Given the immediacy of the danger posed by many types of chemicals, systems that collect and analyze data on the patterns of illness in a population generally will be too slow to act as an event “detector” in most chemical incidents. However, in some cases, such as heavy metal poisoning or pesticide exposure in agricultural workers, clinical recognition of a pattern of clinical signs and symptoms can be key to initiating investigations that lead to incident recognition.
Table 1: Indicators of a Possible Chemical Incident (Passive Detection/Surveillance) 25
| Indicator | Description |
|---|---|
| Dead Animals, Birds, or Fish | Numerous dead animals, wild and domestic, small and large, and in the same area. |
| Lack of Insect Life | Normal insect activity (ground, air, and/or water) is missing. Numerous dead insects on the ground, water surface, and/or shoreline. |
| Different-Looking Areas | Trees, shrubs, bushes, food crops, and/or lawns that are dead, discolored, or withered (with no current drought). |
| Unexplained Odors | Smells unusual for the area, including fruity to flowery, sharp/pungent, garlic/horseradish-like, bitter almonds, or mown hay. |
| Low-Lying Clouds | Low-lying clouds or fog-like conditions that are not consistent with surrounding or current weather conditions. |
| Unusual Liquid Droplets | Numerous surfaces exhibiting oily droplets or films, including water surfaces (with no recent rain). |
| Unusual Numbers of Dying or Sick People (Mass Casualties) | Health problems including nausea, disorientation, difficulty in breathing, convulsions, localized sweating, conjunctivitis, erythema (reddening of skin), and death |
| Pattern of Casualties | Casualties will likely be distributed downwind (if indoors, by the air ventilation system) or downstream. |
| Blisters/Rashes | Numerous individuals experiencing unexplained blisters, weals, and/or rashes. |
| Illness in Confined Areas | Different casualty rates for people working indoors versus outdoors, dependent on where the agent was released. |
| Unusual Debris | Unexplained bomb/munitions-like material, especially if it contains a liquid. |
In general, human and veterinary health surveillance systems monitor for aberrations in characteristic illness and injury presence and patterns such as injuries or illnesses occurring in unusual numbers, unusually clustered, or presenting unusual symptoms. These systems rely on the collection, analysis, and interpretation of health-related data such as traditional case-report data describing injury patterns that may present a public health threat and in-person investigations conducted by public health officials. Patient syndromes caused by exposure to dangerous levels of toxins are referred to as toxidromes; toxidromes are groups of signs and symptoms used to diagnose poisoning when specific chemical/source information is unavailable (Table 2; see also Appendix B for more information on toxidromes). While recognition and interpretation of clinical signs and symptoms as well as patient accounts may provide the critical information needed for the identification of the toxic material, exposure route, and exposure location, this information may come too late to enable well-informed medical treatment or to prevent other individuals from becoming exposed. In cases where the chemical release is not effected in a single burst, these systems may play a critical role in identifying the source of an ongoing public health threat, such as a leak into a waterway, or contamination of the food supply.
Table 2: Chemical Toxidromes
| Toxidrome* | Description and Example Chemicals |
|---|---|
| Solvents, Anesthetics, or Sedatives (SAS) Toxidrome | Central nervous system depression evidenced by a decreased level of consciousness (may progress to coma), depressed respirations, and ataxia (difficulty balancing and walking). Gasoline, benzene, barbiturates |
| Anticholinergic Toxidrome | Under-stimulation of cholinergic receptors characterized by dilated pupils (mydriasis), decreased sweating, elevated temperature, and mental status changes, including characteristic hallucinations. Atropine, scopolamine, chemical warfare agents such as BZ. |
| Anticoagulant Toxidrome | Alteration of blood coagulation resulting in abnormal bleeding. Superwarfarins. |
| Cholinergic Toxidrome | Over-stimulation of cholinergic nerve receptors characterized by pinpoint pupils (miosis), seizing, wheezing, twitching, and excessive output from all secretory cells/organs ("leaking all over" – bronchial secretions, sweat, tears, saliva, vomiting, incontinence). Sarin, VX, phorate, aldicarb. |
| Convulsant Toxidrome | Central nervous system excitation leading to generalized convulsions. Hydrazine, strychnine. |
| Irritant/Corrosive Toxidrome | Immediate effects range from minor irritation of exposed skin, mucous membranes, pulmonary, and gastrointestinal (GI) tract to coughing, wheezing, respiratory distress, and more severe GI symptoms that may progress rapidly to systemic toxicity. Mustard agents, ammonia, chlorine, phosgene. |
| Knockdown/Metabolic Toxidrome | Disrupted oxygen delivery to tissues leading to decreased consciousness, with cardiac signs and symptoms, including the possibility of cardiac arrest; interference with intracellular processes leading to multiple organ dysfunction, characterized by early gastrointestinal symptoms, with subsequent hair, nail, kidney, and/or neurological abnormalities. Carbon monoxide, cyanide, arsenic, mercury, thallium. |
| Opioid Toxidrome | Opioid agonism leading to central nervous system and respiratory depression, characterized by pinpoint pupils (miosis). Heroin, oxycodone, fentanyl. |
| Stress-Response/ Sympathomimetic Toxidrome | Stress- or toxicant-induced central nervous system excitation leading to confusion, panic, and increased pulse, respiration, and blood pressure. Caffeine, nicotine, amphetamines. |
* A more detailed discussion of toxidromes is provided in Appendix B.
