// Diseases, Disorders, Injuries

Skin Cancer and Sunlight

Does sunlight cause skin cancer? Health Canada states that one of the main causes of skin cancer is ultraviolet (UV) light, which is produced by the sun and tanning equipment.

Does sunlight cause skin cancer?

context Health Canada states that one of the main causes of skin cancer is ultraviolet (UV) light, which is produced by the sun and tanning equipment.
context Skin cancer is an occupational concern for people who work under the sun. The risk however, may be reduced through awareness of the problem, and by taking measures to prevent exposure to sunlight.

Are there different types of radiation in sunlight?

Yes. The types of radiation include: Except in extreme situations, neither visible light nor infrared radiation from sunlight causes health problems. However, ultraviolet (UV) radiation can cause harmful effects to the skin. There are three basic types of ultraviolet radiation:

context visible light, which gives us the colours we see
context infrared radiation which gives us the warmth we feel
context ultraviolet (UV) radiation
context UVA (long-wave UV)
context UVB (sunburn UV)
context UVC (short-wave UV)

How does sunlight affect the skin?

When ultraviolet radiation reaches the skin, some radiation is reflected away from the surface. The remaining radiation is scattered into the tissues just beneath the skin's surface. A fraction of this radiation is absorbed by the skin's living cells. Ultraviolet radiation absorbed by living cells damages sensitive substances that influence the skin's normal growth and appearance. Damage can result in:

context sunburn
context increased rate of aging of the skin
context skin cancer

Sunburn

context Sunburn is the most familiar and immediate effect of ultraviolet radiation on the skin. It is an inflammation caused by an increase in blood-flow beneath the skin. The reaction is not normally instantaneous, but reaches a bright red colour within 15 to 20 hours. The condition can be very painful and sometimes causes peeling of the skin.
context Brief intense exposure can cause severe sunburn in people who are not accustomed to strong sunlight. There is evidence that this type of exposure, as well as long-term exposures, might be linked to serious forms of skin cancer later in life.

Increased Rate of Aging of the Skin

context Repeated exposure to the sun's ultraviolet radiation eventually causes skin damage similar to the aging process. Patches of skin become thin and less elastic, and develop blemishes, sun freckles, and wrinkles. These changes may take many years of exposure but when they occur, the damage is irreversible.

Skin Cancer

context If exposure to sunlight continues for several years, the damaged skin has an increased chance of developing one of the forms of skin cancer. Exposure to ultraviolet radiation increases the risk of developing these cancers (although it may not be the only cause of the disease). Health Canada states that many studies have shown that people who have had many severe sunburns in childhood are at greater risk of developing skin cancer. Family history, some chemical exposures, and immune dysfunction conditions can also create a greater risk of developing skin cancer.

What types of skin cancer are linked to sunlight exposure?

Three different types of skin cancer are linked to sunlight exposure:

context basal cell cancer
context squamous cell cancer
context malignant melanoma

Basal Cell Cancer

context Basal cell cancer is the most common of all cancers in North America and Europe. It is usually found in areas of the skin exposed to sunlight, but sometimes occurs in other areas as well. This type of skin cancer appears as a raised, hard, red or red-grey, pearly wound often found on the forehead, eyelids, cheeks, nose, and lips. Although there is always a chance it could become serious, basal cell cancer usually does not spread. Most cases are easily treated.

Squamous Cell Cancer

context Squamous cell cancer occurs most frequently on the skin exposed to sunlight over long periods of time. As such, this type of skin cancer tends to develop where maximum exposure to radiation occurs - forehead, cheeks, nose, lower lip, and tops of the ears. It also usually develops in areas where the skin has been damaged by the sun - areas with blemishes or sun freckles. The blemishes develop into rough, scaly patches with small areas of open wounds that do not heal. They eventually grow into larger wounds with crusts. Similar to basal cell carcinoma, most cases are easily treated.

Malignant Melanoma

context Malignant melanoma, although rarer, is the most serious of the skin cancers. It often shows itself as a mole or pigment spot that begins to bleed, grow, or change its colour, shape or texture. It usually spreads if not treated in the early stage. If caught early, malignant melanoma can be treated. If treatment is delayed, melanoma can be hard to stop once it has spread to other parts of the body. Melanoma is the type most likely to be fatal.

What factors affect a person's risk?

