Building A Cleaner, Greener City

A Look at Nairobi Air Pollution Levels,

Sources and Effects.

by Christine Muthoni Mahihu

Introduction

Air quality in most African countries is not monitored on a regular basis and in some cases does not even exist. The deterioration of air quality in most areas is due to high levels of energy consumption by industry and transport and domestic use (UNEP/WHO, 1992). Air quality is assessed based on the concentration of seven air pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter and sulphur dioxide. Emissions from motor vehicles contain a wide range of pollutants, including, particulate matter (PM), volatile organic compounds, sulphur oxides, nitrogen oxides and carbon monoxide (Kinney and Gichuru, 2011). These pollutants affect air quality. Of these pollutants, particulate matter (PM) is of great importance because of its adverse health effects; for example, high PM concentrations in the air increase post neo-natal infant mortality (Woodruff et al, 2006) and premature deaths from heart and lung diseases (Dockery et al, 1993). Particulate matter is a “complex mixture of solid and liquid organic and inorganic particles that share the property of being less than or equal to 2.5 micrograms in aerodynamic diameter” (Kinney and Gichuru, 2011).

Definitions of Common Pollutants in Nairobi:

Particulate Matter (PM) – According to the US Environmental protection agency (US EPA), Particulate Matter (PM), is a mixture of solid particles and liquid droplets found in the air and can be made up of many different chemicals. These include, dust, acids, organic chemicals, soil, dust, smoke and soot. Particulate Matter are smaller than the diameter of a piece of human hair. There are two main types; coarse particles which are less than 10 micrometers (μm) but larger than 2.5 micrometers (μm) (PM(10)), and fine particles which are 2.5 micrometers (μm) or less (PM(2.5)).

Source: http://www.downwindersatrisk.org

In Developing countries, including Kenya, the pollutant of particular concern is PM(2.5); “Because of their small sizes, PM(2.5) particles are able to penetrate deeply into the lungs where they can exert adverse effects.”(USA EPA, 2013).

Black Carbon (BC) – The US Environmental protection agency defines Black carbon (BC) as the strongest light-absorbing component of PM, and is released into the atmosphere when incomplete combustion of fossil fuels, biofuels, and biomass occur. Black Carbon (BC), also known as soot, is emitted by incomplete combustion sources such as diesel and badly tuned gasoline engines. This element is a million times more effective in absorbing energy, such as solar energy, than C02 meaning it is also a significant contributor to global warming. (Vliet & Kinney, 2007; US-EPA).

Nairobi has high concentrations of PM of over 240 micrograms (UNEP,2006), which is higher than the limit set by the World Health Organization (WHO) at

150 micrograms (μm)1. Further, currently in Nairobi, and in Kenya, there does not exist a programme on air pollution measurement and monitoring. There is an increasing need to gather and compile all the research on air pollution that has been conduction to be used as a foundation for further studies. Understanding the level of PM concentration in the air is important, because it would improve upon the existing minimal knowledge on the air quality in Nairobi to inform transport policy solutions and to improve health by reducing emission levels. In an attempt to better understand pollution levels in Nairobi, below are summaries of three studies carried out in Nairobi in 2003, 2006 and 2009.

1 *WHO levels are daily or yearly average exposure levels while measured levels In Nairobi are over a period of set time. This is important to consider when comparing pollution levels to those collected over a shorter period in Nairobi.

Summary of Past Studies.

Title of Study: Motor Vehicles Air Pollution in Nairobi , Kenya (Odhiambo, Kinyua, Gatebe, & Awange, 2010).Year and period of study: February 2003 to April 2003 (3 months).Locations: Nairobi; at a roundabout connecting University and Uhuru highway. Background data was collected from Nakuru; an open space 4km from nearest highway.Data collection Time: Once per week for 8 hours; 9am-5 pm. Pollutants Studied: PM(10) (suspended Particulate Matter).

The Study aimed to measure levels of PM(10) by collect air samples to determine concentrations of PM(10) (suspended Particulate Matter), fine and coarse fraction mass, Trace elements, gaseous pollutants (NO2, NO, O3-Ozone), and also used weather data such as temperature, humidity, solar exposure, cloud cover and rainfall from Kenya Metrological Department (KMD) to determine their effects of pollution levels.

