Biopersistence of inhaled MWCNT in rat lungs in a 4-week well-characterized exposure.
It is important to conduct a risk assessment that includes hazard assessment and exposure assessment for the safe production and handling of newly developed nanomaterials. We conducted an inhalation study of a multi-wall carbon nanotube (MWCNT) as a hazard assessment. Male Wistar rats were exposed to well-dispersed MWCNT for 4 weeks by whole body inhalation. The exposure concentration in the chamber was 0.37 ± 0.18 mg/m³. About 70% of the MWCNTs in the chamber were single fiber. The geometric mean diameter (geometric standard deviation, GSD) and geometric mean length (GSD) of the aerosolized MWCNTs in the chamber were 63 nm (1.5) and 1.1 μm (2.7), respectively. The amounts of MWCNT deposited in the rat lungs were determined by the X-ray diffraction method and elemental carbon analysis. The average deposited amounts at 3 days after the inhalation were 68 μg/lung by the X-ray diffraction method and 76 μg/lung by elemental carbon analysis. The calculated deposition fractions were 18% and 20% in each analysis. The amount of retained MWCNT in the lungs until 3 months after the inhalation decreased exponentially and the calculated biological half times of MWCNT were 51 days and 54 days, respectively. The clearance was not delayed, but a slight increase in lung weight at 3 days after the inhalation was observed.
Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan. toyabu@med.uoeh-u.ac.jp
Takako
T
Oyabu
Toshihiko
T
Myojo
Yasuo
Y
Morimoto
Akira
A
Ogami
Masami
M
Hirohashi
Makoto
M
Yamamoto
Motoi
M
Todoroki
Yohei
Y
Mizuguchi
Masayoshi
M
Hashiba
Byeong Woo
BW
Lee
Manabu
M
Shimada
Wei-Ning
WN
Wang
Kunio
K
Uchida
Shigehisa
S
Endoh
Norihiro
N
Kobayashi
Kazuhiro
K
Yamamoto
Katsuhide
K
Fujita
Kohei
K
Mizuno
Masaharu
M
Inada
Tetsuya
T
Nakazato
Junko
J
Nakanishi
Isamu
I
Tanaka
D000280:Administration, Inhalation; D000818:Animals; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D008297:Male; D037742:Nanotubes, Carbon; D051381:Rats; D017208:Rats, Wistar; D014018:Tissue Distribution; D059551:Toxicity Tests, Subacute; D014961:X-Ray Diffraction
D037742:Nanotubes, Carbon