Photographic Processing Hazards
Michael McCann, Ph.D., C.I.H
Adaptations specific to UCSD's environment and policies have been inserted.
Black and White Photographic Processing
variety of chemicals are used in black and white photographic processing. Film
developing is usually done in closed canisters. Print processing uses tray
processing, with successive developing baths, stop baths, fixing baths, and
rinse steps. Other treatments include use of hardeners, intensifiers,
reducers, toners, and hypo eliminators. Photochemicals can be purchased both
as ready-to-use brand name products, or they can be purchased as individual
chemicals which you can mix yourself.
Photochemicals can be bought in liquid form, which only need diluting, or
powder form, which need dissolving and diluting.
Developer solutions and powders are often highly alkaline, and glacial
acetic acid, used in making the stop bath, is also corrosive by skin
contact, inhalation and ingestion.
Developer powders are highly toxic by inhalation, and moderately toxic by
skin contact, due to the alkali and developers themselves (see Developing
Baths below). The developers may cause methemoglobinemia, an acute anemia
resulting from converting the iron of hemoglobin into a form that cannot
transport oxygen. Fatalities and severe poisonings have resulted from
ingestion of concentrated developer solutions.
liquid chemistry whenever possible, rather than mixing developing powders.
Pregnant women, in particular, should not be exposed to powdered developer.
mixing powdered developers, use a glove box (a cardboard box with glass or
plexiglas top, and two holes in the sides for hands and arms), local exhaust
ventilation, or wear a NIOSH-approved toxic dust respirator. In any case,
there should be dilution ventilation (e.g. window exhaust fan) if no local
exhaust ventilation is provided.
gloves, goggles and protective apron when mixing concentrated photochemicals.
Always add any acid to water, never the reverse.
eyewash fountain and emergency shower facilities should be available where
the photochemicals are mixed due to the corrosive alkali in developers, and
because of the glacial acetic acid. In case of skin contact, rinse with lots
of water. In case of eye contact, rinse for at least 15-20 minutes and call
concentrated acids and other corrosive chemicals on low shelves so as to
reduce the chance of face or eye damage in case of breakage and splashing.
not store photographic solutions in glass containers.
all solutions carefully so as not to ingest solutions accidently. Make sure
that children do not have access to the developing baths and other
commonly used developers are hydroquinone, monomethyl para-aminophenol
sulfate, and phenidone. Several other developers are used for special
purposes. Other common components of developing baths include an accelerator,
often sodium carbonate or borax, sodium sulfite as a preservative, and
potassium bromide as a restrainer or antifogging agent.
Developers are skin and eye irritants, and in many cases strong sensitizers.
Monomethyl-p-aminophenol sulfate creates many skin problems, and allergies
to it are frequent (although this is thought to be due to the presence of
para-phenylene diamine as a contaminant). Hydroquinone can cause
depigmentation and eye injury after five or more years of repeated exposure,
and is a mutagen. Some developers also can be absorbed through the skin to
cause severe poisoning (e.g., catechol, pyrogallic acid). Phenidone is only
sightly toxic by skin contact.
developers are moderately to highly toxic by ingestion, with ingestion of
less than one tablespoon of compounds such as monomethyl-p-aminophenol
sulfate, hydroquinone, or pyrocatechol being possibly fatal for adults. This
might pose a particular hazard for home photographers with small children.
Symptoms include ringing in the ears (tinnitus), nausea, dizziness, muscular
twitching, increased respiration, headache, cyanosis (turning blue from lack
of oxygen) due to methemoglobinemia, delirium, and coma. With some
developers, convulsions also can occur.
diamine and some of its derivatives are highly toxic by skin contact,
inhalation, and ingestion. They cause very severe skin allergies and can be
absorbed through the skin.
Sodium hydroxide, sodium carbonate, and other alkalis used as accelerators
are highly corrosive by skin contact or ingestion. This is a particular
problem with the pure alkali or with concentrated stock solutions.
Potassium bromide is moderately toxic by inhalation or ingestion and
slightly toxic by skin contact. Symptoms of systemic poisoning include
somnolence, depression, lack of coordination, mental confusion,
hallucinations, and skin rashes. It can cause bromide poisoning in fetuses
in cases of high exposure of the pregnant woman.
