That's a good one!
Just make sure that in your research, you are actually able to come up with a conclusion, since that's a key requirement of an EPQ.
Can you maybe look at previous studies, and see whether they've managed to find anything out for sure?
The other thing is that your question must be specific.
You don't need to know what it is from the start, but in the end you must pin things down to one definite line of research.
So maybe think, is there anything particular about such things that you want to find out?