CMC & ManufacturingLast reviewed May 2026

Elemental Impurity(Elemental Impurity)

Inorganic impurities, principally heavy metals, that may be present in drug products and require assessment under ICH Q3D.

Usage Examples

The ICH Q3D elemental impurity risk assessment identified vanadium from a stainless steel reactor as low risk requiring no routine testing.
USP <232> testing confirmed all Class 1 elements below 30% PDE control threshold.

What is Elemental Impurity?

Elemental impurities are metals and other inorganic elements present in drug products from raw materials, excipients, manufacturing equipment, or container-closure systems. ICH Q3D (2014, revised 2019) established harmonized Permitted Daily Exposure (PDE) limits for 24 elements classified into three classes based on toxicity and likelihood of occurrence.

Manufacturers must conduct a risk assessment for all drug products evaluating: intentionally added elements (catalysts, reagents), potential elements from raw materials or excipients, and container-closure extractables. The assessment documents elemental sources, estimated contribution to finished product, and comparison to PDE limits. Products with identified risk require confirmatory testing and specification controls. USP General Chapter <232> and <233> provide compendial methods aligned with Q3D.

Regulatory Context

This term appears most often in cmc & manufacturing workflows where submission quality, regulatory evidence, and audit readiness depend on consistent language. It is commonly referenced alongside ICH Q3D, USP 232, USP 233.

FDAICHHealth Canada

When This Matters

The ICH Q3D elemental impurity risk assessment identified vanadium from a stainless steel reactor as low risk requiring no routine testing.
USP <232> testing confirmed all Class 1 elements below 30% PDE control threshold.

Common Mistakes

Failing to align CMC change narratives with current CFR/ICH expectations.
Submitting incomplete control strategy documentation.
Separating manufacturing and regulatory review cycles too late in execution.

Related Regulations

ICH Q3DUSP 232USP 233

Frequently Asked Questions

24 elements: Class 1 (arsenic, cadmium, mercury, lead — most toxic, must be assessed regardless of source), Class 2A (cobalt, nickel, vanadium — must be assessed when intentionally added or likely present), Class 2B (assessed only if intentionally added), Class 3 (lower toxicity, assessed based on route of administration).

No — ICH Q3D supports risk-based approach. Risk assessment may conclude no routine testing is needed if sources are controlled and exposure remains well below PDE. High-risk products typically require release and stability testing.

USP <232> adopts the Q3D PDE limits; USP <233> provides validated analytical methods. Together they establish a harmonized US pharmacopeial framework. Q3D is the underlying scientific standard; USP chapters are compendial implementation.