NORA Manufacturing Sector Strategic Goals
927ZGNYa - Workplace Monitoring of Carbon Nanofibers/Nanotubes (NTRC)
Principal Investigator (PI)
Primary Goal Addressed
Secondary Goal Addressed
Attributed to Manufacturing
Direct-reading and laboratory methods are being applied to monitor air contaminants produced during carbon nanotube/nanofibers (CNT/CNF) production. In previous studies by project collaborators, workplace exposures were to a complex mixture of CNF and manufacturing byproducts. Toxic byproducts also must be considered when assessing risks. Given the rapidly changing manufacturing processes, CNT/CNF products and associated byproduct emissions can have substantially different physical, chemical, and biological properties. Studies to characterize workplace exposures are needed. This project is providing workplace monitoring data on CNT/CNF and production byproducts. Results are being used by employers to guide selection of controls and changes in work practices. A variety of commercial products also are being characterized as part of the method development effort for these materials.
Manufacturing, Nanotechnology, Exposure Assessment
Monitoring methods, field research, and exposure data for carbon nanotubes and nanofibers (CNT/CNF) are the major outputs of this project. These outputs are important Institute goals for the Nanotechnology program. Methods can be used by industrial hygienists, researchers, and employers. Exposure data and air monitoring results will guide employers selection of controls, improve work practices, and refine risk assessments. Methods and expertise will support a NIOSH Current Intelligence Bulletin and Recommended Exposure Limit (REL) for CNT. Outputs promote worker protection.
In vitro and in vivo studies indicate carbon nanotubes/nanofibers (CNT/CNF) may have serious human health effects (fibrosis, cancer). Previous field investigations identified elevated air concentrations of CNF. Toxic manufacturing byproducts also were identified. Given the variety of metal catalysts and changing manufacturing processes, these materials can have very different physical, chemical, and biological properties. The goals of this project are to develop/improve workplace monitoring methods for CNT/CNF and collect workplace monitoring data. The overall project objective is to reduce worker exposure to CNT/CNF aerosol and production byproducts. Specific aims are to: 1) conduct field and laboratory research on monitoring methods, 2) identify and characterize workplace emissions and sources, and monitor personal exposure to CNT/CNF and manufacturing byproducts, and 3) characterize the physical and chemical properties of commercial CNT/CNF products.
Field studies to characterize and quantify exposures to CNT/CNF aerosols are being conducted. Direct-reading and laboratory methods are being applied to monitor CNT/CNF and production byproducts. State-of-the-art aerosol instrumentation is being used to characterize aerosol properties (e.g., particle size distribution, aerosol surface area). The physical and chemical attributes of different particle size fractions are being investigated. Air (filters) and bulk samples are being analyzed for organic compounds, metals, and organic and elemental carbon. Transmission electron microscopy with energy dispersive spectroscopy is being used to characterize the physical attributes and metal content of the materials. Metals also are being determined by inductively coupled plasma with atomic emission spectroscopy.
Pilot field work resulted in a NIOSH HHE report and journal publication. Multiple surveys at a major CNF producer were conducted in FY08; a paper on the surveys was recently published (2010). An initial survey at a CNT manufacturer and a report to the company were completed in FY10. Findings of field surveys are being provided to the companies to guide selection of controls and improve work practices. Field and laboratory research is ongoing. Activities to be accomplished include:
Plan/conduct initial survey at CNT manufacturer (completed 1QFY10).
Conduct 2-3 surveys at CNT/CNF manufacturers (FY11)
Complete round robin on NIOSH Method 5040 (2QFY11)
Evaluate air samplers for CNT/CNF (FY11)
Diwakar, P., Kulkarni, P., Birch, M.E. (2010). Semi-continuous Measurement of Elemental Composition of Aerosol Particles Using Laser Induced Breakdown Spectroscopy. Platform presentation at the American Association for Aerosol Research (AAAR) 29th Annual Conference, Portland, OR, October 25-29, 2010.
