RT Journal Article
T1 Toenails as biomarker of exposure to essential trace metals: A review
A1 Gutiérrez González, Enrique
A1 García Esquinas, Esther
A1 Fernandez de Larrea-Baz, Nerea
A1 Salcedo Bellido, Inmaculada
A1 Navas Acien, Ana
A1 Lope, Virginia
A1 Gómez Ariza, José Luis
A1 Pastor Barriuso, Roberto
A1 Pollán, Marina
A1 Pérez Gómez, Beatriz
AB Health problems associated with essential trace metals can result from both inadequate (i.e., low intake) andexcessive exposures (i.e., from environmental and/or occupational source). Thus, measuring the exposure levelis a real challenge for epidemiologists. Among non-invasive biomarkers that intend to measure long-term exposureto essential trace metals, the toenail is probably the biological matrix with the greatest potential.This systematic review collects the current evidence regarding the validity of toenail clippings as exposurebiomarker for trace metals such as boron, cobalt, copper, iron, manganese, molybdenum, selenium, silicon,vanadium and zinc. Special attention was paid to the time-window of exposure reflected by the toenail, theintraindividual variability in exposure levels over time in this matrix, and the relationship of toenail with otherbiomarkers, personal characteristics and environmental sources.Our search identified 139 papers, with selenium and zinc being the most studied elements. The variabilityamong studies suggests that toenail levels may reflect different degrees of exposure and probably correspond toexposures occurred 3–12 months before sampling (i.e., for manganese/selenium). Few studies assessed the reproducibilityof results over time and, for samples obtained 1–6 years apart, the correlation coefficient werebetween 0.26 and 0.66. Trace metal levels in toenails did not correlate well with those in the blood and urine andshowed low-moderate correlation with those in the hair and fingernails.Available data suggests that for some elements (Se, Mn, Zn) toenail concentrations reflect long-term externalexposures in fairly reproducible levels, while for other metals, this association has not yet been assessed. Amongdietary factors, only toenail selenium showed clear associations with the intake of supplements or specific foods.The toenail levels could also represent occupational exposure, for instance, Mn exposure in welders. The scarcityof information on other essential trace elements, together with the great heterogeneity among studies makes thevalidation of the usage of toenails as biomarkers of exposure to these elements difficult. Standardization ofsample collection, quality control, analytical techniques and reporting procedures might facilitate further researchfocused on the clear understanding of the significance of essential levels in this promising matrix andwould enhance its utility in epidemiological research.
PB Elsevier
SN 0013-9351
YR 2019
FD 2019-10
LK https://hdl.handle.net/10272/25193
UL https://hdl.handle.net/10272/25193
LA eng
NO Gutiérrez-González, E., García-Esquinas, E., de Larrea-Baz, N. F., Salcedo-Bellido, I., Navas-Acien, A., Lope, V., Gómez-Ariza, J. L., Pastor, R., Pollán, M., & Pérez-Gómez, B. (2019). Toenails as biomarker of exposure to essential trace metals: A review. In Environmental Research (Vol. 179, p. 108787). Elsevier BV. https://doi.org/10.1016/j.envres.2019.108787
NO This work was supported by FIS grants PI12/00150, PI17CIII/00034 & PI18/00287 (Instituto de Salud Carlos III, State Secretary of R + D + I and European Union (ERDF/ESF, "Investing in your future")).
DS Repositorio Institucional de la Universidad de Huelva
RD 14 jul 2026