Mastering Permitted Daily Exposure (PDE)

In a shared pharmaceutical facility, a single miscalculated cleaning limit can trigger an FDA 483 observation, halt production, or force the costly dedication of equipment worth millions. Regulatory authorities worldwide have moved well beyond arbitrary thresholds: today, compliant cleaning validation demands scientifically rigorous, health-based exposure limits – and at the heart of that science sits the Permitted Daily Exposure (PDE).

This white paper cuts through the complexity. Written by PLG’s UKRT- and ERT-certified toxicologists, it explains exactly how a PDE is derived, why the mathematics matter far more than most manufacturers realise, and how a single over-conservative uncertainty factor can cascade into failed cleaning validations, endless out-of-specification investigations, and multi-million-dollar facility dedications.

How PDE, ADE, and ADI differ – and which metrics regulators actually require.

The step-by-step ICH methodology behind a defensible PDE calculation, including the five uncertainty factors (F1–F5) and when additional Modifying Factors apply.

How Maximum Allowable Carryover (MACO) is directly linked to your PDE – and why a poorly derived value collapses your cleaning programme.

The ‘over-conservative trap’: how stacking unnecessary uncertainty factors produces an artificially low PDE that makes compliant manufacturing operationally impossible.

The full regulatory landscape: EMA HBEL Guideline, ICH Q3C/Q3D, ISPE Risk-MaPP, and ICH Q9.

QA/QC managers and heads of regulatory affairs responsible for cleaning validation strategies, as well as manufacturing directors seeking to optimise shared facility operations without compromising audit readiness.

The Authors:

	Vishnu Jatoth, Medical Writing Specialist & Toxicologist
	Amit Salvi, Clinical & Non-Clinical Operations Director