Comparison of Toxicity and Deposition of Nano-Sized Carbon Black Aerosol Prepared With or Without Dispersing Sonication

Nanotoxicological research has shown toxicity of nanomaterials to be inversely related to particle size. However, the contribution of agglomeration to the toxicity of nanomaterials has not been sufficiently studied, although it is known that agglomeration is associated with increased nanomaterial size. In this study, we prepared aerosols of nano-sized carbon black by 2 different ways to verify the effects of agglomeration on the toxicity and deposition of nano-sized carbon black. The 2 methods of preparation included the carbon black dispersion method that facilitated clustering without sonication and the carbon black dispersion method involving sonication to achieve scattering and deagglomeration. Male Sprague-Dawley rats were exposed to carbon black aerosols 6 hr a day for 3 days or for 2 weeks. The median mass aerodynamic diameter of carbon black aerosols averaged 2.08 microm (for aerosol prepared without sonication; group N) and 1.79 microm (for aerosol prepared without sonication; group S). The average concentration of carbon black during the exposure period for group N and group S was 13.08 +/- 3.18 mg/m3 and 13.67 +/- 3.54 mg/m3, respectively, in the 3-day experiment. The average concentration during the 2-week experiment was 9.83 +/- 3.42 mg/m3 and 9.08 +/- 4.49 mg/m3 for group N and group S, respectively. The amount of carbon black deposition in the lungs was significantly higher in group S than in group N in both 3-day and 2-week experiments. The number of total cells, macrophages and polymorphonuclear leukocytes in the bronchoalveolar lavage (BAL) fluid, and the number of total white blood cells and neutrophils in the blood in the 2-week experiment were significantly higher in group S than in normal control. However, differences were not found in the inflammatory cytokine levels (IL-1beta, TNF-alpha, IL-6, etc.) and protein indicators of cell damage (albumin and lactate dehydrogenase) in the BAL fluid of both group N and group S as compared to the normal control. In conclusion, carbon black aerosol generated by sonication possesses smaller nanoparticles that are deposited to a greater extent in the lungs than is aerosol formulated without sonication. Additionally, rats were narrowly more affected when exposed to carbon black aerosol generated by sonication as compared to that produced without sonication.

Effects of Nano-sized Carbon Black on the Lungs of High Fat-diet Induced Overweight Rats

OBJECTIVES: This study was conducted to determine whether nano-sized carbon black exposure results in greater damage in high fat diet-induced overweight rats than normal weight ones and to identify the possible causes of any differences. METHODS: Two groups of Sprague-Dawley rats allocated by body weight (normal and overweight) were exposed to aerosolized nano-sized carbon black for 6 hours a day, 5 days per week over a 4-week period. Differential cell counts, lactate dehydrogenase (LDH) activities and albumin concentrations were measured in bronchoalveolar lavage (BAL) fluid, and histopathological findings in the lungs were evaluated. Tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 were measured in BAL fluid and supernatants of lipopolysaccharide(LPS)-stimulated lymphocyte culture. RESULTS: Rats exposed to high concentrations of nano-sized carbon black showed significantly increased (p<0.05) polymorphonuclear leukocyte number and LDH activity in the BAL fluid from both overweight and normal rats. Mild histopathological changes were observed in normal rats irrespective of carbon black concentrations. However, severe histological scores were found in overweight rats (1.75+/-0.46, 2.25+/-0.46, and 2.88+/-0.35 after low, medium, and high concentration exposures). Proinflammatory cytokine levels of TNF-alpha and IL-6 were significantly higher in the supernatant of LPS-stimulated lymphocytes of overweight rats, whereas there was no significant difference in the BAL fluid between normal and overweight rats. CONCLUSIONS: Inflammation and damage to lungs exposed to nano-sized carbon black was more severe in high fat diet-induced overweight rats compared to normal rats.

Effect of Agglomeration on the Toxicity of Nano-sized Carbon Black in Sprague-Dawley Rats

OBJECTIVES: Recent studies have shown that nano-sized carbon black is more toxic than large respirable carbon black because of its higher surface area. However, it is not clear if carbon black made larger by agglomeration demonstrates decreased toxicity. The purpose of this study was to verify if agglomeration affects the toxicity of carbon black using three differently prepared nano-sized carbon black aerosols in nose-only inhalation chambers for 13 weeks. METHODS: Printex 90 was selected as a representative nano-sized carbon black. To generate aerosols of three different types of agglomerates, Printex 90 was dispersed in distilled water by three different methods: vortex, vortex+sonication, and vortex+sonication with dispersion in a stabilizer. Then, the three differently prepared solutions were aerosolized through venturi nozzles. Male Sprague-Dawley rats were exposed to Printex 90 aerosols in a nose-only exposure chamber for 6 h/d, 5 d/wk for 13 weeks at a concentration of approximately 9 mg/m3. RESULTS: Numbers of total cells in the bronchoalveolar lavage (BAL) fluid, macrophages, and polymorphonuclear leukocytes were increased and carbon black masses were clearly seen in BAL cells and lung tissues of rats exposed to Printex 90. However, few differences were found between the three differently agglomerated aerosols. In addition, there were no significant differences in other parameters, such as body weight, lung function or cytokine levels in BAL fluid following carbon black exposure. CONCLUSIONS: Only mild to moderate respiratory effects were found in rats exposed to nano-sized carbon black at 9 mg/m3 for 13 weeks. Agglomeration did not affect the toxicity of nano-sized carbon particles.