In dose–response assessment, what is the point of departure?

• A. It is the exposure concentration used to set regulatory limits.
• B. It is the highest observed adverse effect level in a study.
• C. It is the starting point to derive health-based guidance, derived from NOAEL/LOAEL or BMD.
• D. It is the environmental dose at which effects become observable.

Answer: (C)

In dose–response assessment, the point of departure is the starting point for turning observed effects into a health-based exposure value. It is the dose on the dose–response curve used to anchor risk calculations, usually taken from the no observed adverse effect level, or the lowest observed adverse effect level if no NOAEL exists, or from a benchmark dose derived from modeling the curve. From this starting point, uncertainty factors are applied to derive a reference dose or other health-based guidance value. It’s the basis for risk quantification, not the regulatory limit itself, and it’s chosen to reflect a cautious, data-driven starting point rather than merely the highest observed effect.