Paper CYTOGENETIC OBSERVATIONS IN HUMAN PERIPHERAL BLOOD LEUKOCYTES FOLLOWING IN VITRO EXPOSURE TO THz RADIATION: A PILOT STUDY O. Zeni,* G. P. Gallerano, † A. Perrotta,* M. Romano `,* A. Sannino,* M. Sarti,* M. D’Arienzo, † A. Doria, † E. Giovenale, † A. Lai, † G. Messina, † and M. R. Scarfı `* Abstract—Emerging technologies are considering the possible use of Terahertz radiation in different fields ranging from telecommunications to biology and biomedicine. The study of the potential effects of Terahertz radiation on biological sys- tems is therefore an important issue in order to safely develop a variety of applications. This paper describes a pilot study devoted to determine if Terahertz radiation could induce genotoxic effects in human peripheral blood leukocytes. For this purpose, human whole blood samples from healthy donors were exposed for 20 min to Terahertz radiation. Since, to our knowledge, this is the first study devoted to the evaluation of possible genotoxic effects of such radiation, different electro- magnetic conditions were considered. In particular, the fre- quencies of 120 and 130 GHz were chosen: the first one was tested at a specific absorption rate (SAR) of 0.4 mW g 1 , while the second one was tested at SAR levels of 0.24, 1.4, and 2 mW g 1 . Chromosomal damage was evaluated by means of the cytokinesis block micronucleus technique, which also gives information on cell cycle kinetics. Moreover, human whole blood samples exposed to 130 GHz at SAR levels of 1.4 and 2 mW g 1 were also tested for primary DNA damage by applying the alkaline comet assay immediately after exposure. The results obtained indicate that THz exposure, in the explored electromagnetic conditions, is not able to induce either geno- toxicity or alteration of cell cycle kinetics in human blood cells from healthy subjects. Health Phys. 92(4):349 –357; 2007 Key words: health effects; exposure, radiation; genetic effects, radiation; radiation damage INTRODUCTION TERAHERTZ (THZ) radiation covers the frequency range between 100 GHz and 10 THz, which spans the spectral interval between the microwave and the infrared regions of the electromagnetic spectrum. Technologies based on extremely high frequency electromagnetic fields, in par- ticular in the THz region, are quite recent, while a number of applications have been developed, especially in the biomedical area, mainly based on the specific spectroscopic fingerprints of biological matter in this spectral region (Siegel 2004; Woodward 2004). A con- comitant considerable effort has been directed to im- prove THz generation and detection technology to be used for the new applications, even if the understanding of the various mechanisms governing interaction be- tween THz radiation and biological molecules and tis- sues has not yet been fully clarified (Smye et al. 2001). To safely develop the new applications that are breaking through, it is crucial to study the potential health risk related to THz exposure. This aspect exerts particular interest since, to our knowledge, this is the first time that scientific research on possible health hazards accompa- nies from the very beginning the development of a new technology. As a background, there are indications that such radiation could induce damage on the molecular scale. At these frequencies, vibrational and configura- tional molecular transitions become increasingly impor- tant, given that the associated photon energies are in the 4 –120 meV range, corresponding to 0.4 –12 kJ mol -1 . The chemical reactions of large biomolecules in living organisms are not solely controlled by molecular struc- ture; vibrational dynamics play an important role in fundamental processes such as DNA replication and protein interactions (Grosse 2002). In the current literature a considerable amount of research is recorded concerning biological effects at microwave frequencies, recently reviewed in a special issue of the Bioelectromagnetics Journal (2003), but data become scarce as the frequency is increased towards the THz region and are mainly at the boundary between microwave and THz radiation. Pakhomov et al. (2002) have reviewed the biological effects of millimeter waves * Interuniversity Center on Interaction Between Electromagnetic Fields and Biosystems (ICEmB) at CNR—IREA, Via Diocleziano 328-80124 Napoli, Italy; † ENEA-FIM-FISACC, Via E. Fermi 45, 00044 Frascati, Italy. For correspondence contact: Olga Zeni, CNR—Institute for Elec- tromagnetic Sensing of Environment, Via Diocleziano, 328-80124 Naples, Italy, or email at zeni.o@irea.cnr.it. (Manuscript accepted 10 October 2006) 0017-9078/07/0 Copyright © 2007 Health Physics Society 349