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Short answer
Gamma irradiation sterilization uses gamma rays, produced by the decay of cobalt-60, to sterilize finished, packaged products at an industrial facility. Its defining traits are deep penetration and no heat, residue or induced radioactivity. Its main limit is that some plastics change under radiation, so each product must be evaluated for compatibility.
Definition and scope
Gamma sterilization is one form of ionizing radiation sterilization. The CDC’s disinfection and sterilization guideline says ionizing radiation is delivered primarily by cobalt 60 gamma rays or electron accelerators, that it has been used for a number of medical products, and that it is suitable for large-scale sterilization. STERIS AST, a contract sterilization provider, describes gamma radiation as generated by the decay of the radioisotope cobalt-60 and names high penetration as its key characteristic.
The FDA’s page on sterilization for medical devices states that radiation is an established Category A sterilization method. The same page describes a pilot program covering sterilization using radiation, including gamma radiation, or ethylene oxide, and one of its purposes is changing radiation sources in a least burdensome regulatory approach. For how radiation compares with steam, ethylene oxide and other methods, see sterilization technology.
How gamma sterilization is used in practice
According to STERIS AST, gamma processing can treat products in their final packaging, and the delivery and absorption of dose depend on product density and packaging size. Dose is measured in kiloGray (kGy), the unit of absorbed dose. The provider also describes ISO 11137 as the approach to validating a dose that achieves a defined sterility assurance level. The required dose is therefore set per product during validation rather than being one figure for every product; the wider framework is covered in sterilization validation and the target outcome in sterility assurance level (SAL).
The CDC states that there are no FDA-cleared ionizing radiation sterilization processes for use in healthcare facilities, and that because of high sterilization costs the method is an unfavorable alternative to ethylene oxide or gas plasma in that setting. In practice gamma is therefore a manufacturer-side step: the product arrives already sterilized, and a clinic or lab does not run it.
What gamma changes and what it does not
Gamma processing has effects on both sides: benefits for heat-sensitive items and material changes in some plastics. The table sets them out with the source for each.
| Effect | What the source states | Source |
|---|---|---|
| Temperature | Minimal or no rise in temperature | STERIS AST techtip on products commonly treated |
| Residue | No chemical residuals remain on processed products | STERIS AST gamma page |
| Induced radioactivity | No induced radioactivity remains on processed products | STERIS AST gamma page |
| Post-processing hold | Requires no quarantine time after processing | STERIS AST techtip |
| Some materials | Embrittlement, discoloration and change in viscosity can occur | STERIS AST gamma page |
| Polyethylene parts | Induced oxidation in polyethylene, and delamination and cracking in polyethylene knee bearings, are cited as deleterious effects on patient-care equipment | CDC disinfection and sterilization guideline |
The first four rows are why providers promote gamma for heat-sensitive items; the last two are why compatibility is judged product by product. For related material behavior, see which plastics are autoclavable and extractables and leachables in single-use systems.
Where it matters for labs, clinics and supply decisions
STERIS AST’s sample list of products commonly treated by irradiation includes catheters, sutures, test tubes and petri dishes, and notes that labware made of styrene and other plastics is temperature sensitive. The provider adds that each product must be evaluated for compatibility with whatever sterilization method is chosen, and that the list is not exhaustive and does not mean gamma is the only option. A practical checklist drawn from these sources:
- Read the labeled method. Sterile single-use items state how they were sterilized; gamma, e-beam and ethylene oxide are separate processes with different trade-offs.
- Ask whether the process was validated for that product and packaging. Dose absorption depends on density and packaging size, and ISO 11137 is the validation approach the provider cites.
- Treat material compatibility as product-specific. Embrittlement, discoloration and oxidation are documented for some materials, not all.
- Do not plan on in-house gamma. The CDC reports no FDA-cleared ionizing radiation processes for healthcare facilities.
- Expect source changes to be a regulatory matter. The FDA pilot program explicitly covers changing radiation sources, including a change from gamma to another radiation source. The other common radiation route is covered in e-beam sterilization, which includes a comparison with cobalt-60 gamma.
Common misunderstandings
Gamma sterilization makes products radioactive
STERIS AST states that no induced radioactivity remains on processed products.
Gamma is safe for every plastic
It is not. The CDC and STERIS AST both document material effects, and the provider’s own guidance is that each product must be evaluated for compatibility.
Gamma is the only radiation option
The CDC names electron accelerators alongside cobalt 60 gamma rays, and STERIS AST says its product list does not indicate that gamma is the only option available.
FAQ
What does gamma irradiation do to plastics?
Depending on the material, it can cause embrittlement, discoloration or a change in viscosity (STERIS AST), and induced oxidation in polyethylene (CDC). Compatibility is evaluated per product.
Does gamma sterilization make products radioactive?
No. STERIS AST states that no induced radioactivity remains on processed products.
Is gamma sterilization used in hospitals?
Not as an in-house process. The CDC states there are no FDA-cleared ionizing radiation sterilization processes for use in healthcare facilities; hospitals receive products sterilized by manufacturers.
What is a kGy?
The kiloGray is the unit of absorbed dose used for radiation sterilization, according to STERIS AST. The dose needed for a given product is set during validation.
Sources
- U.S. FDA, Sterilization for Medical Devices, checked 2026-10-29.
- CDC, Other Sterilization Methods, Guideline for Disinfection and Sterilization in Healthcare Facilities, checked 2026-10-29.
- STERIS AST, Gamma (provider description), checked 2026-10-29.
- STERIS AST, Products commonly treated by irradiation (provider description), checked 2026-10-29.
