More Nanoparticle Hazard Identification - Iron Oxide Added to the List

Toxicol. Sci. 2009 107: 342-351; doi:10.1093/toxsci/kfn245.
http://toxsci.oxfordjournals.org/cgi/content/abstract/107/2/342?etoc

Particokinetics and Extrapulmonary Translocation of Intratracheally Instilled Ferric Oxide Nanoparticles in Rats and the Potential Health Risk Assessment
Mo-Tao Zhu*,, Wei-Yue Feng*,1, Yun Wang*,, Bing Wang*, Meng Wang*, Hong Ouyang*, Yu-Liang Zhao* and Zhi-Fang Chai*
* Laboratory for Bio-Environmental Effects of Nanomaterials and Nanosafety and Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China Graduate School of Chinese Academy of Sciences, Beijing 100049, China
1 To whom correspondence should be addressed at P.O. Box 918, Beijing 100049, China. Fax: (8610) 88235294. E-mail: fengwy@mail.ihep.ac.cn
Abstract
Exposure to nanoparticles has presented potential risks to human cardiorespiratory systems. Pulmonary retention and extrapulmonary redistribution of inhaled nanoparticles have been considered to be important contributing factors of cardiorespiratory diseases. In the present work, 22-nm 59Fe2O3 nanoparticles (radioactive isotope 59Fe-labeled ferric oxide nanoparticles) were intratracheally instilled into the male Sprague-Dawley rats at a dose of 4 mg/rat. Extrapulmonary distribution of 59Fe2O3 in organs and its metabolism in lung, blood, urine, and feces were measured for 50 days of exposure. Phagocytosis and clearance of agglomerated nano-Fe2O3 by monocytes/macrophages were observed by histopathology and inductively coupled plasma-mass spectrometry examination. Our results showed intratracheal-instilled nano-59Fe2O3 could pass through the alveolar-capillary barrier into systemic circulation within 10 min that consisted with one-compartment kinetic model. The nano-59Fe2O3 in the lung was distributed to organs rich in mononuclear phagocytes, including liver, spleen, kidney and testicle. The plasma elimination half-life of nano-59Fe2O3 was 22.8 days and the lung clearance rate was 3.06 µg/day, indicating the systemic accumulation and lung retention had occurred. The deposited nano-Fe2O3 in interstitial lung was probably contributed by the particles escaping from alveolar macrophages phagocytosis and macrophages clearance function overloading. Our results suggest that the effect of Fe2O3 nanoparticles exposure, even at low concentration, should be assessed because of the potential lung and systemic cumulative toxicity of the nanoparticles.
Key Words: ferric oxide nanoparticle; extrapulmonary translocation; particokinetics; lung retention; health risk assessment.
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BrooklynDodger(s) comment: By now, the question of whether nanoparticles are absorbed from the respiratory tract, translocated systemically and enter cells should be settled. Yes they can! Toxic potential and potency plausibly has a physical component - independent of chemistry - and a chemical specific component. The Dodger(s) would buy carbon black and titanium dioxide - Group 2B carcinogens - as the baselines for comparison of other species. Iron oxide (not metallic iron) particles might be pretty potent - iron oxide getting loose in the cell likely promotes redox-cycling and oxidative damage.

Welding fume contains iron oxide particles, it would be worthwhile assessing particle size, the time course of particle size and the size distribution of particles reaching the alveolar surface.