Metal grill brushes like these, when used, shed their bristles. These razor-sharp thin wires, if they stick to your food and enter your body, can become lodged in your esophagus, puncture your stomach, intestines, or liver, or even cause a pulmonary embolism, which could be fatal. Physicians universally recommend against using metal grill brushes, but since it’s technically a cleaning product and not a food, it’s apparently harder to regulate.
The bristles are so thin they don’t show up on X-rays, and are difficult to remove using non-invasive techniques.
Grill season is more or less over this year, but you might want to just wad up a piece of aluminum foil and use that to clean your grill from now on. (And no, before you ask, you can’t use The Grillbot, the Roomba-ed version of the same metal grill brush.)