 Safety factors are also used in regulatory toxicology and ecotoxicology. For instance, in food toxicology, the highest dose allowed for human exposure has traditionally been calculated as one hundredth of the highest dose (per kilogram body weight) that gave no observable negative effect in experimental animals. Today, higher safety factors than 100 have become common (Dourson and Stara 1983; Pressman et al. 2017).