| Abstract: | Six polychlorinated biphenyl (PCB) congeners,one technical PCB mixture,and two polybrominated diphenyl ether (PBDE) congeners were studied for their cytotoxicity on four human cancer cell lines and developmental toxicity on zebrafish embryos with or without chorions.All chemicals were tested at four concentrations for exposure time periods ranging from 1 to 6 days.The findings showed no adverse effects on cell growth for any chemicals except that high concentrations of PBDE 209 caused significant inhibition of proliferation in two Human Colon Cancer cell lines,RKO and HCT116,after 3-6 day exposure.PBDE 209 had no effect on Breast Cancer Cells ZR75-1 and MDA-MB-231.In contrast,continuous exposure of zebralish embryos beginning at 5-6 hour post-fertilization to PCBs and PBDEs fbr 6 days produced concentration-dependent increases in malformation and mortality.The degree of sensitivity varied with congener and the presence of a chorion.Specifically,PBDE 209 showed no adverse effect on zebrafish embryos with intact chorions while this chemical led to malformation in 43.33% of larvae without chorions at the highest concentration and exposure time period,suggesting chorions act as barriers for high molecular weight chemicals such as PBDE 209.The PCB structure also influenced the embryonic response.For example,PCB 126 induced severe developmental toxicity at 1μmol·L~(-1) in
embryos with or without chorions,while PCB 105 produced no observable effects even at 10μmol·L~(-1).The developmental
toxicity of these chemicals in descending order is PCB 126≈PCB 156>PCB 1254(Aroclor1254)>PBDE 47>PCB 77>PCB 105≈PCB 118≈PBDE 209.The findings indicate that the toxic response varies between individual cells and in developing embryos where cellular complexity is very different. |
