Toenails as biomarker of exposure to essential trace metals: A review.

Biomonitoring of Metals in Children Living in an Urban Area and Close to Waste Incinerators

“…Several studies measured the concentration of V in nails [40,47,48,81,94,95], reporting an LOD of 0.001 µg/g [81], an inverse relation with age [47,94,95], and values generally lower than 1 µg/g [40]. This was also the case of toenail V concentration measured in the exposed children from our study (0.19 µg/g).…”

“…The slow rate of growth of toenails (on average 1.62 mm/month) [37] allows to evaluate longer term exposure [37], as compared with blood or urine [38][39][40]. Few studies evaluated the correlation between the concentration of metals in nails and in other biological matrices, with variable results [40] probably due to the different time windows that can be explored using nails (6-12 months earlier [37,40,67,71,72]), blood (2-3 h [73]), and urine (3-4 days [74]). Positive correlations have been documented between concentration in toenails, urine, and blood in the case of Mn [75] which, in the present study, has been found in higher concentration in exposed children than in controls.…”

“…Toenail concentration of Mn has been frequently studied both in children [47][48][49][50] and in adults [40], with an LOD ranging from 0.001 [81] to 0.33 µg/g [66] and values usually below 10 µg/g [40]. The highest Mn toenail concentrations have been found in subjects living near a highly industrialized city in Pakistan (average value 52.1 µg/g) [82] and in highly polluted areas in Cambodia (average concentration 43.9 µg/g) [66].…”

“…Studies exploring the specific concentrations of heavy metals in air samples collected around a Spanish municipal solid waste incinerator showed that the highest concentration was registered for Cu [83,85]. Previous studies assessed nail Cu concentrations both in adults [40,86] and in children [47], indicating an LOD ranging, for this metal, from 0.009 to 0.12 µg/g, with values usually below 10 µg/g [40]. The highest Cu concentration in nails (average value 26.2 µg/g) has been recorded in subjects living in rural areas near a highly industrialized city in Pakistan [82].…”

“…Several studies explored the concentration of heavy metals (mainly lead, cadmium, mercury, nickel, and chromium) in adults exposed to emissions from waste incinerators [31][32][33][34][35][36]. However, in the majority of cases a limited number of metals have been considered, and the sampling procedures were on blood and/or urine, thus mainly representing shortrather than long-term exposure [37][38][39][40]. Similarly, previous biomonitoring studies in exposed children only determined the body burden of few trace elements (mainly manganese [3], chromium, lead, and cadmium [41][42][43]), not considering the wide panel of metals [1,5] emitted by waste incinerators.…”