THURSDAY, MAY 2, 2013
Nanotechnology holds great promise for paints and coatings, but those microscopic carbon nanotubes and fibers may also carry large risks for workers exposed to them, federal health officials warn.
How large a risk? New exposure guidelines set safe levels for workers at nearly zero.
The guidelines, published April 24 by the National Institute for Occupational Safety and Health (NIOSH), recommend limiting worker exposure to just one microgram per cubic meter of air per eight-hour workday.
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The bulletin includes toxicology data and strategies for controlling worker exposures. |
That is the minimal amount that can be measured by current equipment, Andrew Maynard, chair of environmental health sciences at the University of Michigan in Ann Arbor, recently told USA Today.
‘As Low as We Can Measure’
“They’ve set the limit as low as we can measure,” Maynard said.
Part of the Centers for Disease Control and Prevention, NIOSH does not mandate standards, but its findings are followed closely by regulatory agencies and private industry.
NIOSH is the leading federal agency that conducts research and provides guidance on the occupational safety and health implications and applications of nanotechnology. Its new recommendations are the first of their kind and follow six years of research on carbon nanofiber and nanotube safety.
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Tesla NanoCoatings Ltd., of Massillon, OH, has attracted awards and funding for its corrosion control coatings made with fullerene carbon nanotubes (CNTs). |
Scope of Research
NIOSH’s Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers:
Respiratory Hazards
Nanotechnology generally referes to engineered structures, devices and systems between 1 and 100 nanometers long.
Many of technology’s burgeoning first generation of products. including paints and coatings, are composed of engineered nanoparticles, such as metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes (buckyballs). Much current coatings research also focuses on nanotechnology.
However, the same teeny size that makes nanoparticles attractive for incorporating into products “may pose a greater health risk than the larger bulk form of these materials,” NIOSH said.
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Battelle has been testing a CNT-based anti-icing coating in tunnels that replicate FAA-defined known icing conditions. |
“Results from recent animal studies indicate that carbon nanotubes (CNT) and carbon nanofibers (CNF) may pose a respiratory hazard.”
Complicating understanding of the health risks is the tremendous variety in the nanoparticles’ shape, size and chemical composition, NIOSH said.
Adverse Lung Effects
The risks apply to several types of exposures, NIOSH said.
“Occupational exposure to CNTs and CNFs can occur not only in the process of manufacturing them, but also at the point of incorporating these materials into other products and applications,” the agency found.
The agency cites “a number of research studies” that show pulmonary inflammation, “rapidly developing, persistent fibrosis” and other “adverse lung effects” on rodents from low-dose exposures to CNT and CNF. The particles' carcinogenic potential in animals is still being studied, NIOSH said.
“Although it is not known whether similar adverse health effects occur in humans after exposure to CNT and CNF, the results from animal research studies indicate the need to minimize worker exposure,” NIOSH said.
Tumors in Mice
Just weeks before issuing the new guidance, NIOSH presented the findings of a new study, in which mice were exposed to inhalation of multi-walled carbon nanotubes.
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A new study suggests that carbon nanotubes could be "a cancer promoter." |
The study suggested that the nanotubes could increase the risk of cancer in mice exposed to a known carcinogen. NIOSH called the particles “a cancer promoter” but emphasized that the nanotubes alone did not cause cancer in mice.
Nevertheless, the researchers recommended using “prudent practices” such as containment, local exhaust ventilation, filtration, and personal protective equipment, including respirators, in the workplace.
Another NIOSH study, published last August in the peer-reviewed Future of Medicine, suggested that nanoparticle exposures to mice and human cells in the lab produced cellular changes associated with risks for autoimmune disorders like rheumatoid arthritis.
Regulations
Coatings are increasingly turning to nanomaterials, including CNTs. Carbon nanotubes and other nanomaterials have found varied applications in paints, coatings and a wide range of other products. With the trend growing, regulation of these materials is likely in the years ahead.
Many nanoscale materials are already regarded as "chemical substances" under the Toxic Substances Control Act (TSCA).
Meanwhile, in 2010, the Environmental Protection Agency began developing a Significant New Use Rule (SNUR) and other regulations to address potential health and environmental risks from nanoscale materials.
And in December 2012, EPA announced that it would conduct research with the Consumer Products Safety Commission on the health and environmental effects of many nanomaterials.
The Occupational Safety and Health Administration (OSHA) currently includes nanomaterial exposures under its General Industry standards.
Tagged categories: Coating chemistry; Coating Materials; Containment; EPA; Nano and hybrid coatings; Nanotechnology; NIOSH; OSHA; Personal protective equipment; Research; Respirators; Tesla NanoCoatings
