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10.1146/annurev.energy.27.122001.083421
Annu. Rev. Energy Environ. 2002. 27:397–431
doi: 10.1146/annurev.energy.27.122001.083421
Copyright
c
 2002 by Annual Reviews. All rights reserved
URBAN AIR POLLUTION IN CHINA:
Current Status, Characteristics, and Progress
Kebin He, Hong Huo, and Qiang Zhang
Department of Environmental Science and Engineering, Tsinghua University,
Beijing 100084, China; e-mail: , ,

Key Words Chinese cities, urban air quality, atmospheric pollutants, control
strategies, Beijing
■ Abstract China is rapidly developing as evidenced by enhanced urbanization
and industrialization and greatly increased energy consumption. However, these have
brought Chinese cities a variety of urban air pollution problems in recent decades. Dur-
ing the 1970s, black smoke from stacks became the characteristic of Chinese industrial
cities; in the1980s,many southern cities began tosuffer serious acid rain pollution; and
recently, the air quality in large cities has deteriorated due to nitrous oxides (NO
x
), car-
bon monoxide (CO), and photochemical smog, which are typical of vehicle pollution.
Some cities now have a mixture of these. Urban air pollution influences both the health
of citizens and the development of cities. To control air pollution and protect the atmo-
spheric environment, the Chinese government has implemented a variety of programs.
This paper first reviews the current status of air quality in Chinese cities, especially
key cities, then describes the characteristics of some major urban air pollutants, includ-
ing total suspended particles (TSP), respirable particles 10 microns or less in diameter
(PM

10
), very fineparticles2.5microns orless in diameter (PM
2.5
), sulfurdioxide (SO
2
),
acid rain, NO
x,
and photochemical smog. Two specific topics, SO
2
and acid rain control
and vehicle emission control, are used to illustrate the actions that the government has
taken and futureplans.Finally,acase study of the Chinese capital, Beijing, is presented
with adiscussion of its mainair pollution problems,recentlyimplemented control mea-
sures and their effects, and future strategies for urban air quality improvement.
CONTENTS
INTRODUCTION 398
OVERVIEW OF CURRENT URBAN AIR QUALITY STATUS 401
CHARACTERISTICS OF URBAN AIR POLLUTANTS 404
TSP 404
PM
10
and PM
2.5
407
SO
2
409
Acid Rain 410
NO

x
411
1056-3466/02/1121-0397$14.00
397
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O
3
and Photochemical Smog 414
Indoor Pollutants 414
ECONOMIC DAMAGE 416
CONTROL PROGRESS AND PROSPECTS 418
SO
2
Pollution and Acid Rain Control 418
Vehicle Emission Pollution Control 422
Beijing—A Case Study for Urban Air Pollution
Control in China 424
CONCLUSION 427
INTRODUCTION
China has achieved rapid economic growth, industrialization, and urbanization in
recent decades, with the annual increases in GDP of 8%–9% (1). Cities, as a kind
of hallmark for progress, have played a significant facilitating role in Chinese eco-
nomic and social development. Since the Open Policy, the urbanization of China
has accelerated with the proportion of urban population to the total population in
China increasing from 18% in 1978 to 31% in 1999, a growth rate three times the

world average during this period (1–3). By the end of the twentieth century, the
explosion in economic growth also made China the world’s second largest energy
consumer after the United States. Energy consumption, especially coal consump-
tion, is the main source of anthropogenic air pollution emissions in Chinese cities.
Since the late 1970s, the total energy consumption has greatly increased from 571
million tonnes of coal equivalent (Mtce) in 1978 to 1220 Mtce in 1999 (Figure 1)
(1). Coal, the primary energy source, accounted for about 74% of the total energy
consumption during this period, and its use is the origin ofmany air pollution prob-
lems, such as TSP pollution, SO
2
pollution, and acid rain. Crude oil consumption
has increased with the average growth rate of 6% per year in the past decades.
Part of this increase is due to the rapid expansion of motor vehicle fleets. This has
heightened ambient pollution by NO
x
, CO, and related pollutants in large cities
(4, 5).
China’s growing energy consumption, reliance on coal, and rapidly increasing
vehicle population place a heavy burden on urban atmosphere in China, and urban
air pollution is rapidly emerging as a major environmental issue. Many cities have
sufferedfrom increasingly serious air pollution since the1980s.Attheearly 1990s,
less than 1% of over 500 cities in China reached Class I (the least serious of three
levels) of the national air quality standards (6).Duringthe1990s, some megacities,
such as Beijing, Shenyang, Xian, Shanghai, and Guangzhou, were always listed
among the top 10 most polluted cities in the world. Urban air pollution in China
and has probably caused significant public health effects and economic damage.
To protect public health and environmental quality, the Chinese government has
undertaken a series of actions including:
1. The promulgation of laws, regulations, and standards. The environmental
policydecision-makingsystemoftheChinesegovernment consists chiefly of three

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URBAN AIR POLLUTION IN CHINA 399
Figure 1 Primary energy consumption in China from 1978–1999.
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organs. One is the Environment and Resources Protection Committee (ERPC) of
the National People’s Congress(NPC);itmakes policy decisions for the protection
of the environment, passes legislation, and supervises its enforcement. Another is
the State Environmental Protection Commission (SEPC) of the State Council; it
drafts policies, regulations, and laws for environmental protection. The third is the
State Environmental Protection Agency (SEPA) of the State Council; it supervises
and administers the environmental protection laws throughout the country. The
local Environmental Protection Bureaus (EPB) at the province, municipality, and
city levels are directly under the SEPA. On September 15, 1987, the Law on Air
Pollution Prevention and Control of the People’s Republic of China (LAPPC) was
approved by the NPC. The law required that all plants that discharge pollutants
into the air must comply with the rulesforpollutioncontrol.After that, the Chinese
government published a series of policies and regulations for air quality protection
and establishedaset of nationalstandardsrelated to airquality,which are discussed
in detail later.
2. Establishment of a national air pollution monitoring system. Urban air pol-
lution monitoring started as early as the mid-1970s in China. Currently, more than
350 cities conduct routine urban air quality monitoring of the pollutants SO
2
, TSP,
and NO

