TiO₂ comes in many different forms. However, only a few of these forms are considered food-grade (acceptable to be added to food). Many studies that raised concern about the safety of TiO₂, including the concern for genotoxicity, used forms of TiO₂ that are not considered acceptable for use in food and have different properties than food-grade TiO₂. Other studies did use food-grade TiO₂, but took steps to break the material down into smaller particles than what would normally be found in food.