## 4 Discussion
### Potentially Toxic Metals  
Table 2 shows the content of potentially toxic metals, namely, Pb, Cd, Cu, Cu, Ni, Cr, Mn, and Co, in the eight types of edible vegetable oils. According to international requirements, the maximum level of heavy metal content in oils is 0.1 mg/kg for Cu and Pb. There is currently no legislation for Cd [57; 58]. The Food and Agriculture Organization (FAO) and the World Health Organization (WHO) have established a limit for heavy metal intake based on body weight [59]. For a 60 kg adult, the tolerable daily intakes for Cu and Pb are 3 mg and 214 mg/g [59]. Based on the results of this study, it was found that in sunflower oil, the content of metals varied in the following order: Cu > Pb > Mn > Cr = Cd = Co > Ni; in grapeseed oil, this was Cu > Mn > Co > Ni > Pb > Cd > Cr; in extra virgin olive oil, this was Cr > Pb > Ni > Cu = Mn > Co > Cd; and in organic extra virgin olive oil, this was Cu > Pb > Mn > Co = Ni > Cr > Cd. In walnut and rapeseed oil, the concentration of metals varied as follows: Cu > Pb > Mn > Co > Cr > Cd > Ni, and Cu > Mn > Pb > Co > Cr > Ni > Cd, respectively. In the case of rice oils and blends (linseed, rapeseed, and pumpkin), the variation was as follows: Pb > Cu > Cr > Mn > Ni > Cd > Co, and Cu > Pb > Cr > Mn > Co > Ni > Cd, respectively. From these observations, it can be concluded that in six of the eight types of studied oils, the most abundant metal was Cu, except for rice oil, in which Pb predominated, and extra virgin olive oil, in which the most abundant metal was Cr. Cd was the least abundant element in the studied samples. Generally, the concentrations of the determined metals are at an acceptable level in the oil samples, exceeding the permissible value in a few cases, such as Cu in the blend oil and organic extra virgin olive oil, and Pb in rice oil, with organic extra virgin olive oil having Pb concentration at a permissible value of 0.1 g/kg [59]. Some of these metals can cause adverse effects on the oxidative stability of oils if they are present [60]. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Oil** & **Country** & **AI (\%Oleic Acid)** & **MC (\%)** & **PV (meq/\(\alpha_{\text{z}}\)/kg)** & **RI** & **IV (g/100 g)** & **SV (mg/\(\alpha\)KOH/g)** & **TPC** \\ \hline \multirow{4}{*}{Sunflower} & Turkey & 0.81 & & 4.19 & & 102.02 & & [45] \\  & Russia & 1.40 & & 3.50 & & & [46] \\  & Romania & 0.10–0.62 & 0.04 & 3.65–10.50 & & 122.00–123.00 & 185.00–204.80 & [17; 47; 48] \\  & India & & & 10.63 & 1.461 & & [56] \\ \hline \multirow{4}{*}{Grapeseed} & Romania & & & & 129.50 & 184.00 & & [47] \\ \hline \multirow{4}{*}{Olive} & Turkey & 0.82 & & 6.39 & & 80.03 & & [45] \\  & Bangladesh & 4.20 & 0.47 & 12.43 & & 78.38 & 185.80 & [49] \\  & Romania & 0.80 & 0.50 & & 89.00 & 191.00 & [1] \\  & Spain & 0.48 & 0.15 & 5.31 & & & 20.90 & [54; 55] \\  & Marco & 1.46-240 & & 3.50–7.00 & & 89.50 & & 21.67 & [50; 51] \\  & Libya & 2.19 & & 7.81 & 1.4686 & 81.14 & & [52] \\ \hline \multirow{4}{*}{Rapeseed} & Turkey & 0.65 & & 9.46 & & 107.51 & & [45] \\  & Russia & 0.80 & & 4.50 & & & [46] \\  & Romania & 0.65 & & 11.50 & & 102.00–113.20 & 182.00–186.20 & [17; 47] \\ \hline \multirow{4}{*}{Walnut} & Romania & & & & 149.70 & 188.20 & & [47] \\  & Republic & 3.44 & 0.10 & 7.70 & 1.473 & 147.70 & 185.77 & [53] \\ \hline \multirow{2}{*}{Rice} & Bangladesh & 0.09–1.11 & 0.82–3.05 & 1.43–43 & 1.465 & 88.07–110.59 & 191.38–203.31 & [41; 49] \\ \hline \end{tabular}
\end{table} 
Table 5: Literature reports on the physicochemical contents of oils. The most possible explanation for the increased concentration of Pb is that, in urban and industrial areas, the air carries toxic substances to the surface of plants. The use of chemical pesticides and fertilizers during crop cultivation is also an explanation for such contamination [60; 61; 62]. Plant leaves can absorb heavy metals during development, transport them to the seeds, and hence, result in heavy metal contamination of oils (bioaccumulation) [12; 63; 64].