The EPA is taking an active role in developing extending existing regulatory frameworks for potentially toxic manufacturing materials to nanotechnology. The Agency wants to ensure that manufacturers of carbon nanotubes meet their Toxic Substance Control Act (TSCA) obligations in registering new molecular formulations of carbon nanotubes and other nanotechnology building blocks.
Nanotubes Similar to Asbestos Fibers
The overriding concern on the rapidly growing use of nanotubes for research and development – for a variety of products that may lead to a multibillion dollar industry in a matter of a few years – is that nanotubes have been shown to function much like asbestos fibers when exposed to lung lining tissue. Pleural mesothelioma is the lethal asbestos caused cancer that has killed tens of thousands of workers over the past century who suffered asbestos exposure on the job.
A study conducted at North Carolina State using mice in an animal model study set out to determine what happens when multi-walled carbon nanotubes are inhaled. Specifically, researchers wanted to determine whether the nanotubes would be able to reach the pleura, which is the tissue that lines the outside of the lungs. The researchers used inhalation exposure and found that inhaled nanotubes do reach the pleura and cause health effects.
Short-term studies described in the paper do not allow conclusions about long-term responses such as cancer. However, the inhaled nanotubes “clearly reach the target tissue for mesothelioma and cause a unique pathologic reaction on the surface of the pleura, and caused fibrosis,” says Dr. James Bonner, associate professor of environmental and molecular toxicology at NC State and senior author of the study.
The “unique reaction” began within one day of inhalation of the nanotubes, when clusters of immune cells began collecting on the surface of the pleura. Localized fibrosis, or scarring on parts of the pleural surface that is also found with asbestos exposure, began two weeks after inhalation. Scarred internal lung tissue results in asbestosis when asbestos fibers lodge within the lung.
EPA to Enforce Rules on Carbon Nanotubes
EPA officials have indicated that they plan to follow through on their previously announced plan to take enforcement action against companies manufacturing or importing carbon nanotubes that have not submitted premanufacture notices (PMNs) as required by the TSCA. Along with this threat of enforcement, EPA has issued Significant New Use Rules (SNURs) for a single- and a multi-walled carbon nanotube. EPA has also indicated that it may issue additional test rules for these newly developed types of carbon nanotubes.
Carbon Nanotubes, An Occupational Risk
One of the results has been a protest by the European Union over what is being perceived as restrictive actions on products and composite materials now being developed for manufacturing purposes. The EPA is faced with a burgeoning industry based on a newly conceived building block for which there has not been adequate research on the potential impact of workplace exposure such as occurred with asbestos. Just as genetic modification of food genetics has had unintended consequences, the proliferation of carbon nanotube use can develop into another industrial health disaster like the asbestos cancer that overtook generations of twentieth century workers.
