ASSESSMENT OF AIR QUALITY ALONG THE TRAFFIC

CORRIDOR IN LAGOS METROPOLITAN CITY

BY

MOMOH ITUNU DORCAS

PHY/DE/19/018

A RESEARCH PROJECT SUBMITTED TO THE DEPARTMENT OF,

PHYSICAL SCIENCES, FACULTY OF SCIENCE,

IN PARTIAL FULFILMENT FOR THE AWARD OF BACHELOR OF TECHNOLOGY HONS

DEGREE IN PHYSICS, OLUSEGUN AGAGU UNIVERSITY OF SCIENCE AND

TECHNOLOGY, OKITIPUPA, ONDO STATE ,NIGERIA.

i
 DECLARATION

I, MOMOH ITUNU DORCAS, hereby declare that all information and activities reported in this project

were written and carried out by me during the period of research. All sources of information are

acknowledged using references.

Student’s signature…………………….. Date…………………………

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 CERTIFICATION

This is to certify that the research work reported in this project write up was carried out by MOMOH

ITUNU DORCAS, with Matriculation Number PHY/DE/19/018, and submitted to the Department of

Physical Sciences, School of Science, Olusegun Agagu University of Science and Technology, Okitipupa,

Ondo State. Having met the standard as approved by the institution and approved as to content and style

by:

DR. O.R. OMOKUNGBE …………………………..

SUPERVISOR SIGNATURE/DATE

DR. F.O. ADEYEMI …………………………..

HEAD OF DEPARTMENT SIGNATURE/DATE

………………………………… ………………………….

EXTERNAL SUPERVISOR SIGNATURE/DATE

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 DEDICATION

The project report is dedicated to God Almighty who has been my source of Strength, Grace and Wisdom

throughout the period of my course, through whose Grace and Favor I have been able to run my course

and scale through the hurdles of my academic pursuit.

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 ACKNOWLEDGEMENTS

All thanks to the almighty God for his divine mercy and guidance and for making this project work a

success. My sincere gratitude to my project supervisor Dr. O.R. OMOKUNGBE who has been of help to

me during the process of undertaking this study into writing a better report, providing valuable

suggestions, for the patience and care he showed to me during this project work to make it successful,

thanks for all your input, may God continue to bless you. To the head of department Dr. N.O. BAKARE,

and all Lecturers and Staffs of Physical Sciences Department, DR. Ajanaku, (My course adviser), DR.

Ilori, and others, I say very big thanks for impacting me with vast knowledge and for your academic help

so far.

Also, my profound gratitude to my parents Mr. and Mrs. Momoh Adetoye, who through their prayers,

guidance, patience, and care endured and strived so hard for me, so that I can complete my program. May

God bless you and keep you always.

With heartfelt love, I acknowledge those who influenced my life positively, my sibling (Oluwatimilehin

Adeola) and friends (Tomiwa, Ifeoluwa Familusi, Channah, Abbey, Toluwani Akinrotoye) and others may

God crown all your efforts with success and make you excel in all your endeavours.

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TABLE OF CONTENT

Contents Pages
DECLARATION...................................................................................................................................ii
CERTIFICATION...............................................................................................................................iii
DEDICATION......................................................................................................................................iv
TABLE OF CONTENT.......................................................................................................................vi
LIST OF FIGURES.....................................................................................................................................viii
LIST OF TABLES.........................................................................................................................................ix
LIST OF PLATES..........................................................................................................................................x
INTRODUCTION...................................................................................................................................11
1.2 AIR POLLUTION IN NIGERIA......................................................................................................15
1.3 STATEMENT OF RESEARCH PROBLEM........................................................................19
1.4 AIM OF THIS STUDY............................................................................................................20
1.5 SPECIFIC OBJECTIVES OF THE RESEARCH................................................................20
1.6 SCOPE OF THE STUDY..................................................................................................................21
1.7 JUSTIFICATION OF THE STUDY......................................................................................21
1.8 CONTRIBUTION TO KNOWLEDGE.................................................................................22
1.9 LIMITATION OF STUDY......................................................................................................22
1.10 DEFINITIONS OF TERMS....................................................................................................22
CHAPTER TWO..........................................................................................................................................25
LITERATURE REVIEW.............................................................................................................................25
2.1 Sources of Air Pollution...............................................................................................................25
2.1.1 NATURAL SOURCES..................................................................................................................25
2.1.2 HUMAN-MADE SOURCES.........................................................................................................27
2.2 CRITERIA POLLUTANTS OF PRIORITY CONCERN FOR AMBIENT AIR QUALITY:..............30
2.3 LINK BETWEEN AIR QUALITY AND TRAFFIC MANAGEMENT...............................................32
2.4 EFFECTS OF AIR POLLUTION ON HUMAN HEALTH..................................................................39
2.5 EFFECTS OF AIR POLLUTION ON ENVIRONMENT.....................................................................41
2.6 EFFECT OF PARTICULATE MATTER ON HUMAN HEALTH......................................................43
2.7 AIR QUALITY.................................................................................................................................44
METHODOLOGY.......................................................................................................................................46
3.1 Description of the study area.............................................................................................................46
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3.2 Procedure for Data Acquisition and Data Analysis................................................................................47
3.3 Basic Principles of Electrochemical Sensors..........................................................................................48
CHAPTER FOUR.........................................................................................................................................53
RESULTS AND DISCUSSION...................................................................................................................53
4.1 Weekly Variations of the Pollutants with Prevailing Meteorological Parameters............................53
4.2 Pollutants Hourly Trends with Prevailing Meteorological Parameters.............................................57
4.3 Directional Dependence of the Pollutants.........................................................................................58
CONCLUSION AND RECOMMENDATION..............................................................................................1
CONCLUSIONS:...........................................................................................................................................1
RECOMMENDATIONS:...............................................................................................................................1
General Recommendations:............................................................................................................................2
REFERENCES...............................................................................................................................................3

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 LIST OF FIGURES
Figures Caption Page
Fig 4.1 Weekly Trend of CO , NO , NO 2, Temperature, Relative Humidity and 58
Wind Speed at Majidun, Lamata and Motor Ways

Fig 4.2 Hourly Trend of CO , NO , NO 2, Temperature, Relative Humidity and 59

Wind Speed at Majidun, Lamata and Motor Ways

Fig 4.3 Pollution Rose of CO , NO and NO 2 at Majidun Site 60

Fig 4.4 Pollution Rose of CO , NO and NO 2 at Lamata Site 61

Fig 4.5 Pollution Rose of CO , NO and NO 2 at Motor Ways Site 62

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 LIST OF TABLES
Tables Caption Page
Table 3.1 Image of GMC 500 23

Table 3.2 Image of mobile GPS app 23

Table 3.3 Map of Ondo state showing Okitipupa, the study area 24

Table 4.3 The radiological hazard indices distribution of the AEDE and ELCR. 31

Table 4.4 Graph of Dose Rate and the values of various body organs (BOD) 32

Table 4.5
Table 4.6

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 LIST OF PLATES
Figures Caption Page
Plates 3.1 Image of GMC 500 23

Plates 3.2 Image of mobile GPS app 23

Plates 3.3 Map of Ondo state showing Okitipupa, the study area 24

Plates 4.3 The radiological hazard indices distribution of the AEDE and ELCR. 31

Plates 4.4 Graph of Dose Rate and the values of various body organs (BOD) 32

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 ABSTRACT

In Lagos Metropolitan City, the city's fast urbanization and growing car traffic have had a substantial
influence on air quality, raising health and environmental threats. With an emphasis on the concentration
of pollutants like nitrogen dioxide (NO2), nitrogen monoxide (NO), and carbon monoxide (CO), as well as
meterological parameters (T,RH, and WS), this study attempts to evaluate the air quality along traffic
corridors in Lagos. This study uses a combination of spatial sampling and real-time air monitoring
statistics to identify pollution hotspots and assess temporal fluctuations over the course of the day and
week. Along with evaluating the efficacy of current air quality control techniques, the study looks into
links between traffic density and pollutant levels. Initial results point to higher than average pollution
levels in high-traffic locations, with rush hour concentrations being the highest.

