Tuesday, 14 June 2016


Air Pollution is the introduction of particulates, biological molecules or other harmful substances, at higher concentrations into the atmosphere and consequently posing a threat to the health of humans, animals and plants after continuous and long period of exposure.

Air Pollutant is a substance in the air that can have adverse effects on humans and ecosystems. Air pollutants are either introduced into the atmosphere naturally or facilitated by humans through various means. Air pollutants are classified either as:

-          Primary Air Pollutants; or
-          Secondary Air Pollutants.

Primary Pollutants are introduced directly into the atmosphere while Secondary Pollutants are formed in the air as primary pollutants react or interact. Primary pollutants include:
-          sulfur oxides;
-          nitrogen oxides;
-          carbon oxides;
-          volatile organic compounds;
-          particulate matter;
-          free radicals; and
-          toxic metals such as methyl mercury, odours,  chlorofluorocarbons, ammonia and radioactive pollutants.

Secondary Air Pollutants majorly include photochemical smog and ground level ozone and peroxyacetyl nitrate (PAN) both from nitrogen oxides and volatile organic compounds.

Dispersal of air pollutants is affected by Thermal Inversion, Wind Dispersion and “Grasshopper effect”.

Thermal Inversion occurs when a stable layer of warm air overlays cool air, and consequently:
a)      reversing the normal temperature decline with increasing height;
b)      preventing Convection Currents from dispersing pollutants, thus limiting dilution of air pollutants.

Wind also facilitates dilution of air pollutants by evenly dispersing them, which then reduces higher concentrations in certain areas.

Grasshopper Effect Principle is whereby volatile organic compounds evaporate from warmer areas then condense and precipitate in the cooler areas.

Anthropogenic sources of air pollution include:
1.      Combustion of coal, oil and oil products in industries and poorly maintained motor vehicles which release nitrogen oxides and sulfur oxides into the atmosphere;
2.      Electric power generation releases nitrogen oxides into the atmosphere;
3.      Use of aerosols and smoking release particulate matter into the atmosphere;
4.      Construction also release particulate matter into the atmosphere from the cement used and also asbestos fibers (serpentine and amphiboles) from breaking of asbestos used for roofing;
5.      Strip Mining and Rock Crushing release particulate matter into the atmosphere as dust;
6.      Leaks around industrial valves and pipes release volatile organic compounds and toxic metals into the atmosphere;
7.      Open combustion of solid wastes also pollutes the air; and
8.      Combustion of mined fuels releases heavy metals into the atmosphere such as leaded gasoline which release lead during combustion.

Natural sources of air pollution include volcanic eruptions that release ash, crystalline silica, acid mists, pyroclasts and hydrogen sulfide, plants that release volatile organic compounds (Terpenes and Isoprenes), Dust Storms which cause wind erosion and swamps and dairy animals that are responsible for 66% of the atmospheric methane.

Air pollution is a great challenge facing both developing and underdeveloped countries due to inadequate finances, technology, policies and framework that hinder air pollution control. Pollution has several detrimental effects to health of humans, animals and plants, that is, the ecosystem as a whole.

Sulfuric (IV) Oxide is oxidized in the air to form Sulfur Trioxide, which then reacts with water to form Sulfuric Acid which leads to acid rain.  Acid Rain corrodes iron sheets and other metallic structures and also causes lung damage from acidic sulfate ions. Acid rain also lowers the soil’s pH which in turn reduces the bioavailability of essential nutrients to plants and mobilizes heavy metals such as lead, arsenic into the groundwater through catalyzing weathering in the respective bearing rocks.

Nitrogen Oxide is oxidized to Nitrogen Dioxide, which then reacts with water to form Acid Rain which leads to Eutrophication in aquatic ecosystems. This then causes Algal Blooms and thus lowering dissolved oxygen in aquatic ecosystems which further leads to death of aquatic life forms through suffocation and also provides conducive conditions for incubation of disease-causing micro-organisms. Nitrogen Oxide (N2O) also absorbs ultraviolet rays modifying the climate.

