What an interesting question Alan. We are talking about 'fuming' correct?
Lets' consider this... these 'fumes' are submicron particles... almost single atoms.
Silver 'fumes' at 2212 degrees C, producing 5,607,476,635,514,018 particles per microgram.
Gold 'fumes' at 3080 degrees C, producing 3,045,685,279,187,817 particles per microgram.
(Note: The particle count is an approximated count for a 1/8" x 1/8" square piece of foil - approximately one microgram -- if I did my moles, mass weight, and molecules calculations correctly
)
Checkout the particle count. These are
tiny particles. These are submicron particles... referred to by the EPA as 'fine particles' or Particulate Matter less than 2.5 microns (PM2.5). Submicron particle distribution in 'room air' is influenced exclusively by thermal currents. That is, they float on the air... and flow with the air current... they don't drop like a rock --
ever (unless it's raining). Once 'fumed', they have slightly more mass than a few oxygen molecules. If something gets in their way they will 'stick' to it, e.g., bead, finger, wall, etc.. (Goldfinger?)
Also note the relatively small difference in particle count between both materials -- in the quadrillions (at least
I think that big number is quads). IMHO I don't think it really matters, particle-wise, which material is being fumed. Neither does it to the EPA... a fine particle, is a fine particle, is a fine particle.
Now... before you think I'm an alarmist... note that the allowable submicron level of particles is nominally 35 micrograms per cubic meter of breathable air, per day.
http://epa.gov/pm/standards.html So, theoretically you could fume up about 35 of the little squares referenced above every day. But remember the rest of the world uses up most of that 35 with
other types of combustion processes. Also note, that until 2006 that number was 50 per day... but enough 'normal' air pollution was finally brought under control that the number could be lowered to 35. (Yes... it does sound like shooting an arrow, and then drawing a bullseye around it). Basically... there's not a lot of 'room' left in the air we breath inside a studio, to add more nanoparticles to it.
How about toxicity-wise? Submicron particles, aka nanoparticles, bypass all of our biological respiratory protection filtering mechanisms... which means they go directly to the alveolar region of the lungs, via the mouth and nasal passage; and possibly via the nasal olfactory organ to the cerebellum. Tests with fish show nanoparticles migrated to the cerebellum (the part responsible for sensory perception and motor output). However, no behavioral changes were noted in the fish, which is good!, but these were fish after all... how much behavior change would we see?
Although nano sized particles have been a concern of the EPA since the 1970's, and the EPA reviewed and revised standards to be even more strict in 2006, and several studies have be started in the last few years... the first international conference (CDC/NIOSH) on nanomaterial toxicity did not occur until about 2 weeks ago. That kind of lets us know just how little we know about this topic... toxicity-wise. Basically... we know that if it's a fine particle, then it's not... it's a bad particle... sometimes. Which ones are the bad ones, and how bad each one is, is still pretty much a guess -- so we assume they all are bad. On the flip side, studies are ongoing that use gold nanos as 'medicine delivery systems' to target specific disease causing organisms. So maybe golds' good. Maybe.
So what should we do? Like many things, it's a personal decision. You won't drop dead or develop emphysema tomorrow morning from fuming today (the CDC is pretty quick to catch onto those bad actors
). Particle buildup in the body depends on exposure... frequency and concentration... and the body does have a tendency to elminate some 'bad things'... over time (sometimes years). So, IMHO, MIT's suggestion for their labs is worth seriously considering: "Working safely with nanomaterials involves following standard procedures that would be followed for any particulate material with known or
uncertain toxicity (emphasis added): preventing inhalation, dermal, and ingestion exposure."
http://web.mit.edu/ENVIRONMENT/ehs/t...omaterial.html
How about respirators (aka the particle filter 'mask')? That is what you asked about
. The N100 mask most folks use is designed and expected to reduce exposure to 1/10 what it would be without a mask. WHAT? Only 90% filtering? Yes, the mask material will trap 99.97 % of the nanoparticles
that hit the 'filter' material... but does nothing to stop those particles that make it around the face seal. Thus, the 'paper and elastic bands' air purifying half-face mask reduces exposure... but certainly does not eliminate it. That's why NIOSH considers them to be AFP10 respirators (i.e., 10% bypass - 90% minimum protection).
http://www.osha.gov/SLTC/etools/resp...e/apf/apf.html
The suggested answer... IMO, the only real answer... Adequate Local
Exhaust Ventilation.
Me
p.s. Oh yes... re: the boro shops...
youth is invincible!... I was invincible once too... about century ago -- actually it was a century ago.
p.s.s For those who have read this far... you might now be thinking... hmmmm... when I melt glass, don't I also 'fume' glass molecules... like say boron oxide? The short answer is... Yes. Ditto 'adequate ventilation'.
Gold and silver foils...
