Nail is a biological specimen that has some advantages as a
biomarker for trace elements exposure, especially because its collection
is noninvasive and simple and because nail samples are
very stable after collection, not requiring special storage conditions
[1,2]. Trace elements in nails reflect long-term exposure because
this compartment remains isolated from other metabolic activities
in the body [2,3]. Because toenails are less affected by exogenous
environmental contamination than fingernails, they have been preferred
for exposure to toxic metals [3]. Toenails have a slower
growth rate than fingernails (up to 50% slower, especially in winter)
and thus may provide a longer integration of the exposure [2–4].
Atomic absorption spectrometry (AAS) [5,6] and inductively
coupled plasma emission spectrometry (ICP-OES) [7] are still the
dominant analytical techniques used for trace element analysis