Sodium sulfite is moderately toxic by ingestion or inhalation, causing
gastric upset, colic, diarrhea, circulatory problems, and central nervous
system depression. It is not appreciably toxic by skin contact. If heated or
allowed to stand for a long time in water or acid, it decomposes to produce
sulfur dioxide, which is highly irritating by inhalation.
the section on Mixing Photochemicals for mixing precautions.
not put your bare hands in developer baths. Use tongs instead. If developer
solution splashes on your skin or eyes immediately rinse with lots of water.
For eye splashes, continue rinsing for 15-20 minutes and call a physician.
Eyewash fountains are important for photography darkrooms.
not use para-phenylene diamine or its derivatives if at all possible.
Stop Baths and
baths are usually weak solutions of acetic acid. Acetic acid is commonly
available as pure glacial acetic acid or 28% acetic acid. Some stop baths
contain potassium chrome alum as a hardener. Fixing baths contain sodium
thiosulfate ("hypo") as the fixing agent, and sodium sulfite and sodium
bisulfite as a preservative. Fixing baths also may also contain alum
(potassium aluminum sulfate) as a hardener and boric acid as a buffer.
Acetic acid, in concentrated solutions, is highly toxic by inhalation, skin
contact, and ingestion. It can cause dermatitis and ulcers, and can strongly
irritate the mucous membranes. The final stop bath is only slightly
hazardous by skin contact. Continual inhalation of acetic acid vapors, even
from the stop bath, may cause chronic bronchitis.
Potassium chrome alum or chrome alum (potassium chromium sulfate) is
moderately toxic by skin contact and inhalation, causing dermatitis and
powder form, sodium thiosulfate is not significantly toxic by skin contact.
By ingestion it has a purging effect on the bowels. Upon heating or long
standing in solution, it can decompose to form highly toxic sulfur dioxide,
which can cause chronic lung problems. Many asthmatics are particularly
sensitive to sulfur dioxide.
Sodium bisulfite decomposes to form sulfur dioxide if the fixing bath
contains boric acid, or if acetic acid is transferred to the fixing bath on
the surface of the print.
(potassium aluminum sulfate) is only slightly toxic. It may cause skin
allergies or irritation.
acid is moderately toxic by ingestion or inhalation and slightly toxic by
skin contact (unless the skin is abraded or burned, in which case it can be
darkrooms require good ventilation to control the level of acetic acid
vapors and sulfur dioxide gas produced in photography. Kodak recommends at
least 10 air changes per hour, or 170 cfm for darkrooms and automatic
processors. I recommend using the larger of the two ventilation rates. The
exhaust duct opening should preferably be located behind and just above the
stop bath and fixer trays. The exhaust should not be recirculated. For group
darkrooms, the amount of dilution ventilation should be 170 cfm times the
number of fixer trays. Make sure that an adequate source of replacement air
is provided. This can be achieved without light leakage by use of light
traps. Ducting used with local exhaust systems should prevent light leakage
from the exhaust outlet.
gloves and goggles.
all baths when not in use to prevent evaporation or release of toxic vapors
after-treatment of negatives (and occasionally prints) is either
intensification or reduction. Common intensifiers include hydrochloric acid
and potassium dichromate, or potassium chlorochromate. Mercuric chloride
followed by ammonia or sodium sulfite, Monckhoven's intensifier consisting of
a mercuric salt bleach followed by a silver nitrate/potassium cyanide
solution, mercuric iodide/sodium sulfite, and uranium nitrate are older, now
discarded, intensifiers. Reduction of negatives is usually done with Farmer's
reducer, consisting of potassium ferricyanide and hypo. Reduction has also be
done historically with iodine/potassium cyanide, ammonium persulfate, and
potassium permanganate/sulfuric acid.
Potassium dichromate and potassium chlorochromate are probable human
carcinogens, and can cause skin allergies and ulceration. Potassium
chlorochromate can release highly toxic chlorine gas if heated or if acid is
Concentrated hydrochloric acid is corrosive; the diluted acid is an skin and
Mercury compounds are moderately toxic by skin contact and may be absorbed
through the skin. They are also highly toxic by inhalation and extremely
toxic by ingestion. Uranium intensifiers are radioactive, and are especially
hazardous to the kidneys.
