"Ozone Depletion, Skin Cancer and Australia" Lesson 3 "Ozone Depletion, Skin Cancer and Australia" This lesson is intended to what role ozone depletion has in relation to Australia, and Australia’s high rate of skin cancer. Note: One of the misconceptions many Australian have is that ozone depletion is responsible for Australia’s high rate of skin cancer. This will be discussed in this lesson. Ozone module prepared by Eugene C. Cordero

Outline How does ozone depletion affect Australia? Why does Australia have the highest rate of skin cancer globally? Skin cancer risk factors Ozone module prepared by Eugene C. Cordero

What are the consequences of an ozone depleted world? With ozone depletion, there will be higher rates of UV radiation. More UV radiation rates mean Higher rates of skin cancer Higher amounts of cataracts Possible danger to plant and animal life Recall: Without the ozone layer, life on the Earth’s surface would not exist!!! When the international community first realized that there was potential for large scale ozone depletion the consequences spurred rapid action. A lowering of global ozone levels by 10% could have a catastrophic impact on biological life on earth. Not only would human cases of skin cancer soar, but animal and plant life would be severely impacted. Ozone module prepared by Eugene C. Cordero

How does ozone depletion affect Australia? Global ozone trends? Ozone Hole? Over Southern Australia, ozone levels are declining at about 3% per decade, while over Northern parts of Australia, there is little or no trend. The ozone hole doesn’t seem to have much influence on the Australian continent, although it’s relatively proximity seems to explain at least some of the public misunderstanding that the ozone hole is over Australia. Ozone module prepared by Eugene C. Cordero

Global Ozone Trends Ozone trends from a NASA satellite shown in percent change per decade. The horizontal scale is time, in months from January through December, while the vertical scale is latitude from the South Pole to the North Pole. The colors denote larger negative ozone trends, while the white shading indicates no ozone trend. For example, over Southern Australia main population centers (25-35S), trend is at most 2-4% per decade, although less during some seasons. In Northern Australia such as Cairns (17S), there is no observable ozone trend, in a statistical sense. Most of Australia does not have large negative ozone trends Ozone module prepared by Eugene C. Cordero

How does ozone depletion affect Australia? Is the ozone hole over Australia? No, not even close! Over Southern Australia, ozone levels are declining at about 3% per decade, while over Northern parts of Australia, there is little or no trend. The ozone hole doesn’t seem to have much influence on the Australian continent, although it’s relatively proximity seems to explain at least some of the public misunderstanding that the ozone hole is over Australia. Ozone module prepared by Eugene C. Cordero

… then why does Australia have the highest rate of skin cancer? Naturally high levels of UV radiation in Australia Australia has a light skin-type population Lifestyle choices (suntan, outdoor hobbies etc.) So if Australia isn’t influenced much by ozone depletion, why do we have such problems with skin cancer? That is a good question! The simple answer lies in the fact that Native Australians don’t have much problems with skin cancer, they’ve lived here for many thousands of years and have adapted to the normally harsh sunlight of Australia. However, the immigrants of Australia are largely from Europe, where UV levels are naturally much weaker. Other factors that influence skin cancer besides skin type and UV levels have to do with social attitudes. If a tan looks good, if going to the beach is cool, and if people like to enjoy time outside, these are all factors that can change ones risk to skin cancer (recall that in the 50’s, hats, dresses and long sleeves were the fashion rather than shorts and a t-shirt of the 80’s. Hopefully, social attitudes are now changing. At least government has recognized the value of a sun-smart social awareness, and school children and parents are much better educated now then 20 years ago. Ozone module prepared by Eugene C. Cordero

Skin Cancer Risk Factors High Risk Low Risk Skin type: Light skin Dark skin Environment: Tropics High Latitudes Occupation: Outdoor Indoor Social factors (i.e. hobbies etc.) This figure lists some of the risk factors involved with skin cancer. The primary two are skin type and environment. Light skined people are always at a higher risk than people with naturally darker skin. Take Australia’s indigenous population, for example, who have a low risk of skin cancer. They have lived in Australia for thousands of years, and thus have had a lot of time to adapt. Environment is also very important. Light skined populations are historically from the higher latitudes, where natural UV levels are relatively low. Australia is in a high sunlight environment, similar to Africa. Occupation and other social factors are also important. Naturally, a fisherman who works outside all day will likely have a higher risk of skin cancer than an indoor worker. Social attitudes are also important, like whether a tan looks good, and thus is desirable. Ozone module prepared by Eugene C. Cordero

