Radiological and nuclear disasters are infrequent, but when they occur, they result in large and demonstrable health burdens. Several scenarios can result in the public's exposure to radiation. For example, radiation sources used in health care or other industries can be lost or misused. Incidents in the nuclear power industry, such as those at Chernobyl and Three Mile Island, require significant public health response. In addition, radiological terrorism can involve the use of a radiological dispersal device (RDD) or an improvised nuclear device (IND). State and local health agencies are expected to perform essential public health functions in response to any of these emergencies. Recent events illustrate that the public health sector will be essential in a radiological or nuclear response. For example, in August 2004, the day before the Republican National Convention, the New York City Department of Health and Mental Health (DOHMH) responded to a radiation incident at a mid-town Manhattan post office. A radiation source failed to retract into its protective shielding, resulting in dangerously high radiation levels near the radiation source. Police and fire departments evacuated the building and closed off nearby streets. The DOHMH response included conducting extensive environmental surveys outside and throughout the building, assisting with shielding the source, conducting press conferences, providing approximately 2,000 copies of fact sheets to residents in nearby buildings, and conducting dose estimates for the contractor and postal service employees. It took over 24 hours to remove the radiation source safely. The public's maximal risk for exposure was less than that received from a single chest radiograph because of their distance from the radiation source.