Greek authorities have ruled out a natural gas leak after a pervasive chemical odor swept across Athens and triggered building evacuations, with scientists now debating whether shipyard operations in the Saronic Gulf or a rare seabed upwelling phenomenon is responsible — and noting the same smell struck the capital in May 2025.
Energy Minister Stavros Papastavrou said emergency crews found no atmospheric breaches after sweeping the city's gas network.
"We can now say with safety that there was no natural gas leak," Mr. Papastavrou told reporters, adding that public safety had not been compromised.
Demosthenes Sarigiannis, president of the National Research Foundation and a professor of environmental engineering, said the odor — consistent with mercaptans, the chemicals used as gas odorants — appeared to have drifted from the sea.
Mr. Sarigiannis outlined two leading maritime theories: metal-cutting operations at the Salamis-Perama shipyards, or a tanker venting cargo tanks at anchor near Aegina Island.
Costas Synolakis, a natural disaster professor at the University of Southern California, offered a different explanation.
Mr. Synolakis argued the incident may have resulted from coastal upwelling — environmental currents pushing toxic, stagnant bottom sediments to the surface — and criticized the absence of localized, empirical monitoring data that would allow a definitive conclusion.
Both researchers agreed the fumes carried no long-term toxicity. Civil protection authorities have reduced their emergency posture but are continuing air quality monitoring, while municipal officials have called for permanent deep-sea surveillance across the heavily industrialized gulf.