In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine safe levels of contaminants in drinking water which do or may cause health problems. These non-enforceable health goals, based solely on possible health risks and exposure over a lifetime, are called maximum contaminant level goals (MCLG). Contaminants are any physical, chemical, biological or radiological substances or matter in water.
The MCLG for polychlorinated biphenyls is zero. EPA has set this level of protection based on the best available science to prevent potential health problems