Air Pollution &
Health
Air Pollution Index (API)
Our air pollution problems
are related mainly to long-term health effects caused
by persistently high levels of tiny particles that can
penetrate deep into our lungs. However, our air pollution
levels sometimes can become so high that they may have
more immediate impacts for those with existing heart
or respiratory illnesses. In order to give public a
clean and simple picture of the air quality around us,
the Hong Kong Environmental Protection Department (EPD)
designed a simple way of indicating air quality, namely
Air Pollution Index (API).
The API is a simple way of describing
air pollution levels to provide timely information about
air pollution to the public and to enhance awareness.
Since June 1995, the EPD has been reporting the API
and making a forecast for the following day. Similar
systems are widely used in many other places such as
the United States, Singapore, Malaysia, Taiwan and the
Philippines.
The API forecast serves as an alert
to the public before the onset of serious air pollution
episodes. It helps the general public, especially susceptible
groups such as those with heart or respiratory illnesses,
to consider taking precautionary measures when necessary.
The API ranges from 0 to 500
and is divided into 5 bands according to the potential
effects on health. An API number of 100 is particularly
important since it indicate to the short-term air quality
in Hong Kong. An API higher than 100 means that one
or more pollutants may pose immediate health effects
to some susceptible members of our community.
The potential
health effects for different ranges of API
values are as follows: |
Air Pollution
Level |
API |
Health Implication |
Severe |
 |
201 to 500 |
People with
existing heart or respiratory illnesses may
experience significant aggravation of their
symptoms and there may be also widespread
symptoms in the healthy population. These
include eye irritation, wheezing, coughing,
phlegm and sore |
Very High |
|
101 to 200 |
People with
existing heart or respiratory illnesses may
notice mild aggravation of their health conditions.
Generally healthy individuals may also notice
some discomfort. |
High |
|
51 to 100 |
Very few people,
if any, may notice immediate health effects.
Long-term effects may, however, be observed
if you are exposed to such levels for a long
time. |
Medium |
|
26 to 50 |
None expected
for the general population. |
Low |
|
0 to 25 |
None expected. |
|
The suggested
precautionary actions are summarised below: |
Air Pollution
Level |
API |
Advice to
You |
Severe |
 |
201 to 500 |
The general
public are advised to reduce physical exertion
and outdoor activities |
Very High |
|
101 to 200 |
Persons with
existing heart or respiratory illnesses (such
as coronary heart and cardiovascular diseases,
asthma, chronic bronchitis and chronic obstructive
airways diseases) are advised to reduce physical
exertion and outdoor activities |
High |
|
51 to 100 |
No immediate
response action is suggested -- Long-term
effects may, however, be observed if exposed
at this level persistently for months or years |
Medium |
|
26 to 50 |
No response
action is required. |
Low |
|
0 to 25 |
No response
action is required. |
|
You can visit EPD's website for
more details (www.epd.gov.hk)
Typical Air Pollutants around You
The
air we breathe can be contaminated with pollutants from
factories, vehicles, power plants, and many other sources.
These pollutants have long been a major concern because
of the harmful effects they sometimes have on people's
health and the environment. Their impact depends on
many factors, including the quantity of air pollution
to which people are exposed, the duration of the exposures,
and the potency of the pollutants. The effects of air
pollutants can be minor and reversible (such as eye
irritation) or debilitating (such as aggravation of
asthma) and even fatal (such as cancer).
Air pollutants are those pollutants
that are known or suspected to cause cancer or other
serious health effects, such as reproductive effects
or birth defects, or to cause adverse environmental
effects. The degree to which a toxic air pollutant affects
a person's health depends on many factors, including
the quantity of pollutant the person is exposed to,
the duration and frequency of exposures, the toxicity
of the chemical, and the person's state of health and
susceptibility.
