Literature Review

Background

Air pollution has become an ongoing problem in many countries in the Southeast Asian region, and Malaysia is one of the worst affected countries. Among the main causes of air pollution is the development of the country such as industry, smoke emissions from vehicles and heavy machinery, open burning and often receiving air pollution from foreign countries such as Indonesia, which is haze. Malaysia also receives impacts from neighboring countries every year. Especially Sumatra, which mostly affects Peninsular Malaysia and Kalimantan, which mainly affects East Malaysia. 

Based on the records, Malaysia is suspected of having such a high Air Pollution Index (API) in 1997. The unsafe API reading happened again in 2005 when it reached 500 which is at a very dangerous level. Remember that in 2019, the country will be haze free. Oh! That's wrong. Last September 26, Batu Pahat district recorded IPU at a concentration of fine particles (PM) of 1.02 (unhealthy level) and several cities were also covered in dust. So, it is true that experts predict throughout this year, the haze that is expected to occur in March will continue until September. What is certain, the 'symptom' can last until the middle of October depending on the wind blowing from the northeast.(Afroz,Review of air pollution and health impacts in Malaysia 2003)

Particulate Matter

Particulate means particulate matter (also called particulate pollution) a term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small that they can only be detected using an electron microscope..(Grantz 2003)

Particulate matter (PM) refers to a complex mixture of solid and liquid particles suspended in the air. These particles can vary in size, composition and origin. They are categorized based on their aerodynamic diameter, which determines how far they can penetrate the respiratory system and potentially cause health effects. The most commonly used classification for particulate matter is based on the size of PM10 particles with a diameter of 10 micrometers (μm) or smaller. These particles can be inhaled and can reach the upper respiratory system. PM2.5 particles with a diameter of 2.5 μm or smaller. These particles are fine and can penetrate into the lower respiratory system and even enter the bloodstream. PM1.0 particles with a diameter of 1 μm or smaller. These are ultrafine particles that can penetrate deep into the respiratory system and potentially cross the blood-air barrier. Particles can come from natural and man-made sources. Natural sources: Dust and soil particles, pollen, sea salt spray, volcanic ash and forest fires are examples of natural sources of particulate matter. Anthropogenic sources: Human activities contribute significantly to particulate matter pollution. These sources include combustion processes (vehicular emissions, industrial emissions, power generation), construction activities, agricultural practices (burning crop residues), and various industrial processes.(Ecological effects of particulate matter 2003)

Chemical Composition Of Particulate Matter

In the chemical composition of particles, we can classify them into several types, including organic compounds containing carbon elements except carbon oxide (carbon monoxide and carbon dioxide), carbide compounds, cyanide compounds, carbonate compounds, and bicarbonate compounds. Simple organic compounds can be classified according to the functional groups present in the compound. In addition, there are also inorganic compounds which are common chemical compounds that lack carbon-hydrogen bonds, compounds that are not organic compounds. Next is the carbon element (EC) Carbon is a chemical element in the periodic table that has the symbol C and atomic number 6. This element is a non-metallic element that has many tetravalents. Carbon is found in all living carbon and is the basis of organic chemistry. Non-metals also have interesting chemical properties that are able to bond with each other and many other elements. In addition, secondary aerosols, which are part of the particles, are formed through atmospheric reactions. And finally, there is biological content such as microorganisms.(Perrino, 2004)

Organic Compound

Any large class of chemical compounds in which one or more carbon atoms are covalently bound to atoms of another element, typically hydrogen, oxygen, or nitrogen. The carbon-containing compounds carbides, carbonates, and cyanides are not classified as organic. Carbon atoms provide the primary structural framework that generates the vast variety of organic compounds. All living creatures on Earth (and most likely elsewhere in the universe) rely on organic compounds for their survival. Organic compounds include nutrients, which include lipids, proteins, and carbohydrates, as well as essential substances such as haemoglobin, chlorophyll, enzymes, hormones, and vitamins. Clothing made of cotton, wool, silk and synthetic fibres; common fuels, such as wood, coal, petroleum and natural gas; components of protective coatings, such as varnishes, paints, lacquers and enamels; antibiotics and synthetic drugs; natural and synthetic rubber; dyes; plastic; and pesticides are also composed of organic compounds.(Source apportionment of airborne particulate matter using organic compounds as tracers. Atmospheric Environment, 30(22), 3837-3855.) 

Particulate matter often contains organic compounds originating from various sources such as combustion processes, industrial emissions and vegetation. These organic compounds include polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), aldehydes and other carbon-based compounds.(Newman,2004)

Inorganic Compound

In chemistry, inorganic compounds are usually chemical compounds that do not have carbon-hydrogen bonds, i.e. compounds that are not organic compounds. The study of inorganic compounds is a subfield of chemistry known as inorganic chemistry. Inorganic compounds comprise most of the Earth's crust, although the composition of the inner mantle remains an active area of investigation. Some simple carbon compounds are often considered inorganic. Examples include allotropes of carbon (graphite, diamond, buckminsterfullerene, etc.), carbon monoxide, carbon dioxide, carbides, and the following inorganic anion salts, carbonates, cyanides, cyanates, and thiocyanates. Most of these are normal parts of most organic systems, including organisms; describing a chemical as inorganic does not necessarily mean that it does not occur in living things.

