The Environment Problem Of Ozone Depletion

We have always seen cricketers paint their faces white and mothers insisting their kids to apply sun screen to protect themselves from UV or Ultraviolet rays. Ultraviolet rays are harmful sun rays that increase the risk of skin cancer, cataract and harm the immune system. They can also cause damage to plant life, single cell organisms and equated ecosystems. Earth is protected from these UV rays by a layer in the stratosphere called ozone layer. However, since the 1970s ozone has been depleting and this refers to two related events: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone around Earth's Polar Regions (ozone hole).

Ozone is a gas made up of three oxygen atoms which is about three to five millimeters thick and this thinly spread out gas has been protecting life on Earth’s surface from UV rays for billions of years. The ozone layer takes in about 97-99% of the sun's harmful ultraviolet light rays. Since the measure for ozone layer thickness is measured in Dobson unit, it helps in identifying what the physical thickness of ozone would be if compressed in the Earth's atmosphere. It is the primary measure used in ozone related researches and one Dobson Unit (DU) is defined to be 0. 01 mm thickness at STP (standard temperature and pressure). Our ozone sheet is being deteriorated due to certain man-made chemicals.

Ozone can be torn down by a number of free radical catalysts; the most significant are the hydroxyl radical (OH•), nitric oxide radical (NO•), chlorine radical (Cl•) and bromine radical (Br•). The dot is a notation to represent that each species has an unpaired electron and is therefore extremely reactive. These elements are formed through natural and man-made sources but if we look at the current scenario, majority of the OH• and NO• in the stratosphere is naturally occurring, but human activity has intensified the levels of chlorine and bromine. These elements are generally found in stable organic compounds, the most common being chlorofluorocarbons, which can travel to the stratosphere without being broken down in in the troposphere due to their low reactivity. With the assistance of a catalyst, oxygen can easily reduce to the more stable oxygen form. Chlorine and Bromine atoms destroy ozone molecules through a variety of catalytic cycles.

One of the simplest example of such a cycle could be that of a chlorine atom’s reaction with an ozone molecule (O3), taking an oxygen atom to form chlorine monoxide (ClO) and leaving an oxygen molecule (O2). Ozone layer depletion increase surface UVB levels( all else equal) which could affect human health, especially through increase in skin cancer as ozone layer absorbs UVB ultraviolet light from the sun. According to HIPERION, a study published by Ecuadorian Space Agency in 2008, retrieved data from 12 satellites of several countries over 28 years showed that UV radiation reaching equatorial latitudes was higher than expected, with the UV Index increasing up to 24 in Quito (the WHO considers 11 as an extreme index and a great risk to health) The conclusion of the report stated that the depleted ozone levels around the mid-latitudes of Earth are already endangering large populations in these area. The effects of increased surface UV radiation on human health has been the major public concern regarding the ozone hole. So far, ozone depletion in most locations has been typically a few percent and, no direct evidence of health damage is available in most latitudes. If the increased levels of depletion identified in the ozone hole were to be common across Earth, the subsequent effect could be considerable more dramatic. UVB exposure have drastic effect on human health as the most common forms of skin cancer, basal and squamous cell carcinomas has been firmly linked to UVB.

The mechanism by which UVB induces these cancers is well understood — absorption of UVB radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcription errors when the DNA replicates. Though these cancers are comparatively mild and rarely fatal, extensive reconstructive surgery is required for the treatment of squamous cell carcinoma. Another form of skin cancer, malignant melanoma, is rare but far more threatening, being lethal in about 15–20 percent of the cases diagnosed. The association of malignant melanoma to ultraviolet exposure is not fully studied, but it appears that both UVB and UVA are involved. It is difficult to estimate the effect of ozone depletion on melanoma incidence because of this uncertainty. Epidemiological studies also found that ocular cortical cataracts can be associated with UVB exposure, using crude approximations of exposure and various cataract assessment techniques. On the report of Br J Ophthalmol (1994), he stated that increase in average annual ocular exposure were associated with the increasing risk of cortical opacity. When it comes to other health risks associated with increased surface UV on humans, increased tropospheric ozone is an important concern as it leads to presence of Ground-level ozone. The action of UV radiation on combustion gases from vehicle exhausts causes the formation of ozone at ground level. Ground level ozone is produced mainly Ground-level ozone is generally recognized to be a health risk as ozone is hazardous due to its strong oxidant properties.

The risks are especially high for young children, the elderly, and those with asthma or other respiratory difficulties. As ultraviolet light helps in the production of Vitamin D in the skin, higher UVB exposure raises human vitamin D in those deficient in it. Blood calcium increases excessively when the blood level of Vitamin D is in excess of 100 ng/ml which is associated with higher mortality although the excess production of Vitamin D by the sunlight is prevented by certain mechanisms in our body. It is also vital to focus on the effects of UV rays on animal life, particularly on marine life. Phytoplankton are the most vulnerable to high levels of UV rays as they can be potentially be killed in large numbers solely from ozone depletion to the point that it will cause a domino effect. Their absence can lead to a skewed food chain and create strong competition among other marine life. Though the damage caused by extreme UV rays on plant life cannot be visually identified, its effect is paramount. Its growth, physiological and developmental processes are all affected negatively which can subsequently have important implications for plant competitive balance, animals feeding on them, plant diseases, and biogeochemical cycles. For instance, a wide range of economically important species of plants such as rice depend on cyanobacteria inhabiting on their roots for the retention of nitrogen.

