Trihalomethanes induce sister chromatid exchanges in human lymphocytes in vitro and mouse bone marrow cells in vivo.

The four major trihalomethanes (THMs) found in chlorinated drinking water (CHCl3, CHCl2Br, CHClBr2, and CHBr3) have been investigated for their ability to induce sister chromatid exchanges (SCEs) and cell-cycle delays in human lymphocytes in vitro and to induce SCEs in mouse bone marrow cells in vivo. Each THM tested caused dose-dependent increases in SCE frequency and delays in the cell cycle. The THMs differed greatly in their ability to induce these cytological effects in vitro, with CHBr3 being the most active compound and CHCl3 the least active compound, whereas they were not markedly different in their ability to induce SCEs in vivo.