x
. The 103 municipal atmospheric monitoring stations with 470 moni-
toring sites form China’s national air monitoring system (NAMS). In addition,
Beijing, Shenyang, Shanghai, Guangzhou, and Xian joined the Global Environ-
mental Monitoring System (GEMS). In the early 1980s, monitoring of acid rain
began, which mainly focuses on the urban districts in the south and southeast. The
National Acid Deposition Monitoring Net (NADMN)presentlyincludes113 mon-
itoring stations and 300 monitoring sites throughout the country. The monitoring
data are published in various ways such as the environmental statistical yearbooks,
annual reports of the environmental state, and weekly or daily air quality reports
(7, 8).
3.Implementationofresearchanddevelopmentprogramsfor urbanair pollution
control. The Chinese government initiated a series of research and development
programs involving studies analyzing urban atmospheric pollutants, atmospheric
modeling, environmental planning, development of advanced technologies, and
demonstration studies of urban air pollution control. Also, many international
organizations and foundations, such as United Nations Development Programme
(UNDP), U.S. Environmental Protection Agency (USEPA), World Bank, U.S.
Energy Foundation, and others, have provided financial and technological support
to help strengthen the capacity of Chinese experts and researchers to solve urban
air pollution challenges for themselves.
4. The investment in environmental infrastructure, including pollution control
devices, cleaner production technology, and natural gas pipelines.
These actions have prevented China’s urban atmospheric environment from de-
teriorating.Thisreviewdiscusses thecurrentstatus, characteristics, andprogressof
the urbanairpollutioncontrols in China, basedonthe results of theaforementioned
actions.
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URBAN AIR POLLUTION IN CHINA 401
OVERVIEW OF CURRENT URBAN AIR QUALITY STATUS

On October 1, 1996, the Chinese National Ambient Air Quality Standards
(CNAAQS, GB3095-1996) were published, which specify 10 air pollutant stan-
dards for SO
2
, TSP, PM
10
,NO
x
, nitrogen dioxide (NO
2
), CO, ozone (O
3
), Pb,
B[a]P, and F (Table 1). According to these standards, cities should meet Class II
of the CNAAQS, which is considered to be safe and acceptable (9).
At present, the urban air pollution in China, especially for northern cities, is
mainly from coal smoke with particles. According to the Report on the State of the
Environment inChina for2000, 62%ofthecitiesexceededClassIIoftheCNAAQS
for TSP and PM
10
concentrations. SO
2
pollution has improved somewhat with the
percentage of cities exceeding Class II of CNAAQS decreasing from 28% in 1999
to 22% in 2000. The NO
x
pollution level was relatively low in most cities except in
larger ones with better economic development and more vehicles, such as Beijing,
Guangzhou, and Shanghai, where the pollution is a mixture of coal smoke and
vehicle exhaust. Generally speaking, urban air quality in China is improving with

the percentage of cities meeting Class II of the CNAAQS increasing for over
300 cities as shown in Figure 2 (10).
During the ninth five-year plan (1995–2000), China focused on 47 sites as key
environmental protection areas (4 municipalities, 28 provincial cities, 15 special
economic regions, open coastal cities, and major tourist cities, which together
account for 40% of the total urban population and 60% of the total urban GDP).
The air quality data of cities is public information. Beginning in June 1997, many
large cities began to publish weekly air quality reports by using an air pollution
index (API) and an air quality level. In June 2000, daily air quality reportsreplaced
TABLE 1 Concentration limits for some pollutants in the
CNAAQS (mg/m
3
)
Pollutants Averaging time Class I Class II Class III
TSP Daily 0.12 0.3 0.5
Annual 0.08 0.2 0.3
PM
10
Daily 0.05 0.15 0.25
Annual 0.04 0.1 0.15
SO
2
Daily 0.05 0.15 0.25
Annual 0.02 0.06 0.1
NO
2
Daily 0.08 0.08 0.12
Annual 0.04 0.04 0.08
NO
x

Daily 0.1 0.1 0.15
Annual 0.05 0.05 0.1
CO Daily 4 4 6
O
3
Hourly 0.12 0.16 0.2
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Figure 2 Overview of urban air quality in China from 1998–2000.
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URBAN AIR POLLUTION IN CHINA 403
TABLE 2 Relationship of concentrations and subindex of some
pollutants (mg/m
3
)
Pollutant types
Subindex TSP PM
10
SO
2
NO
2
NO
x
O
3

50 0.12 0.05 0.05 0.04 0.05 0.06
100 0.3 0.15 0.15 0.08 0.10 0.12
200 0.5 0.25 0.25 0.12 0.15 0.20
300 0.625 0.42 1.6 0.565 0.565 0.40
400 0.875 0.5 2.1 0.75 0.75 0.50
500 1.0 0.6 2.62 0.94 0.94 0.60
weeklyreportsin 42 keyenvironmental protectionsites,and oneyearlater,daily air
quality predictions in 47 areas began to be reported to the public. These reports aid
environmental management by raising the public’s environmental consciousness.
In China, each pollutant reported has a subindex ranging from 0 to 500, with
50 corresponding approximately to Class I of the CNAAQS, 100 corresponding
to Class II, 200 corresponding to Class III, and 500 corresponding to significant
harmful effects. Table 2 gives the relationship of concentrations and subindexes
of some pollutants. Based on the ambient measurement results, the subindexes in
Table 2 are computed by using linear interpolation.
Initially, air quality reports for many Chinese cities published the levels of three
major pollutants, TSP, SO
2,
and NO
x
. Since February 2000, the air quality reports
for many cities listed the API value of PM
10
,NO
2
, and SO
2
; the first two of these
have been found to have more direct influence on public health than TSP and NO
x

