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Characterizing Adoption of Precautionary Risk Management Guidance for Nanomaterials, an Emerging Occupational Hazard a
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Mary K. Schubauer-Berigan , Matthew M. Dahm , Paul A. Schulte , Laura Hodson & Charles L. Geraci
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Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio b
Education and Information Division, National Institute for Occupational Safety and Health, Cincinnati, Ohio Accepted author version posted online: 05 Aug 2014.Published online: 20 Nov 2014.
Click for updates To cite this article: Mary K. Schubauer-Berigan, Matthew M. Dahm, Paul A. Schulte, Laura Hodson & Charles L. Geraci (2015) Characterizing Adoption of Precautionary Risk Management Guidance for Nanomaterials, an Emerging Occupational Hazard, Journal of Occupational and Environmental Hygiene, 12:1, 69-75, DOI: 10.1080/15459624.2014.946515 To link to this article: http://dx.doi.org/10.1080/15459624.2014.946515
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Journal of Occupational and Environmental Hygiene, 12: 69–75 ISSN: 1545-9624 print / 1545-9632 online DOI: 10.1080/15459624.2014.946515
Characterizing Adoption of Precautionary Risk Management Guidance for Nanomaterials, an Emerging Occupational Hazard Mary K. Schubauer-Berigan,1Matthew M. Dahm,1 Paul A. Schulte,2 Laura Hodson,2 and Charles L. Geraci2 1
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Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio 2 Education and Information Division, National Institute for Occupational Safety and Health, Cincinnati, Ohio
Exposure to engineered nanomaterials (substances with at least one dimension of 1–100 nm) has been of increased interest, with the recent growth in production and use of nanomaterials worldwide. Various organizations have recommended methods to minimize exposure to engineered nanomaterials. The purpose of this study was to evaluate available data to examine the extent to which studied U.S. companies (which represent a small fraction of all companies using certain forms of engineered nanomaterials) follow the guidelines for reducing occupational exposures to engineered nanomaterials that have been issued by the National Institute for Occupational Safety and Health (NIOSH) and other organizations. Survey data, field reports, and field notes for all NIOSH nanomaterial exposure assessments conducted between 2006 and 2011 were collected and reviewed to: (1) determine the level of adoption of precautionary guidance on engineering controls and personal protective equipment (PPE), and (2) evaluate the reliability of companies’ self-reported use of engineering controls and PPE. Use of PPE was observed among 89% [95% confidence interval (CI): 76%–96%] of 46 visited companies, and use of containment-based engineering controls for at least some processes was observed among 83% (95% CI: 76%–96%). In on-site evaluations, more than 90% of the 16 engineered carbonaceous nanomaterial companies that responded to an industrywide survey were observed to be using engineering controls and PPE as reported or more stringently than reported. Since PPE use was slightly more prevalent than engineering controls, better communication may be necessary to reinforce the importance of the hierarchy of controls. These findings may also be useful in conducting exposure assessment and epidemiologic research among U.S. workers handling nanomaterials. Keywords
engineering controls, exposure, health, hierarchy of controls, nanotechnology, personal protective equipment (PPE)
Address correspondence to: Mary K. Schubauer-Berigan, Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, 1090 Tusculum Ave, Cincinnati, OH 45226; e-mail: [email protected]
INTRODUCTION
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anotechnology, the manipulation of matter at the 1–100 nm size range, has enormous potential to meet medical and technological needs, but there are concerns about potential occupational health hazards. These concerns are based on the growing number of animal toxicological studies indicating the potential for inflammatory response and oxidative stress, culminating in multifocal granulomatous pneumonia, interstitial fibrosis, and mutagenesis from inhalation of some engineered nanomaterials (ENM), including engineered carbonaceous nanomaterials (ECN) such as carbon nanotubes and nanofibers.(1–3) It is difficult to estimate how many workers are involved in the manufacture and use of ENM. One estimate has 400,000 workers worldwide in the field of nanotechnology, with an estimated 150,000 of those in the United States.(4) A more recent enumeration of the U.S. workforce handling ECN,(5) which includes carbon nanotubes, carbon nanofibers, graphene, and fullerene, counted fewer than 1000 workers above the research and development scale. While there is incomplete information about possible health risks of handling ENM in the workplace, the National Institute for Occupational Safety and Health (NIOSH) recommends that companies take precautionary measures to protect the health of their employees handling nanomaterials. Based on the hierarchy of controls, engineering and administrative controls are preferred to reduce possible exposures before requiring use of personal protective equipment (PPE). NIOSH has recently issued a detailed guidance document about the use of this approach for ENM,(6) but the general approach has been advocated for many years by NIOSH and others.(7–9) Despite the availability of such guidance, the extent to which the industry has adopted the recommendations of NIOSH and other organizations to minimize potential exposure to nanomaterials remains unclear.
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The purpose of the present study was to characterize current U.S. industry practices with respect to minimizing exposure to ENM. Specifically, our aims were to (1) determine the level of adoption of precautionary guidance on engineering controls and PPE among U.S. companies, and (2) evaluate the reliability of companies’ self-reported use of engineering controls and PPE. Because NIOSH has conducted a large number of exposure assessments at a wide variety of manufacturers and users of nanomaterials and has also conducted an industrywide survey of ECN users, the focus of this study was on data collected by NIOSH.
