Safe Sun?
	© Stephen T. Abedon
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	last updated on Friday, January 16, 1998

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"And your new shoes are worn at the heels
and your suntan does rapidly peel
and your wise me don't know how it feels
to be think as a brick."

- Gerald "Little Milton" Bostock (a.k.a.?, Ian Anderson)

Exposure to the sun is the leading contributor to the aging of the skin, the premature aging of the skin, and formation of skin cancers including the incredibly dangerous malignant melanoma. Only you can protect yourself and your children from the harmful effects of unprotected exposure to the sun's rays, and only you can make sure that past exposures to the sun do not result tomorrow in disfiguring and even fatal skin cancers. Bottom line: Protect yourself from the sun at all times but especially during the middle of the day, at high altitudes, low latitudes, and when on snow, water, or sand. Do so by using a broad spectrum, high SPF sunscreen, ultraviolet radiation (UV) filtering sun glasses, clothing made from reasonably thick cloth (especially cotton and not wet), and a wide brim hat (which protects your scalp, your face, the tops of your ears, your eyes, and maybe even the back of your neck).

"The types of energy that are emitted from the sun include radio waves, X rays, infrared rays, visible light, and ultraviolet radiation. Infrared rays, which provide much of the heat on our planet, are not considered harmful, but in combination with wind they can cause the natural moisture in the eyes (and skin) to dry out. . . Ultraviolet radiation---especially UV-A and UV-B (are of much greater concern to the health of your skin and eyes). UV-C is absorbed in the upper atmosphere, but UV-A and UV-B reach the surface of the earth, where UV-A represents 5.5 percent of total solar energy and UV-B represents only 0.5 percent. UV-A can induce sunburn, but not nearly as intensely as UV-B; however, (UV-A) penetrates through three layers of skin and causes long-term damage, including wrinkles and cancer of the skin. UV-B penetrates only the first two layers, but its intensity enables it to cause both immediate and long-term damage. The depletion of the fragile and protective ozone layer, a consequence of artificially prepared chemicals that have been released into the atmosphere, permits much more ultraviolet radiation to reach the earth than in previous times, thus increasing our risk of damage from the sun." (p. 68, Siegel, 1990)

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No entry.

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No entry.

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history ---

the "old" sun ethos:

At one time, in what was mostly an agrarian society, those who could avoid signs of sun exposure and exercise stood apart as individuals who did not have to work at manual labor out of doors.

Status consequently was afforded in part by the lack of a suntan.

In other words, those who could afford to, for perhaps all of the wrong reasons, took what we now know scientifically was good care of their skin through avoidance of exposure to the sun.

a changing sun ethos:

Industrialization changed the demographics of work from one in which a large fraction labored in the fields to one in which a large fraction labored in factories.

Since factories tended not to be sunlit, and factory workers tended not to be highly affluent, the ranks of the sun deprived suddenly included more than just the idle rich.

Consequently, lack of a suntan was no longer considered to be a sign of status. Instead, in urban locals, it was only those who could afford to not spend all of their time working in doors who could expose their skin to the sun.

The status suntan was born!

a new sun ethos:

With the increasing prosperity and idle time that followed World War II, sun exposure suddenly once again became accessible to the urban masses.

This time, however, the suntan could not be considered a sign of inability to avoid the sun, and therefore did not fall out of favor.

Instead, the pre-World War II status of a suntan was recalled and the degree of suntan became a sign of status, a measure of both leisure time and ability to travel to exotic southern locals during Winter months.

epidemic skin damage:

And thus the stage was set for an epidemic occurrence of premature aging and skin cancer as more and more pursued, mostly with great ignorance, more and more sun.

the great suntan inertia:

Today we suffer the consequences of these trends in sun abuse despite our knowing better.

Part of the problem is simply the conflict between what we as a society thought we knew and understood decades ago (a "healthy" suntan is good for us, right?) and what science has subsequently discovered (there is no such thing as a healthy suntan and certainly not one which is any good for us).

The other part is that the new scientific understanding has simply not been sufficiently popularized. In this lecture we will take a stab at enlightening the world to the dangers of exposure to ultraviolet radiation.

