The use of depleted uranium munitions has been fiercely debated, with opponents like the International Coalition to Ban Uranium Weapons saying there are dangerous health risks from ingesting or inhaling depleted uranium dust, including cancers and birth defects.
Because the issue is specific to the region and started specifically after the tank battle where DU ammunition was used. If it would be a general issue with some dangerous chemical being used, weβd expect to see similiar issues in other regions. Of course it is hypotheticakky possible that at the same time some dangerous and persistant chemical exposure happened in the region, but that is not plausible and also the US would have a strong interest in finding such an alternative explanation. But there isnβt any research published, that provided an alternative.
Also look into the wording of the US when sending the ammunition to Ukraine. They state that no radiation hazard is to be expected for the Ukrainians. They do not talk about a toxicological hazard.