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METHODS Data Sources The sources of data used in this study included (1) a NIOSH telephone survey of all ECN manufacturers and users who could be identified as operating above research and development scale; and (2) field reports, notes, and data tables for all NIOSH surveys of ENM exposure conducted within a defined time frame, from 2006 through 2011. These data sources and their utility are described below. To assess the use of precautionary guidance among companies manufacturing or using ECN in the United States, NIOSH conducted an industrywide survey (by telephone) between October 2008 and May 2009 to identify types and quantities of ECN produced and factors related to workplace exposure reductions.(5,10) The initial telephone survey consisted of 30 respondents among 61 potential participants; five additional companies (four of which had not been initially surveyed) responded to the survey after the date of initial publication, for a total of 35 out of 65 (54%). Companies were asked to indicate which among a wide variety of administrative controls, engineering controls, and PPE types were being used at their facility (Table I). These approaches are among those recommended in a variety of NIOSH guidance documents for minimizing exposure to engineered nanomaterials. NIOSH also conducted field research between 2006 and 2011 in 46 facilities handling a variety of ENM, including 16 of the 35 companies handling ECN that participated in the telephone survey. The ENM evaluated in these field studies included carbon nanotubes (n = 26), carbon nanofibers (n = 12), other ECN such as fullerenes and graphene (n = 3), other nanofibers or nanowires (n = 2), metals or metal oxides (n = 10), nano-silica (n = 2), and quantum dots (n = 2). Some facilities handled several types of ENM. The NIOSH field evaluation reports and field notes were evaluated to assess the level of observed adoption of risk management guidance within the participating ENM companies. Since 16 of the ECN facilities participating in the NIOSH survey were also part of the 46 ENM field evaluations, this created the opportunity to assess the accuracy of self-reported engineering controls and PPE use. The field notes collected from each site visit did not describe the use of most administrative controls listed in Table I; therefore, the current study focused on engineering controls, some housekeeping methods, and use of PPE, as 70
identified by italics in Table I. The authors also classified the 46 facilities into one of three groups: (1) involved in primary manufacturing or purification of ENM; (2) a secondary manufacturer or user, incorporating ENM into other products; or (3) a hybrid facility involved in both the production and use of ENM. Data Analysis For the present study, three analyses were conducted. First, for data in the NIOSH industrywide survey of ECN manufacturers and users (n = 35), the authors estimated the percentage of companies that reported use of each type of italicized engineering control, housekeeping method, or PPE listed in Table I. This analysis is similar to that reported by Dahm et al.(10) but with information added for five companies that newly responded to the survey. Second, for the ENM companies visited by a NIOSH field team (n = 46), the authors estimated the percentage for whom each type of engineering control, housekeeping method, or PPE was observed to be in use and also evaluated whether there were differences in the adoption of these approaches by type of facility (primary manufacturer, user, or hybrid). Third, of the ECN companies participating in the industrywide survey which were also visited by a NIOSH field team (n = 16), the authors estimated the percentage for which the observed use of engineering controls or PPE was as reported or more stringent than reported. For each analysis type, 95% confidence intervals (CIs) were estimated for the calculated percentage of use of each type of engineering control or PPE (assuming it represents a binomial proportion), using the exact binomial distribution.(11) A normal approximation was used to test the difference between the proportions of each type of PPE used against those for each type of engineering control and housekeeping method. Fisher’s exact test was used to test whether the adoption of exposure minimization practices differed by facility type (primary manufacturer, user or hybrid). All analyses were conducted in SAS version 9.2 (SAS, Inc., Cary N.C.). RESULTS
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he most commonly reported engineering controls among surveyed ECN manufacturers or users were chemical hoods (83%) and local exhaust ventilation (71%) (Table II). A much smaller percentage reported use of more-contained production, such as ventilated enclosures or glove boxes (each at 40%), or completely enclosed (i.e., isolated) production processes (34%). As seen in Table II, 80% or more reported using each type of PPE (respirators, lab coats or Tyvek suits, gloves). Overall, 97% (95% CI: 85–100%) of ECN manufacturers and users reported using some form of PPE, and the same percentage reported using a hood or ventilated enclosure as forms of engineering control. In the analysis of 46 ENM manufacturers and users visited in NIOSH field evaluations, in all instances, the individual engineering control types and cleanup techniques
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TABLE I. Examples of Exposure Controls Used in NIOSH Industrywide Survey of Engineered Carbonaceous Nanomaterials Engineering and Administrative Exposure Controls
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Substitution: material or process Local exhaust ventilation = LEV A a. LEV ducted to the outside of the building b. LEV filtered and ducted back into the room with a HEPAB filter Non-HEPA filter Chemical fume hoods Biosafety cabinets = BSC a. BSC ducted to outside b. BSC HEPA filtered and exhausts into the room Ventilated enclosures a. Glove boxes b. Other (Describe)
Separate ventilation for office areas Isolated operations (enclosed production)
Restricted Access Sealed Operations Health and Safety Training Spill Control & Storage
Work Practice and Personal Protective Equipment Exposure Controls Wet methods for dust a. clean-up b. machining HEPA-filtered vacuums for clean-up Housekeeping program Equipment Maintenance Standard Operating Procedures Hand washing Food Prohibited in Process Areas
Personal Protective Clothing a. aprons b. Tyvek suits c. Work shoes/shoe covers d. Eye and Face Protection e. Respirators f. Gloves Coveralls/uniforms supplied/laundered at the worksite Change facilities Showers
AItalicized BHEPA:
items were included in the current analysis. high-efficiency particulate air
TABLE II. Reported Use of Engineering Controls and Personal Protective Equipment, among 65 U.S. Manufacturers and Users of Engineered Carbonaceous Nanomaterials (ECN) Surveyed in 2008–2011A N reporting usage 35A
Percentage (95% confidence interval)
Wet-wipe cleanup methods Use of HEPA vacuum for cleanup
22 18
63% (45%, 79%) 51% (34%, 69%)
Personal protective equipment
Lab coats/Tyvek suits Gloves Respirators
29 33 28
83% (70%, 95%) 94% (81%, 99%) 80% (63%, 92%)
Engineering controls
Local exhaust ventilation Chemical fume hoods Ventilated enclosures Glove boxes Enclosed production
25 29 14 14 12
71% (54%, 85%) 83% (70%, 95%) 40% (24%, 58%) 40% (24%, 58%) 34% (19%, 52%)
Type of exposure control
Total respondents
Housekeeping practices
AAmong
sites surveyed by NIOSH in 2008–2009 10 and supplemented through 2011 with additional information, as described in text.
