# A "philosophical molecule," hydrogen may overcome senescence and intractable diseases.
> 水素分子が老化と難治性疾患に与える影響：ヒドロキシルラジカル消去の観点からの考察


## Abstract

Reactive oxygen species, particularly hydroxyl radicals (·OH), are identified as central contributors to cellular senescence and the progression of various diseases. Among candidate scavengers, molecular hydrogen (H₂) is highlighted as uniquely capable of penetrating mitochondrial membranes—the primary site of ·OH generation—and neutralizing these radicals. This review argues that endogenous and exogenous H₂ may contribute to both disease prevention and physiological recovery. A practical concern noted is the explosive nature of H₂ gas, which necessitates the engineering of safe inhalation devices suitable for domestic use. The authors advocate broader investigation into H₂ applications across aging-related and refractory conditions.

### Mechanism

Molecular hydrogen penetrates mitochondrial membranes and selectively neutralizes hydroxyl radicals (·OH) generated predominantly within mitochondria, thereby reducing oxidative stress implicated in aging and disease pathogenesis.

## Bibliographic

- **Authors**: Hirano S, Ichikawa Y, Kurokawa R, Takefuji Y, Satoh F
- **Journal**: Med Gas Res
- **Year**: 2020
- **PMID**: [32189669](https://pubmed.ncbi.nlm.nih.gov/32189669/)
- **DOI**: [10.4103/2045-9912.279983](https://doi.org/10.4103/2045-9912.279983)
- **PMC**: [PMC7871941](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7871941/)
- **Study type**: review
- **Delivery route**: inhalation
- **Effect reported**: not assessed

## Delivery context

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

## Safety notes

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [LFL / UFL terminology](https://h2-papers.org/en/safety-notes/lfl-ufl-explained)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 32189669. https://h2-papers.org/en/papers/32189669
> **Source**: PubMed PMID [32189669](https://pubmed.ncbi.nlm.nih.gov/32189669/)