With most industries companies live and die by their reputation. Find a bulk provider with a positive reputation and the creatine you buy is almost certainly going to be safer than e.g. eating at Taco Bell. And with creatine in particular it's so dirt cheap that a lot of motivation for dodgy stuff goes away unlike e.g. with protein powders where amino acid spiking can save a company a bunch of money. And incidentally creatine is one of the substances dodgy companies use for amino acid spiking, just because it's so cheap!
That said it's obviously the right decision to drop it if you're not seeing any effects. The interesting thing about creatine is that people's bodies are very different in their natural levels of creatine, and if you're already at 'saturation' then more creatine isn't going to do anything. Same reason the typical benefits of creatine don't show much difference beyond 5g/day. That's enough to send the overwhelming majority of people towards 'saturation.'
There is a brand of creatine manufactured in the US (con-cret) and a brand manufactured in Germany (Creapure). Either of those companies should address the concern around adulterated powder.
> That's why I dropped creatine since I didn't notice any benefits when I tried it for a year.
Some percentage of people (~20%) are creatine non-responders [1]. It's pretty reasonable to try creatine and then drop it if you find no benefit. I personally find the gain very marginal.
You still haven't specified what negative side effects you're referring to. Nitrogen tends to be inert, so I'm questioning your claim that N2 causes some negative side effect, not your claim that creatine hinders this yet-unnamed side effect
That's why I dropped creatine since I didn't notice any benefits when I tried it for a year.