Analyzing The Quality Of Air In Megacities Environmental Sciences Essay
In the author's perspective "Clean Air for Megacities" Parrish and T. Zhu describe the problem of air pollution in megacities linked to the size of its population. In the year 2008 more than half of the Earth's population is living in the cities. A megacity is a city with a population exceeding the amount of 10 million inhabitants. The number of these cities grew from three in 1975 up to nineteen in 2007 and is predicted to increase to twenty seven in 2025. There are very large sources of air pollutants and climate-forcing agents. A large population size of the city increases the health impacts, like respiratory and cardiovascular diseases. The World Health Organization guideline for particulate matter specifies the levels of allowed particulate matter in the air. However all of megacities exceed this level. According to Parrish and Zhu a larger population density could do something to mitigate climate change yet, because it may provide more efficient energy use and then lower per capita CO2 emissions .
The situation of air pollution in big cities is more severe than in the countryside. Citizens in cities have cars that they use every day for travelling to the work. There is a lot of people not willing to use the public transport. Last but not least issue is that many of the megacities do not provide their inhabitants with good conditions for walking or for using a bike. On the other hand, megacities have better possibilities and conditions to improve the state of their air quality.
The other authors of articles on the topic of air pollution describe the problem of air pollution from different perspectives, but in general we can say that they support the opinion about the serious state of air quality in cities.
Description of air pollution in megacities
Air quality in megacities
The authors  speculate about possibilities of big cities to improve the state of air quality. Megacities are usually in a good economic condition, so they are better able to take measures to improve the air quality. This means for example new infrastructure, in which the traffic bypasses the city centre. The exhaust fumes from cars in such case do not pollute the air of the city in such concentrations. The showed air pollutant levels that accompanied past development can be avoided .
As an example the authors  use the city of Los Angeles, where ozone concentrations reached very high levels before responding to control strategies over the precedent three decades. In Mexico City the high ozone concentrations were showed later and peaked at the beginning on 1990. These concentrations never attained the peak of the concentrations in Los Angeles, and have decreased faster than in Los Angeles .
In the last author's example - Beijing - are available limited research data sets. In these data sets is showed, that ozone concentrations were low in 1980s, but they are rapidly increasing, especially according to concentrations measured by the preparations for the Olympic Games in 2008. Beijing has previously realized belligerent emission controls on automobiles and implemented the limits for heavy truck traffic in the city at night time to alleviate traffic overcrowding . Beijing really exceeds the level given by WHO guideline for suspended particulate matter  and for SO2 .
In these three examples as well as in almost all megacities are the motorized vehicles the main emitters of greenhouse gases, because the growth of vehicles goes together with the city development. It is possible and cost-effective for megacities to introduce emission controls on vehicles sooner that the more expensive and long time demanding regionally control policies will be needed .
Possible impacts of air pollution in megacities
The cars and motorized vehicles in cities are the biggest problem for the air pollution. The exhaust fumes cause many types of emissions which result in some health - problems for the citizens. It is quite common that big cities have their industrial part and in such areas more measures of emissions should be done.
The authors  also see the problem in the possible health - impacts. It is necessary to understand the dual role of particulate matter as the air pollutant with the big health-impacts and as both a cooling and warming agent for climate. Particulate matter is supposed to recently substitute for a large fraction of the warming impacts of greenhouse gases. But in this respect find the authors some problem. There is a big uncertainty in our understanding of particulate matter's net climate impacts and on the different time and space scales on which particulate matter stay in atmosphere and then affects climate. While the CO2 is mixed almost consistently all over the Earth, the shorter-lived particulate matter has robust regional differences in its impacts on temperature and precipitation model .
The other authors provide the opinion, that the role of particulate matter is important from the perspective of health problems and of course from perspective of air pollution and climate change . The epidemiological evidence confirms the impacts of particulate matter on human health. WHO perceives the dominant effects to respiratory and cardiovascular diseases .
John R. Lyman (Clean Air for Asia) says that China tries to implement new and alternative energy technologies into its technology. Generally, in Beijing is established that the obligatory deals are not possible without a most important restructuring of the electric power sector. Power generation and distribution are checked by regional governments .
China wanted to implement some reforms. The Chinese people are looking for practical answers - for example how to undertake structural reforms. Policymakers consulted these issues with many specialists and organizations, but they still do not have all the answers .
In perspective of Jennifer Sills "A Greener Future For Chinas Cities" is described, that only 60.5 % of the 287 big cities in China which were monitored in 2007 had air quality that met the standard of Ministry of Environmental Protection of China. At the beginning of 2008 the World Wildlife Fund worked together with Shanghai and Baoding on the topic how to realize low-carbon development in China's urban areas .
According to Sills, the biggest problem of air pollution is that some countries do not have obligations under the Kyoto protocol. So they are not obliged to account for emissions from loss of terrestrial carbon. Furthermore, some countries that are under commitments do not account some of their sources of emissions .
3. Conclusion and possible solutions
In my opinion it is absolutely clear that the air pollution in cities represents a serious problem both for citizens of these cities as well as for surrounding nature. In case of citizens, I see the biggest issues in health-related problems (especially respiratory diseases), resulting from the air pollution and also in excessive noise which can undoubtedly disturb many people.
I have my own personal experience with growing up in the industrial city and I have chronic bronchitis till today.
The situation of air pollution in big cities is more serious than in the countryside, because of their industry and high populations. On the other hand, the cities have better opportunities to improve this situation given their stronger economic conditions. They are thus able to take such measures like building new infrastructure, new paths for bikes or improvement of public transport.
I believe that good solution how to improve air quality in cities is to use alternative means of transport. Specifically, I would propose to reduce using cars for almost every purpose, and instead of that to use the public transport more as well as walking or riding bike. I understand that it can be a problem with the infrastructure, especially if we think about biking routes. Unfortunately, there are no special bike routes in many of big cities, so it is impossible or at least uncomfortable to ride the bike there. The problem might be that in case of some megacities, it is not possible to built new bike routes and use the bike for travelling from one side of the city to the other side. In such cases, the good solution could be to use bikes in city centers. In some cities it is possible to take the bike at one place, use it for free in the city center area and then after you don't need it to give the bike back to the special station at different place. I see this is a possible good solution for each megacity.
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