Nanomaterials in
By Gavin H. West, Bruce Lippy, Danie​l Marsick, and Michael R. Cooper​​
All emerging technologies pose a similar dilemma for industrial hygienists. While the benefits of a new material, product, or process are often immediately apparent, assessing risks takes time. Typically, by the time IHs have the information they need to determine hazards and recommend controls, a new technology is already well established. Such is the case with nanotechnology, which is prevalent in many industries and is now beginning to transform construction. Remarkable modifications to traditional construction materials can be achieved by adding engineered nanoparticles (ENPs) or altering the materials’ nanostructure. These changes, which are discussed in the digital version of this issue, may lead to improved resource conservation, energy efficiency, and biodegradability—but they also introduce unknown occupational risks. RISKS OF NANOMATERIALS Construction workers and industrial hygienists should assume that the risks posed by nano-objects—a broad term covering nanoparticles, nanofibers, and nanoplates—are greater than those of the bulk material. The increased surface area of nanoparticles allows for greater bioreactivity, and decreased size influences mobility in living systems. A study published in the August 2009 Journal of Nanoparticles and Nanotechnology found that certain nanoparticles have been shown to cross the blood-brain barrier. Due to the large and expanding number of nanomaterials, researchers are trying to understand particle characteristics that influence health effects—an area of research that may lend itself to broad-based occupational exposure limits.

