Summer is here, or will be shortly and with that we increase our outdoor activities. More time outdoors means more sun exposure. We all need a small amount of time in the sun without sunscreen so that we can produce vitamin D. This statement is supported by the World Health Organization, however the WHO also states that overexposure to UV rays greatly increases the risk for health issues. Somewhere in the middle there is a balance between enjoying the healthy benefits of being in the sun and overexposure.
It is estimated that 20 minutes in the sun without sunscreen (10 minutes per side) was more than enough to get all the healthy vitamin D benefits. Darker skin colors may need a little more exposure to receive the same benefits, nevertheless, skin cancers do occur with this group and unfortunately they are often detected at a later, more dangerous stage.
Research has proven that vitamin D intake prevents breast, prostrate and other kinds of cancer at rates 30 times higher than melanoma occurs. Vitamin D also is important in preventing the incidence of multiple sclerosis, especially for us Canadians who live in more northerly latitudes, where we get less exposure to the sun’s beneficial ultraviolet B rays. Other autoimmune diseases, like type 1 diabetes, are similarly affected. Recent expert panels have concluded that to prevent fractures, older adults should aim for serum 25-hydroxyvitamin D levels that are higher than 75 nmol/L. To guarantee this level, adults need at least 2,000 IU a day of vitamin D.
The WHO states approximately 130,000 malignant melanomas occur globally each year, substantially contributing to mortality rates in fair-skinned populations. An estimated 66,000 deaths occur annually from melanoma and other skin cancers. Worldwide some 12 to 15 million people become blind from cataracts annually, of which up to 20% may be caused or enhanced by sun exposure according to WHO estimates. Furthermore, a growing body of evidence suggests that environmental levels of UV radiation may suppress cell-mediated immunity and thereby enhance the risk of infectious diseases and limit the efficacy of vaccinations. Over the longer term, UV radiation induces degenerative changes in cells of the skin, fibrous tissue and blood vessels leading to premature skin aging, photodermatoses and actinic keratoses.
Health Canada suggest that the level of ultraviolet (UV) radiation reaching the earth’s surface depends on a number of factors. The UV rays are strongest between 12 and 1pm when they have the shortest distance to travel. UV intensity is greatest in the spring and summer based on the angle of the sun. In areas where there is a decrease in the thickness of the ozone layer the UV increases. Cloud cover can greatly affect the amount of UV radiation received at the earth’s surface. Clouds that are dark and heavily burdened with water can absorb up to 80 percent of the radiation. High thin clouds do not significantly affect the amount of UV radiation that will reach the surface. Scattered clouds can actually increase the amount of UV radiation at the surface of the Earth due to reflection.
The intensity of UV radiation also depends on which pressure system is influencing the weather. A high-pressure area results in a thinner ozone layer whereas a low-pressure area is characteristic of a thicker ozone layer. Fresh white snow reflects about 85 percent of UV radiation while other bright surfaces such as sand, concrete, and water, reflect less. If skiing on a spring day at the end of March, for example, the UV index may only be 4, but due to reflection from the snow, the skier may experience a UV index of 7. UV radiation increases with altitude because there is less atmosphere to absorb the damaging rays. At an altitude of around 2,000 metres the amount of UV radiation can be up to 30% higher than at sea level. UV is strongest at the equator where the UV index can reach about 12. In Canada, the UV index reaches its maximum in southern Ontario and is the least at the North Pole.
The SunSmart program in Australia lists the following ways to protect yourself and your family from overexposure…Shade, clothing and hats provide the best protection – applying sunscreen becomes necessary on those parts of the body that remain exposed like the face and hands. Sunscreen should never be used to prolong the duration of sun exposure. Limit time in the midday sun as the sun’s UV rays are the strongest between 10 a.m. and 4 p.m. Watch for the UV index as this important resource can help you plan your outdoor activities in ways that prevent overexposure to the sun’s rays. Use shade wisely, seeking shade when UV rays are the most intense, but keep in mind that shade structures such as trees, umbrellas or canopies do not offer complete sun protection. Remember the shadow rule: “Watch your shadow – Short shadow, seek shade!”
Wear protective clothing, a hat with a wide brim offers good sun protection for your eyes, ears, face, and the back or your neck. Sunglasses that provide 99 to 100 percent UV-A and UV-B protection will greatly reduce eye damage from sunfrom the sun. Use sunscreen applying a broad-spectrum sunscreen of SPF 15+ or higher liberally and re-apply every two hours, or after working, swimming, playing or exercising outdoors. Avoid sunlamps and tanning parlours as sunbeds damage the skin and unprotected eyes and are best avoided entirely.
The take home message is to use common sense…some sun exposure is important for our vitamin D levels but too much exposure has many risks.