A View to a Kill in the Morning: Carbon Dioxide

By Deborah Blum 

In 1940, inspired by a tragic accident, a New York pathologist came up with the scenario for a perfect murder.

His idea was based on the deaths of five longshoremen, their bodies found in the cargo hold of a steamer docked on the East River. The boat had been carrying cherries from Michigan. The men had been bunking in the room where the fruit was stored and to the shock of their co-workers, as they started to unload the cherries, all five were found lifeless in their beds.

When investigators from the New York City medical examiner’s office arrived, they discovered that the fruit had been chilled by placing large containers of “dry ice” in the storage area. Dry ice was, of course, not ice at all but carbon dioxide (CO2) in its solid form, resembling breathtakingly cold chunks of frosted glass. At standard atmospheric pressure, water (H2O) freezes as temperatures slip just below 32 °F. Carbon dioxide solidifies (a process called deposition) at −109.3 °F.

As it warms – say, as it sits in a fruit storage area – it begins returning to its gaseous state, a transition known as a phase change. The solid chunks shrink without the seeping wet of melting water ice, hence the name dry ice (patented in 1924 by the DryIce Corporation of America). Instead there is a steady seep of gas in the surrounding air. Mostly this is nothing to worry about - unlike its chemical cousin, carbon monoxide (CO), carbon dioxide is not acutely poisonous – and, in fact, the chilly vapors lifting off dry ice have been used to create a fog effects in places ranging from theatres to Halloween parties.

But there is a risk. Carbon dioxide is denser than oxygen-rich air and can, notably in confined spaces, essentially displace the breathable atmosphere, settling into its surroundings like an invisible but suffocating blanket.

And this is what the city’s medical examiners realized had happened to their dead longshoremen. The men’s blood was “saturated with carbon dioxide and the men had obviously died from asphyxia,” explained assistant medical examiner Edward Martens in his 1940 book, The Doctor Looks at Death.

Still, he added, finding CO2 in the blood went only part way to solving the puzzle. Carbon dioxide is always naturally present in human blood. It’s a byproduct of the way we metabolize oxygen and as it builds up, we exhale it away. If a person is murdered by suffocation and cannot exhale, the gas also builds up in the blood: “Exactly the same autopsy picture would have been found if the men had died from being smothered by holding, say, a pillow over their mouths.” 

“This brings up a rather interesting possibility for a method of murder that would be extremely difficult to detect,” the doctor, Edward Marten, continued. “I pass this on, for what it is worth, to writers of detective stories.” In his scenario, a sleeping or heavily intoxicated person slumbers in bed. The killer places a bucket, packed with dry ice, on the floor, shuts all windows, and closes the door tightly as he leaves. Within a few hours, the victim suffocates. When someone else opens the door, normal air refills the room, whisking away all trace of the murder weapon: “The trick is that when dry ice evaporates it leaves absolutely no trace behind, so that the investigating detectives would find nothing except a dry and completely empty pail.”

Still, Marten considered that a better tip for fiction writers than real-life killers. The purchase of dry ice was easy to track, the material so cold as to bring on frostbite if handled improperly, and an ideally airtight room almost impossible to find. And someone, after all, might wonder about that peculiarly placed empty pail. 

Nevertheless, I’d like to take this moment to pay tribute to carbon dioxide, as one of the most important – and dangerous- gases on the planet. We tend to discount its lethal potential by contrast with its toxic chemical cousin, carbon monoxide (CO). Thanks to its ability to block oxygen circulation in the blood stream, carbon monoxide drifting from faulty heaters, generators, cars accidentally left running, furnaces and other fuel-burning machinery is estimated to kill some 500 people in the United States every year and send thousands of others to doctors and hospitals.

And we tend to discount carbon dioxide as an actual poison because we’re focused instead on all the other ways it can – and does - cause trouble. These days, its best known as a greenhouse gas, for its ability to trap heat in the atmosphere. Numerous studies have found that levels of CO2 have risen steadily due to human activities – ranging from industrial burning of carbon-rich fuels to deforestation to agricultural practices. The U.S. Environmental Protection Agency estimates, for instance, that in 2005, “global atmospheric concentrations of CO2 were 35 percent higher than they were before the Industrial Revolution​.” Although other gases are also linked to the current scenario of human-induced climate change, carbon dioxide is considered by many to be the most important factor.