Sodium or potassium cyanide is extremely toxic by inhalation and ingestion,
and moderately toxic by skin contact. Adding acid to cyanide forms extremely
toxic hydrogen cyanide gas which can be rapidly fatal.
Potassium ferricyanide, although only slightly toxic by itself, will release
hydrogen cyanide gas if heated, if hot acid is added, or if exposed to
strong ultraviolet light (e.g., carbon arcs). Cases of cyanide poisoning
have occurred through treating Farmer's reducer with acid.
Potassium permanganate and ammonium persulfate are strong oxidizers and may
cause fires or explosions in contact with solvents and other organic
Chromium intensifiers are probably the least toxic intensifiers, even though
they are probable human carcinogens. Gloves and goggles should be worn when
preparing and using these intensifiers. Mix the powders in a glove box or
wear a NIOSH-approved toxic dust respirator. Do not expose potassium
chlorochromate to acid or heat.
not use mercury, cyanide or uranium intensifiers, or cyanide reducers
because of their high or extreme toxicity.
safest reducer to use is Farmer's reducer. Do not expose Farmer's reducer to
acid, ultraviolet light, or heat.
print usually involves replacement of silver by another metal, for example,
gold, selenium, uranium, platinum, or iron. In some cases, the toning involves
replacement of silver metal by brown silver sulfide, for example, in the
various types of sulfide toners. A variety of other chemicals are also used in
the toning solutions.
Sulfides release highly toxic hydrogen sulfide gas during toning, or when
treated with acid.
Selenium is a skin and eye irritant and can cause kidney damage. Treatment
of selenium salts with acid may release highly toxic hydrogen selenide gas.
Selenium toners also give off large amounts of sulfur dioxide gas.
and platinum salts are strong sensitizers and can produce allergic skin
reactions and asthma, particularly in fair-haired people.
Thiourea is a probable human carcinogen since it causes cancer in animals.
out normal precautions for handling toxic chemicals as described in previous
sections. In particular, wear gloves and goggles. Mix powders in a glove box
or wear at oxic dust respirator. See also the section on mixing
Toning solutions must be used with local exhaust ventilation (e.g. slot
exhaust hood, or working on a table immediately in front of a window with an
exhaust fan at work level).
precautions to make sure that sulfide or selenium toners are not
contaminated with acids. For example, with two bath sulfide toners, make
sure you rinse the print well after bleaching in acid solution before
dipping it in the sulfide developer.
thiourea whenever possible because of its probable cancer status.
other chemicals are also used in black and white processing, including
formaldehyde as a prehardener, a variety of oxidizing agents as hypo
eliminators (e.g., hydrogen peroxide and ammonia, potassium permanganate,
bleaches, and potassium persulfate), sodium sulfide to test for residual
silver, silver nitrate to test for residual hypo, solvents such as methyl
chloroform and freons for film and print cleaning, and concentrated acids to
clean trays. Electrical outlets and equipment can present electrical hazards
in darkrooms due to the risk of splashing water.
Concentrated sulfuric acid, mixed with potassium permanganate or potassium
dichromate, produces highly corrosive permanganic and chromic acids.
Hypochlorite bleaches can release highly toxic chlorine gas when acid is
added, or if heated.
Potassium persulfate and other oxidizing agents used as hypo eliminators may
cause fires when in contact with easily oxidizable materials, such as many
solvents and other combustible materials. Most are also skin and eye
previous sections for precautions in handling photographic chemicals.
Cleaning acids should be handled with great care. Wear gloves, goggles and
acid-proof, protective apron. Always add acid to the water when diluting.
not add acid to, or heat, hypochlorite bleaches.
potassium persulfate and other strong oxidizing agents separate from
flammable and easily oxidizable substances. 5. Install ground fault
interrupters (GFCIs) whenever electrical outlets or electrical equipment
(e.g. enlargers) are within six feet of the risk of water splashes.
processing is much more complicated than black and white processing, and there
is a wide variation in processes used by different companies. Color processing
can be either done in trays or in automatic processors.
first developer of color transparency processing usually contains monomethyl-p-aminophenol
sulfate, hydroquinone, and other normal black and white developer components.