Syndromic surveillance systems track indicators that occur before clinical diagnosis, such as chief complaint data from urgent medical visits, over-the-counter medication purchases, and key word (e.g., “itch”, “vomit”) presence on social media platforms. Commercially available systems that monitor 911 call data (i.e., FirstWatch) can enhance syndromic surveillance and situational awareness in communities in real time, as the 911 center is often a jurisdiction’s first opportunity to recognize a toxidrome based on information from callers, social media reports, etc. Such systems will be a boon to jurisdictions as the nation progresses through implementation of Next Generation 911 (NG911). Surveillance-based incident recognition can also be supported by members of the community other than first responders and health care providers. For example, schools with teachers/staff trained to be aware of unusual behaviors, sickness, absenteeism, or comments regarding health status in their neighborhoods, can play key roles in event recognition. Mortality surveillance and unusual death reporting also play roles in chemical incident recognition. Although the information tracked by these various systems may provide the first indication that an incident has occurred, the timeliness of the information provided varies based on the data sources used and how they are analyzed. In some cases, the information is very current, whereas others have data that are weeks old. Syndromic surveillance works best when all involved are aware, alert, and reporting activities in their areas.
Unfortunately, many chemical injuries start with vague symptoms and require additional testing to definitively determine the cause. Laboratory results that conclusively identify the chemical may not be available for days, and diagnostic and screening methods for particular chemical substances may not be attainable.
One example of a worker health surveillance program is the close monitoring of pesticide exposures in the agricultural sector by NIOSH via the Sentinel Event Notification System for Occupational Risk (SENSOR)-Pesticides program. This program monitors trends in pesticide-related illnesses and injuries and is therefore useful for identifying emerging pesticide-related problems. Currently, 13 states participate in the program; these states require physicians to report confirmed and suspected cases of pesticide-related illness and injury to state health authorities. Besides identifying, classifying, and tabulating pesticide poisoning cases, states periodically perform in-depth investigations of pesticide-related events and develop interventions aimed at particular industries or pesticide hazards. Although this system is useful for identifying chronic exposures, it does not collect data on a timescale useful for guiding the response to an emergent event.
Due to the immediate need to limit ongoing exposures in chemical incidents, recognition of chemical intoxicant-specific syndromic symptom patterns (toxidromes, see Table 2) therefore should be incorporated into all components of the emergency response system, starting with training and educational programs. The ability for first responders to quickly recognize the signs and symptoms of chemical intoxication should decrease alert and assessment time even in the absence of chemical identification, thereby increasing response efficiency and potentially saving lives.
The USDA’s Animal and Plant Health Inspection Service (APHIS) Veterinary Services (VS) National Animal Health Surveillance System (NAHSS) provides the tools necessary to recognize the presence of chemical substances that could affect animal health.26,27 For scenarios in which livestock are exposed to a hazardous material, veterinary surveillance systems such as this may be the first to recognize that an incident has occurred. In such cases, communication between veterinary and public health communities is essential for chemical incident recognition. However, this communication is likely to be delayed, as it will take time for veterinary diagnostic and reporting chains to meet requirements for providing notification to public health officials. For example, if the veterinarian called in by the livestock producer cannot identify the chemical substance, they will require assistance from a state veterinarian and/or order toxicological screening tests. The state veterinarian would then report the incident to the USDA and other authorities. Again, the timeliness of data collected by veterinary surveillance systems and any forthcoming communication with public health officials varies and is in general unlikely to be fast enough to prevent further harm to human and animal health.
Footnotes
25. U.S. Department of Agriculture. (2020, June 2). Animal Health Surveillance in the United States. Animal and Plant Health Inspection Service Veterinary Services.
26. U.S. Department of Agriculture. (2018, November). United States National Animal Health Surveillance System: 2017 Surveillance Activity Report. Animal and Plant Health, Inspection Service, Veterinary Services.
27. Federal Emergency Management Agency. (2018, June). Resource Typing Definition for Response Environmental Response/Health and Safety Hazardous Materials Response Team. FEMA-508-v20170717.