NIOSH has issued recommended exposure limits (RELs) for carbon nanotubes (CNTs) and ultrafine titanium dioxide (TiO2). NIOSH and the International Agency for Research on Cancer (IARC) consider nanoscale TiO2 a potential inhalation occupational carcinogen, and studies published in 2008 in the Journal of Toxicological Sciences and Nature Nanotechnology have linked CNTs to asbestos-like pathogenicity in mice, including mesothelioma. More recently, a 2014 long-term study in the American Journal of Physiology — Lung Cellular and Molecular Physiology showed that CNTs and asbestos fibers were both present one year post-exposure and were associated with adverse health effects in mice. Pathogenicity is believed to be related to chronic inflammatory processes for tubular fibers, such as CNTs, and bio-persistent low-toxicity dusts, such as nano TiO2. In the absence of other published approaches, the British Standards Institute suggested in 2007 that the NIOSH REL for TiO2 may be a reasonable basis to judge other insoluble nanoparticles.
Nanoparticles can be engineered to be safer by design—for example, capping CNTs with a C60 fullerene (also known as a “bucky-ball”) can prevent them from penetrating the pleura. A 2006 article in Science identifies nano-objects’ shape, chemical composition, solubility, surface charge, degree of aggregation, and surface structure as examples of factors related to toxic potential, which are important to consider in risk assessment and material design.
Despite cause for concern, the human health effects of ENP exposure remain largely unknown. Because epidemiological data are lacking, current risk assessment approaches rely heavily upon laboratory research. Risk of explosion and fire from nanoparticle powders is a notable safety concern. In construction, knowledge gaps in risk assessment are very much a function of unknown and under-characterized potential exposures to nanomaterials. MEASUREMENT TECHNIQUES Historically, the construction industry has overlooked occupational exposures toward the end of the product life cycle (for example, PCBs, lead, and asbestos). The organization of construction work also affects exposures. Work sites can change daily, with different trades coming and going as the project progresses, presenting different levels of knowledge, experience, and training. Whether workers are renovating an existing structure or building a new one, nanoparticles may be a component of various materials on site, making it difficult to identify and minimize exposures. The frequent presence of multiple contractors also raises the issue of exposures to bystanders. The diverse nature of construction tasks and materials, and the high levels of energy typical of power tools and machinery used in construction, increase the likelihood of ENP release and exposure. Characterizing ENPs, including forms of release, is just as important as quantifying exposures. Research published in the Journal of Environmental Monitoring suggests that nanoparticles released from products tend to be matrix-bound, but some fraction is also released as single, dispersed nanoparticles. The matrix-bound nanoparticles will change over their expected life cycle.
For example, a polymeric, multi-walled CNT composite can undergo conformational changes depending on the rigidity of the polymer matrix, degree of cross-linkage, degradation, expansion, contraction, and so on. Recent studies have not indicated a hazard from the sanding of products containing nanomaterials, but exposure assessments in construction are limited and more work is needed.
In the November 2013 Synergist, Jennifer Dimitri, Keith Rickabaugh, Paul Webb, and Michele Shepard, members of the AIHA Nanotechnology Working Group, provide an excellent overview of industrial hygiene sampling strategies and equipment for assessing nanomaterial exposures. Construction exposures pose some additional challenges, however. Rain, snow, and wind can limit the use of real-time instrumentation. Extending the sampling times to ensure a good detection limit for transmission electron microscopy (TEM), as the authors reasonably suggest, can lead to overloaded samples in construction where grinding, cutting, and drilling generate extraordinary levels of dust. (In one instance, we overloaded samples after 13 minutes of grinding mortar, precluding direct preparation for TEM analysis by a modified version of the NIOSH 7402 method.)
"Without labeling requirements, there is no practical way demolition workers can know whether they are being exposed.​"
Worker grinding mortar while wearing a powered air-purifying respirator. Photo credit: Neil Lippy/eLCOSH​
HAZARD CO​MMUNIATION​ NIOSH has produced excellent guidance for IH practitioners on reducing exposures to ENMs. Very little of the guidance developed thus far, however, has been aimed at workers. The federal government’s only guidance on training workers about the risks of nanomaterials is from the National Institute of Environmental Health Sciences (see http://bit.ly/nanotraining).
At a minimum, hazard communication should inform contractors and workers whether nanoparticles have been added to the products they might install, disturb, or demolish on construction sites. But according to research from Europe published in 2011 by the Journal of Nanoparticle Research, 80 percent of workers and 71 percent of employers were “not aware of the availability of nanomaterials and were ignorant as to​ whether they actually used nanomaterials at their workplace.” No similar research has been published for the U.S. construction industry; however, written surveys we conducted in 2013 and 2014 of 79 union trainers from 15 different trades with an average of 30 years’ experience found that almost half were unaware that nanotechnology has been applied to construction materials.
The OSHA website indicates that the agency’s new globally harmonized hazard communication standard may be applicable to nanomaterials but offers no guidance on effectively applying it. A NIOSH report published in the Journal of Chemical Health and Safety states that 67 percent of nano safety data sheets (SDSs) collected during 2010–2011 “provided insufficient data for communicating the potential hazards of ENM documented.” A web search can turn up SDSs for carbon nanotubes that cite the OSHA permissible exposure limit for synthetic graphite of 5 mg/m3, which is 5,000 times higher than the new NIOSH REL of 1 µg/m3.
There are no requirements in the U.S. for companies to report the inclusion of nanoparticles in product SDSs. Consequently, construction industry stakeholders have no means to reliably identify nano-enabled construction materials. Many companies do acknowledge the addition of nanoparticles but often provide no further information or designate the information as proprietary. Compounding the difficulty, products identified as nanomaterials may not actually contain nano-objects. The particles may be larger than 100 nanometers or the material may be nano-structured (that is, having internal or surface structure in the nanoscale). Without knowing the chemical composition of the nanoparticles in a product, planning a sampling strategy is exceedingly difficult since many NIOSH sampling protocols are element-specific.
