Twenty‐eight‐day repeated inhalation toxicity study of nano‐sized lanthanum oxide in male sprague‐dawley rats

Abstract

Although the use of lanthanum has increased in field of high-tech industry worldwide, potential adverse effects to human health and to the environment are largely unknown. The present study aimed to investigate the potential toxicity of nano-sized lanthanum oxide (La O ) following repeated inhalation exposure in male Sprague-Dawley rats. Male rats were exposed nose-only to nano-sized La O for 28 days (5 days/week) at doses of 0, 0.5, 2.5, and 10 mg/m . In the experimental period, we evaluated treatment-related changes including clinical signs, body weight, hematology, serum biochemistry, necropsy findings, organ weight, and histopathology findings. We also analyzed lanthanum distribution in the major organs and in the blood, bronchoalveolar lavage fluids (BALF), and oxidative stress in lung tissues. Lanthanum level was highest in lung tissues and showed a dose-dependent relation. Alveolar proteinosis was observed in all treatment groups and was accompanied by an increase in lung weight; moreover, lung inflammation was observed in the 2.5 mg/m and higher dose groups and was accompanied by an increase in white blood cells. In the BALF, total cell counts including macrophages and neutrophils, lactate dehydrogenase, albumin, nitric oxide, and tumor necrosis factor-alpha increased significantly in all treatment groups. Furthermore, these changes tended to deteriorate in the 10 mg/m group at the end of the recovery period. In the present experimental conditions, we found that the lowest-observed-adverse-effect level of nano-sized La O was 0.5 mg/m in male rats, and the target organ was the lung. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1226-1240, 2017.

Twenty-Eight-Day Repeated Inhalation Toxicity Study of Nano-Sized Neodymium Oxide in Male Sprague-Dawley Rats

“…However, systemic changes including abnormal clinical signs and changes in body weight were not observed. These results were similar to those obtained in a previous inhalation toxicity study using nano-sized La 2 O 3 in rats (23). …”

“…Therefore, it was thought that nano-sized Nd 2 O 3 may require a longer elimination time than nano-sized CeO 2 and La 2 O 3 under the same conditions. Neodymium in blood was detected at low levels with no dose-dependent relationship, which corresponded with the results of previous studies using La 2 O 3 (21,23). Therefore, longer studies, or additional studies on kinetics, should be considered to identify a clear dose-dependent relationship and to elucidate this result.…”

“…The percentage decrease was 21, 34, and 34% in the 0.5, 2.5, and 10 mg/m 3 treatment groups, respectively, after the 28-day recovery period, and the half-life of nano-sized Nd 2 O 3 in the lung was calculated to be 83, 47, and 47 days, respectively. In previous studies, the half-life of nano-sized cerium oxide (CeO 2 ) and La 2 O 3 in the lung was calculated as 40 and 55 days, respectively, in rats exposed to 0.5 mg/m 3 for 4 weeks (20,23). Therefore, it was thought that nano-sized Nd 2 O 3 may require a longer elimination time than nano-sized CeO 2 and La 2 O 3 under the same conditions.…”

Twenty-Eight-Day Repeated Inhalation Toxicity Study of Aluminum Oxide Nanoparticles in Male Sprague-Dawley Rats

“…In this study, we evaluated the inhalation toxicity of Al 2 O 3 NPs using a nose-only inhalation system in SD rats. Exposure conditions to Al 2 O 3 NPs were in accordance with the OECD test guidelines for 28-day inhalation toxicity studies ( 12 ), with exposure concentrations selected based on the results of a previous inhalation study of metal nanomaterials that included rare earth metals and Al 2 O 3 ( 10 , 11 ). Male rats were preferentially used since men primarily work in environments prone to nanomaterial exposure.…”

“…Four groups of SD rats were exposed to Al 2 O 3 NPs for 28 days (6 hr/day, 5 days/week) at doses of 0, 0.2, 1, and 5 mg/m 3 . These doses were selected based on the results of a previous repeated inhalation toxicity study of metal NPs, including neodymium oxide, cerium oxide, and lanthanum oxide ( 10 , 11 ).…”