What is the relationship between greenhouse effect and skin cancer?

Climate change can have a direct impact on human body through various channels, affecting people's spirit, immunity and disease resistance. Temperature change is closely related to mortality. In the United States and Germany, when the heat wave strikes, the overall mortality rate is on the rise. The adverse effects of global warming on human health are more serious in poor areas.

Global warming directly leads to superhigh temperature, heart disease and various respiratory diseases in some areas in summer, which takes many lives every year, among which newborns and the elderly are the most dangerous. Global warming leads to an increase in ozone concentration. Ozone in the lower air is a very dangerous pollutant, which can destroy human lung tissue and cause asthma or other lung diseases. Global warming will also lead to the spread of some infectious diseases.

After global warming, diseases in high-latitude countries will increase. According to statistics, in the absence of other environmental changes, the population mortality will increase when the temperature rises by 2℃ ~ 4℃. Global warming not only affects human health, but also affects some species on the earth. Some species may not adapt to this climate change, resulting in a decline in species diversity.

The increase of ultraviolet radiation on the ground will strengthen its long-term and short-term harmful consequences to human skin. Excessive exposure to solar radiation may lead to severe sunburn. Long-term exposure to radiation may lead to skin thickening, wrinkles and loss of elasticity, and increase the possibility of skin cancer. Sunburn and skin cancer are mainly caused by UV-B, and its wavelength is about 300 nm at most. Other adverse consequences are more related to ultraviolet-A. ..

White people have the greatest risk of skin cancer, among which light-colored people have the greatest risk, which can be understood according to the viewpoint of evolution. In ancient times, people with dark skin migrated from their original residence (assuming sunny East Africa) to high latitudes such as Europe and China, which reduced their exposure to the sun. In order to keep enough vitamin D produced by sunlight in the skin, natural selection may reduce skin pigmentation and allow more ultraviolet radiation to enter. The mechanism of this choice may have quite ruthless direct consequences: lack of vitamin D will cause rickets (bone softening and deformation); The abnormal pelvis of dark-skinned women living in high latitudes may directly reflect their impaired fertility. This is the main principle of natural selection. Light-skinned immigrants may finally gain an advantage in the gene pool (interestingly, South Asians, Africans and West Indies who immigrated to European countries now have evidence that this old problem has reappeared, and it is reported that some of those dark-skinned immigrants suffer from rickets). In the early immigrants to high latitudes, the lightening of skin color caused by natural selection may increase their risk of skin cancer in the long run. However, the increased risk of skin cancer in the next generation of adults has little to do with natural selection.

The increase of solar radiation is one of the main causes of skin cancer. Due to the hole in the ozone layer, the chances of human exposure to solar radiation increase, which makes people think that it will cause an increase in skin cancer. But to what extent? In recent years, scientists in many different fields have solved this problem. Traditional epidemiologists may prefer the individual counting method of waiting for observation; The answer that is useful to the society comes from the estimation made now, not from the real clinical observation that began to appear at the beginning of the next century.

First of all, if we know the relationship between the ozone reduction in the stratosphere and the corresponding change result of ground UV-B radiation (called radiation amplification factor). Secondly, if we know the dose-response multiple (biomagnification factor) between more chances of exposure to UV-B and more chances of skin cancer, it is possible to estimate that the risk of skin cancer will increase with the reduction of ozone in the future. The first relationship is to obtain clear results through direct environmental measurement, including clarifying the confusion caused by tropospheric pollutants. The second relationship can be estimated by several methods, especially by estimating the regional differences in the incidence of skin cancer caused by different exposure of light-colored people to ultraviolet radiation. But it should be noted here that how much of the difference in the incidence of skin cancer related to latitude is caused by the difference in the surrounding radiation level? How much is caused by the differences in people's behavior patterns such as occupation, entertainment and clothing? Because of these complex behavioral changes that reflect the local average solar radiation (a "complex" variable recognized by epidemiologists, which makes it difficult to conduct non-experimental research among free people), the data obtained from people who are addicted to eating, drinking and having fun may not accurately reflect the true intensity of the dose-response relationship. For example, Queensland people in low latitudes wear wide-brimmed hats, while people in high latitudes don't, so simply comparing their incidence of skin cancer will underestimate the true latitude-related risk of skin cancer in Australia.

199 1 year, the United Nations Environment Programme estimates that every time ozone disappears 1%, the dose of carcinogenic UV-B will increase 1.4%, and the incidence of basal cell carcinoma and squamous cell carcinoma will increase by 2.0% and 3.5% respectively. The United Nations Environment Programme estimates that for every 1% ozone consumption, non-melanoma skin cancer will increase by 2.3%. According to the IPCC's estimate of global warming, there is an uncertain area in these estimates of radiation and biomagnification factors, which is about 1/4. The biomagnification coefficient of melanoma is even more uncertain, ranging from 0.5% to 10%. The United Nations Environment Programme predicts that if ozone is reduced by an average of 65,438+00% (as it happens in high latitudes) and lasts for 30 to 40 years in the world, it will lead to at least 300,000 cases of non-melanoma skin cancer and 4,560 cases of malignant melanoma in the world every year, which may be twice this figure.

Increasing exposure to UV-B has an impact on the incidence of skin cancer, which is equivalent to moving people to low latitudes. Take Tasmania, Australia (about 40 south latitude) as an example. According to the current development trend, in another 40 years, such as 1980~2020, the annual ozone layer consumption will increase by 15%, and the non-melanoma skin cancer will increase by about1310. For people in Tasmania, this is equivalent to living halfway up the east coast of Australia, about 30 south latitude. In the long run, due to the continuous consumption of stratospheric oxygen, the incidence of skin cancer will increase by 50% ~ 100% for people with light skin color living in high latitudes in two hemispheres.

At present, all these estimates are unclear due to technical and statistical uncertainties. These uncertainties are caused by unpredictable adaptive changes in people's behavior (for example, ozone disappearance reports have become a routine part of our daily weather reports) and local fluctuations in tropospheric air pollution. Monitoring the real incidence of skin cancer among sensitive people in the world will not provide obvious evidence of risk changes for at least several decades. In view of this lag, the International Agency for Cancer (an agency of the World Health Organization) is studying and developing a new method, establishing a crowd monitoring system and providing early warning. The system can include the detection of early cancer-related skin cell damage, including the occurrence of special genetic variation, in selected populations living in different geographical locations and therefore having different UV-B radiation exposures.