Overexposure to the sun and other sources of ultraviolet radiation (UVR) are known to cause harm to the skin, eyes and immune system.1 About 65% of melanomas worldwide can be attributed to UVR exposure, with well over 90% among white populations.2 Exposure to UVR also increases the risk of ocular melanoma, cortical cataracts and a number of other eye conditions, while the sun’s visible light, specifically in the blue light range, increases the risk of age-related macular degeneration.3 UVR immune system effects include increased susceptibility to infection and activation of latent virus infections (e.g., herpes simplex, human papillomavirus).4
As far as we know, skin cancer represents the greatest burden of disease related to sun exposure worldwide4 and is the most common form of cancer in Canada.5 The burden of eye disease related to sun exposure has not been well quantified.6 The incidence of melanoma, the most fatal form of skin cancer, ranks sixth after prostate, breast, colorectal and lung cancers, and non-Hodgkin lymphoma. Among Canadians aged 15 to 29 and among those aged 30 to 49, it ranks fourth in frequency of diagnosis annually.7
Between 1996 and 2006, Canadians increased their time in the sun without improving protective behaviours.8 In addition, melanoma incidence rates have been increasing in Canada and are projected to continue to rise.7
Personal protective measures against sun and UVR exposure are key parts of preventing skin cancer and other conditions. A comprehensive strategy for reducing the burden of skin cancer should therefore include efforts to increase awareness of the actions individuals should take to reduce their risk. Communicating a consistent set of recommended actions that are supported by evidence is a first step in increasing the uptake of those actions.
SUN SAFETY RECOMMENDATIONS:
Ultraviolet Radiation Exposure
- When outside and the Ultraviolet (UV) Index is 3 or higher, there is risk of harm to unprotected skin and eyes.
- The UV Index regularly reaches 3 and higher between the peak hours of 11:00 a.m. and 3:00 p.m. (daylight savings time [DST]; 10:00 a.m. to 2:00 p.m. standard time), from March to October on sunny and cloudy days.
- The UV Index regularly reaches 5 and higher between 11:00 a.m. and 3:00 p.m. (DST) from May to August, but rarely exceeds 10 in Canada.
- Infants, young children and people with fair skin that burns easily are especially vulnerable to UV exposure.
Recommended Protective Actions:
- When the UV Index forecast is 3 or higher, generally from March to October, plan outdoor activity before 11:00 a.m. and after 3:00 p.m. whenever possible for the best protection.
As a general guide, if outside for 15 minutes or more during peak hours:
- Seek both shade AND use personal protection (hats, protective clothing, and sunglasses; and sunscreen on non-covered skin) from May to August.
- Seek shade OR use personal protection in early spring and fall (March, April, September and October).
- Check the weather forecast for the daily UV Index forecast (http://weather.gc.ca).
- Protecting the skin of infants, young children and people with fair skin that tends to burn easily is especially important.
- Ensure infants younger than six months of age are always kept out of the sun—in the shade and wearing protective clothing when outside; sunscreen may be used on infants younger than six months on small areas of skin, if adequate clothing and shade are not available.
- Even when in water, sun protection is needed.
- UV radiation can pass through cloud cover.
- When around snow-covered surfaces (e.g., in the mountains), from March to November, sun protection is needed from 11:00 a.m. to 3:00 p.m. (DST). Snow reflects and intensifies UV radiation, but when the UV Index is low, intensification is minimal.
- Environment Canada’s daily UV Index peak time forecasts are available here: http://weather.gc.ca/forecast/public_bulletins_e.html?Bulletin=fpcn49.cwao.
- UV radiation increases with altitude, so sites at higher elevations receive more UV radiation than those closer to sea level.
- It is important to adjust to local conditions.
What does the evidence say?
