The 21st century offers the promise of a new application of science and technology – Nanomaterials.
While anything in the submicron range may qualify as a nanomaterial, the greatest promise is associated with materials that are less than 100 nanometers in size. Some of these nanomaterials, such as carbon black and fumed silica, have been in use for many decades. Carbon black is considered to be “possibly carcinogenic to humans” and fumed silica is known to irritate the respiratory system.
From carbon nanotubes to quantum dots, the potential applications of modern nanotechnology are impressive. So are the challenges of assessing the impacts of these materials, once they are released into the environment.
What makes the management of Nanomaterials complex?
It is estimated that many millions of tons of a diverse array of nanomaterials will be manufactured on an annual basis, in the years to come. Some of the modern applications of these novel materials are less than a decade old. They are also expected to add trillions of dollars in revenue to the global economy.
Let us look at how one fundamental aspect of these materials, their size, influences a broad range of properties, from adsorption to dispersion in the environment. As particles shrink, their effective surface area increases dramatically. Due to their small size, the recovery of nanomaterials released into the environment is also highly unlikely.
For example, a nanomaterial that weighs 1 gram per cubic centimeter (same density as water) can produce a nanomaterial or “dust”, made up of 100 nm cubes/particles, with a surface area of ~60 square meters. A kilogram of this dust would cover almost 2 football fields, if spread out evenly, one particle thick. With this understanding, we can begin to appreciate the promise and challenges of working with nanomaterials. They are extremely effective, on a weight basis, at interacting with and influencing the physical and chemical properties of the materials (matrix) they are dispersed in.
The magic of nanomaterials lies in their large interfacial area, allowing for a large number of interactions at the molecular level, with whatever they come in contact with. From advanced sensor technologies using nanotubes and quantum dots, to branched polymer transport/delivery systems known as dendrimers, and specialized surface coatings to alter the properties of common materials, they will revolutionize the applications of materials science in the 21st century.
But what about the adverse effects nanomaterials have on human beings and the environment? We know very little about the fate and persistence of some of these modern materials. Risk assessments, addressing both the long-term human toxicity and ecotoxicity profiles of these materials, are needed.
Looking ahead…
The U.S. Environmental Protection Agency(EPA) has initiated a review of some nanomaterials currently being used. Materials like carbon nanotubes– used in structural applications, nanometals (e.g., iron, silver) – used for environmental remediation and as an antibacterial, and titanium dioxide– used in cosmetics and paints/coatings, and apparently even in donuts. Similar studies are underway in the European Union(EU).
A collaborative research and development perspective is needed, using an interdisciplinary approach to provide a favorable environment for both ethical considerations and innovation. Opportunities for public input, allowing both informed and independent assessments, are needed to balance the engines of commerce with the costs of future remediation.