Keep slapping it on: fears over sunscreen nanoparticles unfounded

A festival worker hands out sunscreen to the crowd at the Big Day Out in Sydney. AAP/Dan Himbrechts

Human skin can tolerate the tiny metal oxide nanoparticles found in some sunscreens just as well as larger and organic alternatives, the latest tests by RMIT University researchers show.

The finding comes despite evidence that many Australians feel it is safer to avoid sunscreen altogether than subject themselves to the supposed dangers of nanoparticles.

Debate over the safety of nanoparticles, which are smaller than 100 billionths of a metre, has been spurred by research suggesting they can cross the human placenta, and even affect DNA without making contact.

The particles are so small that they do not reflect sunlight, making the lotion appear clear on the skin.

An online poll of 1000 people by the Department of Industry, Innovation, Science, Research and Tertiary Education found that one in four people felt it was safer to use no sunscreen at all than nanoparticle-based lotion.

But research by RMIT University’s Nanosafety Research Group showed that human cell test systems can tolerate the miniscule zinc oxide and titanium dioxide particles as well as zinc ions and conventional chemical sunscreens.

RMIT University toxicologist, Associate Professor Paul Wright, said that Australia has “the highest rate of skin cancer in the world and it is important that people use the most protective sunscreens available.

"The most effective broad spectrum UV blockers are the physical blockers, such as the metal oxides zinc oxide and titanium dioxide, which both absorb and reflect UV, don’t break down under UV exposure and are longer-acting than organic UV blockers.”

Professor Wright’s team presented its research at the International Conference on Nanoscience and Nanotechnology in Perth last week.

For their tests, they used in vitro human skin and immune cell systems to compare the effects of sunscreen components in the presence of ultraviolet light.

Toxicity from zinc oxide particles was only seen at extremely high doses that would not be achieved from sunscreen use, they found.

“Nano-sized metal oxides absorb UV light better as particle size gets smaller, and have the added advantage of a transparent appearance,” said Professor Wright. “It is important to weigh up the known risk of skin damage from excessive UV exposure, with the diminishing perceived risk of using nano sunscreens.”

The consumer group CHOICE has said that lotions which contain nanoparticles should be proven safe before being allowed on to the market, and last year the Victorian branch of the Australian Education Union passed a resolution trying to ban them in schools.

But Professor Wright said that “the RMIT research, along with recent studies by others reporting that there is negligible penetration of these nanoparticles through human skin, indicate that nano sunscreens should continue to be used as part of the SunSmart program to reduce skin cancer incidence.”