Since 1958, FDA and USDA have continued to monitor all prior sanctioned and GRAS substances in light of new scientific information. If new evidence suggests that a GRAS or prior sanctioned substance may be unsafe, federal authorities can prohibit its use or require further studies to determine its safety. In 1960, Congress passed similar legislation governing color additives. In contrast to food additives, colors in use before the legislation were allowed continues use only if they underwent further testing to confirm their safety. Both the Food Additives and Color Additives Amendments include a provision which prohibits the approval of an additive if it is found to cause cancer in humans or animals.
Manufacturers use only the amount of an additive necessary to achieve the desired effect.