The article is a bit technical (I know there are some ultra smart people lurking on T-Nation who can interpret it though,) but from what I can understand, it might be best to avoid cod liver oil and get your vitamins and EFAs from other sources.
It seems to also be somewhat preliminary, and it doesn’t say how much arsenic there is in cod liver oil. Wikipedia http://en.wikipedia.org/wiki/Cod_liver_oil also mentions other toxins that can be found in cod liver oil, and how most are refined out and tested for. However, the arsenic the above article talks about isn’t a heavy metal in the oil. It is bound in the fatty acids, and the speculation is to what happens when you ingest it. When people ingest cod liver oil, the same metabolite appears as when people ingest arsenate.