Ozone layer is a deep layer in earth’s atmosphere that contains ozone which is a naturally occurring molecule containing three oxygen atoms. These ozone molecules form a gaseous layer in the Earth’s upper atmosphere called stratosphere. The lower region of stratosphere containing relatively higher concentration of ozone is called Ozonosphere. The ozonosphere is found 15-35 km (9 to 22 miles) above the surface of the earth.
The ozone layer protects our planet i.e. Earth from the harmful radiation that comes from the sun. French physicists Charles Fabry and Henri Buisson first discovered the ozone layer in 1913. It has the capability to absorb about 97-99% of the harmful ultraviolet (UV) radiation that the sun emits, which can produce long term devastating effects on human beings as well as plants and animals.
An essential property of the ozone molecule is its ability to block solar radiation of wavelengths less than 290 nanometers from reaching Earth’s surface. In this process, it also absorbs ultraviolet radiations that are dangerous for most living beings. UV radiation could injure or kill life on Earth. Though the absorption of UV radiations warms the stratosphere but it is important for life to flourish on planet Earth. Research scientists have anticipated disruption of susceptible terrestrial and aquatic ecosystems due to depletion of ozone layer.
Ultraviolet radiation could destroy the organic matter. Plants and plankton cannot thrive, both acts as food for land and sea animals, respectively. For humans, excessive exposure to ultraviolet radiation leads to higher risks of cancer (especially skin cancer) and cataracts. It is calculated that every 1% decrease in ozone layer results in a 2-5% increase in the occurrence of skin cancer. Other ill-effects of the reduction of protective ozone layer include – increase in the incidence of cataracts, sunburns and suppression of the immune system.
Ozone layer depletion is simply the wearing out (reduction) of the amount of ozone in the stratosphere. Unlike pollution, which has many types and causes. Ozone depletion has been pinned down to natural cause and major human activity.
Natural causes of depletion of ozone layer:
Ozone layer has been found to be affected by certain natural phenomena such as Sun-spots and stratospheric winds. But this has been found to cause not more than 1-2% depletion of the ozone layer and the effects are also thought to be only temporary. It is also believed that the major volcanic eruptions (mainly El Chichon in 1983 and and Mt. Pinatubo in 1991) have also contributed towards ozone depletion.
Man-made causes of depletion of ozone layer:
The main cause for the depletion of ozone is determined as excessive release of chlorine and bromine from man-made compounds such as chlorofluorocarbons (CFCs). CFCs (chlorofluorocarbons), halons, CH3CCl3 (Methyl chloroform), CCl4 (Carbon tetrachloride), HCFCs (hydro-chlorofluorocarbons), hydrobromofluorocarbons and methyl bromide are found to have direct impact on the depletion of the ozone layer. These are categorized as ozone-depleting substances (ODS). Chlorofluorocarbons are released into the atmosphere due to:
- Cleaning Agents
- Coolants in refrigerators
- Packing material
- Air conditioning
- Aerosol spray cans etc.
The problem with the Ozone-Depleting Substances (ODS) is that they are not washed back in the form of rain on the earth and in-fact remain in the atmosphere for quite a long time. With so much stability, they are transported into the stratosphere. The emission of ODS account for roughly 90% of total depletion of ozone layer in stratosphere. These gases are carried to the stratosphere layer of atmosphere where ultraviolet radiations from the sun break them to release chlorine (from CFCs) and bromine (from methyl bromide and halons). The chlorine and bromine free radicals react with ozone molecule and destroy their molecular structure, thus depleting the ozone layer. One chlorine atom can break more than 1, 00,000 molecules of ozone. Bromine atom is believed to be 40 times more destructive than chlorine molecules.
The adverse effects of stratospheric ozone depletion on human health and welfare is a major environmental concern. One potential welfare effect is reduction in plant productivity, including agricultural crops, due to increased UV-B radiation and tropospheric ozone formation. This paper evaluates the economic effects of potential changes in crop yields due to hypothetical depletions in stratospheric ozone.
An unhealthy populace is an unproductive workforce. If the ozone becomes depleted, then more ultraviolet radiation could have serious impacts on human beings causing the following among others;
- Weakening of the human immune system (immunosuppression). Early findings suggest that too much UV radiation can suppress the human immune system which may play a role in the development of skin cancer.
- More skin cancers, sunburns and premature aging of the skin.
- Cataracts, blindness and other eye diseases; UV radiation can damage several parts of the eye including the lens, cornea, retina and conjunctiva.
2. Adverse Impacts on Agriculture, Forestry and Natural Ecosystem in Nigeria:
- Several of Nigeria’s major crop species are particularly vulnerable to increased UV radiation. Experiments on food crops have shown lower yields for several key crops such as rice, soy beans and sorghum. Also, plants minimize their exposure to UV radiation by limiting the surface area of foliage, which in turn causes stunted growth.
- This implies there would be a drop in the level of output of agricultural produces leading adversely to hunger and poverty.
- In particular, plankton (tiny organisms in the surface layer of oceans) are threatened by increased UV radiation. Plankton are the first vital step in aquatic food chains.
- Decreases in plankton could disrupt the fresh and saltwater food chains, and lead to a species shift.
- Loss of biodiversity in our oceans, rivers and lakes could reduce fish yields for commercial and sport fisheries.
- The destructive effects of ultraviolet-A radiation on the African Catfish, Clarias gariepinus was revealed in terms of the carbonyl protein (CP), lipid peroxidation (LPO), DNA damage, super oxide dismutase (SOD), catalase (CAT), glutathione peroxidase (Gpx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), lactate dehydrogenase (LDH), glutathione (GSH) and total antioxidant (TAO) in the gills, kidney, liver, muscles and skin. Also, glucose, total lipid, total protein and cortisol content of fish serums were detected.
- Wood, plastic, rubber, fabrics and many construction materials are degraded by UV radiation.
- The economic impact of replacing and/or protecting materials could be significant.
- Most of Nigeria’s structures collapse are usually as a result of unprofessionalism and use of sub-standard building materials, but now we stand a risk of having it happen naturally as a result of ozone layer depletion.
In conclusion, Nigeria needs to pay more attention to the issues of ozone layer depletion. There has been considerable progress in finding non-ozone-depleting substitutes for ODS in the last few years. Substitutes for air-conditioning and refrigeration applications are now available. Alternative products or processes can be used in some cases like: alternative insulating materials; substitute food containers such as hydrocarbon blown polystyrene, plastic film wrap and bags; alternative packaging materials such as plastic film bubble wraps; and air-conditioning and refrigeration plants operating on non-HCFC refrigerants.
Many household and personal aerosol products, e.g. paint sprays and insecticides, now use hydrocarbons (e.g. propane and butane) as propellants instead of HCFCs or CFCs.
The economic implication of ozone layer depletion in Nigeria is as real as day light.