R. Gellermann The world we really live in – communication on radiation In order to make the communication on radiation and radia- tion levels more tangible and clear to the generalpublic, mea- sured results from actual living environments are needed. The paper demonstrates by means of measured results of the ambi- ent dose rates (ODL) thatthe ambient dose rates in the centre of German cities locally exceed levels typical forthe respective geogenic environmentsignificantly. The highest dose rates which have been measured up to nowreach 680 nSv/h. The role of these results from the radiation protection point of view is discussed and a level of 300 nSv/his suggested as an upper level of the normal ambient dose rate in the urban environ- ment. Still higher dose rates have been found in areaswith radioactively contaminated soil. The need forremediation of such contaminated sites is indicated. Die Welt in der wir wirklich leben – Kommunikation über Strahlung. Um die Kommunikation über Strahlung und Strah- lenpegel mit Laien konkreterund anschaulicher zu gestalten, sind Messwerte aus dem realen Lebensumfeld nötig. Der Bei- trag zeigt anhand von Messergebnissen der Umgebungsstrah- lung (ODL) in Zentren deutscher Städte, dass in Stadtzentren lokal deutlich höhere ODL vorkommen als es dem geogenen Umfeld entspricht. Die höchsten bisher gemessenen ODL- Werte liegen bei 680 nSv/h. Die Bedeutung dieser Befunde aus Sicht des Strahlenschutzeswird diskutiert und ein Wert von 300 nSv/h als oberer Normalbereich im urbanen Umfeld vor- geschlagen. Noch höhere Werte der ODL sind von Flächen radiologischer Altlasten bekannt. Auf die Notwendigkeit solche Altlasten zu sanieren wird hingewiesen. 1 Introduction Radioactivity and the emitted ionising radiation are non-per- ceivable withhuman senses . Therefore,any public dialogue on thistopicrequiresappropriate illustration. For such illus- tration it is frequentlybeing referred to official information of state institutions (e. g. Annual Reports of Environmental Ministries),to officially published measured data (e. g. IMIS data in Germany),to well-known areas with enhanced back- ground radiation like Saxony orthe Bavarian Forest in Ger - many orto high background areas worldwide (frequentlycit- ed isKerala in India). This kind of communication creates the impression that German people live in aworld generally characterised by very low radiation,whichisspatiallyand temporally invariantand harmless . If we analyse the cases mentioned before in more detail, it soon becomesapparentthat these casescharacterise onlya part of the surroundings people live in. The German IMIS- grid measures radiation mainly at sites outside the urban en- vironment. But for illustration of radiation in everyday life, such kind of comparisonsshould preferably stem from actual living environments . Thiscomparison should notbe restricted toextreme values, but should characterise the “world we really live in” in acomprehensible way . First surveys of ambient dose rates in Germany have been carried out in the 1960 th and 1970 th [1– 3]. In severalpublica- tions Bonka started to use measured dataas a reference to ra- diation atwell-known places in Germany [4– 6] in communi- cation. With a similar approach measurements have been performed in the last decade in central places in German towns . Selected results of thiswork arepresented in this pa- per. 2 Performance of measurements The measurements reported in this paperwere carried out from 2007 to 2010. A dosimeter Automess 6150AD 4 with scintillation detector AD-b/E has been used. This device was calibrated to equivalent dose rate H x till 2009. The calibration was switched to ambient dose rate H*(10) in 2009. The device wasregularly checked and annually calibrated atthe calibration site of the German Federal Agency of Ra- diation Protection (BfS). The calibration factor for doses low- erthan 300 nSv/h was between 0.99 and 1.01. A few measurements have been carried out with a RadEye PRD. Because this device indicates an energy compensated dose rate that does not correspond with H x or H*(10) at low ratesthe measurements were performed in the impulse mode and afterwardsrecalculated into dose rates based on a specific calibration. The measurements have been performed as “screening measurements”, i. e. whilst walking in publicareasthe dose rate in 1 m heightwas continuously observed and typical lev- els have been registered. This measuring approach was not in- tended to determine a “representative” value of the dose rate. Instead the aim wasto determine the variability of dose rates in the city centres as a basis for communication about radia- tion in everyday life. 3Results Until the first months of 2010 twenty-one German townswith more than 20,000 inhabitants have been “screened” for dose rates in their central areas . For 15 of these townsthe ranges of dose rates obtained are depicted in the diagram of Fig. 1. For comparison the range of dose rates derived from IMIS- data in the surrounding of each town was calculated. The evaluated data representthe terrestrial radiation of five time intervals each of them lasting two weeks during 2008 and 2009. The intervalswere selected in such a waythatsnow cov- er during the observation time could beexcluded. The mean KT_kt-110260 – 26.4.12/stm media köthen R. Gellermann:The world we really live in – communication on radiation 77 (2012) 3 Ó Carl HanserVerlag, München 1