.
However, air pollution reporting varies according to local governmentpolicies.For
example, Beijing reports CO and O
3
levels in addition to the other three pollutants.
For a city, the API of a week or day is the maximum of the subindexes of
pollutants reported, and the pollutant with the highest subindex is cited as the
major pollutant. A level and an assessment of the general air quality, based on the
reportedAPI,arealsoincludedintheairquality reports.The levelsand assessments
along with their associated API ranges are presented in Table 3.
Figure 3 summarizes the average monthly API values of eight regions in China,
based on the daily air quality reports of 42 key cities from June 5, 2000 to Septem-
ber 30, 2001 (11). Significant regional air quality differences are evident in China.
The most polluted cities were located in the northwest and north. The south-
central and northeast regions ranked third and fourth, followed by the east and
southwest. The cleanest region was the south followed by the southeast with the
API values of both almost always less than 100 all year. Urban air in northern
China was generally more polluted than in the south mainly due to the higher
particulate matter pollution levels in the north. There was also an obvious sea-
sonal variation in urban air quality. For all regions, summer and fall were the
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TABLE 3 Relationship of API ranges and air
quality level and assessment
Air quality
API ranges level Assessment

0–50 I Excellent
51–100 II Good
101–200 III Lightly polluted
201–300 IV Polluted
301–500 V Heavily polluted
cleanest seasons, due to fewer pollutants emitted during the warm months, better
atmospheric diffusion conditions, which can bring pollutants outside the ambient
air of the cities, and more precipitation, which helps to decrease the concentrations
of the atmospheric pollutants—especially particulate matters. After October, the
air quality of most cities began to deteriorate and pollution peaked in the winter.
In northern cities, bad air quality in the winter was probably because of the large
amount of coal burned for heating, which emited high levels of pollutants. The
winter peak was the sharpest for the northeast region where it is the coldest. In
February, the air quality improved some, but another pollution peak occurred in
March or April. The spring peak in northern cities was due to the sandstorms
from the west. The northwest region, which experienced the heaviest burden of
sandstorms, had the sharpest and highest spring peak.
Figure 4 shows the air quality level in each of 42 key cities from July 1, 2000 to
June 30, 2001. As shown in Figure 4a, during this statistical year, only about 30%
of the 42 key cities met the Level II air quality most of the time. In the Chinese
capital, Beijing, the pollution onmore than half of the 365daysexceeded the Level
III air quality as it did in other big cities, such as Tianjin and Chongqing. In the
northern cities of Lanzhou, Taiyuan, and Shijiazhuang, the air quality was so poor
that Level III was exceeded more than 75% of the year, and Level V pollution
frequently occurred. According to Figure 4b,PM
10
was the dominant pollutant in
most cities. SO
2
was the major pollutant in Chongqing and Guiyang and was a

concern in Shijiazhuang, Changsha, Qingdao, and other cities.
CHARACTERISTICS OF URBAN AIR POLLUTANTS
TSP
Measured by the frequency and degree of violations of the CNAAQS, TSP is the
mostsignificantair pollutantin Chinesecities.Inrecentdecades, thecharacteristics
of urban particles have changed. In the 1970s, cities were so severely polluted by
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URBAN AIR POLLUTION IN CHINA 405
Figure 5 Average annual urban TSP concentration in China from 1990–1999.
coal smoke that “rolling black smoke” was a common phrase to describe the air.
The emphasis on urban air pollution control at that time was smoke abatement
and dust removal, with boilers refitted and “nonblack smoke zones” established.
In the 1980s, improvements were seen with lower smoke and dust levels. In the
1990s, the control emphasis turned to the abatement of particles from residential
coal burning, with regulations requiring the use of briquettes and for optimization
of the residential fuel structure by using gas, electricity, and oil to replace coal.
As total energy consumption increased in recent years, the average urban TSP
concentration gradually declined, which illustrates progress in urban TSP control.
The average annual rate of decrease in the national average TSP concentrations
for over 70 cities was 4% during the 1990s, as shown in Figure 5. The rate of the
average TSP concentration decrease in 4 municipalities
1
and 24 provincial cities
(including 14 northern cities and 14 southern cities) was 3% (12).
As Figure 5 shows, the urban TSP concentration in the north was much higher
than in the south. This was due to many factors. The colder north burns much
more coal for winter heating, and its lack of vegetation and aridness give rise to
high concentrations of large-diameter, nonrespirable sand or loess soil particles
blown from the west each spring. The effects of these natural factors make control
of TSP pollution in northern cities difficult, so the TSP concentration in the north

is decreasing more slowly than in the south. Moreover, the north has more heavy
industry, which emits particulate matter.
1
Chongqing, which was removed from Sichuan Province and promoted to the status of a
provincial-level municipality in 1997, is reckoned in as a municipality.
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Figure 6 Average annual urban TSP concentrations in different sized cities in China
from 1990–1998.
The TSP concentrations in cities of different sizes
2
did not vary much. As
Figure 6 shows,
3
the average TSP concentrations in 12 largecitieswereonlyalittle
higher than in 12 medium and 12 small cities, with almost no difference between
medium and small cities. Therefore TSP air pollution is a national environmental
problem in China.
Because many effective measures have been implemented to reduce the particu-
late matters emittedfrom boilers, the contribution of coal smoke dust to urban TSP
has decreased. As the coal smoke pollution in urban air gradually decreased, some
nonpoint sources, such as soil, road particles, and construction dust contributed a
large percentage (13–15). Many modeling studies of the source apportionment of
urban TSP have been implemented in China, especially for the northern cities. In
the north, particulate soil matter has become the largest part of the TSP, with an
average level of 40% to 50% due to the dry climate and low level of forestation

in the area (16,17). Remote sources of soil particulates also contribute a lot to the
northern cities. During springtime, 20% of the TSP mass was from outside in Xian
city (18). Therefore, the TSP concentrations have remained high in northern cities
even after implementation of TSP control measures, and soil-dust control in the
north remains a challenge. During the northern heating period, the burning of coal
elevates the percentage of coal smoke dust in the urban TSP up to 30% to 40%.
The high share of coal smoke particles during the winter and the soil dust during
spring are common features of the TSP in the north but not in the south (19–22).
2
In this paper, large cites have population >1 million, medium cities are 0.5–1 million, and
small cities are <0.5 million.
3
For Figures 6 and 7, 12 large, 12 medium, and 12 small cities were chosen.
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URBAN AIR POLLUTION IN CHINA 407
PM
10
and PM
2.5
Particulate removal techniques currently in use in China are effective with coarser
particles but do not remove small particles very well; this has caused the TSP in
urban air to become finer and the PM
10
portion to grow. For example, in Beijing,
about 92% of the TSP in coal smoke dust is less than 10 microns (23). Not only
does PM
10
predominate among urban air particles, but concerns over its impact on
health have caused researchers and government officials to focus more attention
on it than ever. In 1996 the PM

