title: Prevalence of radioactive signals from surveillance of an emergency department.
abstract: BACKGROUND
  Since the 11 September 2001 terrorist attacks in the United States, concerns have been raised regarding the threat of a radiological terrorist weapon. Although the probability of the employment of a nuclear device is remote, the potential of a radiological dispersal device (RDD) or "dirty bomb" is of concern. While it is unlikely that such a device would produce massive numbers of casualties, it is far more likely that it would result in public panic and perhaps even disable the local healthcare system. The utility of surveillance with radiation detectors in the healthcare setting has not been fully evaluated.
  
  
  OBJECTIVE
  The objective of this study was to characterize the prevalence of radioactive sources entering an urban emergency department (ED).
  
  
  METHODS
  A retrospective review of data obtained from a radiation detector positioned to detect radioactive people entering an ED of an urban academic hospital that serves 45,000 patients/year was performed. Graphical outputs of radioactivity were recorded in Microsoft Excel (Microsoft, Redmond, WA, US) spreadsheets in microREM/hour. Data were collected continuously from 22 December 2003 to 22 January 2004. An event was defined as any elevation in radiation levels >95% confidence interval from the mean level of background radiation over 72 hours (h).
  
  
  RESULTS
  A total of 215 events were observed over a 28-day period, with a mean value of 7.7 events/day, and a maximum of 15 events/day. During the 28-day period, the baseline mean level of background radiation was 2-4 microREM/h. Readings ranged from 2,148.28-17,292.25 microREM/h with a maximum sustained detector exposure of 684.37 microREM. Distinct signal patterns were seen at both detectors including tonic, phasic, dual, and short duration spikes.
  
  
  CONCLUSIONS
  The number of radioactive signals detected from persons entering the ED was much higher than expected. While the vast majority of these signals pose no health threat, they may make routine screening for a radiological terrorist event difficult. Further study is needed to determine this correlation.
authors.affiliation: Department of Emergency Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Guyette
authors.forename: Joe
authors.initials: J
authors.lastname: Suyama
authors.forename: Jerry
authors.initials: J
authors.lastname: Rosen
authors.forename: Michael
authors.initials: M
authors.lastname: Allswede
mesh_terms: D000398:Air Pollution, Radioactive / Q000032:analysis*; D004636:Emergency Service, Hospital; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D012189:Retrospective Studies; D014481:United States