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Nanomaterials Raise More Questions than Answers
In 2011, the National Institute for Occupational Safety and Health (NIOSH) released its first recommended exposure limit (REL) for nanoparticles. Since that time, NIOSH has released RELs for additional types of nanoparticles, including carbon nanotubes (CNTs), carbon nanofibers (CNFs) and ultrafine titanium dioxide (TiO2).
“The benefits of using nanomaterials in construction are well-documented. Adding nanoparticles to base materials like concrete or steel can make them stronger, more durable or more flame resistant,” says LIUNA General President Terry O’Sullivan. “But the potential negative effects and long-term health risks are still unknown and will likely continue to be for years. When it comes to nanomaterials, we should proceed with caution.”
Because of the uncertainty over these chronic health effects, NIOSH recommends reducing exposure to CNT and CNF “as much as possible” – below 1 μg/m3 of respirable elemental carbon as an 8-hour time-weighted average (TWA) during a 40-hour workweek.
Laborers can be exposed when handling materials containing nanoparticles, but also face potential exposure later during demolition (e.g., with jackhammers). With the popularity of nanomaterials growing, these materials could pose a hazard to workers for years to come.
Part of the difficulty in assessing the hazards that nanoparticles present is that their physical properties vary widely. Even though nanoparticles are only a few atoms thick (thousands of times thinner than a human hair), their differing structures, shapes and chemical properties affect how they interact once they enter the body. Because of this, researchers and regulatory agencies aren’t able to treat nanoparticles like they treat asbestos or silica, for example. Instead, each type of nanoparticle must be considered separately, similar to how hazardous chemicals each have their own safety data sheet. Adding to this difficulty is the fact that safety data sheets often don’t list whether nanoparticles are included in a product.
Though nanoparticles exhibit different properties, all are small enough to be easily inhaled, which could cause them to lodge deep in the lungs. They can also be swallowed or absorbed through the skin and can travel through the body via the circulatory system. Several studies have linked nanoparticles to lung disease and cancer, and though there’s no conclusive data to show the effect nanoparticles have on humans, studies have shown certain nanoparticles to cause respiratory problems similar to asbestos exposure in mice.
In an effort to further research on the occupational health and safety of nanoparticles, NIOSH launched the Nanoparticle Information Library. This library “provides instant access to information that would take hours to find otherwise, and offers a dedicated cyber-forum to help scientists communicate and network with each other,” said NIOSH Director John Howard, M.D.
The Library contains information from both NIOSH scientists and outside contributors and will be continually expanded as new information is available. Users can search the site and find information relevant to occupational safety and health studies, including:
- Size, shape, structure, surface characteristics and chemical properties
- The particle’s origin or method of synthesis (if known)
- Applications, industries and any related occupations (if known)
- Links to safety data sheets and applicable toxicity studies
- Best practices for production and workplace use
Currently, OSHA standards don’t address nanomaterials, making it difficult to determine or even estimate a safe exposure level. NIOSH is studying engineering controls that could protect workers by placing a barrier between them and the nanoparticles, and is also examining safe handling techniques. These methods are likely to be the most effective control strategies for nanomaterials. The NIOSH Science Blog has also examined the use of respirators to reduce nanoparticle exposure, but noted concerns that very small particles could still pass through filters or leak through small gaps between the mask and the wearer’s face.
CPWR – the Center for Construction Research and Training – created the Construction Nanomaterial Inventory to bring awareness to contractors and workers about which products on the market today contain nanoparticles. The inventory contains over 400 products sorted by material type, including several categories Laborers often come in contact with (e.g., concrete and cement additives, flooring, roofing, insulation). Click here to read more about the CPWR’s Nanotechnology Initiative.
To find out more about controlling exposure to nanoparticles, visit the CDC’s Nanotechnology page or read this NIOSH publication titled Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes.