# Human Exposure to Toxic Metals (Cd, Pb, Hg) and Nitrates (NO3-) from Seaweed Consumption
## 3 Results and Discussion
### Nitrate Concentrations (NO3\({}^{-}\)) and Dietary Intake  
Table 7 shows the mean nitrate concentrations in the analyzed algae as well as the estimated daily intake values and their percentage contribution to the ADI value set by EFSA in 2017 [24; 25].  
The nori species has the highest concentration of nitrates, with a mean value of 3183 mg/kg and with larger samples >8000 mg/kg. On the other hand, kombu seaweed has a mean concentration of 3084 mg/kg with a maximum value of 6400 mg/kg.  
It should be noted that there is no legislation regulating the content of nitrates in seaweed. However, Commission Regulation (EU) No. 1258/2011 of 2 December 2011, which modified Regulation (EC) No. 1881/2006 with regard to the maximum content of nitrates in food products, set a limit of between 6000 and 7000 mg/kg for rocket or arugula [39]. Considering the limit applicable to arugula, whose permitted concentrations of nitrates are the highest of all foods, some kombu samples would exceed this limit, and therefore would not be suitable for human consumption.  
However, taking into account the manufacturer's recommended consumption of 4 g of nori algae per day, the mean concentration of 3183 mg/kg would represent a percentage contribution to the ADI of nitrates (3.7 mg/kg bw/day) of 5.02%. Although this would  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Species**} & [**NO3\({}^{-}\)**] \(\pm\) SD** & **Max.** & **Min.** & **EDI** & **Contribution** \\  & **(mg/kg)** & **Value** & **Value** & **(mg/day)** & **to ADI (\%)** \\ \hline _Arame_ & \textless{}500 & - & - & - & - \\ _San Substitution_ & \textless{}500 & - & - & - & - \\ _Hijiki_ & \textless{}500 & - & - & - & - \\ _Kombu_ & 3084 \(\pm\) 2698 & 6400 & \textless{}500 & 12.34 & 4.87 \\ _Sea lettuce_ & 965 \(\pm\) 135 & & & 3.86 & 1.52 \\ _Mixed salad_ & 1096 \(\pm\) 203 & 1239 & 952 & 4.38 & 1.73 \\ _Starry moss_ & \textless{}500 & - & - & - & - \\ _Nori_ & 3183 \(\pm\) 2279 & \textgreater{}8000 & \textless{}500 & 12.73 & 5.02 \\ _Wakame_ & \textless{}500 & - & - & - & - \\ \hline \hline \end{tabular} ADI, acceptable daily intake.  
\end{table}
Table 7: Concentration of nitrates (mg/kg), standard deviations (SD), estimated daily intake, and contribution to the ADI of the analyzed algae.  
not pose a risk to adult health, it should be borne in mind that the storage and the cooking process of algae, etc. can lead to the transformation of nitrates into nitrites, thus posing a risk to the consumers' health.  
Although the algae analyzed do not suppose a high intake, the importance of taking into account other nitrate sources such as water and other vegetable foods should be noted. A study carried out by [PERSON] et al. [40] reported nitrate levels in water from wells and springs of Azadshahr (northeastern Iran) of 1 up to 51 mg/L. [PERSON] et al. [41] determined the nitrate content in vegetables marketed in Valencia (Spain), finding concentrations of 40 mg/kg (carrots), 173.5 mg/kg (potatoes), and 1266.5 mg/kg (fresh spinach). It is advisable to moderate the consumption of the algae species that recorded the highest nitrate concentrations, especially in vegans or vegetarians, and by people living in areas of high concentrations of nitrate in the water supply.