A WINTER WARNING

Contributed by Christopher Pullins, MD



Normal Eye
We are well into the winter season and those in the snow climates have already ventured out into nature's winter wonderland. Many are unaware of a potential danger that an individual is exposed to each time they step outside. It is a misconception that the effects of prolonged sun exposure are lessened as temperatures start to decline. In some cases, the risk is increased. We will discuss what this invisible element is and how to protect yourself against it.





Center for Global Environmental Research, National Institute for Environmental Studies Japan
What is Ultraviolet light?

Ultraviolet light (UV) is a source of energy that comes primarily from the sun. Ultra means beyond. It's name explains why it is invisible to the naked eye. We learned the mnemonic ROYGBIV as a child to help us memorize the visible color spectrum. Violet is at the end of the spectrum having the shortest wavelength. Ultraviolet rays are classified into types, UV-A, UV-B, and UV-C. They vary in their energy and wavelengths with UVA being the longest and weakest and UVC being the shortest and strongest, respectively. This is important as only UVC has enough energy to split ozone molecules which produces a filter effect not allowing it to pass through the ozone layer and thus the atmosphere. The ozone layer does have some effect on all types of UV radiation. The amount of UV rays reaching the ground increases indirectly proportional to the thickness of the ozone layer. Sand, snow, and water also can enhance this effect by reflecting the UV rays back up onto an individual.


What consequence does it have on our health?

Prolonged exposure to UV rays has consequences on our skin, eyes, and immune system. We will not discuss UVC in this portion as it does not reach the ground surface. However, this may change if the ozone layer continues to deteriorate. One sign of UV skin overexposure is redness (erythema), the common sunburn. This is an attempt by the body to heal itself by sending increase blood flow to the area of damage. UVB is responsible for this effect as it reaches the top skin layer known as the epidermis. UVA goes down deeper to the dermis and causes no erythema. UVA is thought to lead to premature aging of the skin and wrinkles. UVB is thought to lead to skin cancer as it distorts DNA molecules producing mutations. The immune system in the damaged skin normally would correct these oddities, but are inhibited by UV radiation. The 3 leading skin cancer types are squamous cell carcinoma, basal cell carcinoma and melanoma (deadliest). Fortunately, the first two do not spread to other organs. One myth that needs to be dispelled is that darker skinned individuals cannot or do not get skin cancer. Melanoma accounts for 80% of all skin cancer deaths. It can spell disastrous for African Americans as it is more likely to be caught at a later stage. Any skin lesion that changes needs to be brought to the attention of your physician immediately.

 
Cataracts
The eyes are also at risk for damage. They are uniquely placed in that they are recessed into the skull. They are protected by various structures such as the eyelashes, the eyebrows, and the eyelids. An individual can not stare directly into the sun as the pupils will constrict automatically. This mechanism fares well on a sunny day, but not on cloudy days when UV rays are still present. As stated previously, certain conditions can give an individual a double dose. Activities such as water skiing, snow skiing, fishing, and swimming put individuals at higher exposure risk due to the reflection effect. Conditions such as photokeratitis (sunburn of the cornea), cataracts (opacity of the lens) are caused by high exposure to UV rays. Photokeratitis, also known as snow blindness occurs when there is high exposure over a short period of time. It usually recedes in 1-2 days. UV rays also cause the proteins of the lens to disorganize and accumulate pigment. This leads to opacities in the lens. They can lead to blindness if not surgically corrected. This condition is known as cataracts and is currently the number one cause of blindness in the world.

There are also some beneficial effects of UV rays. They promote synthesis of Vitamin D in the skin. Vitamin D plays an important role in maintaining strong bones and positively impacts the immune system. UV rays also have medical applications. They are used to treat vitiligo and psoriasis.



 
Ski Goggles
How do I protect myself against UV exposure?

Fortunately, we do have some informative systems in place. One such system is the UV index. It was created to inform the public about the days UV intensity. Ratings are numerical. 1-3 means low exposure. 4-6 means medium exposure. 7-9 means high exposure. Anything above 10 means extreme. The worst time to be outside is between 9 a.m. and 3 p.m. Unfortunately, this is time most outdoor activities occur.
Preventative measures should include proper eyewear and skin protection. During the winter months, eyewear should cover eyes from all directions. Ski goggles usually cover all of this area. Some of the newer sleek designs may leave space for UV rays to get in. A cap with a visor may also add protection to shades. You want to choose eyewear that blocks 99% of UV rays.

Skin protection includes sunscreen products that are based on the sun protection factor system (SPF). This rating system tells how long an individual could stay out in the sun before developing sunburn. For example, if an individual normally would sunburn in 7 minutes without sunscreen. It would take 70 minutes with an SPF 10 sunscreen. The minimal SPF sunscreen used should be a rating of 15. Anything over SPF 30 is overkill, especially in African Americans. Sunscreen should cover both UVA and UVB. Some sunscreen products labeled "broad-spectrum UVA/UVB protection" do not provide adequate protection against UVA rays. The best UVA protection is provided by products that contain mexoryl, zinc oxide, and avobenzone. Any clotheswear that covers exposed skin also adds protection. Generally, fabrics with a tighter, denser weave, in dark colors, layered, and a matte or dull finish, give the best protection. There is sunlight or UV resistant fabric available out in the market. Darker skin individuals do have added protection due to the increased melanin in the skin. However, there is still a point at which sunburn can occur.


Remember these simple steps:

1) Check out the UV index

2) Put on the appropriate gear and eyewear

3) Apply sunscreen.

Now that you are aware of the impact of UV rays, get out and remain safe and active.


About Christopher Pullins

Dr. Christopher Pullins is a board certified Family Practioner in Peoria, AZ. His outdoor activity of choice is mountain biking.