10
standard was added to the CNAAQS, and in 2000
PM
10
replaced TSP in the air quality reports of many cities.
Fine particles contain a large component of organic and toxic materials and can
enter and remain in the human body more easily than coarse particles and affect
human health. These particles reducethevisibility in cities and influence daily life.
Theacidityandbuffer capacityofthe particlesalsoinfluences acid rain.TheUnited
States published an air quality standard for PM
2.5
in 1997, but in China only a few
research projects have analyzed urban PM
2.5
(24–26). According to these studies,
the PM
2.5
pollution level in Chinese cities is 1 to 5 times higher than the U.S.
standard of 65 µg/m
3
, and PM
2.5
is the largest portion of PM
10
, 50%–85% of the
total in terms of mass (Figure 7). The urban PM
2.5
concentration also varies with
seasons. For example, the PM
2.5

concentration in Beijing was highest during the
winter, decreased through the spring, and tended to be lowest during late spring
to early fall (24). The sources of PM
10
and PM
2.5
are much more complicated
than that of TSP. Human activity is the main source of fine particles in cities. For
PM
2.5
, the ratio of anthropogenic contribution to natural contribution was 10–15:1
Figure 7 PM
2.5
and PM
10
concentration in the cities Guangzhou, Wuhan, Lanzhou,
and Chongging in 1996.
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Figure 8 The chemical composition of PM
2.5
in terms of mass in Beijing from 1999–
2000.
but only 1:1 for TSP (27). Coal combustion and oil combustion (mostly from
vehicles) contributed 28% and 54% to PM
2.0

in the fall and 38% and 43% in the
winter in Beijing (28).
Figure 8 presents the chemical composition of PM
2.5
in terms of mass in
Beijing. Carbon was the main component due to the large contribution of coal
and oil consumption. The proportions of NH
+
4
,SO
2−
4
, and NO
−
3
were very high,
about 30%–40%, which indicates that the acidity of urban PM
2.5
is strongly in-
fluenced by secondary particles. Atmospheric NH
3
, as an important precursor to
secondary particles, reacts with SO
2
and NO
x
. According to studies of the ammo-
nia level in China, the biggest contributors are livestock (which contributes about
30%–60%) and the application of nitrogenous fertilizer (which contributes about
17%–47%) (29–32). The characteristics of these sources determine the tempo-

ral and spatial NH
3
distribution. The ammonia concentration in northern cities is
relatively high during the spring and summer farming period, while in southern
cities no obvious seasonal variation occurs because the farmland is worked during
all four seasons. In addition to NH
3
, the relative humidity, the temperature, and
the insolation are also important factors influencing the formation of secondary
particles. But the interactions between these factors are so complex and the meth-
ods used by researchers are so dissimilar that no uniform result is forthcoming.
In Beijing, some research has shown that the concentration of secondary particles
seems to be higher in the winter probably due to the high SO
2
emissions and low
wind speed at that time, which aid the formation of SO
2−
4
, and the low tempera-
ture, which assists the oxidation of NO
x
to NO
−
3
. Other research has shown that
summer has the highest secondary particle concentration—not winter—because
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URBAN AIR POLLUTION IN CHINA 409
of the large NH
3

emissions and sufficient temperature and humidity to ensure the
oxidation of SO
2
to SO
2−
4
(24, 30).
The enrichment by toxic materials, such as manganese, nickel, copper, zinc,
selenium, and lead, was substantially greater in PM
2.5
than in coarser particles,
which indicates that urban pollution sources provide a much larger contribution to
PM
2.5
. The lead concentration was fairly low in Beijing, largely below Class II of
the CNAAQS because leaded gasoline has been banned (24, 25).
SO
2
SO
2
is not only an important precursor of acid rain and secondary particles, but it
can also severely impair public health. As shown in Figure 9, SO
2
pollution was
very serious in the early 1990s. The concentration value has since dramatically
decreased at an annual rate of 6%. During the same period, the annual rate of
decrease in the average SO
2
concentration of 4 municipalities and 24 provincial
cities was 5%. The constant SO

2
concentration decrease shows that SO
2
pollution
is now well under control (12).
The geographical distribution of SO
2
pollution is somewhat different than the
TSP distribution. The SO
2
pollution level in northern cities is approximately the
same as in the south, but SO
2
concentration declined more rapidly in southern
cities. Figure 10 shows that the SO
2
pollution was extremely serious in large
cities, well above Class II of the CNAAQS, but SO
2
control measures have been
rapidly reducing the SO
2
concentration in them. For example, SO
2
concentration
in the heavily polluted cities of Guiyang, Chongqing, Qingdao, and HangZhou
was reduced by about 50% during the 1990s.
The SO
2
pollution in cities is a local environmental problem, which results

mainly from industrial production, energytransformation,andresidentialcooking.
Figure 9 Average annual urban SO
2
concentrations in China from 1990–1999.
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Figure 10 Average annual urbanSO
2
concentrations in cities of varied sizes in China
from 1990–1998.
Industry is a large SO
2
emission source, estimated to account for about half of
total SO
2
emissions in 1995. Energy transformation and residential cooking ac-
counted for about 36% and 9.3% of the emissions, respectively (Kebin He, unpub-
lished). Therefore, the cities in southwest China (a high-sulfur coal area), middle
and eastern China (an energy production base), and some areas of north China
(dominated by heavy industry), were seriously polluted. More than 85% of SO
2
comes from coal combustion in China, and the correlation coefficient between
increased SO
2
level and coal consumption was above 95%. Therefore, the key
to reducing SO