Of course, even that doesn’t really give full credit to the ways that carbon dioxide can alter the environment. For instance, scientists calculate that our oceans absorb a good proportion of the gas generated by human activities. Unfortunately, when you dissolve CO2 into H2O you rather logically end up with the compound H2CO3, better known as carbonic acid. If you don’t recognize it, it’s the rather weak acid found in carbonated soft drinks (although not so weak that countless middle school students haven’t studied its corrosive effect on everything from teeth to lug nuts).

It’s not surprising, then, that marine biologists have expressed alarm about the increasing acidification of the oceans. One recent report I found examined increases in carbonic acid levels on California mussels, finding a notable thinning of their shells and a decrease in their overall size. A study conducted by Norwegian scientists also found that overall that mussel larvae decreased in size, but suggested, hopefully, that the effects might be mitigated if, as seemed probable, only the larger larvae would survive. Of course, mussels aren’t far from the only species at risk, as a National Science Foundation​ report concluded recently, listing everything from coral to marine algae. This is just another way of saying that we’re deep into a global chemistry experiment with one of nature’s most important – troublesome and occasionally lethal – chemical compounds.

There are many reasons, in fact, why we should regard carbon dioxide with respect, if not wariness. And, certainly, one finds that kind of response at a subconscious level. A rather fascinating experiment a couple of years ago found that just inhaling a small amount carbon dioxide triggered a fear response in mice. And there’s an equally fascinating wealth of research about the relationship between human panic disorders and CO2 inhalation. Far beyond my New York murder scenario, there’s rather horrifying evidence that occasionally this can be a panic-worthy gas.

The best example of that comes from a real life event, a catastrophic natural release of carbon dioxide in Lake Nyos in Cameroon during the summer of 1986. Beneath that beautiful lake, geothermal seeps release CO2 into the deep lake waters, normally trapped near the bottom by pressure and cold. But in this case, apparently, the lake became oversaturated with the gas and on August 21, 1986, the lake waters effectively turned over, carbon dioxide fizzing explosively upward, the waters of Lake Nyos turning a startling red as iron deposits were stirred about. The rapidly released gas settled in a suffocating layer into the valleys around the lake. So many people died – an estimated total of 1,746 – that eventually the website Snopes.com felt compelled to investigate. Snopes reported that the event was real and, in fact, not the only case of suffocation deaths due to carbon dioxide seeps at lakes in Cameroon. Since that time, in fact, measures have been taken to maneuver the gas out of the lakes. 

And this, of course, brings me back to plotting a CO2 murder. I discovered Martens’ theory and his long out-of-print book while researching early 20th century forensic toxicology a few years ago. At first, I just liked the improbability, a medical examiner cooking up a supposedly unsolvable murder. But what’s stayed with me is the implicit message –that we’re talking about a dangerous compound.

It’s a message to remember as we move deeper into our global experiment in greatly increasing the amount of carbon dioxide in our environment. For those who haven’t taken the experiment seriously – in my opinion, still far too many – it’s a reminder that they should start doing so now. And for those who need no reminder of the bigger carbon dioxide picture, I think I can still pass along at least one useful tip - in case of strangers bearing buckets of dry ice, sleep with your windows open.

photo credits: http://www.flickr.com/photos/dherholz/5886706782/ (smoke)

http://www.flickr.com/photos/bryanchan/327644305/ (dry ice blocks)


(window) http://www.flickr.com/photos/chiotsrun/5843798932/


(earth) http://www.flickr.com/photos/randomcliche/2537646816/

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The Lost Girls

by Deborah Blum

Winter is the season of carbon monoxide poisoning, unfortunately. Every year about this time, public health officials and poison control centers sound the warning. "Carbon monoxide threat grows as winter nears," announced a news story from Maine this week. "Avoid carbon monoxide when heating your home," echoed one from Arizona. Still, not everyone hears these messages and takes protective measures. Far too often we see stories like this one from California: "Three hospitalized with in-home carbon monoxide poisoning." Or even worse, this headline from Indiana: "2 South Bend men die of carbon monoxide poisoning." So, as a reminder to us all that this is a very dangerous gas, I'm reprinting my favorite post on carbon monoxide from my chemistry and culture blog at the Public Library of Science, Speakeasy Science. Its original title was "Poison in the Night," and when you read it, you'll see why.

There it was, the sound of an engine, that low, steady grumble. The little girls heard it, and they told their mother. They were just 11 and 12. "You parked the car in the garage and it's still running," they said. But she told them they were wrong. "Oh, no," she said, "it's just the fan cooling down the motor. It's a big car, you know, and it gets hot."

