DIOXINS, FURANS AND AHH-ACTIVE PCB CONGENERS IN EGGS OF 2 GULL SPECIES FROM THE WESTERN MEDITERRANEAN

Polychlorinated biphenyls, dibenzodioxins and dibenzofurans were analy sed in eggs of a protected gull species, the Audouin's Gull (Larus aud ouinii) and compared to those of the Yellow-legged Gull (Larus cachinn ans), both breeding in the Western Mediterranean (Ebro Delta and Medes Islands, respectively). Differences in concentrations as well as in c ongener profiles reflected differences in both habitat and diet of the two species. Levels of AHH-active PCB congeners were lower in Yellow- legged Gull (0.4-1.6 mu g/g d.w) than in Audouin's Gull eggs (1.2-33.9 mu g/g d.w.). These concentrations, expressed in international toxic equivalence factors (i-TEQ/g d.w.), were on average 24 times higher in the Audouin's gull. I-TEQ levels due to dioxins were also higher in t his species by a factor of ca. 7. I-TEQ levels related to PCBs resulte d 90-230 times higher than those of dioxins and furans. Thus, AHH-indu cing PCBs might represent even higher toxicological hazards than dioxi ns and furans to some populations of seabirds. The necessity of assess ing the impact of these compounds in rare and protected species is poi nted out.