2
emissions is to control the SO
2
emitted from coal combustion
(33, 34).
Acid Rain
Acid rain was recognized as a potential environmental problem in China in the
late 1970s and early 1980s. In the early 1980s, acid rain primarily occurred in two
regions Chongqing-Guiyang and Nanchang. In the 1990s, the southeast coastal
area (Fuzhou, Xiamen, and Shanghai), the north coastal area around Qingdao in
Shandong Province, and the northeast area around Tumen in Jilin Province were
also identified as acid rain areas. Now, acid rain is mainly dispersed south of the
YangtseRiverand incoastal regions,includingmanysouthern citiesin Guangdong,
Guangxi, Sichuan, Guizhou, Yunnan, Hunan, Jiangxi, Fujian, Zhejiang, Jiangsu,
andAnhui, aswell astheShanghaiandChongqingMunicipality,and afewnorthern
cities such as Qingdao and Tumen. About 40% of China suffers from acid rain
pollution, Figure 11 (35–37).
SO
2−
4
,Ca
+
2
, and NH
+
4
are the dominant ions in acid rain, with the average
proportion of SO
2−
4

being 30%, Ca
2+
being 20%, and NH
+
4
being 17% in 1993.
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URBAN AIR POLLUTION IN CHINA 411
The ratio of the equivalent concentration of SO
2−
4
to that of NO
−
3
averages about
4–15, which is quite different from other acid rain areas in the world. In the United
States, Europe, and Japan, the SO
2−
4
to NO
−
3
contribution ratio is about 1–2.5. The
difference is mainly due to the large amount of coal consumed in China (38, 39).
The SO
2
level in acid rain is now decreasing so the average ratio of [SO
2−
4
]to

[NO
−
3
] is decreasing because of the SO
2
emission reduction measures and the
emission of more NO
x
from vehicles (40).
Acidrainhas beenobserved insouthern Chinabut notinmost ofnorthern China,
although there are stronger emissions of the precursors, SO
2
and NO
x,
in the north.
The difference may be due to the alkaline soils and meteorological conditions.
As stated earlier, the contribution of soil dust to urban particulate matter in the
north is larger than in the south. Furthermore, the northern soils are much more
alkaline, which neutralizes acidic ions such as SO
2−
4
and NO
−
3
in the rain. Higher
temperaturesandthe humidclimateinthesouth alsofacilitatetransformationof the
SO
2
and NO
x

to sulfate and nitrate. Goodatmospheric dispersion in the north helps
to mix and transport pollutant emissions over large areas (41). Simulations show
that the ratio of sulfur emissions to sulfur deposition is much less than 100% in
most northern cities, which indicates that some of the emitted SO
2
was transported
and deposited in other regions (40).
NO
x
The average NO
x
concentration in China did not vary much in the past decade and
was consistently under Class II of the CNAAQS (Figure 12). The average NO
x
concentration in the north was higher than in the south. For the whole country,
NO
x
pollution is relatively low, but some large cities face extremely serious NO
x
Figure 12 Average annual urban NO
x
concentrations in China from 1990–1999.
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Figure 13 Annual NO
x

concentrations in some large cities from 1990–1998.
levels. As Figure 13 shows, broadly speaking, the NO
x
concentration in these four
large cities gradually increased in the 1990s and greatly exceeded Class II of the
CNAAQS. In Guangzhou and Beijing, the NO
x
level even dramatically exceeded
theClassIIIstandard. Table4 also shows thatlargercitieshad higher NO
x
pollution
levels than smaller ones (42).
Vehicles are the main contributor to the urban NO
x
. Since the late 1970s, the
vehicle population in China has grown extremely rapidly, increasing about 10-fold
during the past two decades. By the end of 1998, the total number of vehicles had
reached about 40 million (including motorcycles). The increase is more obvious
in the large cities. In Beijing, the average growth rate was 17.4% in the 1990s with
TABLE 4 NO
x
pollution level in different size cities in China, 1994 and 1998
Average NO
x
concentration Excess over
Number of cities (mg/m
3
) Class II standard
City population
(city size) 1994 1998 1994 1998 1994 1998

>2.0 million 9 11 0.074 0.077 19.5% 81.82%
1.0–2.0 million 19 23 0.065 0.056 17.9% 52.17%
0.5–1.0 million 14 44 0.039 0.037 3.3% 11.36%
0.2–0.5 million 27 133 0.038 0.035 3.4% 13.53%
<0.2 million 16 111 0.031 0.030 1.3% 12.61%
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URBAN AIR POLLUTION IN CHINA 413
the vehicle population reaching 1.45 million in 1999. In Guangzhou, the num-
ber of vehicles reached 1.10 million in 1999 (43,44). However, road construction
has not been able to keep up with the significant increase in the number of ve-
hicles. In Guangzhou, the average growth rate of vehicle population was more
than 20%, but the growth rate of road length and road area was only 13%–14%
during 1990–1995 (45). Slow increases in transportation infrastructure greatly ex-
acerbated the vehicle emission problem. In Beijing and Guangzhou, the average
velocity of vehicles on main roads in the daytime is below 20 kilometers per hour
(46).
Vehicles not only emit large quantities of NO
x
, but they also produce large
amounts of carbon monoxide (CO) and volatile organic compounds (VOCs), both
of which are important pollutants in urban air. In Beijing, the NO
x
and CO emis-
sions from vehicles were 0.12 million tons and 1.3 million tons in 1998. Table 5
lists the percentage of emissions and pollutant concentrations due to vehicles in
three large cities (47–50). NO
x
, CO, and VOC concentrations were highest in the
dense traffic parts of the cities, especially during the rush hours. The emission
levelofNO

