Overview
Alizadeh, Balali-Mood, Mahdizadeh, and Riahi-Zanjani measured total mercury and total lead in 32 bar-soap samples purchased from the Mashhad, Iran retail market in 2016, spanning four anonymized cosmetic-soap brands, five anonymized hygiene-soap brands, and two anonymized contraband-soap product lines. All values were below the FDA cosmetic-material comparators of 1 µg/g for mercury and 20 µg/g for lead the authors invoke. Contraband-soap mercury was significantly higher than cosmetic (P<0.01) and hygiene (P<0.05) soap mercury. The paper also reports a within-hygiene-category significant difference between brands P and T, but the source narrative and Table 3 disagree on whether the contrast is in lead or mercury (see Verification notes). The highest mean mercury was reported for one of the two contraband lines (0.39 µg/g) and the highest mean lead for the P hygiene brand (0.36 µg/g).
Key numbers
All concentrations are in µg/g (= mg/kg) of finished soap as purchased. The FDA comparators the source invokes for soap and cosmetic materials are 1 µg/g for mercury and 20 µg/g for lead.
Overall category means (Table 1; mean ± SEM)
| Soap category | n samples | Pb (µg/g) | tHg (µg/g) |
|---|---|---|---|
| Cosmetic | 12 | 0.10 ± 0.01 | 0.02 ± 0.004 |
| Hygiene | 15 | 0.19 ± 0.04 | 0.08 ± 0.013 |
| Contraband | 5 | 0.13 ± 0.04 | 0.23 ± 0.122 |
Contraband mercury was significantly higher than cosmetic (P<0.01) and hygiene (P<0.05) soap mercury. Lead differences across the three categories were not statistically significant.
Cosmetic-soap brands (Table 2; mean ± SEM, n=3 per brand)
| Anonymized brand | Pb (µg/g) | tHg (µg/g) |
|---|---|---|
| F | 0.12 ± 0.020 | 0.016 ± 0.006 |
| D | 0.08 ± 0.003 | 0.03 ± 0.005 |
| S | 0.08 ± 0.006 | 0.013 ± 0.003 |
| L | 0.12 ± 0.012 | 0.03 ± 0.011 |
No significant differences across cosmetic brands.
Hygiene-soap brands (Table 3; mean ± SEM, n=3 per brand)
| Anonymized brand | Pb (µg/g) | tHg (µg/g) |
|---|---|---|
| P | 0.36 ± 0.205 | 0.14 ± 0.026 |
| Y | 0.14 ± 0.006 | 0.07 ± 0.028 |
| T | 0.12 ± 0.014 | 0.03 ± 0.011 |
| G | 0.21 ± 0.027 | 0.11 ± 0.018 |
| A | 0.12 ± 0.035 | 0.08 ± 0.003 |
Significant P-vs-T contrast (P<0.05): the source’s prose describes this as a lead contrast, but the asterisk in source Table 3 is printed on the mercury column. The contradiction is preserved here rather than silently resolved (see Verification notes).
Contraband-soap lines (Table 4; mean ± SEM)
| Anonymized line | n | Pb (µg/g) | tHg (µg/g) |
|---|---|---|---|
| Contraband-A | 2 | 0.19 ± 0.105 | 0.39 ± 0.320 |
| Contraband-B | 3 | 0.09 ± 0.003 | 0.12 ± 0.032 |
No significant differences between the two contraband lines.
Methods (brief)
Soap samples were purchased from the Mashhad retail market in 2016. Lead was measured by atomic absorption spectrometry with graphite furnace on a Perkin Elmer model 3030 instrument. Total mercury was measured by a mercury/hydride system; the source does not explicitly state whether the mercury/hydride system is integrated with the Perkin Elmer 3030 or is separate instrumentation. Method reliability was evaluated by spiking five samples and computing recovery, detection limit, and accuracy; reported accuracy was 98.4% for mercury and 99.4% for lead. Statistical analyses used SPSS for Windows version 11.5 with a P<0.05 significance threshold; values are reported as mean ± SEM. The paper does not report numerical LOD or LOQ values, does not separate mercury species (results are total mercury), does not state per-brand sample counts explicitly for the hygiene category (presumed three samples per brand by parallel with the cosmetic-category statement), and does not report digestion procedure detail.
Implications
Certification: Provides finished-product lead (Pb) and total-Hg occurrence values for an anonymized Iranian-market bar-soap panel. The usable concentration basis is finished product as purchased; the values are not food-occurrence data and should not be routed into dietary benchmark pools. All values are well below the 1 µg/g mercury (Hg) and 20 µg/g Pb FDA cosmetic-material comparators the source invokes.
Courses: A compact example of a single-market personal-care heavy-metal panel, illustrating how contraband or unregistered soap categories can carry meaningfully higher mercury than registered cosmetic and hygiene lines in the same market even when all values remain below a regulatory cosmetic-material comparator.
App: Supports Iran-market personal-care context for bar soaps. Because the source reports a small panel (n=32) with anonymized commercial brands, app use should frame the values as a small surveillance study, not a national distribution.
Microbiome: Not addressed.
Related evidence
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