Results

Figure 1- weekly collections of potential pollutants. #The first letter in the sample code refers to the month in which the sample was collected and the second letter refers to the week.

Results show that overall PM(10) levels, which include both the fine and course particles, were mostly higher than WHO guidelines; sometimes 150% higher. These measured levels reflected in the graph above were noticeably high even when compared to levels in Bombay, London and Los Angeles. The study produces evidence to show that high number of vehicles contribute to an increase in coarse, but more so, in fine particulate. There was also a high possibility that other activities such as industrial emissions, contribute to these high levels. Vehicle emissions are therefore more responsible for fine particle concentrations. An interesting added observation was that rain, more so lack of it, increased the amounts of coarse particles in the atmosphere. Vehicle emissions were also responsible for other pollutants such as NO and trace elements PB and Br.

Title of Study: Impacts of roadway emissions on urban particulate matter concentrations in sub-Saharan Africa: new evidence from Nairobi, Kenya (Vliet & Kinney, 2007).Year and period of study: February 4th to 11 (6 total collection days; 2 on Thika Rd), 2006. Location: From window of downtown YMCA, 100 m from roadway and from window of travelling car on Thika Rd. Data collection Time: 12 hour samples collected from YMCA and 2days from car window for 90 minutes each dayPollutant Studied: Air monitoring of PM(2.5) concentrations and Black Carbon (BC) in Nairobi, Kenya.

This study carried out by Vliet & Kinney (2007), Compared PM(2.5) concentrations in an area with heavy traffic with that of a less crowded area. They measured pollution levels a commuter on Thika Road and one residing at the YMCA location may be exposed to. They used portable air sampling systems to collect air samples.

Results

Figure 2: Pollution levels in two urban locations.

According to the results, both PM(2.5) and Black Carbon (BC) levels were much higher on Thika road compared the YMCA site. The results reflect higher

pollution on one of Nairobi major highways; much higher than WHO recommendations, and clearly show that motor vehicles contribute significantly to pollution and low air quality levels in Nairobi, especially on roadways.

Title of study. Traffic impacts on PM 2.5 air quality in Nairobi, Kenya (Kinney et al., 2011).Year and period of study. Two weeks in July, 2009.Locations: Ronald Ngala (near a major minibus(Matatu) stop), Tom Mboya (near the Kenya National Archive building), River Road (next to numerous hotels), Thika Rd. (both sides of the highway), Kenyatta University and Nairobi University.Data collection Time: From 7.30 am to 6.30 pm (18.30), Monday to Friday.Pollutants Studied: PM(2.5) levels in Nairobi.

This study aimed to collect and measure PM(2.5) levels in different parts of Nairobi. The study collected samples in densely populated areas in the CBD, roadways as well as locations far from heavy human and vehicle traffic. Two other samples were collected to measure horizontal and vertical pollution dispersion; one at Chiromo-Museum intersection near the University of Nairobi to measure horizontal dispersion, and the other near Nairobi Fire Station to measure vertical dispersion. This particular sample was used to test if pollution levels change when there is some distance from the polluting source, in this case vehicles.

Results

Figure 3: Average PM(2.5) levels in 5 locations in Nairobi.

Results show huge variations in PM(2.5) concentrations among the different sites ranging from 10.7 to 98.1 μg/m3. As shown in above (Figure 3), the various sites in the CBD, led by Tom Mboya Street, had the highest levels, followed by Thika road. The lowest levels were at the rural site in Kenyatta University. In conclusion, high PM levels were seem next to major roadways, high vehicle and people traffic areas in the CBD, commuter routes and local locations next to roadways (buildings).

It is important to note that there was also significant reduction in PM levels both vertically and horizontally away from roadsides. Concentrations reduce as soon as one moved a few feet away from the traffic source; PM levels were much lower on the downwind location than the upwind location. Reductions were also observed as one moved more floors upwards in the CBD. However, PM levels on the 3rd floor of one of the locations close to heavy traffic areas were still double WHO guidelines.

