Toward a comprehensive framework for nanomaterials: An interdisciplinary assessment of the current Environmental Health and Safety Regulation regarding the handling of carbon nanotubes

The United States has recently paid significant attention to potential environmental health and safety concerns surrounding nanomaterials. Still, there exist several policy barriers to constructing effective regulation. These policy barriers include public awareness and perception, an inadequate classification system, a deficient assessment process, and industry cooperation. While public perception and industry cooperation vary greatly by country and trade, our team finds that a critical failure in the assessment and classification processes is the insufficient testing framework for classifying environmental health and safety (EHS) risk. In large part, this is due to relative novelty of the field but is also a result of the wide variety of new and under researched variables relevant to the unique health risks posed by nanomaterials. One area we believe deserves more attention in the Environmental Protection Agency's (EPA) current approach for assessing the potential toxicity of airborne nanomaterials, specifically in regards to issues of agglomeration. To better understand the potential EHS risk associated with airborne agglomeration of nanoparticles, we examine carbon nanotubes (CNTs) a nanomaterial touted for use in several consumer technologies. The first section of this paper provides a summary of the recent approaches to EHS regulation of nanomaterials. In this section we target four main policy barriers that are hindering effective EHS regulation for the research sectors in the life cycle of nanomaterial development across several government agencies. The second section is a review of the toxicology literature on inhalation risk associated with CNTs. The third section outlines the series of aerosols tests we conducted to characterize common exposure mechanisms in terms of airborne nanotubes and to determine whether current exposure levels of carbon nanotubes are acceptable under existing industry regulation. We measure exposure levels in terms of number concentration (#/cm(3)) and mass concentration (mg/m(3)) for vertically aligned CNTs and dispersed single and multi-walled CNTs. We conclude that CNTs may pose an inhalation risk to people in a manufacturing or laboratory setting and that new OSHA exposure levels need to be set for nanomaterials to secure a safe working environment. Additionally, we believe that NIOSH needs to invest in CNT aerosol studies to better develop thorough chemical and physical test processes, understand the inhalation risks associated with nanomaterials, and build toward comprehensive framework for assessment and classification of EHS risks.