For your health and safety, it is critical to clean your grill grates before you start cooking. The concern with wire brush cleaning tools is that the wire bristles can snap off, land in the grates and ultimately find their way into your food. There are hundreds of emergency department visits annually related to ingested wire bristles.
The good news is that there are many safer and just as effective alternatives to a wire brush. Consider using a grill cleaning stone or brick, a bristle free metal brush made of metal coil or even a nylon bristle brush. These are all safer alternatives. If you do want to stick with a wire brush, make sure that it is in good condition and always wipe down the grates or grill surface with a wet paper towel after using the wire brush.