Ultraviolet radiation (UVR) is a portion of the electromagnetic spectrum, and is further divided into the UVC (shortest), UVB and UVA (longest) wavelengths. Sunlight is made up of UVR, as well as an additional two portions of the electromagnetic spectrum—infrared and visible light.The Ultraviolet (UV) Index is a measure of sunburn response to levels of UVR intensity.14 The UV Index ranges from 0 (low intensity, usually at night) to 11 (extreme intensity, usually at solar noon on a clear summer day at the Earth’s northern mid-latitudes). The UV Index very rarely exceeds 10 in Canada.15 When the UV Index is 3, it takes about an hour to get the first perceptible sign of reddening (i.e., erythema) for skin type II (i.e., skin that burns easily, but can develop a tan). When the UV Index is 10, it takes just 17 minutes to get the same UV dose.14Environment Canada developed the UV Index and issued the first forecasts in 1992.16 In 1994, the World Meteorological Organization and the World Health Organization adopted the index as an international standard and updated it to the current 11-point scale.14
The UV Index changes with the time of day and season, specifically with changes in the local solar zenith angle; in other words, UVR is greater when the sun is closer to being directly overhead. The daily peak UV Index is therefore related to solar noon. In Canada, the UV Index is typically below 3 before 9:00 a.m. and after 5:00 p.m. local solar time. It is typically below 3 from October to March on any type of day. The UV Index is particularly high (above 5 on average) from May to August between 10:00 a.m. and 2:00 p.m. (solar time; 11:00 a.m. to 3:00 p.m. daylight savings time).17 As expected, the daily peak UV Index is also higher in the summer and lower in the winter.15
While UV Index declines with latitude, the differences between Toronto (44 N) and Edmonton (54 N) are not very large.17 One message should work for most of the country.
UV Index mediating factors include ozone levels, cloud cover and reflective environments, such as fresh white snow. Atmospheric ozone depletion, which varies with time and location (e.g., depletion is greater at higher latitudes), is associated with increased average UV Index levels. Local, ground-level ozone from pollution absorbs UVR.15,17 Partly cloudy skies will either magnify or mitigate UVR depending on the pattern of cloud cover and the sun’s relative position,18 while uniform cloud cover reduces UVR in relation to its thickness.19 Snow- and ice-covered surfaces can increase UVR.17
UVR also increases with altitude, so sites at higher elevations receive more UVR than those closer to sea level.15 In water, shorter UV wavelengths (UVB 280 nm to 315 nm) can penetrate to a depth of at least 30 m, and longer UV wavelengths (UVA 315 nm to 400 nm) can penetrate to a depth of at least 60 m.20
Evidence on personal protection and degree of effectiveness against UVR are in the sections that follow, but as a general rule, as the UV Index increases more protection is required (e.g., shade plus protective clothing).
Some specific populations need to exercise increased caution. Epidemiological studies suggest that children are more susceptible to increasing their risk of skin cancer through UVR exposure.21,22 People with certain phenotypic characteristics—fair skin, light eyes, blond or red hair, and a tendency to burn rather than tan when exposed to sunlight—have higher susceptibility to UVR damage and subsequent risk of all types of skin cancer.23,24
The American Academy of Pediatrics recommends limiting sunscreen use on infants younger than six months to small areas of the skin when adequate protective clothing and shade are not available, due to the increased likelihood of irritation on their not-yet-fully-developed skin.25
- Seek shade as a first line of defence when outside between 11:00 a.m. and 3:00 p.m. (daylight savings time) from March to October, or when the UV Index is 3 or higher.
- Good quality shade includes dense vegetation and covered structures that offer protection from the side and not just overhead.
- Find shade, such as under trees with dense foliage or covered structures, or create your own shade using an umbrella.
- As a rule of thumb, the protection factor under a shaded area increases as the amount of visible bright sky decreases.
- Cloth sources of shade should be made of tightly woven fabric; if possible, look for a labelled ultraviolet protection factor (UPF) of 15.
- Additional personal protection (protective clothing, sunglasses, sunscreen) is still needed under shade to protect against reflected sunlight, especially on high UV Index days or around highly reflective surfaces.
