This study was undertaken to assess the toxicological risks from sodium accumulation in a vermifiltration wastewater treatment system to the key worm species, Eisenia fetida. The Study found that sodium chloride (NaCl) is the more toxic of the common sodium Salts found in wastewater to the worms. The research further found that the worms have ail ability to detoxify NaCl although reproduction will be impaired if the worms are exposed to moderate concentrations of NaCl for a long period of time. The actual risk from NaCl toxicity in the vermifiltration process was low however. The low risk was due to the low solid-water partitioning constant of NaCl, which led to a very low predicted environmental concentration (PEC) for NaCl (c) 2009 Elsevier Ltd. All rights reserved.