According to The Australian and ABC “Geochemist Brian Gulson, of Sydney's Macquarie University, has provided the first conclusive evidence that zinc oxide nanoparticles - which appear in many translucent sunscreens - can be absorbed by the body and remain there for extended periods of time. “ This is certainly an intriguing, but unfortunately not quite accurate reporting, of the conclusion of Gulson’s research. Here’s the entire interview with Dr. Gulson with Ashley Hall of PM. Take special note that Dr. Gulson points to the fundamental failing of the study, which is not about nanoparticles, but about absorption of zinc, which is actually quite harmless.
MARK COLVIN: There have long been concerns that the zinc used in sunscreen could be absorbed through the skin and into the body. A series of studies have shown no evidence of that - until now. Scientists at Sydney's Macquarie University have found that zinc does penetrate the body and that it stays around for extended periods of time although not in big enough amounts to be harmful.
The researchers included controversial zinc nano-particles in their tests, but it's not clear what role, if any, the nano-particles played in the absorption process.
They presented their findings this week at a conference in Sydney on nanotechnology.
Ashley Hall reports.
ASHLEY HALL: Like many significant scientific discoveries, this one began in the most mundane way. About six years ago, the Macquarie University geochemist Brian Gulson was applying sunscreen to his five young grandchildren when a question formed in his mind.
BRIAN GULSON: It appeared to disappear and I suddenly thought gosh it's disappearing and it wasn't just from the small size of the particles, it's disappearing through their skin and where's it going?
ASHLEY HALL: So, along with his team, Professor Gulson formulated two special sunscreens using a traceable zinc oxide isotope. One version contained zinc nano-particles, the other contained larger zinc particles. They applied the formulations to 20 people of various ages, skin types and races over a five day period.
BRIAN GULSON: We collected blood and urine samples before we applied that sunscreen, we actually did that a week before, and then we took blood and urine samples during the time of the trial, five days of the trial, and then we actually had a follow up a week later to collect another blood and urine sample from the people. And we measured the isotopes in a big black box, which separates out different isotopes and you can tell how much penetration there's been.
ASHLEY HALL: Unlike all the earlier studies, Professor Gulson's team found clear evidence that the zinc was being absorbed. Nonetheless he says there's no cause for alarm.
BRIAN GULSON: I guess the critical thing was that we didn't find large amounts of it getting through the skin. The sunscreens contain 18 to 20 per cent zinc oxide usually and ours was about 20 per zinc. So that's an awful lot of zinc you're putting on the skin but we found tiny amounts in the blood of that tracer that we used.
ASHLEY HALL: So is it a significant amount?
BRIAN GULSON: No, no it's really not.
ASHLEY HALL: But Brian Gulson is warning people who use a lot of sunscreen over an extended period that they could be at risk of having elevated levels of zinc.
BRIAN GULSON: Maybe with young children where you're applying it seven days a week, it could be an issue but I'm more than happy to continue applying it to my grandchildren.
ASHLEY HALL: This study doesn't shed any light on the question of whether the nano-particles themselves played a part in the zinc absorption.
BRIAN GULSON: That was the most critical thing. This isotope technique cannot tell whether or not it's a zinc oxide nano-particle that got through skin or whether it's just zinc that was dissolved up in contact with the skin and then forms zinc ions or so-called soluble ions. So that's one major deficiency of our study.
ASHLEY HALL: Where do nano-particles go is one of the big questions that have dogged the rapid rise of nanotechnology and it's not confined to whether they can penetrate the body. Dr Mark Wiesner is a professor of environmental engineering from Duke University in North Carolina who's looking into the environmental impact of nano-materials.
MARK WIESNER: This is really the first case where a major technological system has been rolled out by society where the scientific community has really led the charge in asking the question what might the environmental impacts be?
ASHLEY HALL: As part of his research, Dr Wiesner has set up simulated wetlands to monitor the effect of nano-silver in the environment. Nano-silver is now commonly used in bandages, socks and other clothes because of its anti-bacterial properties.
MARK WIESNER: We knew again that silver was an issue from the outset, and so the methods that we have for dealing with materials that we already know are toxic, like silver, are fairly straightforward. We do the same thing with nano-silver that we did, for example, with silver that was coming off of film and so on in the photographic industry. You limit it at the source.
ASHLEY HALL: Dr Wiesner says what's already become clear is that different nano-materials behave in different ways, so each will have its own hazard profile. But he doesn't agree with calls to stop developing nano-materials until their full hazard potential can be identified.
MARK WIESNER: There's lots of things that we're exposed to every day, like electricity, that in fact we limit the exposure by the kind of plugs we use, by putting insulation around wires and so on, but electricity itself is actually quite hazardous. So we limit the risk by limiting the exposure.
MARK COLVIN: Dr Mark Wiesner, a professor of environmental engineering from Duke University in North Carolina, speaking to Ashley Hall.