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ultraviolet light (radiation) ---

electromagnetic spectra:

The sun emits photons, among other things, but only photons manage to make it through Earth's atmosphere but not through the Earth itself.

The majority of the photons which reach the Earth's surface have variations in energy associated with them that we perceive as colors (wavelenghts equal 700 nm down to 400 nm). This is known as the visible spectrum.

The rest are of greater energy (< 400 nm) and are considered to make up the ultraviolet spectrum (UV; "beyond violet", violet being the most energetic of the colors that make up the visible spectrum).

UV striking earth:

Depending on source (i.e., authors), the UV spectrum ranges from 15 to 390 nm or 4 to 400 nm.

UV emitted from the sun and striking the upper atmosphere of the earth is typically found only in the longer wavelength (less energetic) portion of the UV spectrum (i.e., bigger numbers).

Of that UV radiation which strikes the upper atmosphere, not all makes it through the atmosphere to strike the surface of the Earth. Particularly, it is filtered by the Earth's stratospheric ozone layer.

In fact, the spectrum which strikes the earth spans only from 287 nm to 390 nm.

action spectra:

UV in the range of 260 nm is highly biologically damaging because this wavelength is preferentially absorbed by and damages DNA. However, UV of this higher energy does not typically reach the Earth's surface.

Of that UV which strikes the Earth's surface, that with wavelengths shorter than 320 is most damaging to cells, particularly that with a wavelength of 296.7 nm.

Higher wavelength (i.e., > 320 nm; less energetic) UV radiation is less damaging, but is more penetrating of unprotected tissues.

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UV-A, UV-B, UV-C ---

UV-A:

A common name for the less energetic UV spectra (i.e., > 320 nm).

UV-A comprises about 5.5% of the sun's energy striking the Earth.

UV-A radiation is less damaging but more penetrating than UV-B.

UV-A appears to be responsible for a large component of the premature aging effect the sun has on the skin. It appears to do this by damaging the connective tissue of the underlying dermis layer.

UV-A, along with UV-B, causes skin to tan.

UV-A is the "safe" form of UV radiation typically employed in tanning solons.

Note that UV-A is not filtered by glass unless that glass is well angled (as in wind shield glass) or is specially treated to resist UV-A penetration.

UV-B:

The more energetic of the UV which strikes the Earth's surface, having a spectrum from 287 to 320 nm.

UV-B comprises about 0.5% of the sun's energy striking the Earth.

UV-B causes skin to burn.

UV-B exposure is thought to be the dominant cause of skin cancer formation.

Suntan lotion SPF ratings refer to the ability of a product to block UV-B radiation.

In general, glass affords protection against UV-B radiation.

UV-C:

UV-C includes that range of UV radiation, emitted by the sun, which fails to reach the Earth's surface.

UV-C is extremely damaging to biological systems and, in fact, is commonly employed as an artificial biocidal treatment.

caveat:

Physicists of the world, please enlighten me (abedon.1@osu.edu) if I have failed to successfully match UV wavelengths with UV-A, UV-B, and UV-C designations.

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skin cancer ---

most common cancer:

Skin cancers are the most common of all cancers. Approximately one-half million new skin cancers are diagnosed annually in America.

As many as 50% of peolpe who live to the age of 65 are expected to experience at least one skin cancer.

Fewer than 10,000 individuals die from skin cancers annually, however.

Nevertheless, curing skin cancer, since this can involve surgery, radiation treatments, and chemotherapy, is not necessarily as pleasurable an experience as, for example, spending a day at the beach.

caused by the sun:

Skin cancers occur as a consequence of over-exposure to the sun, especially by particularly susceptible individuals (with susceptibility and degree of exposure tend to have similar impacts on incidence).

Skin cancers tend to occur in those areas of the body which are most exposed to the sun: the face, head, and neck (i.e., approximately 80% of all skin cancers appear in these areas).