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xii
 CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY

Globally, air pollution poses a serious threat to public health. Over 90% of the world’s population is

exposed to dangerous levels of PM 2.5, and the World Health Organization (WHO) estimates that there are

4.2 million premature deaths annually that can be linked to fine ambient particulate matter pollution

(PM2.5) (WHO Pollution, 2018). The quality of the air we breathe varies widely around the world, and

people in many low- and middle-income nations are most exposed to it (Shaddick et al., 2020). Some of

these countries have PM2.5 levels that are more than five times the WHO Air Quality Guidelines. In terms

of its effects on health, there are numerous techniques for evaluating air pollution levels. While the

assessment of longer-term exposures is necessary for the estimation of the disease burden, short-term

forecasting supports communication and prompt public health action, especially for the most vulnerable

(Kumar et al., 2018). The latter is highly important because, while reducing exposure during air pollution

episodes will lessen the chances of acute injury, the greatest health benefit is anticipated with long terms

reductions that minimize the possibility of chronic sequelae (Shaddick et al., 2020). The quality of life and

public health have lately been harmed in numerous key European (EU) cities due to recently discovered

critically high pollution (Jesemann et al., 2022). The most common anthropogenic air pollutants include

particulate matter (PM), volatile organic compounds (VOCS), ozone (O 3), carbondioxide (CO), sulfur

dioxide (SO2), nitrogen oxides (NO2/NOX), nitrogen monoxide (NO), and oxygen (O). These pollutants

are caused by local industries, excessive traffic, and house heating (Zheng et al., 2022).

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Lagos Metropolitan City is one of the most densely populated and rapidly growing urban centers in

Africa. Lagos being the Nigeria’s major economic hub has experienced significant expansion and

urbanization, leading to increased vehicular traffic and industrial activity. This growth has brought

numerous benefits to the city, including economic development and job opportunities, but it has also

resulted in challenges, particularly regarding air quality.The heavy traffic in Lagos is a major contributor

to air pollution, as a large number of vehicles release harmful emissions such as particulate matter (PM),

nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and volatile organic compounds

(VOCs). These pollutants can have serious health effects on the city's residents, ranging from respiratory

and cardiovascular diseases to other long-term health issues.

In addition to traffic-related pollution, the city's geography and climate can exacerbate air quality

problems. Lagos is situated on the coast, and its high humidity and warm temperatures can influence the

behavior of pollutants. Furthermore, weather patterns such as wind direction and strength can affect the

dispersion and concentration of air pollutants. Despite these challenges, there is limited data and research

on the specific air quality issues along traffic corridors in Lagos. Understanding the levels and sources of

pollution in these areas is crucial for developing targeted interventions and policies to protect public health

and improve the quality of life for residents. The background of the study highlights the need to conduct a

thorough assessment of air quality along traffic corridors in Lagos to address these issues and provide

data-driven recommendations for sustainable urban planning and effective air quality management. By

doing so, this research aims to contribute to the city's efforts to balance growth and development with the

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well-being of its residents and the environment. The atmosphere is the gaseous envelope that surrounds

the earth and constitutes the transition between its surface and the vacuum of space (Bhatia,2009). The

atmosphere is composed primarily of nitrogen (N2) and oxygen (O2) and is made up of many layers of air,

in each one which is identified by their thermal characteristics or temperature changes, chemical

composition, movement and density (Narayanan, 2009). Life on earth is supported by the layers of air,

solar energy and our planet's magnetic fields, and the quality of air is very essential to its sustenance

(Oxlade, 1994; Ojo and Awokola, 2012).Air pollution is the introduction of chemicals, particulate matter

or biological materials that cause harm and discomfort to humans and other living organisms (Bhatia,

2009). The most common air pollutants in the urban environment include: sulphur dioxide (SO 2); oxides

of nitrogen (NOx), such as nitrogen oxide, (NO) and nitrogen dioxide (NO 2); carbon monoxide

(CO);volatile organic compounds (VOCs); ozone (O 3); suspended particulate matter (SPM) also called

particulates; and lead (Pb) (Lutgens and Edward, 2000). Air pollutant can be in the form of solid particles,

liquid droplets, or gases. In addition, they may be natural or man-made (USEPA, 2006; Narayanan, 2009).

Sources of air pollution include traffic (vehicle exhaust), industrial sectors (from brick making to oil and

gas production), power plants and generating sets, cooking and heating with solid fuels (e.g. coal, wood,

crop waste), forest fires and open burning of municipal waste and agricultural residues (Akanni, 2010;

Komolafe et al., 2014).

Air pollution is becoming a topic of intense researches at all levels because of the increased level of

anthropogenic activities and climatic changes. Air pollution in the urban center has increased rapidly due

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to high population density, increased numbers of motor vehicles, use of fuels with poor environmental

performance, poorly maintained transportation systems and above all, ineffective environmental

regulations and policies (Komolafe et al., 2014). Air pollution is believed to kill more people worldwide

than AIDS, malaria, breast cancer, or tuberculosis (WHO, 2014). Airborne particulate matter (PM) is

especially detrimental to health (Beelen et al., 2013), and has previously been estimated to cause between

3 and 7 million deaths every year, primarily by creating or worsening cardio-respiratory disease (Hoek et

al.,2013).

Particulate sources include electric power plants, industrial facilities, automobiles, biomass burning, and

fossil fuels used in homes and factories for heating. In China, air pollution was previously estimated to

contribute to 1.2 to 2 million deaths annually (WHO, 2014; Yang et al., 2013). Figure 1.1 depicts the air

pollution emanating from diesel powered vehicle along the traffic corridor.

1.2 AIR POLLUTION IN NIGERIA

The major cities of Nigeria are slowly coming under serious threat from atmospheric pollution. High

amounts of localized air pollution are produced by incomplete combustion of diesel power engines in

motor vehicles, particularly in urban metropolitan regions. The expansion and importation of used

automobiles as well as the widespread use of single-engine “okada” motorbikes for passenger

transportation throughout the majority of Nigerian cities have increased the overall level of air pollution.

In fact, compared to all other human activities combined, driving a car causes the most air pollution

(World Resources Institute 1992). Nearly 50 percent of global carbon monoxide, hydrocarbon, and

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nitrogen oxide emissions from fossil fuels combustion come from gasoline and diesel-powered engines. In

city central like Lagos and Abuja, especially on highly congested streets, traffic can be responsible for as

much as 90% to 95% of the ambient carbon monoxide levels, 80% to 90% of the nitrogen oxides and

hydrocarbon. In addition, a large portion of the particulates, posing a significant threat to human health

and natural resources (Savile 1993).

However, total reliance on biomass materials which has been the main energy source for domestic needs

of the poor in Nigeria has also been the major menace, among other things, as partly responsible for a

variety of health problems particularly among women. Industrial energy usually contributes to the overall

level of air pollution. More so, the gas flaring in the Niger Delta oil-producing regions of the Nigeria

constitute majority to atmosphere pollution problem in Nigeria.

