Module 3 Toxicity

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Module 3Toxicity
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Toxicity Measures

• The term Ct is used to describe an estimate of
  dose. C represents the concentration of the
  substance (as vapor or aerosol) in air (usually
  expressed as mg/m3 ) and t represents time
  (usually expressed in minutes).
• The t value is the product of the concentration
  (C) to which an organism is exposed multiplied by
  the time(t) during which it remains exposed to
  that concentration. Ct does not express the
  amount retained within an organism thus, it is
  not an inhalational dose.
• The term LCt50 is often used to denote the vapor
  or aerosol exposure (Ct) necessary to cause death
  in 50 of the population exposed (L denotes
  lethal, and 50 denotes 50 of the population).
• The term LD50 is used to denote the dose that is
  lethal for 50 of the population exposed by other
  routes of exposure (liquid,solid).

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Toxicity Values for Nerve Agents

• LD50 of VX is 5 milligrams/70-kg human (liquid on
  skin)
• LCt50 of VX is 15 milligrams-min/m3 (vapor
  inhalation)
• LD50 of GB is 1.7 grams/70-kg human (liquid on
  skin)
• LCt50 of GB is 35 milligrams-min/m3 (vapor
  inhalation)
• 1 kilogram (kg) 2.2046 pounds

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VX Liquid Exposure

• An potentially lethal exposure is a drop about
  the size of the Lincoln Statue in the center of
  the Lincoln Memorial on the back of a penny

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Toxicity Values for Sulfur Mustard Agent

• LD50 (liquid on skin) is 1.4g/70-kg human
• Between 4 and 32 micrograms/70-kg man can cause
  blistering
• LCt50 is 1000 mg-min/m3

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Acute Exposure Guidelines (AEGLs)
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AEGLs

• Concentration of a chemical in air, above which,
  specific categories of health effects could begin
  to occur in an unprotected civilian population.
• AEGLs are expressed as the concentration of a
  chemical an individual is exposed to over a given
  period of time.

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AEGLs

• Represent threshold exposure limits
• Three levels - 1, 2, and 3
• Based on 5 reference times from 10 minutes to 8
  hours
• Used to trigger emergency actions including event
  notification and protective action decisions

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Five Exposure Periods

• 10 minutes
• 30 minutes
• 1 hour
• 4 hours
• 8 hours

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AEGL-1

• AEGL-1 is the airborne concentration (expressed
  as ppm or mg/m3) of a substance at or above which
  it is predicted that the general population,
  including susceptible individuals, could
  experience notable discomfort, irritation, or
  certain subclinical, non-sensory effects.
  However, the effects are not disabling and are
  transient and reversible upon cessation or
  exposure
• May trigger a precautionary alert

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AEGL-2

• AEGL-2 is the airborne concentration (expressed
  as ppm or mg/m3) of a substance at or above which
  it is predicted that the general population,
  including susceptible individuals, could
  experience irreversible or other serious,
  long-lasting effects or impaired ability to
  escape.
• Exposed people need to evacuate or
  shelter-in-place above AEGL-2. May become a mass
  casualty event.

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AEGL-3

• AEGL-3 is the airborne concentration (expressed
  as ppm or mg/m3) of a substance at or above which
  it is predicted that the general population,
  including susceptible individuals, could
  experience life-threatening effects or death.
• People must not be exposed to these levels. This
  is likely a mass casualty event.

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AEGL Summary
Severe adverse effects
Above AEGL-3 effects become increasingly severe
and could be fatal.
AEGL-3
Significant adverse effects
Above AEGL-2 effects become increasingly more
significant, and may cause impairment, be longer
lasting, or permanent.
AEGL-2
No significant adverse effects
Above AEGL-1 there may be some discomfort, odor,
or irritation. Effects, if any, are not impairing
and only temporary.
AEGL-1
No adverse effects
No Exposure
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AEGL Values for GB
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Comparison of AEGLs CTs for HD and GB