Why traditional 10 ppm and 1/1000-dose cleaning criteria are not equivalent to modern health-based exposure limits.
Traditional cleaning programmes often relied on simple universal criteria such as 10 ppm or a fraction of the therapeutic dose. These approaches were practical, but they do not evaluate the substance-specific toxicology in the same way as an HBEL.
Therapeutic dose measures efficacy
A therapeutic dose is selected to achieve a clinical effect; it is not designed to identify the most sensitive adverse effect from unintended chronic exposure.
Fixed fractions ignore toxicological diversity
Two compounds with similar therapeutic doses can have very different critical toxicities and uncertainty.
Why legacy limits can remain useful
A historical limit that is more restrictive can sometimes be retained as an internal alert or process target, but that does not make it a health-based assessment.
Modern expectation
Current risk-based frameworks expect scientifically justified health-based limits when applicable.
Frequently asked questions
Is a 1/1000 dose always more conservative than an HBEL?
No. The relative numerical value depends on the substance and evidence.
Why is 10 ppm not a universal safety limit?
Because it is not derived from substance-specific toxicology or patient exposure.
Can legacy limits still be maintained?
They can sometimes be retained internally when they are more restrictive, but should not replace the HBEL rationale.
What is the key difference?
HBELs are derived from the pharmacological and toxicological evidence for the substance.
