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Dangers of Rock Dust

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Dangers of Rock Dust
By Glen Kuban

Keywords: Silicosis, pulmonary fibrosis, lung disease

Many collectors use a mechanical rock saw to cut, trim, or abrade rocks and fossils in the field or lab. Dangers of this activity include flying rock chips, wounds from the blade itself or broken blades, and rock dust, which is extremely dangerous to inhale. Always read and understand the proper operation of any mechanical tool before using it. Whenever cutting or grinding rock, wear protective eye goggles. Also wear a good respirator, or use a dust collection system, to avoid inhaling rock dust, which accumulates in the lungs and can cause a variety of serious illnesses.

For those not convinced that rock dust is a serious danger, or that they can get away with not wearing a respirator or working under a hood (if working indoors), I encourage you to read the messages below. The original message was posted on 7-14-97 in the Rocks and Fossils Newsgroups, and my reply was sent to that list as well as the Dinosaur List, VrtPaleo, and Fossil Nuts.

The original message I am responding to was posted in Rocks and Fossils, but I am sending my response to other paleo related lists as well, because I feel this is an important safety issue. It affects anyone who even occasionally cuts rocks or fossils, or does fossil preparation work. It will be very worthwhile if it prevents even one person from suffering lung problems or dying prematurely. With that deliberately ominous introduction, let me quote the post that prompted my response:

Pete Richards wrote: {{Last night I spent an hour cutting sandstone sidewalk blocks with a composition blade made of fiberglass and carborundum grit. This is a dry saw and it was a still night and clouds of dust were all around. Some of it hung in the air for minutes. I am not really concerned about a one-shot exposure, but it did make me wonder if this is the size of silica which DOES represent a health hazard. Of course, I do not know for sure that the fine dust was silica, as opposed to calcium carbonate (the cement in the sandstone) or material from the saw blade... }}

It's funny, or really not so funny, that you should write now. I'm suffering a chronic lung irritation, and seeing doctors now, because of the results of a similar incident. In short, yes, one or a few exposures to significant amounts of freshly-cut rock dust can cause serious problems. Silicosis is only one of many lung problems that can be caused by rock dust, many of which (like fibrosis) can occur no matter what the composition of the rock. Wearing a good respirator or hood with dust collector if working indoors is a must. If you don't have the proper safety equipment, don't cut the rock!

Unfortunately, I found out the hard way, I hope everyone learns from my mistakes. About a year ago our fossil club went to Ontario to collect trilobites, and we took along a diamond rock saw. I only sawed out a few trilobites for fellow members (without wearing a mask; I forgot to bring one) and I tried to not inhale the dust. However, large clouds of it were kicked up each time, and it was impossible to avoid inhaling quite a bit of it. My the next morning I had significant lung irritation, and have had it ever since -- some days worse than others. I have frequent coughing and uncomfortable sensation in my upper chest. After this went on a few weeks, I went to a doctor, not knowing if I had contracted a bacteria, fungus, or other microbe at the quarry, or just had accumulated too much dust in my lungs. An x-ray was clear, but that is not unusual in such cases (it sometimes takes years for fibrosis, TB, cancer, and other diseases to develop). Apparently the rock dust itself is the cause the current lung irritation, and it may never get better. In fact, it may worsen into other conditions, as explained below.

Many people assume years of exposure to rock dust is needed to cause serious problems, and this is generally true when dealing with wind-blown, low concentration dust, which usually has already been weathered to some degree. But not so with freshly cut rock. After I started having my problems, I began talking to doctors and doing lots of reading. I also talked to an uncle who used to work in a quarry, and is now dying of pulmonary fibrosis at the age of 55. I'm now going to his doctor.

It turns out that not only do rock particles of any composition tend to stay and accumulate in the lungs, but FRESHLY CUT rock is the worst, and extremely pernicious. Even one or a few incidents of significant inhalation of such dust can cause lung irritation and a start process of increasingly serious lung damage. The microscopic particles are like millions of razor-edged shards that damage lung tissue directly, as well as create conditions promoting the development of TB, microplasms, fibrosis, and cancer. Experiments with rats and other animals have shown that inhalation of fresh cut rock dust is far more damaging than worn rock dust of any composition, and leads to far greater rates of several diseases, including pulmonary fibrosis and lung cancer. (But even accumulations of worn rock dust in the lungs greatly increased chances of lung diseases).