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FIGURE 1. Frequency of observed use of engineering controls or PPE among 46 companies visited by a NIOSH field team. Stippled bars indicate engineering controls, clear bars indicate housekeeping methods, and hatched bars indicate PPE.
were observed to be adopted significantly less frequently than individual forms of PPE (Figure 1). The most frequently adopted engineering control was local exhaust ventilation (59%). Approximately half of companies adopted chemical hoods, ventilated enclosures, or enclosed production (i.e., isolated operations). Only 22% reported using glove boxes. Despite the low percentages of adoption for individual engineering controls, most ENM companies were using one or more forms of containment: 85% (95% CI: 72%, 94%) of the surveyed companies were observed to be using some form of containment-based engineering control, such as a chemical hood or other enclosure. A smaller percentage, 74% (95% CI: 59%, 86%) used an enclosure-based form of containment. By contrast, 89% (95% CI: 76%, 96%) were observed to be using some form of PPE. Gloves were the most widely adopted form of PPE (89%), with slightly but non-significantly lower percentages reporting use of respirators and lab coats or Tyvek-style suits. Respirator types observed to be used by the ENM companies varied widely: 23% used filtering facepiece respirators (with N95, N100, or P100 filters), 40% used half-face negative pressure respirators, 13% used full-face negative pressure respirators, 2% used powered air-purifying respirators, and 21% used multiple respirator types. Fewer than 40% of ENM companies were observed to be using recommended housekeeping methods, such as wet wiping and use of HEPA-filtered vacuums. These percentages were significantly lower than for use of any form of PPE or for use of a containment system type of engineering control (p < 0.0002). Half of the 46 ENM facilities visited were users of ENM (e.g., facilities that incorporate ENM into other materials), 72
one-third were primary manufacturers, and the rest were hybrid (i.e., both produced and used ENM). There were no significant differences by facility type in adoption of containment-based engineering control, use of LEV, housekeeping practices, or use of gloves or lab coats/Tyvek suits (Table III). However, ENM users were somewhat less likely than primary manufacturers or hybrid facilities to wear respirators (p = 0.06) and to use containment-based controls other than a chemical fume hood (p = 0.08). In the analysis of ECN companies that were surveyed and then subsequently visited by a NIOSH team, nearly all companies were observed to be using engineering controls and PPE as reported or more stringently than reported (Table IV). More than 90% of the ECN companies used each PPE type, wet-wipe cleanup methods, and HEPA vacuums, as reported in the survey or better. At least 75% (95% CI: 48%, 93%) were using each type of engineering control as reported in the survey or better.
DISCUSSION
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he previous NIOSH survey of companies handling ECN found that 70% reported having a health and safety program for the use of nanomaterials.(10) The present study augmented that survey with information from five additional companies, and the reported use of engineering controls, good housekeeping practices, and use of PPE was very similar to that reported previously. On-site evaluation confirmed that self-reporting was reliable, as more than 90% of the ECN companies who responded to the survey were using
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TABLE III. Observed Frequency of Use of Any Form of Containment-Based Engineering Control, of Cleaning Best Practices, and of Different Forms of Personal Protective Equipment, by Facility Type Type of exposure control method
Primary manufacturerA (n = 15)
Hybrid (n = 8)
User (n = 23)
p (for difference among facility types)
Local exhaust ventilation ContainmentB Hood only Other enclosure Wet wiping methods HEPA vacuum Gloves Lab coats/Tyvek suits Respirators
67%(38%, 88%) 87%(60%, 98%) 6.7%(0.2%, 32%) 80%(52%, 96%) 40%(16%, 68%) 27%(7.8%, 55%) 100%(78%, 100%) 80%(52%, 96%) 93%(68%, 100%)
50%(16%, 84%) 100%(63%, 100%) 0%(0%, 37%) 100%(63%, 100%) 25%(3.2%, 65%) 25%(3.2%, 65%) 100%(63%, 100%) 100%(63%, 100%) 88%(47%, 100%)
57%(34%, 77%) 78%(56%, 93%) 17%(5.0%, 39%) 61%(39%, 80%) 39%(20%, 61%) 35%(16%, 57%) 78%(56%, 93%) 78%(56%, 93%) 61%(41%, 81%)
0.7830 0.4231 0.5543 0.0800 0.8429 0.9141 0.0976 0.5078 0.0610
AIncludes
facilities that only purify nanomaterials fume hood, ventilated enclosure, glove box, and/or enclosed production
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BChemical
engineering controls and PPE as reported or more stringently than reported. In our assessment of ENM manufacturers and users, of the 46 companies visited for a NIOSH field evaluation, PPE use was observed slightly more frequently than containmentbased engineering controls (hoods or enclosures). Until further information on the possible health risks and extent of occupational exposure to nanomaterials becomes available, interim protective measures should be developed and implemented. NIOSH recommends a hierarchy of controls (hazard elimination, chemical substitution, engineering controls, administrative controls, and PPE), to reduce the potential exposure to hazardous materials where possible, or if that is not feasible, to control the hazard as close to the source as possible.
Engineering control techniques (e.g., source enclosure, chemical hoods, and local exhaust ventilation) in conjunction with administrative controls (e.g., good work practices and training) are preferred over the use of PPE to protect workers. For PPE to be effective, employees must understand the proper selection, use, and limitations of PPE and wear it properly at all times when there is the potential for exposure; this places the burden on the employee instead of reducing potential exposures with engineering and administrative controls. NIOSH has been promoting this advice since 2005 when the draft document, Approaches to Safe Nanotechnology: An Information Exchange with NIOSH was released; this document has since been updated and published in 2009 as Approaches to Safe Nanotechnology: Managing the Health and Safety Concerns with Engineered Nanomaterials.(7) Comprehensive guidance
TABLE IV. Observed Concordance of Engineering Controls and Personal Protective Equipment among U.S. Manufacturers and Users of Engineered Carbonaceous Nanomaterials (ECN) Concordance of field observations with survey reports Observed exactly as reported
Total N Wet-wipe cleanup methods Use of HEPA vacuum for cleanup Lab coats/Tyvek suits Gloves Respirators Local exhaust ventilation Chemical fume hoods Ventilated enclosures Glove boxes Enclosed production ANumber
Observed as reported or better
N
95% CI
N
95% CI
16A 11 15 14 15 13 14 12 12 13 10
69%(41%, 89%) 94%(70%, 100%) 88%(62%, 98%) 94%(70%, 100%) 81%(54%, 96%) 88%(62%, 98%) 75%(48%, 93%) 75%(48%, 93%) 81%(54%, 96%) 63%(35%, 85%)
16 15 15 15 16 16 14 12 14 14 14
94%(70%, 100%) 94%(70%, 100%) 94%(70%, 100%) 100%(79%, 100%) 100%(79%, 100%) 88%(62%, 98%) 75%(48%, 93%) 88%(62%, 98%) 88%(62%, 98%) 88%(62%, 98%)
visited by a NIOSH team, among 35 ECN survey respondents.
