critical group

https://doi.org/10.1351/goldbook.15609
Part of a target population most in need of protection because it is most susceptible to a given toxicant.
Source:
PAC, 2007, 79, 1153. (Glossary of terms used in toxicology, 2nd edition (IUPAC Recommendations 2007)) on page 1199 [Terms] [Paper]