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Trace Elements in Abiotic and Biotic Environments
of Sweden contain Ti within the range of 0.17–0.25 mg/kg (Eriksson 2001a). Some
weeds, especially horsetail and nettle may accumulate more Ti, up to 80 mg/kg.
51.6 HUMANS
Titanium content in human body is estimated to be 700  mg, at concentrations in
blood, 50 μg/L; bones, 40 mg/kg; and other tissues, 1–2  mg/kg (Emsley 2011).
Titanium does not play a significant role in any body functions and is relatively nontoxic, because the body can tolerate relatively high doses, and it is not accumulated.
Titanium halogen intake causes nausea and vomiting, and acidifies the body after its
resorption. Corrosion occurs at eye or skin, when it comes in contact with mucous
membranes. Breathing of Ti dioxide (TiO 2 ), in very small particle size, may affect
lung disease.
Titanium metal, in surgical implants, is well tolerated by tissues. Its compounds
are generally considered to be poorly absorbed, upon ingestion and inhalation. However, detectable amounts of Ti can be found in the blood, brain, and parenchymatous
organs in the general population; the highest concentrations are found in the hilar
lymph nodes and the lung. Titanium crosses the blood–brain barrier, and is also
transported through the placenta into the fetus. It seems to accumulate with age in
the lungs, but not in other organs. The biological half-life for Ti in man has been
calculated to be about 640 days. It is excreted with urine.
Titanium and its compounds presence in various environmental media, as well
as in implants, are not of any health risks (WHO 1982). Small amounts of Ti, occasionally released from implants into adjacent tissues, have not caused any adverse
effects. TiO 2 dust, when inhaled, has been classified by the International Agency for
Research on Cancer (IARC), as a Group 2B carcinogen, which means that it is possibly carcinogenic to humans (IARC 2013).
Food is the principal source of exposure to Ti for humans. Whole grains, some
vegetables and fruits, and common fish meat contained little, or not detectable
Ti amount, while milled cereal grains, butter, corn oil, and lettuce may have its
elevated levels. High levels of Ti in food, especially in cheese, can arise from the
use of TiO 2 , as a whitener in the manufacture of several cheeses (WHO 1982).
The foods with the highest content of TiO 2 included candies, sweets, and chewing gums, which indicates that children are having the highest exposure to TiO 2 .
Typical exposure for adults in the United States may be in the order of 1 mg Ti/kg
BW/day.
In several high-consumption pharmaceuticals, Ti contents range from below the
detection limit (0.0001 mg Ti/kg) to a high level of 0.014 mg Ti/kg. Food-grade TiO 2
(E171) is approximately at 36%, in the particles less than 100 nm, and thus it readily
disperses in water as a fairly stable colloids (Weir et al. 2012).
Conventionally, TiO 2 fine particles (FPs) have been considered as a low toxicity material. TiO 2 nanoparticles (NPs) possess different physicochemical properties,
compared to their FP. TiO 2 NPs may translocate to systemic organs, from the lung
and gastrointestinal tract (GIT), although the rate of translocation appears low.
In the field of nanomedicine, intravenous injection can deliver TiO 2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO 2 NPs