AbstractThe present paper shows the multidisciplinary approach used to assess the ecotoxicity of chemical munitions lying on the seabed in the Southern Adriatic Sea where aerial bombs charged with mustard agent and organoarsenic chemical warfare agents (CWAs) have been dumped.Sampling activities and laboratory analyses have been carried out on two sentinel species, the blackbelly rosefish, Helicolenus dactylopterus, and the European conger, Conger conger, collected in a CWA dumping site 35 nm from the coast of Apulia, Italy, and from a reference site. Fish were analyzed through an ecotoxicological approach, integrating chemical analysis and biological responses.Degradation products of the blister agents bis-(2-chloroethyl)sulphide, commonly known as mustard agent or yperite (also called sulfur or sulfur mustard), were found in sediment samples collected nearby aerial bombs. Although no evidence of these compounds was detected in tissues of either fish, levels of heavy metals (arsenic and mercury), potentially released by rusted chemical weapons, were significantly higher in sediment and fish from the CWA site compared to the reference site. Severe external and internal lesions were observed in fish captured in the CWA site, with congers displaying small to large skin ulcers along the body. Health assessment index (HAI) values, as well as spleen melano-macrophages centres and CYP1A ethoxyresorufin-O-deethylase activity were higher in fish from the CWA site, indicating a chronic state of illness and environment degradation.The working procedures and analyses performed during these surveys could be suitable for future biomonitoring studies in other CWA dumping sites.