Sheep, Goats, and Nanoparticles

I was a child when introduced to the phrase, “separating the sheep from the goats.” Although the saying has biblical roots, I typically heard it in reference to distinguishing between good and bad, or between high and low value. Recently, I’ve been thinking about it with respect to nanotechnology.

Earlier this year I participated in a public event, and we were asked: “Are nanomaterials safe?” This reasonable question comes up often, sometimes in the negative form, “Are nanomaterials dangerous?” I have begun prefacing my response by asking that we reframe the question.

This is where sheep and goats come in.

Nanoparticles taken as a large group actually seem to be a mixed collection of at least these two ruminants. We could also add cattle, bison, and the odd yak. Many particles are likely to be sheep—beneficial, benign, and obedient to our calls to form an orderly herd. Others are cattle, mostly docile except for the occasional bull who rages when provoked. The bison are the naturally produced nanoparticles, untamed but in harmony with nature. The yaks are particles like dendrimers: hairy and a bit exotic, but valuable to those who know how to use them.

Then there are the goats: particles whose particular characteristics may spell trouble for people or wildlife if not kept under control. Goats can be tamed and very useful. (I’m a big fan of goat cheese.) Yet goats, being goats, are prone to mischief. When I was a kid, I had a Nubian goat as a pet and he was a prankster, sneaking up behind me and gently butting my backside.

The reframed question, then, is not whether nanomaterials in general are safe or dangerous but rather, how we identify the goats and either keep their bad behavior in check or ban them from the barnyard altogether.

To do that, we need to learn what makes a particular nanoparticle troublesome—a goat. Do particles that look like fibers become a problem if they are long, and therefore perhaps more difficult to remove from the lung if inhaled? Are very small particles more likely than larger ones to go places we don’t want them to go (such as into cells) or will they clump together and not get very far?

These are the kinds of questions EPA’s Nanotechnology Research Program is working to address.

Not all of us grew up on farms, but we all know the importance of separating the sheep from the goats.

About the author: Jeff Morris is National Program Director for Nanotechnology in EPA’s Office of Research and Development.

Editor's Note: The views expressed here are intended to explain EPA policy. They do not change anyone's rights or obligations. You may share this post. However, please do not change the title or the content, or remove EPA’s identity as the author. If you do make substantive changes, please do not attribute the edited title or content to EPA or the author.

EPA's official web site is Some links on this page may redirect users from the EPA website to specific content on a non-EPA, third-party site. In doing so, EPA is directing you only to the specific content referenced at the time of publication, not to any other content that may appear on the same webpage or elsewhere on the third-party site, or be added at a later date.

EPA is providing this link for informational purposes only. EPA cannot attest to the accuracy of non-EPA information provided by any third-party sites or any other linked site. EPA does not endorse any non-government websites, companies, internet applications or any policies or information expressed therein.