I've also made many fossil molds and casts over the years, and although I often wore a mask while working with plaster, but sometimes did not. I may well have accumulated plaster in my lungs as well, which may have contributed to or aggravated my lung condition. Plaster hardens when in contact with moisture, wherever it occurs, including one's lungs. But I did not have the constant lung irritation until after the Ontario trip using the rock saw (on hard shales and siltstones), and have had it ever since.

I have another appointment with a pulmonary doctor on Thursday, but from what I have learned such damage is generally irreversible, the best I may hope for is to have my condition not get worse. I may have to live with lung
irritation and chronic caugh for the rest of my life, plus increased chances for the serious conditions I listed above.

So PLEASE, whenever you are cutting or grinding rock of any kind, ALWAYS wear a respirator (not just a cheap dust mask). If working indoors, use a dust collecting hood, or don't do it. Your health is not worth any rock or fossil.

There are serious inhalation dangers in the lab also, including solvents, urethanes, glues, and other chemicals used on prep work. These too can have accumulative effects, and lead to a variety of heath problems. Work with such chemicals only with very good ventilation, or under a hood, or don't do it. Again, a rock or fossil is not worth your health.

If I scared anyone, I can't feel too bad, because I wish someone had scared me before I did what I did, and may have to pay the price the rest of my life.

Pete, in your case, I hope you do not have any problems, and can only urge you not to do it again, at least not without wearing a respirator. The dust you created by cutting sandstone probably included a mixture of siliceous sand particles, calcium carbonate particles, (from the cement between the sand grains), and fibers from the fibrous saw blade. All could be dangerous to inhale.

Thank you.

Glen Kuban

Glen Kuban's message touched a chord with me concerning the dangers of rock dust or other airborn particulates. Since starting this hobby a year ago, I've been thinking about getting a mask, not one of the disposable gause varieties, but a professional quality model with replacable filter canisters. But two things have held me up; not knowing what to protect against, and not wanting to look like a wimp in the shop on an ill-founded hunch that the stuff is bad to breathe.

I would assume the list of damaging particulates is quite long. One candidate I think might be added is the cutting oil in the clouds of smoke coming from slab and trim saws. Another is the fresh-cut rock particles that are carried by the aerosol mist from the grinding and sanding wheels. Does anyone have any hard data about these sources? Opinions are plentiful, but it is supported data that we need.

In particular, I'm interested in the size of the particulates so that I can better choose a mask and filter.

Los Angeles

I've heard that there is a chemical component to this problem, that it isn't just the shapes of the rock particles that are dangerous. As I recall, there is a reaction that occurs which converts silicon dioxide to silicic acid as
freshly-cut rock dust is hydrated in the lungs; which greatly increases the corrosive effect experienced. Apparently, this hydration will happen naturally as the particles are exposed to the moisture in the air, rendering the dust less harmful some hours after it is produced. This was supposed to account for the increase in virulence of the fresh particles as experimentally verified above. Does anybody have any confirmations or refutations of this theory?

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
(Ed. Note: Nathan Schachtman wrote a recent post to Rocks and Fossils mail list addressing this exact question concerning silicic acid, the presence of a high zeta charge of the surface of newly cut rock and the biological activity. I have just written to him asking permission to reprint it here, which I will do as soon as he replies. It is directly related to the questions which Andrew has raised. -- hale)

Hold on all you wise experienced ones...there are some of us new-to-lapidary out here who may be missing some basic points...I was under the impression (mistakedly????) that because I saw with oil and shape and polish with water on my arbors that I have eliminated the dangers of rock dust, making a respirator unnecessary.

Please back up a couple of steps and give us newbies a little more info.

Thank you so much!!!!



(In an earlier post on Rocks-and-Fossils mail list, dated 7/16/97, someone had suggested that there were two reasons why freshly cut rock dust was far more dangerous then wind blown dust. First, it has sharper edges which can really damage your lungs; the comparison between them was compared to the differences between shards of broken glass and tumbled pebbles. Next, the concentration of rock saw dust is probably much greater than the concentration of dust in wind)

In reply to this, on Thu, 17 Jul 1997 "Nathan A. Schachtman" {nschacht@voicenet.com} writes:

The reason is much more likely to be that freshly fractured silica carries a surface charge (high zeta potential) that makes the particles much more membranolytic or cytotoxic. It really has nothing to do with the shape of the particle.

If you take those same particles and allow them to age, their biological activity goes down as the surfaces are hydrated. The toxicity of the particles can be restored by washing the particles in acid to dissolve away the layer of hydration (Beilby layer) and expose the fresh silica surface.

