Formaldehyde and arsenic — two fun substances

Posted by David Eicher
on Friday, April 08, 2011

Welcome to "Dave’s universe," the new blog by Dave Eicher, editor of Astronomy magazine, and astronomy and science popularizer. I’ll be bringing you new thoughts about astronomy, cosmology, nature, the hobby of astronomy, the sometimes disturbingly pseudoscientific culture we live in, and other miscellany. I hope you’ll enjoy it!

Napoleon Bonaparte — not a friend of arsenic. Credit: Wikimedia Commons
Early this week, we heard about an important discovery by three astronomers at the Carnegie Institution of Washington. George Cody, Conel Alexander, and Larry Nittler issued a press release describing how organic carbon solids found previously in many asteroids and comets likely descended from formaldehyde in the early solar system. This common compound with the formula CH2O is (at room temperature) a gas that’s highly poisonous to humans. So it reminded me of the big story a few months ago that centered on arsenic.

You may recall that in December, several NASA researchers announced they had found bacteria in Mono Lake, California, that incorporated arsenic instead of phosphorus in their DNA. That was explosive news in astrobiology, constituting the first known life-forms using arsenic in that way — a new paradigm of life, and “alien life right here on Earth,” as some news headlines read. But within days, a critical examination of the paper by various other researchers revealed flaws in the research and in the conclusions, and the bacteria from Mono Lake were deemed not so special after all.

In any case, these stories raise interesting points about space, about the interstellar medium around our solar system, and about the neighboring void close to our solar system. Lots and lots of toxic substances are out there, many of them quite close to home, and the universe doesn’t much care whether livings things here on Earth breath our nitrogen/oxygen-rich atmosphere or not. Mother Nature is ambivalent.

There’s a fine line between living with dangerous things in the cosmos and having them kill you. Take arsenic, again. (Well, don’t really take it — just follow along with this example.) All of us have arsenic in our bloodstream — somewhere between 2 and 9 micrograms per liter of blood — and in our bones and hair, too. Despite its notoriety as a killer, arsenic is a necessary trace element in some animals and maybe even in humans. About 100 milligrams of the substance will kill you — lights out. And yet we eat trace elements of arsenic every day, normally up to 1 milligram, in various foods.

Oddly, people who ingest arsenic on purpose can build a tolerance to it. In the 17th century, arsenic eaters of the Styrian Alps ingested as much as 250 milligrams a day twice a week, thinking it helped them work better at high altitude. Chilean villagers in San Pedro de Atacama are immune to arsenic poisoning, in effect, because its presence is high enough in their water supply to have changed their bodies, from day one.

But for most of us, arsenic remains one of the deadliest elements, and one to avoid. Through a complex series of chemical reactions in the body, it disrupts nucleotides and enzymes needed for energy transfer and causes hyper-oxidation in the body; fatal doses quickly cause the shutdown of multiple organs.

We must be quite careful with many substances that are abundant in the cosmos. Napoleon Bonaparte found out the hard way about arsenic, apparently, as scientists found high doses of the element in his hair when they used neutron activation to analyze it. It’s quite possible, maybe even probable, that he was poisoned intentionally while in exile on St. Helena. In any case, many highly toxic elements and compounds were important and abundant in the early solar system and throughout the universe at large. Fortunately, we can gaze out into what would be lethal areas to visit from the comfort of our telescopic eyepieces. And for the time being, at least, Earth itself is still a pretty poison-free place to hang out.

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