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FIG 1.1: Air Pollution emanating from a diesel powered vehicle along the traffic corridor

Source: https://thelogicalindian.com/environment/pollution-in-india

These have heightened the level of airborne emissions of pollutants such as sulphur dioxide, carbon

monoxide, nitrogen oxides and volatile organic compound (VOC) all which are hazardous and

deteriorating to human and materials. As reported, carbon dioxide emissions from industries activities are

estimated from gas flares alone. Nigeria has been struggling since the 1950s, when oil was discovered

there. The growth of the country’s oil industry, coupled with the population explosion as well as lack of

xviii
environmental regulation has led to substantial damage to Nigeria’s environment and air quality especially

in the Niger Delta region, which is the central industry oil base of Nigeria (Oyekunle, 1999). The Sahara

desert’s invasion in the north and severe air pollution in densely populated areas like Kaduna, Lagos, and

Abuja provide the country with additional environmental concerns related to air pollution and

desertification (Ifeanyichukwu, 2002). Oil spills, gas flare-ups, and deforestation are the main

environmental problems in the Niger Delta. This gas flaring is one of the key factors causing the

environmental hazards and this is associated with the uncontrolled burning of the natural gas waste in the

oil production processing (Bassal, 1981). This study focuses on one of the most populous, but visibly

polluted Nigerian urban environments. Lagos metropolis has been experiencing air pollution problems in

all its severity over the past decades which are associated with high density of industries, transport

networks and open waste burning. Several research works have been carried out in assessing air quality in

traffic dense area and industrial zones in selected part of Lagos, but there seems to be a paucity of

information on full scale monitoring considering the contribution of pollutants from vehicular traffic,

residential area, industrial zones and dumpsite areas. Hence, the objective of this study is to present the air

quality monitoring data of selected gaseous pollutants (SO2, NO, NOx, CO, CO2, noise) and suspended

particulate matter (SPM) in Lagos along the major high traffic corridor, and also examine the AQI rating

for ambient air quality.

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1.3 STATEMENT OF RESEARCH PROBLEM

Lagos Metropolitan City, one of the most densely populated and fastest-growing urban areas in Africa,

faces significant challenges related to air pollution due to its heavy traffic volume and rapid urbanization.

The traffic corridors in Lagos are particularly congested, with high levels of vehicular emissions

contributing to poor air quality. Despite being a major public health concern, there is limited

comprehensive research on the levels and sources of air pollution along these traffic corridors. This lack of

data hinders the development of targeted strategies to improve air quality and protect the health of the

city's residents. Therefore, there is an urgent need to assess air quality along the traffic corridors in Lagos

to identify the main pollutants and their sources, evaluate their impact on public health, and provide data-

driven recommendations for policy and urban planning interventions.

1.4 AIM OF THIS STUDY

The aim of the study is to evaluate the air quality along traffic corridors in Lagos Metropolitan City in

order to gain a comprehensive understanding of the levels and types of air pollutants present. The air

quality assessment in this study will help to identify the key sources of the pollutants, their potential

impact on public health and the environment. This will also provide data-driven insights for stakeholders

to formulate policies that will improve air quality, promote a clean and healthier urban environment for

the residents of Lagos and its environs.

1.5 SPECIFIC OBJECTIVES OF THE RESEARCH

The objectives of the study are;

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 (i) Measure and analyze the concentration levels of key air pollutants such as nitrogen dioxide

(NO2), along traffic corridors in Lagos Metropolitan City.

(ii) evaluate the potential impact of air pollution on public health

(iii) know the relationship between air quality and some identified meteorological parameters

1.6 SCOPE OF THE STUDY

The scope of the study encompasses the assessment of air quality along major traffic corridors in Lagos

Metropolitan City, focusing on the criteria pollutants such as particulate matter (PM), nitrogen dioxide (NO2),

sulfur dioxide (SO2), carbon monoxide (CO), and ozone (O3). The research will cover both peak and off-peak

traffic hours across a variety of locations representative of the city's traffic patterns. The study will involve real-time

monitoring and data collection of air pollutants at strategic points along the corridors. It will also consider the

meteorological conditions to provide a comprehensive analysis of the effects of these meteorological variables on

the air quality. In addition, an examination of the potential health impacts of air pollution on residents using air

quality index so as to know the vulnerable groups to both short and long-time exposure. Finally, the study will offer

recommendations for air quality management and policy interventions to improve public health and environmental

quality in Lagos.

1.7 JUSTIFICATION OF THE STUDY

Lagos Metropolitan City is one of the fastest-growing urban centers in Africa, experiencing rapid industrialization

and a significant increase in vehicular traffic. This growth has led to elevated levels of air pollution, particularly

along major traffic corridors. However, poor air quality is a pressing public health concern, as it can cause or

exacerbate respiratory and cardiovascular diseases, cancer of the lungs and other health issues. Despite these

challenges, there is inadequate of dataset on air pollution levels and sources specific to Lagos' traffic corridors,
xxi
hindering effective policy-making and urban planning. This study is necessary as it addresses the major knowledge

gap by providing an in-depth assessment of air quality along traffic corridors, identifying pollution hotspots, and

understanding their sources and impacts on health. The research findings will support the development of targeted

interventions and policies to improve air quality, thereby enhancing the health and quality of life of the residents of

Lagos and contributing to sustainable urban development.

1.8 CONTRIBUTION TO KNOWLEDGE

The study intends to provide a comprehensive assessment of air quality along major traffic corridors in Lagos

Metropolitan City. Also, real-time monitoring of these pollutants will give up-to-date insights into the spatial and

temporal variations of air pollution for Lagos, Nigeria and the tropical region, which can inform strategies and

policy formulation to mitigate poor air quality. This information can guide policymakers and urban planners in

implementing targeted interventions for advance future air quality studies.

1.9 LIMITATION OF STUDY

This study is limited to Lagos Metropolis and its environs being one of the pollution hotspots in Nigeria.

1.10 DEFINITIONS OF TERMS

Air Quality: A measure of the cleanliness or pollution of the air in a particular area, often indicated by the

concentration levels of various pollutants.

Traffic Corridor: A route or pathway in an urban area with a high volume of vehicular traffic, such as

major roads, highways, and intersections.

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Particulate Matter (PM): A mixture of tiny particles and droplets in the air, which can be harmful when

inhaled. It is usually categorized by size, such as PM2.5 (particles smaller than 2.5 micrometers) and

PM10 (particles smaller than 10 micrometers).

Nitrogen Dioxide (NO2): A reddish-brown gas commonly produced from vehicle emissions and

industrial processes. NO2 is a significant air pollutant that can have harmful effects on human health and

the environment.

Sulfur Dioxide (SO2): A colorless gas with a sharp odor, often produced by the burning of fossil fuels

such as coal and oil. SO2 can contribute to respiratory problems and acid rain.

Carbon Monoxide (CO): A colorless, odorless gas produced by the incomplete combustion of fossil

fuels. CO can be harmful when inhaled, as it interferes with the blood's ability to carry oxygen.

Ozone (O3): A reactive gas that occurs both at ground level and in the upper atmosphere. Ground-level

ozone is a major component of smog and can be harmful to human health and vegetation.

Volatile Organic Compounds (VOCs): A group of organic chemicals that easily evaporate into the air.

VOCs can be emitted by vehicles, industrial processes, and consumer products, and can contribute to air

pollution.

Health Impact: The potential effects of air pollution on human health, including respiratory and

cardiovascular issues, as well as other diseases.

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 CHAPTER TWO

LITERATURE REVIEW
2.1 Sources of Air Pollution
Sources of air pollution can be broadly categorized into natural sources and human made. Although, some

air pollution sources may be accessed through other means such as estimation of emissions and so on.

Apart from that, local sources and sources located further away (even hundreds of kilometres, or

transboundary) also contribute to air pollution and are important contributors to the air quality of a place.

2.1.1 NATURAL SOURCES

Naturally occurring particulate matter (PM) includes dust from the earth’s surface (crustal material), sea

salt in coastal areas and biological material, in the form of pollen, spores or plant and animal debris.

Volcanic eruptions can introduce very important quantities of gases and particles into the atmosphere. For

example, the Etna volcano emits 3000 tons of sulphur dioxide (SO2) on an average day and up to 10000

tons during periods of great activity. During the cataclysmic eruptions of the Tamborain 1815 in

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Indonesia, 100 billion tons of volcanic products were ejected into the atmosphere, 300 million tons of

which reached the stratosphere which resulted in a mean temperature fall of 0.7 0C over the whole earth. In

some rural areas, periodic forest fires produce large amounts of PM (Ref).

Other natural sources of air pollution include: thunderbolts, which produce significant quantities of oxides

of nitrogen (NOx); algae on the surface of the oceans, which give out hydrogen sulphide (H 2S); wind

erosion, which introduces particles into the atmosphere; and humid zones, such as swamps, peat-bogs or

little deep lakes, which produce methane (CH4) by reactions between NOx and volatile organic

compounds, VOCs (Ref).

