Inez,
I think Thompson Enamels is just ground up glass. But you might email them to ask.
Here's my two cents:
I have never seen anything that specifically states "Do not inhale tiny glass particles" but that's probably b/c it seems like a "duh" statement.
However, I HAVE heard one should not get glass in your eyes.
Our lungs are under attack, so to speak, daily...every time we breathe. Small particles flying around every day are filtered by our nose and nasal passages.
I believe that we should worry as much about the fumes from our torches and glass as the flying particles of glass. Which is to say, that caution is warranted in every aspect of our work.
"Fairy dust" and enamel probably fall into this category (but I've never measured them to be sure)
that I found in lung disease data from Nat'l Lung Assoc.
"
Fine particles, with a diameter of 2.5 microns or less (pm2.5) represent the most serious threat.
Particles this small easily penetrate the alveoli, the very smallest air sacs of the lung, and because this region of the lung has a slow clearance system, the deposits persist to perpetrate damage for long periods of time. A study conducted in Belgium in 2002 showed that the tiniest particles,
termed ultrafine particles – those less than 1 micron in size – may pass through to the blood stream and then to the rest of the body.
Exposure to particle pollution increases the risk of premature deaths and can trigger asthma attacks, wheezing, coughing, and lung irritation in people with sensitive airways. Persons with chronic cardiovascular disease and diabetes are also at high risk