Scientists, businesses and politicians are growing increasingly interested in the safety of nanomaterials. Panel after panel has been convened to discuss whether substances engineered on the nanometre scale pose different environmental, health and safety risks from those engineered on larger scales. Report after report has called for greater scrutiny of any possible effects (see Nature 444, 267–269; 2006).

So it should come as no surprise that US regulators have finally agreed on their first ruling concerning nanoparticles. In a decision that came to light last week, the Environmental Protection Agency (EPA) plans to regulate products marketed as antimicrobial because they contain nano-sized particles of silver. In essence, companies will no longer be able to sell things such as odour-eating silver shoe inserts without being able to prove — in a manner yet to be defined — that the particles will not harm the environment.

The ruling stems from a challenge over a Samsung washing machine, which is claimed to release silver ions to sterilize clothes. Environmentalists challenged an EPA decision last year that the washing machine was a 'device' and so did not need to be regulated. (Typically, devices that release pesticides are not regulated, but the pesticides are.) The agency reconsidered and now says the silver nanoparticles can be considered to be a pesticide, and so need to be regulated.

The Environmental Protection Agency's decision is the first, necessary step along what promises to be a lengthy road.

Companies that make and market nanoproducts have yet to see how environmental concerns may affect their business plans (see Nature 443, 137; 2006). But the EPA is, in this case, taking a step in the right direction. Clearly, many details remain to be worked out; the new ruling, for instance, leaves a significant loophole, as companies will be able to stop marketing their devices as antimicrobial and continue to sell them without regulation. But despite the criticism often hurled at them, regulators (at least in the United States and Europe) have a reasonably good track record of evolving their rules to protect the public interest.

The impact of all this on nanotechnology researchers and businesses will depend on how regulatory agencies cope with the dizzying array of products that will be produced under the wide rubric of 'nanotechnology'. If regulation is to be fair and effective, agencies will have to work closely together. Nanosilver, for instance, falls under the purview of the EPA when the particles could be released into the environment, such as in waste water from a washing machine. But it becomes the responsibility of the Food and Drug Administration for medical applications, such as when nano-sized silver particles are used on bandages to kill germs. Regulators from various agencies routinely attend nano-safety seminars and background briefings together; soon we will discover how much they have learned.

The scientific community, for its part, plays an important role in the development of technologies, including nanotechnology. But that doesn't mean it supports every application. Like everyone else, scientists want to see intelligent regulation. They should not interpret the EPA decision as negative: it is the first, necessary step along what promises to be a lengthy road. Regulators cannot begin to work their way through different health and safety risks until the first rules are on the table. Now they are.