Color developers contain a wide variety of chemicals including color coupling
agents, penetrating solvents (such as benzyl alcohol, ethylene glycol, and
ethoxydiglycol), amines, and others.
the developing section of black and white processing for the hazards of
standard black and white developers.
general, color developers are more hazardous than black and white
developers. Para-phenylene diamine, and its dimethyl and diethyl
derivatives, are known to be highly toxic by skin contact and absorption,
inhalation, and ingestion. They can cause very severe skin irritation,
allergies and poisoning. Color developers have also been linked to lichen
planus, an inflammatory skin disease characterized by reddish pimples which
can spread to form rough scaly patches. Recent color developing agents such
as 4-amino-N-ethyl-N-[P-methane- sulfonamidoethyl]-m-toluidine sesquisulfate
monohydrate and 4-amino-3-methyl-N-ethyl-N-[,3-hydroxyethyl]-aniline sulfate
are supposedly less hazardous, but still can cause skin irritation and
amines, including ethylene diamine, tertiary-butylamine borane, the various
ethanolamines, etc. are strong sensitizers, as well as skin and respiratory
Although many of the solvents are not very volatile at room temperature, the
elevated temperatures used in color processing can increase the amount of
solvent vapors in the air. The solvents are usually skin and eye irritants.
gloves and goggles when handling color developers. Wash gloves with an
acid-type hand cleaner (e.g. pHisoderm (R)), and then water before removing
them. According to Kodak, barrier creams are not effective in preventing
sensitization due to color developers.
powders in a glove box, or wear a NIOSH-approved toxic dust respirator.
processing needs more ventilation than black and white processing due to the
use of solvents and other toxic components at elevated temperatures.
Preferably, for tray processing, use a 3-foot slot hood exhausting 1050
cubic feet/minute (cfm). Some automatic processors can be purchased with an
exhaust, which would need to be ducted to the outside.
Fixing and Other Steps
the chemicals used in other steps of color processing are essentially the same
as those used for black and white processing. Examples include the stop bath
and fixing bath. Bleaching uses a number of chemicals, including potassium
ferricyanide, potassium bromide, ammonium thiocyanate, and acids. Chemicals
found in prehardeners and stabilizers include succinaldehyde and formaldehyde;
neutralizers can contain hydroxylamine sulfate, acetic acid, and other acids.
Formaldehyde is moderately toxic by skin contact, and highly toxic by
inhalation and ingestion. It is an skin, eye and respiratory irritant, and
strong sensitizer, and is a probable human carcinogen. Formaldehyde
solutions contain some methanol, which is highly toxic by ingestion.
Succinaldehyde is similar in toxicity to formaldehyde, but is not a strong
sensitizer or carcinogen.
Hydroxylamine sulfate is a suspected teratogen in humans since it is a
teratogen (causes birth defects) in animals. It is also a skin and eye
Concentrated acids, such as glacial acetic acid, hydrobromic acid, sulfamic
acid and p-toluenesulfonic acids are corrosive by skin contact, inhalation
solutions, if they contain sulfites or bisulfites (e.g., neutralizing
solutions), can release sulfur dioxide upon standing. If acid is carried
over on the negative or transparency from one step to another step
containing sulfites or bisulfites, then sulfur dioxide can be formed.
Potassium ferricyanide will release hydrogen cyanide gas if heated, if hot
acid is added, or if exposed to strong ultraviolet radiation.
exhaust ventilation is required for mixing of chemicals and color
processing. See previous section for discussion of ventilation.
premixed solutions whenever possible. For powders, use a glove box, or wear
a NIOSH-approved respirator with toxic dust filters.
color processes using formaldehyde, if possible.
gloves, goggles and protective apron when mixing and handling color
processing chemicals. When diluting solutions containing concentrated acids,
always add the acid to the water. An eyewash and emergency shower should be
water rinse step is recommended between acid bleach steps and fixing steps
to reduce the production of sulfur dioxide gas.
not add acid to solutions containing potassium ferricyanide or thiocyanate
Control the temperature carefully according to manufacturer's
recommendations to reduce emissions of toxic gases and vapors.
Disposal of Photochemicals
responsible for deciding what is hazardous waste and what can go down the
drain. Researchers should never put any hazardous (or even potentially
hazardous) materials down the drain without explicit permission from EH&S.
