A mundane industrial mineral, Potter’s Rot, a Renaissance polymath, and climate change; what could these things possibly have in common? More than you might think. Lets start with that can of old talc (as in talcum powder).
The can had been sitting on a shelf in my wife’s pharmacy since at least the early 1990s. It looked much older than that (in my world, old equals cool). The wife thought it had been around since the hospital was built in the 1960s (translation: since hippies and Richard Nixon roamed the Earth). Produced by a well-known pharmaceutical company, it was labeled, simply, “purified talc.” Talc is a mineral. Not a particularly rare mineral but interesting. It’s related to micas and clays and widely used in ceramics, cosmetics, and, yes, pharmaceuticals. The wife patiently explained that it was used as a binder for compounding custom prescriptions. Curiosity got the better of me and I asked if I could have what was left in the can. The dear wife said yes, but she wanted the can back. I did say it was cool looking.
I took the gray powder back to my lab. I look at rocks and minerals using with x-rays. That surprises people sometimes. I don’t image them the way a dental x-ray would, rather I look at how the atoms in the sample bend the x-ray beam (called diffraction). This tells me something about the structure, or framework of the mineral. Lots of different minerals share the same chemical elements, but each has a unique structure-its “DNA.” The x-ray scan would tell if the stuff was actually talc, and if it was just talc or other stuff too. Not surprisingly, I found that the talc was talc, but it also had another mineral mixed with it: chlorite. This isn’t unusual as chlorite forms in the same environment as talc, and shares a similar chemistry. However, it casts doubt on the “purified” label. Of course, at the time it was produced it may have been pure enough.
Why my curiosity? The talc reminded me of a lab exercise I assigned to my Forensic Geology class. It involved analyzing various cosmetics. Cosmetics and paints are made mostly of various minerals. One brand of cosmetics they examined advertised that they were “So pure you could sleep in It.” and “free of chemicals, talc, fragrance…” you get the idea. I was curious about what minerals they did use, and why talc was considered bad. My students found three minerals in this particular brand, one being chlorite (we’ll ignore the other two for simplicity). Recall, chlorite is in the same broad family of minerals as talc (cousins if you will). Why did they substitute chlorite for talc? Was talc really unsafe? As it turns out, it depends.
Most people have heard of silicosis, which is an occupational lung disease caused by inhalation of crystalline silica dust and has been recognized since 1705. Bernardino Ramazzini (1633-1714) first observed silicosis in the lungs of stonecutters. The condition was known informally as Grinders Disease, or, wait for it-Potter’s Rot. Ramazzini is recognized as the father of occupational medicine. He was the first to document that repeated exposure on the job to dust, chemicals, repetitive motion, etc., could cause harm where casual exposure to the same things did not.
So, is talc hazardous? Turns out that there is a condition similar to silicosis known as talcosis, which is connected with exposure to talc dust from mining or processing talc products. Ramazzini again. A National Toxicology Program report (1993) reported that cosmetic grade talc caused tumors in lab rats forced to inhale talc for 6 hours a day, 5 days a week for 113 weeks. Maybe that cosmetics company was on to something. I dug a little deeper and found that, despite this study, the FDA had concluded that routine, or cosmetic exposure to most talc products was safe. Why the apparent contradiction? Remember the poor rats: 6 hours a day, 5 days a week, 113 weeks. That isn’t “cosmetic” exposure, that’s unprotected occupational exposure.
Now, let’s call in our Renaissance polymath: Phillip von Hohenheim (1493-1541). Better known as Paracelsus. He was botanist, alchemist, astrologer, philosopher, occultist, and physician. The guy even has a Facebook Page! He is also widely recognized as the father of toxicology. He’s famous for stating: “All things are poison and nothing is without poison, only the dose permits something not to be poisonous.” Its not so much what you are exposed to, but how much you’re exposed to that makes the difference. Wearing cosmetics containing talc, or using talcum powder after a shower, is not likely to cause problems. Work in talc mine or as a stonecutter for 40 years and talc, quartz, just about any dusty material, may become toxic. Something Ramazinni would write about 200 years later.
This brings me to carbon dioxide. The EPA recently declared that CO2 in the atmospheric was a threat to human health. Essentially defining it as a pollutant (which has big economic and health ramifications). This may sound odd, but its really not. Currently CO2 concentration in the atmosphere stands at 387 parts per million (by way of comparison, above 10,000-ppm and it gets toxic to humans). Despite its low concentration, it is vital for, among other things, microbial, plant and animal respiration. In humans, the trigger to inhale isn’t controlled by low blood-oxygen levels; CO2 levels control it. Take away CO2 and life gets hard. So how could this gas be considered a pollutant? To understand that we need to consider what else CO2 does. Most people understand that CO2 is necessary for temperature regulation in the atmosphere (its not the only thing, but its critical). Too little, we lose heat to space and things get cold. Too much and we get Venus. If we double atmospheric CO2 to, say 800-ppm individual animals and plants would hardly notice (no where near 10,000 ppm levels), but the effect on atmospheric temperatures and climate could be extreme. If CO2 levels get high enough to cause the climate to become dangerous to life then it’s following the dictum of Paracelsus: it is behaving as poison. The same way Ramazinni recognized that silica dust was toxic if you inhaled enough of it. So, is my wife in danger from a can of talc? Probably not. Is CO2 toxic? Is it a pollutant or necessary organic compound? It depends. “All things are poison and nothing is without poison, only the dose permits something not to be poisonous.”
Until next time,
Tom Williams
