Tool 7 - Human Health Effects of Common
This tool specifically concentrates on the human health effects of major
pollutants. It is intended to assist the Working Groups in understanding
the danger of each pollutant, identifying and prioritizing hazardous pollutants
within their own cities, and initiating actions to curb them
While there are many pollutants, it is generally sufficient to focus
air quality management on the major pollutants mentioned in the Table
below. Some of these pollutants cause acute health effects after short
or longterm exposure while others have chronic effects after long (chronic)
periods of exposure.
Acute effects occur when the concentration of a pollutant is above the
prescribed level for a short period of time. Carbon monoxide (CO) is a
well-known example of a pollutant that causes acute effects. It reduces
the oxygen carrying capacity of the blood. People may immediately die
when exposed to very high CO concentrations. High CO concentrations can
occur in isolated rooms with badly maintained gas heaters. The one-hour,
mean concentrations of pollutants (that cause acute effects) should not
exceed prescribed levels. If information on hourly concentrations is not
available, the information on the 24-hour mean or the 8-hour mean concentrations
In case of pollutants causing long-term effects (such as cancer or asthma),
annual mean concentrations should not exceed the prescribed levels. These
levels can be found in the WHO air quality standards TOOL
6. Dust (SPM) is a classic example of a pollutant with long-term effects.
It affects human health in the most serious way because it causes breathing
problems and asthma. The extent of illnesses depends upon the size and
chemical composition of the particulate matter. The smallest particles
are the worst because they are the inhalable, thoracic fraction of SPM.
This fraction is called the PM 10 fraction, meaning that the particles
are 10 micrometre or less in diameter. In practice, dust emitted by diesel
motor vehicles is worse than the same amount of dust from the desert,
because diesel emissions contain a large percentage of small particles.
Alone in Europe, particulate matter is estimated to cause more then 200'000
deaths per year.
Table 7.1 Human Health Effects of Pollutants
||Human Health Effects
Reduces oxygen carrying capacity of the blood by combining with
hemoglobin. Results depend on severity of exposure and can include
mild headaches, dizziness, tiredness, nausea, loss of consciousness
|No adverse effects are known
|Oxides of Nitrogen (NOx
Sensitizes the lungs to other pollutants
and allergens and has a range of effects on the lung function (especially
from indoor exposure) including asthma. Respiratory irritant.
An ingredient in acid rain (acid aerosols) which can damage trees
and lakes and reduce visibility
A major component of photochemical smog that affects health and
Powerful oxidant reacting with most biological substances.
A lung irritant and sensitizer to other pollutants and allergens,
can reduce lung function and do permanent damage to lungs. Can inhibit
immune system response.
Can produce teary eyes and sore throats.
Attacks paints, elastomers, and rubbers.
Can damage plants and trees. Can reduce the growth of plants and
Smog can cause reduced visibility.
||Potential carcinogenic effects. Many
hydrocarbons formed from incomplete combustion of fuels are human
toxins, are reproductive hazards and can cause morbidity or even death
in prolonged exposure.
||Some, such as formaldehyde and ethylene
may harm plants
(PAHs), notably benzo(a)pyrene(BaP)
Benzo(a)pyrene and certain other species are carcinogenic. Short
term hazards include red blood cell damage, leading to anemia; suppressed
immune system. Reproductive and organ (liver, kidney and skin) damage
have also been reported in laboratory tests.
PAH related human health problems occur via inhalation and via
consumption of food polluted due to atmospheric deposition.
|Harmful for plants
||Powerful carcinogen linked
to leukemia. Causes harmful effects on the bone marrow and can cause
a decrease in red blood cells leading to anemia. Short-term exposure
to high levels of benzene can cause drowsiness, dizziness, unconsciousness
||Harmful for plants
Neurotoxin, impairment to cognitive development - reduces IQ levels-,
especially in children. Causes brain and nervous system damage.
Affects capacity to concentrate and memorize.
Affects blood biochemistry and can raise blood pressure. Impairs
production of hemoglobin in blood.
Lead related human health problems occur via inhalation, via consumption
of food polluted due to atmospheric deposition (for example agricultural
activities near main roads) and through contact with lead containing
substances (such as paint).
|Sulfur Dioxide (SO2)
Narrows the airways, particularly in sensitive individuals, producing
symptoms ranging from coughing and wheezing to bronchitis and asthma.
Increased prevalence to chronic bronchitis and permanent lung damage.
Ingredient in acid rain (acid aerosols) which can damage wildlife,
trees and lakes.
Acid aerosols can reduce visibility.
|Suspended Particulate Matter
||Affects the airways, strongly dependent
on size and chemical composition; the small fraction of 10 micrograms
and smaller (so called PM10 - see below)
is the most harmful as it can penetrate deep into the lungs. It is
especially the very fine parts, PM2.5, that
are most harmful.
Ashes, smokes, and dusts can dirty and discolor structures and
other property including clothes and furniture, speed their deterioration
PM10 (part of SPM and refers to those
particles with a diameter equal to or smaller than 10 micrometre)
This is the inhalable, thoracic fraction of SPM. Often seen as
the most serious pollutant.
The smallest particles, PM2.5, are the
Increased cardio-respiratory mortality-particularly in combination
Increased cardio-respiratory mortality no observable threshold.
Some constituents of fine particulate matter, such as diesel smoke,
|Same as SPM
Additional information can be obtained from:
- The report "Air Quality Management and Assessment Capabilities
in 20 Major Cities (UNEP/WHO 96);
- The Air Guide, Chapter 3, included as a word file in the ISIS'97 CD
ROM; developed by the WHO etc.
- "Phasing Out Lead from Gasoline: World - Wide Experience and
Policy Implications, The World Bank 1996
- At the national level: Ministries of Health, hospitals, public health
officials, statistics departments, motor vehicle registration.