- Summary, What
should be known, French
- On this page :
Thorium dioxide by Edouard Bastarache, Bioxyde
de Thorium par Édouard Bastarache
- Identification and Uses
- CAS Number :1314-20-1
- Thorium Dioxide is a heavy,
white, crystalline (sand-like) powder.
- It is used in :
- -in nuclear fuels,
- -as a catalyst,
- -in electrodes for arc
- Thorium Dioxide emits alpha
particles which can be breathed in and
- I-Acute Health Effects
- Exposure can reduce the
ability of the bone marrow to make white blood
- II-Chronic Health
- Thorium Dioxide is a
carcinogen in humans. It has been shown to cause
angiosarcoma, liver and kidney tumors, lymphoma and
other tumors of the blood system, and tumors at the
site of application.
- B-Reproductive Hazard
- Thorium Dioxide has not been
tested for its ability to affect reproduction.
- Because Thorium Dioxide
gives off very dangerous radiation, it has the
potential for causing reproductive damage in
- C-Other Long-Term Effects
- Overexposure can occur with
no acute symptoms.
- Low repeated exposures may
scar the lungs.
- After exposure, some Thorium
Dioxide is retained in the bones, lymph system, lungs
and other body organs for many years.
- Exposure may damage the
liver and kidneys.
- Any evaluation should
include a careful history of past and present symptoms
with a physical examination.
- Before beginning employment
and at regular times after that, the following are
- -White blood cell
- -Lung function test.
- -Consider periodic chest
x-ray for persons with potentially high or repeated
- If symptoms develop or
overexposure is suspected, the following may be useful
- -Liver and kidney function
- Medical tests that look for
damage already done are not a substitute for
- Ways of
Reducing Exposure :
- I-Enclose operations and use
local exhaust ventilation at the site of chemical
release. If local exhaust ventilation or enclosure is
not used, respirators should be worn.
- II-A regulated, marked area
should be established where Thorium Dioxide is
handled, used, or stored.
- III-All processes involving
Thorium Dioxide should be mechanized, enclosed or
- IV-When working with small
quantities of Thorium Dioxide, use in a glove
- V-Wear protective work
- VI-Wash thoroughly
immediately after exposure to Thorium Dioxide and at
the end of the workshift.
- VII-Post hazard and warning
information in the work area. In addition, as part of
an ongoing education and training effort, communicate
all information on the health and safety hazards of
Thorium Dioxide to potentially exposed workers.
Controls and Practices :
- Unless a less toxic chemical
can be substituted for a hazardous substance,
controls are the most
effective way of reducing exposure.
- The best protection is to
enclose operations and/or provide local exhaust
ventilation at the site of radiation release.
Isolating operations can also reduce exposure. Using
respirators or protective equipment is less effective
than the controls mentioned above, but is sometimes
- In evaluating the controls
present in your workplace, consider:
- -how hazardous the substance
- -how much of the substance
is released into the workplace and
- -whether harmful skin or eye
contact could occur. Special controls should be in
place for highly toxic chemicals or when significant
skin, eye, or breathing exposures are possible.
Recommended Controls :
- A-Automatically transfer
Thorium Dioxide from drums or other storage containers
to process containers.
- B-Specific engineering
controls and personnel monitoring are required
according to local legislation.
- II-Work practices
- Good work practices can help
to reduce hazardous exposures. The following work
practices are recommended:
- A-Workers whose clothing has
been contaminated by Thorium Dioxide should change
into clean clothing promptly.
- B-Do not take contaminated
work clothes home. Family members could be
- C-Contaminated work clothes
should be laundered by individuals who have been
informed of the hazards of exposure to Thorium
- D-If there is the
possibility of skin exposure, emergency shower
facilities should be provided.
- E-On skin contact with
Thorium Dioxide, immediately wash or shower to remove
the chemical. At the end of the workshift, wash any
areas of the body that may have contacted Thorium
Dioxide, whether or not known skin contact has
- F-Do not eat, smoke, or
drink where Thorium Dioxide is handled, processed, or
stored, since the chemical can be swallowed. Wash
hands carefully before eating or smoking.
- G-Employees exposed to
ionizing radiation should be provided with personal
monitoring equipment such as film badges or pocket
- H-Use damp methods to
control dust. Test for trace levels of radioactivity
Protective Equipment :
- Workplace controls are
better than personal protective equipment.
- However, for some jobs (such
as outside work, confined space entry, jobs done only
once in a while, or jobs done while workplace controls
are being installed), personal protective equipment
may be appropriate
- The following
recommendations are only guidelines and may not apply
to every situation.
- A-Avoid skin contact with
Thorium Dioxide. Wear protective gloves and clothing.
Safety equipment suppliers/manufacturers can provide
recommendations on the most protective glove/clothing
material for your operation.
- B-All protective clothing
(suits, gloves, footwear, headgear) should be clean,
available each day, and put on before work
- II-Eye Protection
- -Wear dust-proof goggles and
face shield when working with powders or dust, unless
full facepiece respiratory protection is worn.
- Improper use of
respirators is dangerous :
- Such equipment should only
be used if the employer has a written program that
takes into account workplace conditions, requirements
for worker training, respirator fit testing and
- medical exams.
- Engineering controls must be
effective to ensure that exposure to Thorium Dioxide
does not occur.
- At any exposure level, use
an approved supplied-air respirator with a full
facepiece or use an approved self-contained breathing
apparatus with a full facepiece operated in
pressure-demand or other positive pressure
- First Aid
- I-Eye Contact
- Immediately flush with large
amounts of water for at least 15 minutes, occasionally
lifting upper and lower lids.
- II-Skin Contact
- Quickly remove contaminated
clothing. Immediately wash contaminated skin with soap
and large amounts of water
- Remove the person from
- Begin rescue breathing if
breathing has stopped and CPR if heart action has
- Transfer promptly to a
Exposure Limits :
- Exposure to radioactive
materials is regulated by local legislation.
- Thorium Dioxide is a
carcinogen in humans. There may be no safe level of
exposure to a carcinogen, so all contact should be
reduced to the lowest possible level.
- References :
Medicine,Carl Zenz, last edition.
- 2-Clinical Environmental
Health and Toxic Exposures, Sullivan & Krieger;
- 3-Sax's Dangerous
Properties of Industrial Materials, Lewis C., last
Industrielle et Intoxications Professionnelles,
Lauwerys R.R. last edition.
- 5-Chemical Hazards of the
Workplace, Proctor & Hughes, 4th
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