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SECTION
5 ASSIMILATIVE CAPACITY CAPITAL STOCK
| 5.4 |
Assimilative
Capacity of Air (including Noise) |
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| 5.4.3 |
Impacts
and Resource Constraints |
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| 5.4.3.1 |
Air
pollution problems in Hong Kong are largely
a function of both substantial local emission
sources, such as vehicles and power plants,
and seasonally varying trans-boundary pollution
transfers. Regional movements of pollutants
in the atmosphere, in particular from the
Pearl River Delta region, have an impact
on ambient pollution levels in Hong Kong
which tend to be elevated during the winter
months when northerly winds prevail. For
example, air quality data for 1995 (China
Environment Yearbook) suggest that concentrations
of SO2 in Guangzhou are 2-3 times those
of Hong Kong levels and TSP concentrations
are around twice those of the SAR. These
higher levels of pollution can be attributed
to the greater use of coal, higher sulphur
content in fuel and significant levels of
pollution from the growing source of road
vehicles. Indeed, it has been reported that
as a result of increasing volumes of traffic,
ambient concentrations of nitrogen dioxide
in Shenzhen and Guangzhou are increasing
by 20% and 10% respectively per annum and
particulates are estimated to be increasing
by 15% per annum principally due to industrial
activity (Plan D 1993b).
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| 5.4.3.2 |
In
Hong Kong whilst ambient levels of SO2 and
lead have declined in recent years and are
now of less concern for air quality, trends
in the data show that TSP, RSP and NO2 are
the major contributors to air quality problems
in Hong Kong. These three pollutants show
a historical pattern of non-compliance with
AQOs in a number of locations and if recent
trends are sustained, breaches at additional
sites are predicted within the next few
years (Territory Wide Air Quality Modelling
Study). In addition, whilst there were no
breaches of AQOs for ozone in 1998, there
were two exceedences in 1996 and annual
average levels have steadily increased in
the last 8 years. The trend of increased
ozone levels and more frequent violations
of the hourly ozone limit, suggests that
photochemical pollution is likely to be
of increasing concern in Hong Kong. Problems
of urban smog formation are already evident
through reduced visibility in the territory
on many days in the year.
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| 5.4.3.3 |
The
data on air pollution therefore suggest
that the air in many urban parts of Hong
Kong may be approaching the natural assimilative
capacity, although further study would be
needed to quantify such capacity. A number
of air pollution hotspots can also be identified
in the densest parts of Kowloon and Hong
Kong Island. A significant proportion of
the criteria and toxic air pollutants of
concern are emitted by road vehicles and
this source can be identified as the sector
contributing most significantly to the decline
in assimilative capacity, and to these hotspot
areas. The local and territory-wide effects
of road traffic emissions on air quality
are presently of concern and are predicted
to be the single most important source of
air quality problems in future planning
horizons. Air quality predictions undertaken
by ERM using the PATH model for CTS-3 (WSA
1999) have indicated that air pollution
will continue to increase in future years
without further control measures.
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| 5.4.3.4 |
A
measurable impact arising from declining air
quality has been manifested in a high incidence
of respiratory problems among the urban population.
The most significant air pollutant in terms
of its effects on the human respiratory function
is RSP, or Respirable Suspended Particulates.
These are very small particulate matter (not
exceeding 10 um in diameter and thus often
referred to as PM10) which are inhaled into
the lungs and which often remain attached
to lung tissue (particularly the smaller particles
less than 2.5 um wide). These particles can
result in damage to lung tissue causing long
term disorders of the pulmonary functions,
increased infant mortality and lung cancer.
The effects are most marked as a result of
long term exposure to RSP, of which the principal
source in Hong Kong is road transport emissions,
particularly from diesel engined vehicles
which account for nearly 70% of vehicle kilometres
travelled (HKSARG 1999). Those groups which
appear to be most sensitive to the effects
of RSP include individuals with chronic lung
and heart disease, individuals with influenza
and asthma and elderly people and children.
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| 5.4.3.5 |
The
data suggest a trend that respiratory disease
is increasing in significance as a cause of
ill health and mortality in Hong Kong. Although
influences such as the prevalence of smoking
should be accounted for in interpreting health
data, recent data from the Department of Heath
(DoH 1998) shows that overall smoking prevalence
among the population continues to decline.
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| 5.4.3.6 |
The
incidence of excessive noise, particularly
from transport sources, is also widespread
in Hong Kong with around 1 million people
affected. Where noise levels are significant
enough to cause disturbance to people through,
for example, sleep loss, speech disturbance,
intrusion in offices and homes and even occupational
health impacts, then they must be considered
in any assessment of sustainability. Mitigation
of noise needs to be considered according
to the location, existing noise climate, predicted
noise impact and sensitivity of the receiving
environment. Noise is also controlled by EPD
who enforce the Noise Control Ordinance (Cap
400) to control levels of noise from construction
works and industrial installations. Opportunities
to design out noise are usually afforded during
new construction (eg through insulation of
buildings or by design of transport infrastructure
to minimise noise impact on surrounding receivers).
However, it is only in the long term as land
uses change significantly that the widespread
incidence of excessive noise levels can be
addressed through re-housing. Exposure to
excessive noise levels will remain a problem
unless significant changes to the patterns
and flows of road traffic (the source) are
effected. |
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