After a long Canadian winter or on a warm-weather vacation, you probably want to soak up as much sunshine as you can. However, excessive sun exposure, as well as multiple or severe sunburns, can increase your risk of skin cancer. People with fair skin, or lots of freckles and moles, are at even greater risk, and children are more likely to suffer long-term damage from sun exposure, as their skin is thinner and more sensitive than an adult’s.
We’re not saying that you should stay cooped up out of the sun – there’s nothing better than enjoying beautiful weather outside – but ultraviolet (UV) radiation can cause a lot of harm. There are steps you need to take to keep yourself safe, including wearing protective clothing, applying sunscreen and understanding when UV radiation is the strongest.
Sun protective clothing
Wearing a bikini made of sunproof materials won’t offer you much in the way of protection, since it only covers a small portion of your body. When it comes to sun safety, coverage is everything. Things like wide-brimmed hats, long sleeves and longer shorts are all effective means of minimizing your exposure – but bear in mind that not all materials are created equal.
UPF rating for clothing
To know how strong or weak a material’s sun protection is, you need to pay attention to its UPF (Ultraviolet Protection Factor) rating. Canada doesn’t have its own standards for measuring and assigning UPF ratings. MEC voluntarily uses the Australian/New Zealand Standard for Sun Protective Clothing (AS/NZS 4399) for some MEC Label clothes to give you a relative indication of how well they guard against ultraviolet radiation. As a rule, the higher the rating, the higher the level of protection from UV rays.
AS/NZS 4399 UPF ratings and the UV-R protection classification levels they provide:
|UPF rating||UV-R protection classification||Effective UV-R penetration ≤ %|
|50, 50+||Excellent protection||2.0|
UPF ratings range from 15 to 50+ based on the percentage of UV rays they block:
If a long-sleeve shirt has a UPF rating of 30, it only lets one-thirtieth (3.3%) of solar radiation reach your skin.
A basic white cotton t-shirt provides a UPF of around 5 when dry, which allows about 20% of UV rays to pass through.
In general, garments with that cover more of your skin and that are made of materials with a tighter weave or knit provide higher levels of overall sun protection.
As clothing gets damaged, wet, worn or stretched, its UPF rating decreases.
Due to their polymer structure, synthetic fibres such as polyester, nylon, spandex and acrylic are generally better UV disruptors than natural fibres like wool, cotton and linen.
Some UV-protective garments are additionally treated with compounds, fluorescent brighteners or special resins that absorb or reflect UV rays. MEC requires these materials to be preconditioned in accordance to the American Society for Testing and Materials (ASTM) D6544 before testing to assess the long-term durability of the UV-resistant finish. According to the ASTM, a garment with a UPF treatment must undergo 40 simulated launderings, withstand the equivalent of two years’ exposure to sunlight, and (for swimwear) be exposed to chlorinated water.
Sunscreen and SPF
You’ve probably noticed that the UPF ratings on clothes look a lot like the SPF ratings on sunscreen – but the two systems are not the same.
SPF (Sun Protection Factor) ratings measure how long it takes for a person’s skin to redden in the sun, which means they’re more targeted toward the superficial effects of UVB radiation. For now, there’s no unifying standard for testing how well a sunscreen blocks the more pervasive UVA radiation, even though “broad spectrum” sunscreens claim to protect against both types of UV. Many professionals recommend using broad spectrum products as a precautionary measure regardless.
It’s also worth noting that the UPF rating of clothing is relatively consistent over time, notwithstanding regular wear and tear; sunscreen, on the other hand, is affected by things like sweating, swimming and towelling off, and needs to be reapplied regularly.
Some things to remember regarding sunscreen:
Most people benefit from sunscreens with an SPF of 15 or more.
A sunscreen with SPF 15 blocks about 93% of UVB rays, while SPF 30 blocks 97%. The Canadian Cancer Society recommends using an SPF 30 or higher.
Sunscreen should never be used on infants under 12 months; instead, they should be kept shaded and out of the sun, with a hat and clothing.
Sunscreen should be applied 15–30 minutes before spending time in the sun, and before applying insect repellent.
Sunscreen should be reapplied every 2 hours, even if the label claims that it lasts longer. For climbers or endurance athletes who can’t stop every 2 hours, we recommend a product with an SPF of 45 or 60, as the higher initial chemical load will provide a slighter higher protection.
UV radiation: what you need to know
The sun’s visible and invisible radiation comes in a variety of wavelengths; the shorter the wavelength, the more intense the radiation, with ultraviolet radiation being the most intense. There are three types of UV radiation: UVA, UVB and UVC. Because UVC rays are absorbed by the atmosphere before they reach the ground, it’s UVA and UVB rays that are of greatest concern to us.
UVA vs. UVB rays
UVA rays make up the majority of UV radiation – about 95% – and can penetrate deep into skin to cause structural damage and aging. They also contribute to the development of skin cancers, which are some of the most common types of the disease. UVA radiation is relatively constant year-round during all daylight hours.
UVB rays are almost 1000 times stronger than UVA rays. They damage the outermost layer of the skin, can cause sunburns and surface skin aging, and are closely linked to the development of cancer and cataracts. Unlike UVA radiation, UVB varies by season, location and time of day. It tends to be strongest at midday, through the late morning and early afternoon, when the sun’s rays reach the earth at a straighter, more direct angle.
Tips to keep yourself safe from UV radiation
Remember this info when you’re planning to play outside:
In North America, sunlight is strongest between 10am and 4pm, and between April and October.
Skiers, hikers and mountaineers should remember that UV radiation gradually increases with elevation gain – about 10% for every 1000m. Bring sunscreen as part of your 10 essentials.
Fresh snow can reflect up to 94% of UV rays, nearly doubling your exposure, so protect yourself during winter sports, especially on clear days. For comparison, water and grass reflect less than 10%, while sand reflects approximately 15%.
Clouds can reduce UV on the earth’s surface, but it depends on the thickness of the cover – which can be difficult to gauge from the ground. Don’t let overcast skies lure you into a false sense of security.
Depletion of the ozone layer increases the amount of UV that penetrates the atmosphere. In Canada, our ozone layer tends to be at its thinnest in the late summer through fall.
If you’re taking any medication, ask your doctor or pharmacist if it can increase your sensitivity to sunlight. Antibiotics such as doxycycline and tetracycline, which many people take while travelling abroad, might make you more vulnerable to UV. Common over-the-counter drugs can also increase photosensitivity, including anti-inflammatories like Advil and antihistamines like Benadryl.