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Phosphine is a toxic agent and part of the phosphorus cycle. A hitherto unknown formation mechanism for phosphine in the environment was investigated. When iron samples containing iron phosphide were incubated in corrosive aquatic media affected by microbial metabolites, phosphine was liberated and measured by gas chromatography. Iron liberates phosphine especially in anoxic aquatic media under the influence of sulfide and an acidic pH. A phosphine-forming mechanism is suggested: Phosphate, an impurity of iron containing minerals, is reduced abioticly to iron phosphide. When iron is exposed to the environment (e.g. as outdoor equipment, scrap, contamination in iron milled food or as iron meteorites) and corrodes, the iron phosphide present in the iron is suspended in the medium and can hydrolyze to phosphine. Phosphine can accumulate to measurable quantities in anoxic microbial media, accelerating corrosion and preserving the phosphine formed from oxidation.

The possible liberation of highly toxic and mutagenic phosphine from putrefying media raises the question of its significance as a problem of hygiene. Free phosphine was established by gas chromatography as a universal trace component in gas emitted from the anaerobic biosphere. Sources of phosphine include landfills, compost processing, sewage sludge, animal slurry and river sediments. We detected maximum concentrations in the order of 20 ppb(v/v).

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Background Homologous and heterologous SARS‐CoV‐2 vaccinations yield different spike protein‐directed humoral and cellular immune responses. This study aimed to explore their currently unknown interdependencies. Methods COV‐ADAPT is a prospective, observational cohort study of 417 healthcare workers who received vaccination with homologous ChAdOx1 nCoV‐19, homologous BNT162b2 or with heterologous ChAdOx1 nCoV‐19/BNT162b2. We assessed humoral (anti‐spike‐RBD‐IgG, neutralizing antibodies, and avidity) and cellular (spike‐induced T‐cell interferon‐γ release) immune responses in blood samples up to 2 weeks before (T1) and 2–12 weeks following secondary immunization (T2). Results Initial vaccination with ChAdOx1 nCoV‐19 resulted in lower anti‐spike‐RBD‐IgG compared with BNT162b2 (70 ± 114 vs. 226 ± 279 BAU/ml, p < .01) at T1. Booster vaccination with BNT162b2 proved superior to ChAdOx1 nCoV‐19 at T2 (anti‐spike‐RBD‐IgG: ChAdOx1 nCoV‐19/BNT162b2 2387 ± 1627 and homologous BNT162b2 3202 ± 2184 vs. homologous ChAdOx1 nCoV‐19 413 ± 461 BAU/ml, both p < .001; spike‐induced T‐cell interferon‐γ release: ChAdOx1 nCoV‐19/BNT162b2 5069 ± 6733 and homologous BNT162b2 4880 ± 7570 vs. homologous ChAdOx1 nCoV‐19 1152 ± 2243 mIU/ml, both p < .001). No significant differences were detected between BNT162b2‐boostered groups at T2. For ChAdOx1 nCoV‐19, no booster effect on T‐cell activation could be observed. We found associations between anti‐spike‐RBD‐IgG levels (ChAdOx1 nCoV‐19/BNT162b2 and homologous BNT162b2) and T‐cell responses (homologous ChAdOx1 nCoV‐19 and ChAdOx1 nCoV‐19/BNT162b2) from T1 to T2. Additionally, anti‐spike‐RBD‐IgG and T‐cell response were linked at both time points (all groups combined). All regimes yielded neutralizing antibodies and increased antibody avidity at T2. Conclusions Interdependencies between humoral and cellular immune responses differ between common SARS‐CoV‐2 vaccination regimes. T‐cell activation is unlikely to compensate for poor humoral responses.