[pure-silver] Hydroquinone

   I got curious just what hazards Hydroquinone poses. The 
following is from various sources as given.

Mallenkrodt-Baker MSDS:

Potential Health Effects
---------------------------------- 

Inhalation:
Causes irritation to the respiratory tract. Symptoms may 
include coughing, shortness of breath. Systemic effects have 
not been proven by this route.
Ingestion:
Highly Toxic. May cause hyperactivity, stupor, fall in blood 
pressure, hyperpnea, abdominal pain, diarrhea, intense 
thirst, sweating, tinnitis, nausea, dizziness, a sensation 
of suffocation, an increased rate of respiration, vomiting, 
pallor, muscular twitching, headache, cyanosis, delirium, 
and collapse (from respiratory failure). Estimated lethal 
dose lies between 5 to 12 grams (usually because of 
respiratory failure from methemoglobin formation which 
leaves the blood unable to carry oxygen). May cause green to 
brownish-green urine.
Skin Contact:
Causes severe irritation, redness and pain. Alkaline 
solutions can cause skin sensitization.
Eye Contact:
Causes severe irritation and possible corneal ulceration.
Chronic Exposure:
Repeated exposure to vapor or dust (typically 10 to 30 
mg/m3) for > 5 years has caused brownish staining of the 
conjunctiva which may be followed by changes to the cornea 
leading to loss of visual acuity. Repeated exposure may also 
cause skin effects.
Aggravation of Pre-existing Conditions:
Persons with pre-existing skin or eye disorders or impaired 
respiratory function may be more susceptible to the effects 
of this substance.

From another M-B MSDS:
11. Toxicological Information

  Oral rat LD50: 320 mg/kg; investigated as a tumorigen, 
mutagen, reproductive effector.

  --------\Cancer 
Lists\------------------------------------------------------
                                         ---NTP 
Carcinogen---
  Ingredient                             Known 
Anticipated    IARC Category
  ------------------------------------   -----    ----------- 
    -------------
  Hydroquinone (123-31-9)                 No          No 
3
From Fisher Scientific MSDS:



EMERGENCY OVERVIEW
Appearance: colorless, light tan, or light gray crystals. 
Warning! Harmful if swallowed. May cause allergic skin 
reaction. This substance has caused adverse reproductive and 
fetal effects in animals. May cause cancer based on animal 
studies. May cause digestive tract irritation with nausea, 
vomiting, and diarrhea. Light sensitive. Air sensitive. 
Causes eye and skin irritation. May cause respiratory tract 
irritation. May cause dermatitis. May cause 
methemoglobinemia.
Target Organs: Central nervous system, respiratory system.


Potential Health Effects
Eye: May cause eye irritation. Repeated exposure may cause 
corneal abnormalities including structural changes and 
brownish discoloration which can lead to decreased visual 
acuity and blindness.
Skin: Causes severe skin irritation. May cause skin 
sensitization, an allergic reaction, which becomes evident 
upon re-exposure to this material. May cause dermatitis. 
Repeated exposure may cause hyperpigmentation of fair skin 
and depigmentation of dark skin.
Ingestion: May cause severe irritation of the digestive 
tract. May be harmful if swallowed. May cause dizziness, 
nausea, sense of suffocation, increased respiratory rate, 
vomiting, pallor, muscle twitching, cyanosis (bluish 
discoloration of skin due to deficient oxygenation of the 
blood), delirium, collapse. May cause green or brownish 
green urine which continues to darken upon standing.
Inhalation: May cause respiratory tract irritation. Causes 
narcotic effects including headache, dizziness, weakness, 
unconsciousness, and possible death. Vapors may cause 
dizziness or suffocation. Inhalation of dust may cause 
respiratory tract irritation. Exposure to high concentration 
of vapor may caues irritation, photophobia, tearing, and 
corneal ulceration.
Chronic: Prolonged or repeated skin contact may cause 
sensitization dermatitis and possible destruction and/or 
ulceration.

   And:



      Section 12 - Ecological Information




Ecotoxicity: Fish: Rainbow trout: LC50 = 0.097 mg/L; 96 Hr.; 
UnspecifiedFish: Fathead Minnow: LC50 = 0.1-0.18 mg/L; 96 
Hr.; UnspecifiedBacteria: Phytobacterium phosphoreum: EC50 
=0.77-3.97 mg/L; 5,15,30 minutes; Microtox test No data 
available.
Environmental: Substance has a high biological oxygen 
demand, and a high potential to affect aquatic organisms. 
Substance readily biodegrades, and is not likely to 
bioconcentrate.
Physical: No information available.
Other: None.

And:

Epidemiology: Substance may be involved in cancer-forming 
processes.

From Eastman Kodak MSDS:

=====================  Ecological Information 
=====================

Ecological:HIGH BIOCHEMICAL OXYGEN DEMAND, A POTENTIAL TO 
CAUSE OXYGEN
    DEPLETION IN AQUEOUS SYSTEMS, A HIGH POTENTIAL TO AFFECT 
SOME
    AQUATIC ORGANISMS, A MODERATE POTENTIAL TO AFFECT 
SECONDARY WASTE
    TREATMENT MI CROBIAL METABOLISM, A MODERATE POTENTIALTO 
AFFECT
    GERMINATION OF SOME PLANTS, A MODERATE POTENTIAL TO 
AFFECT GROWTH
    OF SOME PLANT, A HIGH POTENTIAL TO BIODEGRADE, A HIGH 
POTENTIAL TO
    PHOTOCHEMICALLY O R CHEMICALLY DEGRADE, A LOW POTENTIAL 
TO
    BIOCONCENTRATE. AFTER DILUTION WITH A LARGE AMOUNT OF 
WATER,
    FOLLOWED BY SECONDARY WASTE  TREATMENT, THIS MATERIAL IS 
NOT
    EXPECTED TO CAUSE ADVERSE ENVIRONMENT AL  EFFECTS.

     Some MSDS indicate that Hydroquinone is _suspected_ of 
being a contributing carcinogen to some animal cancers. I 
have been unable to find the exact source or the relation 
this has to human carcinogenicity. I suspect the hazard is 
small. Remember that MSDS are meant to cover users of very 
large quantities of a substance. They are also _legal_ not 
_scientific_ docments meant to protect the issuer from legal 
jeapordy. They must be interpreted with this in mind.

     Hydroquinone sould be handled with care. The 
protections recommended are similar to those for other 
substances which pose hazards in airborne condition. Wear a 
dust mask, a face protector or goggles, wear gloves, wear 
protective clothing. Work in a well ventillated place. Work 
in a way that minimises the chance of the substance becoming 
airborne. In general, minimise contact with the substance.

A saftey booklet about Hydroquinone published by the state 
of New Jersey may be found at:

http://www.state.nj.us/health/eoh/rtkweb/1019.pdf

A report on an extensive research program on the health 
hazards of Hydroquinone may be found at:

http://www.inchem.org/documents/ehc/ehc/ehc157.htm



---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx









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