Ozone Depletion, a Big Threat to Climate Change: What can be Done?-Juniper publishers
JUNIPER PUBLISHERS-OPEN ACCESS GLOBAL JOURNAL OF PHARMACY & PHARMACEUTICAL SCIENCES
Ozone in the stratosphere is very important as it
acts as a safeguard for the earth and protects life from harmful
ultraviolet radiations coming from the sun. Depletion of stratospheric
ozone, resulting from atmospheric pollution has led to increased
ultraviolet radiation at the earth’s surface as well as spectral shifts
to the more biologically damaging shorter wavelengths. A decrease in the
concentration of stratospheric ozone enhances the solar ultraviolet
(UV) radiation, which is harmful to the growth of the plant and various
other metabolic processes of the organisms and might cause changes in
pigment concentrations, nucleic acids, and proteins. Multiple causes of
ozone depletion have been identified in the literature review, but the
findings are not synthesized at one place. Thus, the purpose of this
paper was to review the causes of ozone depletion and to propose the
interventions to address this problem in order to avoid the climate
change and its associated outcomes.
Keywords: Ozone depletion; Climate change; InterventionsIntroduction
Ozone in the stratosphere is very important as it
acts as a safeguard for the earth and protects life from harmful
ultraviolet radiations coming from the sun [1]. About 90% of ozone is
located in the stratosphere (8-18 km) and only 10% in the troposphere
(below 8 km) [1]. Stratospheric ozone depletion has been recorded from
the temperate to Polar Regions [2]. Ozone in the troposphere is a
greenhouse gas, trapping the long wave radiation in 9.6 nm bands
affecting the energy budget of the earth-atmosphere system [3].
Atmospheric ozone has two types of effects on the temperature balance of
the earth, it absorbs solar ultraviolet radiations, which heats the
stratosphere and it also absorbs infrared radiation emitted by the
earth’s surface effectively trapping heat in the troposphere [4].
Therefore, the climate impact of changes in ozone concentration is
important and varies with altitude (Troposphere to Stratosphere) at
which these ozone changes occur [4]. Depletion of stratospheric ozone,
resulting from atmospheric pollution has led to increased ultraviolet
radiation at the earth’s surface as well as spectral shifts to the more
biologically damaging shorter wavelengths [5,6].
A decrease in the concentration of stratospheric
ozone enhances the solar ultraviolet (UV) radiation, which is harmful to
the growth of the plant and various other metabolic processes of the
organisms and might cause changes in pigments concentrations, nucleic
acids and proteins [7,8]. Moreover, exposure to elevated concentrations
of ozone is associated with increased hospital admissions for pneumonia,
chronic obstructive pulmonary disease, asthma, allergic rhinitis, and
other respiratory diseases, and with premature mortality [9,10].
Multiple causes of ozone depletion have been identified in the
literature review, but the findings are not synthesized at one place.
Thus, the purpose of this paper was to review the causes of ozone
depletion and to propose the interventions to address this problem in
order to avoid the climate change and its associated outcomes.
Methodology
Studies on this topic of ozone depletion were
identified through the search engines including Pub med, science direct,
Springer link, Cochrane library, and Google scholar Furthermore, World
Health Organization (WHO) website was also used for getting some
information regarding the topic. The keywords
which were used are: “ozone layer depletion”, “ozone depletion
and Pakistan”, “global data about ozone depletion”, “ozone
depletion in developing countries”.Around twenty articles were
reviewed completely, including reports.