What does the evidence say?
Shade can be an effective means for reducing exposure to solar ultraviolet radiation (UVR). A cross-sectional study showed that seeking shade may be more effective than sunscreens in preventing sunburns and reducing UVR exposure.26The ultraviolet protection factor (UPF) provides a measurement describing the effectiveness of a source of shade and other physical sources of UVR protection, such as clothing. A UPF of 15 reduces UVR by about 93%.27One factor determining a shade structure’s UPF is the amount of UVR that the structure’s material lets through. For example, how tightly woven a cloth shade structure is will determine its UPF, more so than the type of fabric used.27 Similarly, the UPF of tree cover varies based on the density of its canopy.27 Tall deciduous trees with dense, wide canopies and low foliage create the most shade and offer the highest UPF among natural sources of shade.28 A canopy with a heavy density, that blocks 90% of the sky, has a UPF of 10.29
Examples of effective built shade structures include gazebos, verandas, sails and awnings.27 Portable shade is often less effective, but is a necessary solution for places where other shade options are not available, such as the beach. Examples of portable shade include umbrellas, beach cabanas, tents and shelters that can be dismantled.28
Shade primarily reduces sun and UVR exposure by blocking radiation directly from the sun. However, nearby surfaces, objects and atmospheric particles will reflect some radiation into shaded areas, so the need for personal protection in shaded areas is not eliminated. The level of reflection varies depending on the different physical properties of objects and surfaces.27 For example, particles in the atmosphere will create diffuse reflection, or scattering,27 while fresh white snow produces a significant amount of direct reflection.17
The UPF of a shade structure is therefore also determined by the amount of reflected UVR that is blocked. Structures with an expansive roof or that have side panels offer greater protection.27 Portable shade devices often provide limited protection against reflected UVR due to their limited area of coverage.28 A shade structure that has a broad expanse can also provide protection from the sun’s direct radiation as the angle of the sun changes.30
For more information on the level of UVR protection offered by different types of shade, the Toronto Cancer Prevention Coalition’s Shade Guidelines offers detailed guidance on selecting good quality shade.28
Protective Clothing & Hats
When outside between 11:00 a.m. and 3:00 p.m. (daylight savings time) from March to October, or when the UV Index is 3 or higher:
- Wear clothing with tightly woven fabric to cover as much skin as possible.
- Choose hats with a wide brim all around made of tightly woven fabric. Hats should shade your face, ears and the back of your neck.
- Use sunscreen on non-covered skin.
- Choose synthetic fabrics or polyester blends, or look for clothing labels with a high ultraviolet protection factor (UPF) number.
- Lightweight, loose-fitting UV protective clothing can keep you cooler than bare skin in hot weather.
- Baseball hats do not provide enough protection, covering only the scalp and shading only a small part of the face.
- Don’t risk developing skin cancer while trying to keep active. When you participate in outdoor sport, cover up as much as possible.
- If you work outdoors, consider UV protective clothing designed specifically for outdoor workers, which may also keep you cooler.
What does the evidence say?
Clothing is a simple, practical and reliable means of photo protection and may be more effective than sunscreen.26,31 A common measure of the total UVA and UVB blocked by textiles is the UPF. The UPF is calculated by taking the ratio of amount of UVR emitted by the source and the amount transmitted through a sample fabric.32 Many reports have made recommendations for labelling UPF on photo protective clothing;33–36 however there are no set guidelines. According to recommendations from Australia, to make the claim of good protective properties, clothing must have a UPF greater than 15;35 more recent recommendations from the European Committee for Standardization require fabrics to have a UPF greater than 40 in order to be labelled as offering UV protection.36
Many factors affect transmission of UVR through fabrics. In vitro studies have shown greater UV protection is provided by clothing made with tightly woven fibres, including synthetic fabrics, darker colours and polyester blends; denim or wool will also provide protection, but may not be practical in warm weather.31,37 These can include lightweight and loose-fitting clothing. Loosely woven and light-coloured fabrics offer lower levels of protection.31 With wear and use of a garment, additional factors can decrease the UPF including stretchiness, wetness (depending on the fabric, wetness can also increase UPF) and degradation by washing,32,33 but many UPF-rated fabrics can withstand repeated washings.