Increase in UV radiation affects the presence of cyanobacteria as they are is highly sensitive to UV radiation. To prevent these hazardous effects and the ozone hole from spreading further, an international treaty known as the Montreal Protocol was designed by phasing out the mass production of numerous substances that are responsible for ozone depletion. This international agreement that was signed on 16th September 1987, has helped the ozone hole in Antarctica slowly but significantly. According to the recent climate projections (2011), the ozone layer will revive to 1980 levels between 2050 and 2070. The treaty is blanketed around several groups of halogenated hydrocarbons that deplete stratospheric ozone. All of these destructive substances that are now controlled by the Montreal Protocol contain either chlorine or bromine (substances containing only fluorine do not harm the ozone layer) but some substances like nitrous oxide (N2O) are yet to be controlled by the Montreal Protocol. According to Elizabeth R. DeSombre (2000), the treaty is highly successful due to solution proposals mitigating regional conflicts of interests and effective burden sharing making it the single most effective international agreement till date. Since its implementation, the atmospheric concentrations of chlorofluorocarbons and related chlorinated hydrocarbons have either been decreased or leveled off. A clear positive signal from the Montreal Protocol to the stratospheric ozone has been evident from the statistical analysis from 2010.

The Montreal Protocol is also expected to dissolve the health issues related to ozone depletion. A report by U. S Environmental Protection Agency (2015) estimated that the revival of the ozone layer under the treaty will avert 280 million cases of different types of skin cancer and 45 million cataracts in the United States of America. Montreal Protocol’s success which is expected to recover the ozone layer by 2050 is challenged by two major points that distracts it from achieving its objectives. First being that many of the developing countries have not yet phased out ozone depleting substances like R-22, a hydrochlorofluorocarbon (HCFC) found in many refrigeration and air conditioning systems. There have also been various reported cases of these substances being smuggled to other countries which answers to the conclusion of the 2001 NASA report wherein the ozone thinning over Antartica had remained the same thickness for the previous three years, however it grew to its second largest size in 2003 and a relative increase in CFC due to an unknown source. These developing countries will require financial support in the form of multilateral funds which is provided under the Montreal Protocol to eliminate the usage of the ozone depleting substances. This funding is crucial for these poor countries to not only help them eliminate the usage of these harmful substances but also leap forward to much cheaper replacement- hydroflurocarbons (HFCs). The US usually provides about 20 per cent of the funds but the government under Trump has turned a deaf ear to this so far. Second being the ignorance of the harmful effects of the cheaper alternate halogen: hydroflurocarbons (HFCs). While HFC’s are safe for the ozone, they pose great danger to the environment as they are a powerful greenhouse gas, thousand times worse than carbon dioxide (CO2). Developing countries like China and India are manufacturing air conditioners and refrigerators using HFC’s at a faster pace. Thus, the resultant climate change has produced persistent heat waves and higher summer temperature. The Kigali Amendment to the Montreal protocol has been made to phase out the use of HFC in manufacture of cooling equipment and it is said to have major impact on global warming and climate change. Under this amendment, over 197 countries have committed to cut down the usage of hydroflurocarbons by more than 80 per cent over the next 30 years. This development is likely to cut down to cut down global warming up to 3. 6 degrees F (2 degrees Celsius). The limiting of global warming will cut out Africa’s agricultural yields by 40 per cent which will result in a risk of under nourishment to more than half of the African nourishment. In these times of war, diplomacy, refugee crisis and regional conflicts, global environmental crisis might seem like a problem of lower magnitude. In this vast effort of saving our plant and whatever is left of it, hurdles seem to be continuous and challenge the future of mankind existence all together.

References

1. DeSombre, Elizabeth R. (2000). The Experience of the Montreal Protocol: Particularly Remarkable, and Remarkably Particular(PDF). UCLA Journal of Environmental Law and Policy, 19(1), 69-75. Retrieved from https://escholarship. org
2. Fahey, David. Hegglin, Michaela (2010) Twenty Questions and Answers about the Ozone Layer (PDF). Geneva, Switzerland: World Meteorological Organization. Retrieved from www. wmo. int
3. Purohit, Pallav. Höglund-Isaksson,Lena. Wagner,Fabian. (2018). Impacts of the Kigali Amendment to phasedown hydrofluorocarbons (HFCs) in Asia (PDF). Laxenburg, Austria: International Institute for Applied Systems Analysis. Retrieved from http://pure. iiasa. ac. at