Engineered carbonaceous nanomaterials manufacturers in the United States: Workforce size, characteristics, and feasibility of epidemiologic studies

Division of Surveillance, Hazard Evaluations, and Field Studies, Industrywide Studies Branch, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, MS-R15, Cincinnati, OH 45226, USA.
Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine (Impact Factor: 1.63). 06/2011; 53(6 Suppl):S62-7. DOI: 10.1097/JOM.0b013e31821b1e2c
Source: PubMed


Toxicology studies suggest that carbon nanotube (CNT) exposures may cause adverse pulmonary effects. This study identified all US engineered carbonaceous nanomaterial (ECN) manufacturers, determined workforce size and growth, and characterized the materials produced to determine the feasibility of occupational ECN exposure studies.
Eligible companies were identified; information was assembled on the companies and nanomaterials they produced; and the workforce size, location, and growth were estimated.
Sixty-one companies manufacturing ECN in the United States were identified. These companies employed at least 620 workers; workforce growth was projected at 15% to 17% annually. Most companies produced or used CNT. Half the eligible companies provided information about material dimensions, quantities, synthesis methods, and worker exposure reduction strategies.
Industrywide exposure assessment studies appear feasible; however, cohort studies are likely infeasible because of the small, scattered workforce.

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    • "The inhalation study utilized the MWCNT produced by Hodogaya, commonly referred to as the Mitsui MWCNT or MWNT-7. This particular product was utilized for several reasons: 1.) A majority of the U.S. workforce handling carbonaceous nanomaterials primarily produces or utilizes MWCNT [15]. 2.) Economically, the global market showed that CNT represents 28% of the total engineered nanomaterial market share with MWCNT being 94% of the total CNT production value ( "
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    ABSTRACT: Dosimetry for toxicology studies involving carbon nanotubes (CNT) is challenging because of a lack of detailed occupational exposure assessments. Therefore, exposure assessment findings, measuring the mass concentration of elemental carbon from personal breathing zone (PBZ) samples, from 8 U.S.-based multi-walled CNT (MWCNT) manufacturers and users were extrapolated to results of an inhalation study in mice. Upon analysis, an inhalable elemental carbon mass concentration arithmetic mean of 10.6 mug/m3 (geometric mean 4.21 mug/m3) was found among workers exposed to MWCNT. The concentration equates to a deposited dose of approximately 4.07 mug/d in a human, equivalent to 2 ng/d in the mouse. For MWCNT inhalation, mice were exposed for 19 d with daily depositions of 1970 ng (equivalent to 1000 d of a human exposure; cumulative 76 yr), 197 ng (100 d; 7.6 yr), and 19.7 ng (10 d; 0.76 yr) and harvested at 0, 3, 28, and 84 d post-exposure to assess pulmonary toxicity. The high dose showed cytotoxicity and inflammation that persisted through 84 d after exposure. The middle dose had no polymorphonuclear cell influx with transient cytotoxicity. The low dose was associated with a low grade inflammatory response measured by changes in mRNA expression. Increased inflammatory proteins were present in the lavage fluid at the high and middle dose through 28 d post-exposure. Pathology, including epithelial hyperplasia and peribronchiolar inflammation, was only noted at the high dose. These findings showed a limited pulmonary inflammatory potential of MWCNT at levels corresponding to the average inhalable elemental carbon concentrations observed in U.S.-based CNT facilities and estimates suggest considerable years of exposure are necessary for significant pathology to occur at that level.
    Full-text · Article · Oct 2013 · Particle and Fibre Toxicology
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    • "A total of six site visits were conducted between May and September of 2010 at primary and secondary manufacturers of CNTs or CNFs. These companies were recruited from a previous NIOSH survey on engineered carbonaceous nanomaterials (Dahm et al., 2011; Schubauer-Berigan et al., 2011). Of the six companies that agreed to participate, three were primary manufacturers of MWCNTs, DWCNTs, or SWCNTs (coded as Sites A–C). "
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    ABSTRACT: RESEARCH SIGNIFICANCE: Toxicological evidence suggests the potential for a wide range of health effects, which could result from exposure to carbon nanotubes (CNTs) and carbon nanofibers (CNFs). The National Institute for Occupational Safety and Health (NIOSH) has proposed a recommended exposure limit (REL) for CNTs/CNFs at the respirable size fraction. The current literature is lacking exposure information, with few studies reporting results for personal breathing zone (PBZ) samples in occupational settings. To address this gap, exposure assessments were conducted at six representative sites identified as CNT/CNF primary or secondary manufacturers. Personal and area filter-based samples were collected for both the inhalable mass concentration and the respirable mass concentration of elemental carbon (EC) as well as CNT structure count analysis by transmission electron microscopy to assess exposures. When possible, full-shift PBZ samples were collected; area samples were collected on a task-based approach. The vast majority of samples collected in this study were below the proposed REL (7 μg m(-3)). Two of the three secondary manufacturers' surveyed found concentrations above the proposed REL. None of the samples collected at primary manufacturers were found to be above the REL. Visual and microscopy-based evidence of CNTs/CNFs were found at all sites, with the highest CNT/CNF structure counts being found in samples collected at secondary manufacturing sites. The statistical correlations between the filter-based samples for the mass concentration of EC and CNT structure counts were examined. A general trend was found with a P-value of 0.01 and a corresponding Pearson correlation coefficient of 0.44. CNT/CNF concentrations were above the proposed NIOSH REL for PBZ samples in two secondary manufacturing facilities that use these materials for commercial applications. These samples were collected during dry powder handling processes, such as mixing and weighing, using fairly large quantities of CNTs/CNFs.
    Full-text · Article · Dec 2011 · Annals of Occupational Hygiene
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    ABSTRACT: Nanotechnology presents the possibility of revolutionizing many aspects of our lives. People in many settings (academic, small and large industrial, and the general public in industrialized nations) are either developing or using engineered nanomaterials (ENMs) or ENM-containing products. However, our understanding of the occupational, health and safety aspects of ENMs is still in its formative stage. A survey of the literature indicates the available information is incomplete, many of the early findings have not been independently verified, and some may have been over-interpreted. This review describes ENMs briefly, their application, the ENM workforce, the major routes of human exposure, some examples of uptake and adverse effects, what little has been reported on occupational exposure assessment, and approaches to minimize exposure and health hazards. These latter approaches include engineering controls such as fume hoods and personal protective equipment. Results showing the effectiveness - or lack thereof - of some of these controls are also included. This review is presented in the context of the Risk Assessment/Risk Management framework, as a paradigm to systematically work through issues regarding human health hazards of ENMs. Examples are discussed of current knowledge of nanoscale materials for each component of the Risk Assessment/Risk Management framework. Given the notable lack of information, current recommendations to minimize exposure and hazards are largely based on common sense, knowledge by analogy to ultrafine material toxicity, and general health and safety recommendations. This review may serve as an overview for health and safety personnel, management, and ENM workers to establish and maintain a safe work environment. Small start-up companies and research institutions with limited personnel or expertise in nanotechnology health and safety issues may find this review particularly useful.
    Full-text · Article · Mar 2011 · Journal of Occupational Medicine and Toxicology
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