Hazard communication becomes daunting when considering the life cycle of construction products. The most serious exposures might occur many years after installation, when the facility is being renovated or demolished. Without labeling requirements, there is no practical way demolition workers can know whether they are being exposed. Bulk sampling of building materials, as is now required for suspected asbestos-containing materials, could identify nano-objects prior to demolition, but this seems a remote possibility given the general lack of sampling on construction sites and the cost of TEM analysis. The parallel between nanomaterials and asbestos raises the question of whether the government may eventually intervene and require identification of nanomaterials prior to demolition. Ironically, nano-enabled materials may extend the life expectancy of buildings by decades, further reducing the likelihood that workers will know nanoparticles are present.
​There is a bright spot. In 2012, the International Standards Organization (ISO) produced excellent guidance on preparing SDSs for nanomaterials. The report applies the precautionary principle and requires (with few exceptions) the writing of SDSs for all manufactured nanomaterials, regardless of whether the bulk material is classified as hazardous. ISO recommends that manufacturers provide primary particle size, size distribution, aggregation state, shape, aspect ratio, crystallinity, surface area, and dustiness. If manufacturers conscientiously follow this guidance, industrial hygienists will be able to better characterize exposures and protect workers.
RESEARCH GAPS​ The lion’s share of nanotechnology research funding in the U.S. is dedicated to innovation, development, and commercialization of new applications, though the proportion of funding for environmental health and safety (EHS) research has grown in recent years. This trend may reflect growing concern for unknown and under-characterized risks related to nanotechnology. Despite recent growth, nano EHS research accounts for only 7 percent of the 2015 National Nanotechnology Initiative research funding, according to Nano.gov. Considering the current pace of innovation, it is reasonable to expect that novel applications of nanotechnology in construction will continue to be brought to market faster than relevant research on health effects.
European researchers laid much of the groundwork for examining occupational health and safety aspects of nanotechnology in construction. A study published in the Journal of Nanoparticle Research found the use of nanoproducts in the European construction industry to be relatively low in 2009, representing a niche market comprised primarily of coatings, concrete, and cement. The study identified high costs and uncertainty regarding adverse occupational risks of ENPs as barriers to adoption.
The study also measured exposure to nanoparticles in a limited number of construction work environments, finding low-level exposure to nanoparticles that did not exceed preliminary European nano reference values for workplace exposure. The authors highlighted the difficulty of distinguishing ENPs from incidental nanoparticles generated via machine exhaust and cigarette smoke, for example. During one test, more nanoparticles came from the electric motor of a drill than from the substrate when the drill was engaged.  
Other studies of ENP exposure in construction provide little cause for alarm, but more work is clearly needed. Also, synergistic effects are particularly important in construction because of the diverse activities occurring simultaneously in shared work space. In 2010, according to Occupational and Environmental Lung Diseases: ​Diseases from Work, Home, Outdoor, and Other Exposures, more than half of construction workers reported exposure to vapors, gas, dust, or fumes twice a week or more.
NIOSH, in addition to offering RELs and guidance, has characterized the toxicity of nanomaterials, developed sampling and analytical methods, evaluated control technologies, and collected exposure measurements in a variety of workplaces, including production facilities and insulator apprenticeship schools. The agency also partners with the Center for Construction Research and Training (CPWR), a 501(c)(3) not-for-profit institution that currently serves as the NIOSH-funded National Construction Research Center. As part of its agreement with NIOSH, CPWR has undertaken a five-year research project dedicated to nanotechnology in construction.
CPWR has been identifying commercially available nano-enabled construction products, in part to foster greater understanding in the construction industry of potential risks, benefits, and safe work practices related to use of these products. As of this writing, CPWR’s inventory contains more than 400 products. The inventory is publicly available on eLCOSH, the electronic Library of Construction Occupational Safety and Health (www.elcosh.org), which is managed by CPWR.
The inventory will be used to select candidates for exposure assessment. CPWR has measured nanoparticle exposures and efficacy of controls during cutting, drilling, and nailing of photocatalytic roofing tile, and during grinding of mortar-patching compound. CPWR plans to conduct additional assessments of nanoparticle exposures during performance of routine construction tasks in both indoor and outdoor environments. In addition to publication, findings will be disseminated to workers and used to develop training materials.
CPWR has been communicating with researchers at Loughborough University who have secured similar funding from the UK-based Institution of Occupational Safety and Health (IOSH) to identify nano-enabled construction products in Europe and to characterize potential releases and exposures. The UK research focuses on the recycling and demolition phase of the product life cycle, whereas CPWR’s work examines initial product use and application as well as maintenance and repair. We hope the complementary nature of these projects will promote responsible development of nanotechnology by filling gaps in understanding health and safety risks across the life cycle of nano-enabled construction materials.
Gavin H. West, MPH

Bruce Lippy, PhD, CIH, CSP

Daniel Marsick, PhD, CIH, CSP

Michael R. Cooper, CIH, CSP, MPH
is a research analyst with CPWR - The Center for Construction Research and Training.

is director of safety research at CPWR and a member of the AIHA Nanotechnology Working Group.

is principal of Marsick Consulting, LLC, and a member of the AIHA Nanotechnology Working Group.

is a consultant to CPWR and a member of the AIHA Nanotechnology Working Group. ​
Unknown Risks: Nanomaterials in Construction