Estimates of Exposure to Chemical Threat Agent Surrogates in the United States, 2012

Abstract

The development of effective medical countermeasures against chemical threat agents is a priority. Limited civilian exposure to such agents limits our ability to develop effective countermeasures for humans. We propose to use the unintended exposure to agents similar to chemical threat agents as surrogates in order to describe the estimated national incidence of emergency department (ED) visits and hospitalizations for such agents in the U.S.National incidence estimates for 2012 were derived from the de-identified Healthcare Cost and Utilization Project (HCUP) National Inpatient Sample (NIS) dataset and the National Emergency Department Sample (NEDS). Visits for exposure to chemical threat agent surrogates were defined using International Classification of Diseases, 9th edition; Clinical Modification (ICD-9-CM) codes for specified (e.g. nitrogen oxides, chlorine, hydrocyanic acid) and unspecified irritant gas exposures as well as unintentional poisoning by organophosphates, fumigants and medicinal bromine. Frequency of visits was described.In 2012, there were ~31 million ED and 7.1 million inpatient (IP) visits in the HCUP data; when weighted these visits reflect 134 million ED and 36 million IP visits in the U.S. The estimated incidences of any toxic gas exposure were 96.7 ED and 75.8 IP per 100,000 visits. With regard to specific exposures, the estimated incidences for unspecified gas exposure were 39.8 ED/43.9 IP; for other specified gas exposure, 32.6 ED/17.6 IP; for nitrogen oxide exposure, 24.1 ED/14.9 IP; for hydrocyanic acid exposure, 5.3 ED/2.6 IP; and for chlorine exposures, 1.3 ED/0.4 IP per 100,000 visits. In general, the ED visit incidence was higher than IP visits with the exception of visits for an unspecified gas exposure although the magnitude differed by specific exposure.The incidence of ED and IP visits for chemical threat surrogates appears to be sufficient to inform prospective comparative studies of medical countermeasures to these threats.