Hats provide additional yet variable sun protection. There are many factors that affect the amount of protection provided by hats. In general, tightly woven fabric, presence of a large brim, good coverage of the ears and back of the neck are factors that enhance photoprotection.32 Brims should extend around the whole hat and be at least three inches wide.38
A common misconception about protective clothing is that it would be too hot to wear in warm weather. However, lightweight, loose-fitting clothing, which people in hot desert regions traditionally wear, can help to keep the body cooler. A number of modern fabrics designed for sportswear also have moisture-wicking, quick-drying and highly-breathable properties.
Sunglasses that completely shield the eyes protect against a number of eye diseases.
- Wear close-fitting, wraparound sunglasses or sunglasses with side shields, even if you wear contact lenses, when outside from 11:00 a.m. to 3:00 p.m. (daylight savings time), from March to October.
- Wear sunglasses any time you are in highly reflective environments, such as on snow, water or sand.
- For effective protection, sunglasses should provide coverage from direct and indirect sunlight.
- Brown-tinted sunglasses generally provide better protection than other tint colours.
- Prescription sunglasses and sunglasses that fit over your regular non-treated prescription glasses are available.
- Most modern, non-tinted prescription glasses are treated to provide ultraviolet (UV) protection.
- In situations where you can’t wear sunglasses, use either prescription or non-prescription (plano) ultraviolet absorbing contact lenses.
What does the evidence say?
Chronic exposure to ultraviolet radiation (UVR) is a risk factor for several eye-related disorders, including ocular melanoma, cortical cataracts, pterygium, and some corneal and conjunctival neoplasms. 6,23,39 Acute exposure to UVR can also cause photokeratitis, photoconjunctivitis and retinal burns (e.g., from looking directly at the sun).40 However, age-related macular degeneration (AMD) is more likely related to exposure to the visible light portion of sunlight, specifically the blue light range.3
For eye protection in most situations, including driving, Health Canada recommends using general purpose sunglasses, which block 60% to 92% of UVA rays and visible light and 95% to 99% of UVB rays.41 The percentage of UVA rays and visible light that is blocked is related to the density of the tint.42 While most sunglasses protect the eyes from the sun’s direct radiation, neither sunglasses nor hats generally provide adequate protection from indirect sunlight or sunlight reflected from nearby surfaces and objects. The greatest protection for eyes against sunlight is provided by ski goggles and wrap-around sunglasses. UV-absorbing soft contact lenses can protect the inner eye structures from UVR; however, the lids and conjunctiva remain unprotected from UVR, and the lenses do not offer protection in the visible light spectrum.40
Among the range of tints that minimally affect colour perception, brown-tinted lenses generally offer the best protection, protecting against both UVR and the blue light portion of the sun’s visible spectrum.42
Sunscreens must have a sun protection factor (SPF) of 30 or higher, be broad spectrum and water resistant, and applied with a generous layer on all exposed skin to work effectively.
- Sunscreens should be used on exposed skin not covered by protective clothing, which offers more effective skin protection.
- Use a generous amount of sunscreen. Reapply sunscreen based on activity level, immediately after swimming, towelling off or sweating heavily.
- When choosing a sunscreen, look for one that is:
- Broad spectrum, protects against ultraviolet A (UVA) and ultraviolet B (UVB)
- SPF 30 or higher
- Water resistant
- Applying sunscreen about 15 minutes before going outside helps your skin to absorb it before exposure, but once outside, it’s not too late to apply.
- Health Canada recommends reapplying sunscreen every two hours.
- Sunscreens come in a variety of formulations. Find one that suits you best.
