30 years of the Montreal Protocol – what it means for skin cancer
Many believe the ozone hole is a factor in our excessively high skin cancer rates in Australia. Stratospheric ozone does reduce the amount of ultraviolet radiation (UV) reaching the Earth’s surface.
In reality though the hole is confined to the South Polar Region and ozone depletion has made no appreciable difference to skin cancer rates in Australia and New Zealand.
The depletion of the ozone layer caused legitimate concern and prompted the establishment of the Montreal Protocol in 1987 designed to eliminate ozone-damaging pollutants and repair the ozone hole. The Montreal Protocol is often dubbed the world’s most successful environmental agreement and is slowly but surely reversing the damage caused to the ozone layer. As ozone-destroying gases are phased out, the annual ozone hole is generally getting smaller. It will take many decades to be fully repaired however.
The calculated clear-sky UV index expected for November 2065 with the Montreal Protocol, compared with what would have been the UV index with no Montreal Protocol.
Without the Montreal Protocol, UV levels would have been expected to have tripled by 2065. One study estimates that 2 million fewer skin cancers per year will be diagnosed by 2030 thanks to the protocol.
Why is skin cancer so common in Australia?
Australia has the second highest rates of skin cancer in world, having recently been overtaken by New Zealand. Skin cancer is Australia’s most common cancer, with data showing that every year, GPs have over 1 million patient consultations for skin cancer, and skin cancers account for around 80% of all newly diagnosed cancers.
Skin cancer is primarily caused by excessive exposure to UV radiation from the sun, causing DNA damage to skin cells. People with pale skin types are more vulnerable to skin cancer and, broadly, the more sun they are exposed to – and the greater the intensity of the UV radiation – the higher their risk.
Most Australians (and Kiwis) have the wrong type of skin for their environment. Basically, through migration, our two countries have been populated by many people with fair skin whose ancestors come from much less sunny climates. Lack of protective pigmentation leaves skin cells especially vulnerable to the DNA-damaging rays from the sun.
As well as skin type, a major factor is our proximity to the equator. Generally speaking, the closer to the equator someone lives, the greater the amount and intensity of sun exposure they receive. That gradient is seen in a comparison of skin cancer rates across Australian states with Queensland reporting much higher rates than New South Wales, which is in turn higher than Victoria.
Add to that the lower pollution levels and clearer air in the southern hemisphere – due largely to much lower population densities – resulting in UV levels about 7% higher than in the northern hemisphere.
The main cause of skin cancer is sunburn and tanning, in other words, exposure to UV radiation, made worse in Australia by our location and skin types. The solution? Check the UV Index in the weather section of daily newspapers, at www.myuv.com.au or by using the free SunSmart app. When it’s 3 or above, use sun protection.
Thanks to our friends Terry Slevin and David Whiteman for their Conversation article. Read it here