Findings of review
It is known that air pollution is and will be directly
influenced by future changes in emissions of pollutants, climate,
and stratospheric ozone, and will have significant consequences
for human health and the environment [11]. UV radiation is one
of the important factors for the formation of photochemical
smog, which includes troposphere ozone and aerosols; it also
initiates the production of hydroxyl radicals (˙OH), which
control the amount of many climates- and ozone-relevant gases
(e.g., methane and HCFCs) in the atmosphere [12]. Numerical
models predict that future changes in UV radiation and climate
will modify the trends and geographic distribution of ˙OH, thus
affecting the formation of photochemical smog in many urban
and regional areas [12]. Concentrations of ˙OH are predicted
to decrease globally by an average of 20% by 2100, with local
concentrations varying by as much as a factor of two above
and below current values. If emissions of anthropogenic air
pollutants from combustion of fossil fuels, burning of biomass,
and agricultural activities continue to increase, concentrations
of troposphere O3 will tend to increase over the next 20-40
years in certain regions of low and middle latitudes because
of interactions of emissions, chemical processes, and climate
change. Climate-driven increases in temperature and humidity
will also increase production of tropospheric O3 in polluted
regions1 [11,13].
Stratospheric ozone layer depletion has been recognized as
a problem by the Vienna Convention for the protection of the
ozone layer and the 1987 Montreal Protocol (MP) for quadrennial
ozone assessments and monitoring of stratospheric ozone
concentrations and emissions of ozone destructing substances
[14]. Industrialized countries have contributed significantly to
the problem by releasing chlorofluorocarbons (CFCs) and halons
in the atmosphere [15]. The effect of these chemicals, which were
known for their inertness, non flammability and non toxicity, was
discovered in 1874 [16]. Action to deal with the effects of CFCs
and halons was initiated in 1985 in a 49-nation UN meeting. 21
nations signed a protocol limiting ozone depleting substances
(ODS) including CFCs and halons. An Interim Multilateral
Fund under the Montreal Protocol (IMFMP) was established
to provide loans to finance the costs to developing countries in
meeting global environmental requirements [17]. The IMFMP
is administered by the World Bank, the UN Environmental
Program, and the UN Development Program [18]. As a result of
these agreements, global consumption of CFCs fell by more than
70% between 1986 and 1996 [17]. The campaign against CFC
use in aerosols and packaging is often presented as an example
of a massive and noble behavior and social change in populations
[17]. On a global scale, if 1990 is treated as the reference period, then moderately high annual mean maximum ozone
concentrations of 60 parts per billion (ppb) were anticipated
in central Europe, China, Brazil, South Africa, and eastern North
America during summertime.
By 2030, under a high emission cicumstances, the area
experiencing a background of 60 ppb was expected to expand
significantly, especially in Europe and North America [19,20]. By
2060, most of the populated continental areas would experience
ozone concentrations of at least 60 ppb [21-23]. By 2100, much
of the Northern hemisphere was expected to have annual mean
maximum ozone levels of 60 ppb, as were most of the populated
areas of the Southern Hemisphere [24]. The global average
populationweighted8-hr maximum ozone concentration was
likely to increase by 9.4 parts per billion per volume (ppb)with
approximately 500,000 additional deaths compared with the
same concentration in 2000, with the largest increases over
South Asia (nearly15 ppb) and with large increases in the Middle
East, Southeast Asia, Latin America, and East Asia [25,26].
By the end of the twenty-first century anthropogenic climate
change alone would decrease background ozone concentrations
over the United States, while ozone produced internally would
increase [27].
The authors anticipated that over the eastern United States,
up to 12 additional days annually would exceed 80 ppb [28]. In
England, whales and United States when the authors assumed
thresholds for the health effects of ozone, the increase in
health effects due to ozone was relatively small. If no threshold
is assumed, then ozone is projected to increase premature
deaths by 10, 20, and 40% for the years 2020, 2050, and 2080,
respectively [29]. Using a threshold of 25 ppb, 191,000 deaths
worldwide could be avoided using currently enacted legislation,
and 458,000 deaths could be avoided using maximum
reasonable reduction technologies. On the basis of a limited
number of modeling studies, climate change is likely to increase
ozone concentrations in high-income countries when precursor
emissions are held constant, leading to increased morbidity and
mortality [30].