Typical there are six common air
pollutants, they are sulphur dioxide (SO2), carbon monoxide
(CO), ozone (O3), nitrogen dioxide (NO2), Volatile Organic
Compounds (VOCs) and suspended particulate (SP),
Gaseous Pollutants
- Sulphur Dioxide
- Carbon Monoxide
- Nitrogen Dioxide
- Ground-level Ozone
- Volatile Organic Compounds
(VOCs)
Particulates Pollutants
- Particulate matter (Total
and Respirable Particulates)
Sulphur Dioxide
Sulfur dioxide, or SO2, belongs to the family of sulfur
oxide gases (SOx). These gases dissolve easily in water.
SOx gases are formed when fuel containing sulfur, such
as coal and oil, is burned. SO2 dissolves in water vapor
to form acid, and interacts with other gases and particles
in the air to form sulfates and other products that
can be harmful to people and their environment.
Health and Environmental Impacts
Respiratory Effects from Gaseous SO2 - Peak levels of
SO2 in the air can cause temporary breathing difficulty
for people with asthma who are active outdoors. Longer-term
exposures to high levels of SO2 gas and particles cause
respiratory illness and aggravate existing heart disease.
Respiratory Effects from Sulfate
Particles - SO2 reacts with other chemicals in the air
to form tiny sulfate particles. When these are breathed,
they gather in the lungs and are associated with increased
respiratory symptoms and disease, difficulty in breathing,
and premature death.
Visibility Impairment - Haze occurs
when light is scattered or absorbed by particles and
gases in the air. Sulfate particles are the major cause
of reduced visibility in many parts of the U.S., including
our national parks.
Acid Rain - SO2 and nitrogen
oxides react with other substances in the air to form
acids, which fall to earth as rain, fog, snow, or dry
particles. Some may be carried by the wind for hundreds
of miles.
Carbon monoxide
Carbon monoxide, or CO, is a colorless, odorless gas
that is formed when carbon in fuel is not burned completely.
It is a component of motor vehicle exhaust, they are
also coming from other non-road engines and vehicles.
Higher levels of CO generally occur in areas with heavy
traffic congestion and other heavy industrial areas.
Health and Environmental Impacts
Cardiovascular Effects - The health threat from lower
levels of CO is most serious for those who suffer from
heart disease, like angina, clogged arteries, or congestive
heart failure. For a person with heart disease, a single
exposure to CO at low levels may cause chest pain and
reduce that person's ability to exercise; repeated exposures
may contribute to other cardiovascular effects.
Central Nervous System Effects -
Even healthy people can be affected by high levels of
CO. People who breathe high levels of CO can develop
vision problems, reduced ability to work or learn, reduced
manual dexterity, and difficulty performing complex
tasks. At extremely high levels, CO is poisonous and
can cause death.
Smog - CO contributes to the formation
of smog ground-level ozone, which can trigger serious
respiratory problems.
Nitrogen oxides
Nitrogen oxides, or NOx, is the generic term for a group
of highly reactive gases, all of which contain nitrogen
and oxygen in varying amounts. Nitrogen oxides form
when fuel is burned at high temperatures, as in a combustion
process. The primary manmade sources of NOx are motor
vehicles, electric utilities, and other industrial,
commercial, and residential sources that burn fuels.
NOx can also be formed naturally.
Health and Environmental Impacts
Ground-level Ozone (Smog) - is formed when NOx and volatile
organic compounds (VOCs) react in the presence of sunlight.
Children, people with lung diseases such as asthma,
and people who work or exercise outside are susceptible
to adverse effects such as damage to lung tissue and
reduction in lung function.
Acid Rain - NOx and sulfur dioxide
react with other substances in the air to form acids
which fall to earth as rain, fog, snow or dry particles.
Some may be carried by wind for hundreds of miles. Acid
rain damages; causes deterioration of cars, buildings
and historical monuments; and causes lakes and streams
to become acidic and unsuitable for many fish.
Global Warming - is also a greenhouse
gas. It accumulates in the atmosphere with other greenhouse
gasses causing a gradual rise in the earth's temperature.