Australia is in a high sunlight environment!!! This world map simply illustrates where Australia would be (in terms of the same latitude but in the N. Hemisphere) if Australia was in the Northern Hemisphere. This example illustrates how Australia has the same latitudes as central Africa, with Europe to the North. So, in essence, Australia really is a subtropical continent, much different from it’s ancestors of Europe. If Europeans migrated south to central Africa, would it be a surprise if they had troubles adapting to the strong sunlight? Ozone module prepared by Eugene C. Cordero

Skin Cancer and Ozone Depletion Most skin cancer is attributed to exposure 20 or more years ago (before ozone depletion). The younger generation of today will face higher risks in the future due to current decreases in ozone levels and increases in UV (~5-10%). When answering the question: Is ozone depletion the major cause of Australia’s high rate of skin cancer, the answer is simply, no. Although ozone levels are lower over much of Australia today compared to 20 years ago, these changes cannot explain why Australia has such a problem with skin cancer. Here is some reasons for that. Most skin cancer diagnosed today is attributed to sun exposure 20 or more years ago. Childhood sunburn and prolonged exposure to the sun increase the risk of skin cancer later in life. Ozone depletion, however, has only been around for say, 15 years, and in relatively small amounts. Personal exposure to UV radiation is dependent on a number of variables. One of these is what type of lifestyle a person has, I.e their employment and hobbies etc. For example, a professional push-bike rider will naturally have much more exposure to UV radiation than an office worker. A light skinned person has a much higher risk of cancer than an dark skinned person. In Australia, the majority of the population has roots in Northern Europe, where UV levels are fairly lower. That is why this population is naturally fair skinned. In contrast, the indigenous population of Australia have very dark skin. They have had many thousands of years to adapt to the high UV environment, and thus their skin pigments are dark. Thus, Aborigines have low rates of skin cancer. Is it a surprise that light-skinned Australians are at risk? An important point is this: Although today’s skin cancer problems are not due solely to ozone depletion, the real reductions of ozone in the atmosphere have not helped the situation. This is especially true for today’s youth, who face much larger skin cancer threats than we did as children. The upside to this situation is that today’s youth is educated about of the potential harm of the sun, and hopefully more sunsmart. Ozone module prepared by Eugene C. Cordero

Ozone depletion and global warming No direct connection between these environmental issues. However: Global warming may enhance ozone depletion global warming produces Tropospheric warming & stratospheric cooling Therefore, if the stratosphere cools, then ozone destroying chemistry (e.g. ozone hole), will increase. Extra topic: (advanced) There exists lots of confusion between ozone depletion and global warming, not just with students, but with the general public. Many people confuse the cause and effect, saying that automobile pollution cause ozone depletion, or that holes in the ozone layer allow more radiation to enter, thus causing global warming. These are not true. One may think of ozone depletion and global warming as two separate environmental issues, with almost no overlap. Ozone depletion comes from CFC’s, or air conditioner refrigerants, fire retardants, aerosols etc. Global warming comes from increases in CO2, due to coal power plants, automobile exhaust etc. The only relationship between the two issues is: If global warming continues, as expected, then the earth’s surface will continue to get warmer. A consequences of a warmer surface is a cooler upper atmosphere. Recall, from our ozone hole recipe, that cold temperatures are one of the prerequisites for an ozone hole. Thus, if the upper atmosphere does cool off, this could enhance ozone depletion. What this means is that even though we are cleaning up the atmosphere of chlorine, the recovery of the ozone layer will take longer if the upper atmosphere gets cooler. It seems that we are now seeing evidence of a cooler upper atmosphere. Measurements of stratospheric temperatures show that the stratosphere has cooled 1-2K in the last two decades. The consequences of this may be occurring over the Arctic, where cooler temperatures have caused the appearance of so-called mini ozone holes, small areas of ozone depleted air similar to the Antarctic ozone hole, but of a much smaller size. More general note: Although international steps have been taken to address the possible depletion of the ozone layer, addressing the concerns of global warming is much more difficult. In the ozone depletion story, the science behind the ozone hole was good, and large companies like Du Pont, who saw a future in producing alternate ‘ozone friendly’ chemicals, agreed with the science that CFC’s could potentially destroy large amounts of ozone. However, in the case of global warming, the science is much more complicated, and the economic interests are much larger, and could mean the end of an era of energy producing companies. Thus, the story of ozone depletion, although far from over, seems headed for some time of happy ending, while global warming is just heating up, pardon the pun. It therefore seems particular important that we pass on the ozone depletion story to today’s students, so they can refer to this experience when making the difficult decisions that will be needed to deal with global warming. Ozone module prepared by Eugene C. Cordero

Summary A sun smart lifestyle! Many factors influence skin cancer such as A sun smart lifestyle! Ozone module prepared by Eugene C. Cordero