x
inside the second ring of Beijing was about four times that beyond
the fourth ring. (The second ring is closer to the center of the city than the fourth
ring.) In cities, two peak vehicle pollution levels occur during each day, one from
about 8:00–10:00 and theother from 15:00–17:00, which correspondto rush hours
(51, 52).
Theaverageemissionlevelsofnewdomestic vehiclesare3–10 timeshigherthan
that in developed countries due to lagging automotive manufacturing technology,
poor fuel quality, poor vehicle exhaust control, and lenient laws limiting vehi-
cle emissions. In addition, bad traffic management, poor maintenance, and slow
infrastructure development have exacerbated the emission problem, all of which
explain how a relatively small vehicle population can emit very large amounts of
pollutants in Chinese cities.
TABLE 5 Contribution of vehicles to emissions and concentration of urban
CO and NO
x
Item City Base year CO (%) NO
x
(%)
Emissions Beijing 1995 76.8 40.2
Emissions Beijing 1998 82.7 42.9
Emissions Guangzhou 1995 84.8 42.3
Emissions Shanghai 1995 76 44
Emissions Shanghai 1996 86 56
Concentration Beijing 1995 76.5 68.4
Concentration Beijing (city center) 1995 86.3 72.0
Concentration Guangzhou 1988 87 67
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O
3
and Photochemical Smog
The NO
x
and VOC emissions from vehicles can further react in the air and form
secondary pollutants such as O
3
and peroxyacetyl nitrate (PAN). The combina-
tion of these pollutants leads to the formation of photochemical smog, which is
strongly oxidizing and can seriously impair human health and the environment.
Besides the precursors, the formation of photochemical smog principally requires
ambient temperatures above 20 centigrade, wind speeds lower than 3 m/s, and
intense sunlight (53). So, at midday during the summer or early fall, if the mete-
orological conditions are right, photochemical smog will probably occur in cities
with abundant precursors. In the late 1970s, photochemical smog first appeared in
the Xigu petroleumindustry district in Lanzhou.In 1986, Beijing also experienced
photochemical smog in the summer. There the O
3
level gradually increasedlater in
the day exceeding Class II of the CNAAQS and increased from 188 in 1991 to 777
in 1999(54,55). More recently, somesoutherncities,especially coastal cities,have
faced the threat of photochemical smog in the summer. Shanghai, Guangzhou, and
Shenzhen have frequently experienced photochemical smog pollution. A signifi-
cant property of photochemical smog in China is the high ratio of NMHC to NO
x
,

which has an average value above 100, indicating that the O
3
formation is very
sensitive to the NO
x
concentration. Therefore, the NO
x
level must be controlled to
reduce the O
3
(53).
Indoor Pollutants
Energy used by households in the cities is an important component of China’s
energy consumption and is 7%–10% of the total commercial energy consumed in
recent years (4, 5). Space heating and cooking are the major energy uses in the
household. They account for 75% of the residential energy consumption in China,
with space heating dominating all other types of energy use in the home. Three
quarters of the floor area in urban residential buildings were heated by stoves with
efficiency oflessthan 10% (56, 57).Inthe1980s and the early1990s,coalprovided
more than 80% of the total urban residential energy and contributed significantly
to indoor air pollution. But the percentage hasbeendecliningwiththe proliferation
of gas fuel (including natural gas, coal gas, and liquefied petroleumgas), largely as
a result of government investments (Figure 14). In 1999, 80% of urban homes had
access to gas for cooking, and coal-burning households were increasingly turning
to the use of cleaner, more efficient briquettes (1).
A recent series of studies showed that indoor air pollution is very serious in
urban China. The research results in Shanghai and three other cities confirmed
the expected result that concentrations of inhalable particulates (IP), SO
2
,NO

2
,
and CO, in the homes using coal were much higher than in the homes consuming
gaseous fuel (Table 6). The difference between the SO
2
, IP, and CO concentrations
caused by the two types of fuel used could reach a multiple of more than 10 times
during the winter, although the NO
2
concentrations were somewhat higher in the
homes fueled by gas than those fueled by coal. The concentrations of pollutants in
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URBAN AIR POLLUTION IN CHINA 415
Figure 14 Urban residential energy consumption per capita in China from 1991–1999.
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TABLE 6 Changes in the average concentration of indoor pollutants by using different fuels
during the winter (mg/m
3
)
SO
2
NO
2
CO IP
Fuel Coal Gas Ratio Coal Gas Ratio Coal Gas Ratio Coal Gas Ratio

Taiyuan 0.283 0.166 1.7 0.101 0.622 0.2 5.91 7 0.8 1.173
a
0.386
a
3.0
(58)
Yinchuan 0.394 0.372 1.1 0.157 0.154 1.0 —
b
— — 0.853 0.372 2.3
(59)
Guangzhou 0.487 0.038 12.8 0.062 0.076 0.8 18.19 3.24 5.6 0.706 0.424 1.7
(60)
Chengde 0.482 0.163 3.0 0.068 0.084 0.8 7.39 4.69 1.6 0.665 0.209 3.2
(61)
Shenyang — — — — — — 7.46 4.69 1.6 0.651 0.355 1.8
(61)
Shanghai 0.86 0.065 13.2 0.1 0.04 2.5 14.07 3.45 4.1 0.384 0.148 2.6
(61)
Wuhan 0.173 0.07 2.5 0.094 0.115 0.8 3.46 4.83 0.7 0.291 0.204 1.4
(61)
a
Data are for TSP.
b
No data are available for the items with a dash.
kitchenswere muchhigherthanthoseinbedrooms.Withregardtodifferentkindsof
heatingsystems,separateones(withsmallcoalstoves)in individualresidenceunits
cause higher indoor pollution than central heating systems during the winter (57).
The residential cooking andheatingalsoemitsa great amount of polycyclicaro-
matic hydrocarbons (PAHs). Some studies investigated the composition of PAHs
and concluded that high indoorconcentrations of PAHs(2–30µg/m

3
) were mainly
caused by household cooking and heating activities, and a high concentration of
B[a]P (5–19 µg/m
3
) was mainly from smoking (62, 63).
Other important contributors to indoor air pollution are new building materials
and furnishings, which generally emit VOCs at a much higher rate than older
materials. Because of concerns about the health effects of VOCs, in 2002 the
Chinese government implemented 10 national standards for limitingtoxic subjects
in building materials and furnishings.
ECONOMIC DAMAGE
Estimates of economic losses from air pollution can provide useful information
for environmental policy making. Table 7 lists the direct economic losses of air
pollution accidents according to the China Environment Yearbook (12). These
statistical results are only a part of the economic losses caused byair pollution.The
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URBAN AIR POLLUTION IN CHINA 417
TABLE 7 Direct economic losses caused by air pollution accidents
[million renminbi (RMB)]
1993 1994 1995 1996 1997 1998 1999
Losses 98.7 17.0 13.0 8.6 13.0 7.5 8.2
total economic losses include health problems associated with urban air pollution
and indoor air pollution and damage to productivity, materials, agriculture, and
ecology.
Since the 1980s, many research projects studying economic damage from en-
vironmental pollution (including water pollution and air pollution) have been con-
ducted in China, but few were for urban air pollution. In 1984, a research project
conducted by SEPA, the Forecast and Countermeasures on China’s Environment
in 2000, was the first national study of environmental costs. After it, additional

