View Full Version : Clarification about Pyro

steve simmons
17-Jun-2004, 07:52
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

Jorge Gasteazoro
17-Jun-2004, 08:53
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.

Linas Kudzma
17-Jun-2004, 09:00

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 jtbaker.com) 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

17-Jun-2004, 09:05
What are nitrile gloves? Are typical "rubber" gloves one can buy at walmart inadaquate?

Jorge Gasteazoro
17-Jun-2004, 09:15
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.

Ken Burns
17-Jun-2004, 10:25
Jeremy, I get nitrile gloves at Lowes Home Improvement Center.

Chris Gittins
17-Jun-2004, 10:33
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.


Chris Gittins
17-Jun-2004, 10:51
The NIOSH Pocket Guide also indicates that skin exposure should be prevented for both hydroquinone and catechol.

Brian Ellis
17-Jun-2004, 10:55
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.

Chris Gittins
17-Jun-2004, 11:06
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

John Boeckeler
17-Jun-2004, 11:24
Almost makes me want to go digital.

Kirk Keyes
17-Jun-2004, 12:17
Brian - if you look in the earlier thread, you will find mention of studies that have been done on rabbits and mice (see http://ntp-server.niehs.nih.gov/htdocs/Chem_Background/ExecSumm/Pyrogallol.html This document is written by the National Institute of Environmental Health Sciences - I again suggest that everyone take a look at this document and read through it at least once.)

A quarter of the way through the document you will find this sentence, "Lifetime dermal exposure of mice and rabbits to low doses of pyrogallol did not induce toxic effects." So while it apears that no one has done any tests to determine the chronic effects on humans, these tests have been done on mice and rabbits.

Pyro use in developers is exactly this kind of exposure - low dermal dosages. And as Jorge points out above, our photographic exposures are for rather short periods of time. If one adds in the protection that will be gained by the use of gloves, then the risk of exposure to the pyro in the first place is greatly reduced. Certainly much lower than the exposure you get by placing you hands into a tray of Dektol.

Speaking of Dektol, has any one here bothered to read the MDSD that Kodak has for it? See http://www.kodak.com/US/en/corp/environment/kes/healthSafety/pdfs/consumer/B_W.pdf. Kodak is talking about it when diluted as recommended, and it contains the sentence, "In case of contact, immediately flush eyes and skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes." This doesn't sound like something we would want to get anywhere near! But how many of us feel that Dektol is nothing to worry about?

Jeremy - one reason that I find nitrile gloves better is that they appear to be tougher than latex, and there is less risk of the tearing during use. Maybe I just have large hands, but I find that even with fresh latex gloves, quite a few seem to break immedately while putting them on. I rerely ever have a nitrile glove break like this. So I kind of feel that nitrile are better. And they are usually a cool blue or purple color, not that boring beige color that latex comes in! and don't be cheap - do not reuse your gloves. Replace them when you remove them.

Steve Simmons- how about the idea to find a toxicologist or a doctor that is knowledgable in industrial medicine? That would go a long way and most certainly be a very definitive article for the photographic field. Just make certain that references and sources are given, as you see the kind of response that appearantly unsubstantiated claims are given (and rightly so).

17-Jun-2004, 12:34
"recommend exposure to no more than 2 mg/m3 of hydroquinone"

Could I get this in english? 2 mg per cubic metre? A cubic metre of what? Me? Air? Developer?

Chris Gittins
17-Jun-2004, 13:10
>Could I get this in english?

NIOSH and OSHA recommend that people not be exposed to more than 2 mg hydroquinone per cubic meter of air at any time.

That concentration refers to hydroquinone particulates in air, such as you might encounter when you're making up a stock solution. Take home message: wear protection to prevent inhallation of particulates, such as a dust mask, and work in a well-ventilated area when you're mixing up your D76, etc. stock.

The NIOSH guide I have does not offer any quantitative exposure guidelines with respect to hydroquinone dissolved in water, which will be the primary type of exposure once the developer is mixed. NIOSH's only recommendation with respect to dermal exposure is to prevent it.

mark blackman
17-Jun-2004, 15:36
Steve, I for one am grateful that you've bothered to cover this subject, and look forward to reading Richard's comments, which I'll take on board and deal with as an adult.

I sometimes wonder about the negative crap posting on here, is it jealousy I wonder, and why does it all seem to emanate from the USA? View Camera may not be the best photography magazine in the world but it certainly is the only one I know of that covers the LF scene.

All you need to do to make me a really happy bunny is conifer the same rights you give to your American subscribers to those of us elsewhere.

Brian Ellis
17-Jun-2004, 20:07
Kirk - I apparently didn't make my point clear. As I said, I have no idea whether pyro is toxic or not (and don't care, I don't use it though I have in the past). I also have no idea (and don't care) whether any studies have been done on humans, mice, rabbits, space aliens, or anyone or anything else. I just find it extremely odd that someone would say in one sentence that no studies have been done concerning its hazardous nature and in the next sentence say it isn't hazardous. I just don't see how one makes the leap from the first sentence to the second. That was all I was pointing out. As to whether it is really hazardous or not, and as to what studies, if any, have been done, I'll leave the arguments about that to the people who use it and care but I'm not one of those people.