Guideline for Elemental Impurities
The ICH quality guideline establishing permitted daily exposures (PDEs) and a risk-based approach for controlling elemental impurities in drug products. Q3D(R2) updated PDEs and added cutaneous and transcutaneous routes of administration.
What this does not cover
stated in the document's own scope- Covers elemental (metal) impurities; organic impurities in the substance and product are ICH Q3A and Q3B, and residual solvents are ICH Q3C.
- Sets permitted daily exposures and the risk-assessment approach, not the analytical test procedures, which are the pharmacopoeial chapters (e.g. USP <233>).
- Applies to drug products and their components; it is not a general environmental or occupational metals standard.
- The R2 additions extend to cutaneous/transcutaneous routes, but the guideline still places some product classes outside parts of its scope.
Always verify against the current published text before relying on it for a submission or inspection.
Overview
ICH Q3D(R2) is the harmonised guideline for the control of elemental impurities — metals such as arsenic, cadmium, lead, and mercury, and catalyst residues — in drug products. It establishes permitted daily exposures (PDEs) for elements of toxicological concern and sets out a risk-based process for assessing which elements could be present, from what sources (the drug substance, excipients, water, equipment, and container-closure systems), and whether controls are needed. Q3D(R2) updated some PDEs and added guidance for the cutaneous and transcutaneous routes of administration, extending the framework beyond the oral, parenteral, and inhalation routes covered by the original.
Scope & applicability
Drug products and their components across ICH regions. Implemented through the pharmacopoeias (e.g. USP <232>/<233>).
Legal basis & how it acquires force
Q3D is an ICH Quality guideline; the R2 revision reached Step 4 in April 2022. An ICH guideline is not itself law; regions implement it. The FDA issued Q3D as a guidance for industry, the EMA adopted it as a scientific guideline applied through the marketing-authorisation framework, and Japan implements it through MHLW. The pharmacopoeias align with it: the elemental-impurities general chapters (such as USP <232>/<233> and the corresponding Ph. Eur. texts) operationalise the Q3D limits, which is how the guideline’s PDEs acquire compendial force.
Document structure
| Part | Covers |
|---|---|
| Toxicological basis and PDEs | How permitted daily exposures were derived for each element of concern |
| Element classification | Grouping elements by toxicity and likelihood of occurrence to focus the assessment |
| Risk assessment | Identifying potential elemental impurities and their sources, and evaluating against the PDEs |
| Control of elemental impurities | Options for controlling impurities and converting PDEs to concentration limits |
| PDE values by route (Appendices) | Tabulated PDEs for oral, parenteral, inhalation, and — added in R2 — cutaneous/transcutaneous routes |
| Calculation options (Appendix) | The permitted-concentration approaches for combining components |
Key requirements
- Establish a documented elemental-impurities risk assessment
- Control impurities to within route-specific PDEs
- Justify analytical controls (e.g. ICP-MS)
Implementation tips
- Build the risk assessment from all components and the intended route, not just the API
Revision notes
Q3D(R2) (2022) updated PDEs and added cutaneous and transcutaneous routes of administration.
Where this control fails
live FDA enforcementLive FDA recalls SPEQ maps to this standard’s topics — a SPEQ interpretation, not an FDA classification.
International alignment
Q3D sits in the ICH impurities family alongside Q3A (impurities in new drug substances), Q3B (impurities in new drug products), and Q3C (residual solvents), each governing a different impurity class. It replaced the older non-specific heavy-metals tests with a toxicology- and risk-based approach, and its PDEs are carried into practice by the pharmacopoeial elemental-impurities chapters, so the guideline and the compendia are designed to work together.
ICH Q3D(R2): frequently asked questions
Quick answers to common questions about ICH Q3D(R2).
What is a PDE in ICH Q3D?
A permitted daily exposure is the maximum acceptable daily intake of an elemental impurity, derived from toxicological data. Q3D sets PDEs for elements of concern and provides options to convert them into concentration limits for the drug product and its components.
What did the R2 revision add?
Q3D(R2), finalised in 2022, updated certain PDEs and added guidance and PDE values for the cutaneous and transcutaneous routes of administration, extending the framework beyond the oral, parenteral, and inhalation routes addressed by the original guideline.
How does ICH Q3D relate to the pharmacopoeias?
The pharmacopoeial elemental-impurities general chapters — such as USP <232>/<233> and the corresponding European Pharmacopoeia texts — operationalise the Q3D PDEs and analytical approach, which is how the guideline’s limits acquire compendial, enforceable force.
This standard in practice
Recall domain is a SPEQ mapping of this standard’s topics, not an FDA classification.