Hydrogen sulfide — a gas that smells like rotten eggs — can be insidious in its lethality. Its odor will be unmistakable to its victim. But the gas can quickly numb the sense of smell, leading to the belief that the threat has passed. Unconsciousness and death can follow. Even at tiny amounts — parts per billion — research has suggested there might be an impact on people living in an affected area. A 2001 study by UTMB researchers looked at residents in Odessa, where ponds of industrial wastewater were emitting hydrogen sulfide gas. The researchers said they found people suffering from disorders like dizziness and shortness of breath. And while stopping short of a definitive link, the researchers wrote: “… our results, providing evidence of the elevated prevalence of adverse health symptoms in communities potentially exposed to low levels of H2S (hydrogen sulfide), emphasize the need for further studies on the effects of this toxin.”