Sun safety - how much is too much?

Some exposure to sunlight is essential for your health, but too much can be dangerous.
 
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  • Updated:10 Oct 2005
 

01 .Sun safety

Woman applying sunscreen

What is UV radiation?

Sunlight is made up of various types of radiation. Across the full radiation spectrum, it’s mostly visible light and infrared heat that reach the earth’s surface. But it’s ultraviolet radiation, or UVR, that’s the most dangerous for your skin.

There are three types of UVR:  

  • UVA penetrates the skin, causes wrinkles and discolouration, and has been implicated in skin cancer
  • UVB is the most dangerous type, even though it’s mostly blocked by the earth’s ozone layer. Exposure to UVB causes sunburn, which can lead to permanent skin damage and cancer
  • UVC is less dangerous to skin and is in any case almost completely absorbed by the ozone layer, so it’s not a major cause for concern.

Please note: this information was current as of October 2005 but is still a useful guide today.


How to protect yourself from the sun

It's not hard to protect yourself from sunburn. Sunscreen, the right clothing, a hat and sunglasses and a bit of common sense are all you need.

Time of day

  • Keep out of the sun between 10 am and 2 pm (or 11 am and 3 pm during daylight saving)
  • Stay in the shade. But watch out for reflected UVR: indoor or grassy areas generally have less reflected UVR and therefore give better protection than areas with bright reflective surfaces like concrete, sand, snow or water
  • Clouds absorb or scatter some UVR, but not all of it. You can still get sunburnt on cool or cloudy days
  • Watch the UV index on weather reports as a guide to how much sun protection you'll need each day.

Sunscreens

If you're not using this much (as shown in the image to the right) - about six teaspoons - every time you put sunscreen on your whole body, you're probably not getting enough protection from UV. Sunscreen covering palm

  • SPF 30+ is best; it blocks about 97% of the sun's rays
  • Broad-spectrum sunscreens protect you against both UVA and UVB, ordinary sunscreens against UVB only
  • Water-resistant sunscreens are important if you're swimming, because UVR penetrates water for up to a metre. Reapply the sunscreen every two hours and after each swim (you're likely to towel some of it off anyway)
  • Use enough. There's reasonable evidence that a lot of people don't. About six teaspoons (30 mL) are needed for your whole body so if your head, neck, arms and legs (and maybe midriff) are all bared to the sun on a normal day you'll need a good proportion of that amount. It's a good idea to apply it once on the bits that aren't under clothing 20 minutes before you plan to go out and once again just before you go. You'll get better coverage, probably be using more like the right amount and be giving time for the sunscreen to interact and bond with your skin. Don't rub it into your skin; it should glide on like a coat of paint
  • Store your sunscreen in a cool place, as it can lose effectiveness if left somewhere hot like a car's glovebox for long periods. Throw away sunscreens that are past their expiry date, or that have gone gluggy or separated. The active ingredient may still be OK, but it may not spread evenly on your skin, which could result in patchy sunburn
  • Don't forget your lips: sunscreen can wear off them quickly. Alternatives are a lip balm with a high SPF or a thick zinc or titanium oxide sunblock
  • Manufacturers of sunscreens of SPF 4 or over have to be licensed by the Therapeutic Goods Administration and demonstrate that their products meet the claimed SPF, so you can be pretty confident that any SPF 30+ broad-spectrum sunscreen will do the job. Choose according to price and your personal preference
  • Sunscreens are quite safe, but young kids and people with sensitive skin may benefit from a low-irritant version.

Clothing

  • Medium-weight clothing will protect the areas it covers. Clothes that are too lightweight or have worn thin won't give good protection. Light colours let more light through than dark colours unless the material is thick enough to ensure the light is mostly reflected. So dark-coloured fabric usually provides better UV protection. But don't worry about this too much; a good medium or heavyweight white T-shirt, for example, will still protect your back
  • To protect yourself in the water, wear a shirt while swimming, but if it goes transparent when wet it'll be less protective. Consider special high-UPF swimwear, designed to be sunproof even in the water. (UPF is the clothing equivalent of SPF: for more see UPF.)
  • A broad-brimmed hat or legionnaire-style cap with a neck-drape, or even a scarf around your head and neck, will help protect your face and neck.

Sunglasses

  • Your eyes can also be damaged by long-term exposure to UVR, so put on a good pair of sunglasses along with your shirt, hat and sunscreen
  • Look for sunglasses labelled general-purpose or specific-purpose with traditional brown or grey lenses (rather than fashion or unlabelled sunglasses), as these offer the best UV protection
  • Ideally choose larger lenses: at least as big as a 20 cent coin with a wraparound style to cover the top and sides of your eyes
  • Normal prescription glasses (especially those with polycarbonate plastic lenses) give some UV protection, but for maximum protection consider getting prescription sunglasses as well. Alternatively, have your usual glasses treated with a clear UV-protective coating

Nutrition

  • There's evidence to suggest that a low-fat, high-fibre diet with plenty of vegetables and fruit and not too much red meat reduces the risk of certain types of cancer, and of course it'll help keep you healthy generally. However, connections between nutrition and skin cancer in particular aren't well understood, though one study has suggested that vitamin A may help reduce melanoma risk in some people.
 
