PCBs do not induce DNA breakage in vitro in human lymphocytes.

Polychlorinated biphenyls (PCBs) are classified by IARC as non-mutagenic in vivo. However, despite almost 20 years of research, their mutagenicity in vitro is still debatable. In this work the in vitro cytochalasin B micronucleus test and the alkaline comet assay applied to human lymphocytes were used to study the genotoxicity of a PCB. PCB77, at concentrations ranging from 0.01 to 100 microg/ml, was used in whole blood or isolated lymphocyte cultures, with final dimethylsulfoxide percentages of 0.5-2%. In the micro-nucleus test lymphocytes were exposed for 48 h, and in the alkaline comet assay for 30 min, 1 h and 3 h. No increases of single strand breaks or micronucleus frequencies was found, in contrast to previously reported data. Our data indicate that PCB77 has no clastogenic properties in human lymphocytes.