DUST: In wide open spaces with little vegetation and low precipitation, wind can naturally produce dust

storms. When the particle matter in the dust mixes with the air, it can naturally warm the environment and

provide a health risk to living things. Attention is drawn to the fact that finer street dust fractions pose an

even greater threat because of how easily they can penetrate the respiratory tract. When dispersed into

areas with native flora, particulate particles can also act as a natural barrier to photosynthesis (Wojciech

Zglobicki et al., 2019).

WILD FIRE: Seasonal changes and a lack of precipitation both contribute to the natural occurrence of

wildfires in woody areas during extended dry seasons. Due to the Greenhouse Effect, this is caused by the

smoke and carbon monoxide produced by these fires, the atmosphere’s carbon concentration is rising

quickly. Wildfires are associated with several environmental impacts, including economic losses, impacts

xxv
on water resources and impacts on air pollution, which poses serious health hazard (Igor Cobelo et al.,

2023).

VEGETATION AND ANIMAL DIGESTION: Another kind of natural air pollution that results in the

production of methane, another greenhouse gas, is animal digestion, especially that of cattle. On warmer

days, flora including willow, black gum, poplar, and oak trees produces considerable volumes of volatile

organic compounds (VOCs) in several parts of the world. Low-lying seasonal hazws that are ozone-rich

are created when these combine with primary anthropogenic pollutants, notably nitrogen oxides, sulphur

dioxide, and carbon compounds.

VOLCANIC ACTIVITY: Natural air pollution is primarily caused by volcanic eruptions. Massive

quantities of sulfuric, chlorine, and ash products are produced during an eruption and released into the

atmosphere where they can be carried by the wind and scattered over a wide area. Additionally, because of

their capacity to reflect solar radiation, substances like sulphur dioxide and volcanic ash have been found

to naturally chill the environment. Volcanic ash, characteristics that inform whether ash may cause harm if

inhaled or indigested include particle size, particle shape, surface area, and the presence of leachable

elements (Carol Stewart et al., 2022).

2.1.2 HUMAN-MADE SOURCES

In urban areas, most air pollution comes from human-made sources. Such sources can be classified as

either mobile (cars, trucks, air planes, marine engines, etc.) or point source (factories, electric power

plants, etc.). To date, road traffic constitutes the major source of air pollution in the large cities of

xxvi
industrialized countries. Combustion of carbon-constituted fuels (coal, fuel oil, wood, natural gas) is never

complete, and it produces carbon monoxide (CO) and hydrocarbons. Nox result from the combination of

fossil fuels contained in motor fuel at high temperature. Human activities have increased the amount of

VOCs due to petroleum, chemical industries and transportation, and NO x result from the combination of

air nitrogen and oxygen from combustion in power stations and automobiles. Consequently, O 3 is more

concentrated and more smog occurs in densely populated and industrial regions (ref).

EMISSIONS FROM FOSSIL FUELS: One of the main causes of air pollution is the combustion of

fossil fuels like coal, gasoline from cars, and other industrial combustibles. These are typically utilized in

manufacturing facilities, trash incinerators, power plants, furnaces, and other fuel-burning heating

equipment. Significant amounts of power are needed for air conditioning and other services, which

increases the emissions of fossil fuels. According to the Union of Concerned Scientists (UCS), the US

industry is responsible for 21% of greenhouse gas emissions, with power generation making up the

remaining 31% (Edenhofer et al., 2014).

AGRICULTURE AND ANIMAL HUSBANDRY: Methane produced by cattle is one of several

variables that contribute to the creation of greenhouse gas emissions from agriculture (the raising of crops

and livestock). Another factor is deforestation, which occurs when trees that would otherwise absorb

carbon and purify the air are cut down to make way for pastureland and agricultural areas. Agriculture is

responsible for 24% of yearly emissions, according to the IPCC Fifth Assessment Report. This estimate

however, does not account for the 20% of emissions from this sector that ecosystems counteract by

xxvii
sequestering carbon in biomass, decomposing organic matter, and soils. Pollutants from agriculture greatly

affect water quality and can be found in lakes, rivers, wetlands, estuaries, and groundwater. Pollutants

from farming include sediments, nutrients, pathogens, pesticides, metals, and salts. Animal agriculture has

an outsized impact on pollutants that enter the environment (Wikipedia., 2023).

WASTE EMISSIONS: Landfills are also known to generate methane, which is not only a major

greenhouse gas, but also an asphyxiate and highly flammable and potentially hazardous if a landfill grow

unchecked. Population growth and urbanization have a proportional relationship with the production of

waste, which in turn leads to greater demand for dumping grounds that are far removed from urban

environments. These locations thus became a significant source of methane and carbon dioxide

production, CO2 and CH4 can cause major global surface temperature increase (Rabia Munsif et al., 2020).

2.2 CRITERIA POLLUTANTS OF PRIORITY CONCERN FOR AMBIENT AIR QUALITY:

Ambient air quality refers to the quality of the air in the outdoor environment that people breathe. It is

determined by the presence and concentration of various pollutants, including gases and particulate matter,

in the atmosphere. These pollutants can be emitted from various sources, such as industrial facilities,

vehicles, power plants, and natural sources like wildfires or dust storms.

Monitoring and assessing ambient air quality is crucial to understanding the level of pollution and its

potential impacts on human health, ecosystems, and the environment. Several key pollutants are

commonly measured and monitored to assess air quality.

Carbon Monoxide (CO)

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A notoriously poisonous and lethal pollutant known for having no distinguishing color or smell is carbon

monoxide. Most frequently, combustion engines operating without new catalytic converters, obsolete gas

and fuel appliances, incinerators, and even cigarettes emit carbon monoxide. Due to its severe

poisonousness and ability to contribute to extremely hazardous ozone and ground-level air conditions,

carbon monoxide can have a significant impact on the environment. It results in flu-like symptoms such as

headaches, nausea, lethargy, dizziness and chest pain in those with coronary heart disease, reduced

eyesight and coordination at higher concentrations, lightheadedness and confusion, and potentially

harmful health effects on unborn children at high concentrations (Agency, Carbon Monoxide’s Impact on

Indoor Air Quality, 2021).

NITROGEN DIOXIDE (NO2)

One of the oxides that can combine to create ozone is nitrogen dioxide; however this is by no means its

only unfavorable effect. One of the more obtrusively hazardous pollutants, nitrogen dioxide is thick,

brown, causes choking, and is a pollutant. Similar to many other pollutants, nitrogen dioxide is most

frequently emitted into the atmosphere as a result of the burning of fossil fuels in manufacturing facilities,

power plants, aircraft, and automobile engines. Its tendency to react with other substances to generate

nitric acid and organic nitrates, which contribute to the development of acid rain, makes it a suffocating

and obstructive gas in the air as well. Acid rains produced by Nitrogen Dioxide are extremely harmful to

soils, plants and animals across the world, and can lead to further problems in water systems. Nitrogen

xxix
Oxide has a huge effect on humans, enhancing the likelihood of respiratory problems, asthma, cancers,

and other lung problems (Agency. 2020).

2.3 LINK BETWEEN AIR QUALITY AND TRAFFIC MANAGEMENT

Traffic is a major source of air pollutants in urban areas. In Europe, exhaust from motor vehicle traffic is

considered to contribute to more than 50% of ambient particle matter less than 10 mm (PM10)

concentrations. However, relatively few studies mainly in Europe have investigated the specific effects of

traffic related air pollution on human health.

