2021 Proceedings of the National Academy of Sciences of the United States of America Mechanism / Preclinical Unspecified
2021 · Patterson et al. — H₂ in Antarctic Firn Air: Atmospheric Reconstructions and Implications for Anthropogenic Emissions
Super-Abstract
This is an atmospheric science study — it investigates how levels of molecular hydrogen (H₂) in the Earth's atmosphere have changed from 1852 to 2003, using ancient air trapped in Antarctic snow layers. This study has no relevance to biomedical hydrogen therapy. Molecular hydrogen here is an atmospheric trace gas studied for environmental and climate science purposes.
Commentary
This paper, published in the Proceedings of the National Academy of Sciences, uses firn air (air trapped in compacted but not fully ice-converted snow at Megadunes, Antarctica) to reconstruct 150 years of atmospheric H₂ history. The findings — that atmospheric H₂ rose by approximately 70% over the 20th century despite expected reductions in automotive emissions — are relevant to understanding hydrogen's future role as an energy carrier and its potential environmental impact. The study is entirely outside the domain of biomedical hydrogen science. The only connection to the H₂ medicine literature is the molecule itself. This entry exists in this database likely because of an automated keyword match on H2 — it should not be read as evidence for or against any health application of hydrogen.
Key quotes
- „H2 levels in the southern hemisphere were roughly constant near 330 parts per billion (ppb) during the mid to late 1800s.“ — the pre-industrial baseline of atmospheric H₂ — environmental context only
- „An additional unknown source of H2 is needed to explain twentieth-century trends in atmospheric H2.“ — the key open question: unaccounted H₂ sources in the global atmospheric budget
- „The firn air-based atmospheric history of H2 provides a baseline from which to assess human impact on the H2 cycle over the last 150 y.“ — the scientific contribution: a 150-year reference record for atmospheric H₂ — climate science, not medicine
Our assessment
This paper is not relevant to biomedical hydrogen therapy. It is atmospheric chemistry and climate science. The molecular hydrogen (H₂) studied here is an atmospheric trace gas at parts-per-billion concentrations in Antarctic ice cores — an entirely different context from therapeutic H₂ at dissolved millimolar concentrations or inhaled at percent-level concentrations. This study provides no evidence for or against any health effect of hydrogen. It is included here for completeness of the literature search.
Study design
- Type: atmospheric reconstruction study · n: firn air samples from Megadunes, Antarctica (1852–2003) · H₂ measurement: trace gas analysis of ancient air — not biological
- Result: atmospheric H₂ rose ~70% over 20th century; unknown anthropogenic sources implicated; no biomedical relevance
Abstract
The atmospheric history of molecular hydrogen (H2) from 1852 to 2003 was reconstructed from measurements of firn air collected at Megadunes, Antarctica. The reconstruction shows that H2 levels in the southern hemisphere were roughly constant near 330 parts per billion (ppb; nmol H2 mol-1 air) during the mid to late 1800s. Over the twentieth century, H2 levels rose by about 70% to 550 ppb. The reconstruction shows good agreement with the H2 atmospheric history based on firn air measurements from the South Pole. The broad trends in atmospheric H2 over the twentieth century can be explained by increased methane oxidation and anthropogenic emissions. The H2 rise shows no evidence of deceleration during the last quarter of the twentieth century despite an expected reduction in automotive emissions following more stringent regulations. During the late twentieth century, atmospheric CO levels decreased due to a reduction in automotive emissions. It is surprising that atmospheric H2 did not respond similarly as automotive exhaust is thought to be the dominant source of anthropogenic H2. The monotonic late twentieth century rise in H2 levels is consistent with late twentieth-century flask air measurements from high southern latitudes. An additional unknown source of H2 is needed to explain twentieth-century trends in atmospheric H2 and to resolve the discrepancy between bottom-up and top-down estimates of the anthropogenic source term. The firn air-based atmospheric history of H2 provides a baseline from which to assess human impact on the H2 cycle over the last 150 y and validate models that will be used to project future trends in atmospheric composition as H2 becomes a more common energy source.
Source & links
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