Uptake of hexanitrohexaazaisowurtzitane (CL-20) by the earthworm Eisenia fetida through dermal contact

The explosive compound hexanitrohexaazaisowurtzitane (CL-20) has been shown to cause both lethal and sublethal (reproductive and neurotoxic) effects in exposed oligochaetes. However, whether worms take up CL-20 and how much CL-20 enters worm bodies leading to toxicity (e.g., lethality) remain to be determined. In the present study, we used high performance liquid chromatography (HPLC) and radiolabeled tracer methods to investigate the CL-20 uptake in the whole worm body after contact exposures. Worms (Eisenia fetida) were exposed to filter paper spiked with non-radioactive or [U-14C]-labeled CL-20 for 1–3 d. The radiolabeled tracer method allowed us to detect the parent compound and transformation products in worms exposed to as low as 0.04 μg CL-20 cm− 2 of filter paper. The HPLC method without radiolabeled tracer was far less sensitive with a detection limit of 2.17 μg CL-20 cm− 2. Using the radiolabeled tracer, we were able to demonstrate that the worm body concentration linearly correlated to the filter paper concentration ≤ 0.34 μg cm− 2 (r = 0.94) if no breakdown products are assumed. At higher concentrations, the body concentration increased slowly and saturated at around 11 μg g− 1 dry mass resulting in an estimated lethal critical body burden of 10–15 μg CL-20 g− 1 dry mass. These findings demonstrate that CL-20 or potential transformation products are taken into the earthworm body through dermal contact. This information should prove valuable in assessing the bioaccumulation potential and ecological risks of CL-20.