Hair and nails can serve as important biological samples for assessing past exposure to trace elements, making them increasingly valuable in clinical and epidemiological studies evaluating the effects of environmental factors on human health. In the Laboratory for Enzyme and Trace Element Analytics at the University Medical Centre Ljubljana (UMCL), concentrations of trace elements are typically determined in blood and urine samples. In this master's thesis, we developed and validated a method for the quantitative determination of concentrations of 26 trace elements in hair and nail samples, including 7 essential and 19 non-essential elements.
Based on a literature review, we developed a method for trace element determination that incorporates pre-analytical procedures (washing, drying, and acid digestion using a microwave) and liquid sample analysis using inductively coupled plasma mass spectrometry (ICP-MS). The method was validated according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI), assessing detection capability, precision, accuracy, linearity, and working range. Based on the validation parameters, we determined that the method meets the requirements for its intended use in determining trace elements in nails and hair. In samples from 140 healthy individuals of both sexes, we established 95% reference intervals for both essential and non-essential elements, which were comparable to those in the literature, albeit somewhat narrower. We further evaluated the impact of exogenous and endogenous factors on trace element concentrations in toenails and hair. We observed differences in the concentrations of V, Mn, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Ag, Cd, and Sn between genders. With age, the concentrations of most elements in hair and nail samples slightly decreased. Hg concentrations were elevated in the Coastal-Karst and Goriška regions, while no significant regional differences were observed for other elements. Supplement intake increased Se content in nails, and seafood consumption raised Hg concentrations in both nails and hair. Smokers had higher concentrations of Cd and Pb in their hair and nails, with these elements correlating with the number of cigarettes smoked per day. Nail polish did not show statistically significant differences in element concentrations, whereas hair dyeing affected the concentrations of certain elements. Mn, Co, Ni, Sr, and Ba were higher in dyed hair, while Cu, Zn, As, Se, and Mo were lower compared to undyed hair. Finally, we compared trace element concentrations in nails and hair. Weak positive correlations were found for Mn, Co, Cu, Se, Al, Ga, As, Sn, Cs, Au, V, and Pb, while a strong positive correlation was observed for Hg.
The newly developed method for determining trace elements in nails and hair is reliable, although further efforts are needed to standardize and harmonize results between different laboratories, as well as to better understand the influence of hair dyeing and endogenous factors based on a larger number of samples, as current study results have been inconsistent.
|
