Toxic elements are considered a significant threat to public health in oil-producing coun-

Overview

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Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

Mangistau, and Atyrau oblasts by cluster sampling method (Table 1).
1 N = data number. 2 N% = data number percentage. 3 Median (min–max) = median (minimum–maximum
and diluted with distilled deionized water to a concentration of 0.5–1% HNO3 before direct
10 µg/L Ce, Co, Li, Tl, Y in 2% acid (Agilent Technologies, USA) is used for daily evaluation
tions of 0.5, 1, 5, 10, and 5000 µg/L are prepared before starting work from the Universal
MA, USA) by dilution in distilled deionized water acidified with 1% HNO3 . To account
internal standard containing 10 µg/L Rh is prepared from a rhodium reference standard
(#N9300167, PerkinElmer Inc.) on a matrix containing 8% butanol-1 (#1. 00988, Merck
KGaA, Darmstadt, Germany), 0.8% Triton X-100 (Sigma T9284 Sigma-Aldrich, Co., Burling-
ton, MA, USA), 0.02% TMAH (#20932, Alfa-Aesar, Ward Hill, MA 01835 USA) and 0.02%
median (Me), and minimum and maximum values, along with the 2.5th, 25th, 50th, 75th,
adopted for hypothesis testing, with results reported at a 95% confidence interval
The mean age of the study participants was 11 (5; 18) years. 764 (47.9%) of the study
urban areas, 805 (50.5%) and 790 (49.5%) in rural areas (Table 1).
children’s hair in the oil and gas province of Kazakhstan are presented in Table 2. The unit
concentrations did not differ significantly by gender (Table S1, Supplementary Materials).
(Table S1, Supplementary Materials). The age of the children was considered as a numerical
ranged from −0.320 (for Pb) to 0.080 (for Hg). The age of the children was significantly
Table 3 shows the concentrations of Al, As, Be, Cd, Hg, and Pb in the hair of children
Table 3. Comparative analysis of toxic trace element concentrations (µg/g) in the hair of children from
age, sex, BMI, smoking, and urban/rural residence. The results are summarized in Table 4.
To illustrate how this table should be understood, we use the example of As. In model 0, the
regression coefficient of As, 0.066 (95% CI 0.040; 0.092), means that the natural logarithm
setting (urban or rural) in Model E (see Table 4).
Table 4. Evaluation of crude and adjusted differences in hair levels of toxic trace elements: findings from multiple regression analysis.
Median 5.98 (0.00; 2.09 (0.08; Ruiz et al.,
Italy, Median 8.45 5.60
South Median 8.08 (3; 0.11 (0.05– 0.07 (0.01– Park et al.,
Italy, Median 6.09 (0.01; 0.03 (0.01; 0.78 (0.37;
Hg showed clear significant gender differences. As shown in Table S1 (Supplementary
elements content with the age of the children studied (Table S1). All toxic trace elements
proportion of the total number of papers (Table 5). Nevertheless, high concentrations of
cury (MeHg), set at 0.1 µg/kg body weight per day, to protect against developmental
are almost three times higher than in children (Table 5). High hair mercury concentrations
data (medians and ranges) (1,14,22,26,33,41,42,48,50,51). The dark blue color indicates polluted areas,
times higher than our values (Table 3).
areas of East Kazakhstan and Pavlodar regions. J. Trace Elem. Med. Biol. 2019, 56, 31–37. (CrossRef) (PubMed)
1. Crisponi, G.; Fanni, D.; Gerosa, C.; Nemolato, S.; Nurchi, V.M.; Crespo-Alonso, M.; Lachowicz, J.I.; Faa, G. The meaning of

Methods (brief)

Trace Metal and Metalloid Profiles in Hair Samples from
ducted involving 1595 school-aged children. Element levels in hair samples were quantified
Academic Editors: Matteo Vitali and using inductively coupled plasma mass spectrometry (ICP-MS). The association between
Profiles in Hair Samples from (0.064 (CI: 0.039; 0.089), 0.093 (CI: 0.045; 0.141), and 0.244 (CI: 0.202; 0.287), respectively).
Human hair is a useful tissue sample for non-invasive environmental studies (20).
attractive biomaterials because it is easy to collect, store, transport, and prepare samples for
and the use of metal instruments when taking samples for research (22). According to
biomonitoring studies (23). Hair samples are ideal for the analysis of healthy populations
in biological samples (27,29–33). Of particular significance is the focus on the pediatric
We present data on the levels of toxic trace elements in scalp hair samples from
To calculate the sample, we used official data on the number of the general population
inclusion in the study. Exclusion criteria: insufficient hair length to obtain a useful sample,
who were present on the day of sample collection and from those whose parents provided
authorized written permission to participate in the study. A total of 1595 samples were
collected from 30 schools, one school per district. Weight and height were measured, and
System. Precise coordinates for each sampling location were collected using government-
and subsequent amendments. Before parents answered the questionnaire and hair samples
Hair samples were collected by cutting with clean stainless steel scissors from

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised