Pollution, like money, is fungible. Once you breathe carbon dioxide into the atmosphere, it’s interchangeable with all the other CO2 on the planet, just like how, when you deposit $20 into your bank account, it’s inseparable from the $40 that’s already there.
Fungibility shouldn’t mean immunity from consequences, however. If that $20 comes from, say, selling fentanyl to schoolchildren, then the police can seize your $60 in assets, at least temporarily. And if you’re spewing pollution into the air, then you should be held accountable for your part in befouling the entire atmosphere.