Evans DE, Birch M.E., Ku B-K, Dunn K.H. Emissions and Exposure Monitoring During Carbon Nanofiber Production. American Industrial Hygiene Conference and Exposition (AIHce), Denver, CO, May 22-27, 2010. Completed (FY09/FY10)
Agnew R.A., Lu, M., Birch M.E., Hu J. Characterization and Size Distribution of Engineered Carbon Nanomaterials. 2010 OIS Conference, Materials and Energy: Building Blocks for Ohio's Economic Future, Columbus OH, April 20-21, 2010.
Evans DE, Ku BK, Birch M.E., Dunn K.H. Airborne Contaminants in a Carbon Nanofiber Manufacturing Facility: Direct Reading Monitoring. Poster presentation at the American Association for Aerosol Research (AAAR) 28th Annual Conference, Minneapolis, Minnesota, October 26-30, 2009 (09-083).
Birch ME, Evans DE, Ku BK, Ruda-Eberenz T. (2009). Monitoring Air Contaminants During Carbon Nanofiber Production. 28th Annual Conference of the American Association for Aerosol Research (AAAR), Minneapolis, MN, October 26-30, 2009.
Evans DE, Ku BK, Birch ME, Dunn KH. Direct Reading Monitoring of Contaminants in a Carbon Nanofiber Manufacturing Facility. 4th International Conference on Nanotechnology Occupational and Environmental Health (NanOEH2009), Helsinki, Finland. August 26-29, 2009.
Birch ME, Evans DE, Ku BK, Ruda-Eberenz T. (2009). Air Contaminants in a Carbon Nanofiber Manufacturing Facility. 4th International Conference on Nanotechnology Occupational and Environmental Health (NanOEH2009), Helsinki, Finland. August 26-29, 2009.
Evans D.E., Ku B.K., Birch M.E., Dunn, K.H . Aerosol characterization during carbon nanofiber production: mobile directreading sampling. Ann. Occup. Hyg. (In Press).
Agnew R.A., Lu M., Birch M.E. . Investigation of health relevant physical and chemical properties of select engineered carbon nanotubes. Proceedings of the American Chemical Society (ACS) National Meeting and Exposition, Boston MA, August 22-26. 2010 (accepted).
Agnew R.A., Birch M.E., Lu M., Andrews R. . Physical and chemical properties of selected commercially available carbon nanotubes. Carbon (submitted).
Birch M.E., Evans D.E., Ku B-K, Ruda-Eberenz). Monitoring air contaminants during carbon nanofiber production. In preparation for submission to Ann. Occup. Hyg. (FY11)
Birch M.E. Application of NIOSH Method 5040 to carbon nanotubes and nanofibers (CNT/CNF). In preparation for inclusion in new NIOSH CIB on CNT (FY11).
Production of carbon nanotubes and nanofibers (CNT/CNF) and composite products of these materials is increasing globally.
Annual global production of CNT is over 100,000 tons, while CNF production by a major supplier is over 70,000 pounds. CNF are generating great interest in certain industrial sectors, such as energy and electronics, where alternative materials may have limited performance or much higher cost. Worldwide, nanotechnology job projections for the year 2015 are estimated at about two million workers, with about half of these being in the United States.
High volume production of CNT/CNF is a concern for workers that handle these materials. They may be harmful when inhaled because of their size, persistence, composition, and fibrous structure. Studies in rodents suggest the possibility of serious human health effects, including lung fibrosis and possibly cancer. These findings escalate the need for field investigations to assess potential exposures to CNT/CNF. Currently, occupational exposure data are lacking. A pilot study (NIOSH) identified companies that produce/process CNT. Field research will be conducted to investigate monitoring methods and collect exposure data. The project will contribute monitoring methods and exposure data for facilities that produce/process CNT/CNF. Research findings will fill knowledge gaps on nanomaterial exposure, properties, and health risks. Methods can be applied by industrial hygienists and employers for hazard identification and personal monitoring. Data and methods can be used by NIOSH for development of occupational safety and health guidelines, and by regulatory agencies for monitoring and standards setting. Ongoing work with manufacturers is having positive impact on reducing worker exposure to CNT/CNF and harmful manufacturing byproducts such as carbon monoxide (CO) and polycyclic aromatic hydrocarbons (PAH).