Organochlorine compounds in Patella spp from the Canary Islands (Spain). Distribution of DDTs. Potential sources of exposure

At present, Canary Islands archipelago is not part of the OSPAR Convention area (the Convention for the Protection of the marine Environment of the North-East Atlantic), but it is expected that EU Marine Strategy Framework Directive will recommend its inclusion soon. Moreover, there are very few research studies on marine bioindicators of organochlorine compound contamination in this area. Therefore, in 2012 a study was carried out to determine the spatial distribution of PCBs (polychlorinated biphenyls) and DDT (dichlorodiphenyltrichloroethane) in limpets (Patella spp) from the seven major islands of the Canary Archipelago. Limpets were chosen since they are good indicators of pollution, are easily found on all islands and valued for human consumption. These organochlorine compounds are characterized by their toxicity and persistence. Due to their lipophilicity, stability and persistence, they tend to accumulate up the food chain (biomagnification). Their release into the environment is mainly unintentional and related to human activity. The atmospheric transport is the main pathway for the spread of these compounds, so they can be found far from their source of emission. Concentrations of 7 PCBs congeners (IUPAC nº 28, 52, 101, 118, 138, 153 and 180) and DDTs (p,p’ DDT, p,p’ DDE, p,p’ DDD and o,p’ DDD) were analysed by gas chromatography-electron capture detector (GC-ECD) with capillary column. The used procedures are systematically validated and controlled by the use of Certified Reference Materials (CRMs) and by participating in intercalibration exercises promoted by international institutions. The results obtained with limpets (Patella spp) from the Canary Islands, present a pattern of pollution characterized by higher levels of DDTs with respect to PCBs, which have very little presence, in contrast to the northwestern Iberian Peninsula area (Galicia-Cant´abrico) where PCBs are the majority. In all the Islands, the major metabolite is the DDE, presenting the highest concentrations in Lanzarote (18 g/kg p.h.), Fuerteventura (10 g/kg p.h.) and Tenerife (8 g/kg p.h.). Presence of DDE in Tenerife can be attributed, among other factors, to being one of the most populated islands and to the high growth of agriculture during the last decades. The concentrations in Lanzarote and Fuerteventura, can be influenced by its proximity to the African continent, where DDTs are still in use today