Precursor-free eruption triggered by edifice rupture at Nyiragongo volcano.

Classical mechanisms of volcanic eruptions mostly involve pressure buildup and magma ascent towards the surface1. Such processes produce geophysical and geochemical signals that may be detected and interpreted as eruption precursors1-3. On 22 May 2021, Mount Nyiragongo (Democratic Republic of the Congo), an open-vent volcano with a persistent lava lake perched within its summit crater, shook up this interpretation by producing an approximately six-hour-long flank eruption without apparent precursors, followed-rather than preceded-by lateral magma motion into the crust. Here we show that this reversed sequence was most likely initiated by a rupture of the edifice, producing deadly lava flows and triggering a voluminous 25-km-long dyke intrusion. The dyke propagated southwards at very shallow depth (less than 500 m) underneath the cities of Goma (Democratic Republic of the Congo) and Gisenyi (Rwanda), as well as Lake Kivu. This volcanic crisis raises new questions about the mechanisms controlling such eruptions and the possibility of facing substantially more hazardous events, such as effusions within densely urbanized areas, phreato-magmatism or a limnic eruption from the gas-rich Lake Kivu. It also more generally highlights the challenges faced with open-vent volcanoes for monitoring, early detection and risk management when a significant volume of magma is stored close to the surface.

FeNO levels increase with degree of sensitisation in apprentices at risk of occupational asthma.

BACKGROUND: Atopy has emerged as a major determinant of airway inflammation. OBJECTIVE: To examine whether early markers of occupational asthma increase with degree of sensitisation. METHOD: This study was a prospective follow-up study of apprentices in baking, pastry-cooking and hairdressing during their 2-year apprenticeship. Four visits were conducted to administer a standardised questionnaire, a methacholine challenge test to assess bronchial hyperresponsiveness (BHR) and to measure fractional exhaled nitric oxide (FeNO). Degree of sensitisation was estimated based on the number of positive skin prick tests (SPTs) for 12 common allergens. Mixed-effect models were applied to examine the association between the degree of sensitisation and FeNO levels, BHR and eosinophilic status (more than 3% of cells in nasal lavage fluid). RESULTS: Of the 441 apprentices who agreed to take part in the study, 417 had at least one SPT session providing usable results. Degree of sensitization was related to BHR and FeNO levels. Compared to non-sensitised subjects, FeNO levels were 83% higher (P < 0.01) in highly sensitised subjects and 30% higher (P < 0.01) in weakly sensitised subjects. However, the degree of sensitisation was not predictive of the evolution of these markers. CONCLUSION: Degree of sensitisation is related to early markers of airway inflammation.