Environmental toxicology of hydrogen sulfide

Abstract

The passenger-carrying paddle steamer Princess Alice was sunk in a collision on the River Thames in 1878 with the loss of over 640 lives and, curiously, may represent one of the largest mass poisoning episodes in history [1, 2]. Raw discharge from the London sewers had been released into the Thames (standard practice at the time) and some survivors reported the unusually foul nature of the water. The extraordinarily high death toll of the Princess Alice accident (> 80%) is in stark contrast to the similarly violent sinking of the pleasure craft Marchioness on the Thames a century later in 1989, where only 51 of 130 people on board were lost (< 40% fatalities) [3, 4]. The Board of Trade inquiry and the Coroner’s inquest at the time of the Princess Alice disaster were primarily concerned with establishing blame for the collision and determining if there were any criminal charges to be filed. That there may have been significant deaths caused by hydrogen sulfide (H2S) inhalation, possibly accelerated by the victims thrashing at the surface, was not given much serious consideration [1, 2]. Nevertheless, it was only nine years after the Princess Alice disaster occurred that the necessary investment was made to treat and separate the sewage before releasing it into the Thames [5]. It has since become entrenched in sanitary engineering lore that many of the Princess Alice deaths were due to poisoning, probably by H2S [6]. While it is now widely accepted that H2S acts as a signaling molecule and exhibits some potentially beneficial therapeutic effects [7–15] at elevated levels H2S is highly toxic. Gaseous H2S continues to be one of the most common hazardous substances attributed to acute poisoning deaths in occupational settings [16]. However, there are still facets of H2S toxicity that remain elusive – including, but not necessarily limited to, a comprehensive estimate of the prevalence of this poisonous gas emitted into the environment and any effects associated with such exposures, the mechanism(s) of its cellular toxicity, and lack of effective antidotes. Herein, we consider some of the knowledge gaps associated with H2S in the environment and its toxic effects on the human body when inhaled.