Silent killer: Kenyans struggle with daily dose of toxic air

A herd of cattle feeding besides a burning pile of garbage at Mukuru Kayaba slums, Nairobi.


What you need to know:

  • Her doctor prescribed an inhaler and advised her to either relocate her business or cease operations altogether to preserve her health.
  • She ultimately chose to close her shop and transitioned to working full-time as a health promoter.

Imagine this: You step outside your house, ready to start the day. But instead of the crisp morning air you crave, you are greeted by a thick, acrid mix of exhaust fumes and smoke that sends you into a coughing fit. Annoyance prickles at you – is this the air you must breathe daily?

This experience is all too familiar for Mary Njoki, a resident of Mathare slums. The community health promoter has been tethered to an inhaler for the past five years. "I cannot leave the house without it," she says.

Mary's troubles began when she opened a roadside stall near a matatu drop-off point in Mathare. At the market, proper waste disposal and burning were non-existent, adding to the noxious air. Daily, she inhaled a toxic cocktail of dust and vehicle exhaust.

A new report jointly launched by the United Nations Environment Programme (Unep) and the Climate and Clean Air Coalition (CCAC) shows that heavy-duty vehicles (HDVs) such as trucks and buses are heavy emitters. Kenya is the second largest exporter of HDVs in East Africa after Burundi.

"If you have ever walked behind a big heavy truck, you may have smelled the nasty fumes billowing from its exhaust. Now, imagine standing next to such fumes all day?" She sighs. "I remember that the issue of polluted air was a constant conversation among us roadside sellers, and we wondered how long we would breathe the polluted air. I didn't know it would scar me for life," she says.

WHO estimates that seven million people die prematurely yearly due to air pollution, with half of this due to outdoor air pollution.

Her health issues began with a persistent cough and chest pains. Despite multiple trips to the hospital and treatment for recurring respiratory infections, the 62-year-old was ultimately diagnosed with asthma, a lung condition that makes breathing more difficult. Her doctor prescribed an inhaler and advised her to either relocate her business or cease operations altogether to preserve her health. She ultimately chose to close her shop and transitioned to working full-time as a health promoter.

Back home, the situation was the same. The smoke from her charcoal stove, a common feature in many Kenyan households, stung her eyes and irritated her throat. Lower-income groups in Nairobi's informal settlements like Mathare, where Mary lives, heavily rely on solid fuels like charcoal, classified as dirty fuels that release pollutants like smoke and dust when burnt.

"After many months of saving, I switched to cooking with gas, and I advocate for the same to the residents here," she says. Mary and other women under Groots Kenya work to raise awareness about cleaner cooking alternatives and reduce air pollution in the slums.

Yet, Mary's story isn't unique. Across Kenya, various towns are grappling with their own air pollution cocktails. Multiple studies reveal a rapid decline in outdoor air quality, raising health concerns.

Recently, IQAir released 2023's World Air Quality Report, finding that millions of people live with and breathe polluted air. The report ranks 134 countries across 7,748 locations using data from over 30,000 air quality monitoring stations around the globe. WHO estimates that seven million people die prematurely yearly due to air pollution, with half of this due to outdoor air pollution.

The Air Quality Index (AQI) measures air pollution to understand its severity. This index considers various pollutant concentrations and assigns a numerical value. Higher AQIs indicate greater air pollution and potential health risks.

The World Health Organization (WHO) identifies PM2.5 fine particulate matter as the most hazardous pollutant as it gets deep into our lungs and causes health problems. Measured in micrograms per cubic metre (μg/m³), PM2.5 is one of the six common pollutants monitored and regulated by environmental agencies worldwide due to the significant impacts on human health and the environment. Other pollutants include ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide and lead). According to WHO, air is healthiest when these particles are below 5 µg/m3. That's like saying there should be less than five tiny specks in every breath of air you take throughout the year.

Moses Njeru, an air quality researcher at the University of Nairobi, terms air pollution as a lurking danger. Vehicle emissions, industrial facilities, burning waste and dust storms contribute to this toxic mix.

"PM2.5 fine particulate matter are particles a fraction the size of human hair that can be inhaled and often find their way into the deep lungs and even the bloodstream. Studies have shown links to strokes, heart diseases, neurological diseases, chronic obstructive pulmonary disease (COPD), lung cancer and other health-related conditions," he offers.

The pollutants, he says, can come from various sources, including vehicle emissions, industrial facilities, burning waste, and dust storms.

PM2.5 particles, caused mainly by fossil fuel emissions, affect human health and environmental processes like climate change. Only 10 of 134 countries met WHO's annual PM2.5 guidelines in 2023.

IQAir ranked Nairobi as the 79th most polluted city globally. Bangladesh is the world's most polluted country, while Burkina Faso is the most polluted in Africa. The report is based on data from 24 out of 54 Sub-Saharan African countries, indicating the need for more comprehensive air quality insights.

"Five cities in Kenya met the criteria for inclusion in the 2023 World Air Quality Report. "Data shows improved PM2.5 levels in Nakuru, Kapsabet and Nairobi over the past year. This year marks the fourth consecutive year for PM2.5 improvements in the capital city of Nairobi, which boasts the second-largest network coverage of air quality monitors among African cities," says Dr Christi Chester-Schroeder, an air quality science manager.

Here is the not-so-good news: only about nine per cent of cities worldwide have clean air. IQAir found that the cities with the worst air were New Delhi, Dhaka, Ouagadougou, Dushanbe, and Baghdad. Capitals with the lowest concentrations of PM2.5 were mainly in Oceania, Scandinavia and the Caribbean.

A trailer along Mombasa Road emitting exhaust fumes


A recent Clean Air Fund report warns that without crucial urban development interventions, the economic cost of air pollution in six rapidly growing cities, including Nairobi, could reach a staggering Sh19 trillion by 2040.

Mr Njeru and his team from the University of Nairobi have deployed air quality monitors across Kenya to verify air quality data. "Given the diverse micro-environments, we need comprehensive data," he explains. Monitors are placed in residential areas, suburbs, industrial zones, forested areas, and the central business district (CBD) to capture pollution variations.

The verdict: Kenyans are breathing unsafe air. Research reveals "hotspots"—areas with elevated PM2.5 pollution, particularly in high-traffic zones, informal settlements and industrial regions. The CBD experiences spikes during rush hour. "Our research, in particular, shows the guidelines have exceeded even three times in some areas," he says.

While PM2.5 poses direct health risks, Moses says its implications extend beyond human health to climate change, which is primarily driven by greenhouse gas emissions.

"For centuries, air pollution has been a silent killer. It was not until the Great London Smog of the 1950s that enough noise was made after thousands of people died prematurely in Europe. This led to a call for regulation and the birth of the famous Clean Air Act, whose mission was to control common pollutants," says the researcher.