Private contractors play a discreet but increasingly important role in the research operations of government agencies. These companies are generously paid to do everything from surveying endangered species to collecting and reviewing toxicology studies of potentially dangerous chemicals. The information is then used by research agencies or regulators to make critical decisions on public health or the environment.

The relationship can be mutually beneficial: the contractors make money, and the agencies can meet their research needs without assembling a large army of government employees. But many contractors also have private clients — and these are sometimes the same companies that their public-sector clients are trying to regulate.

On page 958 of this issue, we report on an example of the problems this can create. Last year, the US National Institute of Environmental Health Sciences (NIEHS) hired a private firm, Sciences International of Alexandria, Virginia, to help it review a chemical called bisphenol A, which may affect the endocrine system. The contractor, it turns out, also had private clients that produced bisphenol A. Environmentalists cried foul, and the NIEHS has been forced to withdraw the contract. This week, it announced that it would re-review all 20 chemicals that Sciences International had examined.

Under the original contract, a panel of external scientists was due to have the final word on the chemical's safety — and there is no evidence that the contractor was trying to manipulate them. But the potential for a conflict of interest still seems to exist. In this case, although the NIEHS required individual scientists on its advisory panel to sign statements about possible conflicts, it didn't place the same requirement on the contractor.

The NIEHS is hardly alone in this. Individual researchers are often screened quite rigorously for potential conflicts before they participate in government reviews, but contractors are rarely asked to disclose possible conflicts. Many agencies have standard warnings about conflicts in their contracts, but few have comprehensive rules about how companies should segregate their public and private work. There is also little active oversight of declarations that the contractors make, or fail to make.

In the United States, as elsewhere, reliance on contractors has been steadily rising. The time has come for agencies to re-examine how they use contractors, and how they screen for potential conflicts. Agencies should create explicit conflict-of-interest guidelines similar to those already in place for individual scientists. Contractors should be required to divulge potential problems and should be given explicit instructions on how to segregate government and private clients. Agencies should also conduct periodic audits to ensure that contractors are delivering high-quality information.

The vast majority of contractors are honest brokers, and many employ former government officials who are fully aware of what their public-sector clients need and expect. But the system seems to be open to abuse. By taking the right steps now, regulatory agencies can prevent wasteful episodes such as the one at the NIEHS. More importantly, they can ensure that they are receiving the data they need to perform their missions.