February 2022 Issue Table of Contents
In this issue of Elements, we are shown how the four halogens (F, Cl, Br, I) “punch well above their weight” in a whole plethora of Earth and planetary processes, from the atmosphere down to the core. This led me to wonder when each of us first became aware of the role of these trace elements in our daily lives. For myself, it was in childhood. Not necessarily the fluoride in toothpaste, which has greatly reduced cavities, nor iodized table salt, a boon for our thyroids. I was oblivious to such health-related matters as a kid. Rather, it was the intense burning of my eyes that followed countless hours of summer fun in strongly chlorinated public pools. To this day, my Pavlovian response to the pungent smell of bleach is a fond flood of childhood memories.
With respect to Br, I was not meaningfully introduced to the term “bromide” until I was an undergraduate at UC Berkeley. Not in chemistry lab, but rather in a Comparative Literature course. The term “bromide!” was scrawled in red, repeatedly, all over my essay on Moby Dick. Apparently, my deep, philosophical musings on Ahab’s obsessive quest were found to be “trite and unoriginal”. Oh dear! A wellearned, if stinging, instruction on how Br-bearing sedatives (no longer available due to their toxicity) entered the English lexicon to refer to boring and meaningless expressions, in large part due to Gelett Burgess’ 1906 essay, Are You a Bromide?
Although bromine solutions were not a feature of my undergraduate chemistry labs, there was plenty of hydrochloric acid (HCl) to be had. It was not until graduate school that I became familiar with the more dangerous halogen acid, HF. Although the weaker of the two acids, it is that very trait, namely HF’s low dissociation constant, that enables it to penetrate tissue (i.e., skin, eyeballs, lungs, etc.) as a neutral lipid-soluble molecule, where it can then do significant damage. As part of my pursuit of silicate-melt density data, I spent hundreds of days in the late 1980s cleaning out silicate-coated platinum crucibles with vast quantities of HF. This was an era when laboratory safety protocols were nowhere near what they should have been. Although I carefully donned a flimsy (and ineffective) pair of vinyl gloves when handling the HF, I watched my PhD advisor cavalierly and deftly work with the stuff with bare hands. Now, my graduate students and I don fullblown hazmat attire when using HF in quantity: goggles, face shields, HF-protective aprons, thick gloves (which unfortunately reduces our dexterity when handling small beakers), gaiters, the lot. Those safety videos that feature severe HF burns are effective!
The 1980s was also when many of us became increasingly aware of the problem with chlorofluorocarbons (CFCs) and their destructive impact on Earth’s protective ozone (O3) layer, subjecting all forms of life to dangerous levels of UV radiation. A decade earlier, the Molina and Rowland (1974) landmark paper predicted the breakdown of CFCs in the stratosphere and showed how one measly chlorine atom can efficiently destroy over 100,000 ozone molecules.
Cover Image from Are You a Bromide? (Burgess 1906)
But scientific papers, even when they lead to Nobel prizes, do not move public opinion. What caught most people’s attention was the actual discovery in 1985 of a large ozone “hole” over Antarctica, which had formed far more rapidly than scientists had predicted. That the unrelated Chernobyl nuclear accident occurred the very next year may have contributed to public alarm over the ozone hole, owing to the frightening resonance the term “radiation damage” has in the collective public imagination, whatever the source – nuclear or solar.
Global action on curbing CFCs with the 1987 Montreal Protocol was surprisingly swift and united. It appears that two factors drove sustained success in healing our ozone layer in the ensuing decades: i) widespread public alarm and ii) business opportunities to profit from CFC substitutes. Many have asked if the recipe for success in curbing CFCs can be applied to greenhouse emissions and our unfolding climate crisis.
Perhaps there are thin silver strands of hope that can be gleaned from otherwise dark news headlines over the past year. The sheer number of record-breaking, climate-related disasters has left virtually no part of the globe unscathed and it’s going to get a lot worse. Has the devastation been enough to move public opinion on the urgent need to transition from fossil fuels? Or is more suffering required? With respect to profitable green technologies, it is noteworthy that today’s richest person in the world (and in history) vaulted to that status just last year due to the success of Tesla’s electric cars. Some news headlines suggest that high-temperature fusion power plants may be attainable within a decade or two; others feature transformative, cheap methods to store energy (e.g., Form Energy; Energy Vault). Even if these specific examples don’t quickly come to fruition, at least substantial investment in green technologies is accelerating. As noted by Euripides, “Nothing has greater strength than dire necessity”. (Oops, I hope that’s not a bromide!)
Burgess G (1906) Are You a Bromide? or, The Sulphitic Theory. B. W. Huebsch, New York, 63 pp
Molina MJ, Rowland FS (1974) Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone. Nature 249: 810-812, doi: 10.1038/249810a0