QSAR makes use of statistical and mathematical techniques to quantitatively connect a biological characteristic to molecular characteristics (such as structural features or physicochemical qualities), which are numerically stored inside so-called molecular descriptors. QSAR has become more significant in international decision-making frameworks , and the European REACH legislation promotes its use for prioritising, data gap filling, and the rationalisation of animal testing. The vast majority of BCF QSAR models are constructed using octanol/water partition coefficient (K ow ) or other descriptors that are quite comparable to them . In practice, bioconcentration happens predominantly as a thermodynamically driven partitioning between water and the lipid phases of organisms, as shown by K ow . However, other processes, such as metabolism and excretion, as well as specific interactions with tissues other than lipids, can greatly contribute to the apparent quantities that are present within organisms . Chemicals that can be transformed into hydrophilic molecules may be eliminated more quickly, and as a result, their BCF values are lower than what is predicted by K ow . However, substances that form specific connections with non-lipid tissues can have a bigger BCF than one would anticipate. One example of this is methylmercuric chloride, which has a low log K ow but a very high BCF (up to 1,000,000 in fish) as a result of its linkage with protein sulfhydryl groups. Other examples of this type of compound include benzene, which has a low log K ow but a very high BCF . In a similar way, K ow -based QSAR models, which vary in how complex they are, can either underestimate or overestimate the true BCF .