## 4 Discussion  
We assessed the impact on short-term (urine) and long-term (toenails) metal biomarkers levels of seafood, mollusk and fish consumption before urine and toenail sample donation in a group of workers occupationally exposed to metal and controls. We found that the impact of SMFc is different depending on the metals for urine and toenail samples. We found that among workers exposed to metals, when urine is used as a matrix for biomonitoring, arsenic and cobalt can be influenced by any type of fish consumption. Arsenic showed statistically significant relationships with sea fish (white and blue fish and canned sardines), and mercury showed significance after blue fish and, especially, canned sardines. Moreover, arsenic and lithium levels are statistically related with seafood or mollusk consumption, while the other studied metals (Ba, Be, Cd, Cu, Hg, Pb, Se, Sr, Tl, V, W and Zn) did not reflect any statistical relation. On the other hand, when using a biomarker for long-term exposure (like toenails), recent intake of fish and seafood or mollusks did not have any impact except for aluminum and beryllium after fish consumption. Toenails seem to be a good biomarker to evaluate metal bioaccumulation because of their advantages for large epidemiological studies and because they represent longer-term exposures compared with other biomarkers, which is an essential feature to study the involvement of certain occupational exposures. As our study has shown, matrices that capture long-term exposure, such as toenails, are better biom indicators of workers' occupational metal exposure because they are less influenced by specific factors that could distort metal exposure levels, like SMFc. In metal-exposed workers, urine does not appear to be a good biomarker of occupational exposure to total arsenic or cobalt, as matrices that capture short-term contamination are more sensitive to any specific interference. Alternatively, when biomonitoring occupational short-term exposure to total arsenic, seafood consumption \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & **No SMFc 1** & **Any Type** & **Mann-Whitney 2** & **Shell** & **No-Shell** & **Shrimps,** & **Median Test 3** \\ \hline  & n = 87 & n = 11 & \(p\) & n = 1 & n = 4 & n = 6 & \(p\) \\ \hline Al & 9.5 & 11.2 & 0.884 & 29.4 & 4.8 & 12.6 & 0.053 \\ As & 0.109 & 0.069 & 0.555 & 0.069 & 0.077 & 0.131 & 0.551 \\ Ba & 1.110 & 0.925 & 0.478 & 0.726 & 0.722 & 1.598 & 0.444 \\ Be & 0.0002 & 0.0005 & 0.502 & 0.0086 & 0.0002 & 0.0007 & 0.621 \\ Cd & 0.031 & 0.022 & 0.809 & 0.018 & 0.036 & 0.036 & 0.808 \\ Co & 0.016 & 0.017 & 0.475 & 0.025 & 0.031 & 0.016 & 0.551 \\ Cr & 1.017 & 0.818 & 0.293 & 0.354 & 1.319 & 0.693 & 0.621 \\ Cu & 4.940 & 4.212 & 0.870 & 2.429 & 3.267 & 5.286 & 0.444 \\ Fe & 27.5 & 30.3 & 0.464 & 54.6 & 29.8 & 28.9 & 0.798 \\ Hg & 0.206 & 0.196 & 0.609 & 0.166 & 0.268 & 0.186 & 0.798 \\ Li & 0.028 & 0.021 & 0.528 & 0.019 & 0.014 & 0.035 & 0.127 \\ Mn & 0.360 & 0.584 & 0.710 & 0.421 & 0.140 & 0.691 & 0.189 \\ Mo & 0.050 & 0.060 & 0.818 & 0.037 & 0.074 & 0.027 & 0.128 \\ Pb & 2.190 & 3.156 & 0.879 & 3.156 & 2.080 & 2.699 & 0.798 \\ Ni & 0.595 & 1.170 & 0.140 & 0.543 & 1.036 & 1.500 & 0.428 \\ Se & 0.811 & 0.746 & 0.690 & 0.792 & 0.926 & 0.729 & 0.621 \\ Sr & 1.050 & 0.967 & 0.831 & 0.467 & 1.273 & 1.360 & 0.798 \\ Tl & 0.003 & 0.001 & 0.298 & 0.000 & 0.002 & 0.002 & 0.798 \\ U & 0.004 & 0.005 & 0.748 & 0.004 & 0.004 & 0.005 & 0.287 \\ V & 0.035 & 0.027 & 0.282 & 0.028 & 0.024 & 0.027 & 0.399 \\ W & 0.005 & 0.005 & 0.393 & 0.002 & 0.009 & 0.006 & 0.818 \\ Zn & 100.0 & 95.2 & 0.657 & 82.0 & 89.1 & 126.2 & 0.551 \\ \hline \hline \end{tabular}  
* No shellfish or mollusk consumption in the 8 h prior to donating the toenail sample. 2 No shellfish or mollusk consumption vs. any type of shellfish or mollusk consumption. 3 No shellfish or mollusk consumption vs. type of shellfish or mollusk consumption.  
\end{table}