Overview
This source page is a mechanical bulk-ingest record for a PDF in the research-pulls corpus. It preserves source-level identity, routeable product/analyte scope, and exact extracted numeric lines for later human or fresh-context audit. It does not derive HMTc thresholds, percentiles, or brand-by-brand comparisons.
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:
- controls for blood (0.20 vs. 0.02 µg/L), hair (0.26 vs. 0.03 µg/g), and nails (0.19 vs. 0.02 µg/g) (all
- metal concentrations attributable to industrial effluents and processing steps, indicating plausible Hg sources in this ecosystem (7). Field
- to ensure recovery within ±10% of target values (16).
- participant group status during ICP-OES readings. Quality control included duplicate analysis of 10% of samples, inclusion of procedural blanks,
- and use of freshly prepared reagents to prevent cross-contamination. Missing data were rare (<5%) and handled by pairwise deletion to preserve
- 0.05, and 80% power, yielding a minimum of 45 participants per group; recruitment was expanded to 120 workers and 60 controls to improve
- 95% confidence intervals were reported, and p-values < 0.05 were considered statistically significant. Sensitivity analyses were performed
- among workers was 9.6 ± 5.2 years, and 41.7% reported consistent use of personal protective equipment (PPE). Smoking prevalence was higher
- among workers (38.3%) compared with controls (20.0%), a difference that reached statistical significance (p = 0.018).
- Table 1. Demographic and occupational characteristics of study participants
- Variable Leather workers (n = 120) Controls (n = 60) p-value 95% CI or effect size (d)
- concentrations were significantly higher in workers than in controls across all matrices (p < 0.001). The median Hg concentration in workers’
- blood was 0.20 µg/L (IQR 0.01–0.54), compared with 0.02 µg/L (IQR 0.00–0.05) in controls. In hair samples, workers had 0.26 µg/g (IQR 0.02–
- distributions are presented in Table 2, with corresponding non-parametric Mann–Whitney U statistics, effect sizes (rank-biserial r), and 95%
- Table 2. Mercury concentration in blood, hair, and nail samples of leather workers and controls
- Table 3. Spearman correlations of mercury concentrations among blood, hair, and nail matrices (all participants, n = 180)
- Matrix 1 Matrix 2 Spearman ρ p-value 95% CI for ρ
- When compared with internationally accepted biological exposure limits (BEIs) for non-occupational populations—blood < 0.05 µg/L; hair < 0.10
- Table 4. Frequency and proportion of participants exceeding biological exposure limits for mercury
- Matrix BEI Threshold Workers n (%) above limit Controls n (%) above limit χ² (df = 1) p-value Odds Ratio (95% CI)
Methods (brief)
- concentrations in blood, hair, and nail samples of leather-industry workers in Sialkot, Pakistan,
- 120 male tannery workers and 60 non-industrial controls. Blood, hair, and nail samples were
- collected, cleaned, acid-digested, and analyzed using inductively coupled plasma–optical emission
- spectrometry (ICP-OES). Data were analyzed in SPSS using nonparametric tests and Spearman’s
- Mercury, Biomonitoring, Leather Industry, Occupational Exposure, Hair, Nails, Sialkot, ICP-OES.
- For quantification in these matrices, inductively coupled plasma–optical emission spectrometry (ICP-OES) provides accessible multi-element
- capability with adequate sensitivity for occupational studies when paired with rigorous digestion, calibration, and quality control (12).
- collection, pre-analytical cleaning, and ICP-OES analytics. Prior regional research has emphasized chromium or focused on pediatric/para-
- (1,4,7). Accordingly, in a cross-sectional study of Sialkot tanneries, we aim to quantify Hg concentrations in blood, hair, and nail samples from
- hair, and nail samples were obtained during a single session in the morning hours to standardize diurnal variation. Blood (5 mL) was collected by
- region using ethanol-sterilized stainless-steel scissors, while fingernail clippings were collected after participants washed their hands with
- medicated soap and rinsed with deionized water. All samples were labeled, stored in acid-washed polyethylene containers, and transported in cold
- To remove external contaminants, hair and nail samples were sequentially washed three times with deionized water, once with acetone, and again
- with deionized water, then oven-dried at 110 °C for one hour. Each matrix was subjected to acid digestion using nitric acid and hydrogen peroxide
- at a 2:1 ratio under controlled heating until clear solutions were obtained. Blood digestion involved combining 500 µL of whole blood with nitric
- using inductively coupled plasma–optical emission spectrometry (ICP-OES; PerkinElmer, Analyst-200) with calibration against multi-point
- measurement bias, identical sample collection and digestion protocols were used for both worker and control groups, and analysts were blinded to
- participant group status during ICP-OES readings. Quality control included duplicate analysis of 10% of samples, inclusion of procedural blanks,
Implications
This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.
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Verification notes
- Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing
wiki/sources/pages before creation. - Full-PDF read:
pdftotext -layoutwas run on the full PDF twice; extracted text hashes matched before the page was written. - Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
- Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
- HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.
Update history
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