Epidemiological studies on the health effects of traffic related air pollutants commonly use subjective

assessment of traffic exposure such as self-reported street type, traffic intensity, frequencies of traffic jams

at the home address, or proximity of the home to major roads. Moreover, air pollution annoyance scores

and traffic noise annoyance scores8 9 have also been used as exposure measures which combine exposure

to traffic related air pollution, perception, and awareness of traffic related pollution and noise. All of these

subjective indicators are easy to obtain, do not require monitoring data, and can easily be applied in large

scale studies with minimal effort and cost. However, the validity and reliability of these subjective

exposure surrogates have been challenged recently. Most of the studies indicated above using subjective

assessment of traffic related air pollution exposure did not validate their exposure indicators, but rather

interpreted the results with caution. Further, most of the authors argued that exposure misclassification

could not be excluded, and that heterogeneous result among different studies or no-effect studies could be

possibly due to insufficient exposure assessment and misclassification. Typically, subjects who reported

xxx
on traffic at their home address also answered health questionnaires. Thus, in particular cross-sectional

study results could be severely biased if both the exposure and potential health impacts were assessed

subjectively. The European Environmental Agency (EEA) and the Environmental Noise in Europe

(ENE, 2020) identified that urbanization, economic development activities (e.g. transport development of

road lanes, increase in traffic and high construction and extension of cities) were the main drivers for the

increase in environmental noise in 2020. The most common type of environmental noise among other

sources is road traffic noise. According to statutory requirements (Barnes et al., 2018), the UK

Government leads on the UK’s input to International and European legislation relating to air quality, with

input from the Scottish Government, and the other devolved administrations. Linking to the requirements

of the EU Directives, the latest Air Quality Strategy published in July 2007 (DEFRA, 2007) established

the framework for air quality improvements across the UK. Measures agreed at the national and

international level are the foundations on which the strategy is based. The strategy sets out the Air Quality

Standards and Objectives which have been set to benchmark air quality in terms of protecting human

health and the environment. However, air quality is a devolved matter within the UK, with the Scottish

Government having responsibility for the development of air quality policy and legislation for Scotland

and other regions with similar responsibilities. Emissions of nitrogen dioxide, carbon monoxide, and

particulate matter (PM10 and PM2.5) emissions from road transport have fallen by 77% (4.5 million

tonnes, 16,000 tonnes and 17,000 tonnes, respectively) between 1990 and 2017, but high levels of

pollution still exist (Jones et al., 2019). Following more strict exhaust emission standards, emissions of

numerous pollutants that are particularly harmful to human health (such as carbon monoxide, particulate
xxxi
matter, and nitrogen oxides) have decreased. As the UK strives to achieve net zero emissions by 2050,

reducing emissions from road transportation remains a serious problem; as of the end of 2018, 0.5% of all

vehicles permitted in the UK were ultra-low emission vehicles. From 255 billion miles driven on British

roads in 1990 to 328 billion miles in 2018, there was a 29% rise. Due to newer vehicles' higher fuel

efficiency, the total amount of fuel used for road transport in the UK remained largely consistent between

1990 and 2017. While gasoline consumption decreased throughout this time, diesel use climbed. An

individual and combined effect of noise and air pollution has been studied internationally through

epidemiological analysis (Tétreault et al., 2013). Sørensen et al. (2014) showed that there were combined

effects of air and noise pollution on human health resulting in increased risk of stroke. Studies have also

shown that air and noise pollution has effects on cognitive functioning among children (Van Kempen et

al., 2012). In other parts of the world, studies on noise and air pollution have shown that these exposures

can increase the risk of viral infection due to a decreased immune system (Hjortebjerg et al., 2018). Road

traffic noise and air pollution generate considerable interest due to increase in economic and social

activities in most cities that are densely populated, especially the urban areas of the UK (EEA, 2006). The

transport sector is the largest source of noise and air emissions in urban environments. A Study from the

UK have shown that urban areas are polluted by high frequency of noise in association with air pollution

and that high car traffic volumes correlate positively with high frequency noise and air pollution,

especially at night-time (Adza et al., 2023). Environmental noise from road traffic is also the target of

many campaign groups in UK due to the relative air emissions and road traffic noise and air pollution have

a strong correlation (Davies et al., 2009). Despite the potential adverse effects of noise and air pollution on
xxxii
health, it is anticipated that the next decade will see increase transport of vehicle with passengers’ more

than 8.3 billion affecting remarkable features of Great Britain in both residential area and

commercial/business districts (TSGB, 2019). It is significant to acknowledge the caveat on the increase in

transportation and passengers as COVID restrictions has change peoples’ habits and work practices. The

association between environmental noise and air pollution needs to be assessed to allow reliable action

planning if threshold limits are exceeded (Murphy et al., 2010; Beattie et al., 2015). In New York, a study

conducted on the association of noise level and constituent air pollutants showed that noise threshold limit

was exceeded. The constituent air pollutant includes nitrogen oxides and particle pollution (also known as

particulate matter). There was an association between traffic, noise, and air pollution from combustion

between intra urban areas suggesting confounding evidence impacting on epidemiological studies of

health-related traffic issues (Kheirbek et al., 2014). According to ENE (2020), potential adverse effects of

noise pollution include annoyance, sleep disturbance, cardiovascular disease and cognitive impairment.

Studies on road traffic and environmental noise have reported an association with auditory and wider

health impacts such as hearing loss and cardiovascular-related events such as myocardial infarction,

hypertension, stroke and heart failure (ENE, 2020).It has been suggested that the risk of cardiovascular

disease (CVD) in European regions may be related to environmental noise and air pollution. According to

British Heart Foundation (Scarborough et al., 2011), CVD is simply defined as all diseases affecting the

heart and blood vessels found in the cardiovascular system. Potential and established risk factors for CVD

include age, family history, smoking and physical inactivity (Scarborough et al., 2011). Evidence testing

the relationship between noise, air pollution and hypertension is limited (Van Kempen et al., 2012, Gan et
xxxiii
al., 2012, Tétreault et al., 2013; Floud et al., 2013 and Clark, 2015), but interest in this area for the UK has

increased recently (Carey et al., 2016, Shin et al., 2020 and Adza et al., 2022). According to the World

Health Organization, the devolved regional Governments in the UK have implemented directives of the

European Union (EU) for environmental noise and air quality (WHO, 2011). These have resulted in noise

maps to meet required response to the European Parliament and Council Directive for Assessment and

Management of Environmental Noise 2002/49/EC, more commonly referred to as the END (King et

al., 2016). Despite the direct association of environmental noise and air pollution and until the introduction

of the Environmental Protection Act 1990 and Environmental Noise Directive (END) 1990 (Sands et

al., 1991; Haigh, 1992), there were few concerns in the UK relating to road noise and air pollution

(Foraster, 2013). However, this has changed in recent years and studies on their combined effects have

been initiated (WHO, 2018). Some cohort studies in the UK have used the distance to major roads as a

surrogate for exposure to air pollutants in relationship to cardiovascular health impact (Cai et al., 2017,

2018). Other studies have also used spatial and temporal distributions to investigate associations of road

traffic noise and air pollution with cardiovascular outcomes (De Kluizenaar et al., 2013; Fecht et

al., 2016). However, a research gap exists between the association of road traffic noise and air pollution

with hypertension and other cardiovascular outcomes in the UK (Beelen et al., 2009), even though cohort

studies are ongoing in European countries to assess issues related to traffic noise and air pollution

exposures. Both road traffic noise and air pollution may be associated with hypertensive heart disease, but

mechanisms may differ (Babisch et al., 2014; Pitchika et al., 2017; Fuks et al., 2017; Sears et al., 2018).

xxxiv
Understanding the association between these pollutants and their joint effects on human health is essential

for developing population-based policies for further improving health outcomes (Fecht et al., 2016). This

can be explored by evaluating associations between modelled noise and air pollutants using different

spatial units and area characteristics. However, results from epidemiological studies with respect to the

joint cause–effect association are rare. The public health evaluation framework models available in the

literature that provide the opportunity to address the joint associations of road traffic noise and air

pollution with hypertension are evaluated. Through a systematic literature review, the implementation and

policy integration and assessment of progress on selected issues of the joint cause–effect relationships

between road traffic noise and air quality and implications for public health, particularly in relation to the

UK and its devolved nations. The aim and objective of the study were to determine the suitability of the

conceptual framework as well as demonstrating the application of the conceptual framework for an

environmental health tracking system (EHTS) for UK. Considering that the paper is centred on selecting a

conceptual framework for EHTS in the UK, the paper would benefit from introducing what is a conceptual

framework and why it is important to have one for an EHTS (Edokpolo et al., 2019; Eisenberg et

al., 2007; Frank et al., 2019; Harwell et al., 2019; Kyle et al., 2006; McGeehin et al., 2004).

xxxv
2.4 EFFECTS OF AIR POLLUTION ON HUMAN HEALTH
Globally, air pollution is reported as a major environmental risk factor that poses a substantial threat to

human health (Cohen et al., Estimates and 25year trends of the global burden of disease attributable to

ambient air pollution: An analysis of data from the Global Burden of Diseases Study 2015,2015).

