Air Pollution in Developing Countries

The World Health Organization estimates that ninety-eight percent (98%) of cities in low-income and middle-income countries with more than 100,000 inhabitants do not meet the WHO air quality guidelines. According to a Mr. Marko Tainio an environmental health researcher at the University of Cambridge, " In high-income countries air pollution levels are (in global comparison) lower and getting (slowly) better. In the developing world, especially Asia, concentrations are high and are not improving (in some cases getting even worse). Globally the burden of air pollution is focused on countries like India and China due to combination of high pollution levels and large population” \cite{washingtonpost}
Modernization has seen a shift from the use of biomass fuel to petroleum products and electricity in developed countries. However, in the developing world households continue to use biomass fuels and according to \cite{albalak2000} poverty is one of the main barriers to the adoption of cleaner fuels and  the slow pace of development in many countries suggests that biomass fuels will continue to be used by the poor for many decades. Consequently,  women and young children are exposed to high levels of indoor air pollution every day\cite{Gordon_2014}.
Majority of households in developing countries use earth ovens and stoves whereby combustion is very incomplete resulting in substantial emissions which may produce high levels of indoor pollution. Indoor concentrations of particles usually exceed guideline levels by a large margin: 24-hour mean PM10 levels are typically in the range 300–3000 mg/m3 and may reach 30 000 mg/m3 or more during periods of cooking \cite{Smith_1994}. In comparison, the EPA's  standards for 24-hour average PM10 and PM2.5 concentrations are 150 mg/m3 and 35mg/m3    respectively \cite{epaa}.  In homes using biomass fuels in developing countries, reports have shown that the mean 24-hour levels of carbon monoxide are in the range 2–50 ppm; during cooking, values of 10–500 ppm. In comparison, the United States Environmental Protection Agency’s 8-hour average carbon monoxide standard is 9ppm mg/m3  \cite{epaa}. These high concentrations of particulate matter and carbon monoxide have shown to be associated with health effects like respiratory illnesses to more adverse effects such as reduced lung function amongst children and exacerbation of chronic obstructive pulmonary disease  \cite{Smith_1987}
Even though very limited research has been conducted in the Pacific Island Countries (PICs), it is apparent that these countries share similar air quality concerns such as emissions from transport and burning activities.  A recent study in Fiji by \cite{Isley_2017a} showed that the ambient PM2.5 concentrations in its capital city, Suva, was within the World Health Organization guideline of 10 \(\mu\)m/m3, however,  concentrations of black carbon (BC) in Suva were higher than more industrialised cities and comprised of 30% of PM2.5 . Whilst the level of PM2.5 in the city of Suva are within WHO guidelines Isley et al (2017) suggest that continuous monitoring may show that levels in residential areas of Suva may be close or exceed the WHO guidelines.

Common Air Pollutants and their Sources

The World Health Organization has established that the pollutants with the strongest evidence of health effects are particulate matter (PM), ground-level ozone (O3), nitrogen dioxide (NO2),and sulphur dioxide (SO2) and adverse health consequences can occur as a consequence of short and long-term exposure to these pollutants \cite{who2018b}\cite{Chen_2008} also suggested that these pollutants are commonly used as indicator pollutants for fuel combustion and traffic-related air pollution. In the United States, the USEPA has categorised these four chemicals and two others, namely, carbon monoxide and lead as criteria pollutants because they are basically found all over the United States and can cause harm to human health and the environment. 
For the purpose of this study, the following pollutants will be examined:
1. Particulate matter (PM) is also known as particulate pollution and refers to a mixture of solid particles and liquid droplets with some particles such as dust, dirt, soot or smoke are dark enough to be seen by the naked eye. Particulate matter is further categorized into two parts, PM10 and PM2.5. The former are particles with a diameter of 10 micrometres or less and the latter are particles with a diameter of 2.5 micrometres or less. Due to its microscopic solid or liquid droplets, they can be inhaled and penetrate deep into the lungs and some may even end up in the bloodstream \cite{usepa2017a}. Particulate matter is also made up of a variety of components including nitrates, sulphates, organic chemicals, metals, soil and allergens (such as fragments of pollen or mould spores).  The main sources of particulate pollution are from motor vehicles, wood burning heaters and industries. Particulate pollution can reach extremely high concentrations during bushfires or dust storms\cite{nsw-government2013}.
2. Ground-level ozone (O3) is not emitted directly into the air but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight \cite{usepa2017b}. It is composed of three oxygen molecules joined together with the two basic oxygen molecule (O2) and an additional third atom which makes ozone (O3) an unstable, highly reactive gas. Ozone is found in the upper atmospheres whereby it filters out damaging ultraviolet radiation from the sun and is also present at ground level. Ground level ozone is the main component of smog and is the product of the interaction between sunlight and emissions from sources such as motor vehicles and industries. It is more readily formed during the summer months and is usually at the highest concentration in the afternoon or early evening. Ozone can travel long distances and accumulate to high concentrations far away from the sources of the original pollutants\cite{nsw-government2013a}.
3. Sulphur dioxide (SO2) is formed by fossil fuel combustion in industries and power plants and is highly reactive gas with a pungent irritating smell. For all the sulphur oxides (SOx), SO2  is of greatest concern and is used as the indicator for the larger group of gaseous sulfur oxides. Sulphur dioxide is also released into the atmosphere through natural processes such as decomposition and combustion of organic matter, spray from the sea and volcanic eruptions.
4. Nitrogen Oxide (NO2) is formed by emissions from cars, trucks, buses, power plants, off-road equipments, industries, unflued gas-heaters and gas stovetops. High concentrations can be found especially near busy roads and indoors where unflued gas-heaters are in use. Other indoor sources can be from cigarette smoke or from cooking with gas. NOalso contributes to the formation of ground-level ozone and particulate matter pollution.
5. Carbon-monoxide (CO) is a colorless, odorless gas that can be harmful when inhaled in large amounts. CO is released when something is burned. The greatest sources of CO to outdoor air are cars, trucks and other vehicles or machinery that burn fossil fuels. A variety of items in your home such as unvented kerosene and gas space heaters, leaking chimneys and furnaces, and gas stoves also release CO and can affect air quality indoors \cite{usepa2016}.  

Global Health Effects of Ambient Air Pollution

The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015) estimated the burden of disease attributable to seventy-nine risk factors in 195 countries from 1990 to 2015. GBD 2015 identified air pollution as a leading cause of global disease burden, especially in low-income and middle-income countries.  Ambient particulate matter air pollution (PM2.5), particulate (PM2.5), particulate matter with aerodynamic diameter 2.5μm or smaller)was identified as a leading risk factor for global disease burden with an estimated 2.9 million attributable deaths in the year 2013. An additional 217 000 deaths were attributable to long-term ozone exposure\cite{2016b}. According to \cite{Cohen_2017}, ambient air pollution contributes substantially to the global burden of disease in 2015. This burden of disease has increased for the past 25 years (1990-2015) due to population ageing, increasing non-communicable rates and the increasing air pollution in low-income and middle-income countries. Moreover, the report on the 'State of Global Air 2017', on the global exposure to air pollution and its disease burden as shown in Figure 5 illustrates that the air pollutant PM2.5  was the 5th highest ranking risk factor for death in 2015. PM2.5 was responsible for 4.2 million deaths from heart disease and stroke, lung cancers and respiratory illnesses. Ground level ozone was ranked as the 33rd risk factor causing deaths and was responsible for an additional 254,000 deaths.