Overview
ISO 10993-7:2008 - "Biological evaluation of medical devices - Part 7: Ethylene oxide sterilization residuals" defines how to assess and control residual ethylene oxide (EO) and ethylene chlorohydrin (ECH) in EO‑sterilized medical devices. The standard specifies allowable limits, measurement procedures, and product‑release methods so that EO‑sterilized devices with patient contact can be released safely. Devices with no patient contact (e.g., many in vitro diagnostic devices) are excluded. Ethylene glycol (EG) is discussed but no device limits are specified.
Key topics and technical requirements
- Allowable limits: Devices are categorized by duration of contact (limited A, prolonged B, permanent C). Example limits:
- Permanent contact (C): EO average daily dose ≤ 0.1 mg/day; maximum EO 4 mg (first 24 h), 60 mg (first 30 d), 2.5 g (lifetime). ECH average daily ≤ 0.4 mg/day; corresponding early‑use and lifetime caps apply.
- Prolonged exposure (B): EO average daily ≤ 2 mg/day; maximum EO 4 mg (24 h), 60 mg (30 d). ECH average daily ≤ 2 mg/day; ECH early caps apply.
- Measurement methods: Procedures for gas chromatographic determination of EO and ECH are provided (normative and informative annexes). Extraction techniques are defined, including simulated‑use extraction and exhaustive extraction criteria.
- Product release and compliance: Methods include use of residue dissipation curves, release procedures with/without dissipation data, and guidance for interpreting chromatograms and establishing compliance.
- Risk basis: Limits are established to protect against systemic and local effects (e.g., irritation, mutagenicity considerations) and are intended to be used alongside the broader biological evaluation in ISO 10993‑1.
Applications and users
- Who uses it: medical device manufacturers, sterilization engineers, quality assurance, regulatory affairs professionals, testing laboratories, and clinical safety assessors.
- Practical uses:
- Validate EO sterilization processes and specify acceptable post‑sterilization residues.
- Define sampling and analytical testing protocols (GC methods, extraction).
- Establish product release criteria and justify device safety in regulatory submissions.
- Inform material selection and sterilization decisions during device design to minimize residual EO/ECH exposure.
Related standards
- ISO 10993 series (biological evaluation) - especially ISO 10993‑1, ‑3, ‑10, ‑12, ‑17
- ISO 11135‑1 (EO sterilization process requirements)
- Annexes in ISO 10993‑7 include guidance on GC methods, extraction conditions, flowcharts, and rationale for limit derivation.
ISO 10993-7:2008 is essential for ensuring EO‑sterilized medical devices meet toxicological and clinical safety expectations through defined allowable limits, validated measurement methods, and clear product‑release procedures.
