# Human Exposure to Toxic Metals (Cd, Pb, Hg) and Nitrates (NO3-) from Seaweed Consumption
## 3 Results and Discussion
### Concentration and Dietary Intake of Toxic Metals (Cd, Pb, Hg)
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Origin**} & \multirow{2}{*}{**Species**} & \multicolumn{2}{c}{**Concentration \(\pm\) SD (mg/kg)**} & \multicolumn{2}{c}{**Contribution to TWI (\%)**} \\ \cline{4-6}  & & **SD (mg/kg)** & & **Hg (Org.)** & **Hg (Inorg.)** \\ \hline \multirow{4}{*}{Asia} & _Hijiki_ & 0.017 \(\pm\) 0.004 & 0.068 & 0.54 & 0.17 \\  & _Nori_ & 0.010 \(\pm\) 0.004 & 0.04 & 0.31 & 0.10 \\  & _Kombu_ & 0.054 \(\pm\) 0.017 & 0.216 & 1.70 & 0.55 \\  & _Wakame_ & 0.021 \(\pm\) 0.01 & 0.084 & 0.66 & 0.21 \\ \hline \multirow{4}{*}{Europe} & _Sea spaghetti_ & 0.007 \(\pm\) 0.003 & 0.028 & 0.22 & 0.07 \\  & _Kombu_ & 0.017 \(\pm\) 0.011 & 0.068 & 0.54 & 0.17 \\  & _Sea lettuce_ & \textless{}LOQ & & & \\ \cline{1-1}  & _Starry moss_ & 0.003 \(\pm\) 0.00 & 0.012 & 0.09 & 0.03 \\ \cline{1-1}  & _Nori_ & 0.003 \(\pm\) 0.00 & 0.012 & 0.09 & 0.03 \\ \cline{1-1}  & _Wakame_ & 0.008 \(\pm\) 0.008 & 0.032 & 0.25 & 0.08 \\ \cline{1-1}  & _Arame_ & 0.055 \(\pm\) 0.003 & 0.22 & 1.73 & 0.56 \\ \cline{1-1}  & _Mixed salad_ & 0.004 \(\pm\) 0.005 & 0.016 & 0.13 & 0.04 \\ \hline \hline \end{tabular}  
* Org., organic mercury; Inorg., inorganic mercury; TWI, tolerable weekly intake.  
\end{table} 
Table 6: Mercury concentrations, estimated intake (EDI), and percentage contribution to the guideline value of the analyzed algae. Figure 1: Comparison of the toxic metal content (Cd, Pb, Hg) between origins (Europe vs. Asia). The above-mentioned differences in the content of toxic metals between origins are due to the fact that, according to various studies, the high levels of contamination in toxic metals existing in the Asian coasts influence the quantity of these toxic metals in the environment where the algae grow. Notably higher levels of Cd, Pb, and Hg than those recorded in the present study have been reported in many areas of the Chinese coast [35]. The import of edible algae from Asian countries may pose a risk to the health of consumers in terms of toxic metal content. The environmental impact of toxic industrial discharges in algae cultivation areas such as the coast of Falk Bay in India [36] or the Gulf of Kutch in India [37] is of concern due to the increase in levels of heavy metals in algae. In many cases, an increase in Cd and Pb levels has been quantified in algae cultivated on the shores of Falk Bay, presenting levels of 4 mg Cd/kg dw (_Caulerpa racemosa_ species) or up to 15 mg Pb/kg dw (_Caulerpa racemosa_ species). Figure 2 shows the mean concentrations of toxic metals (Cd, Pb, Hg) in the different species of analyzed algae. The differences found in the metal content between species are due to the intrinsic features of each species, with some species being more prone to accumulating some metals than others. Similarly, the statistical study confirmed the existence of significant differences (\(p<0.05\)) in the content of Cd (arame vs. nori; sea spaghetti vs. hijiki, kombu, nori, mixed salad, and wakame; hijiki vs. kombu, mixed salad, and wakame; kombu vs. nori and wakame; nori vs. mixed salad and wakame), in the Pb content (arame vs. nori and mixed salad; sea spaghetti vs. wakame; hijiki vs. wakame; kombu vs. wakame), and in the Hg content (arame vs. sea spaghetti, kombu, nori, mixed salad, and wakame; sea spaghetti vs. kombu, hijiki, and wakame; hijiki vs. nori and mixed salad; kombu vs. nori and mixed salad; nori vs. mixed salad and wakame). Figure 2: Comparison of the toxic metal content (Cd, Pb, Hg) in the different species of analyzed algae. A study conducted by [PERSON] et al. [27] reported a Cd content in Asian wakame algae of 1.11 mg/kg, similar to the Cd content found in the present study in hijiki algae. In contrast, the Pb concentrations recorded by [PERSON] et al. [27] were higher than those found in the study here. However, the Hg content recorded in the present work is higher than the data published by [PERSON] et al. [27].