Larese Filon and colleagues measured lead oxide powder crossing human skin in vitro, and how two skin cleansers changed that passage. The work is an occupational dermal study. It is not a measurement of lead in a food or a cosmetic.
Key numbers
Skin from 14 donors was mounted in Franz cells. Lead oxide was applied at 5 mg/cm2. Synthetic sweat was at pH 5.0. Lead in the receiving cells and in the skin was measured by electrothermal atomic absorption spectrometry (NIOSH method 7105). Tables 1 and 2 report blank-adjusted medians in ng/cm2, with the 25th percentile, 75th percentile, minimum, and maximum.
Receiving cells, blank-adjusted median (25th, 75th, minimum, maximum):
| Experiment | Condition | Median | 25th | 75th | Minimum | Maximum |
|---|---|---|---|---|---|---|
| 1 | Intact skin, no wash, 24 h | 2.9 | 0.35 | 6.0 | 0.2 | 10.9 |
| 2 | Intact skin, liquid soap | 23.6 | 12 | 47.1 | 4.3 | 88.0 |
| 3 | Intact skin, second cleanser | 7.1 | 5.8 | 10.0 | 2.8 | 13.8 |
| 4 | Damaged skin, no wash, 24 h | 26.8 | 15.7 | 36.4 | 6.5 | 143.9 |
| 5 | Damaged skin, liquid soap | 100.2 | 83.2 | 132.7 | 31.8 | 139.3 |
| 6 | Damaged skin, second cleanser | 35.9 | 30.0 | 45.4 | 19.0 | 48.0 |
Skin content, blank-adjusted median (25th, 75th, minimum, maximum):
| Experiment | Condition | Median | 25th | 75th | Minimum | Maximum |
|---|---|---|---|---|---|---|
| 1 | Intact skin, no wash | 321.3 | 243.3 | 528.3 | 191.4 | 833.2 |
| 2 | Intact skin, liquid soap | 19.7 | 11.3 | 34.6 | 4.7 | 147.7 |
| 3 | Intact skin, second cleanser | 10.5 | 6.2 | 19.3 | 4.5 | 41.8 |
| 4 | Damaged skin, no wash | 296.9 | 165.1 | 716.7 | 46.3 | 1933.3 |
| 5 | Damaged skin, liquid soap | 135.6 | 77.0 | 224.3 | 66.0 | 348.0 |
| 6 | Damaged skin, second cleanser | 19.7 | 7.3 | 69.7 | 5.2 | 118.3 |
With no cleanser, lead remaining in the skin was similar in intact and damaged skin (321 and 297 ng/cm2 in the prose). Experiments 2 and 5 used a liquid soap. Experiments 3 and 6 used a second cleanser described as a NIOSH formulation. The soap brand is not repeated here.
The authors then project blood lead with the Adult Lead Model. These figures are modelled, not measured. For unwashed skin the steady-state increase is 0.7 (0.1, 1.4), 2.5 (0.3, 5.1), or 3.6 (0.4, 7.4) µg/dL for hands, hands and arms, or hands, arms, head, and neck, assuming 5 mg PbO/cm2 for 250 days per year. The parenthetical pairs are the interquartile range. For skin washed with the surfactant soap the corresponding projections are 5.4 (2.8, 10.8), 20.2 (10.3, 40.3), or 29.2 (14.9, 58.3) µg/dL.
Methods (brief)
In vitro Franz cells, human skin, lead oxide powder, 24-hour collection, synthetic sweat at pH 5.0, blank cells subtracted. Damaged skin followed an abraded-skin protocol. The blood lead figures are an Adult Lead Model projection from the receiving-cell data.
Evidence fitness
The tables support a statement about lead crossing these skin samples under these six conditions, in ng/cm2. They do not support a concentration in a consumer product. The blood lead figures support only the model run the authors describe.
Limitations
Donor skin in a diffusion cell is not a worker’s blood lead. One cleanser increased passage relative to no wash. That finding is specific to the conditions in the tables. Blank medians are in the paper and are not the blank-adjusted results reported above.
Related evidence
Update history
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