[Jewelry making - Article 00291] - Re: [Orchid] Ultrasonic cleaner and damage to hands

[Bruce Holmgrain]

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>         Hello all, There is a HUGE difference between the frequencies
>     used by ultrasonic cleaners and ultrasound medical equipment. 

    No doubt. My point is that there is little, if any, evidence that
    ultrasonic cleaners used by most jewelers cause any long lasting, or
    even short lasting damage to tissue or bone. 

>         So he just reached in and fished the slices out. He did this
>     many, many times that night with the big ultrasonic tank on the
>     entire time. 

    Was this a typical jewelers ultrasonic? 

>             By the next morning he could not hold a pencil, his
>     fingertips hurt so badly. Basically, the doctor told him that the
>     sound waves had given him the most complete set of stress fractures
>     he'd ever seen. Not to mention the soft tissue damage -- the
>     pinkness and swelling was due to bleeding deep in the tissue. 

    How would we be privy to what "doctor told him"? 

>         Since the sound waves travel especially well in liquids, and
>     you are basically a liquid in a sack made of skin, you can see how
>     there is a potential problem here. 

    Not being a physicist, I would be more inclined to assume that most
    of our tissues behave more as a gel. Absorbing the kinetic energy and
    converting it to heat. 

>             As for the issue of tissue damage, check out the
>     "Guidelines for the Safe Use of Ultrasound, Part II -- Industrial
>     and Commercial" at the Canadian government's informative Consumer &
>     Clinical Radiation Protection site. Specifically:
>     www.hc-sc.gc.ca/hecs-sesc/ccrpb/publication/safety_code24/toc.htm
>     Click on the "contact exposure" headings. They do mention the
>     scarcity of research on this topic. There has been one study with
>     volunteers, who did confirm that putting your fingers in a tank can
>     hurt. (I would suspect that there are ethics problems in pursuing
>     this further with human subjects.) The article says: "Contact
>     exposure can in some cases provide nearly 100% energy transfer to
>     tissue... 

    This is the beginning of a paragraph that addresses  ultrasonic
    humidifiers in particular. 

    The next couple of paragraphs, including the one which you cite
    below refer to devices operating in the "low  MHz frequency range"
    which, to the best of my knowledge is at least an order of magnitude
    above the operating range any ultrasonic cleaner that I have had
    experience with. 

>         For example, high-power ultrasonic waves are used in ultrasonic
>     cleaners and cell disintegrators because of their destructive and
>     violent effects. It is certainly reasonable to assume that
>     relatively intense cavitation activity occurs in the water (or
>     solvent) baths of such devices.... "The literature on devices such
>     as ultrasonic cleaners and tissue homogenizers is confusing: these
>     devices do not appear to be as hazardous as expected, given the
>     effects they were designed to create. Nonetheless, although reports
>     of biological effects are surprisingly rare, exposure to the
>     liquid-bourne ultrasound from these devices clearly can cause
>     tissue injury, and protection measures are necessary." 

    This paragraph is very confusing. It is very late and I wonder why
    it was written. 

    "Nonetheless, documented cases of actual tissue damage are rare. In
    one documented study, exposure to ultrasound in ultrasonic cleaners
    operating at frequencies between 20 and 40 kHz was reported to have
    caused pain in the hands of the volunteers." 

    I took my daughter climbing last night. She complained of hand pain.
    Does that mean anything other than her hands got a workout? Should I
    not allow her to climb anymore? 

    I found section 4 with "Guidelines for Safe Use" amusing. I am sure
    that these make sense with particularly large or powerful cleaners, I
    suspect that this section is not meant to apply to jewelers.


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