As tellurium and selenium are both toxic, although the latter is an essential element in small quantities, I would expect polonium to be chemotoxic, but it is difficult to imagine accumulating enough of the element to find this out.
Interestingly, in fish, polonium is the second largest source of radioactivity after potassium, 40K, because it is in secular equilibrium with the nearly five billion tons of uranium found naturally in the ocean.
This was discussed in the context of the (largely failed) effort of the authors of the original "Fukushima Tuna Fish" paper to correct the media stupidity shit storm that grotesquely misinterpreted the original publication of their work, which was about tracking tuna fish migration patterns. Public stupidity led to the survival of many tuna fish that otherwise would have been killed for food, so it wasn't entirely a bad thing, for the fish.
I covered and linked the corrective paper here: Deluded Scientists Think They Can Reassure the Public on the Fukushima Tuna.
The Russian access to polonium is a function of their use of liquid lead bismuth eutectic (LBE) coolants in some of their fast reactors, including submarine reactors. Small amounts of polonium are generated by neutron capture in 209Bi, which leads through two beta decays to 210Po. The main use for 210Po is for thickness gauges and for the neutralization of static in certain sensitive manufacturing situations. Russia is or was the main supplier. It is "milked" from 210Pb more conveniently that it can be isolated from uranium ores.
I'm personally rather fond of liquid lead coolants, although there are many other excellent options for fast reactors besides LBE or neat liquid lead (LL), besides LBE or LL, most of which are superior to the one of which I'm not all that fond, even if it's the most popular, liquid sodium.
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