Letter 0020

Zinc "whiskers"

As an Industrial Hygienist I have the opportunity to assess numerous health risks. Never have I seen any research about zinc whiskers or zinc needles. A minor search of professional IH groups has not identified any health based documentation. Of course zinc oxide, zinc stearate, and other zinc forms have been known and assessed for quite some time now. One article I recently read, attempted to draw a comparison between asbestos and zinc whisker exposure. While I can understand the electronic risks, do you know of any health based documentation? I am aware of the court case you directed others towards. Thanks Ed Kramer - St. Louis, MO ++ Would you please give us that asbestos-zinc whisker article's reference please? Sounds a little far out to me. Tom Pullizzi Platronica.com Falls Township, PA   ++ I have not read the asbestos-zinc whisker article, but I do know that a relationship could be drawn between them. In at least one state (Michigan or Minnesota, I forget, but I'm sure there's others), the legal definition of 'asbestos' is any inorganic substance that has a 100:1 length-to-width ratio or greater. By this definition, zinc whiskers are classified as asbestos and a manufacturer could be sued on the grounds that the company is exposing their workers to asbestos. This legal definition is different than the true geologic definition of asbestos, which has this description in addition to others but is limited to a small range of silicate minerals. As a side note, 95% of all asbestos does NOT cause lung cancer. They do, however, causes asbestosis, which is the scarring of lung tissue as these crystals get stuck in the lung, which I'm sure that zinc whiskers could cause. I cannot remember which state this story came from, but some mining company that mined nothing similar to asbestos was sued for contaminating the river exiting the mining grounds with asbestos. After some scientific research was done, it was found that the mining company was keeping the river TOO clean. Some diatoms (aquatic microorganisms) that grow only in the cleanest of waters produced silica shells with a length-to-width ratio of 100:1 or greater, which met the legal definition. Unfortunately, I never heard about the conclusion of the lawsuit... Chase Watkins - Purcell, OK Asbestosis is a real disease that had a number of industrial workers as its victims, who have our deepest sympathy. And it's probably true that certain particle sizes and shapes are troublesome regardless what they're made of, just as glass shards do terrible bodily damage despite their lack of hazardous chemistry. But asbestos became a multi-billion dollar boondoggle on all fronts. The American golden goose is dead from a dozen butchers, none of which was asbestos itself, but one of which was our voracious legal industry. It will be amusing to watch that legal industry try to sustain itself on recovered damages from Chinese zinc plating shops :-)   Ted Mooney, P.E. finishing.com Inc. - Brick, NJ

I am a co-author of the article referenced elsewhere on this site. It is not for any individual to make a claim as to hazards of any material. I realize that the comparison to asbestos has raised some eyebrows. First, I would like to say that the article being distributed is an excerpt of a much larger article that was prepared to outline a very specific operational function in an attempt to recover a zinc needle (zinc whisker) contaminated specification environment.
The citing of asbestos properties was made for the purpose of highlighting the fact that it is the shape of the debris, NOT what the chemical makeup, that create inhalation issues.
OSHA's consideration of inhaled zinc. One must do considerable research to discover the documents referenced in the writing of that article. In fact, in a cursory search, the OSHA site has no specific listing for Zinc, but rather Zinc Oxide. For any business concerned with safe and legal operations in America, the issue requires referencing the OSHA classification of whatever the worker may be exposed to in the workplace. There is clear documentation available from OSHA that states inhalation of airborne Zinc particles (Specifically NOT Zinc Fumes nor Zinc Oxide) is considered to be much more than a respiratory irritant.

The following is taken directly from OSHA documentation referencing the hazards of inhaling zinc particles:

NAME: Zinc
IMIS: Z100
CAS: 7440-66-6
DESCRIPTION: Solid.

HEALTH EFFECTS: Irritation-Eye, Nose, Throat, Skin---Marked Respiratory Effects---Acute lung damage/edema Chronic(Cumulative) Toxicity-Suspect Carcinogen or mutagen

I trust this will clear up any questions as to whether statements made in that document are not in line with the OSHA listing.

I am not a metallurgist, nor a doctor. The document in question elsewhere on this site drew attention to the POTENTIAL hazards of inhaling zinc particles in order for our client to determine how his crew should proceed in the operation. Throwing caution to the wind is not prudent in dealing with large scale contaminations of any kind.

VRM

Valan Martini
- Atlanta, Georgia, USA

I can't agree with your second sentence at all, Valan! It is dangerous nonsense. True, it may not be safe to rely on an individual's claims -- but claims by individuals are the starting point of almost all progress. Rachel Carson's Silent Spring was the seed that started the whole environmental awareness movement -- bureaucrats had absolutely nothing to do with it; please don't rewrite history to try to credit the environmental awareness movement to bureaucrats.

Facts are facts irrespective of pronouncements. Asbestos did not actually become dangerous the day OSHA or a government authority said, and remain safe until that day. Are certain compunds carcinogenic within the USA but not elsewhere, and vice versa, because different governments make different pronouncements? That's just crazy.

I lived through this issue while OSHA was wishy-washing about whether hexavalent chrome was carcinogenic. Trying to get chrome plating fumes treated the way they should be was difficult because some architects felt it "wasn't for an individual to say" that it was hazardous. If someone feels that something is hazardous, they should most certainly say so. And if they feel that, in a world of ever-present risks and limited resources, the sky is not falling due to zinc whiskers, they should say that too.

If your referenced report is available, please provide a link. I don't see any reference to your article on this site beyond "One article I recently read" and "I have not read that article", but I might have missed it. I have never seen your article nor heard of it, let alone was I criticizing it. Thanks!

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

P.S.: This "a thing is asbestos if it's longer than it's wide" reminds me of the punch line of an old favorite song, Melanie's Psychotherapy :-)

In silver and copper, the phenomenon has been known for about 425 years now, and for about sixty years in tin, zinc, and cadmium. Check out Scientific American [link is to product info at Amazon], 203:1, 1960, p. 64 -- although the focus is on whisker growth from vapor, basal growth is mentioned. Metal whiskers are discussed in the "Handbook" edition of R. Holm's, "Electric Contacts".

Small amounts of lead, antimony, and a few other elements impede basal growth whisker formation -- probably by blocking material transport along grain boundaries.

Interest in metal whiskers is episodic, waxing when another costly failure is attributed to them.

Norman Helmold
GSFC, NASA - Greenbelt, MD, USA

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This letter is within a monitored forum, very much "alive" here in 2008. If you spot any broken links or obsolete info, please advise!