- In Canada, all sunscreens have passed a review by Health Canada and are given a drug identification number (DIN).
- Reviews of studies of a number of common sunscreen ingredients have not shown that those ingredients, including oxybenzone (benzophenone-3), pose health risks.
What does the evidence say?
Sunscreens reduce the amount of ultraviolet radiation (UVR) absorbed by the skin, preventing sunburn and other UVR-induced changes in the skin.43 The SPF is a ratio of the least amount of solar-simulated UVR required to produce a minimum amount of redness (i.e., erythema) in sunscreen-protected skin compared to unprotected skin, 24 hours after exposure.44 As with UPF, the SPF of a sunscreen can also be calculated as the ratio between UVR transmitted without protection to the amount of UVR transmitted with sunscreen-protected skin.45 SPF 15 allows 7% of UVR through or filters 93%, while an SPF of 30 allows 3% of UVR through, filtering 97%. SPFs higher than 30 offer a smaller increase in filtration capacity (e.g., SPF 60 filters 98% of UVR). Because UVB is many times more erythemogenic (able to cause redness of the skin) than UVA, the SPF is primarily an indicator of UVB protection.
For a sunscreen to be labelled as broad spectrum, protecting against UVB and UVA, Health Canada requires that they have a critical wavelength protection of at least 370 nm.46 The critical wavelength is a measure of the breadth of absorbance. A critical wavelength of 370 nm extends protection into the longer wavelength portion of the UVA spectrum.
Sunscreens have been shown to also protect against the development of squamous cell carcinoma (SCC) of the skin and its precursor, actinic keratosis (AK).47–49 Strong evidence of protection against basal cell carcinoma is lacking. Randomized studies in British Columbia (BC) and Australia provided some evidence that sunscreens may protect against melanoma. The BC study noted that children who regularly used broad-spectrum, high SPF sunscreen developed significantly fewer nevi during the study than those in the control (“as usual” use) group.50 In Queensland, Australia, long-term follow-up of participants in a randomized study of sunscreen use (only SPF17 was available at the time) found a significantly reduced risk of melanoma in the sunscreen arm of the trial.51
There are likely several reasons for the limited evidence about sunscreen use and reduced risk of melanoma and basal cell carcinoma. In particular, it may be that the UVA part of the spectrum is more important in the development of these cancers compared to squamous cell carcinoma, but good UVA absorbers are relatively new. In addition, the recommended application density set by the United States Department of Health for standardized SPF testing is 2 mg/cm2 (or 35 ml of sunscreen per body application), when in reality, the actual amount of sunscreen used by consumers is well below that, to the point where there may be often no to minimal protection on hairy skin and areas of the body that are hard to reach.52,53 Studies have found that the amount of sunscreen used in real life situations ranges from 0.5 to 1.3 mg/cm2.
Since sunscreen is generally not used appropriately, the protection achieved is typically about one third of the labelled SPF.54 Proper use and reapplication are likely primary considerations to promote.52 However, where previous sun protection messages recommended SPF 15 sunscreens, SPF 30 is now recommended.55,56 SPF 15 may be enough for erythema, but the appropriate SPF values for other endpoints such as DNA damage, immunosuppression and carcinogenesis are not known, making the case for the use of higher SPF sunscreens.
While it is clear that swimming and sweating heavily will result in the need for reapplication, it is less clear whether reapplication of sunscreen is required every two hours. Previous research suggested that reapplication every two hours may be beneficial; however, more recent research suggests that sunscreen still has about 43% of its initial protective effect after eight hours on a day with physical activity and bathing57 and measures only a 25% reduction in SPF after a day without physical activity or UV exposure (e.g., with indoor sedentary work).58
In terms of the safety of sunscreen ingredients, the European Union Scientific Committee on Cosmetic and Non-Food Products (EU SCCNFP) has published a number of comprehensive reviews on common sunscreen ingredients, including oxybenzone (benzophenone-3) and homosalate. For these two ingredients, the committee concluded that up to recommended concentration limits, they do not pose a hazard to human health.59–61 Additional committee reviews of sunscreen ingredients may be located through the European Union CosIng database (http://ec.europa.eu/consumers/cosmetics/cosing/).
