There are three hidden dangers associated with taking fish oil supplements. 1. Bad manufacturing processes can allow heat, light, or air to oxidize the oil and cause it to go rancid. 2. Fish oils can contain toxins like mercury and arsenic. 3. Fish oil can be radioactive in some areas of the world where there is a high amount of radioactive waste near the coastline. These issues can be avoided by taking good quality fish oil that has been third-party validated. Avoid buying cheap bulk fish oil a