Sometimes, something meant for good may actually have unintended negative side effects. Take the case of silver nanoparticles in today's consumer products, for instance. While originally meant for killing bad bacteria, Professor Zhiqiang Hu believes that the nanoparticles may kill off benign bacteria as well.

The University of Missouri researcher says that the double-edged nature of silver nanoparticles comes from the fact that they generate unique chemicals known as highly reactive oxygen species. The chemicals tend to inhibit bacterial growth, but apparently make no distinction between good or bad bacteria.

The implications of this are clear: if enough of these silver nanoparticles find their way into sewage lines, activities such as wastewater treatment could be affected. As Hu put it:

Because of the increasing use of silver nanoparticles in consumer products, the risk that this material will be released into sewage lines, wastewater treatment facilities, and, eventually, to rivers, streams and lakes is of concern.

We found that silver nanoparticles are extremely toxic. The nanoparticles destroy the benign species of bacteria that are used for wastewater treatment. It basically halts the reproduction activity of the good bacteria.

Hu is conducting follow-up research on the matter, specifically at which levels the substances start to become toxic. The Water Environment Research Foundation recently awarded him US$ 150,000 for this endeavor.