Sources of Particulate Matter (PM)

The increased volume of car imports in Kenya by 50% between 1992 and 1999 is a major contributing factor of the worsening air quality in the country just as it is the rest of Sub-Saharan Africa (Maina, 2004). According to figure 4 below, trends in motor vehicle registration have risen from about 750,000 in 2005 to over 1.5 million in 2011. The most popular sources of air pollutants, specifically PM, in urban areas specifically are transportation and fuel combustion (WHO, 2001). Motor vehicles, especially diesel powered engines, are the most dominant source of air pollutants, contributing 50 to 80%, in highly populated cities with high traffic density. (Seinfeld, 1989; Akumu, 2013). Black carbon (BC), which forms part of PM, is emitted mostly by diesel and poorly tuned petrol vehicles. There could be other sources of pollution such as biomass and waste burning and previous studies have shown that these could be strong contributors to poor air quality. However, this is also not well understood or investigated. (Vliet & Kinney, 2007).

The main factors leading to air quality degradation and high levels of PM emissions from transport include;

● Ineffective transport and land use planning,● Rising middle class leading to more vehicle ownership;● Rapid rural urban migration,● Lack of adequate investment in public transport;● Central concentration of commercial and industrial activities, leading to

traffic contestation,● High prevalence of old, poorly-maintained vehicles, ● low quality fuels and high levels of sulfur in diesel fuel,● Lack of stringent vehicle emission standards and ineffective

implementation (P. L. Kinney et al., 2011; Akumu, 2013).

Figure 4: Source: Registrar of Motor Vehicles.*Provisional. ** Includes road Construction Vehicles and Farm tractors.

The clear increase of motor vehicles in the city shows there is potential increase in pollution levels from those mentioned in the studies summarized above, where pollution levels at that time were already higher than WHO recommendations. There is urgent need for action now; "One projection estimates that in a “do nothing” (or business as usual) scenario, the number of vehicle trips between 2004 and 2025 in the Nairobi Metropolitan Area will increase by 148% and that the average speed of trips will decrease from 35km/hr to 11km/hr as congestion increases” (Japanese International Cooperation Agency, 2006).

The more immediate reason to act now are the health dangers facing Nairobi citizens. Air pollution is not always visible to the naked eye but has numerous unseen and long term health implications.

PM Health and Climate Effects

According to WHO, PM affects humans more than any other pollutant and kills at least 3.2 million people a year (Akumu, 2013). High PM(10) levels have been

seen to correlate to increased levels of mortality rates, respiratory infections and asthma attacks in different parts of the U.S and the world. What is more worrying is that Levels in these areas are lower than those observed in the studies done in Kenya, however concentrations and combinations of the different pollutants differ. Studies show that inhaling PM of 10 mm or less over time causes premature death, aggravation of respiratory and cardiovascular diseases and negative lung effects. (Odhiam, Kinyua, Gatebe, & Awange, 2010).

“Fine particulate matter (PM(2.5)), generated by fuel combustion (e.g., in motor vehicles) has been linked to a wide range of health effects, including more than 800,000 deaths in cities around the world” (Kinney et al., 2011).

Continuous exposure to motor vehicle related pollutants leads to symptoms such as wheezing, coughing, shortness of breath and sore throats. irritation of already existing respiratory conditions such as asthma are also a common health effects of exposure to these pollutants and affect mainly young children and the elderly. PM(2.5) has been shown to lead to increases post neonatal infant mortality and early deaths from heart and lung diseases. Results from a study in US found that “with each 10-μg/m3 increase in PM(2.5), the relative risk of mortality from cardiopulmonary diseases was increased by 28%" (Kinney et al., 2011).

Unfortunately those living and working in these areas, pedestrians, informal businesses (street vendors), police officers and road travelers are at high risks of exposure. Walking is the most popular mode of transport among Kenyan’s with close to 50% travelling to their destination by foot, meaning a high percentage of our citizens could be exposing themselves to pollution daily (Vliet & Kinney, 2007).

Black carbon, which forms part of PM, has been identified as the second most important climate pollutant and is directly linked to localized temperature increases. It also contributes to low visibility which could be fatal for road users. This coupled with its numerous health effects as shown above, make it a potent pollutant. However, its life span in the atmosphere is only a few days, unlike CO2, meaning reduction in BC could have immediate health and climate benefits (US-EPA; Akumu, 2013).

