We know we should be sun smart but what does that mean? How does sun cause skin cancer? And isn’t sun good for vitamin D?
One person dies about every five hours from skin cancer in Australia – that’s about 2000 a year – and an Australian is diagnosed with the deadliest form, melanoma, every half-hour. In fact, two out of three Australians can expect to have some form of skin cancer by the age of 70.
Many Australians, of course, wear hats and rashies and dutifully cover up their children and themselves in the sun. Yet huge portions of our population remain remarkably unclear – complacent, epivir packungsbeilage even – about what damage the sun does to our skin. “You can go to our beaches any day of the week and there’s thousands of people who are punishing their bodies, breeding their melanomas,” says Professor Richard Scolyer, co-medical director of Melanoma Institute Australia.
Nearly half of the men surveyed in Cancer Council Australia’s 2022 Sun Protection report said they often or always spend time outdoors during peak ultraviolet (UV) radiation hours in summer; less than a third said they use sunscreen. And when life insurer TAL surveyed 1000 members and potential customers in 2020, just over one in 10 believed they were “immune” from skin cancer; more than a third said they had never had a skin check; and two-thirds could not name the key signs of skin cancer (see below).
Australia’s Slip, Slop, Slap! sun safety campaign from the 1980s has since been updated to add Seek (shade) and Slide (on sunglasses). But the most recent key change to messaging is that UV levels are the way to tell when sun protection is needed.
“People often just look at sunny days and temperature to determine their behaviours,” says Megan Varlow, director of Cancer Control Policy at Cancer Council Australia. “Actually, it’s the UV levels, these invisible parts of sunlight that we can’t see or feel [that matter].”
So, what is it about “UV” that we need to know? What does the sun actually do to our skin? And don’t we need to catch some rays to top up on vitamin D?
Artwork Aresna VillanuevaCredit:
So what does the sun do to your skin?
The sun emits radiation that travels to Earth where it is absorbed by the atmosphere – except for the radiation that is not. Some of the raditation is ultraviolet. These rays are a source of both nourishment and damage to humans. Proteins in our skin convert rays into vitamin D3, essential for bone and heart health, but the rays also burn us.
The culprits are two types of ultraviolet rays. Long-wave ultraviolet A light, or UVA, penetrates deep into skin, causing melasma (greyish-brown patches), wrinkles (by damaging collagen fibres) and leatheriness (again from depleted collagen). UVA can also lead to skin cancer.
Shorter-wave ultraviolet B light, or UVB, penetrates the upper layer of our skin and is primarily responsible for sunburn and most skin cancers. Of course, both UVA and UVB rays induce tanning, too, by triggering melanocytes, which are cells that provide melanin, a brown pigment. Freckles are tiny spillovers of melanin product, and in most cases are harmless. They need to be checked by a doctor only if they are asymmetrical; have uneven notched or bumpy borders; contain a variety of colours; have a diameter larger than a pencil eraser; or have evolved (changed in size, shape, colour or elevation). Sunspots are flat brown spots that develop on areas of your skin that are exposed to the sun. They are also harmless, and only need to be checked if they are black; increasing in size; have an irregular border; an unusual combination of colours (often skin-colour and red); or are bleeding.
“Under the microscope, you can see that your skin cells are just smashed with UV damage. It’s like a car accident in your skin.”
Solariums emit both UVA and UVB radiation, which is why they are banned in all states and territories except for the Northern Territory, where there are no commercial tanning businesses.
Tan marks are a graphic illustration of the sun at work, showing the contrast between skin that has been exposed and skin that has been covered, whether the difference is created suddenly and skin is lobster red after a day at the beach, or subtly, almost imperceptibly, by incremental exposure over days, weeks and years.
But here’s the rub: there is no such thing as a “healthy tan”. Tanning is the body’s stress response to damaged DNA – the skin’s attempt to block the radiation. It is, in effect, the skin saying, “Make it stop.”
“When you go into the sun, if your skin is exposed – no sunscreen or anything over it – your skin is getting smashed by UVB photons, high-energy photons,” says Professor David Whiteman, deputy director of QIMR Berghofer Medical Research Institute in Brisbane.