This will lead to increased risks to human health, a
rise in the sea level, and other adverse changes to
plant and animal habitat.
Ground-level Ozone
Ozone (O3) is not usually emitted directly into the
air, but at ground level is created by a chemical reaction
between oxides of nitrogen (NOx) and volatile organic
compounds (VOC) in the presence of sunlight. Motor vehicle
exhaust and industrial emissions, gasoline vapors, and
chemical solvents as well as natural sources emit NOx
and VOC, that help to form ozone. Sunlight and hot weather
cause ground-level ozone to form in harmful concentrations
in the air.
Health Impacts
Ozone can irritate lung airways and cause inflammation
much like a sunburn. Other symptoms include wheezing,
coughing, pain when taking a deep breath, and breathing
difficulties during exercise or outdoor activities.
People with respiratory problems are most vulnerable,
but even healthy people that are active outdoors can
be affected when ozone levels are high.
Even at very low levels, ground-level
ozone triggers a variety of health problems including
aggravated asthma, reduced lung capacity, and increased
susceptibility to respiratory illnesses like pneumonia
and bronchitis.
Volatile Organic Compounds (VOCs)
Volatile organic chemicals (VOCs) are emitted as gases
from certain solids or liquids which contain organic
compounds. In many household products, VOCs is found
to be a common ingredient. Paints, varnishes, and wax
all contain organic solvents, as do many cleaning, disinfecting,
cosmetic, degreasing, and hobby products. Fuels are
made up of organic chemicals. All of these products
can release organic compounds while you are using them,
and, to some degree, when they are stored. When these
organic compound released to atmosphere, they become
VOCs and a key contributor of smog formation.
Health Impacts
VOCs can have direct effects on eye, nose, and throat
irritation; headaches, loss of coordination, nausea;
damage to liver, kidney, and central nervous system.
Some organics can cause cancer in animals; some are
suspected or known to cause cancer in humans.
The ability of organic chemicals
to cause health effects varies greatly from those that
are highly toxic, to those with no known health effect.
As with other pollutants, the extent and nature of the
health effect will depend on many factors including
level of exposure and length of time exposed. Eye and
respiratory tract irritation, headaches, dizziness,
visual disorders, and memory impairment are among the
immediate symptoms that some people have experienced
soon after exposure to some organics.
Smog is sometimes called photochemical
smog or photochemical air pollution. One of smog's key
ingredients is formed when volatile organic compounds
(VOCs) react with ozone in the presence of sunlight.
A simple chemical formula for this reaction would be:
1) O3 + VOC + light --> oxidized
organic compounds
The oxidized organic compounds then
mix with many other compounds and small particles in
the air to create smog:
2) oxidized organic compounds + many
other compounds --> photochemical smog
Humans feel the effects of smog most
often by experiencing respiratory trouble. Although
the exact degree of health effects of smog is unknown,
lung function and breathing can certainly be affected.
Smog is also hazardous because it decreases visibility.
Particulate matter (Total and Respirable Particulates)
Particulate matter, or PM, is the term for particles
found in the air, including dust, dirt, soot, smoke,
and liquid droplets. Particles can be suspended in the
air for long periods of time. Some particles are large
or dark enough to be seen as soot or smoke. Others are
so small that individually they can only be detected
with an electron microscope.
Some particles are directly emitted
into the air. They come from a variety of sources such
as cars, trucks, buses, factories, construction sites,
tilled fields, unpaved roads, stone crushing, and burning
of wood.
The difference between total and
respirable particulates is their size. Size of respirable
particulates is so small that they can be breathed directly
into our lung, but total particulates cover both respirable
and non-respirable particulates.
Health Impacts
Many scientific studies have linked
breathing PM to a series of significant health problems,
including:
- aggravated asthma
- increases in respiratory symptoms
like coughing and difficult or painful breathing
- chronic bronchitis
- decreased lung function
- premature death
Visibility impairment - PM is the
major cause of reduced visibility (haze)
|