No. Cs-137 is a side effect of running nuclear reactors. The Tchernobyl disaster caused a lot of it. It came down as fallout with rain. So the soil got differently burdened with it according to rainfall in critical days. Especially fungus/mushrooms got enriched with it a long time in the specific areas. Foraging mushrooms got intensely discouraged by authorities, at least in some German areas. Later, they found accidentally high doses in mushroom imported from Czechia many years later.
Exposing to radioactivity does not generate Cs
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