Millions of human gametes are stored worldwide. Cryostorage presents many potential risks to the cryopreserved cells/tissues, including loss of viability and most of all contamination. Assisted reproductive technology (ART) clinics need to develop effective strategies to manage these risks. Human ART is the only medical discipline where human gametes and embryos with the potential to produce live births are routinely stored in liquid nitrogen or nitrogen vapor (LN2/NV).
The risk of infection is real, especially when new, highly infectious agents arise. Airborne contaminants come into contact with LN2/NV and are cryopreserved. While some industrial sectors (drug manufacturing, food and beverage sterile packaging) carry out raw filtration of LN2 before use, this precaution is not yet mainstream, although it is increasingly used in the field of human ART. During the COVID-19 pandemic, manufacturers of drugs/disposables/culture media tried to mitigate contamination risk by sourcing raw materials from low-risk regions, but this approach is not feasible in the case of LN2/NV, which can thus become potential vectors of contamination. The risks associated with the use of contaminated LN2/NV are virus awakening and contamination of thawing cells, the environment, and operators.