H₂ Papers

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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

review inhalation not assessed

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
DOI
10.4103/2045-9912.279983
PMC
PMC7871941

Tags

Disease:aging / frailty (37) Delivery:inhalation delivery (196) Mechanism:antioxidant enzymes (423) hydroxyl radical scavenging (352) mitochondrial function (226) oxidative stress (899) reactive oxygen species (774)

Delivery context

In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.

→ Evidence by delivery route

Safety notes

In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.

See also:

Other papers on the same disease / condition