In a conference abstract, Gulson and colleagues summarise their outdoor trial in which 20 adults applied sunscreens made with zinc oxide enriched to more than 99 % in the stable isotope 68Zn, as 19 nm nanoparticles or particles above 100 nm. Almost all applied zinc was not absorbed, but every subject showed small increases in tracer zinc in blood and urine. After five days the tracer in blood was about one thousandth of total blood zinc and kept rising after application stopped.
Key numbers
- n = 20 adults; 5 consecutive days outdoors; blood and urine 8 days before, twice daily during, and 6 days after (PDF p. 1).
- Tracer 68Zn in blood after the application period: “~1/1000th that of total Zn in the blood compartment” (PDF p. 1).
- Females using the nano sunscreen appeared to have higher 68Zn in blood and urine than males on the same product and than all subjects on the bulk product.
Methods (brief)
Stable-isotope tracing with multi-collector mass spectrometry of zinc purified from blood and urine. Corresponding author: brian.gulson@mq.edu.au.
Evidence fitness
Direct human evidence that some zinc from zinc oxide sunscreen reaches the circulation under real use in adults. It cannot tell whether zinc crossed as particles or ions, and it says nothing about impurity metals. The data are the same trial as Gulson et al. 2010 (Toxicological Sciences 118:140-149) and should not be counted twice.
Limitations
Abstract only, adults only, no infant data. The PDF carries conflicting page labels, and Crossref gives no page range.
Related evidence
- Opinion on Zinc oxide (nano form), COLIPA S 76
- Support for the Safe Use of Zinc Oxide Nanoparticle Sunscreens: Lack of Skin Penetration or Cellular Toxicity after Repeated Application in Volunteers
- Zinc
Update history
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