"According to the Skin Cancer Foundation, skin cancer takes decades to develop, and the effects of ultraviolet radiation are cumulative. Thus, even a few weeks of sunbathing each summer will, after twenty or more years, amount to considerable exposure, which in vulnerable people could lead to skin cancer." (p. 77, Siegel, 1990)

types of skin cancer:

There are three general types of skin cancer and the incidence of these cancers and their deadliness is negatively correlated such that the most prevalent are least dangerous and least prevalent most dangerous. These cancers include (in order of decreasing prevalence):

1. basal-cell carcinoma
2. squamous-cell carcinoma
3. malignant melanoma

Note that carcinomas are cancers of the skin's epithelial cells.

risk factors:

"Exhaustive studies have shown that the people most likely to get skin cancer belong to one or more of the following groups:

• Those who have fair skin and sunburn easily (Type 1 or 2 skin)
• Those who are photosensitive
• Those who live in the south or southeast United States or in other areas of the world relatively near the equator (the number of cases doubles with every 8 degrees latitude nearer the equator)
• Those who live at high altitudes (more UVB light penetrates the thinner atmosphere; the city with the highest rate of skin cancer in the United States is Alburquerque, New Mexico, where the altitude is high and the latitude is low)
• Those who experience prolonged exposure to the sun, such as:
  • construction workers
  • farmers
  • athletes (professional and amateur)
  • lifeguards
  • ski instructors
  • sun-worshipers
• Those with genetic conditions predisposing them to skin cancer (such as Gorlin's syndrome, xeroderma pigmentosa, or albinism)
• Those with excessive exposure to X rays (as well as coal tars, arsenic, and thermal burns, plus skin cancers may also associate with scars, vaccinations, tattoos, chronic irritation, ulcerations, traumas, and infections)
• Relatives of people who have had basal cell carcinomas
• (Those who have been previously diagnosed with skin cancer, i.e., as high as 50 to 60% recurrence rate)
• Men, more than women, in the over-forty age range
• Women, more than men, in the under-forty age range
• Those who have a number of unusual moles
• Those who had severe childhood or adolescent sunburns
• Those whose families have a history of melanoma"

(p. 78, Siegel, 1990)

searching for signs:

"In a well-lit room, use a full-length mirror and a small mirror to examine the more difficult-to-see places. With a hair brush or (even better) a blow dryer for pushing away your hair to see your scalp, examina all of your skin, looking for the following warning signs:

• An existing pimple, growth, small sore, or other lesion that
  --- hasn't healed
  --- is getting larger
  --- looks irritated
  --- itches, scabs, or bleeds

  A pale, waxy, pearly looking lump that

  --- suddenly appears

  --- becomes an open sore

  A red, scaly, sharply outlined patch of skin

  An existing mole that

  --- changes in size

  --- becomes red, white, or partially blue or has other tiny dark spots

  --- begins to bleed

  --- becomes darker in color

  New moles--especially if colored a uniform bluish black or bluish gray or exhibiting an uneven surface"

(p. 82, Siegel, 1990)

If you observe any of the above, if you don't regularly examine yourself (or have yourself examined), or if you haven't been professionally examined by a dermatologist recently (i.e., in the past year or so), then it is recommended that you get professionally examined sooner rather than later.

Note that basal cell carcinomas are particularly difficult to self-diagnose.

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non-melanoma skin cancers ---

incidence:

There are approximately one-half million new cases of skin cancer diagnosed each year.

80% are basal cell carcinomas (400,000 new cases annually).

20% are squamous cell carcinomas (80,000 to 100,000 new cases annually).

Skin cancers are responsible for approximately 2000 deaths per year.

prognosis:

Basal cell carcinomas have little tendency to metastisize to distant body parts, though they can invade and severely damage underlying tissues.

Squamous cell carcinomas grow faster than do basal cell carcinomas.

Squamous cell carcinomas also invade underlying structures to a much greater extent than do basal cell carcinomas.

Squamous cell carcinomas also are capable of metastasizing to distant body parts.

In a word, squamous cell carcinomas present a "worse" prognosis than do basal cell carcinomas.

caused by too much sun:

Non-malignant melanoma skin cancer are associated with cumulative exposures to the sun, and to a lesser extent by episodic burning.