Due to the high levels of PM, more particularly PM(2.5), mentioned in previous studies done in Nairobi, more effort need to be placed on reducing there pollutants. In order to understand the real dangers of these pollutants, more localized studies are needed in order to monitor pollution levels in our cities and measure health effects.

Conclusion

The Climate and Clean Air Coalition, a group of various countries and the UNEP, has initiated a program to tackle vehicle pollution in developing countries. Kenya, as a member of East Africa is actively involved in this program and is currently working on modalities to combat air pollution and deal with GHG by increasing Kenya’s fuel quality. Some of the major steps recommended include;

● Promoting better motor vehicle maintenance,

● Tougher regulations and frequent motor vehicle inspections.

● Cleaner fuel – Low sulfur diesel,

● Establishing Strict vehicle emission standards,

● Incentivizing the cleanup of vehicle fleets and uptake of clean technology (Odhiambo et al., 2010; P. L. Kinney et al., 2011; Akumu, 2013; Kaigwara, 2013).

East Africa, including Kenya has made significant strides; East Africa has committed to move to 50 ppm diesel and 150 ppm petrol by Jan 2015. There has also been slight progress in Kenya, although not as impressive as its neighbors, in reducing sulphur in diesel, a major contributor to air pollution (See map below) (Akumu, 2013).

Source: UNEP.

Earlier this year, the National Environment Management Authority (NEMA), announced it was in the process of drafting a bill that will regulate air pollutants and punish those found exceeding set limits. This will be done in an effort to reduce negative health effects resulting in emissions (Aduo, 2014). Kenya’s Environment Cabinet Secretary Judy Wahungu has also announced a raft of measures the government will put in place to deal with air pollution. These include; stiffer penalties and standards, stricter enforcement of imported vehicles age limit, stricter enforcement of industrial pollution limits and acquisition of kits to measure air quality (Nation Media, 2014). Despite these noble steps, there lacks adequate data to properly measure and monitor pollution levels, "no studies have yet been reported that comprehensively assess the full range of important PM sources, and there is little or no descriptive data on patterns of PM(2.5) mass concentrations across time and space" (Vliet & Kinney, 2007). The newly acquired kits, partnerships between educational institutions, government and related stakeholders, is vital in making sure accurate and adequate data is collected.

These steps will go a long way in dealing with the high level of air pollution we experience in Nairobi, but greater public awareness is also needed to educate vehicle users and pedestrians in general of the dangers air pollution poses and what role they can play in eliminating these pollutants. Public participation will also be necessary to hold all institutions responsible accountable, especially the newly formed county governments, whose mandate is enforcing environmental protection laws. For us at ACX, this paper is the first step in educating the public and creating awareness. We hope that by working together, PM levels, GHG emission and any other air pollutants will be greatly reduced and the lives of future generations, secured.

References

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Seinfeld, H.J., 1989. Air Pollution, Physical and Chemical Fundamentals. McGraw-Hill, New York.

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Aduo, P. (2014). Nairobi’s polluted air doles out constant flu. Standard Digital News. Retrieved September 22, 2014, from http://www.standardmedia.co.ke/lifestyle/article/2000126679/nairobi-s-polluted-air-doles-out-constant-flu?pageNo=2

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Nation Media. (2014). Motorists polluting city put on notice. Daily Nation. Retrieved May 14, 2014, from http://www.nation.co.ke/news/Motorists-polluting-city-put-on-notice/-/1056/2313854/-/ft47asz/-/index.html

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USA EPA. (2013). Basic Information | Particulate Matter | Air & Radiation | US EPA. Retrieved March 10, 2014, from http://www.epa.gov/pm/basic.html

Vliet, E. Van, & Kinney, P. (2007). Impacts of roadway emissions on urban particulate matter concentrations in sub-Saharan Africa: new evidence from Nairobi, Kenya. Environmental Research Letters, 2. doi:10.1088/1748-9326/2/4/045028

***Cover Image courtesy of Mutua Matheka

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