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on engineering controls for nanomaterials was published very recently as Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes.(6) The majority of U.S. facilities evaluated by NIOSH were aware of the need for engineering controls and PPE. However, further communication with companies by trade associations, unions, insurance companies, and government agencies may be needed on the hierarchy of controls to amplify existing precautionary messages, since PPE was noted to be slightly more prevalent than the use of engineering and administrative controls and much more prevalent than use of best housekeeping practices. Currently, few studies have investigated the effectiveness of engineering controls commonly used to reduce workplace exposures to nanoparticles.(12) In the present study, the authors observed that users of ENM were somewhat less likely than primary or hybrid manufacturers to use containment-based engineering controls other than a chemical fume hood (61% compared to 80% and 100%, respectively). NIOSH field teams have noted that chemical hoods were not always in operation during handling of nanomaterials (e.g., the operator turned them off so that the product was not drawn up with the exhaust), and that most ventilated enclosures operated at low flow rates for similar reasons.(12,13) NIOSH studies have also noted that potential exposures occurred from open, uncontained, or unventilated procedures (e.g., sonication), which may be more common among users of ENM. These findings could indicate a need to specifically target ENM users for enhanced communication about effective use of engineering controls. To minimize exposure risks, much more information is needed concerning the effectiveness of controls under various workplace conditions and scenarios. The evidence is building for the need to control exposures and to convince employers to invest in appropriate risk management practices. Others have found similar need for amplified precautionary messages. A University of California survey (with 58% of the sample coming from U.S. companies) reported that companies had a high level of uncertainty about the hazards posed by nanomaterials.(14) A majority of companies indicated “lack of information” as an impediment to implementing nano-specific safety practices. Safety data sheets (SDSs) are considered a primary information resource in communicating the hazards of chemicals. NIOSH researchers evaluated 44 nanomaterial SDSs in 2011. The majority (67%) of the SDSs provided insufficient data for accurately communicating the potential hazards of engineered nanomaterials, as toxicologic data were missing or the SDS included recommended exposure limits for the macro-sized material without noting that this occupational exposure limit may not be protective for the nanoscale material.(15) The findings in this study are subject to the limitations of the sample set evaluated. ECN manufacturers and users are over-represented (at 65%) among the 46 sites visited by a NIOSH team, while survey-based estimates have indicated that only about one-third of all ENM facilities are handling ECN.(16) ECN-handling facilities, dominated by producers and 74
users of carbon nanotubes and nanofibers, may have higher awareness of the need to take precautionary measures to reduce workplace exposure because of the large body of evidence regarding hazard from toxicological studies. Another limitation is that the ECN manufacturers and users in our telephone survey data set were comprised of voluntary respondents to a request for information and may not be representative of the entire population of 65 companies identified. Furthermore, the 16 ECN companies that permitted NIOSH to visit for a field study may not be representative of all respondents, and it is possible that they represent the companies most likely to be adherent to recommended exposure control methods. The wider data set of 30 facilities working with other forms of ENM which were visited by a NIOSH field team represents a convenience sample among a population of unknown size, as the underlying number of potentially eligible facilities was not enumerated. In its current strategic plan, NIOSH has prioritized the development and implementation of a survey to more broadly identify and question a representative sample of ENM manufacturers and users, including enhanced outreach to facilities that do not adhere to recommended best practices to minimize workplace exposure,(17) but such a survey will have some of the same limitations as the previous survey of ECN manufacturers (e.g., reliance on voluntary response). CONCLUSION
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he authors found that a reasonably high percentage of the U.S. nanomaterial companies included in this study are adhering to some precautionary guidance. Substantial differences were not observed in the adoption of guidance among the facilities that use ENM compared to those that manufacture ENM. However, given the limitations enumerated above, the true level of adoption of guidance is not known among all U.S. ENM facilities. While there was a high degree of corroboration of survey results by direct observation reported here, further evaluation is needed to assess the finding that self-reporting by companies can be used as a reliable indicator of adherence with recommendations and the effectiveness of their implementation. RECOMMENDATIONS
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otentially hazardous exposures to engineered nanomaterials and potential subsequent illnesses can be minimized through safe work practices and effective communication. Facilities that handle engineered nanomaterials should be reminded to 1) follow the hierarchy of controls, and 2) to update their SDSs (if applicable) to include current relevant toxicologic data and workplace control guidance. ACKNOWLEDGMENTS
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he authors are grateful to the facilities that responded to the survey and those that permitted NIOSH field teams
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to conduct site visits. The authors also thank the NIOSH investigators and contractors who participated in conducting those visits, including Catherine Beaucham, Eileen Birch, Carlos Crawford, Brian Curwin, Douglas Evans, Greg Kinnes, Kenneth Martinez, Mark Methner, and Christopher Sparks. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the NIOSH. This article is not subject to US copyright law.
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FUNDING
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his study was funded by the NIOSH Nanotechnology Research Center and by the National Institute of Environmental Health Sciences (Interagency Agreement numbers AES12029-001-00000, AES12011-001-00001, and Y1ES9026-04).