valuable national research was conducted. Studies in this field have also been
conducted by foreign scholars. The estimates from seven studies are compared in
Table 8. The discrepancies among these authors arise because they use different
analytic methods and data.
TABLE 8 Comparison of studies on economic losses caused by air pollution
Base Economy losses GNP
Studies year (billion RMB) Research categories (%)
Guo & Zhang (64) 1983 12.4 2.2
Xia (65) 1992 57.9 Health, crops, animals, and 2.4
materials
Sun (66) 1992 60.5 2.5
Zheng et al. (67) 1995 30 Health damage due to TSP 0.5
pollution; crop, forest, and
materials damage due to
acid rain
Xu (68) 1993 39.1 Health, agriculture, acid rain, 1.1
household upkeep (cleaning)
Smil (69) 1990 15.1± 4.1 0.86 ± 0.16
World Bank (70) 1995 44.88 Health effects from urban air 7.1
(billion US$) pollution; damage from indoor
rural air pollution; crop, forest,
materials, and ecosystem damage
from acid rain; lead exposure for
children
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CONTROL PROGRESS AND PROSPECTS
SO
2
Pollution and Acid Rain Control
Because coal combustion makes the most significant contribution to SO
2
emission
and because SO
2
is the key precursor to acid rain, in China the control of SO
2
and
acid rain is focused on coal combustion.
POLICIES The Chinese government established a series of laws, regulations, and
standards to control SO
2
and acid rain. In 1995, articles on acid rain control were
first listed in the revised LAPPC, which required newly built thermal power plants
and other large or medium industrial furnaces that did not use low sulfur coal to
be equipped with desulfurization facilities and dust collectors or other preventive
measures. Other laws also referred to acid rain and SO
2
pollution control. The SO
2
emissions were included in the total emissions in the ninth five-year plan. National
standards were successively published to limit SO
2
emissions from power plants,
coke ovens, cement plants, and boilers.
In 1999, SEPA distributed the Control Objectives in Acid Rain Zones and SO

2
Pollution Control Zones in 1999, which required comprehensive protection plans
for the control of SO
2
in every prefecture and city in the Two Control Zones.
China began to experiment with levies on SO
2
in 1992 and expanded this
experiment in 1995. In April 1998, a notice was published by the SEPA, Notice
to Extend Areas for Trial Charges for SO
2
in the Acid Rain Control Zones and
SO
2
Pollution Control Zones (SEPA, 1998, No. 6), which regulated the standard
charge for SO
2
emissions to be 0.20 RMB/kg (71). The total revenue from the
pollution levies on SO
2
in power sector in 1997 amounted to 116 million RMB and
increased to347million RMB in1998.TheseleviesonSO
2
stimulated somepower
plants to control SO
2
emissions with installation of desulfurization equipment
and automatic monitoring systems. Data show that total SO
2
emissions declined

after the assessment increased for the release of SO
2
. However, the existing SO
2
emission levy system in China is not a very efficient way to control SO
2
pollution.
First, the amount charged is far lower than the abatement cost of SO
2
, so it could
not simulate the control of SO
2
emissions by power enterprises. For example, the
amount charged for SO
2
emissions within the Two Control Zones at present isonly
200 RMB/ton, whereas the average abatement cost is around 1100 RMB/ton (72).
Secondly, the Chinese government created a regulation that refunds 90% of the
SO
2
fees to the plants to be used for pollution mitigation. This allocation method
has seriously influenced the efficiency of revenue utilization. In addition, the actual
amount refunded is very low, for example, in 1998 the average refund was only
about 12%, much lower than 90%. Also, the part of the charge not refunded was
not used for SO
2
pollution control (73).
TECHNOLOGIES China also implemented many research and development pro-
grams for SO
2

emission control technologies. Coal washing technology has been
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URBAN AIR POLLUTION IN CHINA 419
actively investigated. By the end of 1997, more than 1500 coal washing facto-
ries and workshops were already built throughout the whole country. Coal gasi-
fication is divided into industrial and domestic gas. The design, manufacturing,
and operating techniques of the 80 kt/yr Texaco for synthesizing NH
3
, have been
mastered in China, and the Yilan and Lanzhou gasification projects successfully
introduced Lurgi oven technology with the productioncapacityof 1,600,000 m
3
/hr
and 540,000 m
3
/hr, respectively.
Inrecent years,industrialbriquettefactorieswere builtinseveralcitiesincluding
Chongqing, Luoyang, Guiyang, Beijing, and Taiyuan.Centralizedcoalmixingand
molding ahead of the boilers, developed on the basis of centralized molding, was
partially implemented in Lanzhou, Beijing, and Tianjin. In the early 1990s, China
began the study and development of circulating fluidized-bed combustion (CFBC)
boilers.Four phasesof theprogram havebeen completed.During thefirst phase,the
focuswasontheinvestigationanddevelopmentofsmallandmiddle sizedindustrial
fluidized-bed boilers, and there are now more than 3000 in operation throughout
the country. The second phase focused on developing circulating fluidized-bed
boilers suitable for thermal power plants, and currently there are approximately
68 MW units in operation. In the third phase combined gas and steam boilers
were developed. In 1994, a demonstration boiler with capacity of 35 t/hr was put
into operation. During the fourth phase, gas-steam combined circulating power
technology was developed based on fluidized-bed gasification and combustion,

and now a 15 MW unit is being demonstrated in the Jiawang power plant located
in Xuzhou city, Jiangsu province.
Research on flue gas desulfurization (FGD) in China started in the 1970s. As
early as the mid-1970s, a 2500 Nm
3
/hr pilot test of the wet limestone-gypsum pro-
cess was completed in the Zhabei power plant in Shanghai. During the sixth five-
year plan, a 5000 Nm
3
/hr pilot facility of active carbon vitriol was established
in Songmuping power plant in Hubei province. In the seventh five-year plan, a
5000 Nm
3
/hr pilot facility with a phosphate ammonium fertilizer process (PAFP)
was constructed in the Douba power plant in Sichuan, which achieved over 95%
efficiency in removing SO
2
. In addition, two spray drying pilot facilities of 50,000
Nm
3
/hr and 70,000 Nm
3
/hr were erected at the Shenyang Engine Manufacturing
CorporationandtheBaimapowerplant inSichuan. Fuxinbituminouscoalwithlow
sulfur content(0.97%)and Furong bituminouscoalwith high sulfurcontent(3.5%)
were burned separately, and both pilot facilities achieved over 80% efficiency
in removing SO
2
. During the eighth five-year plan, an industrial demonstration
facilityusing thecalciuminjectionprocesswasfinishedfor a20 t/hrstratifiedboiler

