Whenever a farm with odor problems makes headlines, what's causing the pollution is usually a single, colorless emission: hydrogen sulfide gas.

It smells like rotten eggs. At high enough concentrations, it makes your eyes burn and water, makes you dizzy and nauseated, makes you forget things, makes your lungs hurt. It's heavier than air, so it tends to hang around for a while, and as it does, it deadens your sense of smell. At even higher concentrations (we're talking enclosed rooms, not farm odors drifting by), you black out, you go blind. Eventually, you die.

Hydrogen sulfide, also known as "sewer gas," is a byproduct of decomposing organic matter – mostly human and animal waste. Occasionally it's a byproduct of activities like oil refining (which is why the air on U.S. Highway 52 in Rosemount, near the Flint Hills refinery, occasionally smells like rotten eggs).

It's pretty awful stuff. It also occupies an increasingly curious place in science. Recent studies suggest that while it's very good at killing us, it can also save our lives and possibly even help us live longer.

Low levels tolerated
That's because the funny thing about hydrogen sulfide is that it occurs naturally in the environment and in our bodies — we're built to tolerate low levels of it for a lifetime without adverse effects, and it helps us regulate body temperature and metabolism.

Take this study. It says that a low-dose injection of hydrogen sulfide during a heart attack could prevent tissue damage caused by the rapid changes in oxygen levels – which plummet during an attack, then shoot back up upon resuscitation.

There's this study, which used hydrogen sulfide to put mice in a state of suspended animation. Their cells practically stopped moving, they hardly breathed, and their body temperatures dropped. When they received fresh air, they woke up as if nothing happened.

There are some wild possibilities for this if it works on humans — space travel, for instance — as well as some practical ones, like hibernating injured troops or people with spinal-cord injuries until they can be transported to a hospital.

Eventual mass extinction?
Suspended animation, though, won't save us from a mass extinction caused by hydrogen sulfide, which is what paleontologist Peter Ward says might happen if global warming continues.

If you believe him, it caused up to a dozen mass extinctions millions of years ago (except for the dinosaurs) and now, because of climate change, threatens to again.

And climate change might be an even bigger problem if hydrogen sulfide works the same way in humans as it does in nematode worms.

It's not as big of a stretch as it sounds, because the worms' nervous systems and other functions are remarkably similar to humans'. In this study, worms living in a controlled atmosphere with low concentrations of hydrogen sulfide lived longer than worms in regular room air, and when the groups were moved to a higher-temperature environment (equivalent to a sweltering August day in Minnesota), the hydrogen sulfide worms lived eight times longer.

The idea that hydrogen sulfide might be our long-awaited fountain of youth is a beautiful, promising idea, except for just one thing (besides the climate change, of course).

We'd have to put up with the smell.