Individuals who work or play for long hours out of doors tend to be who are most commonly afflicted.

fair skinned especially vulnerable:

People with fair skin, light eye color, and a tendency to burn rather than tan when exposed to sun are much more likely to succumb to non-malignant melanoma skin cancers (see Skin Types).

young especially vulnerable:

"Exposure to ultraviolet radiation early in life has a major impact on development of skin cancer later in life." (p. 26, Siegel, 1990)

Approximately 50 to 80% of the average American's cumulative exposure to the sun is achieved by the ages of 18 to 20.

Children receive on average about three times as much daily UV-B exposure as adults.

tissue origins:

Basal cell carcinomas form from transformed basal cells of the skin's epithelium.

Squamous cell carcinomas form from karatinocytes.

Malignant melanomas, of course, form from melanocytes.

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malignant melanoma ---

very lethal:

In 1989, there were 27,000 known cases and 6,000 deaths from malignant melanoma.

increasing danger:

"Back in the 1930's, the risk of developing malignant melanoma was 1 in 1,500 (fifteen hundred). Now the lifetime risk is 1 in 128. According to the Skin Cancer Foundation, at the current rates of increase, the risk will become 1 in 90 by the year 2000." (p. xvii, Siegel, 1990)

prognosis:

"Almost always curable if detected early and treated promptly. Early detection is easily accomplished, since melanoma is visible, in contrast to cancers that begin internally and are difficult to diagnose or even to suspect until they have already spread." (p. 93, Siegel, 1990)

In testament in part to malignant melanomas not always being detected and/or treated early enough, over 20% of cases lead to death.

"Melanoma does its most severe damage (ultimately ending in death) by metastasizing (spreading) to the lungs, the liver, the neurological system, or other body structures and organs. How fast and where it will spread is not always predictable." (p. 107, Siegel, 1990)

young especially vulnerable:

Malignant melanoma is especially linked to bad (blistering especially) sunburns during childhood. Even a single blistering sunburn during adolescence may double the risk of developing melanoma later in life.

"From the point of view of melanoma risk, ages ten to twenty-four are the worst-time of life to live (or play) in a sunny climate." (p. 53, Siegel, 1990)

pregnancy:

Pregnancy can stimulate the growth of melanoma cells.

Avoidance of pregnancy all together can be necessary to keep some not yet fatal melanomas in check.

searching for signs:

"The American Cancer Society, the American Academy of Dermatology, and the Skin Cancer Foundation have devised a simple ABCD rule to help people remember some of the signs of melanoma:

A. Asymmetry: One half of the mole or growth does not match the other half.

B. Border Irregularity: The edges are ragged, notched or blurred.

C. Color: The pigmentation is not uniform. Shades of tan, brown, and black may be present. Red, white, and blue may add to the mottled appearance.

D. Diameter: Any mole larger than 6 mm (the size of a pencil eraser) or exhibiting a sudden or continuing increase in size should be of special concern."

(p.101, Siegel, 1990)

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photosensivity (chemical photosensivity) ---

photosensitivity:

One often overlooked danger of the sun is photosensitivity, the tendency of some individuals to have adverse skin or systemic reactions to sun exposure.

Obviously individuals who are photosensitive are well off avoiding the sun to even greater extremes than ought the non-photosensitive.

tricky diagnosis:

Note that diagnosis of photosensitivity can be tricky since symptoms can take hours and even days to manifest themselves.

chemical photosensitivity:

Even if you are not photosensitive, you are still not necessarily immune to photosensitivity since photosensitivity can also be induced by exposure to certain chemicals, including many drugs and cosmetics.

If you suspect chemical photosensitivity, obviously get out of the sun.

If you are taking a medication, cosmetic, or other substance either internally or on your skin (including sunscreens which are new to you), always assume that it can lead to chemical photosensitivity until proven otherwise (i.e., don't test things out with a day of sun bathing at the beach).

If you discover that you are photosensitive to something that you are taking or using voluntarily, obviously discontinue use. If you are taking or using something on the advice of a physician, consult with that physician (or your pharmacist) before discontinuing use.

If you are undergoing chemotherapy (even anti-bacterial chemotherapy) or are being treated for AIDS, stay out of the sun!