When fair-skinned people, who have almost no protective melanin, go outside without sun protection, their skin “gets pulverised”, he says. “Under the microscope, you can see that your skin cells are just smashed with UV damage. It’s like a car accident in your skin. By the time you’ve got a sunburn … your body is sending out, basically, danger systems, saying, ‘I’m overwhelmed, I’ve got dead cells all over the place’.”
Meanwhile, enzymes in our bodies work non-stop to repair the damage that UV photons do to our cells and to replace damaged bits of DNA. Yet, in the face of repeated exposure, they can only do so much.
But how does the sun cause skin cancer?
When a damaged cell divides, the damaged DNA is passed on to daughter cells. Over a person’s lifetime, the cells divide many times, passing the mutation to more and more daughter cells. The key issue is where the damage occurs in the genetic code. Each cell in our body contains 30,000 genes, each with a different function.
“If [the UVB light] hits a gene that, critically, is involved in that process of cell division, then the cell can just keep dividing repeatedly, that’s how cancer starts,” says Whiteman. “Once the cell loses the ability to switch itself off and just behave, once it loses that regulation, it’s just open slather. That’s what cancer is.
Repeated sunburn, which is a radiation burn, might be the leading cause of skin cancer but it is just one of several mechanisms through which cells acquire damage that starts the cancer ball rolling. Repeated, incidental sun exposure is another significant driver. “What is known is that the more times you go out in the sun, and the more times you get damaged, the higher the probability that you’re going to hit a bad gene [that controls cell division],” says Whiteman.
Australia’s high number of fair-skinned people, the minimal amount of protective clothing that many of us wear, some regions’ close proximity to the equator (where UV levels are highest) and high temperatures (often associated with high UV levels) mean, says Whiteman, that “the odds are stacked against us [that] eventually, somewhere on your body, you’ll get a skin cancer”.
The more times you go out in the sun, and the more times you get damaged, the higher the probability that you’re going to hit a bad gene.
This partly accounts for why at least two in three Australians will be diagnosed with skin cancer before 70, according to Cancer Council Australia. By comparison, about one in five North Americans reportedly develop skin cancer in their lifetime.
“It’s purely an accident of history,” says Whiteman of Australia’s high skin-cancer rates. “Indigenous inhabitants are all deeply pigmented, and were highly selected for living in the world’s most inhospitable continent. It’s a pretty tough environment in Australia.” And it doesn’t take much to get repeated – and damaging – incidental sun exposure, especially over many decades. “Every time you go out in the sun … when you get a sandwich at lunchtime, when you go out to park your car, your skin is getting smashed, particularly from November to February, when the UV index is high, and lots and lots of photons are hitting the Earth’s surface,” he says.
How bad can skin cancer be?
About 98 per cent of skin cancers in Australia are either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC). They both start in the top layer of the skin (the epidermis) but rarely spread (metastasise) to other parts of the body, and can usually be surgically removed. They do carry risks, though. Beyond a small chance of metastasising, they can run deep under the skin, requiring the removal of a large field of tissue that can disfigure a person. When former US Vogue model Zacki Murphy was photographed after surgery to remove a basal cell carcinoma from her nose, she wrote, “My friend titled the photo Anne Boleyn after Beheading.” (Other surgeries for BCC and SCC can be more discreet.)
Melanoma, which begins in the pigment-making, or melanocyte, cells in the skin, is overwhelmingly the most dangerous skin cancer. If not caught early, it is far more likely to spread rapidly. As Science Daily once put it, “Unlike other cancers, melanoma is born with its metastatic engines fully revved.”
There are nearly 770,000 new cases of basal cell carcinoma and squamous cell carcinoma in Australia each year and about 12,000 cases of melanoma. While 722 people died of non-melanoma skin cancer in 2020, 1401 died of melanoma, an Australian Bureau of Statistics report reveals.
The five-year survival rate for patients with advanced melanoma has risen. ‘Ten years ago, it was 5 per cent. Now it’s 50 per cent.’
