The shelves at your store are filled with items that have been enhanced by things too small to see. They are so small, in fact, that each speck would make up the same portion of a regulation soccer ball as a soccer ball would of the entire earth. Tiny particles added to sunscreen transform it from smeary white to invisible, making it more attractive (marketers hope) to sunbathers. Minute bits of silver are added to toothpaste and shampoo to kill bacteria. All sorts of things, from air fresheners to clothes to tennis rackets, feature minuscule pieces, each made up of only a few atoms or molecules, engineered for a specific purpose. As nanoparticles are added to more goods we use daily—up to 800 consumer products and counting—our bodies often absorb them, and the planet deals with what ends up in the dump or washed down the drain.

But are we sure they’re safe?

At the annual symposium of the Johns Hopkins Institute for NanoBioTechnology (INBT), held in late April, speakers from several Hopkins divisions urged toxicologists, environmental scientists, and governments to focus more on the question of safety of nanotechnology so they can begin to catch up with the burgeoning field, which now creates more than $3 billion in revenue annually for private companies.

“It’s too late for precaution,” said Ellen Silbergeld, professor of environmental health sciences at the Bloomberg School of Public Health. “Six years ago, we were in a position where we could look before we would leap. Now I wonder whether the cat is out of the bag. We have to move twice as fast now.” The problem, Silbergeld added, is that there are few hard and fast rules for research into nanoparticles’ possible toxic effects, and that so many types of them are now being made. “We haven’t prioritized our research so we can evaluate the risk of all of them,” she said.

Although scientists and engineers generally view nano-applications as safe, they worry that investigations into their long-term effects haven’t kept pace with the technology. They also aren’t sure how certain chemicals that behave differently when reduced to mere atoms might react in the body, or if they might have previously unseen effects once let loose in the environment. A handful of recent studies involving mice have found that nanoparticles could cause genetic damage. Some types of nonengineered particles that exist at the nanoscale, such as those present in welding fumes and diesel exhaust, have been shown to create health problems for humans.

The issue is further complicated by a lack of knowledge about the materials themselves. Howard Fairbrother, a professor of chemistry at the Krieger School of Arts and Sciences, said research would be better served if the field of nanotechnology kept better tabs on what exactly it produces. For example, carbon nanotubes, which make up a high percentage of all engineered nanoparticles, often contain metal particles that can cause toxicity. “Often, it’s not the carbon that causes the problem, but the contaminating metals,” Fairbrother said.

The size of the particles also represents some new angles for toxicological research, said Patrick Breysse, director of the Division of Environmental Health Engineering at the Bloomberg School. For example, particles of silica don’t invade the lungs of lifeguards because those emanating from grains of sand are too large. But much smaller particles that are created during welding and in lab experiments can lead to silicosis, a debilitating disease, because they are tiny enough to embed in lungs. EPA studies often don’t adequately measure the tiniest of particles. Breysse advocates more use of existing technologies that measure particles at the nanoscale, and the development of new ones.

Last year, the Canadian government enacted a law requiring manufacturers of nanomaterials to register their work and disclose potential toxins. In the United States, only Berkeley, California, has passed similar legislation, and federal oversight is split up between several agencies that haven’t coordinated their efforts. As bioengineers develop more and more nanomaterials, the need for oversight will be even more intense, concluded Ronald White, an associate scientist in the Bloomberg School’s Department of Health Policy and Management. “If you think things are scary now, as we deal with passive nanostructures, take a look down the pike when active nanostructures that are designed to do specific things in the body come to be,” said White. “There’s definitely a need for regulation of nanoparticles. The question is: How do we get there?”