCB other toxic material was used, such as PCP, mercury and other organo-chlorine substances.