GENOTOXICITY Gu¨nter Engelhardt Æ Armin Gamer Æ Pavel Vodicka Ivo Ba´rta Æ Hans-Dieter Hoffmann Æ Gauke Veenstra A re-assessment of styrene-induced clastogenicity in mice in a subacute inhalation study Received: 30 April 2002 / Accepted: 16 August 2002 / Published online: 1 October 2002 Ó Springer-Verlag 2002 Abstract To date, a number of in vivo cytogenetic assays have studied the clastogenicity (chromosome aberra- tions, micronuclei formation) in bone marrow of rodents exposed to styrene by various routes. The majority of all these cytogenetic experiments yielded negative findings (Scott and Preston, Mutat Res 318:175–203, 1994). Recently published data from a micronucleus test in mice exposed via inhalation for up to 21 days showed some positive response, but was not fully conclusive (Vodicka et al., Chem Biol Interact 137:213–227, 2001). Since this exposure regimen has considerable relevance for work- place exposure, the present study was performed to further elucidate these findings. NMRI mice were exposed by whole body inhalation to styrene concentra- tions of 750 mg/m 3 and 1,500 mg/m 3 for 1, 3, 7, 14 and 21 consecutive days (6 h/day). Animals were killed directly after exposure and bone marrow was sampled for analysis of micronucleus induction. Under the experi- mental conditions used in the present investigation, there was no evidence of clastogenicity at any concentration or exposure interval. Keywords Styrene Æ Micronucleus assay Æ Clastogenicity Æ Inhalation Introduction Styrene is an important industrial organic chemical manufactured in large volumes. It is mainly used in the production of polymers and copolymers, the best known of which is polystyrene. Styrene is a volatile material and, due to its widespread industrial use, there is a po- tential for human exposure in the workplace. The highest potential human exposure occurs mainly via the inhalation of styrene vapor during the production of glass-reinforced polyester. The key step in the biotransformation of styrene is the conversion to styrene-7,8-oxide (Leibman and Ortiz 1969; Belvedere and Tursi 1981). This epoxide has a potential for binding with DNA and may pose a geno- toxic hazard. Recent studies, however, have shown that after inhalation of styrene the actual level of DNA binding in rodents is very low (Otteneder et al. 1999; Boogaard et al. 2000). Styrene has been tested extensively in in vitro systems for its genotoxic potential. In the majority of these as- says, styrene itself was not genotoxic (reviewed by Preston 1990; Barale 1991); however, a response could be revealed if test conditions favored its metabolic ac- tivation/conversion to the genotoxic styrene oxide over its inactivation to the non-genotoxic styrene glycol. To date, a number of in vivo cytogenetic assays have studied the clastogenicity (chromosome aberrations, micronuclei formation) of styrene in the bone marrow of rodents. The majority of all these cytogenetic experi- ments yielded negative findings. These data have been summarized and discussed in detail elsewhere (Scott and Preston 1994). Some in vivo experiments for clastogenicity reported positive results in rats after inhalation exposure (Meretoja et al. 1978) and in mice after intraperitoneal injection (Norppa 1981). However, serious questions regarding the Arch Toxicol (2003) 77: 56–61 DOI 10.1007/s00204-002-0406-y G. Engelhardt (&) Æ A. Gamer Æ H.-D. Hoffmann Product Safety, Regulations, Toxicology and Ecology, BASF Aktiengesellschaft, 67156 Ludwigshafen, Germany E-mail: guenter.engelhardt@basf-ag.de Tel.: +49-621-6056762 Fax: +49-621-6051734 P. Vodicka Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic I. Ba´rta Department of General Biology and Genetics, Charles University, 100 42 Prague 10, Czech Republic G. Veenstra Shell Chemicals Ltd, London, UK