 

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02.How much sun do you need?

 

You need some exposure to sunshine

Your body needs sunlight to produce vitamin D, which helps strengthen your bones and muscles and may also help prevent diseases such as multiple sclerosis and certain cancers. Your diet will provide some vitamin D, mainly from fatty fish (such as salmon and mackerel), liver and some fortified foods like margarine, but most of your needs come from exposure to sunlight.  

How much sun should you get?

Surprisingly little, according to a recent study by Australian universities. In summer in most Australian cities, you need as little as five to seven minutes a day (at mid-morning or mid-afternoon, outside the hottest part of the day). Even in southern areas like Melbourne and Hobart you only need eight or nine minutes at most. And that’s not on your whole body, either: just on your face, hands and arms is enough. (This assumes a moderately fair skin.)

Groups at risk of inadequate sun exposure

Most of us probably get more than enough sun, but some people are at risk of not getting enough. They include:

  • Elderly or infirm people who live mostly indoors and can’t get outdoors much.
  • Dark-skinned people: dark skin needs more sun to make vitamin D than fair skin.
  • Women who wear veils and covering clothing as part of their culture or religion.
  • People with skin cancer or conditions (such as lupus) where sun avoidance is necessary. They need to strike a careful balance between necessary and harmful time in the sun, and may need dietary supplements to keep up their vitamin D levels.

Optimum time for sun exposure

Recommended sun exposure times
(minutes, in order of shortest to longest times in winter)*
REGION WINTER:
Jul–Aug, at
10 am or 2 pm
WINTER:
Jul–Aug, at noon
SUMMER:
Dec–Jan, at
11 am or 3 pm**
Cairns (A) 9–12 7 6–7
Townsville (A) 9–13 7 5–7
Brisbane (A) 15–19 11 6–7
Perth (A) 20–28 15 5–6
Adelaide 25–38 19 5–7
Sydney 26–28 16 6–8
Melbourne 32–52 25 6–8
Hobart 40–47 29 7–9

 

Results of too much sun exposure

Some sunlight is good for you, but too much exposure to UVR and you can pay a heavy price.

  • Tanning: A suntan may seem desirable, but in fact it’s a sign of skin damage. A natural tan does give a bit of sun protection, but only about SPF 4. Solarium tans provide even less protection.
  • Premature aging: Ongoing tanning can lead to your skin aging prematurely — becoming dry and wrinkled — and may lead to skin cancers.
  • Sunburn is like any burn, painful and damaging to your skin. If you notice sunburn appearing on your skin, it’s too late to start slapping on sunscreen — the damage is already done. Get out of the sun and drink plenty of water in case you’ve become dehydrated too. If the burn is painful, bathe it in cool water. Apply moisturiser or a sunburn treatment to the affected areas. For severe sunburn, or if you feel faint or nauseous, get medical help immediately.
  • Skin cancer: The worst possible result of too much sun. There are three main types:
    • basal cell carcinoma
    • squamous cell carcinoma
    • melanoma

Of these, melanoma is the deadliest and can spread quickly. Skin cancer comes not just from the damage done to skin by UVR, but also from the way UVR suppresses your immune system, weakening your defences against cancer.

Although detection and treatment of skin cancer has greatly improved in the last 20 years, around 1300 Australians still die each year from skin cancer. Check your skin regularly for suspicious spots, such as non-healing sores, red or pale lumps, or a mole or freckle that changes colour or size. If you find any suspicious spots, ask your doctor about them.

SPF: Sun Protection Factor

This is the factor by which the sunscreen increases the time it takes you to get sunburnt. A properly applied coat of SPF 30 sunscreen will keep you burn-free for 30 times longer than normal, so if you’d normally get mild sunburn in 10 minutes, the SPF 30 sunscreen will in theory keep you burn-free for 300 minutes, or five hours. (Not that it’s wise to spend that much time in the sun even with sunscreen on, especially if your skin is really so fair it would normally start to burn in 10 minutes. It just gives you a sense of the safety margin sunscreen can give you.)

In any case it’s a good idea to reapply sunscreen every two hours, because water and sweat wash away the coating on your skin.

The highest claimable SPF rating in Australia is 30+. This isn’t because SPF 30 is ‘good enough’ (although it does block 97% of the sun’s rays), but rather because the SPF measurement method isn’t completely reliable once the SPF exceeds 30. Some products labelled SPF 30+ may be much higher.

SPF multiplies, so if you’ve covered yourself with SPF 30 sunscreen, then put on a light shirt (the equivalent of say, SPF 5), you’ve got SPF 150 protection.

UPF: Ultraviolet Protection Factor

This rating is for clothing and shadecloth: a shirt with a UPF of 20 allows only one twentieth of the UVR through to your skin. UPF ratings go up to 50, and a fabric with a rating higher than 50 is labelled as UPF 50+.

Different fabrics have different UVR-absorbing properties: generally, the thicker the fabric, the tighter the weave and the darker the colour, the more UVR is blocked. Clothes and swimsuits are available in high-UPF fabrics; look for a label showing they pass the Australian standard AS/NZS 4399.