|Monthly Tech-Tip |
Titanium is one of the most common components of the earth's crust, ninth in abundance. It occurs naturally as ilmenite (iron titanate) and rutile (titanium dioxide).
Titanium forms four distinct oxides: titanium monoxide (TiO), dititanium trioxide (Ti2O3), titanium dioxide (TiO2) and titanium trioxide (TiO3).
Titanium is frequently used as a white pigment for a wide range of paints, paper, inks, plastics, and the like.
Exposure results from breathing titanium dioxide dust. Possible exposure to intermediate products in titanium dioxide production may also occur.
Exposure may then occur at any stage in the mining of ores, in the preparation of titanium dioxide, and in any of the industries in which the powder is stored and used.
Titanium dioxide inhalation is the most common route of exposure. Ingestion is certainly possible when some dust accumulates on mucosal surfaces of the oropharynx and nasopharynx.
Titanium dioxide is found in the lymphatics and regional nodes that drain the lungs, indicating a slow removal by this process.
No data are available regarding oral absorption of titanium.
Titanium is excreted by the kidneys.
Titanium dioxide is an irritant to the upper airway, as are other nuisance dusts. No evidence indicates that it induces an acute inflammatory reaction at commonly seen exposure concentrations.
In workers with preexisting chronic obstructive airway disease, titanium dioxide may exacerbate symptoms.
Titanium dioxide is retained in the lungs. Particles of this dust are found also in the regional nodes draining the lungs, suggesting that these particles are slowly cleared by the lymphatics.
Little evidence indicates that titanium dioxide promotes a chronic inflammatory reaction in the lungs.
Titanium dioxide dust currently is considered to be merely a nuisance dust that results only in upper airway irritation.
No data are available regarding human genetic effects.
Evaluation by the IARC : The agent (the mixture) is possibly carcinogenic to humans Evaluation by the NIOSH and OSHA : Potential human carcinogen.
Note it is not classified as a confirmed carcinogen to man by these organisms.
Evaluation by the ACGIH: Substance not classifiable as a carcinogen to man (A4 group).
Limits of exposure
The limits of exposure proposed in the USA and Quebec do not mention this carcinogenic potential, and the limit is in relation with its irritating power.
Titanium dioxide is an irritant dust, therefore, management of exposure is supportive. Exposed workers should be removed from the environment, and supportive pulmonary care should be provided.
Most laboratory tests are not helpful. Assessement of serum and urinary titanium levels help to identify recent exposure.
Acute upper airway irritation may be reduced by keeping exposure to titanium at low limits.
Quebec's exposure limit
VEMP (Valeur d'Exposition Moyenne Pondéré) = 10 mg/m3 as total dust.
Good industrial hygiene and monitoring of the environment should limit employee exposure to titanium dust. If employees must work in an environment with high titanium dioxide dust levels and poor ventilation,respirators should be used.
Article by Edouard Bastarache
Edouard Bastarache is a well known doctor that has written many articles on the subject of toxicity of ceramic materials and books on technical aspects of ceramics. He writes in both English and French.
By Edouard Bastarache