washington

The US National Institutes of Health (NIH) are not to be stripped of their licence to use nuclear materials, despite the efforts of a pregnant scientist who was contaminated with radioactive phosphorus while working there (see Nature 377, 568; 1995).

The Nuclear Regulatory Commission (NRC) has denied a petition from Maryann Wenli Ma and her husband, Bill Wenling Zheng, that NIH's licence to use nuclear materials be revoked or suspended.

After the discovery of Ma's exposure in June 1995, it was found that 26 others — including Zheng — had been exposed to radiation from a contaminated water cooler at NIH (but not through the consumption of Chinese food that had been left in a refrigerator, as originally thought).

Investigators from the NRC, working jointly with the Federal Bureau of Investigation and the NIH police, concluded that the co ntamination was “deliberate”, but could not identify the perpetrator.

The NRC said in a statement that, normally, “radiation overexposures of this sort would be subject to significant enforcement action”. But it added that it would exercise discretion in this case because there was no evidence that NIH had contributed directly or indirectly to the deliberate misuse of licensed material.

Also, NIH “could not reasonably have foreseen” malicious misuse of materials by an employee, and had cooperated fully in the investigation.

The NRC did say, however, that NIH had violated several requirements for the security and control of radioactive materials, but that the agency had since made “significant efforts to improve its control”.

David Marshall, a lawyer representing Ma and Zheng, says that the decision “allows the [NIH] to continue to put its employees and the public at risk with impunity”. The lawyers are considering filing a civil suit for damages in the federal court. Although Ma's son David was born apparently healthy, “Dr Ma and her child will live for years with the dangerous and uncertain effects of radiation poisoning”, says Marshall.

The NIH has issued a statement welcoming the NRC conclusion. “It is particularly significant,” it said, that the NRC found the contamination “was not the result of faulty compliance with security requirements for radioactive materials”.

But the statement also pointed out that NIH had nevertheless “consistently tightened its standards for the security and use of such materials”.