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Thread: Clarification about Pyro

  1. #1

    Join Date
    Dec 1999

    Clarification about Pyro

    We have slightly revised the piece on pyo's health hazards on our web sites

    the first paragraph was actually a question Mr. Knoppow was responding to

    I am still waiting for the critics of this piece to bring new light to the topic rather than just be critical.

    On another note in the current issue of CameraArts I have compared PMK and HD with 35mm FP4+ In the July issue of View Camera (out in about 10 days) I compare PMK and HD with Tri-X and FP4+ 4x5 sheet films.

    steve simmons

  2. #2

    Clarification about Pyro

    I am still waiting for the critics of this piece to bring new light to the topic rather than just be critical.

    There are about 10 to 15 answers in the other thread that bring not only new light but show why your "article" is bad, yet you refuse to see it. You are behaving like an Ostrich, you bury your head in the sand and you think since you cannot see it, it does not exist.

    I really am at a loss of words here, given that you and I dont see eye to eye in many things, if you are going to lift an answer from a forum an paste it on your web site, you better look at the answers given by Kirk Keyes on the thread you started, they are far better and explain the hazards better. But as he pointed out, it would be better if you had a toxicologist write you a real article with data and studies.

  3. #3

    Clarification about Pyro


    I've had the "pyro is so dangerous" discussion with numerous people over the years. It is nothing short of ridiculous that many of the same people who tell you that pyro developers are too toxic to handle safely go on to stick their bare hands into other developers. The fact is that all film developers contain compounds that are readily absorbed through skin and are toxic to some degree. I have a PhD in Organic Chemistry and feel qualified to state here that according to all data I have seen, pyrogallol and catechol are not significantly more toxic or dangerous than hydroquinone. One should strive to limit exposure to both.

    If one takes care not to inhale the powder when mixing from scratch and wears nitrile gloves (which you should do with ALL developers), pyrogallol and catechol (my personal favorite in Pyrocat-HD) are no more hazardous than hydroquinone.

    Some data (below) would suggest that hydroquinone is actually more acutely toxic than pyrogallol. In my opinion, the below data (from show that all three of our favorite hydroxybenzenes are basically equally toxic.

    Hydroquinone, CAS Number 123-31-9 Synonyms: 1,4-dihydroxybenzene; 1,4-benzenediol, p-Dihydroxybenzene Oral rat LD50: 320 mg/kg

    Catechol, CAS Number 120-80-9 Synonyms: Pyrocatechol; 1,2-benzenediol; 1,2-dihydroxybenzene Oral rat LD50: 260 mg/kg

    Pyrogallol, CAS Number 87-66-1 Synonyms: Pyrogallic acid; 1,2,3-benzenetriol; 1,2,3-trihydroxybenzene Oral rat LD50: 789 mg/kg

  4. #4

    Clarification about Pyro

    What are nitrile gloves? Are typical "rubber" gloves one can buy at walmart inadaquate?

  5. #5

    Clarification about Pyro

    Jeremy, rubber gloves will work just fine. Here is the theory as explained to me by OSHA. Latex and rubber are less resistant to alkaline environments, in continuous exposure they will start to develop pin holes and allow developer to seep into them, but and here is the big but, this is only for periods of hours. If you put your gloves in the developer for 10 minutes, and replace them with new ones for the next developing session, you will have no trouble.

    As Linas stated, nitrile gloves are better, but for the limited amounts of time we put our hands in the developer, latex and rubber are just fine. Of course, if you plan to do a long developing session and plan to keep your hands in the soup for more than 10 to 15 minutes, it is better if you get nitrile gloves, they are really no more expensive than latex and you can buy them in a box just like latex gloves.

  6. #6

    Join Date
    Jan 2001

    Clarification about Pyro

    Jeremy, I get nitrile gloves at Lowes Home Improvement Center.

  7. #7

    Clarification about Pyro

    Some information from the June 1997 edition of the "NIOSH Pocket Guide to Hazardous Chemicals" published by the U.S. Dept of Health and Human Services:

    Hydroquinone (p.170): NIOSH recommends exposure to no greater than 15 mg/m3 at any time over an 8 hour day. OSHA recommends exposure to no greater than 30 mg/m3 at any time over an 8 hour day. (Note: I understand these values to apply to the powered material.) The IDLH, i.e., the concentration which poses an 'immediate danger to life and health', is140 mg/m3.

    Catechol (p.56): NIOSH recommends 8 hour time weighted average (TWA) not exceed 20 mg/m3. OSHA does not offer a TWA exposure limit and there is no IDLH listed.

    Pyrogallol is not included in the NIOSH Pocket Guide.


  8. #8

    Clarification about Pyro

    The NIOSH Pocket Guide also indicates that skin exposure should be prevented for both hydroquinone and catechol.

  9. #9

    Join Date
    Dec 1997
    Baraboo, Wisconsin

    Clarification about Pyro

    Jorge et al - Why bother? In the first thread on this subject Steve Simmons writes the following: "There have been no studies of the chronic effects of pyro exposure. Pyro is no more hazardous than several other developing agents." Pyro may or may not be more hazardous, I have no idea. However, if someone says in one breath that there have been no studies of its possible hazards, then in the next breath says it's not hazardous, that person is not someone who thinks in a particularly logical manner or whose opinions are likely to change just because there are no facts to support them.
    Brian Ellis
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

  10. #10

    Clarification about Pyro

    CORRECTION!!! I copied the hydroquinone information out of the wrong row in the table.

    Both NIOSH and OSHA recommend exposure to no more than 2 mg/m3 of hydroquinone. The IDLH is 50 mg/m3.

    Sorry, Chris

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