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Characterizing Adoption of Precautionary Risk Management Guidance for Nanomaterials, an Emerging Occupational Hazard a
a
b
b
Mary K. Schubauer-Berigan , Matthew M. Dahm , Paul A. Schulte , Laura Hodson & Charles L. Geraci
b
a
Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio b
Education and Information Division, National Institute for Occupational Safety and Health, Cincinnati, Ohio Accepted author version posted online: 05 Aug 2014.Published online: 20 Nov 2014.
Click for updates To cite this article: Mary K. Schubauer-Berigan, Matthew M. Dahm, Paul A. Schulte, Laura Hodson & Charles L. Geraci (2015) Characterizing Adoption of Precautionary Risk Management Guidance for Nanomaterials, an Emerging Occupational Hazard, Journal of Occupational and Environmental Hygiene, 12:1, 69-75, DOI: 10.1080/15459624.2014.946515 To link to this article: http://dx.doi.org/10.1080/15459624.2014.946515
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Journal of Occupational and Environmental Hygiene, 12: 69–75 ISSN: 1545-9624 print / 1545-9632 online DOI: 10.1080/15459624.2014.946515
Characterizing Adoption of Precautionary Risk Management Guidance for Nanomaterials, an Emerging Occupational Hazard Mary K. Schubauer-Berigan,1Matthew M. Dahm,1 Paul A. Schulte,2 Laura Hodson,2 and Charles L. Geraci2 1
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Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio 2 Education and Information Division, National Institute for Occupational Safety and Health, Cincinnati, Ohio
Exposure to engineered nanomaterials (substances with at least one dimension of 1–100 nm) has been of increased interest, with the recent growth in production and use of nanomaterials worldwide. Various organizations have recommended methods to minimize exposure to engineered nanomaterials. The purpose of this study was to evaluate available data to examine the extent to which studied U.S. companies (which represent a small fraction of all companies using certain forms of engineered nanomaterials) follow the guidelines for reducing occupational exposures to engineered nanomaterials that have been issued by the National Institute for Occupational Safety and Health (NIOSH) and other organizations. Survey data, field reports, and field notes for all NIOSH nanomaterial exposure assessments conducted between 2006 and 2011 were collected and reviewed to: (1) determine the level of adoption of precautionary guidance on engineering controls and personal protective equipment (PPE), and (2) evaluate the reliability of companies’ self-reported use of engineering controls and PPE. Use of PPE was observed among 89% [95% confidence interval (CI): 76%–96%] of 46 visited companies, and use of containment-based engineering controls for at least some processes was observed among 83% (95% CI: 76%–96%). In on-site evaluations, more than 90% of the 16 engineered carbonaceous nanomaterial companies that responded to an industrywide survey were observed to be using engineering controls and PPE as reported or more stringently than reported. Since PPE use was slightly more prevalent than engineering controls, better communication may be necessary to reinforce the importance of the hierarchy of controls. These findings may also be useful in conducting exposure assessment and epidemiologic research among U.S. workers handling nanomaterials. Keywords
engineering controls, exposure, health, hierarchy of controls, nanotechnology, personal protective equipment (PPE)
Address correspondence to: Mary K. Schubauer-Berigan, Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, 1090 Tusculum Ave, Cincinnati, OH 45226; e-mail: [email protected]
INTRODUCTION
N
anotechnology, the manipulation of matter at the 1–100 nm size range, has enormous potential to meet medical and technological needs, but there are concerns about potential occupational health hazards. These concerns are based on the growing number of animal toxicological studies indicating the potential for inflammatory response and oxidative stress, culminating in multifocal granulomatous pneumonia, interstitial fibrosis, and mutagenesis from inhalation of some engineered nanomaterials (ENM), including engineered carbonaceous nanomaterials (ECN) such as carbon nanotubes and nanofibers.(1–3) It is difficult to estimate how many workers are involved in the manufacture and use of ENM. One estimate has 400,000 workers worldwide in the field of nanotechnology, with an estimated 150,000 of those in the United States.(4) A more recent enumeration of the U.S. workforce handling ECN,(5) which includes carbon nanotubes, carbon nanofibers, graphene, and fullerene, counted fewer than 1000 workers above the research and development scale. While there is incomplete information about possible health risks of handling ENM in the workplace, the National Institute for Occupational Safety and Health (NIOSH) recommends that companies take precautionary measures to protect the health of their employees handling nanomaterials. Based on the hierarchy of controls, engineering and administrative controls are preferred to reduce possible exposures before requiring use of personal protective equipment (PPE). NIOSH has recently issued a detailed guidance document about the use of this approach for ENM,(6) but the general approach has been advocated for many years by NIOSH and others.(7–9) Despite the availability of such guidance, the extent to which the industry has adopted the recommendations of NIOSH and other organizations to minimize potential exposure to nanomaterials remains unclear.
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The purpose of the present study was to characterize current U.S. industry practices with respect to minimizing exposure to ENM. Specifically, our aims were to (1) determine the level of adoption of precautionary guidance on engineering controls and PPE among U.S. companies, and (2) evaluate the reliability of companies’ self-reported use of engineering controls and PPE. Because NIOSH has conducted a large number of exposure assessments at a wide variety of manufacturers and users of nanomaterials and has also conducted an industrywide survey of ECN users, the focus of this study was on data collected by NIOSH.
