Cities[edit]
Air pollution is usually concentrated in densely populated metropolitan areas, especially in developing countries where environmental regulations are relatively lax or nonexistent[citation needed]. However, even populated areas in developed countries attain unhealthy levels of pollution with Los Angeles andRome being two good examples.[53]
NATA[edit]
The National-Scale Air Toxics Assessment (NATA) is EPA's ongoing comprehensive evaluation of air toxics in the U.S. EPA developed the NATA as a state-of-the-science screening tool for State/Local/Tribal Agencies to prioritize pollutants, emission sources and locations of interest for further study in order to gain a better understanding of risks. NATA assessments do not incorporate refined information about emission sources, but rather, use general information about sources to develop estimates of risks which are more likely to overestimate impacts than underestimate them. NATA provides estimates of the risk of cancer and other serious health effects from breathing (inhaling) air toxics in order to inform both national and more localized efforts to identify and prioritize air toxics, emission source types and locations which are of greatest potential concern in terms of contributing to population risk. This in turn helps air pollution experts focus limited analytical resources on areas and or populations where the potential for health risks are highest. Assessments include estimates of cancer and non-cancer health effects based on chronic exposure from outdoor sources, including assessments of non-cancer health effects for Diesel Particulate Matter (PM). Assessments provide a snapshot of the outdoor air quality and the risks to human health that would result if air toxic emissions levels remained unchanged.[54]
| Most Polluted World Cities by PM[55] | |
|---|---|
| Particulate matter, μg/m³ (2004) | City |
| 168 | Cairo, Egypt |
| 150 | Delhi, India |
| 128 | Kolkata, India (Calcutta) |
| 125 | Tianjin, China |
| 123 | Chongqing, China |
| 109 | Kanpur, India |
| 109 | Lucknow, India |
| 104 | Jakarta, Indonesia |
| 101 | Shenyang, China |
Governing urban air pollution – a regional example (London)[edit]
In Europe, Council Directive 96/62/EC on ambient air quality assessment and management provides a common strategy against which member states can "set objectives for ambient air quality in order to avoid, prevent or reduce harmful effects on human health and the environment . . . and improve air quality where it is unsatisfactory".[56]
On 25 July 2008 in the case Dieter Janecek v Freistaat Bayern CURIA, the European Court of Justice ruled that under this directive[56] citizens have the right to require national authorities to implement a short term action plan that aims to maintain or achieve compliance to air quality limit values.[57]
This important case law appears to confirm the role of the EC as centralised regulator to European nation-states as regards air pollution control. It places a supranational legal obligation on the UK to protect its citizens from dangerous levels of air pollution, furthermore superseding national interests with those of the citizen.
In 2010, the European Commission (EC) threatened the UK with legal action against the successive breaching of PM10 limit values.[58] The UK government has identified that if fines are imposed, they could cost the nation upwards of £300 million per year.[59]
In March 2011, the City of London remains the only UK region in breach of the EC’s limit values, and has been given 3 months to implement an emergency action plan aimed at meeting the EU Air Quality Directive.[60] The City of London has dangerous levels of PM10 concentrations, estimated to cause 3000 deaths per year within the city.[61] As well as the threat of EU fines, in 2010 it was threatened with legal action for scrapping the western congestion charge zone, which is claimed to have led to an increase in air pollution levels.[62]
In response to these charges, Boris Johnson, Mayor of London, has criticised the current need for European cities to communicate with Europe through their nation state’s central government, arguing that in future "A great city like London" should be permitted to bypass its government and deal directly with the European Commission regarding its air quality action plan.[60]
In part, this is an attempt to divert blame away from the Mayor's office, but it can also be interpreted as recognition that cities can transcend the traditional national government organisational hierarchy and develop solutions to air pollution using global governance networks, for example through transnational relations. Transnational relations include but are not exclusive to national governments and intergovernmental organisations [63] allowing sub-national actors including cities and regions to partake in air pollution control as independent actors.
Particularly promising at present are global city partnerships.[64] These can be built into networks, for example the C40 network, of which London is a member. The C40 is a public ‘non-state’ network of the world’s leading cities that aims to curb their greenhouse emissions.[64] The C40 has been identified as ‘governance from the middle’ and is an alternative to intergovernmental policy.[65] It has the potential to improve urban air quality as participating cities "exchange information, learn from best practices and consequently mitigate carbon dioxide emissions independently from national government decisions".[64] A criticism of the C40 network is that its exclusive nature limits influence to participating cities and risks drawing resources away from less powerful city and regional actors.
Atmospheric dispersion[edit]
Main article: Atmospheric dispersion modeling
The basic technology for analyzing air pollution is through the use of a variety of mathematical models for predicting the transport of air pollutants in the lower atmosphere. The principal methodologies are:
- Point source dispersion, used for industrial sources.
- Line source dispersion, used for airport and roadway air dispersion modeling
- Area source dispersion, used for forest fires or duststorms
- Photochemical models, used to analyze reactive pollutants that form smog
The point source problem is the best understood, since it involves simpler mathematics and has been studied for a long period of time, dating back to about the year 1900. It uses a Gaussiandispersion model for continuous buoyant pollution plumes to predict the air pollution isopleths, with consideration given to wind velocity, stack height, emission rate and stability class (a measure of atmosphericturbulence).[66][67] This model has been extensively validated and calibrated with experimental data for all sorts of atmospheric conditions.
The roadway air dispersion model was developed starting in the late 1950s and early 1960s in response to requirements of the National Environmental Policy Act and the U.S. Department of Transportation (then known as the Federal Highway Administration) to understand impacts of proposed new highways upon air quality, especially in urban areas. Several research groups were active in this model development, among which were: the Environmental Research and Technology (ERT) group in Lexington, Massachusetts, the ESL Inc. group in Sunnyvale,California and the California Air Resources Board group in Sacramento, California. The research of the ESL group received a boost with a contract award from the United States Environmental Protection Agency to validate a line source model using sulfur hexafluoride as a tracer gas. This program was successful in validating the line source model developed by ESL Inc. Some of the earliest uses of the model were in court cases involving highway air pollution, the Arlington,Virginia portion of Interstate 66 and the New Jersey Turnpike widening project through East Brunswick, New Jersey.
Area source models were developed in 1971 through 1974 by the ERT and ESL groups, but addressed a smaller fraction of total air pollution emissions, so that their use and need was not as widespread as the line source model, which enjoyed hundreds of different applications as early as the 1970s. Similarly photochemical models were developed primarily in the 1960s and 1970s, but their use was more specialized and for regional needs, such as understanding smog formation in Los Angeles, California.
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