Metal levels in urine samples and in air particulate matter in Turin metropolitan area (Italy): a comparison study

Introduction Current scientific knowledge gives high relevance to oral assumption through diet in determining metal levels in human body while other pathways, like inhalation, are less effective. Objective of this study, performed within the SPoTT health surveillance program, was to evaluate the correlation between metal concentration present in particular matter and metals content in urines of a sample of residents of the Turin metropolitan area. Methods 394 subjects (35-69 years) were randomly selected from the municipal registers, equally distributed by gender age group, and residential area, whose urine samples were collected in two periods, T0, (June-July 2013), and after one year T1 (July 2014). In the same period monthly concentrations of selected metals were computed on particulate matter (PM) sampled from 2 monitoring stations near resident addresses, representative of the two areas considered. Mean and median levels of urine metals were computed at T0 and T1, and compared with analogous levels in PM samples. The metals analysed both at T0 and T1 and in samples of Particulate Matter were: As, Cd, Co, Cr, Cu, Ni, V, and Zn. Results 96% of the original sample at T0 completed the examination at T1 phase. On average, a decrease of ca. -30% (ranging from -2% for Ni to -57% of As) of metals content in urine (except Cr, that showed an increase of about +18%) was found, along with an analogous overall PM2.5 annual concentrations percentage reduction (-25%). The levels of metals among PM samples showed a good correlation with urine levels (R2=.77, with a similar rise in Cr increase – +14%) when confounding factors (change in diet composition) were taken into account. Conclusions Inhalation of PM could be a non negligible pathway of assumption of some metals, given that the metallic dietary composition and its oral assumption does not vary along time.