Approximately 90% of the global population is at risk of air pollution and the disease burden attributable

to air pollution continues to grow, posing a serious threat to global health (Organization, Ambient

(Outdoor) Air Pollution, 2021). As per global estimates, air pollution, both ambient air pollution (AAP)

and household air pollution (HAP), accounts for 7 million premature deaths worldwide (Organization,

Ambient (Outdoor) Air Pollution, 2021). Moreover, the burden of disease attributed to air pollution is

considerably higher in low-and-middle-income countries (LMICs), where more than 90% of deaths occur,

compared to high-income countries (Landrigan, et al., The Lancet Commission on Pollution and health.,

2018).

Ambient air quality refers to the overall condition of the air in a specific environment or region. It is

influenced by various factors such as industrial emissions, vehicle exhaust, dust, pollen, and natural

sources. The health effects of ambient air quality depend on the concentration and types of pollutants

present. Here are some potential health effects associated with poor ambient air quality:

Respiratory Problems: Exposure to polluted air can lead to respiratory issues such as irritation of the

airways, coughing, wheezing, shortness of breath, and exacerbation of asthma and other respiratory

xxxvi
conditions. Fine particulate matter (PM2.5) and nitrogen dioxide (NO2) are particularly linked to respiratory

problems.

Cardiovascular Issues: Poor air quality can contribute to the development or worsening of cardiovascular

diseases. Fine particulate matter and other pollutants can enter the bloodstream causing inflammation,

oxidative stress and damage to blood vessels, which may increase the risk of heart attacks, strokes, and

other cardiovascular problems.

Allergies and Asthma: Airborne allergies like pollen, mold spores, and certain pollutants can trigger

allergies and asthma symptoms in susceptible individuals. High levels of ozone (O 3) and particulate matter

can aggravate these conditions, leading to increased respiratory distress and reduced lung function.

Lung Cancer: Long-term exposure to air pollutants, especially carcinogens such as benzene

formaldehyde, and certain types of particulate matter, is associated with an increased risk of developing

lung cancer. These substances can be released from sources like vehicle emissions and industrial

processes.

Reduced Lung Function: Prolonged exposure to air pollution can result in reduced lung function,

especially in children, older adults, and individuals with pre-existing respiratory conditions. It can lead to

chronic obstructive pulmonary disease (COPD) and other lung-related ailments.

xxxvii
Premature Death: Studies have shown a correlation between long-term exposure to polluted air and

premature death due to respiratory and cardiovascular diseases. The World Health Organization estimates

that millions of premature deaths occur globally each year due to exposure to air pollution.

It’s important to note that the specific health effects may vary depending on the concentration and duration

of exposure to different pollutants, as well as an individual’s susceptibility and overall health.

Governments and organizations work to establish air quality standards and regulations to minimize risk

and promote cleaner air for everyone.

2.5 EFFECTS OF AIR POLLUTION ON ENVIRONMENT

Air pollution has significant effect on the environment, which can impact ecosystems, wildlife, and overall

environmental health. Here are some key effects of air pollution on environment;

AIR QUALITY DEGRADATION: Air pollution directly affects air quality by releasing pollutants such

as particulate matter (PM), nitrogen oxides (NO X), sulfur oxides (SOX), volatile organic compounds

(VOCs), and ozone (O3). These pollutants can cause respiratory problems, smog formation, and damage to

plants and ecosystems thereby decreasing the quality of air. It is estimated that 4.2 million deaths occur

every year because of exposure to ambient (outdoor) air pollution (WHO, 2018). People are likely to adapt

their lifestyles in response to the degrading air quality levels (Deepty Jain et al., 2022).

ACID RAIN: Acid rain was one of the most important environmental issues during the last decades of the

twentieth century. For some time, particularly during the 1980s, acid rain was by many considered to be

one of the largest environmental threats of the time. Acid rain is created when certain air pollutants,
xxxviii
especially sulphur dioxide (SO2) and nitrogen oxides (NOx), react with atmospheric moisture. Aquatic

habitats, woods, and vegetation may suffer negative consequences as a result of acid rain. Additionally, it

can erode infrastructure, monuments, and buildings (Peringe Grennfelt et al., 2019).

WATER AND SOIL POLLUTION: According to European Environment agency, suspended particulate

matter from the atmosphere can accumulate in the soil, bringing with it other pollutants such as toxic

metals which can now affect water bodies and land thereby causing water and land pollution. This can

harm aquatic life, contaminate drinking water sources, and affect soil fertility and agricultural

productivity.

ECOSYSTEM DISTRUPTION: Several air pollutants, such as hydrochlorofluorocarbons (HCFCs) and

chlorofluorocarbons (CFCs) can harm the ozone layer. Ozone depletion increases the amount of harmful

ultraviolet (UV) radiation that reaches the Earth’s surface, which increases the risk of skin cancer,

cataracts, and other health issues in both people and animals.

2.6 EFFECT OF PARTICULATE MATTER ON HUMAN HEALTH

Particulate matter has been confirmed to have health implications on the human. Onabowale and Owoade

(2015), stated that about 28% of the sickness and death is caused by indoor air particulate in developing

countries. The result of the studies carried out by WHO (2014) attributed more than 7 million deaths to the

impact of PM (indoor and outdoor) in india (Delhi). Air pollution has been reported to cause 10,000 to

300000 deaths every year (Gopalaswami, 2016), acute and chronic problems are due to inhalation of PM 10

and PM2.5 (Ezeh et al., 2012), and damage to respiratory organs (Moses and Orok, 2015) Ontario Ministry
xxxix
of the Environmental and Climate Change (2010), reported that the greatest effect on health is from PM 2.5.

This has resulted in hospitalization. Affected people (Old and Children) with asthma, cardiovascular and

lung diseases are most vulnerable to fine PM. Duration of exposure has an effect on the sickness Quoted

by Gopalaswami (2016).

2.7 AIR QUALITY

Air quality refers to the degree to which the air is suitable or cleans enough for humans or the

environment. Air quality refers to the condition of the air in a specific environment concerning the

concentration of pollutants and other substances that can have adverse effects on human health, animals,

plants, and the overall ecosystem. These pollutants may include particulate matter (PM), nitrogen dioxide

(NO2), sulphur dioxide (S02), ozone (O3), carbon monoxide (CO), volatile organic compounds (VOCs),

and others. (N.S.W Government, 2023).

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xli
 CHAPTER THREE

METHODOLOGY

3.1 Description of the study area

Based on field inspections conducted in Lagos, a coastal metropolis estimated to have a population of

approximately 25 million, three research locations (Majidun, Lamata, and Motor Ways) along the traffic

corrodors were selected. The metropolis is vulnerable to storms, heat waves, coastal erosion, floods, and

ocean surges (Ogunsawe et al., 2021). Lagos State is located in the southwest of Nigeria and has an

elevation that fluctuates from 3.8 meters above sea level to below sea level in some places. Lagos is a city

that spans approximately 350 000 hectares and features a generally flat slope that promotes water retention

(Ogunsawe et al., 2021). The city experiences two distinct seasons, a wet season from March to November

and a dry season from December to February, which is brought on by Harmattan winds from the Sahara

Desert. These variations in climate are caused by exchanges between the warm, moist marine tropical air

mass and the hot, arid continent rising air from the interior of the country (Olufemi et al., 2023). The

hottest month is March, while the coldest month is August. Due to intense sea-based disturbances, Lagos

has tropical weather with an average relative humidity of 79% and an average wind speed of 1.2 m/s

(Olufemi et al., 2023). With humid air all year round, the yearly mean rainfall is roughly 1657 mm. In

addition, the average daily temperature is between 29 and 41 °C, and there is little surface wind

movement. The digitalized map of Lagos State's three high-traffic locations (Majidun, Lamata, and Motor

Ways) is shown in Figure 3.1. Lagos experiences tropical weather with a mean relative humidity of 79%,

and an average wind speed of 1.2 m/s as a result of strong sea-based disturbances (Olufemi et al, 2023).

xlii
The annual mean rainfall is about 1657 mm with humid air all through the year. Additionally, the daily

temperature ranges 29 to 41 °C, and the surface wind flow is not particularly strong. The Figure 3.1

depicts the digital map of the three high traffic volume sites namely; Majidun, Lamata and Motor Ways in

Lagos State.

