The chemical composition of the atmosphere today is so different as compared to the atmosphere that existed before the Industrial Revolution, 1760 – 1830. To define air pollution, we should first consider all those sources that release harmful chemicals into the atmosphere and alter its chemical composition. First of all, all anthropogenic (man-made) emissions are air pollutants. Next, is the natural emission which can be divided into biogenic and geogenic. Biogenic emissions result from the living world such as volatile organic compound emissions from forests and CH4 emissions from swamp. On the other hand, geogenic emissions are from the non-living world, such as volcanic emissions, sea-salt emissions, and natural fires. So, keeping all these sources in mind, ‘air pollutant’ can be defined as any substance that is released into the air from anthropogenic, biogenic and geogenic sources, which is maybe not a component of the natural atmosphere or which is present in higher concentrations than it is present naturally in the atmosphere, and may impose harmful effects either in short or long terms. Therefore, air pollution can be defined as the presence of harmful substances in the atmosphere which is maybe not a component of the natural atmosphere or which is present in higher concentrations than it is naturally present in the atmosphere, that can impose short or long term effects, which is emitted by either anthropogenic, biogenic or geogenic sources. AIR POLLUTANTS
Air pollutants can be divided into primary and secondary pollutants. Both primary and secondary pollutants are known to cause harm if present in high concentrations. Primary pollutants are those that emitted directly into the atmosphere, such as the Carbon compounds(CO,CO2,CH4,and VOC’s), Nitrogen compounds(NO,N2O,and NH3), Sulfur compounds(H2S and SO2), Halogen compounds(chlorides, fluorides, and bromides), and Particulate Matter or ‘aerosols’. (refer to the table below for Particulate Matter categories).
PARTICLE SIZE DESCRIPTION
< 100 microns‘inhalable’ since can easily enter the nose and mouth < 10 microns‘thoracic’ since can penetrate deep in the respiratory system, PM10 < 4 microns‘respirable’ because small enough to pass completely through the respiratory system and enter into bloodstream < 2.5 micronsPM2.5, labeled ‘fine’ in the US
< 0.1 micronsPM0.1, labeled ‘ultrafine’
(table constructed by using information from : http://www.aiha.org/abs05/po105.htm and http://www.greenfacts.org/glossary/pqrs/PM10-PM2.5-PM0.1.htm )
Whereas, secondary pollutants are formed in the atmosphere from the primary pollutants (precursors). The examples of those are NO2 and HNO3 (from NO), Ozone,O3 (from photochemical reactions of nitrogen oxides and VOCs), sulfuric acid droplets (from SO2) and nitric acid droplets (from NO2), sulfates aerosols (from sulfuric acid droplets + NH3 ) , nitrates aerosols (from nitric acid droplets + NH3) and organic aerosols formed from VOCs in gas-to-particle reaction. Acid rain is a result of the wet and dry deposition of these pollutants. In the following page, the health effects imposed by these pollutants are discussed. However, this primary and secondary pollutants are now divided into a smaller scope, namely outdoor and indoor pollutants. As for the outdoor pollutants, it is further divided into criteria pollutants, radioactive pollutants and toxic pollutants.
HEALTH EFFECTS OF AIR POLLUTANTS : CRITERIA POLLUTANTS, TOXIC POLLUTANTS, RADIOACTIVE POLLUTANTS AND INDOOR POLLUTANTS Health Effects of Criteria Pollutants
From the many pollutants listed above, there are six principal pollutants which are regulated by most of the countries in the world, including Malaysia. Those are: CRITERIA POLLUTANTDESCRIPTIONPRIMARY SOURCESHEALTH EFFECT Total Suspended Particulate Matter (TSP)-subcategories: particles < than PM10 and PM2.5 -PM can exist in solid or...