In anticipation that the numbers of US workers exposed to nanomaterials will rise significantly in the next ten years, the National Institute for Occupational Safety and Health (NIOSH) is recommending new exposure levels to prevent the health damage that may potentially result from inhaling chemical substances or materials that can be thousands of times thinner than the diameter of a human hair.
NIOSH is the first federal agency to issue recommended exposure levels for nanomaterials in the workplace. The aim is to reduce the potential harm that the materials might cause to workers’ lungs.
In a new bulletin, NIOSH, which is part of the US Centers for Disease Control and Prevention, reports the results of animal tests that show inhaling various types of carbon nanotubes or carbon nanofibers can cause lung damage, including pulmonary fibrosis, inflammation, and granuloma.
NIOSH says the animal studies show lung damage can occur at relatively low doses of carbon nanotube or nanofiber.
Although carried out in animals, the studies have implications for human health, because the damage in animal lungs is similar to that seen in human lungs exposed to tiny particles and dust already studied in occupational settings, says the agency.
Carbon nanotubes and carbon nanofibers are only two examples of the types of materials manufactured at the nanoscale.
Many of the nanomaterials currently in use are made of engineered nanoparticles such as metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes (buckyballs).
They are routinely handled by workers in industries like aviation, automotive, cosmetics, plastics, ceramics, paints, coatings, electronics, manufacturing of construction materias, batteries, textiles, and consumer goods such as sporting products.
Although hundreds of products containing nanomaterials are already in use, the numbers of workers that are potentially exposed to nanomaterials cannot be determined with certainty, says NIOSH.
But the agency says the industry is growing, and demand is expected to rise in sectors like energy saving products, consumer goods and medical devices.
In medicine alone, nanotechnology promises to revolutionize drug delivery, gene therapy, diagnostics, and many areas of research, development and clinical application.
The NIOSH recommendation provides a “quantitative risk assessment based on animal dose-response data”, and proposes a recommended exposure limit of “1 μg/m3 elemental carbon as a respirable mass 8-hour time-weighted average (TWA) concentration”.
The Bulletin also outlines some approaches that organizations can take to control workplace exposures and implement medical monitoring.
However, it also notes that while the recommended levels are “expected to reduce the risk for pulmonary inflammation and fibrosis”, neither of which is a cancerous condition, because of the uncertainty surrounding whether this limit applies to chronic conditions, including cancer, ” continued efforts should be made to reduce exposures as much as possible”.
One of the many challenges in trying to estimate the harm potential of nanomaterials is the large variation in shape, size, chemical compostion, and other physical and chemical properties.
NIOSH has already seen this challenge in the animal studies on the effects of carbon nanotube or nanofiber.
“Such variations in composition and size have added to the complexity of understanding their hazard potential,” says the new bulletin.
Workers can be exposed to these materials not only in the process of manufacturing them, but also at the point of adding them into other products.
NIOSH urges employers to share this information with their workers and their customers, and asks that professional groups, trade associations and labor organizations inform their members about the potential hazards of working with nanomaterials.