Raw fish oils contain environmental toxins like mercury that accumulate in fish during their life spans, but these toxins can be virtually eliminated with the use of high-quality raw materials and advanced distillation technologies. Nordic Naturals fish oils are molecularly distilled, utilizing an enzymatic process that removes potential environmental toxins (such as heavy metals, dioxins, PCBs, etc.). Independent laboratory testing confirms the removal of PCBs, heavy metals, and dioxins from our oils. Certificates of Analysis are available on our website; simply enter your lot number to view the certificate for your specific bottle.