Butter, eggs, cheese, and fish have it too. Personally I like to stick with those. Liver and kidneys have higher values, but I don't trust "filter" organs these days. Too many potential contaminates unless you're very picky about where you get them.
Kidneys are a "filter" organ, liver really isn't. The liver contains p450 enzymes which chemically modify toxins from the blood as they flow through so that they can easily be filtered by the kidneys... I don't see any reason to expect toxins to be concentrated in the liver.
