Permeability of hair to cadmium, copper and lead in five species of terrestrial mammals and implications in biomonitoring

Abstract

The capacity of mammal hair to absorb toxic metals and its utility in biomonitoring has been broadly studied. Though these metal-binding properties has generally been attributed to the sulphur contained in cysteine, an amino acid that forms part of keratin, there are not many experimental studies that analyze the role of sulphur in the external deposition of potentially toxic metallic elements in order to better understand the potential of hair in biomonitoring and generate better tools for differentiating between internal and external deposition of contaminants. In this study, an experimental analysis is carried out using a scanning electron microscope on hairs of five terrestrial mammal species (Peromyscus furvus, P. maniculatus, Glossophaga soricina, Artibeus jamaicensis and Marmosa mexicana) treated with cadmium, copper and lead salts. We quantified absorbed metals as well as natural elements of the hair by energy dispersive X-ray spectroscopy (EDS) to analyze using simple statistics the role of sulphur in the absorption Cd, Cu and Pb. Given the lack of studies comparing the mechanisms of deposition of metal elements among different orders of Class Mammalia, external morphology was considered to be an important factor in the deposition of metallic particles of Cd, Cu and Pb. Bat species (Glossophaga soricina, Artibeus jamaicensis) showed a high concentration of particles in their scales, however, no between-species differences in metal absorption were observed, and during the exogenous deposition metal particles do not permeate the medulla. These results suggest that the sulphur in hair itself cannot bind metals to hair cuticle and that hair absorption capacity depends on a variety of factors such as aspects of hair morphology.

Concentration of Trace Elements in Raptors from Three Regions of Slovakia, Central Europe

“…Besides soft tissues some toxic elements, for instance, lead, are predominantly measured in bones [18]. On the other hand, metal concentrations in feathers are highly variable and depend on bird species and age, and for that reason some researcher state that feather samples have only low priority for ecotoxicological studies [19,20].…”

Roe Deer (Capreolus capreolus) Hair as a Bioindicator for the Environmental Presence of Toxic and Trace Elements

“…It has also been suggested that the metals’ absorption ability could vary in relation to several aspects, such as different hair morphology in different mammalian species. Hair is an epidermal appendage composed of three layers: the innermost layer called the medulla, composed of columns of keratinized cells; the middle layer called the cortex, in which pigment granules are contained; and the most external layer called the cuticle, composed of plates of cells characteristic for each species [ 21 , 22 ]. The differences between the three layers confer different affinities for compounds; for example, the cuticle contains sulphur, which attributes to hair the ability to absorb metals [ 23 ].…”

“…The differences between the three layers confer different affinities for compounds; for example, the cuticle contains sulphur, which attributes to hair the ability to absorb metals [ 23 ]. Meanwhile, the medulla and the cortex contain little or no sulphur, but both layers are embedded in pigment granules that confer the ability to selectively bind metal elements [ 21 , 22 ]. Due to these peculiar features, fur is a more reliable method for monitoring the trace and toxic elements’ status in the body than blood or urine, which are often affected by the temporary influences of some factors and are not matrices of accumulation [ 24 ].…”

Non-destructive mercury exposure assessment in the Brandt’s hedgehog (Paraechinus hypomelas): spines as indicators of endogenous concentrations

“…In particular, hair i) can be easily collected, stored and transported, ii) can be sampled in a non-invasive manner, allowing the monitoring of threatened and/or endangered species, iii) can incorporate and retain chemicals through the hair follicle, iv) allows the elimination of toxic elements from the body when it grows, and v) can be a good indicator of the amount of Hg in the body, showing high correlation between the metal concentrations in hair and in other organs (Crowe et al 2017;Rendón-Lugo et al 2017;de Castro and de Oliveira Lima 2018;Yamanashi 2018;Eyrikh et al 2020).…”