APPENDIX A

Comparison of RfDs, ChE Inhibition and Toxicity Data for GA, GB, GD and VX

Endpoint

GA (µg/kg/day)

GB (µg/kg/day)

GD (µg/kg/day)

VX (µg/kg/day)

Ref.

RfD

0.04

0.02

0.004

0.0006

This report

Estimated no-effect level for RBC-AChE inhibition

-

1.0

-

0.24

GBd

VXa

27–33% inhibition of RBC-AChE in humans/oral dose

-

2.3 (3 days)

-

0.2-2.0

GB - Grob and Harvey, 1958;

VX-this report

RBC-AChE inhibition in humans/i.v. dose

-

-

1.5-2.0 (30%)

1.0 (50%)

DA, 1974;

Sidell and Groff, 1974

50–60% RBC-AChE inhibition in humans/oral dose

-

10

-

2.4

GB - Grob and Harvey, 1958;

VX-Sidell and Groff, 1974

50% brain ChE inhibition in vitro

1.5 × 10-8 (c)

0.3 × 10-8 (c)

-

-

Grob and Harvey, 1958

Acute toxic effects in humans/oral dose

-

20–30

-

2–4.5

GB - Thienes and Haley 1972; Grob and Harvey, 1958;

VX-Sidell and Groff, 1974

human oral LD50 (estimated)

25–50b

5–20b

5–20

3–10b

Somani et al., 1992

rat oral LD50

3700

870–1060 600

400

77–128

DA, 1974 Grob & Harvey, 1958

monkey i.v. LD50

50

20

-

6–11

DA, 1974

rat i.v. LD50

70

45–63

50

6.9–10.1

Dacre, 1984

rat i.p. LD50

490, 800

250

218

-

37–55

DA, 1974

RTECS, 1995

a Based on ratio of oral to i.v. doses (2.4 and 1.0 µg/kg, respectively) required for 50% RbC-ChE inhibition and the estimated i.v. no effect dose of 0.1 µg/kg

b Values were estimated from animal data.

c Molar concentration

d Estimated from RBC-ChE50 values for GB and VX.



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