Mercury and selenium in fish and shellfish: Occurrence, bioaccessibility and uptake by Caco-2 cells

► Hg and Se contents, bioaccessibility and Caco-2 cell uptake in seafood were studied. ► Swordfish is the only sample that exceeds the permitted limits of Hg. ► Hg and Se bioaccessibility varies greatly, 35-106% and 17-125%, respectively. ► In Caco-2, Hg and Se transport from the swordfish bioaccessible fraction is <14%. ► Cellular retention of Hg from swordfish bioaccessible fraction is very high (>49%).