It's not hypothetical; the contamination through water and inhalation has been demonstrated.
That was a poor choice of words on my part. I didn't mean to imply that depleted uranium isn't an environmental toxin, rather than the extent of any contamination caused by what are ultimately very situational anti-tank rounds is currently unknown, therefore the dangers are currently hypothetical. There are situations where the use of depleted uranium has resulted in areas that are essentially uninhabitable, but those tend to be associated with the far more liberal use of depleted uranium in places like Iraq.
My point overall is that it's really difficult to take either side seriously in this "debate" because neither is engaging in good faith. This is a performative debate for the "benefit" of western media audiences who hear uranium and think of the glowing green rods from the Simpsons. Heck, other heavy metals like tungsten are also toxic if inhaled (I don't want to overstate this, tungsten alloys are a lot less harmful to people than depleted uranium which literally turns into corrosive acid when exposed to water, but just pointing it out).
More importantly though, Russia is not a signatory of the 1997 treaty banning the use of anti-personnel mines, and has made extensive use of them in this conflict. There is extensive video evidence of these mines being used. Ukraine is a signatory and Human Rights Watch has found no evidence that its troops have used anti-personnel mines, but that doesn't mean they haven't. Both sides have used anti-vehicle mines which are not covered by the 1997 ban, but can still be detonated by, for example, agricultural machinery. Russian forces, and in a few cases Ukrainian forces, have used cluster munitions, which beyond the initial impact of firing them into populated areas also leave behind huge numbers of unexploded munitions.
There's even evidence pointing to the use of our old friend white phosphorous.. you know.. that stuff that burns entire chunks out of people and gets lodged inside their bodies to keep burning them from the inside.. then causes their organs to fail from toxicity while doctors are trying to treat the burns. The stuff that narrowly avoided being classed as a chemical weapon because everyone crossed their fingers as hard as they could and swore they were only using it to make smoke. White phosphorous smoke is, as you might expect, really, really bad to inhale by the way, and it can also poison water.
The reality of this conflict is that, however it ends, it's going to leave behind a devastated region in which millions of people live in constant danger. Whatever the hazards posed by depleted uranium introduced to the environment via a tank shell or the costs of cleaning it up, it's not even remotely on the level of a cluster munition, and both sides have used them.
Again, none of this is to justify anything. Just because the situation is bad doesn't mean it can't be made worse. I just think this whole controversy seems a bit divorced from the reality of what's actually going on.
But i am not sure the UK even has alternative armor piercing rounds for the Challenger or in a meaningful number.
It doesn't. In fact, it seems like the smarter elements of Russian propaganda have figured this out and are running that story instead of the obvious crocodile tears about Ukrainian civilians being exposed to depleted uranium while walking extremely carefully around wondering when an anti-personnel mine will pop out of the ground and rip them to pieces in a cloud of shrapnel.
Again, just because the UK has a relatively large military budget doesn't mean it has terribly sophisticated or high-tech equipment, and it certainly doesn't mean it has deep stockpiles.