NEPA Vital Signs - Summer Fall 2018 - 11

SUMMER/ FALL 2018

AND OUR SKIN

The sunlight that reaches the earth consists of visible light and
ultraviolet (UV) radiation; the invisible ultraviolet rays cause
suntans and sun-induced skin injuries. The amount of ultraviolet light reaching the skin depends on a number of factors. For
example, the lower the latitude, the greater the risk of sun damage
to the skin at any given hour. A noontime sunbather in Miami
will experience a heavier dose of burning rays than a noontime
sunbather in Boston. The time of greatest risk anywhere in the
world occurs in the middle of summer between the hours of
10 am and 2 pm.

Environmental factors may also enhance one's chances of
sunburn. Beach sand, snow, and shiny metal (as in sun reflectors)
markedly increase the dose of solar radiation. Other factors may
fail to offer adequate protection. Water is not an efficient sun
blocker; burning and tanning rays can penetrate beneath the
surface of a pool. Many people sunburn on overcast days. Fooled
by the lack of visible light, they do not take adequate protection,
unaware that invisible ultraviolet radiation still reaches the skin.
In fact, 70 percent of the sun's rays penetrate clouds and fog.
Ultraviolet radiation is divided into UVA and UVB. UVA constitutes over 90 percent of the radiation penetrating to the earth's
surface. UVA can also penetrate the skin's surface and has been
implicated in suppression of the immune system. UVB causes damage to the epidermis, this resulting in the acute sunburn. Chronic
ultraviolet light exposure induces wrinkles and other signs of
cutaneous aging. UVB is filtered by window glass, but UVA is not.

Seasonal variations and altitude also play a role in the amount
of ultraviolet light striking the skin. One will experience a more
severe suntan in early May than at the end of August. The higher
the altitude, the less atmosphere is present to filter out ultraviolet
rays, a contributing factor to the marked sunburns often seen
in winter skiers.

N E PA

VITAL SIGNS

Table of Contents for the Digital Edition of NEPA Vital Signs - Summer Fall 2018