# Health Risk from Toxic Metals in Wild Rice Grown in Copper Mining-Impacted Sediments
## 3 Results and Discussion
### Human Health Risk Assessment  
A human health risk assessment was performed to understand the potential life-long non-carcinogenic and carcinogenic risks from a diet of wild rice. Potential non-carcinogenic risk calculations due to exposure to toxic metals through the ingestion of wild rice were performed according to USEPA [16]. The mean HQ values were in the order of As (2.13) > Hg (0.12) > Cd (0.09) > Cr (0.07) > Cu (0.07) > Zn (0.01) for Lake Plumbago wild rice seed samples. Out of the metals tested, As had the highest value of 2.13, but for all other metals, the values were well below one, indicating minimal non-carcinogenic risk from daily consumption of wild rice. For the Sand Point samples, the non-carcinogenic risk from As was also the highest (1.12). The HQ values were in the order of As (1.12) > Cd (0.2) > Hg (0.18) > Zn (0.06) > Cu (0.04). Similar to the Lake Plumbago wild rice seed samples, the values were well below one, except for As. The combined non-carcinogenic effects of multiple toxic metals were obtained by calculating the HI values, which is the summation of all the individual HQs [22]. The HI values for the toxic metals in wild rice seeds from both sites were high, 2.50 for Lake Plumbago, and 1.61 for the Sand Point site (Figure 4). The high HI values indicate that although the individual metals are at levels low enough to \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Samples and Locations**} & **A1** & **As** & **Cd** & **Cr** & **Cu** & **Hg** & **Mn** & **Ni** & **Pb** & **Zn** \\ \hline \multirow{2}{*}{_Wild Rice_} & Sand Point & 16.3 & 243.38 & 152.81 & 16.85 & 17.47 & 0.29 & 40.59 & 17.38 & 257.93 & 29.89 \\  & Sloughs & (5.91) \({}^{1}\) & (52.99) & (8.82) & (6.55) & (5.87) & (0.11) & (11.69) & (6.54) & (39.33) & (7.58) \\  & Lake Plumbago & 9.29 & 89.89 & 33.04 & 8.42 & 21.59 & 0.27 & 15.85 & 11.44 & 12.41 & 9.11 \\  & (2.88) & (29.29) & (0.9) & (2.62) & (3.32) & (0.04) & (0.57) & (2.1) & (2.13) & (2.64) \\ \hline \multirow{2}{*}{_Wild Rice_} & Sand Point & 2.07 & 243.38 & 3.83 & 2.14 & 1.90 & 0.27 & 18.02 & 2.28 & 1.79 & 8.67 \\  & Sloughs & (0.46) & (52.99) & (0.15) & (0.39) & (0.32) & (0.08) & (1.54) & (0.96) & (1.07) & (0.16) \\  & Lake Plumbago & 0.16 & 1 & 0.4 & 0.07 & 0.79 & 0.08 & 1.9 & 0.1 & 0.1 & \\  & (0.05) & (0.4) & (0.04) & (0.05) & (0.48) & (0.01) & (0.34) & (0.04) & & N/A \({}^{2}\) & 1.03 \\ \hline \multirow{2}{*}{_Wild Rice_} & Sand Point & 0.84 & 1.59 & 0.41 & 0.76 & 0.28 & 27.48 & \multirow{2}{*}{N/A} & \multirow{2}{*}{N/A} & 14.02 \\  & Sloughs & (0.25) & (0.52) & (0.06) & (0.1) & (0.09) & (9.64) & & & (3.28) \\ \multirow{2}{*}{_Grain_} & 0.15 & 1.06 & 1.87 & 0.07 & 1.12 & 0.14 & 1.57 & 0.23 & N/A & 3.3 \\  & Lake Plumbago & (0.03) & (0.46) & (0.64) & (0.03) & (0.23) & (0.02) & (0.48) & (0.1) & N/A & (0.25) \\ \hline \hline \end{tabular} Notes: \({}^{1}\) Mean values are displayed followed by standard deviations in parentheses; \({}^{2}\) N/A = non-detectable levels of trace elements  
\end{table} 
Table 2: Bioconcentration factor of toxic elements in various parts of wild rice plants from Sand Point sloughs and Lake Plumbago. Figure 3: Total element concentrations in Sand Point sloughs and Lake Plumbago sediment, porewater, and plant samples. The concentrations are expressed as mg/kg for sediment and plant samples and mg/L in water samples. (**A**). Copper, (**B**). Zinc. Data are reported as mean \(\pm\) S.D. (\(n\) = 3). pose no health risk other than As, the combined set of toxic metals poses a considerable non-carcinogenic risk to human health. Carcinogenic risk for the toxic metals As, Cr, and Cd was calculated according to USEPA, 2019 [18]. The mean risk levels from As for rice seed samples from Sand Point and Lake Plumbago were 2.16 \(\times\) 10\({}^{-4}\) and 4.11 \(\times\) 10\({}^{-4}\), respectively (Table 3). For Cr, the risk from oral ingestion of wild rice seed samples from Lake Plumbago was 4.47 \(\times\) 10\({}^{-5}\).