Home LMS THMG169 – Fourth Generation Chemical Agents, Part I

THMG169 – Fourth Generation Chemical Agents, Part I


In this episode, Bob and Mike answer questions about the new generation of chemical warfare agents. This discussion was prompted by a recent joint government publication.

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Complete Show Notes

4:45 A Little Bit of Background

  • As of 1/29/19, the United States government released a document about what they’re referring to as “fourth generation agents”
  • Joint publication from the DOD, EPA, ASPR, CDC, NIOSH, and National Guard

8:30 What is a Fourth Generation Agent (FGA)?

  • Signs and symptoms are exactly the same as “old” chemical warfare agents
  • When used in England, they’re referred to as “A-Series” or “Novichok”
  • FGAs have lower vapor pressures and lower lethal doses than VX
  • Lasts in the atmosphere 5-6 times longer than VX, too
  • Government didn’t provide a specific dosage, so we did our own research and used VX to make an estimate:
    • Estimated lethal skin exposure is 10 mg (0.00035 oz.) for a 155 lb man
    • Estimated lethal concentration time (LCt50) is 30-50 mg·min/m3

12:45 Pathophysiology of FGAs

  • FGAs have the same pathophysiology as other nerve agents
  • According to the document, “medical providers need to keep in mind that those variables (i.e. the specific agent, including concentration and duration of exposure; physical state of the agent in the environment; routes of exposure; time from exposure to treatment; and underlying medical conditions) determine toxicity, clinical manifestations, and effectiveness of medical interventions. Therefore, a spectrum of clinical effects among the nerve agents and among individual patients is expected.”
    • This passage bothered Bob and Mike – they wondered whether this is true for all agents (or just FGAs) and which variables change treatment
  • “In general, the latent period between dermal exposure and symptom onset may be longer for FGA than for VX and can be up to three days. Inhalation, ingestion, or large dermal exposures will have shorter latent periods.”
    • This means we shouldn’t expect results right away, and also gives lots of time for cross-contamination
  • According to the document, FGAs stay around on surfaces for months – this means we can’t decontaminate with fans

21:05 Human Exposure Cases

  • There have only been a few cases of human exposure reported – document makes comparisons between what’s been seen in the lab vs. what’s been seen on the street
  • Symptoms include:
    • “Bronchoconstriction has been a prominent feature of FGA toxicity in animal studies, but has not been observed in the very limited number of human cases. If it occurs, bronchoconstriction may be difficult to manage clinically.”
    • “Seizure activity has been a prominent feature of FGA toxicity in animal studies, but has not been observed in the very limited number of human cases.”
    • “Patients may have some – but not all – of these signs and symptoms. In some cases, miois (pinpoint pupils) and bronchospasm (severe bronchoconstriction) may not be prominent or may even be absent.”

23:50 Protecting Ourselves from Exposure

  • Take all of the normal precautions when protecting yourself from FGAs, but keep the following in mind:
    • “Handle blood and body fluids with extra caution as though they are contaminated with FGA. Limited data are available on the risks, but there are concerns that FGA can persist in body fluids, posing a potential hazard to personnel.”
    • Keep in mind that signs and symptoms can take up to three days to present themselves, so keep that in mind if you ever have to respond to a FGA

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