New research has challenged beliefs about “safe” times to be in the sun, with the total dose found to be more important.
A landmark QIMR Berghofer study has shown that a short time outdoors during hours of low sunlight can cause skin damage and contribute to a person’s skin cancer risk.
The findings go against decades of conventional thinking that time outdoors early or late in the day does not cause harm.
The study’s co-lead Professor Rachel Neale said 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.
“You can get the same dose of UV radiation in a short time in the middle of the day, or a long time earlier or later in the day,” Professor Neale said.
“Our research has shown it’s the total dose that is important – it doesn’t matter how long it takes to get it.
“People potentially get lulled into a (false) 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 back was exposed to ultraviolet rays, delivered at low (mid-morning equivalents) and high (lunchtime equivalents) UV intensities over several days.
Biopsies were taken to see if any DNA damage had occurred, and they also measured molecular and immune responses.
The researchers said they were surprised to see DNA damage – irrespective or whether the UV radiation was given quickly or more slowly.
Importantly, the doses given were not enough to cause the skin of participants to become pink, but they did cause detectable DNA damage.
Study co-lead Professor David Whiteman said that, over time, episodes of incremental, incidental UV exposure had a cumulative impact on the skin which could lead to mutations that would initiate skin cancer.
The researchers say their work reinforces the idea of using sunscreen as part of a daily habit, to protect the skin when exposed for short, unexpected periods of sun exposure.
The study was published in Photochemistry and Photobiology and is available here.
