This chapter focuses on how science-based definitions for zero, such as the no observable adverse effect level (NOAEL), are integrated into regulations to determine how much of a chemical humans are allowed to be exposed to with no risk of adverse effects. Toxicologists and public health officials are rightfully concerned with human exposure to potentially toxic chemicals that is constant and that an individual cannot control in exposure routes such as food, water, and air. Chemical food safety encompasses the entire production cycle of food from farm to table. The diversity, breadth, and regulatory control over this essential human endeavor is underestimated. This chapter presents the scientific approaches used to determine safe levels for human consumption of chemicals primarily in meat and milk. Converting toxicological thresholds presented earlier to an allowable or so-called safe level in food is discussed with attention paid to extrapolations to zero. This conversion is based on assuming lifetime exposure to the chemical at this safe level and on how much chemical is in the food that is consumed. It is stressed that exposure below this threshold, even when the chemical is analytically detected in food, is of no toxicological risk, especially if there is only intermittent exposure.