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Earth Sense: Responses to sunlight vary by country
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Some cultural differences are subtle. Others are highly visible; for example, the way in which people treat sunshine.

The first sunny day during my stay in China’s megacity Hefei had me surprised. Countless people, mostly women, were wearing surgical-style face masks. On the university campus as well as downtown, others were using umbrellas, or holding up magazines and pocketbooks to shield against the sun.

The masks first misled me into thinking “air pollution.” Industrial combustion and automobile exhaust produce oxides of nitrogen and hydrocarbons. These substances react with sunlight, and a series of chemical processes then produces the harmful ingredients in smog.

But the air was actually quite good, and air pollution wasn’t the concern that got people to “mask up.” It was the sunshine. I talked to a number of students about it, and they declared unanimously that they were trying to keep the sun off their faces, to avoid tanning as well as sunburn.

In China, the majority values pale skin as an aesthetic goal, not the deep tan that is favored on our side of the Pacific. One indicator is the absence of tanning salons. The other is the skin-lightening makeup worn by women at formal events.

Beauty considerations aside, sunlight has good as well bad effects on humans. Specifically, it’s the ultraviolet component, a set of invisible wavelengths, that the body needs for healthy bones.

When UV strikes the skin, vitamin D is manufactured, which is necessary for the absorption of calcium into the skeleton. Deficiency of this vitamin can result in thin, brittle bones. The U.S. National Institutes of Health states that 5 to 30 minutes of sunlight taken twice a week should be sufficient for most people. Sitting behind a window or working in a greenhouse will make a person feel warm, but does not help produce vitamin D because glass filters out the ultraviolet radiation.

Conversely, too much sunlight is harmful to the skin. A burn is painful and unsightly, but the real danger is skin cancer. The most common type, basal cell carcinoma, can be treated with surgery.  

But there’s a bad cousin which spreads into body organs and kills 8,000 Americans per year: malignant melanoma.

These facts put people practicing “total cover” and those preferring “deep tanning” on opposite sides of the scale.

As is so often the case, the healthiest solution is probably in the middle.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.

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