Where for God's sake are you even getting "Mossad" and "poisoning"? There was apparently a radioactive leak at the Weizmann Institute in 1957. Professor Dror Sadeh, in whose laboratory it happened, died of cancer in 1993, i.e. 35 years later. Another researcher died of cancer in 1969 and someone else died of leukemia a month after the leak (which means it was probably unrelated to that specific incident). Sure, exposure to radiation in the laboratory, and not just that particular leak, must have elevated their cancer risk. Cancer deaths are pretty common among early nuclear researchers. But elevated risk of cancer years later is not the same as radiation poisoning. And the Weizmann Institute is not the Mossad.
Oops I meant to say "Arafat poisoning" not "Mossad poisoning" in my original comment. I can no longer edit it. I don't have any solid evidence/source for Israel's involvement, just weird coincidence that they came up on Wikipedia. Purely speculation.
Russian agents learning from Israel perhaps.