Safety in the Sun: Notes on effective sun screening

June-July 1996

This is an article from WaveLength Magazine, available in print in North America and globally on the web.

The sun emits three forms of radiation: infared, visible, and ultraviolet. Infared and visible light are valuable because they provide warmth and the ability to see. But ultraviolet light can be harmful. It consists of three basic wavelengths: Ultraviolet A (longest), Ultraviolet B (mid-length), Ultraviolet C (shortest). Each penetrates the atmosphere differently and affects health in different ways.

  • UVA rays are high in intensity all day long, and not just between 10 a.m. and 2 p.m. as are the UVB rays.

  • UVA rays are similar in intensity from one season to another, while UVB rays are less intense during the winter months.

  • UVA rays are similar in intensity in any geographic location between the two poles whereas UVB rays become more intense as the equator is approached.

  • Unlike UVB, UVA rays can penetrate through glass and plastic.

We now know that the increase of harmful ultraviolet radiation reaching the earth is due to the increased concentration of chlorofluorocarbons (CFCs) in the upper atmosphere. While governments world-wide are moving quickly to ban the production of CFCs, these chemicals still continue to drift upward from our industrialized countries.

In the upper atmosphere, the chlorine atoms in CFCs attack ozone, taking away one oxygen atom from the three-oxygen-atom ozone molecule to form chlorine monoxide. That begins a chain reaction in which chlorine monoxide attaches to another oxygen atom to form an oxygen molecule and a chlorine atom. That chlorine atom can destroy thousands of ozone molecules.

Now scientists are recognizing that other chemicals do similar damage to the ozone. But even if all such chemicals are banned, it will be decades before the maximum ozone depletion will be reached. We have to both eliminate ozone-eating pollution of all kinds, and protect ourselves from the sun.

The Effects of UV Light

Eyes -- cataracts can develop, causing the lens to cloud up, resulting in blurred vision and, without treatment, blindness.

Skin -- exposure leads to accelerated aging, wrinkling and skin cancer.

Immune System -- the body is made more susceptible to infectious diseases through reduced immune response.

Crops -- by interfering with photosynthesis, there are lower crop yields.

Marine Life -- radiation decreases the growth of phytoplankton, the mainstay of the ocean food chain.

 

How To Be Safe In The Sun

  • Keep sun exposure to a minimum, especially between 1000 and 1500 hours, when the sun's rays are most intense.

  • Use a sunscreen liberally, and reapply every two hours when working, playing, or excercising outdoors. The sunscreen should be applied before putting on a bathing suit so no areas are missed.

  • Beware of clouds, since up to 80% of the sun's harmful rays can penetrate haze, light clouds and fog.

  • Wear appropriate clothing during prolonged periods in the sun, including a hat, long-sleeved shirt and pants.

  • Wear 100 percent UV-protected sunglasses that wrap around the eyes. Darker sunglasses do not necessarily filter out the UV rays unless they are specially coated.

  • Beware of reflective surfaces. Sand, snow, concrete, water, and even glossy textbook pages can reflect up to 85% of the sun's damaging rays.

  • Examine your skin and your children's regularly for any changes in moles, freckles, or skin discolourations.

  • Avoid tanning booths, and refrain from using sunlamps. The ultraviolet rays that they emit can cause sunburn and premature aging of the skin, suppress the immune system and increase the risk of skin cancer.

  • Protect children by keeping them out of the sun or minimizing sun exposure. An effective sunscreen should be worn even by babies.

  • Teach children and teenagers sun protection. Damage caused by sun exposure accumulates over the course of a lifetime.

  • Share your knowledge of safety in the sun with your friends and encourage then to practise it.

Protection with Sunscreens

The judicious and early use of sunscreens can protect against the most significant external factor in aging, the sun. Most sunscreens currently on the market, however, effectively block only UVB rays, not UVA. The concern is that people using high number sunscreens that block only UVB rays may still get high doses of UVA if natural warning signs, such as sunburn, are suppressed by these sunscreens.

Recognition of the damaging effects of UVA rays has set the wheels in motion for the reformulation of sunscreens to more effectively block UVA rays as well. Sunscreens contain various agents which have been proven to protect against the rays of the sun. Para-aminobenzoic acid or PABA, PABA esters, and cinnimates are all agents which effectively protect against UVB rays. Benzophenones and Parsol 1789 are effective in protecting against UVA rays. So, to be totally protected, select a sunscreen with a combination of two of these agents, one for UVB rays and one for UVA.

Theoretically SPF simply means the factor of time greater than normal that it takes for ultraviolet light from the sun's rays to burn the skin. For example, if the unprotected skin burns in one minute, an SPF 15 sunscreen would allow 15 minutes of sun exposure before sunburn. An SPF greater than 15 provides diminishing returns.

 

Use of Sunscreens

  • Apply a broad spectrum sunscreen with a Sun Protection Factor (SPF) of at least 15 to sun-exposed areas of the skin.

  • Apple sunscreen about 30 minutes before sun exposure when the body is cool and dry so it will bind better to the skin.

  • Reapply sunscreen throughout the day according to the amount of sun exposure you recieve. If you are participating in sports which make you perspire, reapply sunscreens every hour.

  • Protect the sun-exposed areas of the body all year round.

  • Apply adequate amounts of sunscreen, one ounce for one body for one application. If you are using adequate amounts of sunscreen, you should be purchasing it as regularly as you purchase toothpaste. High-risk areas for cancer such as the face and hands should receive an extra dose of sunscreen. If you don't mind the look of a total block, use zinc oxide or titanium dioxide on the particularly sensitive areas such as the nose and cheek bones. They are available in white and a variety of colours.

  • Be thorough in your application; sun-exposed skin which is not covered will burn.

  • If you are wearing loosely woven clothing, put sunscreens on underneath them. The sun also penetrates wet clothing easily.

  • Wear waterproof or water-resistant sunscreens if you plan to be in the water. Waterproof sunscreens last for 1 and 1/2 hours and water-resistant sunscreens for about 30-40 minutes. They should be reapplied to dry skin allowing a bonding period of 20 minutes before re-entering the water.

Information courtesy of Dermtek Pharmaceuticals, makers of Ombrelle