Everyone is at risk of skin cancer. Risk factors include: Another factor may include exposure to chemicals. Exposure to certain chemicals can increase the skin's sensitivity to ultraviolet light through a process called photosensitization. Examples of such chemicals include: Check with your physician or pharmacist if you suspect abnormal or severe reaction to sun exposure after taking new medication. However, simple skin contact with psoralens, which are found in figs, parsnips, citrus plants, or mouldy celery, can make the skin more susceptible to sunburns in some individuals. Experimental studies show that chemicals called "promoters" can increase the cancer-causing ability of ultraviolet radiation. On the other hand, ultraviolet radiation itself can act as a promoter. In particular, ultraviolet radiation (UVR) can increase the cancer-causing ability of chemicals from coal tar and coal tar pitches.

context exposure to ultraviolet radiation (UV)
context having many moles, or certain types of moles on your skin
context having fair or light-coloured skin (these individuals have less melanin which may help protect the skin)
context history of skin cancer in self or family
context specific medical conditions, such as CDKN2A gene mutation
context weakened immune system
context heredity and medical factors, such as:
context coal tar, coal tar pitches, and petroleum products containing polycyclic aromatic hydrocarbons (PAHs)
context certain printing chemicals used in photosensitive printing processes
context certain drugs including antibiotics, oral contraceptives, anti-inflammatories, tranquilizers, and anti-nausea drugs
context chemicals called psoralens found naturally in certain plants, fruits and vegetables

Does the amount of exposure to sunlight matter?

context Yes. The damaging effects of ultraviolet radiation accumulate over the years. In general, the risk of developing skin cancer increases with the amount of time spent under the sun and the intensity of radiation. The intensity of radiation varies according to the season of the year, time of day, geographic location (latitude), elevation above sea level, reflection from surfaces (e.g., white sand or concrete, water, snow), stratospheric ozone, clouds, and air pollution.
context Studies have focused on the effects of intermittent (short-term, occasional) sun exposure in comparison to chronic (long-term) exposure. It appears that the type of exposure may influence the type of cancer that develops. For example, intermittent solar exposure may be an important factor leading to the onset of basal cell carcinoma of the skin. Childhood sun exposure may also play an important part in the development of these cancers later in adult life. The pattern for cutaneous melanoma is similar to that for basal cell carcinoma.
context In contrast, the relationship between squamous cell carcinoma and solar UVR appears to be quite different. For squamous cell tumours, high levels of chronic occupational sunlight exposure, especially in the 10 years before diagnosis, results in an elevated risk for this cancer in the highest exposure group.

What is the UV Index?

In order to address the growing concern by Canadians regarding changes in UVR resulting from ozone depletion, Environment and Climate Change Canada rates the UV intensity as UV Index on a scale of 0 (when there is no sunlight) to 11+ (extreme). It can go to the mid-teens at midday in the tropics. In Canada the UV Index is categorized into low (2 or less), moderate (between 3 and 5), high (between 6 and 7), very high (between 8 and 10) and extreme (greater than 11). The human health effects and precautions relating to the UV Index are summarized in the following table. Source: The UV Index Poster: Environment and Climate Change Canada

context Minimal sun protection required for normal activity.
context Wear sunglasses on bright days. If outside for more than one hour, cover up and use sunscreen.
context Reflection off snow can nearly double UV strength. Wear sunglasses and apply sunscreen on your face.
context Take precautions - cover up, wear a hat, sunglasses and sunscreen especially if you will be outside for 30 minutes or more.
context Look for shade near midday when the sun is strongest.
context Protection required - UV radiation damages the skin and can cause sunburn.
context Reduce time in the sun between 11 a.m. and 3 p.m. and take full precautions - seek shade, cover up, wear a hat, sunglasses and sunscreen.
context Extra precautions required - unprotected skin will be damaged and can burn quickly.
context Avoid the sun between 11 a.m. and 3 p.m. and take full precautions - seek shade, cover up, wear a hat, sunglasses and sunscreen.
context Take full precautions. Unprotected skin will be damaged and can burn in minutes. Avoid the sun between 11 a.m. and 4 p.m., cover up, wear a hat, sunglasses and sunscreen.
context White sand and other bright surfaces reflect UV radiation and increase UV exposure.
context Values of 11 or more are very rare in Canada. However, the UV Index can reach 14 or more in the tropics and southern U.S.

What workers are at risk?

