Elephant Seals Give Scientists a Clue about Carbon Monoxide

New research involving elephant seals has furthered scientists' understanding of carbon monoxide's natural characteristics and limitations.

Carbon monoxide (CO) is a colorless, odorless "silent killer," but what few may know is that the toxic gas is produced naturally in small quantities in humans and animals. The deep-sea diving elephant seal is one of these animals that can tolerate the poisonous substance.

In the human body at least, CO is produced naturally as a byproduct of the breakdown of hemoglobin - molecules responsible for transporting oxygen - inside red blood cells. About 1 percent of the hemoglobin inside healthy human adults is linked with CO. It becomes dangerous when CO levels are too high, and they bind with the hemoglobin and prevent it from distributing oxygen throughout the body.

The US Centers for Disease Control and Prevention estimates that at least 430 people die each year from unintentional CO poisoning.

CO is found in fumes produced by furnaces, vehicles, portable generators, stoves, lanterns, gas ranges, or burning charcoal or wood.

But elephant seals don't have to worry about this. As described in the Journal of Experimental Biology, elephant seals have the highest blood volume of any mammal and are renowned for their extreme diving proficiency. They are so adept at deep-sea diving because, like other efficient divers, they conserve oxygen and save it for their vital organs - the heart, brain and lungs - by shutting off blood flow to peripheral areas of their body.

Researchers at Scripps Institution of Oceanography at the University of California, San Diego were surprised to find that elephant seals harbor 10 times more CO in their bodies than humans do - that's the equivalent to someone smoking 40 cigarettes a day.

"We found that the elephant seal is able to reach incredible depths, apparently with lots of carbon monoxide, so these results are helping us find answers for the rates at which you can expose organs and tissues to this gas," co-author Michael Tift said in a statement. "The elephant seal is giving us the big picture of which concentrations of carbon monoxide might be the most beneficial."

In recent years, medical researchers have even evaluated the gas as a treatment for diabetes, heart attacks, sepsis, and other illnesses.

"Carbon monoxide is toxic and deadly at specific levels, but at low concentrations it may actually be therapeutic and beneficial by playing a crucial role in protecting us," Tift noted.