Good point. What was I thinking? Speaking of that, I remember that a small paintchip hit Space Shuttle Challenger and did some damage to it. They should of thought of making rockets on the ISS, so they can put the trash in it and aim it at the Sun.
The station is in a low orbit. The delta-V required to do that would be very difficult and expensive.
It's a long way from low Earth orbit to escape volcity. All they need to do is slow the rubbish down enough that it eventually falls into the atmosphere and burns up. Don't worry about it hitting anything on the ground. We are constantly pelted with asteroids, so even if a wrench or something survived reentry, it is unlikely to hit anything important.