Tanning Equipment & Tanning Beds
There is no such thing as a safe or healthy tan. Exposure to ultraviolet A (UVA) and UVB radiation from tanning equipment can cause sunburn and eye damage, as well as increase the risk of skin cancer and other UV-related negative health effects.
- A “base tan” provides little to no protection against sunburn. Any tan or change in skin colour is a sign of skin damage.
- Tanning is not a safe source of vitamin D. The best way to maintain a healthy level of vitamin D is through taking a vitamin D supplement and including D-rich food sources, such as milk or milk alternatives, such as fortified soy and almond beverages, in your diet.
What does the evidence say?
UV-emitting tanning devices are classified by the International Agency for Cancer Research (IARC) as carcinogenic to humans (Group 1). There is sufficient evidence that UV-emitting tanning devices cause cutaneous and ocular melanoma. There is limited evidence that UV-emitting indoor tanning devices cause squamous cell carcinoma.23
The World Health Organization has issued a recommendation against the use of tanning equipment—especially by people under the age of 18.62,63
Ever-use of indoor tanning devices increases the risk of cutaneous melanoma by 15% to 22%,64,65 with evidence that risk increases with greater frequency of use.66–68 The few studies that have examined ocular melanoma risk have shown from 30% to as much as three times the risk compared with non-users for the highest exposure categories.23 There is also some indication of a positive dose-response relationship.23
The use of UV-emitting indoor tanning devices during adolescence and young adulthood may be associated with a particularly high risk of cutaneous and ocular melanoma.23,64,69,70
There are safer ways to maintain healthy vitamin D levels than through ultraviolet (UV) exposure.
For bone health, seek sources of vitamin D that are safer than UV exposure:
- Take a daily vitamin D supplement of 400 to 1,000 international units (IU) to ensure that you maintain healthy vitamin D levels all year round.
- Include in your diet:
- Naturally-occurring food sources of vitamin D, such as egg yolk, as well as salmon, tuna, mackerel and other fatty fish
- Milk, fortified milk alternatives, such as soy and almond beverages, and margarine provide a major source of vitamin D.
- Tanning beds are not a safe source of vitamin D.
What does the evidence say?
Dietary intake and taking a supplement are safer ways to maintain healthy vitamin D levels, where the risk of skin cancer due to UV exposure has been well established.
There are a few naturally occurring dietary sources of vitamin D, including fatty fish, fish liver oil and egg yolk.71 It is also mandatory that certain foods in Canada be fortified with vitamin D, namely milk and margarine.72 Other foods have optional fortification, including plant-based beverages (e.g., soy milk), some fruit juices, cereals, yogurts and cheeses.72
Recommended dietary allowances (RDA) from the Institute of Medicine (IOM) (2010) suggest that, as a general population health recommendation, a total dietary intake of 600 IU/day of vitamin D should meet the needs of most people in the United States and Canada, although adults over the age of 70 may need 800 IU/day.71
In Canada, exposure to sunlight and dietary intake alone are insufficient to maintain adequate levels throughout the year.73,74 In the United States, diet accounts for only 148 to 236 IU/day.75 In Canada, the estimate is slightly higher, at 176 to 264 IU/day.71 The most recent Canada Food Guide (2007), recommends that adults over the age of 50 take a daily vitamin D supplement of 400 IU.76 For bone health, guidelines from Osteoporosis Canada recommend a vitamin D supplement of 400 to 1,000 IU/day for most adults under the age of 50.77 The recommendation for individuals over the age of 50 or at risk for osteoporosis or vitamin D deficiency are 800 to 2,000 IU/day.77,78 Supplementation should not exceed 2,000 IU/day without medical supervision.77
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