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tanning ---

physiology of tanning:

"After significant exposure to UV light in sunlight, a hormone called melanocyte stimulating hormone (MSH; emphasis theirs) is released from the pituitary gland at the base of the brain. Transported by the blood, this hormone reaches the melanocytes, causing an increase in their activity and a darkening of skin." (p. 115, Benjamin et al., 1997)

"If you . . . feel you want a bit of a tan, start by using sunscreen with an SPF of 15 or more, and then later in the season use sunscreen with a lower number. A sensible tan like this shouldn't get you into any major health trouble; but remember, it certainly will accelerate skin aging. There is no way around this simple rule: tan now, pay later." (p. 133, Siegel, 1990)

no safe tanning:

"No type or degree of tanning is safe." (p. 9, Siegel, 1990 paraphrasing the conclusion of an NIH committee convened to study the impact of sunlight on the skin)

There is no safe level of tanning. All degrees of tanning are a surrogate marker for skin damage, whether leading to premature aging or to skin cancer.

"Even though your suntan fades as older cells are shed, damage still occurs because the ultraviolet rays of the sun penetrate beyond your skin's visible portion or epidermis." (p. 10, Siegel, 1990)

supplies minimal subsequent protection:

See Dark Skin section of Skin Types.

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sunburn (poisoning) ---

sunburn physiology:

sun poisoning:

A severe sunburn.

Symptoms of sun poisoning include blistering, peeling, nausea, sustained chills, fever, and even an accelerated heart rate (tachycardia).

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aging of the skin ---

wrinkled and sagging dermis:

"The elastic tissues of the dermis are altered with age, as they begin to break down and lose elasticity. The fibers then stiffen, and the skin begins to wrinkle and sag." (p. 11, Siegel, 1990)

hypodermis:

"Over the years the quantity of fatty tissue diminishes, which explains why older people are often best with skin injuries and sensitivity to the cold." (p. 11, Siegel, 1990)

increased sensitivity:

"The very young and the elderly are particularly prone to injury from the sun. Young people often have lighter skin than they will have in later years, and unless they are well instructed and motivated in sun protection techniques, they are likely to ignore the danger. As adults age, their skin becomes thinner and they may have fewer melanocytes, so they are more vulnerable to burning, too." (p. 23, Siegel, 1990)

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skin types ---

dark skin:

Dark skin generally affords greater protection from the harmful effects of UV radiation than does light or lighter skin.

However, note that this is only a generalization and therefore does not preclude dark skin individuals or those with a good tan from being sensitive to the sun.

In fact, tanned skin only affords only about as much UV protection as that afforded by SPF 2 or 3 sunscreen (as much as SPF 4 for impressively dark tans).

"The melanin in . . . skin is still insufficient to protect the deeper layers of the skin from adsorbing the sun's rays." (p. 19, Siegel, 1990)

"According to some estimates, people with Type 5 or 6 skin (i.e., dark, see table below) may have a ten-year grace period of sun exposure without loss of elasticity (i.e., at least one measure of premature aging)." (p. 27, Siegel, 1990)

table of skin types:

Skin Type	Reaction to the Sun	Examples
Type I	Always burns, sometimes painfully; seldom or never tans; peels; extremely sensitive to UV radiation	People with fair skin, blue or sometimes brown eyes, freckles, blonde or red hair
Type II	Usually burns, sometimes painfully; sometimes tans, but not very much; may peel; very sensitive to UV radiation	People with fair skin, red, blonde, or brown hair, and blue, hazel, or brown eyes
Type III	Burns moderately; tans gradually; sensitive to UV radiation	Average Caucasian
Type IV	Seldom burns; tans easily and reacts with almost immediate darkening of skin (IPD: Immediate Pigment Darkening); moderately sensitive to UV radiation	People with white, olive, or light brown skin, dark brown hair, and dark eyes
Type V	Almost never burns; tans easily and considerably; IPD reaction; minimally sensitive to UV radiation	Brown-skinned people, often of Asian or Indian Descent
Type VI	Never burns, but tans greatly; IPD reaction; not sensitive to UV radiation	African-Americans

(from p. 18, Siegel, 1990)

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premature aging (photoaging) ---

caused by the sun:

The various examples of how the skin ages represent, in fact, cumulative declines in the vitality of the skin.

