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Tool 7 - Human Health Effects of Common Air Pollutants
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 could suffice.
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
| Pollutant | Human Health Effects | Other Effects |
| Carbon Monoxide |
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 and death. |
No adverse effects are known |
| Oxides of Nitrogen (NOx and NO2) | 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. |
Corrodes stonework 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 reduces visibility |
| Ozone (O3) |
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 effect agriculture. Smog can cause reduced visibility. |
| Hydrocarbons | 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 |
| Polyaromatic Hydrocarbons (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 |
| Benzene (C6H6) | 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 and death. | Harmful for plants |
| Lead (Pb) |
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). |
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| 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. |
Corrodes stonework Ingredient in acid rain (acid aerosols) which can damage wildlife, trees and lakes. Acid aerosols can reduce visibility. |
| Suspended Particulate Matter (SPM) | 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 Reduces visibility. |
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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 most harmful |
Increased cardio-respiratory mortality-particularly in combination with SO2. Increased cardio-respiratory mortality no observable threshold. Some constituents of fine particulate matter, such as diesel smoke, are carcinogenic |
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.