2018年6月大学英语六级听力常考时文：Sunscreens May Leave Skin Vulnerable to UV

英语自学网

　　1.What can molecules in sunscreens do to the skin over time? They can ...
the skin.
        　　2.What is the correct way to use a sunscreen? To ... on the skin.
        　　3.How often is it recommended to use sunscreens? Every ...
        　　Unless sun lovers continually reapply sunscreen, agents in the sunscreen
itself can attack the skin and leave the body susceptible to ultraviolet
radiation, researchers say. Scientists at the University of California at
Riverside have found that molecules that block UV radiation in sunscreen can,
over time, penetrate into the skin, leaving the outer body vulnerable.Kerry
Hanson, a research scientist in the Department of Chemistry at UCR, said that
sunscreens do an excellent job protecting against sunburn when used
correctly.This means using a sunscreen with a high sun protection factor and
applying it uniformly on the skin. However, Hanson pointed out that their data
showed that if coverage at the skin surface was low, the UV filters in
sunscreens that had penetrated into the epidermis could potentially do more harm
than good. Unprotected skin exposed to UV radiation generates harmful compounds
called reactive oxygen species or ROS. These molecules can react with cells,
membranes and DNA, causing skin damage and signs of aging. Hanson's research
team found that three UV filters widely used in sunscreens generate ROS when
skin is exposed to UV radiation. Only a few UV-filters are capable of blocking
UV-A, the wavelengths that penetrate deeply into the skin. "For now, the best
advice is to use sunscreens and reapply them often — the Skin Cancer Foundation
recommends every two hours, and especially after sweating or swimming, which can
wash away sunscreen — to reduce the amount of UV radiation from getting through
to filters that have penetrated the skin. This, in turn, would reduce ROS
generation." said Christopher Bardeen, an assistant professor of chemistry at
UCR.