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METHODS Data Sources The sources of data used in this study included (1) a NIOSH telephone survey of all ECN manufacturers and users who could be identified as operating above research and development scale; and (2) field reports, notes, and data tables for all NIOSH surveys of ENM exposure conducted within a defined time frame, from 2006 through 2011. These data sources and their utility are described below. To assess the use of precautionary guidance among companies manufacturing or using ECN in the United States, NIOSH conducted an industrywide survey (by telephone) between October 2008 and May 2009 to identify types and quantities of ECN produced and factors related to workplace exposure reductions.(5,10) The initial telephone survey consisted of 30 respondents among 61 potential participants; five additional companies (four of which had not been initially surveyed) responded to the survey after the date of initial publication, for a total of 35 out of 65 (54%). Companies were asked to indicate which among a wide variety of administrative controls, engineering controls, and PPE types were being used at their facility (Table I). These approaches are among those recommended in a variety of NIOSH guidance documents for minimizing exposure to engineered nanomaterials. NIOSH also conducted field research between 2006 and 2011 in 46 facilities handling a variety of ENM, including 16 of the 35 companies handling ECN that participated in the telephone survey. The ENM evaluated in these field studies included carbon nanotubes (n = 26), carbon nanofibers (n = 12), other ECN such as fullerenes and graphene (n = 3), other nanofibers or nanowires (n = 2), metals or metal oxides (n = 10), nano-silica (n = 2), and quantum dots (n = 2). Some facilities handled several types of ENM. The NIOSH field evaluation reports and field notes were evaluated to assess the level of observed adoption of risk management guidance within the participating ENM companies. Since 16 of the ECN facilities participating in the NIOSH survey were also part of the 46 ENM field evaluations, this created the opportunity to assess the accuracy of self-reported engineering controls and PPE use. The field notes collected from each site visit did not describe the use of most administrative controls listed in Table I; therefore, the current study focused on engineering controls, some housekeeping methods, and use of PPE, as 70
identified by italics in Table I. The authors also classified the 46 facilities into one of three groups: (1) involved in primary manufacturing or purification of ENM; (2) a secondary manufacturer or user, incorporating ENM into other products; or (3) a hybrid facility involved in both the production and use of ENM. Data Analysis For the present study, three analyses were conducted. First, for data in the NIOSH industrywide survey of ECN manufacturers and users (n = 35), the authors estimated the percentage of companies that reported use of each type of italicized engineering control, housekeeping method, or PPE listed in Table I. This analysis is similar to that reported by Dahm et al.(10) but with information added for five companies that newly responded to the survey. Second, for the ENM companies visited by a NIOSH field team (n = 46), the authors estimated the percentage for whom each type of engineering control, housekeeping method, or PPE was observed to be in use and also evaluated whether there were differences in the adoption of these approaches by type of facility (primary manufacturer, user, or hybrid). Third, of the ECN companies participating in the industrywide survey which were also visited by a NIOSH field team (n = 16), the authors estimated the percentage for which the observed use of engineering controls or PPE was as reported or more stringent than reported. For each analysis type, 95% confidence intervals (CIs) were estimated for the calculated percentage of use of each type of engineering control or PPE (assuming it represents a binomial proportion), using the exact binomial distribution.(11) A normal approximation was used to test the difference between the proportions of each type of PPE used against those for each type of engineering control and housekeeping method. Fisher’s exact test was used to test whether the adoption of exposure minimization practices differed by facility type (primary manufacturer, user or hybrid). All analyses were conducted in SAS version 9.2 (SAS, Inc., Cary N.C.). RESULTS
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he most commonly reported engineering controls among surveyed ECN manufacturers or users were chemical hoods (83%) and local exhaust ventilation (71%) (Table II). A much smaller percentage reported use of more-contained production, such as ventilated enclosures or glove boxes (each at 40%), or completely enclosed (i.e., isolated) production processes (34%). As seen in Table II, 80% or more reported using each type of PPE (respirators, lab coats or Tyvek suits, gloves). Overall, 97% (95% CI: 85–100%) of ECN manufacturers and users reported using some form of PPE, and the same percentage reported using a hood or ventilated enclosure as forms of engineering control. In the analysis of 46 ENM manufacturers and users visited in NIOSH field evaluations, in all instances, the individual engineering control types and cleanup techniques
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TABLE I. Examples of Exposure Controls Used in NIOSH Industrywide Survey of Engineered Carbonaceous Nanomaterials Engineering and Administrative Exposure Controls
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Substitution: material or process Local exhaust ventilation = LEV A a. LEV ducted to the outside of the building b. LEV filtered and ducted back into the room with a HEPAB filter Non-HEPA filter Chemical fume hoods Biosafety cabinets = BSC a. BSC ducted to outside b. BSC HEPA filtered and exhausts into the room Ventilated enclosures a. Glove boxes b. Other (Describe)
Separate ventilation for office areas Isolated operations (enclosed production)
Restricted Access Sealed Operations Health and Safety Training Spill Control & Storage
Work Practice and Personal Protective Equipment Exposure Controls Wet methods for dust a. clean-up b. machining HEPA-filtered vacuums for clean-up Housekeeping program Equipment Maintenance Standard Operating Procedures Hand washing Food Prohibited in Process Areas
Personal Protective Clothing a. aprons b. Tyvek suits c. Work shoes/shoe covers d. Eye and Face Protection e. Respirators f. Gloves Coveralls/uniforms supplied/laundered at the worksite Change facilities Showers
AItalicized BHEPA:
items were included in the current analysis. high-efficiency particulate air
TABLE II. Reported Use of Engineering Controls and Personal Protective Equipment, among 65 U.S. Manufacturers and Users of Engineered Carbonaceous Nanomaterials (ECN) Surveyed in 2008–2011A N reporting usage 35A
Percentage (95% confidence interval)
Wet-wipe cleanup methods Use of HEPA vacuum for cleanup
22 18
63% (45%, 79%) 51% (34%, 69%)
Personal protective equipment
Lab coats/Tyvek suits Gloves Respirators
29 33 28
83% (70%, 95%) 94% (81%, 99%) 80% (63%, 92%)
Engineering controls
Local exhaust ventilation Chemical fume hoods Ventilated enclosures Glove boxes Enclosed production
25 29 14 14 12
71% (54%, 85%) 83% (70%, 95%) 40% (24%, 58%) 40% (24%, 58%) 34% (19%, 52%)
Type of exposure control
Total respondents
Housekeeping practices
AAmong
sites surveyed by NIOSH in 2008–2009 10 and supplemented through 2011 with additional information, as described in text.
