The hazy skies over the 2008 Summer Olympics have placed Beijing's air quality at the top of news headlines for more than a month. However, outdoor air pollution, whether in the form of visible haze or invisible ozone and carbon monoxide, is a problem in nearly every country in the world.
Outdoor air pollution alone causes an estimated 800,000 deaths each year (an additional 1.6 million premature deaths are attributable to indoor air pollution, the subject of a previous EarthTrends Monthly Update). In many urban areas, especially in the developing world, air pollution is the single greatest environmental threat to human health (WDI, 2007).
However, cities in both the developed and developing worlds that were once heavily polluted have been able to improve air quality to within safe levels, often dramatically. These cities’ success has often come from a combination of stricter standards, sensible regulations, and integrated transit solutions.
Types of Air Pollution
Three widespread air pollutants cause the most damage to the environment and human health:
- Sulfur dioxide (SO2). Produced when fossil fuels high in sulfur (coal and oil) are burned, during smelting, or from other industrial processes.
- Nitrogen oxides (NOx). Produced from both mobile sources like cars and stationary sources like power plants.
- Particulate matter (PM). Refers to fine particles suspended in air. PM are classified by its size; particles of less than 10 microns in diameter are designated as PM10, and particles of less than 2.5 microns are PM2.5. PM is released from vehicles, power plants, and industrial process in nearly equal measure.
Other pollutants include:
- Carbon monoxide (CO). An odorless gas emitted from vehicles, particularly those without a catalytic converter. Some emissions result from industrial fossil fuel burning.
- Lead. Emitted in particulate form by vehicles burning leaded gasoline, or from lead smelting and other metal processes.
- Ozone. Created under certain weather conditions (sunny, still days) by VOCs and nitrogen oxides. Unlike the protective layer of ozone found in the earth’s stratosphere, ozone in the troposphere—where most plants and animals live—creates a photochemical smog and is highly toxic.
- Volatile organic compounds (VOCs). Include hydrocarbons, alcohols, aldehydes, and ethers. VOCs play a role in ozone formation and are emitted by industrial processes and vehicles.
Air Pollution's Global Extent
In the United States and in most other developed countries, NOx and SO2 emissions, generally associated with fossil-fuel driven power generation, have significantly decreased even as electricity production has increased. Most emissions from vehicles have decreased, too, while the total number of vehicle miles traveled in the United States has increased by nearly 150% since 1970. These results are generally due to the stricter standards for both engines and fuels.
In most developing countries, however, increasing numbers of vehicles, power plants, and factories have not been accompanied by cleaner technologies or stricter regulations. Between 1990 and 2000, air pollution increased by around 50% in developing countries (see Figure 1). Air pollution has been a particular problem in Asia, which accounts for 65% of all pollution-related deaths (see Figure 2).
Figure 1: Air Pollution Trends, 1990-2000
Total of sulfur dioxide, nitrogen oxides, and non-methane VOC emissions
Source: EarthTrends, 2005
Figure 2: Global Distribution of Deaths from Urban Air Pollution
Click for a larger image (PDF, 2.0MB)
Source: WHO, 2002
The Health and Enviromental Effects of Air Pollution
The adverse health effects of exposure to air pollution are well documented. One World Bank study found that for every 30-μg/m3 increase in daily PM10 concentrations, symptoms of upper respiratory diseases increased by 9%. The observed increase was the same in highly exposed populations (who live or work near roads or industry) and less-exposed people who live in a more protected environment.
Even a slight 10μg/m3 increase in PM10 is associated with a 1 to 2% increase in cardiovascular mortality and a 3 to 6% increase in respiratory mortality. Other studies have linked increased air pollution to low birth weights (Gouveia, Bremner and Novaes, 2004).
Air pollution can also seriously damage the natural environment. Sulfur dioxide contributes to acid rain, which damages lakes, rivers, and forests. Reactive nitrogen deposited from NOx emissions can over-fertilize land ecosystems, runoff from which can cause eutrophication of coastal zones. In the eastern United States, growing concerns over air pollution and acid rain led to stringent regulations for power plants in the 1970s and 1980s.
Figure 3: Major Sources and Health and Environmental Effects of Air Pollutants
See also: Australian National Pollutant Inventory – Substance Fact Sheets
What Can Be Done to Improve Air Quality?
In the United States, the landmark 1970 Clean Air Act Amendments established National Ambient Air Quality Standards (NAAQS). The NAAQS are based on health and welfare effects of the major air pollutants (SO2, NOx, PM10 and PM2.5) as well as lead, ozone, and carbon monoxide. Most places in the United States regularly meet or exceed these standards for all pollutants. The notable exception is ozone concentrations, which have slowly declined on average but increased in some regions.
Other countries, like China, still struggle to meet their own national standards, which are often less stringent. A 2007 government report concluded that 48% of urban residents in China lived in cities not meeting the national air-quality standards. The burning of coal alone is estimated to cause 50,000 deaths and 400,000 cases of chronic bronchitis. The World Bank has estimated that by 2020 China will spend $390 billion (equivalent to 13% of projected GDP) on healthcare for illnesses resulting from coal burning (National Academies, 2007).
While some developing-world cities are still grappling with an ever-worsening situation, a few have been able to control (or at least lessen) air pollution. For example, Bangkok – a city that just 15 years ago was infamous for its heavily polluted air – has pollutant levels that meet U.S. standards and approach the stricter European standards. Bangkok’s success was due partly to luck and the specifics of its geography and industry structure (see case study below), but can also in large part be attributed to innovative solutions.
