1 Module 3 Toxicity

2 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/m 3 ) 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 LCt 50 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 LD 50 is used to denote the dose that is lethal for 50% of the population exposed by other routes of exposure (liquid,solid).

3 Toxicity Values for Nerve Agents LD 50 of VX is 5 milligrams/70-kg human (liquid on skin) LCt 50 of VX is 15 milligrams-min/m 3 (vapor inhalation) LD 50 of GB is 1.7 grams/70-kg human (liquid on skin) LCt 50 of GB is 35 milligrams-min/m 3 (vapor inhalation) 1 kilogram (kg) = pounds

4 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

5 Toxicity Values for Sulfur Mustard Agent LD 50 (liquid on skin) is 1.4g/70-kg human Between 4 and 32 micrograms/70-kg man can cause blistering LCt 50 is 1000 mg-min/m 3

6 Acute Exposure Guidelines (AEGLs)

7 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.

8 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

9 Five Exposure Periods 10 minutes 30 minutes 1 hour 4 hours 8 hours

10 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

11 AEGL-2 AEGL-2 is the airborne concentration (expressed as ppm or mg/m 3 ) 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.

12 AEGL-3 AEGL-3 is the airborne concentration (expressed as ppm or mg/m 3 ) 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.

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

14 AEGL Values for GB

15 Comparison of AEGLs CTs for HD and GB