Ozone pollution and skin cancer
Many sources offer good descriptions of skin cancer as one of the health effects the relationship between UV-B radiation and skin cancer in the chapter " Human Ozone Depletion and its Relationship to Skin Cancer" by doctors Amron and. The depletion of the ozone layer has health consequences for your skin and eyes , Between and , treatment of nonmelanoma skin cancers increased by There is a strong association between ultraviolet radiation exposure and. Rev Med Chil. Sep;(9) Epub Dec [The relationship between the ozone layer and skin cancer]. [Article in Spanish]. Sánchez C F(1).
Scientists still do not know how much impact UV light has on the human immune system. In animals this immune suppression is necessary for the development of cancers. With depletion of the ozone layer more of the UV wavelengths that suppress the immune system are going to be reaching Australians. So immune suppression from exposure to sunlight is likely to become even more dangerous than the initial production of skin cancer cells.
Vivienne Reeve, a researcher in Veterinary Pathology at the University of Sydney, studied the ability of sunscreens to protect against suppression of immunity caused by UV light.
She and other researchers at the University use a colony mutant hairless mice as models for the development of skin cancer in humans.
Ozone Depletion: Effects On Your Skin And Eyes - Sunsafe Rx
The mice are exposed to an artificial solar simulator with a spectrum similar to sunlight for 10 minutes, 5 days per week for ten weeks. The dose is not enough to cause sunburn but produces a slightly pink colour on the skin.
After 10 weeks the exposure ceases and the mice begin to get tumours. Ninety to one hundred per cent of the mice get skin cancer within 12 months. Reeve has examined two different types of sunscreens by painting them on to the mice before exposing them to the artificial light.
She found that whilst one, whose major active ingredient was an esther of cinnamate, was totally protective against immune suppression the other, whose major active ingredient was an esther of octile para amino benzoic acid PABAtotally failed to protect.
Both prevented sunburn equally well and she is currently investigating their comparative protectiveness from skin cancer. UV light can also initiate skin cancer at the same time that it is interfering with the immune response and this compounds the problem.
Reeve has found that although the major sunscreens on the market are very efficient in protecting the skin from sunburn and skin cancer outgrowth they do not seem to prevent the initiation of skin cancer. Potential cancer cells are still produced in the mice despite the presence of a sunscreen although the sunscreen seems to prevent the cancers from developing as fast as they would if the mouse was unprotected. Reeve does not believe the cinnamate based sunscreen is the ideal sunscreen despite its ability to protect against immune suppression and is awaiting better sunscreens from the industry.
One problem that the cinnamate sunscreen has had in the past was that 10 years ago the School of Public Health and Tropical Medicine at the University of Sydney discovered that some batches were contaminated with a mutagen and it now has to be batch tested to ensure the problem is not repeated. She believes there is a real need for watchdog organisations to monitor the products of the sunscreen industry, which after all is a multi-million dollar business.
He does not believe the government has adequately evaluated the safety of sunscreens. Apart from the possibility that the sunscreens could cause cancer themselves he argues that "we don't know anything about the effects of the chemicals absorbed on the nervous system, liver or other organs.
The relationship between skin cancers, solar radiation and ozone depletion.
Unfortunately it is the heavier, warmer fabrics that provide the best protection, not what fair-skinned Australians are happy to wear on a sizzling summer's day. The first step in this project has been to work out a way of characterising fabrics to indicate their protection factors like a sunscreen has a sun protection factor. Measurement of a fabric protection factor is relatively straightforward and in done in the same way that sunscreens are tested.
A person's skin is tested without any protection to see how long it takes for a particular dose of UV light to cause a slight pinkening of the skin. Then they are exposed to see how long it will take to cause that same pinkening through the fabric. If it takes ten times longer then that fabric is given a fabric protection factor of The trouble is that this method is time consuming and expensive and it would be better to establish a fabric protection factor without human testing, based on the geometry and transmission characteristics of the fabric.
However Walker and his team have found that there is no simple relationship between the characteristics of the fabric and the human testing results, although many researchers have assumed there is. Gavin Greenoak has been studying the role of natural tanning in protection from UV light.
Greenoak, who is remarkably tanned himself, argues that although the tan offers some protection against skin damage there is really no such thing as a safe tan. The researchers at Sydney University have bred a mouse that develops a tan when exposed to UV light. Greenoak believes this may be the first and only tanning mouse in the world. Reeve points out that they weren't aiming for a tanning mouse.