In fact, much of this decline in vitality is not so much a natural process of aging, but the consequence of cumulative exposure of unprotected skin to the sun.

Conclusion: The most crucial thing you can do to avoid skin aging is to avoid exposure to the sun.

photoaging:

Premature aging resulting from exposure to the sun.

"Seventy- and eighty-year-olds who never went out in the sun may have smooth, unwrinkled skin that reveals only some thinning, deepening of lines, and loss of elasticity. Because years of sun exposure may pass before photoaging begins to take place, people have often attributed their aging look to bad luck. But although most people will have a progressive deepening of normal expression lines and will develop some fine wrinkles over the years, those who have had a great deal of sun exposure will acquire deep wrinkles and a bumpy, leathery-textured skin." (p. 26-27, Siegel, 1990)

accelerated loss of resiliance:

Another way of looking at photoaging is that the skin has only so much redundancy or resilience.

With time this resilience normally declines. However most of us are born with enough resilience to last an even long lifetime.

Sun exposure erodes this resilience. However sufficient resilience is built into the skin that sun exposure early in life typically fails to erode this resilience to the point where gross symptoms of premature aging are apparent.

However, with time resilience naturally declines anyway. Those who have habitually over exposed themselves to the sun, however, show this natural decline in resilience over an already depleted base.

As a consequence, the effects of your Summer's in the sun don't reach a level at which they can no longer be ignored until decades after your earlier sun exposure.

Thus, you should first and foremost attempt to protect the skin of your children, who have not yet eroded the resilience of their skin.

However, since photoaging is cumulative and there exists some possibility that skin which is no longer exposed to the sun may to some extent heal itself, it always pays to get out of the sun now!

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tanning parlors ---

high incidence:

Five to ten percent of the U.S. population is thought to regularly visit and employ the facilities of commercial tanning parlors.

Especially prevalent among users are adolescents and young adults "working on their tans."

not safe:

Two gross safety concerns are associated with employing tanning parlors:

1. potential UV induced eye damage
2. overestimates of the safety of intense UV-A exposure to the skin.

eye damage:

Eye damage results as a consequence of our eyelids not being opaque to UV-A.

An absence of effective (i.e., opaque) goggles during parlor tanning can therefore rapidly lead to UV induced burns of the eyes: a painful and dangerous consequence.

Therefore, without question one must employ opaque, intact, effective (and properly sterilized) goggles during parlor tanning.

skin damage:

Tanning parlors employ intense UV-A radiation but, ideally, no UV-B.

This allows parlor goers to achieve a tan without burning.

However, note that this is accomplished via the almost certain photoaging of their skin.

Note that the tan achieved is no more effective in resisting burning under the real sun than is a normally realized tan, and the amount of protection one gains from tanning is not all that great anyway (i.e., SPF 3 to 5 equivalent).

Conclusion, if you regularly employ tanning parlors to work on your tan, you may look great now, but watch out, because premature skin aging really SUCKS!

seasonal affective disorder (SAD):

This is a physiological and psychological disorder which basically is a fancy name for the Winter-time blues.

Borne out hypotheses that SAD is brought on by a lack of exposure to light of sufficient intensity (i.e., the Winter-time or indoor sun versus the outdoor Summer-time sun) have led to the development of a light therapy which involves the artificial exposure of afflicted persons to high intensity, full visual spectrum light. That is, a mimicking of exposure to Summer-time sunlight.

Note that SAD treatment does not involve the exposure of individuals to UV radiation!

This means that intense exposure to UV-A radiation in tanning parlors does not mimic standard of practice treatment of SAD (and nor is it necessary).

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enviromental factors ---

Factors which increase the UV dose striking skin and eyes included:

1. increases in elevation.
2. snow, off which UV reflects.
3. sand, off which UV reflects.
4. water, off which UV reflects.
5. concrete, off which UV reflects.
6. being closer on the calendar to the Summer solstice.
7. being closer in the day to noon.
8. being closer to the equator.
9. an overhead ozone depleted stratosphere.
10. cloudless days.

