An article published on March 20, 2017 in the peer-reviewed journal International Journal of Hygiene and Environmental Health, focused on the variability of drug pharmacokinetics in young adult and elderly subjects. The latter subpopulation is known to be more sensitive to chemical exposures, largely due to alterations in xenobiotic metabolism, leading to slower detoxification and elimination rates. These differences may affect the interindividual uncertainty factor (UFH) applied in the calculation of the acceptable daily exposure (ADE) values.

Anthony Streeter and Ellen Faria from Janssen Research & Development LLC, U.S., analyzed the data for 206 drugs extracted from published studies that directly compared young adults and elderly. They found that the differences may arise due to variations in the activity of multiple biotransformation enzymes as well as drug transporters. Based on their analysis, they recommended using a default UFH of 10 when calculating ADEs for worker populations, as these are composed largely of young adults. At the same time, when calculating ADEs for the general population, a default UFH value of 15 should be used, as this allows taking the elderly into consideration.


Streeter, A., and Faria, E. (2017). ”Analysis of the variability of the pharmacokinetics of multiple drugs in young adult and elderly subjects and its implications for acceptable daily exposures and cleaning validation limits.International Journal of Hygiene and Environmental Health 220(4):659-672.