Particulate matter can contain a variety of inorganic compounds, including sulfates (SO4), nitrates (NO3), ammonium (NH4), carbonates, silicates and various metals. The presence of inorganic compounds depends on the emission source and the atmospheric response.(Perry,2016)

Elemental Carbon (EC)

Elemental carbon is found in nature as two crystalline allotropic forms, graphite and diamond. Elemental carbon also occurs as a spectrum of imperfect turbostratic crystal forms that range in degree of crystallinity from amorphous to perfectly crystalline allotropes. Recently a third crystal form of elemental carbon, the fullerene structure, has been discovered. Elemental Carbon is a particulate component consisting of pure carbon in its elemental form. It is often associated with combustion processes, such as emissions from vehicle exhausts, industrial emissions, and biomass burning.

Trace Elements

Trace elements (or trace metals) are minerals present in living tissues in small amounts. Some of them are known to be nutritionally essential, others may be essential (although the evidence is only suggestive or incomplete), and the remainder are considered to be nonessential.(Strachan ,2010)

The trace elements are also called minor elements. An element is considered a trace element when its requirement per day is below 100 mg. The deficiency of these elements is rare but may prove fatal. Examples include copper, iron, zinc, chromium, cobalt, iodine, molybdenum, and selenium(Mertz, W. (1981). The essential trace elements. Science, 213(4514), 1332-1338.) 

Particulate matter may contain trace elements originating from both natural and anthropogenic sources. These elements include metals such as lead (Pb), arsenic (As), cadmium (Cd), nickel (Ni), and others. The specific trace elements present can depend on the emission sources and local geological characteristics.(Strachan,2010)

Secondary Aerosols

Secondary organic aerosols (SOA) are molecules produced by oxidation over several generations of parent organic molecules. In contrast to primary organic aerosols, which are emitted directly from the biosphere, secondary organic aerosols are either formed by homogeneous nucleation through successive oxidation of gas-phase organic compounds, or by condensation on existing particles. These gas-phase species have high vapor pressures, meaning they are volatile and stable in the gas phase. After oxidation, the polarity increases, and thus reduces the volatility, of the molecule resulting in a reduction in vapor pressure. After sufficient oxidation, the vapor pressure is low enough that the gas phase compounds partition into the solid phase, producing secondary organic matter (secondary organic aerosol particle phase). SOA represents the majority of aerosols contained in the troposphere. A common misconception is that an aerosol refers to the solid phase of a compound, when in fact, by definition, it is the combination of the gas and solid phases that make up the aerosol. Secondary aerosols are formed in the atmosphere by chemical reactions. For example, ammonium sulphate aerosols are formed from the gases sulphur dioxide and ammonia, whilst organic aerosols are formed by chemical reactions acting on chemicals such as isoprene, which is emitted by vegetation.(Sun,  2016) 

Some particulate matter is formed through atmospheric reactions. For example, gaseous pollutants like sulfur dioxide (SO2) and nitrogen oxides (NOx) can undergo chemical transformations and form secondary particulate matter, including sulfate and nitrate aerosols.(Saxena,1967)

Biological Components

When it comes to biological components in particles, it refers to the presence of biological substances or substances in particles. These biological components can include, Bacteria and Viruses: Particles can harbor different types of bacteria and viruses, either as living organisms or as waste. These microorganisms can originate from sources such as soil, water, plants, or human and animal activities. Second, Pollen and Plant Material: Particles may contain pollen grains and plant debris, especially during high pollen release seasons. These biological particles can contribute to allergies and respiratory problems in susceptible individuals. Next, Fungal Spores, Fungi release spores into the air as part of their reproductive cycle. These spores can become suspended in particulate matter and can have health implications, especially for individuals with allergies or respiratory problems. Animal Dander Particles of animal skin, hair or fur, known as dander, can become airborne and contribute to particulate matter. This is particularly relevant in indoor environments with pets or in areas with high animal populations. The presence of biological components in particles can have direct and indirect health effects. Direct effects include respiratory irritation, allergic reactions, and worsening of respiratory conditions. Indirect effects can arise from interactions between biological components and other pollutants, leading to the formation of secondary pollutants or influencing the toxicity of particulate matter.(Morakinyo ,2016)

They include fungi, bacteria, viruses, endotoxin and pollens that originate from terrestrial and marine environments during biological processes. Bioaerosols are present in the atmosphere as individual organisms, or are attached to PM, dust or water droplets. Particulate matter can also contain biological materials such as pollen, spores, bacteria, fungi, and other microorganisms. These components vary depending on the environment, vegetation, and local sources.(Keller, J. 2005)