Please refer to Chapter 12
of the UCSD Lab Safety Plan,
Hazardous Waste Guide, or contact EH&S at (858) 534-2753 for hazardous
waste questions. Each PI must get a
Number to dispose of hazardous waste.
or unused concentrated photographic chemical solutions, toning solutions,
ferricyanide solutions, chromium solutions, color processing solutions,
developer, stop baths, fixing baths, and other solutions should be treated
as hazardous waste.
Unused materials may be recycled by donating it to UCSD's
dispose of photographic wastes, label them with a hazardous waste tag, store
them in secondary containment and submit a waste pickup request as outlined
in Chapter 12 of the
Lab Safety Plan and in
Never attempt to treat photographic wastes. Do not neutralize alkaline
developer solutions with stop bath or any other materials, do not attempt to
neutralize fixing baths with acids. Waste treatment in labs is not allowed
at UCSD and these operations can lead to hazardous by-products.
Fixers contain some silver, which must be treated or recovered before it can
be disposed of. There are two options available for recycling this material:
1) Have a commercial company service your photographic needs (typically
keeping your developer and fixer stocked and your waste removed), or 2) have
EH&S collect the waste. EH&S is permitted to treat the silver waste and
dispose of the treated waste.
important to remember that when handling fixers, developer, or other
photographic products that proper Personal Protective Equipment (PPE) be worn
at all times. See Chapter 10
in the Lab Safety Plan for more information regarding PPE. At a minimum, all
lab workers should wear appropriate footwear, lab coat, surgical type
disposable gloves (preferably nitrile), and safety glasses when handling these
hazardous chemicals. If you have any questions, contact EH&S at (858) 534-3660
data sheet was adapted from the 2nd edition of Dr. McCann's Artist Beware.,
Lyons and Burford (1992).
Ayers, G., Zaczkowski, J. (1991). Photo Developments - A Guide to Handling
Photographic Chemicals. Envisin Compliance, Bramalea, Ont.
Eastman Kodak Co. (1986). CHOICES - Choosing the Right Silver-Recovery
Method for Your Needs. Publication No. J-21. Eastman Kodak, Rochester.
Eastman Kodak Co. (1986). Disposal and Treatment of Photographic Effluent.
Publication No. J-55. Eatman Kodak, Rochester.
Eastman Kodak Co. (1986). Disposal of Small Volumes of Photographic
Processing Solutions. Publication No. J-52. Eastman Kodak, Rochester.
Eastman Kodak Co. (1987). General guidelines for ventilating photographic
processing areas, CIS-58. Eastman Kodak, Rochester.
Eastman Kodak Co. (1979). Safe Handling of Photographic Chemicals.
Publication No. J-4.. Kodak, Rochester.
Handley, M. (1988). Photography and Your Health. Hazard Evaluation System
and Information Service, California Department of Health Services, Berkeley.
Hodgson, M., and Parkinson, D. (1986). Respiratory disease in a
photographer. Am. J. Ind. Med. 9(4), 349-54.
C. & Hart C. (1987). Hazards in a photography lab; a cyanide incident case
study. J. Chem. Educ. 64(10), A234-A236.
H., and Lerman, Y. (1986). Respiratory abnormalities among photographic
developers: a report of three cases. Am. J. Ind. Med. 9(4), 341-347.
S. D., and Rossol, M. (1991). Overexposure: Health Hazards in Photography.
2nd ed. Allworth Press, New York.
J. (ed). (1988). Making Darkrooms Saferooms. National Press Photographers
Further Information written and telephoned inquiries about hazards in the arts
will be answered by the Art Hazards Information Center of the Center for
Safety in the Arts. Send a stamped, self-addressed envelope for a list of our
many publications. Permission to reprint this data sheet may be requested in
writing from CSA. Write: Center for Safety in the Arts, 5 Beekman Street,
Suite 820, New York, NY 10038. Telephone (212) 227-6220. CSA is partially
supported with public funds from the National Endowment for the Arts, the New
York State Council on the Arts, the New York City Department of Cultural
Affairs, and the NYS Department of Labor Occupational Safety and Health
Training and Education Program.
Copyright Center for Safety in the Arts 1994