Carbon Oxides cause global warming by permitting maximum absorption of the incoming short-wave solar radiation on the earth and permitting minimum emission into the atmosphere which is indirectly heated, thus leading to rise in atmospheric temperatures.

Carbon Monoxide also combines with hemoglobin to form carboxyhemoglobin since hemoglobin has a high affinity for carbon monoxide than oxygen thereby causing suffocation which leads to vertigo, fainting, cardiovascular problems, collapse of respiratory system and death. Particulate matter reduces air visibility and leaves dirty deposits on windows, painted surfaces and textiles.

Respirable particulatessmaller than 2.5 micrometers such as crystalline silica cause damage to respiratory tissues when inhaled. Asbestos fibers and cigarette smoke are very dangerous when inhaled since they are carcinogenic in nature.
Diesel Fumes are also highly toxic since they contain benzene, dioxins and mercury which pose a great threat to the health of humans and animals.

Lead from leaded gasoline is a metabolic poison and neurotoxin.

Mercury (Methyl Mercury) emitted by volcanoes, smoke stacks, power plants and medical incinerators is extremely toxic and kills the brain cells.

Photochemical Smog formed by the reaction of nitrogen oxides and hydrocarbons in the presence of ultraviolet radiation is a strong oxidizing agent which damages vegetation, building materials and sensitive tissues such as the eyes and lungs. It however forms the ozone layer which protects the earth from direct ultraviolet rays which are harmful to humans, animals and plants. Persistent inhalation of irritant air pollutants causes mucus buildup, painful cough and involuntary muscle spasms that constrict airways thus causing bronchitis.


Air pollution has adverse effects and should therefore be limited or eradicated by all means in order to protect humans, animals and plants that are all dependent on air for survival. Air pollution can be reduced through switching to clean energy sources (such as solar energy, wind energy, nuclear energy and tidal energy) and abandoning coal and fossil fuels that pollute the atmosphere immensely.

Developing better public transportation systems that reduce the emissions from associated transport means to minimum quantities possible can also lead to reduction in air pollution.
Modern technology such as electrostatic precipitators, baghouses, cyclones, scrubbers and catalytic converters can also be used in cleaning of emissions released through the smoke stacks.

Planting trees remains one of the surest ways of reducing the level of carbon oxides concentrations in the atmosphere as plants absorb carbon dioxide during photosynthesis to manufacture their own food.

Air Pollution Control can also be achieved by heavily fining industries that do not comply with Emission Standards Code and also by regulation of industrialization. Air pollution can also be controlled by banning or restricting importation of vehicles that do not meet emission code standards in order to reduce vehicle emissions.

Prepared for Strategic Legal Solutions Group Limited, by:

Anita OWITI, & Centre for Environmental Law & Policy (a participating consultancy firm in the SLS Group of consultancies).

2.      25th March 2014 World Health Organization Report http://www.who.int/mediacentre/news/releases/2014/air-pollution/en
4.      April 2015The Guardian ,London, UK, “Air pollution may cause  more UK death than previously thought, say scientists” http://www.theguardian.com/environment/2015/apr/02/air-pollution-may-cause-more-uk-deaths-than-previously-thought-say-scientists
5.      EPA , May 2004 “Clean Air nonroad Diesel Rule” https://www3.epa.gov/otaq/documents/nonroad-diesel/420f04032.pdf
6.      BC Lung Association. 2005. Health and air quality 2005. Phase 2: Valuation of health impacts from air quality in the lower Fraser Valley airshed. 127pp. Available at www.bc.lung.ca/pdf/health_and_air_quality_2005.pdf
7.      Joan Leslie Aron, Jonathan Patz, 2001. Ecosystem Change and Public Health: A global perspective (page 379-400). The Johns Hopkins University Press, Baltmore and London https://books.google.co.ke/books?hl=en&lr=&id=_FjXiPOFcs8C&oi=fnd&pg=PA379&dq=dispersal+of+air+pollutants+through+thermal+inversion,+grasshopper+effect+and+wind&ots=7YlAU0dX32&sig=XeCZp06rFtkd7gf135KtYYgslnU&redir_esc=y#v=onepage&q&f=false

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