Toluene may be the ingredient of largest quantity, but it is not the main ingredient. Like a cup of coffee, the main ingredient isn't water, but water is the ingredient with the most quantity. Toluene is the carrier (as well as the petroleum distillates), and the glue part is actually relatively small. They have to list the MSDS controlled ingredients, but the proprietary ingredients that make the glue work are not listed because they are not MSDS controlled. The information you are looking at is not an ingredients list but a list of ingredients to which there are health hazards.