Traces of some of the nearly 80,000 chemical substances used by U.S. industry end up in the air, in consumer products and in drinking water. Yet the U.S. Environmental Protection Agency has only evaluated the safety of a few hundred of them. Last year the EPA pledged to speed and streamline its evaluation process. But some scientists argue that the agency needs to do more, including update the science behind its assessment approaches and incorporate data from other agencies.

One reason the EPA's chemical risk assessments are slow is that its scientists “tend to … keep trying to improve [an assessment] without thinking how much is too much,” says Adam Finkel, executive director of the Penn Program on Regulation at the University of Pennsylvania. But “delay always costs society.” The agency could speed its process by incorporating data from other organizations, says George Gray of George Washington University, a former EPA staffer who recently co-wrote an editorial on the topic in Nature.

Incorporating personnel from other organizations may help as well. In 2011 eight professional scientific societies, including the Endocrine Society, asked the EPA to put their scientists on regulatory panels to help improve accuracy. Among other things, the EPA has been using outdated science to study the effects of low doses of hormonelike chemicals such as bisphenol A, the societies argue.

Ultimately, Gray and his co-authors say, it makes sense for the EPA to embrace uncertainty. Instead of devising a single threshold value distinguishing safe from unsafe exposure, the agency should consider providing a range of values. “We should describe the risk as well as we can—given what we have—and get it out in the hands of people who have to make decisions that can affect their nation's health,” he says.