# Comparative Study of the Presence of Heavy Metals in Edible Vegetable Oils
## 3 Challenges and Future Prospects  
As a consequence of this review, different details were extracted to clarify the trend lines of the current studies focused on the presence of heavy metals in edible vegetable oils. Likewise, it was possible to demonstrate which countries are most interested, which metals are the most studied, and which analytical techniques are chosen for the determination and quantification of these metals, even though there is no clear predominance in the latter. However, this review has also made it possible to show existing deficiencies in the investigation of the presence of these heavy metals in edible vegetable oils. These are considered as new technical challenges and new opportunities to be addressed in future researches:  
Choice of a suitable chromatographic standard. The current bibliography shows the use of different chromatographic techniques of atomic absorption or mass spectrometry, and their different couplings used for the determination of heavy metals. Each one shows advantages and disadvantages regarding its use, but there is no specific criterion regarding sensitivity and detection of these metals. This lack of criteria may be due to the diversity of previous extraction processes as well as analyte extracting agents that, in combination with the different chromatographic techniques, broaden the range of possibilities for metal determination without a specific standard. Current legislation is scarce and insufficient in relation to the presence of heavy metals in edible vegetable oils. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Oils**} & **Analytical** & **Limit of** & **Limit of** & **Results** & & \\  & **Techniques** & **(LD) 1** & **Quantification** & **(Range or Average & **Region** & **References** \\  & & **(LD) 1** & **Value) 1** & & & \\ \hline Walnut oil & ICP-OES & \(6.01\times 10^{-3}\) & 0.025 & 1.26–1.66 & Turkey & [95] \\ \hline Sweet & ICP-OES & \(6.01\times 10^{-3}\) & 0.025 & 1.06–1.60 & Turkey & [95] \\ almond oil & ICP-OES & \(6.01\times 10^{-3}\) & 0.025 & 1.24–1.47 & Turkey & [95] \\ \hline Bitter & ICP-OES & \(6.01\times 10^{-3}\) & 0.025 & 1.02–1.47 & Turkey & [95] \\ almond oil & ICP-OES & \(6.01\times 10^{-3}\) & 0.025 & 1.16–1.42 & Turkey & [95] \\ \hline Cocnut oil & ICP-OES & \(6.01\times 10^{-3}\) & 0.025 & 1.16–1.42 & Turkey & [95] \\ \hline Extra virgin & & & & \(7.00\times\) & & \\ olive oil & ICP-MS & \(2.50\times 10^{-3}\) & 0.500 & \(10^{-5}\)–4.50 & Italy & [96] \\  & & & & \(\times\)\(10^{-4}\) & & \\ \hline \hline \end{tabular} \({}^{\dagger}\) The values present the decimal places provided by the authors or, failing that, approximated to three decimal places.  
\end{table} 
Table 7: Summary of data obtained from the presence of antimony (Sb) in edible vegetable oils. Taking Cd as an example, it was observed in this review as the heavy metal most analysed. However, there is currently no specific limit for this heavy metal established in international legislation for edible vegetable oils. In this regard, the most current regulation that deals with Cd is Commission Regulation (EU) 2021/1323 in which the limits established for oil seeds are annulled when they undergo an oil extraction and refining process. As it was possible to analyse in this study, different vegetable oils, whose process prior to commercialization was refining, have exceeded the established limits of toxicity marked for other heavy metals such as Pb. This implies that, despite the high toxicity for humans derived from prolonged intake, vegetable oils with a high Cd content may be being marketed and consumed. It is necessary to mention Pb at this point, whose selected results are matching or greatly exceeding the limit established by current legislation. Therefore, the study of the presence of these metals in vegetable oils reveals the toxicity values found in the current bibliography, with the possible health conditions that these heavy metals can cause in humans, in order to be able to establish adequate toxicity thresholds.