# Organochlorines Accumulation in Caged Mussels
## 4 Discussion
### OCs--Accumulation Pattern  
Unlike DDTs (Kastela Bay 93.1% and Mali Ston Bay 95.3%), the contribution of HCB, lindane, heptachlor and aldrin in Kastela Bay is rather low, showing mean values for 1-year-old mussels of 1.63%-2.13% and 2-year-old musselsof 1.93%-1.89% (Figure 5). With regard to _p,p'_-DDTs compound accumulation patterns in mussels in Kastela Bay, their average contribution decreases equally in the order of DDE(56.0%) > DDD(24.4%) > DDT(19.6%) for 1- and 2-year-old mussels. No significant difference was observed in relation to mussel age. For Mali Ston Bay, the average contribution of DDE:DDD:DDT was 59.7%:24%:20.3% and 61%:20.1%:18.9% for 1- and 2-year-old mussels, respectively (Figure 5). The prevailed contribution of _p,p'_-DDE is attributed to its high chemical stability, hydrophobia, long half-life, and persistence in abiotic and biotic aquatic compartments [35]. Similar findings were reported by [PERSON] et al. [36], but a difference was found in mussels from Korea (29.6%:43%:27.5%) [37].  
Predominantly accumulated congeners in Kastela Bay and Mali Ston Bay were CB 153 and CB 138, due to their ability to attach to particulate matter. In Kastela Bay, the contribution of the hexachlorinated biphenyls CB 153 was 36.69% of the total in 1-year-old mussels and 36.74% of the total in 2-year-old mussels, and CB 138 was 32.23% of the total in 1-year-old mussels and 34.47% of the total in 2-year-old mussels. The significant prevalence of CBs 138 and 153 has been reported in several bivalves [12; 27; 38].  
Increased contribution of low chlorinated congeners (CB 28 and CB 52) was observed in mussels from the reference location compared to Kastela Bay (Figure 5). Similar findings were observed by [PERSON] et al. [27] and [PERSON] et al. [38].  
No significant differences were observed in CB accumulation profiles between young and old mussels. However, CB congeners with more than five chlorine atoms and parachlorine atoms, such as CB 118, CB 138, CB 153, and CB 180, have higher metabolic resistance and their elimination from the organism is much slower, resulting in stronger bioaccumulation than low chlorinated congeners [39]. The predominant groups of PCB congeners accumulated in mussels, grouped by the number of chlorine atoms, were hexa-, followed by penta-, tetra-, tri-, hepta-, and octachlorinated biphenyls for the reference station and penta-, hepta-, tetra-, tri-, and octachlorinated biphenyls in Kastela Bay, respectively. With regard to mussel age, no significant differences in homolog CB accumulation patterns were evident between 1- and 2-year-old mussels (Figure 5). Our findings are in accordance with [PERSON] et al. [4].  
Regarding human exposure to contaminants, concentrations of chlorinated pesticides and six indicator PCBs expressed on a wet weight basis are much lower than the maximum concentrations set by the European legislation [40; 41]. The following values of maximum concentrations of chlorinated pesticides and six indicator PCBs (in ng g\({}^{-1}\) wet weight) in the samples from Mali Ston Bay and Kastela Bay were determined: HCB\({}^{\text{a}}\) 0.06; lindane\({}^{\text{a}}\) 0.07; heptachlor\({}^{\text{a}}\) 0.08; aldrin\({}^{\text{a}}\) 0.06; DDT\({}_{3}\) 1.71, and 6 PCBs 24.1. The corresponding maximum residue levels (MRL, ng g\({}^{-1}\)) are HCB\({}^{\text{a}}\) 20; lindane\({}^{\text{a}}\) 2; heptachlor\({}^{\text{a}}\) 20; aldrin\({}^{\text{a}}\) 20; DDT\({}_{3}\) 100, and 6 PCBs 75. A comparison of chlorinated pesticides such as HCB, lindane, heptachlor, aldrin, DDTs, and PCBs by data obtained in this study for Mali Ston and Kastela Bay, with levels found in mussels _Mytilus galloprovincialis_ sampled from other regions, showed values usually found in low (Mali Ston Bay) to moderately contaminated (Kastela Bay) areas of the Mediterranean Sea [26; 38].