T8 AM Ecological Fate and Effects of Explosives and Related Compounds
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 337-338

(GON-1117-839355) Neurotoxicity of CL-20 in earthworm Eisenia fetida.

Gong, Ping¹, Inouye, L², Perkins, E², ¹ Analytical Services, Inc, Vicksburg, MS, USA² US Army ERDC, Vicksburg, MS, USA

ABSTRACT- Recent studies suggest that CL-20, a new energetic compound in contention for replacing current explosives, or its transformation products, have unforeseen negative impacts on terrestrial and aquatic ecosystems. CL-20 has been found highly toxic to soil invertebrates with EC20 values as low as 0.02 mg/kg soil. However, little is known about its toxicological mechanism. Based on previous observations of neurotoxicological symptoms, we hypothesized that CL-20 or its transformation products acted as neurotoxins to earthworm central nervous system. A noninvasive electrophysiological technique was employed to (1) assess the impacts of acute sublethal exposures on impulse conduction in the worms medial (MGF) and lateral (LGF) giant nerve fiber pathways, (2) to detect whether such effects were generalized or localized within various body regions, and (3) to evaluate the reversibility of neurotoxic effects. Earthworms (E. fetida) were exposed to 0.2 to 4 microgram/cm2 of CL-20 for one day on moistened filter paper. Conduction velocities of MGF and LGF were recorded on a digital oscilloscope before and after exposure. Results showed that even at the lowest exposure level worms exhibited physiological impacts such as retardation, stiffness and body shrink. There was no significant differentiation between different body regions, suggesting that neurotoxic impacts of CL-20 were generalized. Both MGF and LGF conduction velocities were negatively correlated with increasing doses of CL-20 (do you have a value for this correlation?). However, such neurotoxic effects were alleviated or even eliminated in 1-3 days after exposed worms were transferred to uncontaminated environment, depending on exposure doses. This indicates that the neurotoxicity is reversible after short-term exposure. However, the reversibility of chronic exposure needs to be further investigated.

Key words: neurotoxicity, CL-20 (hexanitrohexaazaisowurtzitane), earthworm Eisenia fetida, noninvasive electrophysiological technique