# Weekly and Longitudinal Element Variability in Hair Samples of Subjects Non-Occupationally Exposed
## 3 Results and Discussion
### Element Content in Human Hair Samples
If the trends of Br, Ca, K, and Na from Tables 2 and 3 are taken into account, similar concentrations are noted for Br both during the days and in correspondence with the sampling zones and in the longitudinal variation: mean value 26.5 \(\pm\) 3.46 \(\mu\)g g\({}^{-1}\); 1 st day 25.0 \(\pm\) 3.0 \(\mu\)g g\({}^{-1}\); 2 nd day 24.1 \(\pm\) 0.6 \(\mu\)g g\({}^{-1}\); 3 rd day 30.4 \(\pm\) 2.3 \(\mu\)g g\({}^{-1}\) (Table 2); left zone 27.1 \(\pm\) 2.1 \(\mu\)g g\({}^{-1}\); central 23.7 \(\pm\) 0.45 \(\mu\)g g\({}^{-1}\); right 28.8 \(\pm\) 1.7 \(\mu\)g g\({}^{-1}\); hair proximal section 26.5 \(\pm\) 2.6 \(\mu\)g g\({}^{-1}\); distal 26.5 \(\pm\) 4.9 \(\mu\)g g\({}^{-1}\). The same stability in the concentration trend is evident for Na, Ca, and K. These four elements, i.e., Br, Ca, K, and Na, are ubiquitous in the environment; besides, Ca, K, and Na are among the fundamental components of the tissues and biological fluids in the human body, and K and Na are also present in the body secretions (exudate, etc.). In the samples, Br, K, and Na show an increasing concentration trend between the first and third day (Table 2). Similarly, the same trend is shown, but in a much more marked way, by elements of environmental origin such as La, + 47.5% \begin{table}
\begin{tabular}{c c c c c} \hline
**Element** & **Concentration** & \multicolumn{2}{c}{**Concentration (Mean \(\pm\) s.d. 1)**} \\ \hline  & **x (Min–Max; CV%)** & **1 st Day** & **2 nd Day** & **3 rd Day** \\ \hline Ag & 0.740 (0.34–1.2; 36.6) & 0.630 \(\pm\) 0.354 & 0.855 \(\pm\) 0.417 & 0.735 \(\pm\) 0.134 \\ As & \textless{}LOD & \textless{}LOD & \textless{}LOD & \textless{}LOD \\ Au & 0.022 (0.008–0.37; 63.6) & \textless{}LOD & 0.010 \(\pm\) 0.03 & 0.028 \(\pm\) 0.013 \\ Ba & 1.44 (1.20–1.69; 15.9) & 1.20 \(\pm\) 0.18 & 1.58 \(\pm\) 0.31 & 1.50 \(\pm\) 0.27 \\ Br & 26.5 (22.9–32.1; 13.2) & 25.0 \(\pm\) 3.0 & 24.1 \(\pm\) 0.6 & 30.4 \(\pm\) 2.3 \\ Ca & 2010 (1363–2601; 25.4) & 1982 \(\pm\) 875 & 2264 \(\pm\) 468 & 1784 \(\pm\) 303 \\ Co & 0.041 (0.031–0.066; 31.7) & 0.032 \(\pm\) 0.002 & 0.038 \(\pm\) 0.006 & 0.054 \(\pm\) 0.017 \\ Cr & 0.086 (0.002–0.180; 66.2) & 0.086 \(\pm\) 0.006 & 0.081 \(\pm\) 0.007 & 0.092 \(\pm\) 0.128 \\ Cu & 15.1 (2.30–27.8; 68.8) & 19.9 \(\pm\) 9.0 & 21.2 \(\pm\) 9.4 & 4.17 \(\pm\) 2.70 \\ Eu & 0.001(0.001; N/A) & \textless{}LOD & \textless{}LOD & 0.001 \\ Fe & 17.7 (13.5–28.4; 33.3) & 14.1 \(\pm\) 0.1 & 14.3 \(\pm\) 1.1 & 24.6 \(\pm\) 5.4 \\ Hg & \textless{}LOD & \textless{}LOD & \textless{}LOD & \textless{}LOD \\ K & 249 (178–364; 26.5) & 195 \(\pm\) 23 & 228 \(\pm\) 8 & 323 \(\pm\) 58 \\ La & 0.957 (0.288–1.54; 61.8) & 0.915 \(\pm\) 0.886 & 0.805 \(\pm\) 0.641 & 1.35 \(\pm\) 0.12 \\ Mn & 3.75 (1.91–5.22; 33.0) & 3.10 \(\pm\) 1.70 & 3.20 & 4.66 \(\pm\) 0.69 \\ Na & 109 (88.2–141; 16.5) & 95.1 \(\pm\) 9.8 & 109 \(\pm\) 6 & 122 \(\pm\) 27 \\ Rb & 0.269 (0.105–0.540; 60.9) & 0.117 \(\pm\) 0.017 & 0.319 \(\pm\) 0.070 & 0.370 \(\pm\) 0.241 \\ Sb & 0.075 (0.045–0.120; 37.3) & 0.055 \(\pm\) 0.013 & 0.076 \(\pm\) 0.029 & 0.096 \(\pm\) 0.034 \\ Sc & 0.007 (0.002–0.011; 71.4) & 0.007 \(\pm\) 0.007 & \textless{}LOD & 0.007 \(\pm\) 0.006 \\ Se & 0.413 (0.035–0.050; 13.3) & 0.390 \(\pm\) 0.057 & 0.455 \(\pm\) 0.064 & 0.395 \(\pm\) 0.049 \\ Tb & 0.020 (0.020; N/A) & \textless{}LOD & \textless{}LOD & 0.020 \\ Th & 0.009 (0.000–0.036; 200) & 0.00033 & 0.00043 & 0.018 \(\pm\) 0.025 \\ W & 0.019 (0.012–0.043; 63.1) & 0.012 \(\pm\) 0.001 & 0.015 \(\pm\) 0.003 & 0.031 \(\pm\) 0.017 \\ Zn & 52.3 (66.3–92; 37.2) & 77.1 \(\pm\) 12.0 & 89.7 \(\pm\) 3.9 & 72.1 \(\pm\) 8.2 \\ \hline \end{tabular} \({}^{1}\) s.d. standard deviation.  
\end{table} 
Table 2: Element levels and single daily concentrations (\(\mu\)g g\({}^{-1}\)) determined in all the investigated independent samples (five independent measurements). increase in concentration on the third day compared to the first; Rb, + 216%; Th, + 98%; and W + 158%.