located in the Guizhou tire factory. In addition, during the seventh and eighth five-
year plans, some simplified combined dust collection and desulfurization facilities
were developed in succession in China; most of them used wet technology. Since
the early 1990s, several sets of advanced FGD systems have been introduced
into China in order to promote the progress of FGD industry, including the wet
limestone-gypsum, spray drying, electronic beam (EB), seawater, and limestone
injection into furnace and calcium oxide activation (LIFAC) systems. By the end
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TABLE 9 Desulfurization projects in China
Capacity Desulfurization Desulfurization Year
Plants (MW) technology efficiency (%) commissioned
Sichuan Baima 25 Rotary spray drying 80 1991
Chongqing Luohuang, 2× 360 Wet scrubbing 95 1993
(phase I) (single loop)
Shandong Huangdao 100 Rotary spray drying 70 1994
Dezhou Thermal 120 Drying injection 70 1995
Taiyuan Thermal 1 200 Wet scrubbing 80 1996
(simplified)
Fushun Power 120 Lime injection 40 1996
Sichuan Gaoba 100 High pressure CFBC 1996
Sichuan Neijiang 100 CFBC 90 1996
Chengdu Thermal 100 Electron beam 80 1997
Shenzhen West 300 Seawater >90 2000
Chongqing Power 2× 200 Wet scrubbing 95 2000
Zhejiang Banshan 2× 125 Wet scrubbing 95 2000

Beijing Thermal 1 2× 410 t/h CFBC 2000
Guiyang Power 50 Integration of
desulfurization and
dust removal
Chongqing Luohuang, 2× 360 Web scrubbing 80 1999
(phase II)
Nanjing Xiaguan 2 × 125 LIFAC >75 1999
of 2000, the total capacity of desulfurization units in operation or in construction
was approximately 4,000,000 kW.
Table9 summarizesthedesulfurization projectsinChina (74,75).On thewhole,
the desulfurization technologies in China are backward, and the installed capac-
ity generators equipped with desulfurization systems are rather small. Import of
desulfurization technologies is closely linked to international assistance projects.
Examples of international support follow. The semidrying rotary spray process
adopted by the Huangdao power plant in Shandong was a collaborative project
between the Nippon Electric Development Organization and the former Ministry
of Power Industry of China. In the expansion project of the Xiaguan power plant
in Jiangsu, LIFAC technology was imported from Finland. The simplified humid-
ifying process of the FGD project between China and Japan is part of the Japanese
Green Assistance Program for developing countries (74).
THE TWO CONTROL ZONES In early 1998, the State Council approved a map-
ping scheme for the Acid Rain Control Zone and the SO
2
Pollution Control Zone
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URBAN AIR POLLUTION IN CHINA 421
needed for the control programs. The Two Control Zone locations are shown in
Figure 15. The Control Zones include 175 cities and districts in 27 provinces, au-
tonomous regions, and municipalities accounting for 1.09 × 10
6

km
2
or 11.4%
of the country and 60% of the national SO
2
emissions. The Acid Rain Con-
trol Zone involves 14 provinces south of the Yangtze River with a total area of
0.806 million km
2
. The SO
2
Pollution Control Zone includes 63 cities and their
administrative counties with severe SO
2
pollution, which covers a total area of
0.29 million km
2
(76). The Two Control Zones are characterized by dense popula-
tion, developed industries, and large flourishing cities that are important to the na-
tionaleconomy.Manycomprehensiveprotection measureshavebeenimplemented
in these areas, including:
■
Local and sectional control planning.
■
Promotion of clean energy use. All districts promote the use of low-sulfur-
content coal and the replacement of coal with gas fuel. Among them, Beijing
and Shanghai have taken the lead to establish noncoal districts.
■
Closure of high-sulfur coal collieries. From 2000 to May 2001, 4492 high-
sulfur coal mines ceased production.

■
Closure of small factories with inefficient technology that caused serious
pollution. By the end of May 2001, 338 small power units, 784 product lines
in small cement and glass plants, 404 lines in iron and steel plants, and 1422
additional pollution sources closed, for a reduction of 81,368 kt/yr of SO
2
emissions.
■
Treatment of key pollution sources. To reduce SO
2
pollution, sources were
required to burn low sulfur coal, modify boilers and kilns, and treat efflu-
ent gas. From January to May of 2000, about 2100 treatment projects were
finished, for a reduction of 700,000 t/yr in SO
2
emissions.
These comprehensive measures have resulted in a much improved control of
acid rain and SO
2
pollution in the Two Control Zones. Among the 175 cities, the
number meeting the national ambient air SO
2
concentration standards has begun
to increase. In 1997, only 81 complied with the Class II standard of the CNAAQS,
the number increased to 93 in 1998 and 98 in 1999. SO
2
emissions decreased from
1,408,000 t/yr in 1997 to 1,254,000 t/yr in 1998 and to 1,114,000 t/yr in 1999.
PROSPECTS Currently, China is in a period of economic restructuring, and the
economic level is still relatively low. The SO

2
pollution control and acid rain
control plansmustbein accord with thenationaldevelopmentgoals.The near-term
objectives of urban SO
2
pollution control were to meet Class II of the CNAAQS for
SO
2
concentration in the ambient air of key cities by the year 2000. Twelve more
cities will be added to the group by 2005, and all cities within the Two Control
Zones are expected to meet the standards by 2010. The acid rain control goals are
to reduce acid rain pollution to the 1995 level by 2000, reduce it by 5%–10% more
before 2005, and lower it by an additional 10%–20% before 2010 relative to 1995.
China will reduce SO
2
emissions by limiting the production and use of high-sulfur