The potential impact of nanostructured particles and devices on the environment is perhaps the most high profile of contemporary concerns. Quantum dots, nanoparticles, and other throwaway nanodevices may constitute whole new classes of non-biodegradable pollutants that scientists have very little understanding of. Essentially, most nanoparticles produced today are mini-versions of particles that have been produced for a long time. Thus, the larger (micro) versions have undergone testing, while their smaller (nano) counterparts have not.
For example, Vicki Colvin, Executive Director of Rice University’s Centre for Biological and Environmental Nanotechnology (CBEN) has recently postulated that nanomaterials provide a large and active surface for adsorbing smaller contaminants, such as cadmium and organics. Thus, like naturally occurring colloids, they could provide an avenue for rapid and long-range transport of waste in underground water.
Could Nanomaterials Infiltrate Humans?
The concern that nanomaterials could bind to certain common but harmful substances in the environment, such as pesticides or PCBs, leads to the short-term worry of such materials infiltrating humans. According to the ETC Group, at a recent fact-finding meeting at the US Environmental Protection Agency (EPA), researchers reported that nanoparticles can penetrate living cells and accumulate in animal organs. In particular, the possibility of toxic elements attaching themselves to otherwise benign nanomaterials inside bacteria and finding a way into the bloodstream was acknowledged.
What Effects might Nanomaterials have on Living Systems?
In addition, very little work has been done in order to ascertain the possible effects of nanomaterials on living systems. One possibility is that proteins in the bloodstream will attach to the surface of nanoparticles, thus changing their shape and function, and triggering dangerous unintended consequences, such as blood clotting.
Nanoparticles and the Human Immune System
A second possibility relates to the ability of nanoparticles to slip past the human immune system unnoticed, a property desirable for drug delivery, but worrying if potentially harmful substances can attach to otherwise benign nanomaterials and reside in the body in a similar manner. According to Colvin, ‘it is possible to speculate that nanoscale inorganic matter is generally biologically inert. However, without hard data that specifically addresses the issue of synthetic nanomaterials, it is impossible to know what physiological effects will occur, and, more critically, what exposure levels to recommend.’
What are the Effects of Nanotubes on the Human Body?
To illustrate, this report shows how nanotubes, should industry predictions be realised, are set to become relatively ubiquitous within the coming decades - such materials are already finding their way into a number of products. But it has not yet been determined what happens if, for example, large quantities of nanotubes are absorbed by the human body.
One prominent concern relates to the structural similarities between nanotubes and asbestos fibres: like the latter, nanotube fibres are long, extremely durable, and have the potential to reside in the lungs for lengthy periods of time. One recent study, conducted by the National Aeronautics and Space Administration (NASA), has shown that breathing in large quantities of nanotubes can cause damage to lungs. However, as nanotubes are essentially similar to soot, then this is not particularly surprising. On the whole, far more experiments are required before the issue can be resolved.
What about the Dangers of Self-Replicating Nanorobots?
Self-replication is probably the earliest recognized and best-known long-term danger of molecular nanotechnology (MNT). This centres upon the idea that self-replicating nanorobots capable of functioning autonomously in the natural environment could quickly convert that natural environment (i.e. ‘biomass’) into replicas of themselves (i.e. ‘nanomass’) on a global basis. Such a scenario is usually referred to as the ‘grey goo’ problem but perhaps more properly termed ‘global ecophagy’ (Freitas). The main feature that distinguishes runaway replication as a long-term environmental concern is the extreme difficulty involved in constructing machines with the adaptability of living organisms. As Freitas notes:
‘The replicators easiest to build will be inflexible machines, like automobiles or industrial robots … To build a runaway replicator that could operate in the wild would be like building a car that could go off-road and fuel itself from tree sap. With enough work, this should be possible, but it will hardly happen by accident. Without replication, accidents would be like those of industry today: locally harmful, but not catastrophic to the biosphere. Catastrophic problems seem more likely to arise though deliberate misuse, such as the use of nanotechnology for military aggression.’
Are there Checks to Ensure that Molecular Machines are Produced Safely?
This is not to imply, however, that the risk that molecular machines designed for economic purposes might replicate unchecked and destroy the world should be written off altogether: while the danger seems slight, even a slight risk of such a catastrophe is best avoided. To this end, David Forrest has produced a set of guidelines to assure that molecular machines and their products are developed in a safe and responsible manner.
Note: A complete list of references can be found by referring to the original text.