Bangkok’s approach – combining sensible regulations like tailpipe emissions standards, simple fixes like street washing, and a substantial mass-transit expansion – has become a model for air-quality management. And while specific conditions may vary between cities, the lessons learned in Bangkok are fundamentally applicable everywhere. Integration is key: no one approach is going to solve the problem alone. Urban air pollution is a complex and multifaceted problem, posing challenges at the intersection of health and environment, transport and engineering, and economics and policy.
Beijing’s pollution problem illustrates the need for integrated solutions to air-quality problems. Even last-ditch efforts by the Chinese government to control air pollution by taking half of all private cars in Beijing off the road have not been particularly effective. (For more, see a recent article by Deborah Seligsohn, Director of WRI's China Program). While cars are certainly major contributors to local air pollution, factors outside of the city seem to be more important determinants of the city’s air quality. Small factories in neighboring Hebei province emit VOCs, and big coal mines and coal-fired power plants in Shanxi province (upwind of Beijing) spew particulate matter.
Thus the solution to Beijing’s pollution problem may be more complicated than simply taking cars off the road, or limiting tailpipe emissions. The real underlying drivers of the problem are farther afield and will require serious cooperation between cities, businesses, and both provincial and central government agencies.
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Box 1: Bangkok's Air Pollution Success Story Forty years ago, pollution was not a problem in Bangkok; there was not even a word for pollution in the Thai language until 1976. By the mid-1990s, however, major economic and demographic changes had resulted in air quality problems throughout Asia. As Thailand’s economy grew, the Bangkok metropolitan region urbanized rapidly. Between 1991 and 2000, the number of registered vehicles in the city more than doubled. Motorcycles were a preferred mode of transportation and accounted for nearly half of the city’s total vehicle fleet. Up to 80% of these used two-stroke engines, which are lighter and produce more power than four-stroke engines but emit twice as much particulate matter (APEIS, 2004). The country had no emissions standards and an underdeveloped mass-transit system. Vehicles accounted for an estimated 80% of NOx emissions, 75% of carbon monoxide emissions, 54% of PM emissions, and nearly 100% of hydrocarbon emissions (Bangkok State of the Environment, 2001). Particulate pollution was also created by dust from the city’s construction boom and from the many Buddhist crematoria in and around the metropolitan area, most of which relied on wood and charcoal as their primary fuel. By 1992, pollution was reaching critical levels by roadsides and during rush hours. PM10 levels were reaching more than 300 μg/m3, far above the World Health Organization’s recommended maximum level of 20 μg/m3. Another study found that 28 percent of children tested at several Bangkok schools had bloodstream lead concentrations higher than the acceptable limit. Starting in 1992, the city began to address its air-quality problems with the enactment of emissions standards. Modeled after European regulations, the stringency of the Thai standards was unprecedented in Asia. Despite resistance from oil companies and Japanese automobile manufacturers, officials introduced catalytic converters to reduce the toxicity of tailpipe emissions. In 1995, Thailand phased out leaded gasoline entirely, and lead pollution dropped to an insignificant 0.22 μg/m3 in a few years. These regulations were coupled with simpler, more practical measures. Streets were washed and road shoulders were paved in an effort to reduce dust clouds. The public was offered free engine maintenance manuals and tune-ups. Black-smoke inspection stations were set up to monitor old trucks and buses, and several motorcycle- and vehicle-free streets were created. Mass transit was also expanded. In 1999, the city’s new electric train system began operation. By 2003, its daily ridership was more than 630,000. More lines are under development, and a Bus Rapid Transit (BRT) system with dedicated high-speed bus lanes is also in the works. Today, air quality in Bangkok exceeds American standards and falls only slightly below those of the European Union. PM concentrations have fallen by an impressive 47%. The city, while not as clean as Singapore or Tokyo, has proven that effective air quality management does not necessitate an authoritarian government or huge financial investments. And the worries of automobile manufacturers and oil companies seem to have been overstated: today, Thailand produces 1.25 million cars and 3.5 million motorcycles, making it Asia’s third-largest vehicle exporter (Fuller, 2007). Bangkok’s success was to some extent a function of luck and location. Bangkok is not surrounded by pollution-trapping mountains, as is famously the case in Beijing and Los Angeles. And Bangkok is not surrounded by coal-burning power plants. (Upwards of 70% power plants in Thailand use natural gas, a cleaner-burning fuel.) But the city’s unprecedented turnaround was due in large part to good governance, innovative regulation, and simple, cost-effective policies. |
A Practical, Innovative Approach
Solutions – whether voluntary, mandatory, or incentive-based – need to be practical and innovative. They also need to be adapted to the specific geographical and economic conditions of the cities and regions in which they are to take effect. When supervised by knowledgeable environmental managers committed to good environmental governance, such measures can go a long way to minimizing the harmful health and environmental effects of air pollution.
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RELATED LINKS:
Thai Ministry of Natural Resources and Environment – Pollution Control Department
UN Environment Programme – Urban Environment Unit
World Health Organization – Health and Environment Linkages Initiative
The City Fix Blog at EMBARQ, the WRI Center for Sustainable Transport
EARTHTRENDS:
Data: Carbon monoxide emissions
Data: Nitrogen oxides emissions
Data: Non-methane VOC emissions
Data: Sulfur dioxide emissions
Article: Sustainable Cities, Sustainable Transportation
Article: Acid Rain – Downpour in Asia