Melanoma can often be cured by being removed; 90 per cent of people with a melanoma less than one millimetre thick are cured after it is removed, particularly if it’s detected early. And recent advances in cancer drugs that stimulate the body’s immune response (immunotherapy) or that attack cancer cells without harming healthy ones (targeted therapy) are enabling people to survive melanoma for longer.
“A decade ago, if you had melanoma that had spread to your brain, most people would be dead in six weeks,” says Scolyer. “Now most people who have had melanoma spread to their brain are alive a year later.”
The five-year survival rate for patients with advanced melanoma has risen, too: “Ten years ago, it was 5 per cent. Now it’s 50 per cent.”
As well as our skin, our eyes can suffer damage from UV rays. In fact, basal cell carcinoma can flourish on the eyelids, says Whiteman, particularly in the inner corners. Our eyes’ lenses can be damaged by sunlight and some melanomas can arise in the retina (although rare, it is believed that sunlight is a likely contributor).
It is possible but rare to contract skin cancer that is unrelated to exposure from the sun. Most notably, some people have a variation of the MC1R gene (a key regulator of pigmentation that creates red hair, freckles and fair skin), which gives them a higher risk of developing skin cancer as a result of having faulty DNA repair mechanisms and insufficient melanin.
While noses are a common locale for skin cancer, it can appear anywhere on your body including genitals, inside the eyes, mouth, under fingernails and toenails, on the palms of hands and on the soles of feet.
Is having dark skin a protective factor?
“For people with darkly pigmented skin, their lifetime risk of skin cancer is very, very low; their need for protective steps is lower,” says Whiteman. But it’s not zero. Melanoma may be more than 20 times more common in white people than African-Americans, according to the American Cancer Society, but the fate of an individual cannot be predicted by statistics.
“You may have other genetic factors that mean that [the low probability of skin cancer] doesn’t apply to you. You might be one of the ones that are more susceptible [to skin cancer] or less,” says Scientia Professor Justin Gooding of the University of NSW.
Scolyer, who examines hard-to-diagnose skin biopsies from around the world as a diagnostic oncologist at Royal Prince Alfred Hospital in Sydney, adds this: “Many people get melanoma who’ve got a low risk … We know even people with extremely dark skin get melanoma.”
The national guidelines about sunscreen use pertain to all Australians, regardless of their skin colour.
And people with dark skin can be particularly susceptible to getting skin cancer on those areas that are not necessarily exposed to the sun. “If you spot something, get it checked quickly, says Professor Rachel Neale, head of the cancer aetiology and prevention research group at QIMR Berghofer Medical Research Institute. “People think of it [skin cancer] arising on your face, hands, torso, and when they see something under their toenail or under their feet, they don’t go, ‘That might be a melanoma’.”
Don’t we need the sun for vitamin D?
Vitamin D plays a crucial role in our health: it helps make sure we have enough calcium in our bones, and calcium plays an important role in heart and brain function. Ninety per cent of the vitamin D in our bodies comes from sunlight on our skin, the rest from dietary nutrients such as dairy products, eggs and fish. UVB rays, the same type of wavelengths that are the primary cause of sunburn, make the active form of vitamin D, called D3, in our bodies when they interact with a skin protein called 7-DHC.
Although an imprecise science, the study of vitamin D suggests people from some cultures may require less vitamin D than others. “African-Americans may not need as much vitamin D as their white counterparts to make sure they have healthy bones,” says Neale. “That evidence is emerging but not completely solid. We don’t yet know whether everybody needs exactly the same amount.”
Most Australians get enough vitamin D from incidental sun exposure even while wearing sunscreen.
The recommendation in Australia, according to the Royal College of Pathologists of Australasia and Healthy Bones Australia, is that we have at least 50 nanomoles per litre in our blood, a figure Neale says is taking no chances. By this estimate, she says, 23 per cent of Australians are deficient in vitamin D. By British standards, which recommend just 25 nanomoles, only 6 per cent of Australians are deficient. “People are unlikely to experience major harm until they get down to 25 to 30 nanomoles,” says Neale.