All outdoor workers potentially exposed to the sun's ultraviolet radiation are at risk, including: Indoor workers exposed to UV would include those in tanning salons or where UV-producing devices are used (e.g., medicine, cosmetics, etc.).

context agricultural workers
context farmers
context horticultural workers
context maintenance workers
context pipeline workers
context ranchers
context athletes
context fishermen
context landscapers
context military personnel
context police
context ski instructors
context brick masons
context gardeners
context lifeguards
context oilfield workers
context postal carriers
context sailors
context construction workers
context greenskeepers
context loggers
context open-pit miners
context railroad track workers
context surveyors

How can I reduce the risk of skin cancer from sunlight?

It is important to be aware of the risks and take precautions while under the sun from as early in life as possible. Approaches to prevent skin cancer include: In the winter time, it may be advisable to the above precautions when exposed to sun for prolonged periods, especially in the presence of snow or at high altitudes.

requirement reducing exposure to sunlight
ppe wearing protective clothing
requirement using sunscreens on exposed skin
requirement examining the skin regularly for suspicious spots

Reducing Exposure

requirement Workers should avoid unnecessary exposure to the sun, especially to the intense midday rays between 11:00 a.m. and 3:00 p.m. during the summer. If possible, people should plan outdoor work for early morning or late afternoon, and work in the shade as much as possible. Umbrellas, buildings, shade structures, trees, canopies, etc., can protect against the direct rays from the sun. Work, and take breaks in the shade when ever possible. Set up shade structures when shade is not available. In addition, water, white sand or concrete, snow, and ice can reflect from around 10 percent to 85 percent of the sun's ultraviolet radiation. Skin may require extra protection against these indirect, reflected rays.
administrative Workplaces can also rotate workers between site locations to help reduce UV exposure.

Wearing Protective Clothing and Sunglasses

requirement The use of wide brim hats and clothes made from close-knit fabric can protect the skin and scalp from ultraviolet radiation. Although long-sleeved shirts and long-legged pants may not be comfortable in extremely hot weather, they do help protect the skin. Clothing specifically designed to be sun protective or sun blocking will indicate the protection rating (a UV protection factor, or UPF). Be aware that not all clothing offers the same protection. Factors include the colour of the clothing, construction, materials the item is made from, fit, and coverage over the body. Some fabrics lose their SPF rating when they get wet. Workers should be informed about different fabric characteristics that effect the transmission of sunlight.
requirement Wear wrap-around sunglasses that absorb UVA and UVB radiation.

Using Protective Sunscreens

Workers should liberally apply protective sunscreen on exposed skin 20 minutes before working in the sun, then reapply it during the periods they spend under the sun, as directed by the manufacturer's instructions (usually every two hours). Most sunscreens are colourless, invisible, and cosmetically acceptable. Sunscreens should be used in addition to, not instead of, working in shade and wearing suitable clothing, hats, and sunglasses. Sunscreens are not intended to extend the exposure time to sunlight, but rather to reduce the effects of sunlight when people have to be in the sun. The level of protection depends greatly on how the sunscreen is applied. A wide variety of sunscreens are available. They all contain chemical ingredients that weaken (but do not eliminate) the effects of ultraviolet radiation. The most widely used protective chemicals are PABA (para-aminobenzoic acid) and closely related chemicals such as cinnamates, salicylates, benzophenones, or anthranilates. Some sunscreens contain only one of these protective chemicals while others may have two or more for greater reliability. Manufacturers label sunscreens with a sun protection factor (SPF). The higher the factor, the greater the protection from the sun. The Canadian Cancer Society recommends a broad spectrum sunscreen (protects against UVA and UVB rays) with an SPF of 30 or higher. Follow the manufacturer’s directions. A sunscreen's effectiveness also depends upon its ability to withstand heat, humidity and sweat. For example, sunscreens should be applied 20 minutes before going outdoors, and reapplied every two hours, or more often if perspiring (sweating), swimming, or working in water. Use a broad spectrum lip balm with an SPF of 30 or higher as well. People with skin sensitive to sunlight should use a sunscreen with a high SPF.

requirement SPF 15 sunscreen may absorb 93 percent of UVB radiation.
requirement SPF 30 sunscreen may absorb 97 percent of UVB radiation.

Examining Skin Regularly

People who work under the sun should examine their skin regularly for any unusual changes. The danger signs include any wound, sore, or patch of skin that won't heal or constantly scales. Also examine for any growing lump, particularly if brown or bluish in colour. It is important to get medical care for anything that looks suspicious rather than wait until the problem becomes untreatable.