Nothing to worry about. Not even worth looking at. So, the little girls gathered up some snacks and went to watch a movie, giggling the way you do with your best friend. They were having a slumber party at the 11-year-old's home, after all. The mother went to bed, sleeping away the soft May night. The car kept running. A Ford Escape, with a big gas tank to burn, keeping up that low growl in the closed garage, the rumble in the dark.

In the morning, the mother woke up feeling sick, dizzy, disoriented, knowing that something was wrong, and that the air itself was wrong. She reached for the phone and dialed 911, calling for help. She went into the garage and there it was, the running car. She turned it off, investigators say, threw the keys on the kitchen counter and stumbled into a shower stall to wait for the rescuers.

The house was quiet when the rescuers arrived and the air was wrong. They had to go back outside to gear up, put on their protective masks and oxygen tanks. They took the mother away and saved her at the hospital. But the little girls stayed behind. One lay on the kitchen floor, the other on the carpet in the family room. Still as death in that all-wrong air. The families buried them side by side in a cemetery. They were best friends, you know, in Boca Raton, Florida, where they lived.

The mother tried to make it different, to at first change the story. She was afraid; she couldn't bear it. The car was defective, Loretta Wilson told the police. She couldn't turn it off and she didn't realize that the garage vented into the house, too close to the family room where the little girls were laughing and watching that movie. But the police tested the car. It clicked on and off perfectly, like the good machine it was. Slowly, slowly they coaxed the whole story out. The way her daughter Amber had asked her about the running car, the way she'd turned away. Almost six months later, in December of last year, they charged the mother with manslaughter, or culpable negligence, in the deaths of the little girls, Amber and her friend, Caitlyn Brondolo, side by side now in the warm Florida ground.

If there had been a trial, there were too many things that a prosecutor could have said. He could have said that we've known, almost since the invention of the internal combustion engine, that fuel does not burn perfectly in such machines. That among the byproducts of that imperfection is the gas carbon monoxide: colorless, odorless, deadly. That it comes from such a simple formula, just an atom of carbon and atom of oxygen needed to make a CO molecule. And, that it kills simply, too. It just binds to the proteins in our blood that carry oxygen, muscling that life-sustaining gas out of the way. That carbon monoxide suffocates the body as it saturates the bloodstream. The federal government estimates that it kills about 500 people a year and sickens more than 15,000. We've known for a good hundred years or more that people die from letting carbon monoxide seep into an enclosed space. Not just any people, the faceless numbers, but friends and lovers, husbands and wives, our sons and daughters.

"Ultimately, this difficult case is about an assignment of responsibility," Palm Beach County state attorney Michael McAuliffe wrote in a statement for the public. "While no evidence exists that Ms. Wilson intended to harm the children, this tragic event reinforces the unwavering principle that parents and guardians of children have the paramount responsibility to protect their children and those in their custody."

The mother pleaded guilty on December 19, 2009, the day after she was arrested. A judge sentenced her to five years probation, psychological counseling, and community service through educating others about the dangers of carbon monoxide. The case itself was enough to remind anyone to install carbon monoxide detectors, check leaky gas appliances, keep their families safe. But the mother with her guilt and her grief and her daughter gone to the warm ground, no one could be untouched by that. She could help keep others safe. So they thought, so they hoped.

That is, until this summer drew to its end and they tallied the numbers in Palm Beach County. Last year, in all of 2009, four carbon monoxide poisonings, including the mother and the lost girls. This year, so far, 28 poisonings and three dead. One death from a boat left running in a boat house. Two dead from--yes, unbelievably, but yes--cars left running in closed garages. A 29-year-old woman who forgot to turn off her Lexus. An elderly man who didn't remember that his Lincoln sat rumbling in his garage while the air in that house went wrong. Six rescuers who went to his house were sickened by that poisoned air; the levels, so they said, measured 150 times above safe.

As if we are ever safe. Still, experts puzzled over why this was happening. Maybe, one said, we just haven't persuaded enough people to buy carbon monoxide detectors. The old man didn't have one, did he? Nor the young Lexus owner, nor the man with the boat. But, why not? Why not install some common-sense protection after a hundred years of knowing that we do leave cars idling, that gas appliances do leak, that carbon monoxide is a silent drift of poison in the air, and that people do die.

The mother could have answered that one, maybe. She could have told them that you don't need the detector because you're so sure that it will never be you. The poison gas is always destined elsewhere. You just know it will seep into someone else's life--odorless, colorless, unrecognized. So, when you hear that low growl of warning in the garage, and when the little girls ask, you just laugh, tell them it's nothing, send them off to watch a movie, and let yourself drift to sleep while the night closes in around them.

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