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FIGURE 1. Frequency of observed use of engineering controls or PPE among 46 companies visited by a NIOSH field team. Stippled bars indicate engineering controls, clear bars indicate housekeeping methods, and hatched bars indicate PPE.
were observed to be adopted significantly less frequently than individual forms of PPE (Figure 1). The most frequently adopted engineering control was local exhaust ventilation (59%). Approximately half of companies adopted chemical hoods, ventilated enclosures, or enclosed production (i.e., isolated operations). Only 22% reported using glove boxes. Despite the low percentages of adoption for individual engineering controls, most ENM companies were using one or more forms of containment: 85% (95% CI: 72%, 94%) of the surveyed companies were observed to be using some form of containment-based engineering control, such as a chemical hood or other enclosure. A smaller percentage, 74% (95% CI: 59%, 86%) used an enclosure-based form of containment. By contrast, 89% (95% CI: 76%, 96%) were observed to be using some form of PPE. Gloves were the most widely adopted form of PPE (89%), with slightly but non-significantly lower percentages reporting use of respirators and lab coats or Tyvek-style suits. Respirator types observed to be used by the ENM companies varied widely: 23% used filtering facepiece respirators (with N95, N100, or P100 filters), 40% used half-face negative pressure respirators, 13% used full-face negative pressure respirators, 2% used powered air-purifying respirators, and 21% used multiple respirator types. Fewer than 40% of ENM companies were observed to be using recommended housekeeping methods, such as wet wiping and use of HEPA-filtered vacuums. These percentages were significantly lower than for use of any form of PPE or for use of a containment system type of engineering control (p < 0.0002). Half of the 46 ENM facilities visited were users of ENM (e.g., facilities that incorporate ENM into other materials), 72
one-third were primary manufacturers, and the rest were hybrid (i.e., both produced and used ENM). There were no significant differences by facility type in adoption of containment-based engineering control, use of LEV, housekeeping practices, or use of gloves or lab coats/Tyvek suits (Table III). However, ENM users were somewhat less likely than primary manufacturers or hybrid facilities to wear respirators (p = 0.06) and to use containment-based controls other than a chemical fume hood (p = 0.08). In the analysis of ECN companies that were surveyed and then subsequently visited by a NIOSH team, nearly all companies were observed to be using engineering controls and PPE as reported or more stringently than reported (Table IV). More than 90% of the ECN companies used each PPE type, wet-wipe cleanup methods, and HEPA vacuums, as reported in the survey or better. At least 75% (95% CI: 48%, 93%) were using each type of engineering control as reported in the survey or better.
DISCUSSION
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he previous NIOSH survey of companies handling ECN found that 70% reported having a health and safety program for the use of nanomaterials.(10) The present study augmented that survey with information from five additional companies, and the reported use of engineering controls, good housekeeping practices, and use of PPE was very similar to that reported previously. On-site evaluation confirmed that self-reporting was reliable, as more than 90% of the ECN companies who responded to the survey were using
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TABLE III. Observed Frequency of Use of Any Form of Containment-Based Engineering Control, of Cleaning Best Practices, and of Different Forms of Personal Protective Equipment, by Facility Type Type of exposure control method
Primary manufacturerA (n = 15)
Hybrid (n = 8)
User (n = 23)
p (for difference among facility types)
Local exhaust ventilation ContainmentB Hood only Other enclosure Wet wiping methods HEPA vacuum Gloves Lab coats/Tyvek suits Respirators
67%(38%, 88%) 87%(60%, 98%) 6.7%(0.2%, 32%) 80%(52%, 96%) 40%(16%, 68%) 27%(7.8%, 55%) 100%(78%, 100%) 80%(52%, 96%) 93%(68%, 100%)
50%(16%, 84%) 100%(63%, 100%) 0%(0%, 37%) 100%(63%, 100%) 25%(3.2%, 65%) 25%(3.2%, 65%) 100%(63%, 100%) 100%(63%, 100%) 88%(47%, 100%)
57%(34%, 77%) 78%(56%, 93%) 17%(5.0%, 39%) 61%(39%, 80%) 39%(20%, 61%) 35%(16%, 57%) 78%(56%, 93%) 78%(56%, 93%) 61%(41%, 81%)
0.7830 0.4231 0.5543 0.0800 0.8429 0.9141 0.0976 0.5078 0.0610
AIncludes
facilities that only purify nanomaterials fume hood, ventilated enclosure, glove box, and/or enclosed production
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BChemical
engineering controls and PPE as reported or more stringently than reported. In our assessment of ENM manufacturers and users, of the 46 companies visited for a NIOSH field evaluation, PPE use was observed slightly more frequently than containmentbased engineering controls (hoods or enclosures). Until further information on the possible health risks and extent of occupational exposure to nanomaterials becomes available, interim protective measures should be developed and implemented. NIOSH recommends a hierarchy of controls (hazard elimination, chemical substitution, engineering controls, administrative controls, and PPE), to reduce the potential exposure to hazardous materials where possible, or if that is not feasible, to control the hazard as close to the source as possible.
Engineering control techniques (e.g., source enclosure, chemical hoods, and local exhaust ventilation) in conjunction with administrative controls (e.g., good work practices and training) are preferred over the use of PPE to protect workers. For PPE to be effective, employees must understand the proper selection, use, and limitations of PPE and wear it properly at all times when there is the potential for exposure; this places the burden on the employee instead of reducing potential exposures with engineering and administrative controls. NIOSH has been promoting this advice since 2005 when the draft document, Approaches to Safe Nanotechnology: An Information Exchange with NIOSH was released; this document has since been updated and published in 2009 as Approaches to Safe Nanotechnology: Managing the Health and Safety Concerns with Engineered Nanomaterials.(7) Comprehensive guidance
TABLE IV. Observed Concordance of Engineering Controls and Personal Protective Equipment among U.S. Manufacturers and Users of Engineered Carbonaceous Nanomaterials (ECN) Concordance of field observations with survey reports Observed exactly as reported
Total N Wet-wipe cleanup methods Use of HEPA vacuum for cleanup Lab coats/Tyvek suits Gloves Respirators Local exhaust ventilation Chemical fume hoods Ventilated enclosures Glove boxes Enclosed production ANumber
Observed as reported or better
N
95% CI
N
95% CI
16A 11 15 14 15 13 14 12 12 13 10
69%(41%, 89%) 94%(70%, 100%) 88%(62%, 98%) 94%(70%, 100%) 81%(54%, 96%) 88%(62%, 98%) 75%(48%, 93%) 75%(48%, 93%) 81%(54%, 96%) 63%(35%, 85%)
16 15 15 15 16 16 14 12 14 14 14
94%(70%, 100%) 94%(70%, 100%) 94%(70%, 100%) 100%(79%, 100%) 100%(79%, 100%) 88%(62%, 98%) 75%(48%, 93%) 88%(62%, 98%) 88%(62%, 98%) 88%(62%, 98%)
visited by a NIOSH team, among 35 ECN survey respondents.
