Domino effect: An unusual case of six fatal hydrogen sulfide poisonings in quick succession.

Hydrogen sulfide (H2S) is one of the most serious toxic gases encountered in forensic practice. Aside from being a by-product of many industrial processes, this gas is naturally produced during the putrefaction of organic substances. We report six autopsy cases of fatal H2S poisonings from inhalation of H2S gas after an occupational accident. These six men died during the unblocking of a wastewater cistern. The first worker died shortly after clearing the obstruction, the other five died, one by one, as they attempted to help their colleagues. The macroscopic and histological findings are discussed here to provide useful information for future cases. Greenish discoloration of the skin and of internal organs (liver, trachea, esophagus, stomach) was observed, and one case showed signs typical of drowning. We present a very unusual incident, complete with rare photographs and toxicological analysis. In these cases, based on both macroscopic and microscopic findings, the cause of death was most likely an inhibitory effect on cellular cytochrome oxidase causing respiratory failure.