3.2 Procedure for Data Acquisition and Data Analysis

The study utilized a low-cost Alpha sense electrochemical sensor dataset that was obtained from the

Environmental Pollution Research Laboratory, Department of Physics and Engineering Physics, Obafemi

Awolowo University, Ile-Ife. The dataset covered the period from December 1st to December 31st, 2018.

The information obtained in this investigation at 2-second intervals was condensed to a daily average of

one hour. The weekly and hourly trends of the gaseous pollutants and the meteorological factors, pollution

rise, and the correlation plots along the three traffic corridors (Majidun, Lamata, and Motor Ways) in

Lagos State were plotted using the 1-hour average dataset for data analysis in this study. Furthermore, the

statistical analyses and charting in this work were performed using the OpenAir project for R-statistics

(Carslaw, 2015; Carslaw and Ropkins, 2012).

3.3 Basic Principles of Electrochemical Sensors

When the gaseous species of interest come into contact with the sensor, they pass through a hydrophobic

barrier to reach the electrode surface. This process is required to allow the correct amount of gas to react at

the sensing electrode in order to produce a sufficient electrical signal. At the working electrode, there is a

redox reaction that generates an electronic charge, which is balanced by a complimentary redox reaction in

xliii
pair at the counter electrode. When the gaseous species reacts with the sensor, an electrical signal

proportional to the gas concentration is produced.

Figure 3.1: Digital Map Showing the three sampling sites: Majidun, LAMATA and Motorways.

xliv
The sensor's output, which is the movement of electrons between the working and counter electrodes, is

driven by the redox pair (Alpha sense, 2015; Mead et al., 2013). Typically, a signal is produced by the

reduction reaction occurring at the counter electrode in addition to the oxidation reaction occurring at the

working electrode (Popoola, 2012). After that, the circuit board reverses the signal to produce a matching

positive voltage. Between the anode and the cathode, the resistor placed across the electrodes facilitates

the flow of current proportionate to the gas concentration. The concentration of the gas can be found by

measuring the current. The potential of the counter electrode varies in the target gas present as current is

created to offset the redox reaction occurring at the working potential (Alpha sense, 2015). This

electrochemical sensor consists of a photo ionization detector (PID), non-dispersive infrared carbon

dioxide (CO2) sensor, anemometer, temperature and humidity sensor probes, optical particle counter

(OPC), global positioning system (GPS) receiver and packet radio services (GPRS) transmitter.

Furthermore, the electrochemical sensor employed in this investigation can measure gaseous and particle

contaminants, including CO, NO, NO 2, O3, and CO2. The photo ionization detectors (PID), carbon dioxide

(CO2), anemometer, optical particle counter (OPC), global positioning system (GPS) receiver, and general

packet radio services (GPRS) transmitter were connected to the electrochemical sensor. In addition, it

features built-in power cables, temperature and humidity sensors, and B-series electrochemical cells

specifically made for each type of gas (Plate 3.1).

xlv
Plate 3.1: Diagram showing the Typical Electrochemical Gas Sensor and its Components

Source: Popoola, (2012).

CHAPTER FOUR

RESULTS AND DISCUSSION

4.1 Weekly Variations of the Pollutants with Prevailing Meteorological Parameters

Table 1 presented the statistical description of the gaseous pollutants (CO, NO, NO 2) and the

meteorological parameters (T, RH, ws) during the observation period at the three study locations

(Majidun, Lamata, Motor ways). As observed, the mean concentration of CO, NO, NO 2, T, RH, WS

xlvi
ranged from 1214-2403ppb, 13.2-77.9ppb, 53.6-65.7 ppb, 27.7-28.00C, 58.9-63.6% and 0.50-1.15 m/s,

respectively in all the three sites. The highest concentration of CO was observed at Lamata and this is

attributed to the high influx of vehicular movement which enhanced the concentration. This result is in

line with what was reported by Olufemi et al., 2023. The period of decrease in the concentrations across

all sites coincides with the period of light traffic after the early morning ‘rush hours. In addition, during

the noon time, the height of the boundary level (BL) expands which provides a larger mixing region that

aided the dispersion of pollutants (olajire et al., 2011), hence reduces the concentrations of CO. This trend

was also observed at ‘Majidun’ with a decrease in the concentration of CO corresponding to the period of

reduced traffic flow.

Figure 4.1 gave detailed analysis of the weekly trends of key air pollutants, including carbon monoxide

(CO), nitrogen oxides (NO and NO₂), with meteorological parameters such as temperature, relative

humidity, and wind speed across three significant urban locations namely Majidun, LAMATA, and Motor

Ways. Figure 4.1 showed distinct patterns, particularly the noticeable spikes in NO and NO₂

concentrations during the early morning hours, which coincide with peak traffic times. This pattern is

especially pronounced at the Motor Ways location, suggesting higher levels of vehicular emissions and

potential traffic congestion in that area. These findings are critical as they align with established research

that links increased traffic density with elevated pollution levels in urban settings. As observed, higher

concentrations of the pollutants were noticed during the weekdays compared with the weekends and this

may be linked to the busy nature of weekdays as a result of the high commercial activities. Furthermore,

xlvii
 when these observations are compared to the World Health Organization (WHO) air quality standards

specifically the 1-hour mean limit of 200 µg/m³/106.4 ppb for NO₂ it becomes evident that the pollutant

levels during peak hours may surpass these safety thresholds, posing a significant public health risk. The

study underscores the importance of continuous monitoring and the Implementation of effective pollution

control measures, particularly in high-traffic urban areas, to ensure that air quality remains within safe

limits. Additionally, the consistent patterns observed in temperature and relative humidity, which

inversely correlate with each other, highlight the complex interplay between meteorological conditions

and pollutant dispersion, further emphasizing the need for integrated strategies to manage urban air

quality.

TABLE 1: Summary of the Statistical Description of the CO , NO , NO 2, Temperature, Relative Humidity

and Wind Speed during the Observation period at the three Study Sites in Lagos. Min–minimum, 1st

Quartile, Med–median, 3rd Quartile, Max–maximum, Mean.

Sites Parameters Units Min. 1st Med. 3rd Max, Mean

Quart. Quart.

