Gulson and colleagues used stable zinc isotopes to estimate how much zinc from a zinc oxide sunscreen passed through adult skin. The pilot used about 30 nm zinc oxide enriched to 52 percent 68Zn, applied twice daily for five days in winter without ultraviolet exposure. The authors describe absorption as minimal, on the order of 0.01 percent of the applied dose. Zinc here is the ultraviolet filter, not a heavy-metal impurity.
Key numbers
The abstract clause reads that absorption was minimal (0.01 percent of the applied dose) through the skin. A less-than glyph has been reported in front of 0.01 percent in some readings of this PDF. The token verified in the text layer for this ingest is 0.01 percent of the applied dose. Figures of 6 to 31 µg cited from the authors’ earlier outdoor work, and a blood tracer range that was not re-found as a new pilot result, are not repeated as measurements from this pilot.
Methods (brief)
Stable-isotope tracing in three adults. The formulation is zinc oxide, so the product route is mineral sunscreen. The paper does not identify the users as infants.
Evidence fitness
The pilot supports a qualitative dermal-absorption statement for zinc from zinc oxide sunscreen in adults. It does not support lead, cadmium, or other impurity metals, and it does not support a baby-sunscreen row.
Limitations
n = 3. No ultraviolet exposure in the pilot. The 0.01 percent figure is an estimate of absorbed zinc, not a concentration in the product.
Related evidence
Update history
No substantive edit history is available in this build. The full commit record is available in git.