Devices like tablets, smartphones and laptops can reflect ultraviolet light from the sun and may indirectly increase users' exposure to the cancer-causing wavelengths, according to a new study.

"These devices are generally used for communication or entertainment, so it can be easy to overlook their reflective properties unless you happen to catch the glare off a screen," said Mary E. Logue of the University of New Mexico in Albuquerque, who coauthored the research with Dr. Barrett J. Zlotoff.

They wondered whether, like those old-fashioned tanning reflectors, personal electronics could also pose skin health risks, Logue told Reuters Health by email.

In a small observational study conducted on a grassy field in Albuquerque, the researchers set up a mannequin head wearing a UVA/B light meter and faced it toward a standard musician's sheet stand. Then they placed various mobile devices on the stand.

In two trials, the researchers recorded UV readings for an hour of exposure, from 11 AM to noon, using a magazine, an iPhone5, various iPad models, two Macbook laptops and a Kindle e-reader.

In the first trial the devices were 16.5 inches from the UV sensor. For the second, they were secured 12.25 inches away. The devices and the UV sensor were angled to mimic an adult looking down at the handheld device.

The study team measured UVA/B dose exposure from light reflected by the devices in Joules per square centimeter over one hour and compared that to the UV readings with an empty sheet stand.

In the first trial, when the devices were further away from the mannequin, an open magazine increased UV dosage exposure by 46 percent compared to the sheet stand alone, an iPad2 increased exposure by about 85 percent and an 11-inch Macbook increased UV exposure by 75 percent.

Only the second trial, with devices held closer to the mannequin's "face," included the iPhone5, which increased UV exposure by 36 percent, as the researchers reported in the Journal of the American Academy of Dermatology.

"The harmful effects of UVA and UVB rays have been well documented, and limiting exposure is the single most effective preventive measure an individual can take," Logue said. "Significant levels of UV exposure, such as those found in this study, increase cumulative lifetime UV dosage."

Given the increase in UV exposure, there needs to be further research to see if skin cancer risks are affected, she said.

"While the best course of action is to limit smart device usage to the indoors, this is obviously impractical for most people," Logue said. "We recommend covering the shoulders, wearing sunglasses and wearing sunscreen, especially on the exposed areas of the neck and face."

The devices themselves could be redesigned to be less reflective, or to include UV sensor technology so their users could track their exposure, she said.

Dr. Robert Dellavalle, chief of the Dermatology Service at the Denver VA Medical Center, who was not part of the new study, said that while the research did not involve real people using the devices, it still raised a practical point. In real world use, it may be hard to see phone or tablet screens in full sun, and using them may actually encourage shade-seeking behavior, he noted.