Effects on human health
The ozone depletion has significant effects on human health in terms of skin cancers, cataracts and immune system.
The evidence for UV becoming a vital factor in skin cancers are as follows. First of all, there is an increase in UV-B intensity with the decrease in latitude. Furthermore, skin cancers happen most likely in those areas with high UV exposures. And it happens more often on people who have frequent outdoor operations. Moreover, it’s higher for men than women. With an increase in age, the probability gets higher also.
Throughout the world, there are mainly two types of skin cancers, which are melanoma and non-melanoma. Melanoma is typically a severe form of skin cancer and it’s increasing at an enormous rate. Non-melanoma is the most common form of cancers. However, there is no sufficient evidence to prove the inside relationship between melanoma skin cancer and increasing UV exposures. (IARC,1994) Based on a study conducted in Norway in four different latitudes (Henrikson, et al., 1988, 1990) , the biological amplification factor for non-melanoma skin cancer was shown to be around 2.0.
Apart from higher chances of skin cancer, high intensity of UV light results in causing cataracts, which is a major factor of blindness in the world with over half of the blindness incidences are caused by cataracts (UNEP, 1994). Unlike the mechanism of skin cancer, cataracts are mainly caused by UV-A. Nevertheless, a study (Taylor & McCarty, 1996) suggests that UV-B also causes cataracts.
When the sunlight strike on the normal eye, the light hits cornea first followed by lens, vitreous humor and lastly retina. A various studies show that a large amount of UVR never reach retina, they are absorbed by lens and cornea. The cornea absorb the light with the wavelength below 300nm (mostly UV-B), and the lens absorb the radiation with the wavelength below 370nm (mostly UV-A). That’s also why the artificial replacement lenses involve UV absorption segments.
Excessive exposure of UVR may affect the functionality of immune system. As far as a human body concerns, the skin is the first barrier which protect us from the outside virus and bacteria that may carry infect agents. In order to protect our body, the immune system needs to identify the cells that do not function optimally and clear them if necessary. However, after extensive contact with UVR, the skin cells may be degenerated and lose its functionality. As a result, the skin is no longer able to defense and immune system is partially damaged.
Effects on agriculture
In this day and age, there are arguably parallel possibilities for UVR to be experimented in the enhancement of crop production, nevertheless controversy debates have been carried out focusing on the results for plant productivity due to the threat of increased UV-B levels. Ozone depletion which radiates more UV-B will require the use of UV-B tolerant cultivars and the development of new types of crop. Much evidence suggests that there will be a side effect on crops, but these effects are relatively hard to estimated quantitatively (UNEP, 1994; Tevini, 1993).
Effect on Ecosystem
Terrestrial ecosystems: the largest store of active organic carbon in the biosphere, including biomes of widely variable climate regimes with a diverse set of organisms adapted to this range of conditions.
Anthropogenic activity can directly and indirectly affect terrestrial ecosystem. Superimposed on temperature, atmospheric CO2, and altered precipitation patterns are changes in the levels of solar UV-B radiation, which can cause stratospheric ozone depletion and other atmospheric factors. Since 1979, a significant increase in UV-B radiation reaching the Earth’s surface has been calculated through incorporate satellite measurements of ozone, cloud and aerosol reflectivity. All latitudes except the equatorial zone have shown this increase and the largest increments takes place at mid to high latitudes in the Southern Hemisphere.
Relations of human activities with the environmental problems such as ozone depletion and climate change. The most severe damage of ozone layer happens in southern hemisphere.
The enhanced UV-B radiation results in ~3-4% negative effect on plant growth. Also, a comprehensive meta-analysis of UV-B supplementation studies showed that the average response to treatments that simulated 10 to 20% depletion of ozone was a 6% reduction in plant biomass. Another more recent meta-analysis suggested that woody perennials are more sensitive to UV-B radiation than herbaceous plants in average.
Relations between UV-B radiation amount change with the growth condition of plants.
Although terrestrial ecosystems at high latitudes are not highly productive for grazing, timber production, etc., the influence of ozone reduction on these systems may be important. The Swedish subarctic and southern Argentinean systems, for example, are not only suffering ozone depletion, but also under greatest global warming because carbon sequestration is generally quite high in these ecosystems, including the extensive peat formations. Thus, they are exposed to several features of climate change. In the Northern Hemisphere, these high latitude ecosystems are also very important for the survival of indigenous ethnic groups.
Data has shown that ozone depletion may trigger/contribute to other environmental problem such as climate change. So ozone depletion will affect terrestrial ecosystem regardless location or latitude.
Although there are many uncertainties, increased UV-B radiation has a very real potential for significant impacts on aquatic ecosystems, especially on phytoplankton and larvae of higher organisms.
Marine phytoplankton is fundamental in the food chain and the oceanic carbon cycle, for it can convert atmospheric carbon dioxide into oxygen through photosynthesis. The phytoplankton organisms are the bases of the marine food chain. They are concentrated in high latitudes where stratospheric ozone depletion is predicted to cause the greatest increase in the amount of UV-B radiation reaching the Earth’s surface. Circumpolar region contain densities of phytoplankton approximately 10 to 100 times larger than equatorial regions (UNEP, 1994). Upwelling areas along the continental shelves are other concentrating areas for phytoplankton. Investigations in Antarctica indicate that phytoplankton productivity has already been affected by current UV-B radiation levels (UNEP, 1994; Tevini, 1993).
Food chain supply and energy flow mechanism for aquatic ecosystem. UV-B radiation will start to speed up the growth of plankton(question: here is different from my research). impact on plankton growth will have influence in the aquatic ecosystem in the long run.
Early developmental stages of fish, shrimp, crab, amphibians, and other animals are also limited by current UV-B radiation levels (UNEP, 1994). As for zooplankton, they could be significantly impacted by the UV-B radiation caused by a 16% ozone reduction. The predicted increase in daily UV-B irradiance within the upper 1 to 2m would exceed the daily dose found to cause a significant reduction on survival of most zooplankton species.
UV-B radiation also have negative impact on marine animals.
Effect on biogeochemical cycles and materials
The implication of ozone depletion on terrestrial and marine ecosystem is just a glance of how ozone depletion is actually influence the biogeochemical cycles. With the change from ecosystem and UV-radiation, the global climate would thus change as a response. Right now we are not sure how much and the direction it will change the climates, but one thing is sure. It has been suggested that the imbalance of the biogeochemical cycle would enhance the greenhouse effects.
When we shift our attention out of the ecosystem, we discover that the ozone depletion is in fact affect all aspect of the earth. It may starts from the daily materials we used. The excessive UV-B radiation from ozone depletion have effects on everything such as the physical and chemical properties of materials, such as weaken the elastic properties and shorten the operation life of plastic and rubber.
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