Obviously, the reverse of all of the above has the opposite effect, i.e., reducing the UV intensity.

The hours to avoid sun exposure are actually 10 A.M. to 2 P.M., during non-daylight savings time, and 11:00 A.M. to 3 P.M. during daylight savings time.

It is important to realize that clouds and pollution have an only minimal mitigating effect on UV intensity.

There is a 4 to 5% increase in UV intensity with each 1000 feet in elevation.

Note that, as a consequence of these factors, a person can still be badly exposed to the sun even if they are sitting in the shade at the beach (especially if they are close to unshaded sand or the water), skiing (especially on sunny slopes on sunny days at high altitudes in the Spring or Summer), or even spending a long time unprotected and out of doors on a cloudy day (and especially in the Summer, nearer to the equator, at noon, and at higher altitudes).

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sunscreen (block) ---

skin cancer protection:

"Regular use of sunscreen with an SPF of 15 during the first eighteen years of life (may) reduce a person's lifetime risk of developing nonmelanoma skin cancer by 78 percent." (p. 53, Siegel, 1990)

tips for effective (and pleasurable) use:

Employ a sunscreen with at least an SPF factor of 15

Use one that also indicates that it is effective against UV-A (which is not covered by the SPF rating).

Store sunscreens in convenient locations.

Some sunscreens can go bad with time. Especially do not push expiration dates.

Remember that sunscreen can be important even if you are not having fun.

The need for sunscreen can appear unexpectedly (i.e., when you unexpectedly end up talking with a friend in the sun for a half an hour--"80 percent of sun exposure is incidental. Your skin absorbs those rays when you do errands, walk the dog, push the baby carriage or shopping cart, or simply walk to and from lunch. That adds up to a lot of cumulative exposure, and although you are not likely to get a sunburn from these errands, the damage is accruing in the third layer of skin, the dermis." p. 135, Siegel, 1990).

Avoid getting sunscreen in your eyes.

Creamy sun screens tend to be less drying.

Employ unscented sunscreen to avoid attracting insects.

Use sunscreens liberally, and reapply often (every few hours or after submersion or toweling).

Remember that sunscreen needs to be applied under clothing at edges of clothing or if clothing does not itself supply sufficient UV protection.

Apply PABA and PABA-ester containing sunscreens two (yes 2!) hours before entering the sun, and other sunscreens one-half hour prior to sun exposure.

Place sun block on especially sensitive areas such as the top of your ears.

SPF rating:

"Whether you prefer sunscreen or sunblock, choose one with an SPG rating of at least 15. Light-skinned people should opt for an SPF rating of 30. If it normally takes you 10 minutes to burn at the beach without any protection, an SPF-15 product will let you frolic in the sun for 15 times 10 minutes, or 2½ hours. After that, you've had your radiation dose for the day. Stay out any longer, even if you reapply sunscreen, and you will burn." (Gorman, 1998)

sun block:

Typically zinc oxide or titanium dioxide.

Sunblocks are opaque to both UV radiation and visible light.

They are very effective UV blocks.

young babies:

Despite their vulnerability to the sun, young babies (under six months) should not be exposed to sun block.

Instead make sure that your baby is protected from the overhead and reflective UV radiation by tightly woven fabrics, either on or about him/her. Note, if you can see through a fabric when holding it up to a bright light sourse, it is either too thin or not sufficiently tightly woven. Sand, concrete, snow, and water are all UV reflectors.

Note that babies are not especially well equipped to cool their bodies when exposed to high temperatures. As a consequence it is a good idea to simply avoid taking very young babies on hot outdoor outings.

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protective clothing (hat) ---

sunscreen not enough (slip, slop, slap):

"You should never rely on sunscreen as your only protection. Stay out of the midday sun (from 10 to 3), and you will avoid 60% of the UV-B that hits the earth. Slip on a long-sleeve shirt to protect those vulnerable areas on the shoulders and back. When you use sunscreen, slop it on think and often. And slap on a wide-brimmed hat, and you can keep 70% of the sun's rays off your face and neck. After decades of their "Slip, Slop, Slap" campaign, Australians are starting to see a decrease in their rate of deaths from melanoma." (Gorman, 1998)

sun glasses:

Look for UV-A and UV-B protection.

