How the Department of Aerobiogeoindustriocosmomicromorphology Got Its Name and What It Can Teach Us About Particle Identification

One evening, while my daughter was doing her before-bedtime reading, she encountered the longest word in the English language, pneumonoultramicroscopicsilicovolcanokoniosis, and asked if I knew the word. As I glanced over her shoulder, I noticed the spelling contained “microscopic” among all the other familiar bits of words strung together. This word reminded me of a sign that used to hang on the door of John Gustav Delly’s office at McCrone Associates that read “The Department of Aerobiogeoindustriocosmomicromorphology.” Perhaps not an official word, although it does appear in print in the first edition of “The Particle Atlas”. Interested in the word’s origin, I asked John how he went about constructing the word.

Dust in the Wind

John derived the word when air pollution in the United States was a top concern for lawmakers—a time prior to the beginning of what would eventually become the Environmental Protection Agency (EPA). The word’s derivation begins with the first four letters, aero (air), followed by bio, geo, industrio, and cosmo, which represent all types of particles that can become suspended in the air as dust and later settle-out onto surfaces, many times showing up as microscopic contaminants.

For someone new to the field of particle identification, how might one begin to learn to identify such a vast array of materials and is there a model a newly trained microscopist can look to for guidance? Going back to the first edition of “The Particle Atlas” where Delly’s all-encompassing microscopical word was first published, we find the answer in the book’s preface.

Child’s Play

James P. Lodge, Jr., from the National Center for Atmospheric Research, assures us anyone can become proficient at particle identification and makes the case that most particles you’ll encounter in a microscopic sample occur more frequently than others. Below is from the preface of The Particle Atlas:

“The task of classifying particles in the microscope might seem impossible. One of my children said recently at dinner: “But there must be millions of different kinds!” The truth is that a rather small number of species make up nearly 90 percent of the particles in our urban atmospheres. Indeed, the same child can distinguish among more than a thousand friends and acquaintances, several score make and models of automobiles, the dramatis personae of several dozen television programs, an enormous variety of foodstuffs, and the scenery of a half a hundred ski slopes. Her mind and hands recall the fingering of four different musical instruments as her eye discriminates the notes. Learning to discriminate a few hundred substances under the microscope would tax her little: she nearly knows that many wildflowers.”

Lodge’s reasoning is based on a frequency of occurrence learning model, the same model commonly used by beginning students in foreign language courses.

Totally Greek-ed Out

Most language learning programs begin with learning the most frequently occurring words: those appearing most often in non-fiction literature. Using the textbook “Basics of Biblical Greek” by William D. Mounce as an example, the author lays out the strategy of learning Biblical Greek by using a frequency of occurrence model.

Below are some of Mounce’s foundational principles to guide the student:

“There are 5,437 different words in the Greek New Testament. They occur a total of 138,162 times. But there are 313 words (5.8% of the total number) that occur 50 times or more. In addition, for special reasons you will be asked to learn six more words that occur less than fifty times. These 319 words account for 79.92% of the Greek New Testament. For example, καί (the word “and”) occurs 9,153 times. Learn that one word and you know 6.7% of the total word count.”

The figures used by Mounce are close to those discussed by Lodge. A few hundred words (313) account for eighty percent of the total words.

In keeping with the Biblical Greek analogy, I asked around the lab to see what our microscopists thought the particle equivalent would be for the word “and” (καί)? The general response was cotton/cellulose.

In addition to cellulose fibers, the list of other frequently occurring particles grew to include quartz, calcite, titanium dioxide, pollen, starch, skin cells, spores, diatoms, hairs, fibers, etc. If carried to its logical conclusion, one would likely end up with a collection of particles very much like the reference set we use to teach our polarized light microscopy course.

Sets and Reps

Today, finding prepared set of particles like the one above can be challenging. Over the years, McCrone Microscopes & Accessories has sold many thousands of the one-hundred particle references set, so you may have one kicking around your laboratory somewhere. Of course, you can always make your own reference set using the list of particles above as your guide.

