Every morning, Hillary Kamau boards a bus from Juja to the city centre. Through many years of experience, Hillary knows the fumes emanating from the passenger service vehicles on Thika Road are not good for his health.
But like many city residents, he is stuck with it. Once in while he will sneeze when the fumes really get bad.
In Ngara, he encounters a permanently clogged entry into the city. Here, the traffic flow comes to a halt unless mercifully, a policeman is on hand and actually controlling traffic.
The collective exhaust emissions from PSVs, trucks and diesel-powered SUVs and other vehicles are enough to bring on a day-long headache.
Like many Nairobi residents, Hillary has to breathe in air that is mixed with the exhaust fumes of over 300,000 cars daily. Nairobi has one of the worst vehicle fleets going by the emissions, and this is slowly killing its residents.
But many have no idea.
“We just have to survive,” says Hillary.
The air in different parts in Nairobi increases the risk of heart and respiratory conditions, and lowers resistance to colds and flus.
Once in a while, Hillary experiences headaches and bouts of coughing, which he dismisses as common challenges every Nairobian goes through.
Little does he know that such exposure could also harm the brain, increasing the risk of Alzheimer’s disease and other forms of dementia.
Back home in Githurai, his 72-year-old mother, Veronica Nyatika, is suffering from Alzheimer's.
She was diagnosed with the disease in 2014, following a spate of memory loss incidents.
“She would call us, her children, and ask us to send money, and we would. But then a few days later, she would call and ask for the same money,” Hillary says.
It would have been easy for the family to brush off these memory lapses and nonchalantly tie them to old age.
But they were forced to take Veronica to hospital when, one Sunday after church, she took the wrong turn going back home and couldn't figure out how to find her way.
“We just know that she is sick. We have never been told how the sickness came by,” says Hillary.
It could be anything, really. But it could also be that Veronica’s woes stem from the dirty air she has been breathing in Nairobi and other urban centres.
“She has lived in urban environments since 1965. She has been in Naivasha, Eldoret, Gilgil, Nakuru and Nairobi,” Hillary says.
In 2015, the United Nations Environmental Programme (Unep) conducted air pollution tests in different parts of Nairobi and found some areas worse than others.
The most polluted neighbourhoods in Nairobi are Hazina in South B, Donholm, Kariakor and Baba Dogo estates along Jogoo and Landhies roads, all of which suffer from relatively bad traffic congestion.
Florence Mwenda’s 74-year-old husband Mike was diagnosed with Alzheimer’s in 2012.
“He has lived nearly his entire life close to busy roads in the city,” says Florence. “He worked for the Government in Nakuru, then for Kenya Meat Commission in Athi River, then at a factory along Jogoo Road, then at a petrol station in Dagoretti Corner, then at an establishment along Ngong Road.”
That Mike spent a lot of his life living in towns no doubt exposed him to more air pollution – from vehicle exhaust fumes to industry emissions.
The disease, Florence says, caused him become easily irritable. He would also ask for his toothbrush while holding it in his hand.
“I took him to hospital because his forgetfulness was getting worse,” Florence says. “We would go to a place and he wouldn’t know how to drive back home; we would have to ask someone to drive ahead of us so my husband could follow them.”
Although Mike’s diagnosis was made in 2012, Florence believes her husband’s forgetfulness – his decision-making skills had also become wanting – began earlier.
Maurice Raute, a medical doctor who has studied poisons, says the high presence of heavy metals in polluted air should worry public health officials.
“Prime among these heavy metals is lead – which is present in some fuels. Lead damages the brain and the central nervous system,” Dr Raute added.
Unlike in the countryside, he said, cities like Nairobi don’t have as much vegetation to help purify the air.
“Those who have lived in Nairobi for a long time have more toxins in their body than those who have lived in rural areas,” he says.
The result of too much air pollution in the city, he said, has been an influx in cancer cases.
“These diseases can first be traced to genetics, then lifestyle and the environment.”
Marie Thynell is a researcher at Sweden’s Gothenburg University. In 2015, she led a study of Nairobi pollution.
“The air pollution within the city is 10 times higher than the threshold recommended by the World Health Organisation,” she told the UK’s Guardian newspaper in 2016.
Risk of dementia
Another study, in September 2016, by researchers at Lancaster University in the UK found that some particles found in polluted air find their way to the human brain once ingested through breathing.
And a Canadian study published in The Lancet early in 2017 found that people who live within 200 metres of a busy road have an elevated risk of suffering dementia.
The level of risk increases proportionally with a 2 per cent, a 4 per cent and a seven per cent greater risk among people living 101 to 200 metres, 50 to 100 metres and 50 metres or less, respectively, away from a busy road.
Ray Copes, the chief of environmental and occupational health at Public Health Ontario, who co-led the Canadian study, observed that beyond 200 metres, the risk was insignificant.
Copes and his team tracked adults between 20 and 85 years old living in Ontario for 10 years - between 2002 and 2012 - to arrive at their conclusions.
Currently, there are more than 47 million dementia patients worldwide. The World Health Organisation estimates that 7.7 million new cases occur each year.