A new Australian study highlights the effects of ultraviolet (UV) radiation on the skin, and re-evaluates the prevailing belief about the safety of sun exposure during the early morning and late afternoon.
The study was conducted by researchers from the QIMR Berghofer Institute, who concluded that the most important factor in skin damage is the total dose of ultraviolet radiation a person is exposed to, and not just the intensity of the radiation or the duration of exposure.
Professor Rachel Neal, who co-led the study, said the research is the first of its kind in Australia to examine the effect of naturally occurring levels of ultraviolet radiation on the Earth's surface in causing biological changes within skin cells.
She added: "The same dose of ultraviolet radiation can be obtained during a short period in the middle of the day or during a longer period in the early morning or late afternoon. Our research has shown that the total dose is the deciding factor, regardless of the duration of exposure."
She explained that the decrease in the intensity of sunlight may give some people a false sense of security, causing them to spend more time outdoors without taking precautions, which can lead to skin damage.
The study included 58 participants with fair to olive skin tones. Researchers exposed one area of their backs to low doses of ultraviolet radiation, similar to what a person is exposed to in the middle of the morning, and another area to higher doses similar to midday levels, over a period of several days.
The research team took skin biopsies to examine for DNA damage, along with measuring molecular and immunological indicators related to the skin's response to ultraviolet radiation.
The results showed DNA damage in participants regardless of whether the radiation exposure was rapid or gradual. The doses used, although not sufficient to cause skin reddening, also resulted in significant damage at the cellular level.
The researchers also focused on measuring levels of the p53 protein, which rises when skin cells are stressed or DNA is damaged, along with monitoring UV-induced DNA lesions as early indicators of skin damage.
Professor David Whitman, one of the study's leaders, said that damage to skin cells does not necessarily mean skin cancer, but it could be the beginning of changes that accumulate over time.
He added: "Our results show that small, repeated doses of ultraviolet radiation cause damage to the DNA of skin cells, enough damage to trigger a cellular response. As this exposure continues over months or years, mutations may accumulate that increase the risk of skin cancer."
The researchers pointed out that the study's findings do not mean that sunlight should be avoided altogether, as it is essential for vitamin D production and general health, but they support updating sun protection guidelines based on scientific evidence, rather than traditional assumptions about the safety of certain times of day.
They also stressed that using sunscreen should be part of the daily routine, even during short, unplanned periods of sun exposure, to help reduce the buildup of damage that can affect the skin over time.