Larger lenses, closer fitting lenses and frames, and better fitting frames all reduce light leakage around protective lenses.

Cataract prevention.

Note that the lens of the eye is especially transparent to UV radiation in the very young thus making sun glass use by the very young even more important than for older individuals.

Snow blindness is severe sunburn of the eyes.

hat:

Preferably one which covers your scalp, ears, neck, and shades your face.

other clothing:

Choose the rest of your clothing for comfort and ability to block UV radiation.

Cotton blocks better than do untreated synthetics.

Thicker is better than thinner.

Tighter weaves are better than looser weaves.

Long sleeves are preferable to short sleeves which are preferably to tank tops which are preferable to little or nothing at all.

Long pants are better than shorts are better than little or nothing at all.

Closed shoes are better than sandals with socks are better than sandals without socks are better than little or nothing at all.

If you prefer to have little or nothing come between you and the sun, nevertheless consider wearing a wide brimmed hat, UV-blocking glasses, perhaps a little something over your shoulders, and don't forget to liberally apply your sunscreen everywhere else!

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ozone depletion ---

stratospheric ozone:

Ozone is a trimeric form of oxygen which comes into being as a consequence of UV striking more typical dimeric molecular oxygen.

Ozone is a relatively unstable molecule and consequently oxidizing molecule, but it does have the virtue of being able to adsorb much of the spectrum of UV radiation which strikes the upper atmosphere.

Consequently, ozone serves as a UV filtering layer which reduces the total UV radiation which reaches the ground.

ozone depletion:

As a consequence of anthropomorphic release of chemicals (CFCs) which have a catalytic, degradative effect on stratospheric ozone, the protective ozone layer has declined in ozone density recent decades.

In some places, notably the extreme Southern and Northern locals, the ozone layer has dramatically declined in ozone density, especially during the Winter months in each of the hemispheres.

Stratospheric ozone depletion is particularly a problem for artic and antarctic populations of organisms who must now deal with a UV intensity beyond that which their ancestors evolved to cope with.

Ecosystem impacts could be dramatic and have far ranging consequences.

impact on humans:

Assuming that appropriate measures undertaken to assure ozone depletion is minimized (e.g., the world-wide ban on CFCs via the Montreal Protocol), the impact on humans due to ozone depletion may not be enormous.

This lack of devastating impact is due mostly to the fact that the majority of ozone depletion seems to be occurring particularly in those areas of the globe in which UV intensity is naturally low. Therefore, significant relative increases in UV intensity fail to translate into dramatic absolute increases in UV intensity.

If ozone had instead been depleted over the equators preferentially, the impact could have been unimaginably devastating. We knew that stratospheric ozone loss through CFC use was a possibility long before we knew just how the effects would manifest themselves. In a phrase: We were damn lucky we didn't figuratively shoot ourselves in our collective feet.

more skin cancers:

The primary impact increased UV intensity will likely have on human health, assume our food crops survive, is in an increase in skin cancer rates.

It has been estimated that for each one percent drop in stratospheric ozone concentrations, there my be about 5% more non-melanoma skin cancers.

That translates to about 25,000 new skin cancer cases per year in the United States.

links ---

• Skin & Cancer Foundation
• An Introduction to Skin Cancer
• SafeSun, Personal UV Meter - Basic UV Facts
• SafeSun, Personal UV Meter - Scientific Info
• sunSmart, Inc.
• Plastic Surgery
• American Society for Mohs Surgery
• Melanoma
• The Melanoma List

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1. Benjamin, C. L., Garman, G. R., Funston, J. H. (1997). Human Biology. The McGraw-Hill Companies, Inc. New York. pp. 128-132.

2. Gorman, C. (1997). New sunscreens. Time June, 29, 1998, p. 79.

3. Siegel, M.-E. (1990). Safe in the Sun. Walker and Company. New York.

4. (1982). McGraw-Hill Encyclopedia of Science & Technology. 5th Edition. McGraw-Hill Book Company. New York. volume 14, pp. 216-218

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