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on engineering controls for nanomaterials was published very recently as Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes.(6) The majority of U.S. facilities evaluated by NIOSH were aware of the need for engineering controls and PPE. However, further communication with companies by trade associations, unions, insurance companies, and government agencies may be needed on the hierarchy of controls to amplify existing precautionary messages, since PPE was noted to be slightly more prevalent than the use of engineering and administrative controls and much more prevalent than use of best housekeeping practices. Currently, few studies have investigated the effectiveness of engineering controls commonly used to reduce workplace exposures to nanoparticles.(12) In the present study, the authors observed that users of ENM were somewhat less likely than primary or hybrid manufacturers to use containment-based engineering controls other than a chemical fume hood (61% compared to 80% and 100%, respectively). NIOSH field teams have noted that chemical hoods were not always in operation during handling of nanomaterials (e.g., the operator turned them off so that the product was not drawn up with the exhaust), and that most ventilated enclosures operated at low flow rates for similar reasons.(12,13) NIOSH studies have also noted that potential exposures occurred from open, uncontained, or unventilated procedures (e.g., sonication), which may be more common among users of ENM. These findings could indicate a need to specifically target ENM users for enhanced communication about effective use of engineering controls. To minimize exposure risks, much more information is needed concerning the effectiveness of controls under various workplace conditions and scenarios. The evidence is building for the need to control exposures and to convince employers to invest in appropriate risk management practices. Others have found similar need for amplified precautionary messages. A University of California survey (with 58% of the sample coming from U.S. companies) reported that companies had a high level of uncertainty about the hazards posed by nanomaterials.(14) A majority of companies indicated “lack of information” as an impediment to implementing nano-specific safety practices. Safety data sheets (SDSs) are considered a primary information resource in communicating the hazards of chemicals. NIOSH researchers evaluated 44 nanomaterial SDSs in 2011. The majority (67%) of the SDSs provided insufficient data for accurately communicating the potential hazards of engineered nanomaterials, as toxicologic data were missing or the SDS included recommended exposure limits for the macro-sized material without noting that this occupational exposure limit may not be protective for the nanoscale material.(15) The findings in this study are subject to the limitations of the sample set evaluated. ECN manufacturers and users are over-represented (at 65%) among the 46 sites visited by a NIOSH team, while survey-based estimates have indicated that only about one-third of all ENM facilities are handling ECN.(16) ECN-handling facilities, dominated by producers and 74
users of carbon nanotubes and nanofibers, may have higher awareness of the need to take precautionary measures to reduce workplace exposure because of the large body of evidence regarding hazard from toxicological studies. Another limitation is that the ECN manufacturers and users in our telephone survey data set were comprised of voluntary respondents to a request for information and may not be representative of the entire population of 65 companies identified. Furthermore, the 16 ECN companies that permitted NIOSH to visit for a field study may not be representative of all respondents, and it is possible that they represent the companies most likely to be adherent to recommended exposure control methods. The wider data set of 30 facilities working with other forms of ENM which were visited by a NIOSH field team represents a convenience sample among a population of unknown size, as the underlying number of potentially eligible facilities was not enumerated. In its current strategic plan, NIOSH has prioritized the development and implementation of a survey to more broadly identify and question a representative sample of ENM manufacturers and users, including enhanced outreach to facilities that do not adhere to recommended best practices to minimize workplace exposure,(17) but such a survey will have some of the same limitations as the previous survey of ECN manufacturers (e.g., reliance on voluntary response). CONCLUSION
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he authors found that a reasonably high percentage of the U.S. nanomaterial companies included in this study are adhering to some precautionary guidance. Substantial differences were not observed in the adoption of guidance among the facilities that use ENM compared to those that manufacture ENM. However, given the limitations enumerated above, the true level of adoption of guidance is not known among all U.S. ENM facilities. While there was a high degree of corroboration of survey results by direct observation reported here, further evaluation is needed to assess the finding that self-reporting by companies can be used as a reliable indicator of adherence with recommendations and the effectiveness of their implementation. RECOMMENDATIONS
P
otentially hazardous exposures to engineered nanomaterials and potential subsequent illnesses can be minimized through safe work practices and effective communication. Facilities that handle engineered nanomaterials should be reminded to 1) follow the hierarchy of controls, and 2) to update their SDSs (if applicable) to include current relevant toxicologic data and workplace control guidance. ACKNOWLEDGMENTS
T
he authors are grateful to the facilities that responded to the survey and those that permitted NIOSH field teams
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to conduct site visits. The authors also thank the NIOSH investigators and contractors who participated in conducting those visits, including Catherine Beaucham, Eileen Birch, Carlos Crawford, Brian Curwin, Douglas Evans, Greg Kinnes, Kenneth Martinez, Mark Methner, and Christopher Sparks. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the NIOSH. This article is not subject to US copyright law.
7.
8.
9.
FUNDING
T
his study was funded by the NIOSH Nanotechnology Research Center and by the National Institute of Environmental Health Sciences (Interagency Agreement numbers AES12029-001-00000, AES12011-001-00001, and Y1ES9026-04).
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11.
12.
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