1 table omitted
Since September 11, 2001, concern has increased about potential terrorist
attacks involving the use of chemical agents. In addition, recent cases involving
intentional or inadvertent contamination of food with chemicals have highlighted
the need for health-care providers and public health officials to be alert
for patients in their communities who have signs and symptoms consistent with
chemical exposures.1-3 For example, in February 2003, a Michigan
supermarket worker was charged with intentionally contaminating 200 lbs. of
meat with a nicotine-containing insecticide.3 Although intentional
release of chemical agents might be an overt event (i.e., one whose nature
reveals itself), such as release of a nerve agent in a subway or a large explosion
of a chemical container, a chemical release might instead be a covert event
(i.e., an unrecognized release in which the presence of ill persons might
be the first sign of an exposure), such as deliberate contamination of food,
water, or a consumer product. To increase the likelihood that health-care
providers will recognize a chemical-release–related illness and that
public health authorities will implement the appropriate emergency response
and public health actions, CDC identified examples of chemical-induced illness
and created appropriate guidance for health-care providers and public health
personnel. This report summarizes the epidemiologic clues and clinical signs
or patterns of illness that might suggest covert release of a chemical agent.
CDC is working to develop national surveillance capabilities for detecting
A covert release of a chemical agent might not be identified easily
for at least five reasons. First, symptoms of exposure to some chemical agents
(e.g., ricin) might be similar to those of common diseases (e.g., gastroenteritis).
Second, immediate symptoms of certain chemical exposures might be nonexistent
or mild despite the risk for long-term effects (e.g., neurocognitive impairment
from dimethyl mercury, teratogenicity from isotretinoin, or cancer from aflatoxin).
Third, exposure to contaminated food, water, or consumer products might result
in reports of illness to health-care providers over a long period and in various
locations. Fourth, persons exposed to two or more agents might have symptoms
not suggestive of any one chemical agent (i.e., a mixed clinical presentation).
Finally, health-care providers might be less familiar with clinical presentations
suggesting exposure to chemical agents than they are with illnesses that are
Epidemiologic clues that might suggest the covert release of a chemical
agent include (1) an unusual increase in the number of patients seeking care
for potential chemical-release–related illness; (2) unexplained deaths
among young or healthy persons; (3) emission of unexplained odors by patients;
(4) clusters of illness in persons who have common characteristics, such as
drinking water from the same source; (5) rapid onset of symptoms after an
exposure to a potentially contaminated medium (e.g., paresthesias and vomiting
within minutes of eating a meal); (6) unexplained death of plants, fish, or
animals (domestic or wild); and (7) a syndrome (i.e., a constellation of clinical
signs and symptoms in patients) suggesting a disease associated commonly with
a known chemical exposure (e.g., neurologic signs or pinpoint pupils in eyes
of patients with a gastroenteritis-like syndrome or acidosis in patients with
altered mental status).
Various chemical agents could be used as covert weapons, and the actual
clinical syndrome will vary depending on the type of agent, the amount and
concentration of the chemical, and the route of the exposure. However, certain
clinical presentations might be more common with a covert chemical release.
Certain syndromes are associated with groups of chemical agents with similar
toxic properties that have been used previously, have high toxicity, or are
M Patel, MD, J Schier, MD, M Belson, MD, C Rubin, DVM, P Garbe, DVM,
Div of Environmental Hazards and Health Effects; J Osterloh, MD, Div of Laboratory
Sciences, National Center for Environmental Health, CDC.
Health-care providers, public health agencies, and poison control centers
might be the first to recognize illness, treat patients, and implement the
appropriate emergency response to a chemical release. Familiarity with general
characteristics of a covert chemical release and recognition of epidemiologic
clues and syndromic presentations of chemical agent exposures could improve
recognition of these releases and might reduce further morbidity and mortality.
Public health agencies and health-care providers might render the most
appropriate, timely, and clinically relevant treatment possible by using treatment
modalities based on syndromic categories (e.g., burns, respiratory depression,
neurologic damage, and shock). Treating exposed persons by clinical syndrome
rather than by specific agent probably is the most pragmatic approach to the
treatment of illness caused by chemical exposures.
State and local health departments should educate health-care providers
to recognize unusual illnesses that might indicate release of a chemical agent.
Strategies for responding to intentional chemical releases include (1) providing
information or reminders to health-care providers and clinical laboratories;
(2) encouraging reporting of acute poisonings to local poison control centers,
which can guide patient management and facilitate notification of the proper
health agencies, and to the local or state health department; (3) initiating
surveillance for incidents that potentially involve the covert release of
a chemical agent; (4) implementing the capacity to receive and investigate
any report of such an event; (5) implementing appropriate protocols, including
potentially accessing the Laboratory Response Network for Bioterrorism, to
collect and transport specimens and to store them appropriately before laboratory
analysis; (6) reporting immediately to CDC and local law enforcement if the
results of an investigation suggest the intentional release of a chemical
agent; and (7) requesting CDC assistance when necessary.
To begin developing national surveillance capabilities for detecting
chemical-release–related illnesses, CDC is collaborating with the American
Association of Poison Control Centers to use its Toxic Exposure Surveillance
System to identify index cases, evolving patterns, or emerging clusters of
hazardous exposures. Identification of early markers for chemical releases
(e.g., characteristic symptom complexes, temporal and regional increases in
hospitalizations, or sudden increases in case frequency or severity) will
enable public health authorities to respond quickly and appropriately to an
intentional chemical release.
CDC materials for emergency and health-care personnel, including a list
of chemical agents and biologic toxins and their expected clinical syndromes,
are available at http://www.bt.cdc.gov/agent/agentlistchem.asp.
Additional information about responding to chemical attacks is available from
the U.S. Army Medical Research and Materiel Command at http://www.biomedtraining.org/progmat.htm, the U.S. Army Medical Research Institute of Chemical Defense at http://ccc.apgea.army.mil, and CDC and the Agency for Toxic Substances
and Disease Registry at http://www.atsdr.cdc.gov/mhmi.html.
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