# Weekly and Longitudinal Element Variability in Hair Samples of Subjects Non-Occupationally Exposed
###### Abstract  
Hair is an ideal tissue for tracing the human health conditions. It can be cut easily and painlessly, and the relative clinical results can give an indication of mineral status and toxic metal accumulation following long-term or even acute exposure. Different authors have found outdoor pollution phenomena, such as the levels, significantly alter metal and metalloid hair contents. This paper investigates the element concentration variability in hair samples collected from a not-exposed teenager, neither environmentally nor professionally. The sampling was carried out for one week, and the samples were collected from different locations on the scalp. A nuclear analytical methodology, i.e., the Instrumental Neutron Activation Analysis, is used for determining about 30 elements. Some differences have been found among the samplings as well as between the proximal and distal sections. A deep comparison with other similar studies worldwide present in the literature has been performed for evidencing the relationships and the differences due to different ethnical origins, lifestyles, diets, and climates among the different young populations.  
h airs; variability; week; longitudinal; element; metals; INAA; occupational exposure; unexposed subject +
Footnote †: journal: Medical  
area and the lifestyle of each person [30; 31]. Although there is in literature a great deal of papers regarding the determination of the elemental content in hairs [32; 33; 34; 35], to the authors' knowledge, no paper is focused on the element variability during a week. On the other hand, a few studies concern the longitudinal element distribution along human hairs: [PERSON] et al. [36] reported the variation of the trace element concentration in long human hairs, showing the profiles according to the distance from the scalp; [PERSON] and coauthors [37; 38] discussed how the exogenous contamination does not influence the levels of some elements (for instance, Zn); on the contrary, [PERSON] and [PERSON] [39] report that some other elements, such as Al, are subjected to being accumulated during pollution events and such as Ca, which was demonstrated to be sensitive to endogenous and exogenous contributions [40]; [PERSON] et al. discussed the longitudinal association between toenail zinc levels and the incidence of diabetes among American young adults [41]. Finally, [PERSON] et al. [42] reported a forensic case of poisoning by thallium: the authors developed an analytical method in order to determine the Tl profile all along the hair. The present authors agree with the consideration reported in a recent paper focused on the variation of longitudinal concentration of trace elements in elephant and giraffe hairs [43]. In here, it is highlighted that an important role for this concentration is played by the animals' behavior traits, which suggests that these traits have to be considered also in the study of human hair. Such studies are necessary for having knowledge of endogenous and exogenous roles of hair elements.  
Starting from these considerations, this paper would like to investigate the element concentration variability in hair samples collected from a not-exposed teenager, neither environmentally nor professionally. The sampling was carried out for one week, and the samples were collected from different locations on the scalp. Each hair sample was divided into two parts in order to study the section closest (proximal) to the scalp and the most distant (distal) from it. The analyses were performed by Instrumental Neutron Activation Analysis (INAA), and about 30 elements were determined. The use of such analytical technique allowed minimizing the pre-treatment of the samples and hence the relative positive/negative artifacts and performing a multi-elemental determination simultaneously [44; 45; 46].