Increased UV-B through stratospheric ozone depletion leads
to an increased chemical activity in the lower atmosphere (the
troposphere) [31]. The effect of stratospheric ozone depletion
on tropospheric ozone is small (but significant) as compared
to the ozone generated anthropogenically in areas already
experiencing air pollution. Modeling and experimental studies
suggest that the impacts of stratospheric ozone depletion on
tropospheric ozone are different at different altitudes and in
different chemical regimes [32]. As a result, the increase in
ozone due to stratospheric ozone depletion may be greater in
polluted regions [33]. Attributable effects on concentrations
are expected only in regions where local emissions make minor
contributions. The vertical distribution of NOX (NO _ NO2), the
emission of volatile organic compounds and the abundance of
water vapor, are important influencing factors [34]. The longterm
nature of stratospheric ozone depletion means that even a small increase in tropospheric ozone concentration can have
a significant impact on human health and the environment [11].
The impact of the interaction between ozone depletion and
future climate change is complex and a significant area of current
research [35]. For air quality and tropospheric composition, a
range of physical parameters such as temperature, cloudiness,
and atmospheric transport will modify the impact of UV-B
[36]. Changes in the chemical composition of the atmosphere
including aerosols will also have an impact. For example,
tropospheric OH is the ‘cleaning’ agent of the troposphere [31].
While increased UV-B increases the OH concentration, increases
in the concentration of gasses like methane, carbon monoxide,
and volatile organic compounds will act as sinks for OH in
the troposphere and hence change air quality and chemical
composition in the troposphere. Also, changes in the aerosol
content of the atmosphere resulting from global climate change
may affect ozone photolysis rate coefficients and hence reduce
or increase tropospheric ozone concentrations [11].
Stuation in Pakistan
The ozone layer depletion and its harmful impact on living
beings have been a greater concern of all the scientists all over
the world including Pakistan [36]. The annual, monthly and
seasonal analyses have been performed to check the status
[37,38]. The variation in total column of ozone has been observed
during these analyses and decrease in total column of ozone has
been seen in all the investigations from 1987-2008.
Annual analysis
The annual analysis of total column ozone data has been
done by generating a time series for the period 1987- 2008. The
time series shows that there is a sharp decline in the thickness of
ozone layer particularly from 1993 onwards over Pakistan. The
annual ozone anomalies have been calculated with the help of
observed data. The anomalies show a decreasing trend of ozone
and this loss in total column ozone give a clue that ozone layer
thickness has reduced and thinness has increased during the
study period. The total change observed in ozone over the last
21 years (1987-2008) is−5.67Dobson units (D.U). It is assumed
that this decrease can be due to huge gaseous emissions of
Carbondioxide (CO2) and particularly Chlorofluorocarbons
(CFC’s) which is the main cause of ozone depletion over Pakistan.
Monthly analysis
Monthly analysis of ozone shows a lot of variations in ozone
thickness throughout the year. There are months in which the
ozone thickness remains far above the permissible limits of
ozone (i.e. 260 D.U. in tropics near the equator) whereas, on
the other hand, there are few months when the ozone layer
becomes thin and the value of ozone calculated below the 260
D.U. The highest amounts of total column ozone over Pakistan
occur from March–May, the amount then starts to decrease
from June–September. While the lowest amount of total column
ozone occurs from October–December, the amount of zone again increases from January–February. The total decrease in ozone
thickness is −4.2 D.U which is statistically significant. The wind
transport of ozone is principally responsible for this monthly
variation of ozone patterns.
