This bill significantly amends the Federal Food, Drug, and Cosmetic Act by requiring mandatory notification to the Food and Drug Administration (FDA) for substances considered generally recognized as safe (GRAS). Beginning two years after enactment, any GRAS substance will be deemed unsafe for use in food unless it is included on a new publicly accessible list maintained by the FDA or is actively undergoing agency review. Persons using GRAS substances must file a notice with the FDA to propose their inclusion on this list, with specific deadlines for existing and new substances. Upon receiving a notice, the FDA must either add the substance to the list or make a preliminary determination to exclude it within 180 days; failure to act results in automatic listing. If the FDA preliminarily excludes or removes a substance, the responsible party must then request reconsideration, submit a food additive petition, or provide a plan to phase out its use. Furthermore, the legislation establishes a new process for the FDA to conduct postmarket assessments of food additives, color additives, and GRAS substances when safety concerns arise from citizen petitions, state officials, or the agency's own initiative. These reevaluations must prioritize concerns supported by clear scientific evidence and involve review by career FDA scientists, subject to public notice and comment rulemaking.