If you are not into the DIY approach of slide making, there are sets of prepared slides made by Cargille Laboratories, which cover a similar range of particles like our teaching set.

Below is a list of the eleven Cargille particle reference sets. Each set contains 25 particles:

1. Man Made Fiber Reference Set
2. Common Hairs Reference Set
3. Common Rock Minerals Set
4. Commercial Fibers Reference Set
5. Commercial Fur Hairs Reference Set
6. Elementary Minerals Reference Set
7. Commercial Minerals Reference Set
8. Light Transmitting Minerals Set
9. Metallic Minerals Reference Set
10. Starches and Food Condiments Reference Set
11. Supplementary Minerals Reference Set

Cargille Total = 225 Particles

Adding up the number of prepared particles in the Cargille sets to the list of samples in our one-hundred particle reference, you arrive at approximately 325 particles give or take, close to our 319 Biblical Greek number and Lodge’s “few hundred” estimate. There is some redundancy between the collections, but I think that’s okay. I like the idea of comparing like-particles from different sources to note any subtle variations within a group.

With our reference sets in hand, there are a couple of ways to go about becoming an aerobiogeoindustriocosmomicromorphology microscopist. You can either take on this task by yourself or with a work colleague.

Going it Alone

Let’s first look at the idea of going it alone. For some real-world insights into how this might be accomplished, I recommend you check out our webinar “Robert’s Rules for Contaminant Identification” by Robert Carlton. During Carlton’s presentation he comes up with his own list of frequently occurring particles found in the pharmaceutical industry and shares a clever way of employing self-directed learning while doing project work:

“I nearly always padded my contaminant work with an hour or two of skill development… I might have spent an extra hour learning a little bit more, testing a few other samples, practicing my sampling skills, etc. What I found is that it’s always easier to justify a little extra time on a particular contaminant than it is to try to devote a whole or half day to building your skills.”

Characterizing a particle or two from your particle reference set while doing contaminant work sounds like time well spent.

Study Buddies

In the early days of McCrone Associates, Dr. McCrone would leave unlabeled microscope slide preparations on microscopist’s stages, referring to them as UFOs. You would be expected to characterize the material to the best of your abilities and then try to identify the unknown. Alternatively, with your prepared reference sets, you can take a standard size Post-it® and cut the top part that includes the adhesive portion into three small squares, approximately the size of the microscope slide label.

In the above figure, I created a text box in a PowerPoint slide, and spaced the abbreviation “UFO” in three equally spaced positions along the top of the text box. I then printed the PowerPoint slide with the UFO text box onto a piece of paper and placed a Post-it on top of the textbox and ran the same piece of paper with the Post-it through the printer. The Post-it was then cut into three equal size pieces and trimmed to the dimensions of a standard microscope slide label.

By covering the labels of each prepared microscope slide in your reference set with the UFO tag, you can test yourself to see how your aerobiogeoindustriocosmomicromorphology skills are coming along.

Diminishing Returns

What about studying more particles beyond the few hundred listed above? Would learning more particles be of benefit, or is there a point of diminishing returns? Below is what Mounce thinks about this concept regarding learning Biblical Greek:

“We feel it is counterproductive at this point to learn more (words) unless you really like doing things like that. Your time is better spent reading the Bible or learning grammar.”

Similarly, a new particle analyst can spend their time away from the microscope learning about the microscope’s optics and accessories, conoscopy, contrast methods, seminal works related to particle identification, and other technical aspects of the craft rather than learning to identify more particles, at least in the early stages.

With the aerobiogeoindustriocosmomicromorphology road map laid out, I will leave you with some words from one of the world’s greatest particle microscopists, John Gustav Delly. Delly writes in the Postscript of his book “Essentials of Polarized Light Microscopy and Ancillary Techniques” some words of wisdom to the student: “You have learned that your polarized light microscope is much more than a glorified magnifying glass; it is your vehicle to a wonderful world in which the language spoken is light.”