The bottom line? Most Australians get enough vitamin D from incidental sun exposure even while wearing sunscreen. (And “vitamin D is one part to the story,” says Neale. “Actually, the best thing you can do to look after your bones is exercise. Weight-bearing exercise is equally, if not more, important than vitamin D”.)
What can you do to protect your body from the sun?
What frustrates cancer specialists is how low skin cancer rates could be – and how many people could avoid disfigurement. Rather than looking for cloudless skies and hot weather as prompts to put on a hat and other forms of sun protection, it’s UV levels that we need to be taking our cues from. “A combination of cloudy, overcast days and the temperature lulls people into a false sense of security,” says the Cancer Council’s Varlow. This is especially so during a La Nina season, where UV remains high even if it’s not clear and sunny. “So even on a rainy day, on a cloudy day, you still need to protect yourself from the sun.”
Apply sunscreen every morning when the UV level is three or higher. The UV scale runs from zero (Low) to 11+ (Extreme), and levels differ vastly from state to state, depending on the season. For instance, summer UV levels in Darwin will be around a daily maximum average of 12 and 13, whereas they will be from nine to 10 in Melbourne and between seven and eight in Hobart. To monitor UV levels where you are, check the Bureau of Meteorology’s website, or download the bureau’s SunSmart app.
The bureau not only reports the level, and what it means (for example, eight is very high), but specifies the time window when sun protection is particularly recommended. As a rule of thumb, avoid sun exposure from 10am to 3pm when UV levels are at their highest. Reapply sunscreen if you get wet, and otherwise every two or three hours, regardless of where you are, as cover for incidental sun exposure.
Buy sunglasses that meet strict Australian guidelines, as opposed to sunglasses could come from anywhere, says Whiteman. Sunglasses that comply with the Australian sunglass standard – labelled “sunglasses” or “special purpose sunglasses” rather than “fashion spectacles” – and with the Australian standard AS/NZS 1067 – provide eyes with “substantial protection” against the sun. They are recommended for both children and adults, particularly the wrap-around type that gives protection from the sides.
Consider using new sun-safety technologies such as UV sensors embedded in smart watches and smart phones, which indicate when the UV factor is high and when it’s time to reapply sunscreen. There are already some on the market. A plaster-like UV sticker, created by Gooding and his team at the University of New South Wales, changes from blue to colourless when a certain amount of UV light hits it. The UV light triggers food dye embedded in the paper and degrades it; when it is colourless, it is time to reapply sunscreen or seek shade.
“If you see something on your skin, get it looked at, please, as soon as you see it. Because if you get it early, you’ll be cured.”
Their initial idea, says Gooding, was to create something that parents could use on their children, after applying sunscreen on them, at the beach. “You have smart watches that have UV filters [which, for instance, alert you to when the UV factor where you are is over three] but you’re not going to put a smart watch on little Johnnie or little Susie,” he says. “[Parents need] a simple, cheap and easy thing to pop on their kids, so they know when to get them off the beach and into the shade.”
The caveat? These technologies won’t protect your skin by themselves. “It’s one thing to have a sensor and watch that works and gives the right information; then we have to understand, does that make people stay out [in the sun] longer [or] shorter?” says Whiteman.
Keep an eye on your skin, too – and let experts do so as well. Book in for regular skin checks and see your doctor if you notice any changes. These include the four main signs of skin cancer: crusty, non-healing sores; small bumps that are red, pale or pearly in colour; spots, freckles or moles that have changed in colour, thickness or shape; and the so-called ‘ugly duckling’ that looks unlike any other spot on your skin. (The above signs are, primarily, indications for melanoma. Non-melanoma skin cancers are usually pink and/or red, can be itchy, bleed and do not heal.)
“There’s no limit [where] you’re not at risk of getting melanoma,” says Scolyer. “If you see something on your skin, get it looked at, please, as soon as you see it. Because if you get it early, you’ll be cured. For skin cancer, surveillance is right in our face. It’s not, like, inside your body and we can’t see it. We have the opportunity to look in the mirror each day [and] use that benefit to pick them up early.”
Fascinating answers to perplexing questions delivered to your inbox every week. Sign up to get our new Explainer newsletter here.
Most Viewed in Lifestyle
Source: Read Full Article