# Weekly and Longitudinal Element Variability in Hair Samples of Subjects Non-Occupationally Exposed
## 3 Results and Discussion
### Element Content in Human Hair Samples
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Elem.**} & \multirow{2}{*}{**Nucl. 1**} & \multicolumn{4}{c}{**BCR CRM 397**} & \multicolumn{4}{c}{**NIST-SRM 1515**} \\ \cline{3-8}  & & **Found** & **Certified** & \(\Delta\) & **Found** & **Certified** & \(\Delta\) \\ \hline As & \({}^{76}\)As & 0.29 \(\pm\) 0.02 & (0.31 \(\pm\) 0.02) a & \(-\)6.5 & n.d. & - & - \\ Ba & \({}^{131}\)Ba & n.d. & - & - & 51.0 \(\pm\) 8.0 & 48.8 \(\pm\) 2.3 & 4.3 \\ Br & \({}^{82}\)Br & n.d. & - & - & 3.1 \(\pm\) 0.7 & (1.8) b & 41.9 \\ Ca & \({}^{47}\)Ca & n.d. & (1560 \(\pm\) 40) b & - & 15267 \(\pm\) 676 & 15250 \(\pm\) 100 & 0.3 \\ Ce & \({}^{14}\)Ce & n.d. & - & - & 3.6 \(\pm\) 0.3 & (3) b & 20.0 \\ Co & \({}^{60}\)Co & 0.56 \(\pm\) 0.02 & (0.55 \(\pm\) 0.03) b & 1.8 & 0.10 \(\pm\) 0.01 & (0.09) b & 10.0 \\ Cr & \({}^{51}\)Cr & \(93\pm 9\) & (91 \(\pm\) 33) b & 2.2 & 0.4 \(\pm\) 0.1 & (0.3) b & 33.3 \\ Cu & \({}^{64}\)Cu & \(113\pm 7\) & (110 \(\pm\) 5) a & 2.7 & n.d. & 5.69 \(\pm\) 0.13 & - \\ Fe & \({}^{59}\)Fe & \(575\pm 4\) & (580 \(\pm\) 10) b & \(-\)0.9 & 72 \(\pm\) 1 & 82.7 \(\pm\) 2.6 & \(-\)12.9 \\ Hg & \({}^{203}\)Hg & \(13.0\pm 0.8\) & 12.3 \(\pm\) 0.5 & 5.7 & 0.0223 \(\pm\) 0.0102 & 0.0432 \(\pm\) 0.0023 & \(-\)48.4 \\ K & \({}^{42}\)K & n.d. & - & - & 16035 \(\pm\) 717 & 16080 \(\pm\) 210 & \(-\)0.6 \\ La & \({}^{140}\)La & n.d. & - & - & 20.4 \(\pm\) 0.5 & (20) b & 2.0 \\ Mn & \({}^{56}\)Mn & \(10.9\pm 0.6\) & (11.2 \(\pm\) 0.3) b & \(-\)2.7 & 54.4 \(\pm\) 1.6 & 54.1 \(\pm\) 1.1 & 0.6 \\ Na & \({}^{24}\)Na & n.d. & - & - & 28.3 \(\pm\) 0.7 & 24.4 \(\pm\) 2.1 & 16.0 \\ Ni & \({}^{56}\)Co & n.d. & (46.0 \(\pm\) 1.4) a & - & 0.731 \(\pm\) 0.080 & 0.936 \(\pm\) 0.094 & \(-\)21.9 \\ Rb & \({}^{86}\)Rb & n.d. & - & - & 9.4 \(\pm\) 0.9 & 10.2 \(\pm\) 1.6 & \(-\)7.8 \\ Sc & \({}^{46}\)Sc & n.d. & - & - & 0.028 \(\pm\) 0.001 & (0.03) b & \(-\)6.7 \\ Se & \({}^{75}\)Se & 2.1 \(\pm\) 0.1 & 2.00 \(\pm\) 0.08 & 5.0 & n.d. & - & - \\ Sm & \({}^{153}\)Sm & n.d. & - & - & 2.9 \(\pm\) 0.1 & (3) b & 3.3 \\ Sr & \({}^{85}\)Sr & n.d. & - & - & 28.0 \(\pm\) 3.0 & 25.1 \(\pm\) 1.1 & 11.6 \\ \hline Zn & \({}^{65}\)Zn & \(196\pm 4\) & \(199\pm 5\) & \(-\)1.5 & 12.50 \(\pm\) 0.11 & 12.45 \(\pm\) 0.43 & 0.4 \\ \hline \hline \end{tabular}  
* Product nuclide; a indicative values expressed as \(\upmu\)g g\({}^{-1}\); b informative values expressed as \(\upmu\)g g\({}^{-1}\); n.d.: not detected; \(\Delta\): difference (%) between our mean values calculated and certified one as \(\frac{(corulae-certifiable)}{cortifiable}\times 100\). The standard deviation is calculated among five replicas.  
\end{table} 
Table 1: Analytical standard comparison (mean \(\pm\) s.d. ; \(\upmu\)g g\({}^{-1}\)) between our data and certified values: BCR CRM 397 (human hair) and NIST-SRM 1515 (Apple Leaves). Br, Ca, K, and Na, the last three considered labile elements (because they are strongly influenced by washing [64]) show a low CV% below 27%, confirming that the hair was not washed. Silver and gold are present at low concentrations, 740 and 22 ng g\({}^{-1}\), respectively: their presence could suggest a previous use of shampoos containing nanoparticles of these two elements into the composition for antimicrobial activity [65; 66]. Other elements such as La, Rb, Sc, Th, and W can be considered of environmental origin: their CVs% are high, above 60%, especially Th, up to 200%. Finally, Ba, Br, and Sb show low CVs%: their presence and levels could be due to anthropogenic pollution and particularly to airborne particulate matter, as just evidenced by authors in previous papers [46; 49]. Table 3 shows the concentration trend (the number of samples per nuclide is too low--only three scalp locations and two longitudinal positions--to obtain any actual reasonable trend that could be considered real and not obtained by chance) in the areas of the nape where the sampling was carried out (left, center, and right) as well as the longitudinal variation of the concentrations along the hair.