University of Michigan research calls for 'better sunscreens'

11-Dec-2013 - Last updated on 10-Dec-2013 at 15:34 GMT

UM scientists have found that even low levels of exposure to ultraviolet A1 or UVA1 can cause damage at the molecular level after just a few days.

The new research on the less-studied but ever-present UVA1 rays in natural sunlight and tanning booths shows just two daily exposures can kick start skin-ageing process.

The study, published in JAMA Dermatology, outlines how the team measured the effects of UVA1 at the molecular level using advanced gene expression analysis of skin samples from human volunteers.

According to the researchers, the new findings suggest a need for new sunscreen ingredients that can protect against UVA1 rays.

Currently, only zinc oxide and avobenzone are approved by the US FDA as sunscreen ingredients capable of blocking UVA1. Window glass, and most clothing, also don’t necessarily filter out all UVA1.

The current study didn’t assess the impact of UVA1 on genetic changes that can lead to skin cancers, other forms of UV are firmly linked to most types of cancerous skin lesions.

Study focuses on lesser UV exposure

According to first author Frank Wang, M.D., premature skin ageing from UV exposure has gotten a lot of attention in the last 10 years, but most researchers have focused on UVB rays, which cause sunburn.

"So, we wanted to look at whether it can predispose skin to premature aging by simulating repetitive daily exposure. And we found that it can. Furthermore, the mild tanning that occurs does not seem to protect against damage from additional exposures,” he explains.

Firstly, the researchers shined a low level of pure UVA1 rays, as might be encountered in daily life, on small areas of 22 volunteers’ buttocks. A day later, they measured changes in skin pigmentation before taking tiny samples of skin, in order to detect which genes had been ‘turned on’ by the light exposure, repeating the process three more times on each participant.

The study exposed the fair-skinned volunteers in a repeat manner to the amount of UVA1 they would receive in about two hours of strong sun exposure. Statistical analysis showed the pattern of MMP1 production increased progressively with repeated exposure in the majority of patients.

Reference: JAMA Dermatology online publication, DOI: 130084pap