How much UV reaches the earth's surface depends on the amount of ozone overhead, clouds, small particles or aerosols, and pollution. As much as 80 percent of UVR can pass through thin clouds that appear to block the sun, so that you can sunburn even on an apparently cloudy day. Measuring long-term changes in UV penetration is quite difficult.
First, the amount of ozone overhead varies daily because of weather patterns, and to a lesser extent, due to ozone destruction by CFCs. Secondly, cloud systems change rapidly, and can cause the amount of surface UV to change by 10 to 50 percent occasionally more within minutes: While thick, uniform cloud layers allow little UV to arrive at the earth's surface, side reflections from tall, puffy clouds can actually enhance penetration of UV radiation by a few percent when compared with clear skies.
As much as 80 percent of UV Radiation can pass through thin clouds that appear to block the sun, so that you can sunburn even on an apparently cloudy day. Sincewe have been able to estimate this large variation in UV levels on the ground by using satellites that measure ozone and cloud amounts over the entire earth, and then calculating the UV penetration to the ground.
The calculations are validated by ground-based instruments. This has fallen off somewhat and is now only about four percent higher than in the s. The calculated percent change in UV irradiance caused by percent changes in ozone over the continental United States. The ozone change is estimated from satellite measurements over the United States.
Ozone and UV: Where Are We Now?
The Bright Side Overall, the news is good: The Montreal Protocol has had a dramatic impact in reducing ozone-depleting substances. The ozone layer is no longer declining, and there are signs of improvement. The Montreal Protocol has also helped to slow dangerous climatic changes such as global warming by reducing CFCs and other ozonedepleting substances, powerful greenhouse gases that prevent infrared radiation from escaping the atmosphere, reflecting it back towards earth and thus causing the earth to warm.
While the yet-to-be-signed Kyoto Agreement on greenhouse gases would have reduced carbon dioxide CO2 emissions by two billion tons bythe Montreal Protocol's reduction of ozone-depleting substances already reduced greenhouse gases emissions by the equivalent of more than 10 billion tons of CO2 at the end of When can we expect ozone levels to return to those seen in the s? With CFC production curtailed, scientists have estimated release rates of existing CFC stocks to project future levels.
These projections are fed into complex computer models of the chemistry, radiation, and dynamics of our atmosphere. The models project that ozone levels in the northern mid-latitudes will recover by aboutwhile polar levels the Antarctic ozone hole will recover by approximately A future epidemic of UV-related skin cancers may have been avoided.
Worst Case Scenario When can we expect ozone levels to return to those seen in the s? What might have happened if we had done nothing about CFCs? In the s, prior to discovery of the ozone problem, CFC production was increasing percent per year. Using the same computer models that predict the future recovery, we estimated that CFC emissions would have increased by three percent per year after Bythe levels of stratospheric chlorine would have been 16 times above levels.
Average global ozone levels would have decreased by two thirds. The UV index in the northern mid-latitudes would have increased to a value near 30 for midsummer noon conditions. The average mid-summer UV index value now is about 10 in these regions. Typically, it takes about 15 minutes for a fair-skinned person to develop perceptible sunburn in mid-summer. In this theoretical world "world avoided" it would have taken less than five minutes to develop a perceptible burn.
Research has shown that even small amounts of UV-B radiation can cause considerable harm. It is important to note, however, that UV-B radiation has always had this effect on humans. In recent years non-melanoma skin cancer has become more prevalent in many parts of the world because people are spending more time in the Sun and are exposing more of their skin in the process.
The relationship between the occurrence of milder non-melanoma skin cancers and time spent in the Sun is well documented. Such cancers generally occur in people in their 70s and 80s on areas of the skin usually exposed to sunlight such as the face or hands.
Malignant melanoma, however, usually occurs in younger people and in skin areas not necessarily exposed to sunlight. It tends to occur most commonly among groups of people less likely to have spent significant amounts of time outdoors.
The risk of developing malignant melanoma is directly related to the sensitivity of an individual's skin to the Sun i. The victims are almost exclusively Caucasians, particularly fair-skinned Caucasians.
The incidence of malignant melanoma has been increasing among light-skinned populations around the world for decades.