Original: Polychlorinated biphenyls ( PCBs ; CAS number ) are a class of organic compounds with 1 to 10 chlorine atoms attached to biphenyl , which is a molecule composed of two benzene rings . The chemical formula for PCBs isC12H10-xClx .
Simplified: Polychlorinated biphenyls ( often shortened to PCBs ) are organic chemical compounds that contain chlorine atoms .