2005 Progress Report: Health Effects of Inhaled NanomaterialsEPA Grant Number: R831714
Title: Health Effects of Inhaled Nanomaterials
Investigators: Pinkerton, Kent E. , Guo, Ting
Institution: University of California - Davis
EPA Project Officer: Hahn, Intaek
Project Period: July 1, 2004 through June 30, 2007
Project Period Covered by this Report: July 1, 2004 through June 30, 2005
Project Amount: $334,998
RFA: Exploratory Research to Anticipate Future Environmental Issues: Impacts of Manufactured Nanomaterials on Human Health and the Environment (2003) RFA Text | Recipients Lists
Research Category: Exploratory Research - Human Health , Health , Safer Chemicals , Nanotechnology , Health Effects
The health impact of manufactured nanomaterials is unknown. Nanomaterials are classified as particles less than 100 nm in diameter. The commercial use of these materials in society is anticipated to increase in an exponential manner for carbon nanotubes, nanowires, and silicon/metal oxides. Exposure of the general population to nanomaterials from products and from the environment through incidental introduction to the soil, water, and air is likely to occur. Little, however, is known about the environmental fate of these particles. Both epidemiological and toxicological studies on the effects of particulate air pollution support the premise that ultrafine or nanosize particles cause pulmonary inflammation as well as systemic effects; therefore, we propose to examine the effects of inhaled nanomaterials on the respiratory tract. We hypothesize that inhaled nanomaterials may produce oxidative stress and inflammation in the lungs. We further propose such events will lead to proinflammatory cytokines as well as other mediators to induce cell proliferation and alterations in the normal cellular milieu of the airways and alveoli in the lungs. The objective of this research project is to test if these health impacts of nanomaterials on the respiratory system are driven in large measure by: (1) particle size, (2) particle composition, and/or (3) trace contaminants associated with the manufacturing process of nanomaterials.
During Year 1 of this research project, we have accomplished several objectives. Nanomaterials in the form of carbon nanotubes have been synthesized in the laboratory of Dr. Ting Guo. Synthesis of this material has allowed us to test two systems for the generation of aerosolized carbon nanotubes. In addition, Dr. Guo has acquired carbon nanotubes synthesized at another institution. Using both of these materials has allowed us to determine if there are unique differences based on the type of carbon nanotubes used. We also have used carbon black as another nanomaterial that is commercially synthesized for testing of aerosolization with generation systems designed in our laboratory.
The first system tested is a dry powder aerosol generator consisting of a rotary feed belt mechanism, a fluidized bed system, a cyclone separator and a dilution control system. In the first step, test powder nanomaterials are premixed with cleaned 100 μm diameter glass beads. This mixture of material is then placed in a glass burette feed hopper, which is released into a rotating belt that conveys and discharges the mixture at a controlled rate into the fluidized bed. The fluidized bed consists of a 15 mL conical test tube into which the test material is delivered. Fluidized air is added to the conical tube at the bottom of the cone. The aerosolized mixture subsequently generated by vigorous agitation and combined with airflow passes through a cyclone that readily separates suspended test particles from the glass beads by means of the large difference in aerodynamic diameter. The test aerosol is further diluted with air as it passes through a krypton-85 charge neutralizer prior to flowing into an inhalation chamber. This system was found to be highly effective in the dispersion of carbon black materials, which allowed for the ready dispersion of small particles less than 10 μm in diameter. Although this system was not capable of creating individual carbon black particles, the aerosol generated was clearly within a respirable size range, less than 2 μm in diameter. In contrast, carbon nanotubes aerosolized using this system failed to produce a satisfactory aerosol within a range of respirable materials. Subsequent examination of the glass microspheres used to create the desegregation of these particles found that carbon nanotubes had become coated to the surface of these glass microspheres. Agitation of the microspheres within the fluidized bed system failed to release the carbon nanotubes into the atmosphere. In summary, we found that the first test of the aerosol generator was highly efficient for aerosolizing carbon black nanomaterials but failed to produce a satisfactory aerosol of carbon nanotubes.
A second method was designed due to the fact that the carbon nanotubes failed to become aerosolized using the dry test powder generator. This system consisted of a syringe plunger to feed single-walled nanotubes into the path of a rapidly rotating stainless steel brush wheel to separate carbon nanotube bundles. Aerosolization was done under airflow conditions to allow for the release of carbon nanotubes from the brush wheel into the atmosphere. This mechanical method of aerosol generation was highly effective in creating bundles of carbon nanotubes within a size range of 1 to 2 microns. These findings suggest single-walled carbon nanotubes which do not easily disaggregate under normal conditions, can be aerosolized to create respirable carbon nanotube clusters for future inhalation studies. This method has the distinct benefit of testing potential health effects of carbon nanotubes by inhalation rather than by instillation or aspiration techniques which do not represent natural physiological routes of exposure to these materials.
We plan to further develop these two aerosolization systems for more efficient aerosolization of nanomaterials to test inhalation health effects. We will continue to improve sample handling with our wire brush system to further develop the aerosolization of carbon nanotubes. Our goal in Year 2 of the research project is to improve these systems to the point that we can begin inhalation studies using small laboratory animals to test for potential respiratory health effects of inhaled nanomaterials. In addition to carbon black and carbon nanotubes, we also plan to examine ultrafine titanium dioxide as another nanomaterial for aerosolization.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 32 publications||2 publications in selected types||All 2 journal articles|
||Madl AK, Pinkerton KE. Health effects of inhaled engineered and incidental nanoparticles. Critical Reviews in Toxicology 2009;39(8):629-658.||
||Teague SV, Veranth JM, Aust AE, Pinkerton KE. Dust generator for inhalation studies with limited amounts of archived particulate matter. Aerosol Science and Technology 2005;39(2):85-91.||