Seasonal analysis
The behavior of ozone varies from season to season. The
highest level of ozone occurs in spring, not in summer and
the lowest in the autumn instead of winter. In winters, the
concentration of ozone remains above permissible limit, i.e., 260
D.U. The highest value of ozone in winters was in 1990 which is
292 D.U. In spring, the concentration of ozone also remains above
the permissible limit of 260 D.U. The highest value of ozone in
springs was in 1991 i.e., 316 D.U. The peak value of ozone in
summers is 292 D.U in 1990 & 2005.The ozone layer thinning is
maximum all over the globe during autumn. The same situation
can be analyzed during the autumn season in the atmosphere
above Pakistan. The value of ozone reduced to a large extent
and it falls below the permissible limit of 260 D.U. The lowest
value of ozone in autumn is 242 D.U in 1998.The total change
calculated in spring is −10.5 D.U, summer is −6.3 D.U, winter is
−3.15 D.U while in autumn, it is−2.0 D.U. The wind transport is
the major factor responsible for the seasonal variations of ozone
patterns. The relationship between ozone depletion and solar
radiation has also been seen in the same study. It is concluded
that ozone and solar radiations are inversely proportional to
each other. From December to April when solar radiations are
less intense the ozone thickness reaches to its peak values.
Whereas from May till November due to the high intensity of
solar radiations the concentration of ozone minimize and its
concentration during October and November reduced so much
that ozone reaches to its threshold values over Pakistan [8]. It
has been observed from studies on marine organisms that there
is a remarkable increase in the flux of UV radiation reaching the
Arabian sea through the ozone filter. It is effective particularly in
Pakistan atmospheric region (PAR) that is situated in the west
and northwest of South Asia. It lies from 23.45 to 36.75 in the
northern latitudes, and from 61 to 75.5 eastern longitudes. Ozone
depletion has also effects on marine life as shown by studies.
Studies conducted on Baluchistan and Sindh costs showed that
there is a negativecorrelation between the yield of fish and UV
radiation, as the UV-B increases due to ozone depletion, the yield
of fish decreases [5].
Recommendations
In order to address the challenges posed by climatic change
and to protect the ozone layer following steps can be taken.
- Plan and implement the national climate change policy and action plan.
- Promote the use of ozone-friendly technologies.
- Phase out the use of ozone-depleting substances with the provisions of Montreal protocol.
- Long-term monitoring of the expected decrease in polar and global ozone loss in response to the measures taken based on the Montreal Protocol and its amendments is required. The ultimate goal is to obtain accurate information on the evolution of the ozone layer (total column) and its effect on surface, UV, together with the monitoring of columns of ozone depleting substances (ODS); CFC’s and their replacement HCFCs, and halons. Specifically, information on the changes (trends) in chlorine loading is needed, both in the troposphere and in the stratosphere.
- More detailed policy-relevant information includes the monitoring of the height distribution of ozone and ODS compounds, in addition to total column information.
- Continued assessment and improvement of regulatory action are needed until the recovery of the ozone layer is a fact, currently not expected to happen before 2050.
- A global daily monitoring of the noontime clear-sky UV Index will also give information on the occurrence of extreme values, which are typically related to ozone depletion events.
- The main public health responses to the projected health impacts of climate change are mitigation and adaptation. Adaptation is not an effective risk management strategy for poor air quality because physiologic mechanisms to decrease susceptibility to ozone and other air pollutants are limited. Evidence suggests that reducing current tropospheric ozone concentrations reduces morbidity and mortality, with significant savings in medical care costs. Additional research is needed to reduce the uncertainties associated with projections of the health impacts of changing concentrations of ozone. Research is needed to better understand the impacts of future emissions pathways, climate change impacts on concentrations of fine particles and gases, how changing weather patterns could influence the frequency and severity of episodes of poor air quality, population sensitivity, and how these factors might interact [30].
Conclusion
It seems the most important cause of Ozone depletion
seems to be anthropogenic. Therefore, a lot of research needs
to be done particularly in Pakistan. It is the right time to change
behavior towards the environment by creating awareness among
public. However, Montreal protocol activities have shown the
commitments in the entire world including Pakistan. But there
are so many men – made chemicals, which need to be controlled
in order to overcome the problems of ozone – depletion.
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