300C is pretty damn high... that's like 500F. I generally cook on my grill to get to really high heat, and that is definitely at the high end of what I'd even do with the heat.
At that's the low-point for the effect. I'm not sure that commercial products necessarily all experience that reaction at that temperature.
That's above the smoke point of any oil I could imagine cooking with. While I'm sure you can't discount it entirely, I would not consider it something you would need to worry about unless you were throwing caution to the wind with your cooking process, or perhaps left your stove unattended.
