New research challenges beliefs about ‘safe’ times to be in the sun

A QIMR Berghofer study has revealed that short periods outdoors during hours of low sunlight can cause skin damage and contribute to skin cancer risk.

The findings go against decades of thinking that time outdoors early or later in the day doesn’t cause harm.

Co-lead of the study, Professor Rachel Neale, says the research was the first in Australia to investigate the effects of exposing the skin to UV radiation at levels that occur naturally on the Earth’s surface. The paper is published in the journal Photochemistry and Photobiology.

“You can get the same dose of UV radiation in a short time in the middle of the day or a longer time earlier or later in the day. Our research has shown it is the total dose that is important—it doesn’t matter how long it takes to get it,” Neale said.

“People potentially get lulled into a sense of security when the intensity of sunlight is weak and they spend too long outdoors without adequate protection. We have shown that is a problem for skin damage.”

The Low-Dose UV Study involved 58 people with light to olive skin. An area on their backs was exposed to ultraviolet rays, delivered at lower (e.g., midmorning) and higher (e.g., lunchtime) UV intensities over several days. Biopsies were taken to see whether any DNA damage had occurred, and researchers also measured molecular and immune responses.

The researchers say they were surprised to see DNA damage, regardless of whether the UV radiation was given quickly or more slowly. Importantly, the doses given were not enough to cause participants’ skin to become pink, but even so, these low doses caused detectable damage to the DNA.

While sunlight is essential for vitamin D and overall health, it is also a complete carcinogen, meaning it can both initiate and promote cancer. Current guidelines suggest people take sun-smart actions (slip, slop, slap, seek, and slide) when the UV index is 3 or above.

The Low-Dose UV Study examined molecular markers that act as early alarms for skin damage, long before cancer could ever develop. The researchers measured p53, a protein that increases when skin cells are under stress or DNA is damaged, as well as UV-induced DNA lesions.

Study co-lead Professor David Whiteman AM says while the skin has experienced some damage from the UV exposure, it doesn’t mean that cancer has formed.

“Our lab results show these small, incremental doses of UV have caused some damage to the DNA in the skin cells, enough for the cells to then respond to the damage. Over months and years, these episodes of incremental, incidental UV exposure will have a cumulative impact on the skin and can lead to mutations that will initiate skin cancer,” he said.

The researchers stress that their findings are not about avoiding sunlight altogether—but about updating sun safety advice to reflect biological evidence rather than assumptions.

“Our aim is to give Australians accurate, trustworthy guidance,” they say. “That starts with understanding whether the sunlight we consider ‘safe’ is truly risk-free at the cellular level.”

They say the work reinforces the idea of using sunscreen as part of a daily habit to protect the skin during short, unexpected periods of sun exposure that happen as part of daily life.

Who’s behind this story?

Advertisements

Gaby Clark

MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news.

Full profile →

Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

Full profile →

See also  Taurine in energy drinks may fuel blood cancer growth, new research reveals