EVERYONE KNOWS what a millimetre looks like: a thousandth of a metre, right? Now try wrapping your mind’s eye around something that is a million times smaller than that.
Welcome to the world of nanotechnology, where some very small things are leaving occupational hygienists with some very big questions.
Nanotechnology is currently used primarily in industries and research facilities that manufacture or construct materials measured in nanometres (that’s billionths of a metre). despite current limited applications, the technology is raising concern that it may introduce new classifications of toxins or environmental hazards.
Nanopaticles are created through high-energy processes such as welding, fuel-processing and generation of diesel exhaust. These processes produce particulate matter that, when inhaled, enter the respiratory and digestive system, but can eventually travel to the liver, central nervous system and cardiovascular system. Being as small as they are, nanoparticles behave more like gas molecules than solid particles.
Conclusive evidence exists about the toxic nature of vehicle exhausts, says a paper released last April by the ETC Group (Action Group on Erosion, Technology and Concentration). But scientists do not believe it’s possible to infer conclusions about toxicity of industrial pollutants to manufactured nanoparticles. In other words, there is a difference in toxicity between materials created as a by-product and those that are intentionally manufactured.
An occupational hygienist based in Windsor, Ontario says “respirable particle effect is no longer confined to the lung since smaller particles are suggested to translocate to the blood while lung inflammation invokes systemic responses. Similarly, nanoparticles are theorized as being able to cross the blood brain barrier. There are great health impacts associated with this.”
Little is known about the risk of exposure during manufacturing and handling of nanoparticles. There are no regulatory requirements for the testing of nanoparticles for health, safety or environmental impacts. Conclusive date for risk assessment is conspicuously lacking.
Add to this the potential introduction of new hazards and occupational hygienists in sectors using nanotechnology are presented with substantial challenges. Those challenges, in turn, move on to the companies for which these hygienists work.
Everything on earth is made from atoms and properties of specific substances depend on how those atoms are arranged. If we consider pure carbon, for example, one rearrangement produces graphite while another produces a diamond. Consider also that if we rearrange the atoms in sand, then add a few other trace elements, we have computer chips.
Nanoparticles are so small they cannot be seen by the unaided eye. Although not the only interpretation, the National Nanotechnology Initiative in the United States defines “nano” as between one and 100 nanometres (nm). Because of their size, these very small particles can pass right through particulate filters, including those worn by workers to protect themselves. If a filter was fine enough to trap the molecules, it would also severely restrict any air passing through.
Nanoparticles are currently used in paints, coatings for textiles, sunscreens, cosmetics and power machinery, along with the carbon nanotubes intended for electronics. The National Science Foundation reports that, within 10 years, the entire semiconductor industry will rely on nanotechnology and on nano-materials. Fundamental changes are also expected in terms of medicine, as well as drug production and delivery.
But before nanoparticles become part of the paint or sunscreen, they have to be produced. That means people manufacturing these particles are doing something that is seemingly far more comp;ex than just rearranging those carbon atoms into diamonds. And to produce new products in future, industry will have to respond by creating new tools and new manufacturing processes — that is molecular manufacturing systems.
The smaller the particulate size, the ETC Group paper notes, the more toxic and reactive it may be. Regardless of the chemical composition of a ‘nanothing’, ultra-small materials can be ultra-hazardous. It is already well-known that ultra-fine (generally defined as particles measuring less than 100 nm) materials have the ability to induce respiratory damage.
A paper prepared by Dr. David Warheit, research fellow for DuPont Haskell Laboratory for Health and Environmental Sciences in Newark, Delaware, says toxicology studies in rats demonstrate that ultra-fine particles administered to the lung cause a greater inflammatory response when compared with larger particles of identical chemical composition at equivalent mass concentrations.
In 2002, when researchers at DuPont instilled tubes of carbon (nanotubes developed for their strength and electrical conductivity) into the lungs of rats, the rats gasped for air, and 15 percent quickly died. Yet the experiment did not answer the critical question of what quantity and what level of exposure is safe, or what LEL of exposure is necessary for the rats to breathe in damaging amounts of the nanotubes.
This, says occupational hygienist Neil Langerman, is currently not a problem since, to protect the product, all of the processes are carried out in quite clean envionments, with little to no dust.
But harm to the lungs is not the only worry, says a recent article in the New York Times by Barnaby J. Feder, with research indicating inhaled nanoparticles can move directly into the brain. In the article, Feder concludes this may carry health impacts and make it very difficult to draw common conclusions about the potential effect of nanoparticles on human health.
The cost and difficulties of researching risk has caused some companies to put a halt to their programs. The French research wing of the cosmetics giant, L’Oreal, has stopped research into the characteristics of buckyballs – nanotubes made from buckminsterfullerones – after independent researchers raised questions about toxicity.
Despite 25 years of laboratory work on nanoparticles around the world, scientists have still not managed to agree upon safety protocols to protect workers even though many organizations, such as the Canadian Institute of health Research have attempted to do so. This, most likely, is because the toxicology of nanoparticles in not yet understood and groups cannot agree on the risks of the new technology to human health and the environment.
There are no tests for the effects of inhaled nanoparticles, and no threshold limit values (TLVs). As such, there is no level in the work environment at which an occupational hygienist can ascertain the safety or health risk to workers who are exposed.
In the United States, the national Institute for Occupational Safety and Health (NIOSH)has performed some research with regard to airborne and dermal exposure routes and toxicity of single-walled carbon nanotubes (allotrope of carbon). Over at the Environmental Protection Agency, a focused research progjram on the impacts of manufactured nanomaterials on human health and the environment is expected to begin early this year.
And the national Toxicology Program, for its part, will develop protocols over the next five years to test for toxicity in animals using nanomaterials provided by the Center for Biological and Environmental Nonotechnology (CBEN) at Rice University in Houston, Texas. The Center was founded in 2001 to address the impact of engineered nanomaterials on human health and the environment.
“We have a unique opportunity to ensure that a nascent industry develops responsibly by addressing safety concerns early in its development says Dr. Kristen Kulinowski, executive director for education and public policy at the CBEN.
Today’s occupational hygienists will continue to face a substantial challenge regarding how to monitor, assess and control possible workplace hazards with little understanding of the hazard.
But there may be another side that should be considered. If technology enables the elimination of current industrial processes, certain toxic exposures will be either eliminated or reduced.
The best course of action, right now, may be to keep abreast of research and changes in nanotechnology. If nanoparticles are present in your workplace, stakeholders need to discuss the options for strategies that will minimize exposure.
Gloria’s article was first published in OHS Canada.
My first introduction to the application of nanotechnology was during an Inspection of a cosmetics plant in Toronto, Ontario. Workers in the manufacturing department looked like laboratory workers employed in any large hospital or research centre: they were gowned up, gloved up, masked up. My first question was, “what’s your strategy to protect workers?”