A Beautiful Mind

In recent years, an eclectic band of scientists has mapped out a new frontier known broadly as nanotechnology. Though they're from different traditions and methods, these explorers, who include biologists, chemists, physicists, chipmakers, and computational experts, have tackled the same basic question: how to control the building blocks of matter from the bottom up.
They're learning how to guide individual atoms as they combine to form molecules and, in turn, how to make materials -- molecule-by-molecule -- that don't exist in nature. Their work cuts across some of the hottest areas of science, including innovative drug-delivery systems, cancer treatments, ultrastrong lightweight metals, and mass-produced superconducting wires -- to name a few.

What i can summarise according to the leading scientists there are two broad categories of risk assessment going on right now :

One is in biological systems -- starting with the effects on individual cells and up to more sophisticated organisms such as vertebrate animals. There's a lot of work going on this area already -- looking at how nanoparticles affect bacteria or how they accumulate in cells, for example.
The second major category looks at the environment. Do nanomaterials accumulate in water or the earth, and if so, do they pose a risk to the environment? Are they changing the balance of a water supply in terms of bacteria. If we're making lots of nanoparticles and they become part of waste stream, what happens to them in the long run?
It's really about sustainability. Can we engineer our manufacturing processes and these materials to have an environmentally benign lifecycle from when they're made in the factory to when they're put in a landfill?