Aside from being an English pronoun, He is the symbol for Helium, element #2 on the periodic table. The New York Times article discusses the uses and limitations around He supply, and is an interesting read. Over the last year, I’ve been on a PhD advisory committee for a student in Prof. Steven Young‘s group in the School of Environment, Enterprise and Development (SEED). His student is researching the “industrial ecology” of He, looking into where it comes from, how it’s used, and where the losses occur in the production, transportation and use. It’s quite an interesting issue, and I’ve learned a few things that might be of general interest.

• We typically think of Helium use in balloons, or perhaps deep sea diving, but the major worldwide uses are in hospitals (for MRIs), specialized welding and manufacturing, and laboratories (for cryogenics or analytical equipment).
• He is collected and purified from natural gas. It is produced during the radioactive decay of uranium in the earth, and collects in pockets of natural gas.
• He is one of the few elements on earth that doesn’t have a “cycle”, like the carbon cycle or nitrogen cycle. That means, once it’s released into the air there is no natural way to get it back because it is so light and inert. It simply drifts away into the atmosphere and eventually leaves the planet.
• He is so “light” (a small atom) that it is notoriously difficult to contain. It easily leaks and diffuses through materials, even solid metals. That’s why your balloon deflates after a couple of days, and why there are a lot of losses of He during transportation and use.

Since He is so important for some specialized applications, like MRIs, there are concerns that we need to conserve it. Also, since it is associated with natural gas, which we’re trying to scale back because of climate change, it may become more difficult to obtain. It occurs in the air at a concentration of about 5 ppm, so someday we may have to extract it from the air, like we already do with another related element, argon (Ar).

So Helium is kind of an interesting and important material. It involves chemical and mechanical engineering (for extraction, purification, and transportation), physics (for cryogenics, MRI and other applications), and industrial ecology (for understanding how it flows through our global economy, and what might happen in the future).