to Heavy Metal Exposure of Children Around Smelting Area

Overview

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hand-loaded dust (64.3%) was significantly higher than that in ambient soil, demonstrating
ingestion in children. Soil particles with a size of <63 µm contributed 48–60% to the total
concentration of heavy metal in soil within a single particle-size range (e.g., the <150 µm
that particles < 63 µm accounted for 81.7% of the total mass of soil adhered to children’s
hands (24). Bergström et al. also noted that over 60% of the adhered particles had a
250–352 µm), the arithmetic mean of the mass fractions from the 30 children was calculated.
These mean values were then normalized to sum to 100% to obtain the pooled particle
(D50) for the study population was calculated as the arithmetic mean of the 30 individual
lene (PTFE) digestion vessel. Then, 6 mL of nitric acid (HNO3 , 68%, ρ ≈ 1.42 g/mL), 3 mL
turers, is provided in Table S2. Ultrapure water (resistivity > 18 MΩ·cm) was prepared in
Table S3. The concentrations of Cd, Cr, Cu, Ni, and Pb in the filtrate were determined using
Clara, CA, USA). Each soil sample was digested in triplicate (n = 3 analytical replicates).
stock standard solution (1000 mg/L, National Institute of Metrology, Beijing, China) with
5% HNO3 . A six-point calibration curve was established for each metal at concentrations of
0, 1.0, 5.0, 10.0, 20.0, and 50.0 µg/L. The linearity of the calibration curve was evaluated by
the relative percent difference was maintained below 10%. Internal standards (72 Ge, 115 In,
detection (LOD) for Cd, Cr, Cu, Ni, and Pb were 0.03, 2.00, 0.70, 2.00, and 1.00 mg·kg−1 ,
in Table S4. The ultrapure water (resistivity > 18 MΩ·cm) used was prepared in-house.
The PBET assay was performed in triplicate for each soil sample (n = 3 experimental
(mg·kg−1 ); BAi is the bioaccessibility of the target metal in soil in the i-th particle size range,
assessed using the Anderson-Darling test (Table S5). Correlations among input parameters
were not explicitly considered in the primary analysis due to the limited sample size (n = 17)
used, all containers were acid-washed, and duplicate samples (accounting for 10% of each
the method. The recoveries of Cd, Cr, Cu, Ni, and Pb were 93.6%, 97.5%, 102%, 106%, and
99.5%, respectively. All recovery rates were within the acceptable range of 85–115%. For
and the relative deviations were maintained below 10% for recalibration checks and 30%
by 1/ 2 of the detection limit. All results are reported as the mean ± standard deviation
was consistently below 10%, and the coefficients of variation in parallel samples were all
below 5%, indicating good reproducibility and that the analytical precision met the quality
from 0 to 352 µm, with a median particle size of 46.5 µm. Particles smaller than 63 µm
constituted the largest fraction, accounting for 64.3% of the total mass. Particles with
0.490%, respectively, with the last group showing the smallest proportion. The median
particle size of hand-loaded dust measured in this study fell within the range (33–150 µm)
particles <63 µm, 63–150 µm, and 150–250 µm accounting for 44.6%, 30.9%, and 14.9% of
ranges: Cd (0.06–99.1 mg·kg−1 ), Cr (11.4–287 mg·kg−1 ) (27), Cu (33.7–587 mg·kg−1 ), Ni
range (<250 µm), but decreased significantly in the coarse particle size range (250–352 µm).
of <250 µm, and then tended to stabilize. This trend was mainly attributable to the
Ni, and Pb in the gastric phase were 49.1%, 9.93%, 32.1%, 14.9%, and 24.1%, respectively.
During the intestinal phase, these values decreased to 26.3%, 8.61%, 28.0%, 12.6%, and
20.1%, respectively. In general, Cd and Cu exhibited significantly higher bioaccessibility
dominated by stable forms, such as Cr, exhibit low desorption potential (10). The transition
range. For Ni and Cr, bioaccessibility decreased slowly within the <250 µm fraction and

Methods (brief)

Soil samples were collected from the residential courtyards of these children, as these
17 surface soil samples were collected, corresponding to the 30 participating children. In
sharing a common courtyard, a single composite soil sample was collected to represent
2.2. Sample Collection and Pretreatment
Hand-loaded Dust: Hand-loaded dust samples were collected using an ultrapure
Soil: Surface soil (0–5 cm) was collected from the courtyards where children reside,
A total of 17 composite soil samples were collected, corresponding to the 30 children,
with multiple children sharing a common courtyard represented by a single sample. All
geographical positioning of the sampling points. At each sampling point, four subsamples
were collected within a 5 m radius and combined to form a composite sample. Visible
impurities such as plant roots and leaves were removed, and the samples were then passed
dust, the soil samples were first passed through a 352 µm nylon sieve. This matched the
collected separately for subsequent analysis of metal concentrations and bioaccessibility.
was determined by the loss-on-ignition method, where oven-dried soil samples were
Wei et al. (29). Briefly, 0.15 g of each soil sample was weighed into a polytetrafluoroethy-
lene (PTFE) digestion vessel. Then, 6 mL of nitric acid (HNO3 , 68%, ρ ≈ 1.42 g/mL), 3 mL
microwave digestion, including chemical formulas, purity, specifications, and manufac-
our laboratory. The sealed vessels were subjected to microwave digestion (MARS-5, CEM

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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