Page 431 - Book Hosokawa Nanoparticle Technology Handbook

7.3 SAFETY OF NANOPARTICLES FUNDAMENTALS

50 50
20nm TiO 2
250nm TiO 2 40
Percent neutrophilis (%) 30 Percent neutrophils (%) 30
40
Saline control

20
20
10

0 10 0
0 500 1,000 1,500 2,000 0 50 100 150 200 250
2
(A) TiO Mass (μg) (B) TiO Surface area (cm )
2
2
Figure 7.3.4
Percentage of neutrophils in lung lavage of rats as indicators of inflammation 24h after intratracheal instillation of different
mass doses of 20 and 250 nm TiO particles in rats [3]. (A) The dose responses of two samples are different from each
2
other as mass. (B) The same response relationship is shown as particle surface area.

of different mass doses of 20 and 250 nm TiO parti- that LD50s for these elements in oral and intravenous
2
cles. The steeper dose response of nanosized TiO par- administration are in a range from several dozens to
2
ticles is observed than for submicron TiO particles several thousands milligrams per kilograms, indicating
2
when the dose is expressed as mass (Fig. 7.3.4A). If that none of these elements has high toxicity. In the
the same dose–response relationship as in Fig.7.3.4A results of studies in which the biopersistence and the
is indicated as particle surface area (Fig. 7.3.4B), the distribution of rare earth compounds in the body
particle surface area seems to be a more appropriate were investigated, for example, the compounds
dosimetric for comparing effects of different-sized deposited in bones and teeth, and organs including
particles of the same chemical structure. lung, liver, spleen and kidney following intratracheal,
Zinc oxide is a white powder and used in pigments. oral, intravenous, and intraperitoneal administration.
3
The OEL is 1 mg/m for its respirable fraction [9], Although the compounds deposited predominantly in
and the value for zinc oxide fume which causes metal the liver other than bones, it has also been reported
fume fever is under consideration. that the distribution of the compounds in the lung and
Nanoparticles of transition metals and rare earth spleen increased when the dose was increased [31].
elements and their oxides will be used widely. Since The demand for indium compounds has been
many of these metals and their oxides have biological sharply increasing. The compounds have been used in
effects, particular attention should be given to them. the materials for transparent electrodes for flat panel
Nickel compounds are rated as a human carcinogen displays. In Japan, the cases of pulmonary interstitial
(group 1) by IARC. In particular, nickel oxide is pneumonia and pulmonary fibrosis have been
particularly insoluble among the nickel compounds reported in workers engaged in cutting and grinding
and remains longer in the lung. Nanosized nickel of sintered indium–tin oxide (ITO) and potentially
oxide particles have greater toxicity to the lung than having inhaled the dusts released from ITO [32, 33].
larger particles [26, 27]. Pulmonary inflammatory The biological effects of indium arsenic compounds
responses induced by nanosized cobalt particles have and indium phosphorus compounds also have been
been reported [28–30]. Biological effects of nano- investigated. The ACGIH has proposed a value of
sized particles of other transient metals such as iron 0.1 mg/m for their TLV, and the value has been
3
and manganese have received attention [3]. applied tentatively in Japan.
Rare earth elements are a general term of 17 chem-
ical elements consisting of scandium (Sc), yttrium (Y),
and a lanthanide series of 15 elements from lanthanum
(La) to lutetium (Lu). These elements have been used References
in magnetic alloy, fluorescent and hydrogen storage
alloy. Particularly cerium oxide nanoparticles are fre- [1] The Royal Society, Nanoscience and Nanotechnologies:
quently used as a fuel additive and are incorporated in ISBN 0 85403 604 0, http://www.nanotec.org.uk/
cosmetics formulation. The potential biological and finalReport.htm (2004).
environmental effects of these elements have not suf- [2] M. Takemura: ChemoBio Integr. Manage., 1, 57–73
ficiently been investigated. It has been demonstrated (2005) (in Japanese).

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