Someone else mentioned that silicic acid (silanols) was the bad acting chemical functionality. That's not at all clear. At neutral pHs, silicic acid is not going to much protonating. It is hydrophilic, and can be absorbed in bodily fluids and excreted. Indeed, silicic acid is how we absorb silicon as an essential neutrient. It is a normal constituent of connective tissues and bones, and most human organ tissues has a baseline of silicon content.

Amorphous silica is relatively harmless, and it has surface silanols as well.

The sort of fatal silicosis that results from short, extremely intense exposures is well known in the sandblasting industry. Sandblasting with silica has been prohibited in the UK for a long time now. I suspect that we will see it outlawed within a year or so in the US.

Can fatal silicosis result from a single intense exposure. I would want to see the chest x-rays myself, but there are case reports of people inhaling extremely fine ground silica, such as you will find in Ajax type products,
with lethal effects.

Nathan A. Schachtman

{Reprinted with permission of the author}

Here's an item for a slow day. You've devoted lots of space lately to the dangers of breathing rock dust. In the current Lapidary Journal (August '97), June Culp Zeitner's "Shop Helps" column points out that the longest word in the third edition of Webster's Unabridged Dictionary describes the condition caused by breathing fine silica or quartz dust. I'd think people would avoid doing so simply because, at some future time, someone might ask them the name of their illness and they'd have to say:

While it's a fairly minor danger, gem hobbyists who go on to learn to cast their own lost-wax settings should avoid breathing casting investment (plaster) both when mixing it and when boiling it out of hot casting flasks in cold water. Investment is made of cristobalite, which is dangerous when large quantities are breathed. It's mostly a danger in big production shops and the occasional caster shouldn't be paranoid about it, but since there are people who have lung ailments who might be affected by light exposure. A good
mask can't hurt.

Rick Martin

Howdy Folks,
I would like to know if there exists the same huge difference in lung problems comparing smokers versus non-smokers with respect to 'rock dust' as there is with asbestos. My Dad lost about 1/3 of a lung and suffered other problems but in reading about the issue it appears that, he having been a smoker, his 'cilia' were coated with tar and particles cannot be removed from the lungs. If this is true it would be even MORE prudent for those of you who smoke to wear a mask.

1 Lucky Texan

[Here's a message from sci.bio.paleontology that might be good to include in the "Dangers of Rock Dust" file. I certainly never thought of this when I started grinding on dinosaur ones ...aw]

Someone had written:

{{Saw something about fossil detection using a "radiation monitor" on a hand truck (CNN). Just checked fossil shark tooth and found about 3X background radiation. Are all fossils "hot"?}}

and someone else answered:

{{Enough so that people used to go dinosaur hunting with a Geiger counter! And enough that I have a ring radiation badge as well as one pinned to my shirt when I'm working on my Wasatchian mammal specimens. It's unlikely that you have some that is dangerously "hot", but you might want to check just
to make sure.}}

Indeed. Some Morrison Formation bone material is down-right blazing. It is also a VERY good idea to wear a breathing filter when dry-sawing, dry-grinding, and especially when air-abrasive prep'ing fossil bone and it's surrounding matrix. If the fossils and matrix can take it without crumbling into dust, WET-saw and wet-grind matrix blocks.

Keep in mind that it really isn't the uranophosphate complexes that are dangerous; it's their fission daughter products (radium, radon, and some lead isotopes) that are dangerous to your health. Radio-lead easily incorporates into living bone tissue, and radon adsorbs onto almost any surface (such as alveoli in your lungs) where it emmits alpha rays. Radium is a strong gamma emitter.

An old issue of a radiologist's trade journal noted a whale vertebra from the Calvert Cliffs that was emmitting at the lower allowable background limits as defined by the EPA.

On the other hand, some fossil bones are less radioactive. Hell Creek Formation material from Montana is {relatively} benign in this regard.

BTW: this characteristic of fossil bone apatite to have an affinity for uranium ions has ramifications regarding the preservation potential of ancient DNA. Think about the cumulative effects of having bone collagen and bone DNA zapped with ionizing radation for 225-65 million years. Is that dinosaur DNA going to be preserved in long enough segments to be recognizable?

(See also David Gillette's book _Seismosaurus: The Earth Shaker_...even though his team extracted bio-molecules from the pelvic region (Jour. Vert. Paleo article of a few years ago), the Seismosaurus specimen was also very radioactive. No DNA was found).

Phillip Bigelow {bh162@scn.org}
Sent by:
Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
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