In 2002, two workers died in Des Moines after being overcome by hydrogen sulfide fumes as they worked on a sewer project. Any livestock farmer knows that if the ventilation fails in a hog confinement, both the pigs and any workers in the building are in danger of suffocating from the hydrogen sulfide that comes off decomposing manure in the pits below the hog slats.

Now, researchers at Iowa State University are investigating long-term neurological damage caused by hydrogen sulfide, which can also come from swamps and industrial processes.

Wilson Rumbeiha, a professor of veterinary diagnostic and production animal medicine, said the poisonous gas affects the respiratory and cardiovascular systems and the brain.

Rumbeiha’s research focuses on those who survive hydrogen sulfide poisoning. He wants to know what the long-term consequences are. The exposures can cause symptoms that don’t show up for months.

Rumbeiha recently received a two-year grant from the National Institutes of Health to study the long-term risks associated with exposure to the gas and to test a drug that may pave the way to a therapy in humans. Rumbeiha is working with personnel at the University of California, San Diego.

Hydrogen sulfide gas can form naturally in marshes, volcanoes and sewers. It’s also a byproduct of some industrial and manufacturing processes, such as oil and gas production.