Polychlorinated biphenyls, or PCB's, were banned from use in the United States in 1979. These toxic, carcinogenic compounds were used in the manufacture of plastics and in electrical transformers and capacitators. Unfortunately, like lead, mercury, and many other substances that we have released into the environment, PCB's persist in the environment for many years. A new study found that children whose mothers have the highest levels of PCB's in their blood and breast milk have dysfunctional immune systems. Specifically, these children developed less of an immune response to certain immunizations. PCB's persist to this day in marine life. The very foods that give us the "good" fats that build our brains (marine fats) are polluted with mercury and PCB's! For this reason, it is important to consume a high quality fish oil that all mercury and PCB's have been removed from. What is ironic to me is that these children already have a toxic load in their bodies, and they are subjected to increased toxic load through immunization! Mercury, formaldehyde, and other toxins commonly used in vaccines are known to be toxic to the developing nervous system and to cause immune dysfunction. There is an excellent new text out on thimersol--the mercury in vaccines--called "Evidence of Harm", by David Kirby. Check it out! Link to Study on PCB's