MAJIDUN CO ppb 105.7 656.9 1061.8 1612.8 4098.8 1214.9

NO ppb 1.81 2.19 6.01 14.54 126.67 13.29

NO 2 ppb 5.07 43.94 56.29 66.71 109.95 53.69

T ℃ 20.88 24.80 26.81 31.16 38.29 28.02

rh % 16.32 50.00 69.13 79.17 88.97 63.54

ws m/s 0.16 0.43 0.65 0.90 2.45 0.74

xlviii
LAMATA CO ppb 375 1229 2087 3531 5722 2402

NO ppb 1.95 13.16 56.23 124.94 344.18 77.93

NO 2 ppb 1.51 30.46 51.04 83.31 181.77 59.33

T ℃ 22.81 25.84 27.67 30.42 33.42 27.95

rh % 18.46 46.25 61.53 72.23 87.76 58.96

ws m/s 0.32 0.77 1.11 1.44 2.71 1.15

MOTOR CO ppb 456.9 1162.9 1651.1 2367.9 5925.6 1827.8

WAYS NO ppb 1.94 3.15 15.35 35.67 148.68 25.07

NO 2 ppb 16.71 51.16 62.40 80.34 145.64 65.74

T ℃ 22.61 25.61 26.93 29.99 33.40 27.65

rh % 19.54 49.71 64.59 75.81 90.19 61.82

ws m/s 0.00 0.00 0.45 0.92 2.36 0.52

4.2 Pollutants Hourly Trends with Prevailing Meteorological Parameters

Figure 4.2 illustrates the hourly trends of CO, NO, NO₂, temperature, relative humidity, and wind speed at

Majidun, LAMATA, and Motor Ways. Figure 4.2 indicated that there was a significant increase in

pollutant levels, particularly NO and NO₂, during the early morning hours (around 6 am) and late

afternoon (around 6 pm), coinciding with peak traffic periods which may be linked to early morning and

late evening rush hours. It was observed that the pollutants magnitude dropped at about 6 am in morning

and attained its troughs between 11 am and 12 pm. The reduction in pollutants concentration is an

indication that the atmosphere was unstable during this period which enhanced pollutants effective

dispersal. Motor Ways showed the most pronounced spikes, suggesting that traffic intensity is higher there

xlix
compared to Majidun and LAMATA. These peaks in pollutant levels may exceed the WHO's

recommended limits, particularly the 1-hour mean of 200 µg/m³/106.4 ppb for NO₂, raising concerns

about potential health risks during these times. The trends observed in this analysis are consistent with

previous studies that highlight the influence of traffic emissions on urban air quality (Omokungbe et al.,

2023). Moreover, the variations in temperature and relative humidity further influence these pollutant

levels, with higher temperatures often correlating with increased concentrations of NO and NO₂ due to

enhanced photochemical reactions. This Figure 4.2 underscores the critical need for traffic management

and pollution control strategies to ensure compliance with WHO air quality standards and protect public

health in urban areas.

4.3 Directional Dependence of the Pollutants

Figure 4.3 illustrated the pollution rose plots for CO, NO, and NO₂ at the Majidun site, alongside a wind

rose chart showing wind direction and speed. The pollution roses for the three pollutants indicated the

directional dependence of these pollutants, with the highest concentrations of CO, NO, and NO₂ occurring

when winds are predominantly from southwest and northwest, indicating the proximity of traffic or

industrial activities around these directions as the potential sources of pollution. The wind rose shows that

winds are most frequently blowing from the southwest and northwest, which correlates with higher

pollutant levels from these directions. This pattern suggests that emissions from these areas contribute

significantly to air quality issues at Majidun. When compared to WHO standards, NO₂ was noticed to

have exceeded the 1-hour mean of 200 µg/m³/106. 4 ppb permissible limits, particularly when the winds

transversed from heavily polluted areas. These findings are consistent with previous research highlighting
l
the impact of wind patterns on the dispersion of traffic-related pollutants in urban environments. The

result of the findings suggested that local wind patterns played a significant role in the determination of

the air quality and as such, management strategies to effectively reduce exposure to these harmful

pollutants is highly needed. Figure 4.4 showed that the pollution rose plots for CO, NO, and NO₂ at the

LAMATA site aligned with the wind rose plot. The pollution roses indicated that the highest

concentrations of CO, NO, and NO₂ were associated with winds emanating from the easterly and

northeasterly directions. This suggests that some factors such as traffic or industrial activities which is

along the prevailing wind directions relative to the LAMATA site enhanced the pollutants concentrations

recorded along these directions. Figure 4.5 gave the Pollution Roses for CO, NO, and NO₂ pollutants at a

Motor Ways site, alongside a Wind Rose depicting wind direction of high frequency. The Pollution Roses

indicated the distribution of pollutant concentrations relative to wind direction, with higher levels of CO,

NO, and NO₂ primarily associated with northwesterly and northeasterly directions. As observed, the wind

rose indicated the wind direction is predominant northwesterly and northeasterly directions. Comparing

these findings with previous works, similar studies have shown that pollutant Concentrations are often

higher near roadways and are strongly influenced by wind direction, which can either dilute or concentrate

pollutants depending on the direction and speed (Olufemi et al., 2023; Omokungbe et al., 2023).

li
Figure 4.1: Weekly Trend of CO , NO , NO 2, Temperature, Relative Humidity and Wind Speed at
Majidun, Lamata and Motor Ways

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Figure 4.2: Hourly Trend of CO , NO , NO 2, Temperature, Relative Humidity and Wind Speed at
Majidun, Lamata and Motor Ways
Color Code: CO (red), NO (Olive), NO 2 (green), T (Teal), RH (blue) and ws (pink)

liii
Figure 4.3: Pollution Rose of CO , NO and NO 2 at Majidun Site

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Figure 4.4: Pollution Rose of CO , NO and NO 2 at Lamata Site

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Figure 4.5: Pollution Rose of CO , NO and NO 2 at Motor Ways Site

4.4 Correlation Plots of the Pollutants

Figure 4.6 presented the correlation plots of pollutants (CO, NO, and NO₂) and meteorological parameters
(such as wind speed, temperature, and humidity) at three different sites: Majidun, Lamata, and Motor
Ways. The color-coded and elliptical shapes in the plots represent the strength and direction of
correlations between these variables. Red and narrow ellipses indicate strong positive correlations, while
blue and narrow ellipses indicate strong negative correlations. At all three sites, there is a noticeable
positive correlation between NO and NO₂, which is consistent with former studies that highlight the
relationship between these pollutants as they are both products of combustion processes, particularly from
vehicles. Wind speed often shows a negative correlation with pollutant concentrations, suggesting that

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higher wind speeds may help to disperse the pollutants, reducing their mass concentrations. This pattern is
well-documented in air quality research, where wind plays a crucial role in the dilution of air pollutants.
Relating this to WHO standards, particularly for NO₂, the observed correlations emphasize the importance
of meteorological factors in influencing pollutant levels. WHO guidelines suggest monitoring and
managing these pollutants, especially in areas with high vehicular traffic, as the correlations at these sites
likely indicate concentrations that may approach or exceed WHO-recommended limits, posing potential
health risks. Effective air quality management strategies should consider these correlations to mitigate
pollutant exposure and protect public health.

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Figure 4.6: Correlation plots of pollutants and meteorological parameters at Majidun, Lamata and Motor
Ways Sites

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 CONCLUSIONS:
1. The air quality along the traffic corridors in Lagos metropolitan city, specifically Motorways, Majidun,

and Lamata, is severely polluted, posing health risks to commuters and residents.

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2. High concentrations of particulate matter (PM2.5), nitrogen oxides (NOx), and carbon monoxide (CO)

were recorded, exceeding WHO guidelines.

3. Motorways recorded the highest levels of pollution, followed by Majidun and Lamata, indicating a

correlation with traffic volume and congestion.

4. The study reveals a critical need for effective air quality management and emission reduction strategies

in these areas.

5.2 RECOMMENDATIONS:
Motorways:

1. Implement a bus rapid transit (BRT) system to reduce private vehicle usage.

2. Enhance traffic management to minimize congestion and idling times.

3. Install air quality monitoring stations to track pollutant levels.

Majidun:

1. Promote alternative modes of transportation, such as cycling and walking, through infrastructure

development.

2. Encourage the use of cleaner fuels and emission-reducing technologies in vehicles.

3. Establish green spaces and urban forestry initiatives to mitigate air pollution.

Lamata:

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1. Implement emission control measures, such as catalytic converters, for vehicles.

2. Develop and enforce stricter environmental regulations for industries and vehicles.

3. Educate the public on air quality importance and involve them in mitigation efforts.

5.3 General Recommendations:

1. Develop a comprehensive air quality management plan for Lagos metropolitan city.

2. Increase public awareness campaigns on air pollution and its health impacts.

3. Encourage inter-agency collaboration to address air quality issues.

4. Conduct regular air quality monitoring and assessment to inform policy decisions.

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